0000950170-24-029191 | 10-K | XBRL Viewer

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Net Loss Per Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	21,301,228	15,493,787
Common stock warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	5,675,167	0
RSU's
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	1,820,589	1,201,058
Options and ESPP to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	13,805,472	14,292,729

Income Taxes - Schedule of Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current:
Federal	$ 0	$ 0
State	3,892	0
Total current	3,892	0
Deferred:
Federal	0	0
State	0	0
Total deferred	0	0
Provision for income taxes	$ 3,892	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

STATEMENTS OF STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income/(Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ (459)	$ 1	$ 623,344	$ (242)	$ (623,562)
Beginning balance, shares at Dec. 31, 2021		65,392,758
Exercise of stock options and release of RSUs	99		99
Exercise of stock options and release of RSUs, shares		430,096
Issuance of common stock under the Employee Stock Purchase Plan	$ 549		549
Issuance of common stock under the Employee Stock Purchase Plan, shares	405,192	405,192
Stock-based compensation	$ 13,125		13,125
Other comprehensive income	252			252
Net loss	(99,317)				(99,317)
Ending balance at Dec. 31, 2022	$ (85,751)	$ 1	637,117	10	(722,879)
Ending balance, shares at Dec. 31, 2022		66,228,046
Exercise of stock options, shares	16,535
Exercise of stock options and release of RSUs	$ 26		26
Exercise of stock options and release of RSUs, shares		675,864
Issuance of common stock under the Employee Stock Purchase Plan	535		535
Issuance of pre-funded warrants and warrants, net of issuance cost	$ 29,669		29,669
Issuance of common stock under the Employee Stock Purchase Plan, shares	406,928	406,928
Stock-based compensation	$ 8,558		8,558
Other comprehensive income	85			85
Net loss	(569)				(569)
Ending balance at Dec. 31, 2023	$ (47,447)	$ 1	$ 675,905	$ 95	$ (723,448)
Ending balance, shares at Dec. 31, 2023		67,310,838

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaboration and License Agreements

8. Collaboration and License Agreements

The following table summarizes the revenue by collaboration partner:


	Year Ended December 31,
	2023		2022
	(in thousands)
AbbVie	$	3,688	$	18,563
Amgen		5,739		4,967
Astellas		24,453		20,491
Bristol Myers Squibb		49,300		9,142
Regeneron		7,194		—
Moderna		10,840		—
Total revenue	$	101,214	$	53,163

AbbVie Ireland Unlimited Company

In April 2016, the Company and AbbVie entered into two agreements, a CD71 Co-Development and Licensing Agreement (the “CD71 Agreement”) and a Discovery Collaboration and Licensing Agreement (as amended and restated in June 2019, the “Discovery Agreement” and together with the CD71 Agreement the “AbbVie Agreements”). Under the terms of the CD71 Agreement, the Company and AbbVie were co-developing a conditionally activated antibody-drug conjugate (“ADC”), CX-2029, against CD71, with the Company being responsible for preclinical and early clinical development. AbbVie was to be responsible for later development and commercialization, with global late-stage development costs shared between the two companies. The Company was to assume 35% of the net profits or net losses related to later development and commercialization unless it opted-out. Under the Agreement, if the Company was to opt-out from participation of co-development of the CD71 conditionally activated ADC, which included CX-2029, AbbVie would have had the sole right and responsibility for the further development, manufacturing and commercialization of such CD71 conditionally activated ADC.

Under the CD71 Agreement, the Company has received in aggregate $100.0 million in upfront and milestone payments. AbbVie had entered into a license agreement with SGEN to license certain intellectual property rights pursuant to which the Company was required to pay SGEN sublicense fees for certain milestone achievements and an annual maintenance fee. These sublicense fees were treated as reductions to the transaction price and combined with the performance obligation to which they relate.

In March 2023, the Company announced that it would evaluate the potential next steps for CX-2029 following the decision from AbbVie, to not advance CX-2029 into additional clinical studies. As a result of AbbVie’s decision, the 2016 CD71 License and Collaboration Agreement has been terminated and the Company re-acquired full rights to CX-2029. The Company has completed the performance obligation under the CD71 Agreement as of March 31, 2023 and recognized the related remaining deferred revenue of $4.0 million in the first quarter of 2023.

Under the terms of the Discovery Agreement, AbbVie received exclusive worldwide rights to develop and commercialize conditionally activated ADCs against up to two targets, one of which was selected in March 2017. AbbVie had the option to select a second target in exchange for a $10.0 million payment. The Company concluded that, at the inception of the agreement, AbbVie’s option to select the additional target was not a material right and did not represent a performance obligation of the agreement and would be accounted for as a separate arrangement upon exercise. The Company shall perform research services to discover the PROBODY therapeutics and create conditionally activated ADCs for the nominated collaboration targets. From that point, AbbVie shall have sole right and responsibility for development and commercialization of products comprising or containing such conditionally activated ADCs (“Discovery Licensed Products”).

Under the Discovery Agreement, the Company received an upfront payment of $10.0 million for the first target in April 2016 and subsequently received an additional $10.0 million payment triggered by selection of the second target by AbbVie in June 2019. The second target was selected under the Discovery Agreement that allowed AbbVie to select a target for developing a conditionally activated ADC or a PROBODY antibody. In December 2022, the Company completed the performance obligation for the second target earlier than the original research term projected to end in 2024 and recorded a cumulative change in estimate of $4.4 million. In December 2022, the research on the two discovery targets under the Discovery Agreement concluded with no plans to advance the discovery targets into clinical studies or to pursue new programs. The Discovery Agreement was also terminated in March 2023 by AbbVie and all target rights have reverted back to CytomX.

The Company determined that the AbbVie Agreements should be combined and evaluated as a single arrangement in determining revenue recognition, because both agreements were concurrently negotiated and executed. Therefore, the Company concluded that there were two distinct performance obligations:

(1)

the CD71 Agreement performance obligation consisting of the CD71 Agreement research, development and commercialization license, related research services and participation in the joint research committee, and

(2)

the Discovery Agreement performance obligation consisting of the Discovery Agreement research, development and commercialization license, related research services and participation in the joint research committee.

The total transaction price for the Discovery Agreement and CD71 Agreement, collectively, upon adoption of ASC 606 on January 1, 2018 of $39.8 million consisted of $30.0 million in upfront payments, and a $14.0 million milestone payment received under the CD71 Agreement (net of the payment of an associated sublicense fee of $1.0 million to SGEN), less $4.2 million of estimated sublicense fees. The upfront payments under the AbbVie Agreements were allocated between the two performance obligations based on the estimated relative standalone selling prices. The $30.0 million of upfront payments was allocated $20.0 million to the CD71 Agreement, with the remaining $10.0 million allocated to the Discovery Agreement. The $14.0 million milestone payment received (net of the payment of an associated sublicense fee of $1.0 million to SGEN) and the estimated sublicense fees of $4.2 million were allocated to the CD71 Agreement performance obligation as they are directly related to the development of the CX-2029.

Therefore, of the $39.8 million total initial transaction price discussed above, the Company allocated $29.8 million to the CD71 Agreement performance obligation and $10.0 million to the Discovery Agreement performance obligation and recognized revenue using an input measure for each performance obligation. In applying the input method, revenue is recognized based on actual full time employee ("FTE") hours incurred as a percentage of total estimated FTE hours for completing the combined performance obligation over the estimated service period. The Company evaluated the measure of progress each reporting period and, if necessary, adjusted the measure of performance and related revenue recognition.

The Company updated the transaction price for the CD71 Agreement performance obligation in May 2018, to include achievement of the $21.0 million milestone (net of the payment of an associated sublicense fee of $4.0 million to SGEN) and a revenue adjustment of $9.9 million was recognized in the second quarter of 2018 reflecting the percentage completed to-date on the project related to this milestone. The transaction price was updated again in March 2020 upon achievement of the $40.0 million milestone related to satisfaction of the CD71 dose escalation success criteria and $26.6 million was recognized as revenue related to this milestone reflecting the percentage completed to-date on the project as of March 2020.

As of December 31, 2023 and 2022, deferred revenue related to the CD71 Agreement performance obligation was zero and $4.0 million respectively, and there were no deferred revenues related to the Discovery Agreement performance obligation, respectively.

Amgen, Inc.

On September 29, 2017, the Company and Amgen, Inc. (“Amgen”) entered into a Collaboration and License Agreement (the “Amgen Agreement”). Pursuant to the Amgen Agreement, the Company received an upfront payment of $40.0 million in October 2017. Concurrent with the Amgen Agreement, the Company and Amgen entered into a Share Purchase Agreement pursuant to which Amgen purchased 1,156,069 shares of the Company’s common stock at a price of $17.30 per share for total proceeds of $20.0 million.

In October 2021, CytomX and Amgen executed an amendment to the Amgen Agreement primarily to (1) extend the target selection date for Amgen to select its additional targets for research and development, and (2) reduce the total number of milestone events and increase the total amount of milestone payments for EGFR Products. In May 2023, CytomX and Amgen executed an amendment to the Amgen Agreement to extend the target selection period for Amgen to select its additional targets for research and development as further discussed below.

Under the terms of the Amgen Agreement, as amended, the Company and Amgen will co-develop a conditionally activated T-cell engaging bispecific therapeutic targeting epidermal growth factor receptor (the “EGFR Products”). The Company is responsible for early-stage development of EGFR Products and Amgen will be responsible for late-stage development and commercialization of EGFR Products. Following early-stage development, the Company will have the right to elect to participate financially in the global co-development of EGFR Products with Amgen, during which the Company would bear a certain percentage of the worldwide development costs for EGFR Products and Amgen would bear the rest of such costs (the “EGFR Co-Development Option”). If the Company exercises its EGFR Co-Development Option, the Company will share in somewhat less than 50% of the profit and losses from sales of such EGFR Products in the U.S., subject to certain caps, offsets, and deferrals. If the Company chooses not to exercise its EGFR Co-Development Option, the Company will not bear any costs of later stage development. The Company is also eligible to receive up to $460.0 million in development, regulatory, and commercial milestone payments for EGFR Products, and royalties in the low-double-digit to mid-teen percentage of worldwide commercial sales, provided that if the Company exercises its EGFR Co-Development option, it shall receive a profit and loss split of sales in the United States and royalties in the low-double-digit to mid-teen percentage of commercial sales outside of the United States. In January 2022, the IND for the EGFR product (CX-904) was allowed to proceed by the U.S. Food and Drug Administration (“FDA”).

Amgen also has the right to select a total of up to three targets, including the two additional targets discussed below. The Company and Amgen collaborate in the research and development of conditionally activated T-cell engaging bispecifics therapies directed against such targets. Amgen has selected one such target (the “Amgen Other Product”). If Amgen exercises its option within a specified period of time, it can select two such additional targets (the “Amgen Option Products” and, together with the Amgen Other Product, the “Amgen Products”). Except with respect to preclinical activities to be conducted by CytomX, Amgen will be responsible, at its expense, for the development, manufacture, and commercialization of all Amgen Products. If Amgen exercises all of its options and advances all three of the Amgen Products, CytomX is eligible to receive up to $950.0 million in upfront, development, regulatory, and commercial milestones and tiered high single-digit to low-teen percentage royalties. The Company concluded that, at the inception of the agreement and subsequent amendments, Amgen’s option to select the two additional targets is not a material right and does not represent a performance obligation of the agreement.

At the initiation of the collaboration, CytomX had the option to select from programs specified in the Amgen Agreement, an existing preclinical stage T-cell engaging bispecific product from the Amgen preclinical pipeline. In March 2018, CytomX selected the program and this program is currently in preclinical development. CytomX is responsible, at its expense, for converting this program to a conditionally activated T-cell engaging bispecific product, and thereafter, will be responsible for development, manufacturing, and commercialization of the product (“CytomX Product”). Amgen is eligible to receive up to $203.0 million in development, regulatory, and commercial milestone payments for the CytomX Product, and tiered mid-single digit to low double-digit percentage royalties.

The Company considered the criteria for combining contracts in ASC 606 and determined that the Amgen Agreement and the Purchase Agreement should be combined into one contract. The Company accounted for the Amgen Agreement based on the fair values of the assets and services exchanged.

For each of the EGFR Products and the Amgen Other Products, the Company determined that the respective promised goods and services identified, which are the research, development and commercialization license; the related research and development services and the participation in the joint steering committee and joint research committee, are not distinct. Therefore the identified promised goods and services were combined into one single performance obligation for each of the EGFR Product and the Amgen Other Products.

Furthermore, the Amgen Other Products are accounted for as a separate performance obligation from the EGFR Products as the nature of the services being performed is not the same and the value that Amgen can derive from one program is not dependent on the success of the other. The Company evaluates the measure of progress each reporting period using the input method and, if necessary, adjusts the measure of performance and related revenue recognition.

Concurrent with the execution of the Amgen Agreement, the Company entered into a sublicense agreement whereby the Company granted Amgen a sublicense of its rights to one patent family that it co-owns with UCSB, that is exclusively licensed to the Company under the UCSB Agreement covering PROBODY antibodies and other pro-proteins in the fields of therapeutics, in vivo diagnostics and prophylactics. This sublicense was incremental to the patents, patent applications and know-how covering conditionally activated T-cell engaging bispecific molecules that were developed and owned by the Company and licensed to Amgen. Under the UCSB Agreement, as amended, the Company is obligated to make a sublicense payment to UCSB equal to up to 7.5% of certain upfront and milestone payments owed to or received by the Company.

The total transaction price of $51.2 million, consisting of the $40.0 million upfront payment, an estimated fair value of $10.7 million for the CytomX Product and $0.5 million of premium on the sale of the Company’s common stock, was allocated between the two performance obligations based on the relative standalone selling price of each performance obligation. To determine the standalone selling price, the Company used the discounted cash flow method by calculating risk-adjusted net present values of estimated cash flows. The Company determined that the remaining potential milestone payments were fully constrained due to the uncertainty in achieving them as of December 31, 2023.

Of the $51.2 million total transaction price, the Company allocated $46.4 million to the EGFR Products performance obligation and $4.8 million to the Amgen Other Product performance obligations. The transaction price of each performance obligation was recognized using an input measure. In applying the input method of revenue recognition, the Company uses actual FTE hours incurred relative to estimated total FTE hours expected to be incurred for each combined performance obligation over the research service period. At the end of the second quarter of 2019, the Company determined that it would undertake additional testing and assessment of the molecules being evaluated under the EGFR project. As a result, the estimated FTE hours-to-completion and research service period related to the EGFR project were increased to eight years. In the second quarter of 2020, the Company completed the clinical candidate characterization phase and moved into the IND-enabling phase earlier than planned. As a result, the estimated FTE hours-to-completion and research service period related to the EGFR project were decreased from eight to approximately seven years. In the third quarter of 2022, the FDA initiated Project Optimus which is aimed to reform the dose optimization and dose selection paradigm. As a result, the estimated FTE hours-to-completion and research service period were increased by approximately an additional year.

The $4.8 million transaction price allocated to the Amgen Other Product performance obligation is recognized using estimated FTE hours-to-completion over the estimated research service period of six years.

As of December 31, 2023 and 2022 deferred revenue related to the EGFR Products performance obligation was $12.8 million and $18.0 million, respectively. As of December 31, 2023 and 2022, deferred revenue related to the Amgen Other Products performance obligation was zero and $0.6 million, respectively.

Astellas Pharma Inc.

The Company and Astellas Pharma, Inc. (“Astellas”) entered into a Collaboration and License Agreement (the “Astellas Agreement”) on March 23, 2020, the effective date, to collaborate on preclinical research activities to discover and develop certain antibody compounds for the treatment of cancer using the Company’s PROBODY therapeutic technology.

Under the terms of the Astellas Agreement, the Company granted Astellas an exclusive, worldwide right to develop and commercialize PROBODY therapeutics for up to four collaboration targets including one initial target and three additional targets (“Additional Targets”). In addition, Astellas had the right to expand the number of Additional Targets from three up to five (the “Expansion Option”) before the third anniversary of the effective date. Furthermore, for a specified number of targets, at a pre-specified time prior to the initiation of the first pivotal study of a product against such target, the Company may elect to participate in certain development costs and share in the profits generated in the United States with respect to such product (“Cost Share Option”). The Cost Share Option, if exercised, will also provide the option for the Company to co-commercialize such product in the United States. The Company does not consider the Cost Share Option as a performance obligation at the inception of the agreement as participation is at the Company’s discretion.

Pursuant to the Astellas Agreement, the consideration from Astellas is comprised of an upfront fee of $80.0 million and contingent payments for development, regulatory and sales milestones of up to an aggregate of approximately $1.6 billion. The Company is also

entitled to tiered royalties from high-single digit to mid-teen percentage royalties from potential future sales. Astellas is responsible for all preclinical research costs incurred by either party as set forth in the preclinical research plan and the Company will receive research and development service fees based on a prescribed FTE rate.

The Company determined that the license and expertise related to the development of product candidates should be combined with the research and development services and participation in the joint research committee as one combined performance obligation for each collaboration target. The Company concluded, that at the inception of the agreement, Astellas’ Expansion Option for Additional Targets were not material rights and therefore not considered performance obligations. As such, each option would have been accounted for as a separate arrangement upon exercise.

The initial transaction price of $103.2 million consists of the upfront fee of $80.0 million and estimated research and development fees of $23.2 million. The transaction price was allocated between the four performance obligations based on the relative standalone selling price of each performance obligation, which was deemed to be equal at the inception of the agreement. The Company determined that all potential milestone payments are constrained as of December 31, 2023 due to the significant uncertainty of achievement.

The transaction price, as allocated to the combined performance obligation for each target, is recognized using an input measure. In applying the input method of revenue recognition, the Company uses actual FTE hours incurred relative to estimated total FTE hours expected to be incurred over the estimated research service period of each target.

In January 2023, the Company announced that it achieved a clinical candidate milestone under the Astellas Agreement which triggered a $5.0 million milestone payment to the Company. The $5.0 million milestone payment was fully recognized in the first quarter of 2023 as the Company had completed its related performance obligation of the collaboration target which resulted in the clinical candidate nomination for further development.

As of December 31, 2023 and 2022, deferred revenue relating to the Astellas Agreement was $31.0 million and $44.5 million, respectively. The amount due from Astellas under the Astellas Agreement was $2.2 million and $1.0 million as of December 31, 2023 and 2022, respectively.

Bristol Myers Squibb Company

On May 23, 2014, the Company and Bristol Myers Squibb Company (“Bristol Myers Squibb”) entered into a Collaboration and License Agreement (the “BMS Agreement”) to discover and develop compounds for use in human therapeutics aimed at multiple immuno-oncology targets using the Company’s PROBODY therapeutic technology. The effective date of the BMS Agreement was July 7, 2014.

Under the terms of the BMS Agreement, the Company granted Bristol Myers Squibb exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to four oncology targets. Bristol Myers Squibb had additional rights to substitute up to two collaboration targets within three years of the effective date of the BMS Agreement. These rights expired in May 2017. Each collaboration target had a two-year research term and the two additional targets had to be nominated by Bristol Myers Squibb within five years of the effective date of the BMS Agreement. The research term for each collaboration target could be extended in one year increments up to three times.

Pursuant to the BMS Agreement, the financial consideration from Bristol Myers Squibb was comprised of an upfront payment of $50.0 million and estimated research and development service fees, and the Company was initially entitled to receive contingent payments of up to $25.0 million for additional targets and contingent payments for development, regulatory and sales milestones. In addition, the Company was entitled to royalty payments in the mid-single digits to low double-digit percentages from potential future sales.

On March 17, 2017, the Company and Bristol Myers Squibb amended the BMS agreement and entered into Amendment Number 1 to Extend Collaboration and License Agreement (“Amendment 1”). Amendment 1 granted Bristol Myers Squibb exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to eight additional targets. The effective date of Amendment 1 was April 25, 2017 (“Amendment Effective Date”). Under the terms of Amendment 1, the Company continued to have obligations to Bristol Myers Squibb to discover and conduct preclinical development of PROBODY therapeutics against any targets they chose to select during the research period under the terms of Amendment 1.

Pursuant to Amendment 1, the financial consideration from Bristol Myers Squibb was comprised of an upfront payment of $200.0 million, estimated research and development service fees, and contingent payments for development, regulatory and sales milestones

for the eight targets. The Company was also entitled to tiered mid-single to low double-digit percentage royalties from potential future sales. Amendment 1 did not change the term of Bristol Myers Squibb’s royalty obligation under the BMS Agreement. Bristol Myers Squibb’s royalty obligation continues on a licensed-product by licensed-product basis until the later of (i) the expiration of the last claim of the licensed patents covering the licensed products in the country, (ii) the twelfth anniversary of the first commercial sale of a licensed product in a country, or (iii) the expiration of any applicable regulatory, pediatric, orphan drug or data exclusivity with respect to such product.

The Company elected the practical expedient related to contract modifications upon adoption of ASC 606 and combined the original agreement and Amendment 1. The Company determined that the identified promised goods and services which include the exclusive research, development and commercialization license, the related research services and expertise for the development of the product candidates should be combined with the participation in the joint research committee as one combined performance obligation for each collaboration target. The Company also concluded that, at the inception of the agreement, Bristol Myers Squibb’s options for the third and fourth targets were material rights and performance obligations. As such, the material rights were accounted for as part of the initial transaction price.

The Company received an upfront payment of $50.0 million from Bristol Myers Squibb in July 2014. In January and December 2016, Bristol Myers Squibb exercised the option to select the third and fourth targets, and paid the Company $10.0 million and $15.0 million, respectively, pursuant to the terms of the BMS Agreement. In December 2016, Bristol Myers Squibb selected a clinical candidate pursuant to the BMS Agreement, which triggered a $2.0 million pre-clinical milestone payment to the Company. In November 2017, the Company recognized a $10.0 million milestone payment from Bristol Myers Squibb upon approval of the investigational new drug application for the CTLA-4-directed PROBODY therapeutic.

The initial transaction price for the BMS Agreement and Amendment 1, collectively, was $304.7 million consisting of the upfront fees of $250.0 million, target selection fees for the third and fourth targets of $25.0 million, estimated research and development service fees of $17.7 million and milestone payments received up to January 1, 2018, of $12.0 million. The Company determined that the remaining potential milestone payments were probable of significant revenue reversal as their achievement was highly dependent on factors outside the Company’s control. Therefore, these payments were fully constrained and were not included in the transaction price upon the adoption of ASC 606 on January 1, 2018. The initial transaction price for the combined obligation for each collaboration target is recognized using an input measure. In applying the input method of revenue recognition, the Company uses actual FTE hours incurred relative to estimated total FTE hours expected to be incurred for each combined performance obligation over the estimated research service period of each collaboration target.

During the first quarter of 2019, Bristol Myers Squibb terminated pre-clinical activities on three of the first four collaboration targets selected under the original 2014 BMS Agreement. The Company determined that upon the termination of pre-clinical activities on the three collaboration targets, it has no further obligations related to such targets. The Company accounted for the termination of the three targets as a modification and the related remaining unrecognized transaction price was reallocated to the remaining performance obligations. The Company continues to be obligated to perform research work under Amendment 1 executed in March 2017.

In February 2020, Bristol Myers Squibb dosed the first patient in the Part 2 cohort expansion portion of its ongoing BMS-986249 clinical study for the CTLA-4 program, which triggered a $10.0 million milestone payment to the Company pursuant to the terms of the BMS Agreement. The $10.0 million milestone payment was recognized as revenue in the first quarter of 2020 as the Company had completed its performance obligation related to this collaboration target.

In February 2021, the Company and Bristol Myers Squibb amended the BMS agreement and entered into Amendment Number 2 to amend the Collaboration and License Agreement (“Amendment 2”), as previously amended by Amendment 1. Subsequent to Amendment 2, in addition to Bristol Myers Squibb’s ongoing development of the CTLA-4 program, Bristol Myers Squibb also had the exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to five oncology targets. Under the terms of Amendment 2, the period for target selection was extended and in 2022, all remaining targets were selected. The Company will continue to collaborate with Bristol Myers Squibb to discover and conduct preclinical development of PROBODY therapeutics against targets selected by Bristol Myers Squibb over the estimated research period, which is projected to end in April 2025. Pursuant to Amendment 2, the Company was eligible to receive contingent payments for development, regulatory and sales milestones. It is also entitled to tiered mid-single to low double-digit percentage of royalties from potential future sales. The Company accounted for Amendment 2 as a modification and reallocated the remaining unrecognized transaction price to the remaining performance obligations.

In October 2022, the Company and Bristol Myers Squibb amended the BMS Agreement and entered into Amendment Number 3 (“Amendment 3”), as previously amended by Amendment 1 and Amendment 2, to clarify the rights and restrictions of certain new proprietary antibodies that the parties exchanged. There were no substantive changes to each party's performance obligations. As of December 31, 2023, the Company was eligible for up to approximately $2.1 billion in contingent payments for development, regulatory and sales milestones based on the ongoing collaboration projects, including for the CTLA-4 program, with BMS.

On March 6, 2024, following a Bristol Myers Squibb corporate portfolio prioritization process, Bristol Myers Squibb notified CytomX that it does not intend to continue the development of BMS-986288 beyond the current Phase 2 study and terminated its work on the CTLA-4 target under the collaboration. As of March 6, 2024, CytomX is eligible to receive approximately $1.8 billion in contingent payments for development, regulatory and sales milestones for the ongoing collaboration programs.

The Company reevaluated the remaining potential milestone payments and determined that significant revenue reversal was probable as the achievement of such milestones was highly dependent on factors outside the Company’s control. As a result, these payments continued to be fully constrained and were not included in the transaction price on December 31, 2023. As of December 31, 2023, the Company has received in aggregate $297.0 million in upfront and milestone payments under the agreement.

As of December 31, 2023 and 2022, deferred revenue relating to the BMS Agreement was $119.9 million and $169.2 million, respectively.

ModernaTX, Inc.

The Company and ModernaTX, Inc. (“Moderna”) entered into a Collaboration and License Agreement (the “Moderna Agreement”) on December 30, 2022, the effective date, to collaborate on discovery and preclinical research and development activities to create investigational messenger RNA (mRNA) based conditionally activated therapies using the Company’s PROBODY therapeutic technology. Moderna is solely responsible for the development (preclinical and clinical), manufacturing, and commercialization of any products under the Moderna Agreement.

Under the terms of the Moderna Agreement, the Company granted Moderna an exclusive, worldwide right to develop and commercialize PROBODY therapeutics for the collaboration programs. In exchange, the Company received an upfront payment of $35.0 million in January 2023, including $5.0 million of prepaid research and development service fees. The Company will continue to receive research and development service fees according to the preclinical research work plans based on a prescribed FTE rate and is eligible to receive up to approximately $1.2 billion in future development, regulatory, and commercial milestone payments. The Company is also eligible to receive tiered royalties from high-single digit to low-teen percentage rates of annual global net sales of any products that are commercialized under the Moderna Agreement. The Moderna Agreement also provided Moderna with an option to participate in an equity financing by CytomX at market price, subject to certain terms, conditions and regulatory requirements.

The Company determined that each collaboration program was a distinct performance obligation consisting of the exclusive research, development and commercialization license, research services, and participation in the joint steering committee. The initial transaction price is $51.7 million, consisting of the upfront fee of $30.0 million and estimated research funding of $21.7 million from Moderna. The initial transaction price excludes milestone payments as the achievement of such milestones is dependent on factors outside of the Company’s control and recognition would be probable of significant revenue reversal. As such, the milestones are fully constrained at the inception of the contract. The Company will re-evaluate the transaction price at each reporting date or as uncertain events are resolved or other changes in circumstances occur.

The transaction price at the contract inception was allocated among the performance obligations using the SSP of each performance obligation, which was determined to be equal due to the early stage of the collaboration programs. The transaction price allocated to the collaboration programs is recognized using an input method. In applying the input measure of revenue recognition, the Company uses actual FTE hours incurred relative to estimated total FTE hours expected to be incurred for the respective collaboration program over an estimated service period of four years.

As of December 31, 2023 and 2022, deferred revenue relating to the Moderna Agreement was $24.2 million and $35.0 million, respectively. The amount due from Moderna under the Moderna Agreement was $0 and $35.0 million as of December 31, 2023 and December 31, 2022, respectively.

Regeneron Pharmaceuticals, Inc.

The Company and Regeneron Pharmaceuticals Inc. (“Regeneron”) entered into a Collaboration and License Agreement (the “Regeneron Agreement”) on November 16, 2022, to collaborate on creation of conditionally-activated investigational bispecific cancer therapies utilizing the Company’s PROBODY® therapeutic platform and Regeneron’s Veloci-Bi® bispecific antibody development platform. The Company and Regeneron will collaborate on preclinical research and discovery activities for initially agreed upon collaboration programs (“Collaboration Program”) with an option to expand additional Collaboration Programs (“Additional Collaboration Program Option”).

Under the Collaboration and License Agreement, the Company granted Regeneron an exclusive, worldwide, royalty-bearing license under certain Company intellectual property to develop, manufacture, commercialize and otherwise exploit licensed products (“Licensed Products”) for all human and non-human diagnostic, prophylactic and therapeutic uses in oncology. Regeneron is responsible for funding the cost of preclinical research and discovery activities of both parties for all Licensed Products and for funding the cost of development, manufacturing and commercialization of all Licensed Products worldwide.

Pursuant to the Regeneron Agreement, the consideration from Regeneron is comprised of an upfront fee of $30.0 million, contingent payments for development and regulatory milestones and commercial milestone payments of up to an aggregate of approximately $0.8 billion. If Regeneron exercises its Additional Collaboration Program Option, the Company would be eligible to receive additional upfront and milestone payments aggregating up to approximately $1.2 billion. The Company is also entitled to tiered royalties from high-single digit to low-teen percentage royalties from potential future sales. In addition, the Company will receive research and development service fees based on a prescribed FTE rate.

The Company determined that each collaboration program was a distinct performance obligation consisting of an exclusive research, development and commercialization license, research and development services and participation in the joint research committee. The Company concluded that at the inception of the agreement, Regeneron’s Additional Collaboration Program Option did not include material rights and therefore was not a performance obligation. As such, each option will be accounted for as a separate arrangement upon exercise. The initial transaction price is $39.2 million consisting of the upfront fee of $30.0 million and estimated research and development service fees of $9.2 million. The initial transaction price excludes milestone payments as the achievement of such milestones is dependent on factors outside of the Company’s control and recognition would be probable of significant revenue reversal. As such, the milestones are fully constrained at the inception of the contract. The Company will re-evaluate the transaction price at each reporting date or as uncertain events are resolved or other changes in circumstances occur.

The transaction price was allocated among the performance obligations using the SSP of each performance obligation, which was determined to be equal at the inception of the agreement. The transaction price allocated to each performance obligation is recognized using an input measure. In applying the input measure of revenue recognition, the Company uses actual FTE hours incurred relative to estimated total FTE hours expected to be incurred for the combined performance obligation over the estimated research service period of four years, which is projected to end in November 2026.

As of December 31, 2023 and 2022, deferred revenue relating to the Regeneron Agreement was $24.4 million and $30.0 million, respectively. The amount due from Regeneron under the Regeneron Agreement was $1.1 million and $0 million as of December 31, 2023 and December 31, 2022, respectively.

Contract Liabilities

The following table presents changes in the Company’s total contract liabilities for the years ended in December 31, 2023 and 2022 (in thousands):


	Deferred Revenue
	(in thousands)
Balance at 12/31/2021		284,760
Additions		69,555
Revenue Recognized		(52,989	)
Balance at 12/31/2022		301,326
Additions		6,438
Revenue Recognized		(95,449	)
Balance at 12/31/2023		212,315

The Company expects that the $212.3 million of deferred revenue related to the following contracts as of December 31, 2023 will be recognized as revenue based on actual FTE effort and estimated program progress as set forth below. However, the timing of revenue recognition could differ from the estimates depending on facts and circumstances impacting the various contracts, including progress of research and development, resources assigned to the contracts by the Company or its collaboration partners or other factors outside of the Company’s control.

•

The $12.8 million of deferred revenue related to the Amgen EGFR Products is expected to be recognized until 2026.

•

The $31.0 million of deferred revenue related to the Astellas Agreement is expected to be recognized until 2026.

•

The $119.9 million of deferred revenue related to the BMS Agreement is expected to be recognized until 2025.

•

The $24.2 million of deferred revenue related to the Moderna Agreement is expected to be recognized until 2027.

•

The $24.4 million of deferred revenue related to the Regeneron Agreement is expected to be recognized until 2026.

Common Stock (Tables)

12 Months Ended

Dec. 31, 2023

Warrants and Rights Note Disclosure [Abstract]

Summary of Company's warrants

The following table summarizes the Company's outstanding warrants as of December 31, 2023:


	Pre-funded Warrants				Tranche 1 Warrants				Tranche 2 Warrants
	Number of warrants		Weighted- Average Exercise Price Per Share		Number of warrants		Weighted- Average Exercise Price Per Share		Number of warrants		Weighted- Average Exercise Price Per Share

Warrants Outstanding		14,423,077	$	0.00001		5,769,231	$	4.16		5,769,231	$	6.24

Leases - Summary of Supplemental Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 5,420	$ 5,273
Weighted-average remaining lease term (in years)
Operating lease	2 years 9 months	3 years 9 months
Weighted-average discount rate
Operating lease	8.25%	8.25%

Intangible Asset - Schedule of Intangible Assets (Details) - PROBODY platform intangible asset [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Intangible assets
Intangible assets, gross	$ 1,750	$ 1,750
Less accumulated amortization	(1,021)	(875)
Intangible assets, net	$ 729	$ 875

Collaboration and License Agreements - Bristol-Myers Squibb Company - Additional Information (Details) $ in Thousands			1 Months Ended		12 Months Ended
	Apr. 25, 2017 USD ($) Target	Jul. 07, 2014 USD ($) Term Target	Mar. 31, 2020 USD ($)	Jan. 31, 2018 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Oct. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Feb. 29, 2020 USD ($)	Nov. 30, 2017 USD ($)	Mar. 17, 2017 Target	Dec. 31, 2016 USD ($)	Jan. 31, 2016 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized					$ 101,214	$ 53,163
Type of Revenue [Extensible List]					us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Deferred revenue					$ 212,315	$ 301,326		$ 284,760
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 119,900
Collaborative Arrangement \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration target research term		2 years
Number of additional collaboration target \| Target		2
Research terms					Each collaboration target had a two-year research term and the two additional targets had to be nominated by Bristol Myers Squibb within five years of the effective date of the BMS Agreement. The research term for each collaboration target could be extended in one year increments up to three times.
Extension of research term for each collaboration target		1 year
Upfront payment received	$ 200,000	$ 50,000
Contingent milestone payments receivable							$ 2,100,000		$ 10,000			$ 15,000	$ 10,000
Number of research targets selected \| Target	8
Total transaction price		304,700
Upfront fee received		250,000
Research and development service fees		17,700
Milestone payment received			$ 10,000	$ 12,000
Milestone payments received					$ 297,000
Deferred revenue					$ 119,900	$ 169,200
Collaborative Arrangement \| Bristol Myers Squibb \| Pre Clinical Candidate
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable												$ 2,000
Collaborative Arrangement \| Bristol Myers Squibb \| Third And Fourth Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Target selection fee		$ 25,000
Collaborative Arrangement \| Bristol Myers Squibb \| New Drug Application for CTLA-4
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable										$ 10,000
Collaborative Arrangement \| Maximum \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of oncology target \| Target		4
Number of collaboration target \| Target		2
Period of nomination of additional target from effective date		5 years
Times of increments for extended collaboration target research time \| Term		3
Collaborative Arrangement \| Maximum \| Bristol Myers Squibb \| Each Of Two Additional Targets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable		$ 25,000
Collaboration and License Agreement \| Maximum \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of additional collaboration target \| Target											8

License Agreement - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions					1 Months Ended		12 Months Ended
	Aug. 22, 2023	Mar. 23, 2020	Apr. 25, 2017	Jul. 07, 2014	Apr. 30, 2019	Apr. 30, 2016	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2019
License Agreement [Line Items]
Annual minimum royalty obligations							$ 0.2
License termination period							60 days
Common stock, shares issued							67,310,838	66,228,046
Seattle Genetics Agreement
License Agreement [Line Items]
Annual license maintenance fees	$ 0.3
Sublicense fees							$ 0.3
Bristol Myers Squibb \| Collaborative Arrangement
License Agreement [Line Items]
Upfront payment received			$ 200.0	$ 50.0
Astellas Pharma Inc. \| Collaboration and License Agreement
License Agreement [Line Items]
Sublicense fees							0.2
Upfront payment received		$ 80.0
AbbVie Ireland Unlimited Company \| Discovery Agreement
License Agreement [Line Items]
Upfront payment received						$ 10.0
Immuno Gen Inc \| Collaborative Arrangement
License Agreement [Line Items]
Upfront payment received									$ 7.5
Immuno Gen Inc \| Clinical development milestones \| Maximum
License Agreement [Line Items]
Milestone payment									35.0
Immuno Gen Inc \| Regulatory approval and commercial milestone \| Maximum
License Agreement [Line Items]
Milestone payment									$ 320.0
UCSB
License Agreement [Line Items]
Common stock, shares issued					150,000
Fair value of common stock price per share					$ 10.68
Payment of upfront fees					$ 1.0
Annual license maintenance fees					$ 0.8
License payment term					2031
Percentage of remaining maintenance fees outstanding					50.00%
Sublicense fees							$ 1.1	$ 1.0
Amgen \| Collaboration and License Agreement
License Agreement [Line Items]
Sublicense fees								$ 0.1

Income Taxes - Schedule of Effective Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. federal taxes at statutory rate	21.00%	21.00%
State tax, net of federal benefit	(478.70%)	1.70%
Stock compensation	47.20%	(2.10%)
Tax credits	242.70%	2.40%
Change in valuation allowance	283.20%	(22.80%)
162(m) limitation	1.20%	(0.20%)
Other	0.50%	0.00%
Total	117.10%	0.00%

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 17,171	$ 193,650
Restricted cash - non-current assets	917	917
Total	$ 18,088	$ 194,567	$ 206,447

Leases - Schedule of Subleasing (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 1,333
2025	1,379
2026	1,067
Total sublease income payments	$ 3,779

Leases - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2015
Operating Leased Assets [Line Items]
Restricted cash - non-current assets	$ 917	$ 917
Rent expense	5,100	5,100
Letter of Credit
Operating Leased Assets [Line Items]
Letter of credit outstanding, amount	900
Restricted cash - non-current assets	$ 900	$ 900
New Lease Agreement
Operating Leased Assets [Line Items]
Lease term description	The 2016 Lease has an initial term of ten years through 2026 and the Company has an option to extend the initial term for an additional five years at the then fair rental value as determined pursuant to the 2016 Lease.
Initial lease term	10 years
Extended lease term			5 years
Sublease Income	$ 900

Collaboration and License Agreements - Summary of Contract Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Beginning Balance	$ 301,326	$ 284,760
Additions	6,438	69,555
Revenue recognized	95,449	(52,989)
Ending Balance	$ 212,315	$ 301,326

License Agreement

12 Months Ended

Dec. 31, 2023

Research and Development [Abstract]

License Agreement

9. License Agreement

UCSB

The Company has an exclusive, worldwide license agreement with UCSB (the “UCSB Agreement”), relating to the use of certain patents and technology relating to its core technology, including its therapeutic antibodies, and to certain patent rights the Company co-owns with UCSB covering PROBODY antibodies and other pro-proteins.

Pursuant to the UCSB Agreement, the Company is obligated to (i) make royalty payments to UCSB on net sales of its products covered under the agreement, subject to annual minimum amounts, (ii) make milestone payments to UCSB upon the occurrence of certain events, (iii) make a milestone payment to UCSB upon occurrence of an IPO or change of control, and (iv) reimburse UCSB for prosecution and maintenance of the licensed patents. If the Company sublicenses its rights under the UCSB Agreement, it is obligated to pay UCSB a percentage of the total sublicense revenue received, which total amount would be first reduced by the aggregate amount of certain research and development related expenses incurred by the Company and other permitted deductions. As part of the UCSB Agreement, the Company has annual minimum royalty obligations of $0.2 million under the terms of certain exclusive licensed patent rights. The royalty obligations are cancellable any time by giving notice to the licensor, with the termination being effective 60 days after giving notice.

In April 2019, the Company entered into Amendment No.3 to the UCSB Agreement to adjust and clarify certain sublicense terms (“Amendment No.3”). In connection with the amendment, the Company issued to UCSB 150,000 shares of CytomX common stock with a fair value of $10.68 per share. Under the terms of Amendment No.3, the Company and UCSB agreed to modify the determination of sublicense revenues payable by the Company to UCSB on certain existing collaboration agreements and on collaboration agreements executed subsequent to Amendment No.3. In exchange, the Company agreed to make an upfront payment of $1.0 million as well as additional annual license maintenance fees of $0.8 million through 2031. In the event that the Company terminates the agreement due to material concern of the safety or efficacy of the related technology, 50% of all remaining maintenance fees will become due immediately. Otherwise, all remaining maintenance fees will become due immediately upon early termination of the agreement unless there is a material breach by UCSB.

In 2022, the Company incurred $0.1 million of sublicense fees triggered by the IND for the EGFR product and the dosing of the first patient of the EGFR program under the Amgen Agreement. In 2023, the Company incurred $0.2 million of sublicense fees triggered by achieving the clinical candidate milestone under the Astellas Agreement.

During the years ended December 31, 2023 and 2022, the Company incurred sublicense expenses of $1.1 million and $1.0 million, respectively, under the provisions of the UCSB Agreement.

ImmunoGen (acquired by AbbVie in 2024)

In December 2019, the Company entered into a License Agreement (the “ImmunoGen 2019 License”) with ImmunoGen, Inc. to obtain an exclusive license with respect to epithelial cell adhesion molecule (“EPCAM”). Under the ImmunoGen 2019 License, ImmunoGen agreed to transfer its know-how, patents, intellectual property rights, and technology transfer materials and information related to its EpCAM program. The license gives the Company the sole ability to develop, manufacture, use and commercialize any licensed product that incorporates, is comprised of, or otherwise derived from PROBODY technology that targets EpCAM in any human therapeutic field on a worldwide basis. In exchange, the Company made an upfront license payment of $7.5 million, and will

pay up to $35.0 million in certain clinical development milestones and up to $320.0 million in regulatory approval and commercial milestone payments, if achieved. ImmunoGen is also entitled to royalties on product sales ranging from the mid-to-high single digits percentages.

Seattle Genetics, Inc ("SGEN")

In August 22, 2023, the Company entered into a Transition Agreement (the “Transition Agreement”) with AbbVie Global Enterprises Ltd. (“AbbVie”), pursuant to which the Company regained exclusive worldwide rights to develop CX-2029, a CD71-targeting conditionally activated antibody drug conjugate. The Transition Agreement supersedes the CD71 Co-Development and License Agreement (the “Collaboration Agreement”) entered into between the Company and AbbVie Ireland Unlimited Company (an affiliate entity of AbbVie) in 2016, that was terminated in May 2023, and grants certain intellectual property rights from AbbVie to enable the continued development of CX-2029 by Company for all human and nonhuman diagnostic, prophylactic, and therapeutic uses.

Pursuant to the Transition Agreement, AbbVie is eligible to receive tiered sales royalties for CX-2029 ranging from the low-to-mid single digit percentages. CytomX will also pay SGEN potential future development, regulatory, and commercial milestones, and tiered sales royalties ranging from the mid-to-high single digits percentages related to certain CX-2029 linker payload technology licensed from SGEN. The Company’s royalty obligations for a particular CX-2029 product sold in any country shall continue until the later of (i) the date on which such CX-2029 product is no longer covered by certain patent rights in such country, (ii) the loss of regulatory exclusivity for such CX-2029 product in such country, or (iii) the tenth anniversary of the first commercial sale for such CX-2029 product in such country. Pursuant to the Transition Agreement, the Company will pay an annual exclusive license maintenance fee of $0.3 million starting 2023 through the date on which licensee receives first regulatory approval in the territory for the applicable licensed product.

The Transition Agreement will continue in effect on a country-by-country basis until the expiration of the obligation to make payments under the Transition Agreement with respect to CX-2029 in each country, unless earlier terminated by either party pursuant to its terms. Either the Company or AbbVie may terminate the Transition Agreement for the other party’s insolvency or certain uncured breaches; the Company may terminate the Transition Agreement without cause; and AbbVie may terminate the Transition Agreement if the Company or any of its sublicensees or affiliates challenge certain SGEN patents.

During the year ended December 31, 2023, the Company incurred sublicense expenses of $0.3 million under the provisions of the Transition Agreement.

Intangible Asset - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Finite Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 146	$ 146
PROBODY platform intangible asset
Finite Lived Intangible Assets [Line Items]
Average estimated lives of patents	12 years
Amortization expense of intangible assets	$ 100	$ 100

Restructuring

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Restructuring

16. Restructuring

On July 13, 2022, the Company announced a restructuring plan to prioritize its resources on its emerging pre-clinical and early clinical pipeline as well as its existing collaboration partnerships. The restructuring plan resulted in a reduction to its workforce of approximately 40%. Restructuring costs of $2.4 million and $5.1 million were recorded in general and administrative expense and research and development expense, respectively, for the year ended December 31, 2022. The restructuring was complete in the third quarter of 2023.

The following is a summary of accrued restructuring costs as of December 31, 2023 and 2022 (in thousands):


	Severance and Benefits Costs			Contract Termination Cost			Total
Balance at December 31, 2022		1,512			164			1,676
Cash payment		(1,457	)		(50	)		(1,507	)
Change in estimates		(55	)		(114	)		(169	)
Balance at December 31, 2023	$	—		$	—		$	—

Basis of Presentation and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

2. Basis of Presentation and Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Use of Estimates

The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.

Concentration of Credit Risk and Other Risks and Uncertainties

The Company is subject to a number of risks similar to other biopharmaceutical companies in the early stage, including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, and protection of proprietary technology. If the Company does not successfully obtain regulatory approval, commercialize or partner any of its product candidates, it will be unable to generate revenue from product sales or achieve profitability.

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents, short-term investments and accounts receivable. Substantially all the Company’s cash is held by one financial institution. Such deposits may, at times, exceed federally insured limits. The Company invests its cash equivalents in highly rated money market funds and its short-term investments in U.S. Treasury securities.

Segments

Management has determined that it has one business activity and operates as one operating segment as it only reports financial information on an aggregate basis to its Chief Executive Officer and Principal Financial Officer, who are the Company’s chief operating decision makers. All long-lived assets are maintained in the United States of America.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments purchased with original maturities of three months or less at the date of purchase to be cash equivalents. Restricted cash represents a standby letter of credit issued pursuant to an office lease.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the amounts shown in the statements of cash flows:


	December 31
	2023		2022
	(in thousands)
Cash and cash equivalents	$	17,171	$	193,650
Restricted cash - non-current assets		917		917
Total	$	18,088	$	194,567

Investments

All investments have been classified as available-for-sale (“AFS”) and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments that are required for use in current operations and that mature in less than 12 months are classified as short-term investments in the accompanying balance sheets. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold.

The Company assesses impairment of its AFS debt securities investments at each reporting period. Unrealized gains resulting from the excess of the fair value over the amortized cost basis of an investment are reported as a component of accumulated other comprehensive income (loss), net of tax. Unrealized losses or impairments resulting from the fair value of the AFS debt security being below the amortized cost basis are evaluated, using the discounted cash flow model, for identification of credit losses and non-credit related losses. Any credit losses are charged to earnings against the allowance for credit losses of the security, limited to the difference between the fair value and the amortized cost basis of the security. Any difference between the fair value of the security and the amortized cost basis, less the allowance for credit losses, are reported in other comprehensive income (loss). Expected cash inflows due to improvements in credit are recognized through a reversal of the allowance for credit losses subject to the total allowance previously recognized.

In the event of impairment of any security, if management (i) has the intent to sell such security or (ii) will more-likely-than-not be required to sell such security before recovery of its amortized cost basis, such AFS debt security’s amortized cost basis will be written down to its fair value through earnings along with any existing allowance for credit losses.

Property and Equipment, net

Property and equipment are recorded at cost net of accumulated depreciation and amortization. Depreciation is provided using the straight-line method over the estimated useful lives of the respective assets. The useful lives of property and equipment are as follows:


Machinery and equipment		5 years
Computer equipment and software		3 years
Furniture and fixtures		3 years
Leasehold improvements		Shorter of remaining lease term or estimated life of the assets

Maintenance and repairs that do not extend the life or improve the asset are expensed when incurred.

Goodwill and Intangible Assets

Goodwill represents the excess of the purchase price paid over the fair value of tangible and identifiable intangible assets acquired in business combinations. Goodwill and other intangible assets with indefinite lives are not amortized, but are assigned to reporting units and tested for impairment annually, or whenever there is an impairment indicator. Intangible assets are comprised of in-process research and development. The Company assesses impairment indicators annually as of December 31 or more frequently, if a change in circumstances or the occurrence of events suggests the remaining value may not be recoverable. Intangible assets that are not deemed to have an indefinite life are amortized over their estimated useful lives. There was no impairment of goodwill or intangible assets identified during the years ended December 31, 2023 and 2022.

Impairment of Long-Lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset (or asset group) may not be recoverable and prior to any goodwill impairment test. An impairment loss is recognized when the total of estimated undiscounted future cash flows expected to result from the use of the asset (or asset group) and its eventual disposition is less than its carrying amount. Impairment, if any, would be assessed using discounted cash flows or other appropriate measures of fair value. During the year ended December 31, 2023, there was no impairment of long-lived assets. During the year ended December 31, 2022, the Company recorded an impairment loss of $0.3 million related to certain machinery and equipment.

Revenue Recognition

The Company’s revenues are primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses for the Company’s technology or programs, (ii) research and development services, and (iii) services or obligations in connection with participation in research or steering committees. Payments to the Company under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, research funding, milestone and other contingent payments to the Company for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products.

The Company assesses whether the promises in its arrangements with customers are distinct performance obligations that should be accounted for separately. Judgment is required to determine whether the license to the Company’s intellectual property is distinct from the research and development services or participation on steering committees.

The Company’s collaboration and license agreements may include contingent payments related to specified research, development and regulatory milestones. Such milestone payments are typically payable under the collaborations when the collaboration partner claims or selects a target, or initiates or advances a covered product candidate in preclinical or clinical development, upon submission for marketing approval of a covered product with regulatory authorities, or upon receipt of actual marketing approvals of a covered product or for additional indications. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At each reporting date, the Company re-evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price in such period of determination.

The Company’s collaboration and license agreements may also include contingent payments related to sales-based milestones. Sales-based milestones are typically payable when annual sales of a covered product reach specified levels. Sales-based milestones are recognized at the later of when the associated performance obligation has been satisfied or when the sales occur. Unlike other contingency payments, such as regulatory milestones, sales-based milestones are not included in the transaction price based on estimates at the inception of the contract; instead, they are included when the sales or usage occur.

The transaction price in each arrangement is allocated to the identified performance obligations based on the relative standalone selling price (“SSP”) of each distinct performance obligation, which requires judgment. In instances where SSP is not directly observable, such as when a license or service is not sold separately, SSP is determined using information that may include market conditions and other observable inputs. Due to the early stage of the Company’s licensed technology, the license of such technology is typically combined with research and development services and steering committee participation as one performance obligation. In the event that the Company receives non-cash consideration such as consideration in the form of a research license and research support services from the counterparty, the transaction price of a non-monetary exchange that has commercial substance is estimated based on the fair value of the non-cash consideration received, which may be determined through a valuation analysis.

In certain cases, the Company’s performance creates an asset that does not have an alternative use to the customer and the Company has an enforceable right to payment at all times for performance completed to date. In these cases, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Any consideration payable to the Company’s customers is treated as a reduction to the transaction price and revenue, unless the payment to the customer is in exchange for distinct good and services.

Comprehensive Income (Loss)

Comprehensive income (loss) represents all changes in stockholders’ equity (deficit) except those resulting from distributions to stockholders. The Company’s non-credit related unrealized gains and losses on investments during the period represent the component of other comprehensive income (loss) that is excluded from the reported net loss.

Contract Balances

Customer payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company satisfies its performance obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional.

Research and Development Expenses

The Company records accrued liabilities for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced, and includes these costs in accrued liabilities in the balance sheets and within research and development expense in the statements of operations. These costs are a significant component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers under the service agreements. The Company makes significant judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations.

Research and development expenses include costs directly attributable to the conduct of research and development programs, including the cost of salaries, payroll taxes, employee benefits, materials, supplies, depreciation on and maintenance of research equipment, the cost of services provided by outside contractors, and the allocated portions of facility costs, such as rent, utilities, insurance, repairs and maintenance, depreciation, and general support services. All costs associated with research and development are expensed as incurred.

Stock-based Compensation

The Company measures compensation expense for all stock-based payment awards, including employee stock options, restricted stock units ("RSUs"), and employee stock purchases related to Employee Stock Purchase Plan ("ESPP") based on estimated fair values of the award at the grant date, and recognizes compensation expense over the requisite service vesting period. Stock options forfeitures are accounted for in the period in which they occur.

To determine the fair value of a stock option award on the grant date, the Company uses the Black-Scholes option pricing model which consist of estimating variables such as the following. These estimates involve inherent uncertainties and the application of judgment.

Expected term. The expected term of stock options represents the period that the stock options are expected to remain outstanding and is based on the Company's historical exercise experience with previously issued employee and board of directors' option grants. The expected term of the ESPP shares is equal to the six-month look-back period.

Expected volatility. The expected stock price volatility for the Company’s stock options is based on the historical stock price volatility which is commensurate with the estimated expected term of the stock awards. Volatility for ESPP shares is equal to the Company’s historical volatility over a six-month offering period.

Risk-free interest rate. The risk-free interest rate is based on the U.S. Treasury yield with a maturity equal to the expected term of the stock options in effect at the time of grant.

Dividend yield. The expected dividend is assumed to be zero as the Company has never paid dividends and has no current plan to pay any dividends on its common stock.

The Company measures its restricted stock unit awards based on the market price of the Company’s common shares on the date of grant. Share-based compensation expense for performance-based awards is recognized when it becomes probable that the performance condition will be met. The Company reassesses the estimated probability at each reporting period, and if it is determined at a future date that a performance condition is probable of being achieved, the Company will recognize a cumulative catch-up adjustment and record the remaining expense ratably over the remaining requisite service period.

Income Taxes

The Company accounts for income taxes using an asset and liability approach. Deferred tax assets and liabilities reflect the net tax effects of temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company records a valuation allowance to reduce its deferred tax assets to reflect the net amount that it believes as more likely than not to be realized. Realization of the deferred tax assets is dependent on the generation of future taxable income, the amount and timing of which are uncertain. The valuation allowance requires an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable. Based upon the weight of available evidence at December 31, 2023, the Company continues to maintain a full valuation allowance against all of its deferred tax assets.

The Company recognizes the tax effects of an uncertain tax position only if it is more likely than not that it will be sustained based solely on its technical merits as of the reporting date and only in an amount more likely than not that it will be sustained upon review by the tax authorities. The Company evaluates uncertain tax positions on a quarterly basis and adjust the liability for changes in facts and circumstances, such as new regulations or interpretations by the taxing authorities, new information obtained during a tax examination, significant amendment to an existing tax law, or resolution of an examination. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will impact the income tax provision in the period in which such determination is made. The resolution of its uncertain income tax positions is dependent on uncontrollable factors such as law changes, new case law, and the willingness of the income tax authorities to settle, including the timing thereof and other factors. Interest and/or penalties related to income tax matters are recognized as a component of income tax expense.

Leases

The Company determines if an arrangement is or contains a lease at inception. Operating leases are recorded as operating lease right-of-use (“ROU”) assets and operating lease liabilities in the Company’s balance sheet. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. The Company uses an implicit rate when readily available, or its incremental borrowing rate based on the information available at lease commencement date in determining the present value of lease payments. The operating lease ROU assets also include any lease prepayments made and reduced by lease incentives. The Company’s lease terms may include options to extend the lease when it is reasonably certain that such option will be exercised. Lease expenses are recognized on a straight-line basis over the lease term. The Company elected the short-term lease recognition exemption. The Company’s operating lease arrangement includes lease and non-lease components which are generally accounted for separately.

Collaboration and License Agreements - ModernaTX, Inc - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		$ 212,315	$ 301,326	$ 284,760
Revenue recognized		101,214	53,163
ModernaTX, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		24,200
ModernaTX, Inc \| Collaboration and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	$ 35,000
Upfront consideration, pre-paid research and development service fees	5,000
Total transaction price		51,700
Upfront Fee Received		30,000
Estimated research fund		21,700
Deferred revenue		24,200	35,000
Amount due from agreement		$ 0	$ 35,000
Estimated research service period		4 years
ModernaTX, Inc \| Collaboration and License Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	$ 1,200,000

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Components of Provision for Income Taxes

The components of the provision for income taxes are as follows (in thousands):


	Years Ended December 31,
	2023		2022
Current:
Federal	$	—	$	—
State		3,892		—
Total current		3,892		—
Deferred:
Federal		—		—
State		—		—
Total deferred		—		—
Provision for income taxes	$	3,892	$	—

Schedule of Effective Tax Rate Reconciliation

A reconciliation of the Company’s effective tax rate to the statutory U.S. federal rate is as follows:


	Years Ended December 31,
	2023			2022
U.S. federal taxes at statutory rate		21.0	%		21.0	%
State tax, net of federal benefit		(478.7	)		1.7
Stock compensation		47.2			(2.1	)
Tax credits		242.7			2.4
Change in valuation allowance		283.2			(22.8	)
162(m) limitation		1.2			(0.2	)
Other		0.5			-
Total		117.1	%		0.0	%

Schedule of Deferred Income Tax Assets and Liabilities

The types of temporary differences that give rise to significant portions of the Company’s deferred income tax assets and liabilities are set out below (in thousands):


	Year Ended December 31,
	2023			2022
Net operating loss carryforwards	$	56,767		$	58,193
Research and development credits		22,149			24,700
Lease liability		3,501			3,802
Intangible assets		4,400			3,708
Deferred revenue		47,286			49,919
Accrued liabilities		2,425			1,504
Stock-based compensation		9,600			8,066
Sec 174 capitalized research and development costs		32,630			19,709
Other		55			31
Total gross deferred income tax assets		178,813			169,632
Less: valuation allowance		(175,454	)		(166,037	)
Deferred tax assets, net of valuation allowance		3,359			3,595
Fixed assets		(105	)		(43	)
Right-of-use assets		(3,061	)		(3,358	)
Prepaid expenses		(193	)		(194	)
Deferred tax liabilities		(3,359	)		(3,595	)
Net deferred income tax liabilities	$	—		$	—

Schedule of Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending unrecognized tax benefit amount is as follows (in thousands):


	Year Ended December 31,
	2023		2022
Balance at the beginning of the year	$	9,269	$	7,780
Additions based on tax positions related to current year		527		1,391
Adjustment based on tax positions related to prior years		9,581		98
Balance at end of the year	$	19,377	$	9,269

Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Components of Deferred Tax Assets and Liabilities [Abstract]
Net operating loss carryforwards	$ 56,767	$ 58,193
Research and development credits	22,149	24,700
Lease liability	3,501	3,802
Intangible assets	4,400	3,708
Deferred revenue	47,286	49,919
Accrued liabilities	2,425	1,504
Stock-based compensation	9,600	8,066
Sec 174 capitalized research and development costs	32,630	19,709
Other	55	31
Total gross deferred income tax assets	178,813	169,632
Less: valuation allowance	(175,454)	(166,037)
Deferred tax assets, net of valuation allowance	3,359	3,595
Fixed assets	(105)	(43)
Right-of-use assets	(3,061)	(3,358)
Prepaid expenses	(193)	(194)
Deferred tax liabilities	(3,359)	(3,595)
Net deferred income tax liabilities	$ 0	$ 0

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

3. Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is the same as basic net loss per share since the effect of the potentially dilutive securities is anti-dilutive.

Basic and diluted net loss per share attributable to common stockholders for the years ended December 31, 2023 and 2022 are calculated as follows (in thousands, except share and per share data):


	Year Ended December 31,
	2023			2022
Numerator:
Net loss	$	(569	)	$	(99,317	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted-average common shares outstanding		66,655,971			65,739,844
Weighted-average pre-funded warrants		7,152,266			—
Weighted-average common shares outstanding used to calculate basic and diluted net loss per share		73,808,237			65,739,844
Net loss per share, basic and diluted
Basic and Diluted	$	(0.01	)	$	(1.51	)

The following weighted-average outstanding shares of potentially dilutive securities are excluded from the computation of diluted net loss per share for the periods presented, because including them would have been anti-dilutive:


	Year Ended December 31,
	2023		2022
Options and ESPP to purchase common stock		13,805,472		14,292,729
Common stock warrants		5,675,167		—
RSUs		1,820,589		1,201,058
Total		21,301,228		15,493,787

Property and Equipment

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment

5. Property and Equipment

Property and equipment, net consisted of the following:


	December 31
	2023			2022
	(in thousands)
Laboratory equipment	$	14,119		$	14,002
Computer equipment and software		1,125			1,942
Furniture and fixtures		1,051			1,054
Leasehold improvements		1,983			1,742
Construction in progress		368			705
		18,646			19,445
Less: accumulated depreciation and amortization		(14,688	)		(14,373	)
	$	3,958		$	5,072

Depreciation and amortization expense was $2.0 million and $2.3 million for the years ended December 31, 2023 and 2022, respectively.

Fair Value Measurements and Investments (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Investments Subject to Fair Value Measurements on a Recurring Basis

The following tables set forth the fair value of the Company’s investments subject to fair value measurements on a recurring basis and the level of inputs used in such measurements:


		December 31, 2023
	Valuation Hierarchy	Amortized Cost		Unrealized Gains		Aggregate Fair Value
		(in thousands)
Assets
Money market funds	Level I	$	17,109	$	—	$	17,109
Restricted cash (money market funds)	Level I		917		—		917
U.S. Treasury securities	Level II		157,243		95		157,338
Total		$	175,269	$	95	$	175,364


		December 31, 2022
	Valuation Hierarchy	Amortized Cost		Unrealized Gains		Aggregate Fair Value
		(in thousands)
Assets
Money market funds	Level I	$	64,706	$	—	$	64,706
Restricted cash (money market funds)	Level I		917		—		917
U.S. Treasury securities	Level II		29,941		10		29,951
Total		$	95,564	$	10	$	95,574

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Activities Under Company's Stock Option Plans

The following table summarizes the Company's stock option activities:


				Options Outstanding
	Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value
								(in thousands)
Balances at December 31, 2022		13,289,838		$	7.67
Options granted		1,938,573			2.20
Options exercised		(16,535	)		1.57			$	5.0
Options cancelled		(2,262,264	)		5.95
Balances at December 31, 2023		12,949,612			7.16		6.51	$	70.5
Options Exercisable—December 31, 2023		8,672,013		$	9.03		5.52	$	4.7

Total Stock-based Compensation Recognized

Total stock-based compensation recorded related to stock options, TRSUs, PSUs and the ESPP was as follows (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	2,921	$	5,544
General and administrative		5,637		7,581
Total stock-based compensation expense	$	8,558	$	13,125

Fair Value Assumptions:

Schedule of Estimated Fair Value of Employee Stock Options and ESPP Using Black-Scholes Valuation Model

The Company estimated the fair value of employee stock options and ESPP using the Black-Scholes valuation model based on the date of grant with the following weighted average assumptions:


	Options				ESPP
	Year Ended December 31,				Year Ended December 31,
	2023		2022		2023		2022
Expected volatility	84%		77%		70%		95%
Risk-free interest rate	4.2%		2.4%		5.4%		2.9%
Dividend yield	—		—		—		—
Expected term (in years)		5.1		4.6		0.5		0.5
Weighted average fair value per share	$	1.52	$	1.77	$	0.55	$	0.67

Time based RSUs

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Company's TRSU Activities

The following table summarizes the Company's TRSU activities:


	Number of Shares			Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value (in thousands)		Weighted Average Grant Date Fair Value Per Share

Balance at December 31, 2022		1,212,884						$	2.81
RSUs awarded		724,342							2.30
RSUs vested		(439,329	)						3.16
RSUs cancelled		(97,368	)						3.41
Balance at December 31, 2023		1,400,529			0.94	$	2,171	$	2.40

Performance based RSUs

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Activities for Company's PSUs

The following table summarizes the Company's PSU activities:


	Number of Shares			Aggregate Intrinsic Value (in thousands)		Weighted Average Grant Date Fair Value Per Share

Balance at December 31, 2022		383,750				$	2.96
PSUs awarded		760,000					2.54
PSUs vested		(220,000	)				3.38
PSUs cancelled		(48,750	)				4.28
Balance at December 31, 2023		875,000		$	1,356	$	2.41

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

Restructuring - Summary of Accrued Restructuring Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring cost, Beginning Balance	$ 1,676
Cash payment	(1,507)
Change of Estimates	(169)
Restructuring cost, Ending Balance	0
Severance and Benefits Costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost, Beginning Balance	1,512
Cash payment	(1,457)
Change of Estimates	(55)
Restructuring cost, Ending Balance	0
Contract Termination Cost
Restructuring Cost and Reserve [Line Items]
Restructuring cost, Beginning Balance	164
Cash payment	(50)
Change of Estimates	(114)
Restructuring cost, Ending Balance	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization		$ 2.0	$ 2.3
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]	Net Income (Loss)

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

11. Leases

Operating Lease

In December 2015, the Company entered into a lease (the “2016 Lease”) of office and laboratory space located in South San Francisco, California for the Company’s corporate headquarters. The 2016 Lease has an initial term of ten years through 2026 and the Company has an option to extend the initial term for an additional five years at the then fair rental value as determined pursuant to the 2016 Lease.

In addition, the Company obtained a standby letter of credit (the “Letter of Credit”) in an amount of approximately $0.9 million, which may be drawn by the Landlord to be applied for certain purposes upon the Company’s breach of any provisions under the 2016 Lease. The Company recorded the $0.9 million of cash securing the Letter of Credit as non-current restricted cash on its balance sheet as of December 31, 2023 and 2022. Rent expense during the years ended December 31, 2023 and 2022 was $5.1 million and $5.1 million, respectively.

Supplemental information related to leases are as follows:


	Year Ended
	December 31, 2023			December 31, 2022
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$	5,420		$	5,273

	December 31, 2023			December 31, 2022
	(in thousands)
Weighted-average remaining lease term (in years)
Operating lease	2.75				3.75
Weighted-average discount rate
Operating lease		8.25	%		8.25	%


	December 31, 2023
	(in thousands)
Maturity of operating lease liabilities
2024		5,572
2025		5,729
2026		4,387
Total lease payments		15,688
Less imputed interest		(1,714	)
Present value of lease liabilities		13,974

In March 2023, the Company entered into a sublease agreement for a portion of its existing office and laboratory space. The sublease is classified as an operating lease whereby sublease income is recognized on a straight-line basis over the sublease term that expires on September 30, 2026. For the year ended December 31, 2023, sublease income was $0.9 million.


	December 31, 2023
	(in thousands)
Future sublease income payments
2024		1,333
2025		1,379
2026		1,067
Total sublease income payments	$	3,779

Property and Equipment - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Laboratory equipment	$ 14,119	$ 14,002
Computer equipment and software	1,125	1,942
Furniture and fixtures	1,051	1,054
Leasehold improvements	1,983	1,742
Construction in progress	368	705
Total property and equipment	18,646	19,445
Less: accumulated depreciation and amortization	(14,688)	(14,373)
Property and equipment, net	$ 3,958	$ 5,072

Leases - Schedule of Maturity of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Maturity of operating lease liabilities
2024	$ 5,572
2025	5,729
2026	4,387
Total lease payments	15,688
Less imputed interest	(1,714)
Present value of lease liabilities	$ 13,974

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning of the year	$ 9,269	$ 7,780
Additions based on tax positions related to current year	527	1,391
Adjustment based on tax positions related to prior years	9,581	98
Balance at end of the year	$ 19,377	$ 9,269

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 17,171	$ 193,650
Short-term investments	157,338	0
Accounts receivable	3,432	35,986
Prepaid expenses and other current assets	4,995	7,466
Total current assets	182,936	237,102
Property and equipment, net	3,958	5,072
Intangible assets, net	729	875
Goodwill	949	949
Restricted cash	917	917
Operating lease right-of-use asset	12,220	15,949
Other assets	83	27
Total assets	201,792	260,891
Current liabilities:
Accounts payable	1,458	2,809
Accrued liabilities	17,599	24,450
Operating lease liabilities - short term	4,589	4,082
Deferred revenues, current portion	132,267	121,267
Total current liabilities	155,913	152,608
Deferred revenue, net of current portion	80,048	180,059
Operating lease liabilities - long term	9,385	13,975
Other long-term liabilities	3,893	0
Total liabilities	249,239	346,642
Commitments and contingencies (Note 10)
Stockholders' deficit
Common stock, $0.00001 par value; 150,000,000 shares authorized, and 67,310,838 and 66,228,046 shares issued and outstanding at December 31, 2023 and 2022, respectively	1	1
Additional paid-in capital	675,905	637,117
Accumulated other comprehensive income	95	10
Accumulated deficit	(723,448)	(722,879)
Total stockholders' deficit	(47,447)	(85,751)
Total liabilities and stockholders' deficit	201,792	260,891
Convertible Preferred Stock
Stockholders' deficit
Convertible preferred stock, $0.00001 par value; 10,000,000 shares authorized and no shares issued and outstanding	$ 0	$ 0

Common Stock

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common Stock

12. Common Stock

In June 2023, the Company entered into an agreement with BVF Partners L.P. (“BVF”) for a private placement and received an aggregate net proceeds of approximately $29.7 million in July 2023, after deducting issuance costs of approximately $0.3 million. In the private placement, CytomX issued pre-funded warrants to BVF to purchase up to 14,423,077 shares of common stock, accompanying Tranche 1 warrants to purchase up to 5,769,231 shares of common stock and accompanying Tranche 2 warrants to purchase up to 5,769,231 shares of common stock, at a combined price of $2.08 per share.

The following table summarizes the Company's outstanding warrants as of December 31, 2023:


	Pre-funded Warrants				Tranche 1 Warrants				Tranche 2 Warrants
	Number of warrants		Weighted- Average Exercise Price Per Share		Number of warrants		Weighted- Average Exercise Price Per Share		Number of warrants		Weighted- Average Exercise Price Per Share

Warrants Outstanding		14,423,077	$	0.00001		5,769,231	$	4.16		5,769,231	$	6.24

The pre-funded warrants will expire in July 2043, while Tranche 1 and Tranche 2 warrants will expire in July 2025 and July 2026, respectively.

Stock-based Compensation - Schedule of Company's TRSU Activities (Details) - Time based RSUs $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance at December 31, 2022 \| shares	1,212,884
Units awarded \| shares	724,342
Units vested \| shares	(439,329)
Units cancelled \| shares	(97,368)
Balance at December 31, 2023 \| shares	1,400,529
Weighted Average Remaining Contractual Life (years)
Balance at December 31, 2023	11 months 8 days
Aggregate Intrinsic Value
Balance at December 31, 2023 \| $	$ 2,171
Weighted Average Grant Date Fair Value
Balance at December 31, 2022 \| $ / shares	$ 2.81
Units awarded \| $ / shares	2.3
Units vested \| $ / shares	3.16
Units cancelled \| $ / shares	3.41
Balance at December 31, 2023 \| $ / shares	$ 2.4

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Summary of Calculation of Basic and Diluted Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders for the years ended December 31, 2023 and 2022 are calculated as follows (in thousands, except share and per share data):


	Year Ended December 31,
	2023			2022
Numerator:
Net loss	$	(569	)	$	(99,317	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted-average common shares outstanding		66,655,971			65,739,844
Weighted-average pre-funded warrants		7,152,266			—
Weighted-average common shares outstanding used to calculate basic and diluted net loss per share		73,808,237			65,739,844
Net loss per share, basic and diluted
Basic and Diluted	$	(0.01	)	$	(1.51	)

Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share


	Year Ended December 31,
	2023		2022
Options and ESPP to purchase common stock		13,805,472		14,292,729
Common stock warrants		5,675,167		—
RSUs		1,820,589		1,201,058
Total		21,301,228		15,493,787

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (569)	$ (99,317)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of intangible assets	146	146
Depreciation and amortization	2,029	2,297
Impairment loss on machinery and equipment	0	254
Accretion of discounts on short-term investments	(7,419)	(52)
Stock-based compensation expense	8,558	13,125
Non-cash lease expense	3,729	3,413
Changes in operating assets and liabilities
Accounts receivable	32,554	(35,196)
Prepaid expenses and other current assets	2,471	(3,181)
Other assets	(56)	874
Accounts payable	(1,426)	68
Accrued liabilities and other long-term liabilities	(7,041)	(9,784)
Deferred revenue	(89,011)	16,565
Net cash used in operating activities	(56,035)	(110,788)
Cash flows from investing activities:
Purchases of property and equipment	(840)	(1,740)
Purchases of short term investments	(424,834)	0
Maturities of short term investments	275,000	100,000
Net cash (used in) provided by investing activities	(150,674)	98,260
Cash flows from financing activities:
Proceeds from issuance of pre-funded warrants and warrants, net of issuance cost	29,669	0
Proceeds from employee stock purchase plan and exercise of stock options	561	648
Net cash provided by financing activities	30,230	648
Net decrease in cash, cash equivalents and restricted cash	(176,479)	(11,880)
Cash, cash equivalents and restricted cash, beginning of year	194,567	206,447
Cash, cash equivalents and restricted cash, end of year	18,088	194,567
Supplemental disclosures of noncash investing items:
Purchases of property and equipment in accounts payable and accrued liabilities	$ 75	$ 6

Stock-based Compensation - Schedule of Activities for Company's PSUs (Details) - Performance based RSUs - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Feb. 28, 2023	Aug. 31, 2022	Oct. 31, 2021	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance at December 31, 2022				383,750
Units awarded	760,000	250,000	435,000	760,000
Units vested				(220,000)
Units cancelled				(48,750)
Balance at December 31, 2023				875,000
Aggregate Intrinsic Value
Balance at December 31, 2023	$ 1,900	$ 400	$ 2,300	$ 1,356
Weighted Average Grant Date Fair Value
Balance at December 31, 2022				$ 2.96
Units awarded				2.54
Units vested				3.38
Units cancelled				4.28
Balance at December 31, 2023				$ 2.41

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Revenue	$ 101,214	$ 53,163
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 77,680	$ 111,649
General and administrative	30,018	42,849
Total operating expenses	107,698	154,498
Loss from operations	(6,484)	(101,335)
Interest income	9,837	1,678
Other income (expense), net	(30)	340
Income (Loss) before income taxes	3,323	(99,317)
Provision for income taxes	3,892	0
Net loss	(569)	(99,317)
Other comprehensive loss:
Unrealized gain on available-for-sale investments, net of tax	85	252
Total comprehensive loss	$ (484)	$ (99,065)
Net loss per share, Basic	$ (0.01)	$ (1.51)
Net loss per share, Diluted	$ (0.01)	$ (1.51)
Shares used to compute net loss per share, Basic	73,808,237	65,739,844
Shares used to compute net loss per share, Diluted	73,808,237	65,739,844

Restructuring (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Summary of Accrued Restructuring Costs

The following is a summary of accrued restructuring costs as of December 31, 2023 and 2022 (in thousands):


	Severance and Benefits Costs			Contract Termination Cost			Total
Balance at December 31, 2022		1,512			164			1,676
Cash payment		(1,457	)		(50	)		(1,507	)
Change in estimates		(55	)		(114	)		(169	)
Balance at December 31, 2023	$	—		$	—		$	—

Defined Contribution Plan

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

Defined Contribution Plan

15. Defined Contribution Plan

The Company sponsors a defined contribution plan under Section 401(k) of the Internal Revenue Code covering substantially all full-time U.S. employees. Employee contributions are voluntary and are determined on an individual basis subject to the maximum allowable under federal tax regulations. During the years ended December 31, 2023 and 2022, the Company made contributions to the plan of $0.5 million, $0.9 million, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (q)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//715/tableOfContent

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (o)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (p)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480126/715-20-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 60
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Stock-based Compensation - Total Stock-based Compensation Recognized (Details) - Options, TRSUs, PSUs and the ESPP - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock-based compensation expense:
Stock-based compensation expense	$ 8,558	$ 13,125
Research and Development Expense [Member]
Stock-based compensation expense:
Stock-based compensation expense	2,921	5,544
General and Administrative Expense [Member]
Stock-based compensation expense:
Stock-based compensation expense	$ 5,637	$ 7,581

Fair Value Measurements and Investments

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements and Investments

4. Fair Value Measurements and Investments

In accordance with Accounting Standards Codification (“ASC”) 820-10, Fair Value Measurements and Disclosures, the Company determines the fair value of financial and non-financial assets and liabilities using the fair value hierarchy, which establishes three levels of inputs that may be used to measure fair value, as follows:

•

Level I: Inputs which include quoted prices in active markets for identical assets and liabilities.

•

Level II: Inputs other than Level I that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•

Level III: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The carrying amounts of the Company’s financial instruments, including restricted cash, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. The Company’s financial instruments consist of Level I assets which consist primarily of highly liquid money market funds, some of which are included in restricted cash; and U.S. Treasury securities that are included in cash equivalent or short-term investments.

The following tables set forth the fair value of the Company’s investments subject to fair value measurements on a recurring basis and the level of inputs used in such measurements:


		December 31, 2023
	Valuation Hierarchy	Amortized Cost		Unrealized Gains		Aggregate Fair Value
		(in thousands)
Assets
Money market funds	Level I	$	17,109	$	—	$	17,109
Restricted cash (money market funds)	Level I		917		—		917
U.S. Treasury securities	Level II		157,243		95		157,338
Total		$	175,269	$	95	$	175,364


		December 31, 2022
	Valuation Hierarchy	Amortized Cost		Unrealized Gains		Aggregate Fair Value
		(in thousands)
Assets
Money market funds	Level I	$	64,706	$	—	$	64,706
Restricted cash (money market funds)	Level I		917		—		917
U.S. Treasury securities	Level II		29,941		10		29,951
Total		$	95,564	$	10	$	95,574

As of December 31, 2023, the remaining contractual terms of the U.S. Treasury securities are less than a year.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stock-based Compensation - Additional Information (Details) - USD ($)		1 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 01, 2016	Feb. 28, 2023	Aug. 31, 2022	Oct. 31, 2021	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020	Dec. 31, 2021	Sep. 30, 2019	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option expiration period							10 years
Options granted generally vest period									36 months
Options granted generally vest percent									2.08%
Aggregate intrinsic value of stock options exercised							$ 5,000
Unrecognized compensation expense, options granted							$ 8,200,000
Number of shares issued during period							406,928	405,192
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost, period for recognition							2 years 2 months 23 days
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of the shares on the date of grant							85.00%
Common stock, capital shares reserved for future issuance							939,698	1,346,626
Unrecognized stock-based compensation cost, period for recognition							5 months
Plan maximum percentage of eligible compensation to purchase shares							15.00%
Stock-based compensation expense							$ 300,000	$ 600,000
Unrecognized stock-based compensation cost							100,000
Time based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, options granted							$ 2,100,000
Unrecognized stock-based compensation cost, period for recognition							1 year 7 months 28 days
Stock-based compensation expense							$ 2,000,000	1,200,000
Granted							724,342
PSU's Awarded, Grant date fair value							$ 2,171,000
Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, options granted							$ 2,000,000
Unrecognized stock-based compensation cost, period for recognition							1 year 5 months 4 days
Stock-based compensation expense								$ 55,000
Granted		760,000	250,000	435,000			760,000
PSU's Awarded, Grant date fair value		$ 1,900,000	$ 400,000	$ 2,300,000			$ 1,356,000
Share-Based Payment Arrangement, Tranche One [Member] \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights, description				Vesting for 50% of the PSUs granted will occur upon achievement of certain specific milestones within one year of the grant date ("2021-Tranche 1") and the remaining 50% will vest upon achievement of additional company objectives within two years of the grant date ("2021-Tranche 2").
Share-Based Payment Arrangement, Tranche Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted generally vest percent							2.08%
Share-Based Payment Arrangement, Tranche Two [Member] \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights, description		Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2024 (“2023-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2025 (“2023-Tranche 2”).	Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2023 (“2022-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2024 (“2022-Tranche 2”).
Two Thousand Fifteen Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option expiration period							10 years
Employees holding voting rights of all classes of stock, percentage							10.00%
Common stock, capital shares reserved for future issuance							2,944,245	1,932,345				2,444,735
Increase in number of shares available for issuance, as proportion of issued and outstanding shares of common stock, percentage	4.00%
Two Thousand Fifteen Stock Incentive Plan [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted generally vest period							4 years
Options granted generally vest percent							25.00%
Two Thousand Nineteen Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance							1,725,656	1,120,740			1,815,000
Increase in Common Stock Capital Shares Reserved For Future Issuance										1,000,000
Tranche One \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense							$ 128,000	$ 1,000,000
Tranche Two \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense					$ 100,000	$ 100,000	$ 106,000
Minimum [Member] \| Two Thousand Fifteen Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of the shares on the date of grant							110.00%
Minimum [Member] \| Two Thousand Nineteen Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of the shares on the date of grant							100.00%
Maximum [Member] \| Two Thousand Nineteen Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option expiration period							10 years

Stock-based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

13. Stock-based Compensation

The 2010 Plan and 2011 Plan

In 2010, the Company adopted its 2010 Stock Incentive Plan (the “2010 Plan”) which provided for the granting of stock options to employees, directors and consultants of the Company. Options granted under the 2010 Plan were either incentive stock options (“ISOs”) or nonqualified stock options (“NSOs”).

In February 2012, the Company adopted its 2011 Stock Incentive Plan (the “2011 Plan”). The 2011 Plan is divided into two separate equity programs, an option and stock appreciation rights grant program and a stock award program. In conjunction with adopting the 2011 Plan, the Company discontinued the 2010 Plan and released the shares reserved and still available under that plan.

In connection with the consummation of the IPO in October 2015, the board of directors adopted the Company’s 2015 Equity Incentive Plan (the “2015 Plan” and collectively with the 2010 Plan and 2011 Plan, the “Plans”). In conjunction with adopting the 2015 Plan, the Company discontinued the 2011 Plan with respect to new equity awards.

The 2015 Plan

The 2015 Plan authorized the board of directors to grant incentive stock options, non-statutory stock options and RSUs to employees, directors, non-employee directors and consultants of the Company. Stock options under the 2015 Plan may be granted for periods of up to ten years. All stock options issued to date have had a 10-year life. Under the terms of the 2015 Plan, stock options may be granted at an exercise price not less than the estimated fair value of the Company’s common stock on the date of grant, as determined by the Company’s board of directors. For employees holding more than 10% of the voting rights of all classes of stock, the exercise price of ISOs and NSOs may not be less than 110% of the estimated fair value of the shares on the date of grant, as determined by the board of directors. To date, stock options granted under the 2015 Plan generally vest over four years and vest at a rate of 25% upon the first anniversary of the issuance date and 1/48th per month thereafter.

The initial number of shares of common stock available for future issuance under the 2015 Plan was 2,444,735. Beginning on January 1, 2016 and continuing until the expiration of the 2015 Plan, the total number of shares of common stock available for issuance under the 2015 Plan will automatically increase annually on January 1 by 4% of the total number of issued and outstanding shares of common stock as of January 1 of the same year. As of December 31, 2023 and 2022, 2,944,245 shares and 1,932,345 shares of common stock, respectively, were available for future issuance under the 2015 Plan.

The 2019 Plan

In September 2019, the Board of Directors adopted the 2019 Employment Inducement Incentive Plan (the “2019 Plan”) which provides for the grant of stock options and other equity awards to any employee who has not previously been an employee or director of the Company or who is commencing employment with the Company following a bona fide period of nonemployment by the Company. Awards granted under the 2019 Plan are intended to constitute “employment inducement awards” under Nasdaq Listing Rule 5635(c)(4). Options granted under the 2019 Plan are nonqualified stock options (“NSOs”) which may be exercisable for periods of up to ten years and the options shall be granted at an exercise price of not less than 100% of the fair market value of the Company’s common stock on the date of grant.

The initial number of shares of common stock available for future issuance under the 2019 Plan was 1,815,000. During 2021, the total number of shares of common stock available for issuance under the 2019 Plan has increased by 1,000,000 shares. As of December 31, 2023 and 2022, 1,725,656 and 1,120,740 shares, respectively, of common stock were available for future issuance under the 2019 Plan.

The following table summarizes the Company's stock option activities:


				Options Outstanding
	Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value
								(in thousands)
Balances at December 31, 2022		13,289,838		$	7.67
Options granted		1,938,573			2.20
Options exercised		(16,535	)		1.57			$	5.0
Options cancelled		(2,262,264	)		5.95
Balances at December 31, 2023		12,949,612			7.16		6.51	$	70.5
Options Exercisable—December 31, 2023		8,672,013		$	9.03		5.52	$	4.7

The aggregate intrinsic values of options exercised, outstanding and exercisable were calculated as the difference between the exercise price of the options and the quoted market price of the underlying common stock as of December 31, 2023.

As of December 31, 2023, the unrecognized compensation expense with respect to options granted was $8.2 million and is expected to be recognized over 2.23 years.

Time-based RSUs ("TRSU")

The following table summarizes the Company's TRSU activities:


	Number of Shares			Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value (in thousands)		Weighted Average Grant Date Fair Value Per Share

Balance at December 31, 2022		1,212,884						$	2.81
RSUs awarded		724,342							2.30
RSUs vested		(439,329	)						3.16
RSUs cancelled		(97,368	)						3.41
Balance at December 31, 2023		1,400,529			0.94	$	2,171	$	2.40

The Company recorded $2.0 million and $1.2 million of stock-based compensation expense related to the TRSUs for the year ended December 31, 2023 and 2022, respectively. As of December 31, 2023, the unrecognized compensation expense with respect to the TRSUs was $2.1 million which is expected to be recognized over 1.66 years. The TSRUs generally vest ratably over two to four years.

Performance-based RSUs ("PSU")

In October 2021, the Company granted 435,000 PSUs to executive employees with an aggregated grant date fair value of $2.3 million. Vesting for 50% of the PSUs granted will occur upon achievement of certain specific milestones within one year of the grant date ("2021-Tranche 1") and the remaining 50% will vest upon achievement of additional company objectives within two years of the grant date ("2021-Tranche 2").

In July 2022, the Company determined that the performance condition for 2021-Tranche 1 was met and recorded $1.0 million of stock-based compensation expense for the year ended December 31, 2022. In September 2023, the performance condition for 2021-Tranche 2 was modified and the award was vested in in September 2023. As a result, the Company recorded $0.1 million of stock-based compensation expense for 2021-Tranche 2 for the three and nine months ended September 30, 2023.

In August 2022, the Company granted 250,000 PSUs to executive employees with an aggregated grant date fair value of approximately $0.4 million. Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2023 (“2022-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2024 (“2022-Tranche 2”). In December 2023, the Company determined that the performance conditions for 2022-Tranche 1 was satisfied and the award was vested in December 2023. As a result, the Company recorded the remaining $128,000 compensation cost for the Tranche 1 award for the year ended December 31, 2023. For the year ended December 31, 2022, the Company recorded $55,000 compensation cost for the Tranche-1 award. As of December 31, 2023, the Company determined that it is probable that the performance conditions for 2022-Tranche 2 will be satisfied and recorded $106,000 compensation cost for the award 2023.

In February 2023, the Company granted 760,000 PSUs to executive employees with an aggregated grant date fair value of approximately $1.9 million. Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2024 (“2023-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2025 (“2023-Tranche 2”). The Company determined that it is not probable that the performance conditions will be satisfied for each of these tranches and no compensation cost was recorded for these awards through December 31, 2023.

The following table summarizes the Company's PSU activities:


	Number of Shares			Aggregate Intrinsic Value (in thousands)		Weighted Average Grant Date Fair Value Per Share

Balance at December 31, 2022		383,750				$	2.96
PSUs awarded		760,000					2.54
PSUs vested		(220,000	)				3.38
PSUs cancelled		(48,750	)				4.28
Balance at December 31, 2023		875,000		$	1,356	$	2.41

As of December 31, 2023, the unrecognized compensation expense with respect to PSUs granted was $2.0 million and is expected to be recognized over 1.43 years.

Employee Stock Purchase Plan

Concurrent with the completion of the IPO in October 2015, the Company’s Employee Stock Purchase Plan (“ESPP”) became effective. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP generally provides for six-month offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. The Company issued 406,928 and 405,192 shares of common stock under the ESPP in 2023 and 2022, respectively.

Shares available for future purchase under the ESPP were 939,698 shares and 1,346,626 shares at December 31, 2023 and 2022, respectively. The compensation expense related to the ESPP was $0.3 million, $0.6 million for the years ended December 31, 2023 and 2022, respectively. As of December 31, 2023, there was $0.1 million of unrecognized compensation cost related to the ESPP, which the Company expects to recognize over 5 months.

Stock Based Compensation

Total stock-based compensation recorded related to stock options, TRSUs, PSUs and the ESPP was as follows (in thousands):


	Year Ended December 31,
	2023		2022
Research and development	$	2,921	$	5,544
General and administrative		5,637		7,581
Total stock-based compensation expense	$	8,558	$	13,125

Fair Value Assumptions:

The Company estimated the fair value of employee stock options and ESPP using the Black-Scholes valuation model based on the date of grant with the following weighted average assumptions:


	Options				ESPP
	Year Ended December 31,				Year Ended December 31,
	2023		2022		2023		2022
Expected volatility	84%		77%		70%		95%
Risk-free interest rate	4.2%		2.4%		5.4%		2.9%
Dividend yield	—		—		—		—
Expected term (in years)		5.1		4.6		0.5		0.5
Weighted average fair value per share	$	1.52	$	1.77	$	0.55	$	0.67

Basis of Presentation and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Cash, Cash Equivalents, and Restricted Cash


	December 31
	2023		2022
	(in thousands)
Cash and cash equivalents	$	17,171	$	193,650
Restricted cash - non-current assets		917		917
Total	$	18,088	$	194,567

Schedule of Useful Lives of Property and Equipment

The useful lives of property and equipment are as follows:


Machinery and equipment		5 years
Computer equipment and software		3 years
Furniture and fixtures		3 years
Leasehold improvements		Shorter of remaining lease term or estimated life of the assets

Accrued Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Research and clinical expenses	$ 8,435	$ 13,089
Payroll and related expenses	8,160	8,060
Legal and professional expenses	690	1,413
Restructuring expenses	0	1,627
Other accrued expenses	314	261
Total	$ 17,599	$ 24,450

Common Stock - Additional Information (Details) - BVF Partners L.P. Private Placement - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Jul. 31, 2023	Dec. 31, 2023
Class Of Stock [Line Items]
Gross proceeds from issuance of private placement	$ 29.7
Price per share	$ 2.08
Issuance cost	$ 0.3
Pre-Funded Warrant
Class Of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	14,423,077
Expiration date		Jul. 31, 2043
Tranche 1 Warrant
Class Of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	5,769,231
Expiration date		Jul. 31, 2025
Tranche 2 Warrant
Class Of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	5,769,231
Expiration date		Jul. 31, 2026

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. Commitments and Contingencies

Legal Proceedings

On March 4, 2020, Vytacera Bio, LLC filed a patent infringement lawsuit against the Company in the U.S. District Court for the District of Delaware. The lawsuit alleges that the Company's use, offers to sell, and/or sales of the PROBODY® technology platform for basic research applications constitutes infringement. The complaint seeks unspecified monetary damages. In September 2022, the Company filed a motion to dismiss the case and the Court granted the parties’ stipulation to stay all pending case deadlines until that motion is finally resolved. On October 30, 2023, Magistrate Judge Burke issued a Report & Recommendation that recommended granting Company’s motion to dismiss all counts of the complaint. In January 2024, the case was transferred to a new judge and the case will remain stayed pending a ruling by the trial judge on the Magistrate’s Report & Recommendation. The Company believes that the lawsuit is without merit and intends to vigorously defend itself. The Company does not believe a loss is probable and has not recorded any amount as a contingent liability for claims associated with this lawsuit as of December 31, 2023.

Indemnifications

In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance.

Restructuring - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
	Jul. 13, 2022	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Percentage of company's workforce reduction	40.00%
General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 2.4
Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 5.1

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Commitments and Contingencies - Additional Information (Details) - Patent Infringement Lawsuit - USD ($) $ in Thousands		12 Months Ended
	Mar. 04, 2020	Dec. 31, 2023
Loss Contingencies [Line Items]
Lawsuit filed date	March 4, 2020
Name of plaintiff		Vytacera Bio, LLC
Loss contingency claim amount		$ 0

Stock-based Compensation - Schedule of Estimated Fair Value of Employee Stock Options and ESPP Using Black-Scholes Valuation Model (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	84.00%	77.00%
Risk-free interest rate	4.20%	2.40%
Dividend yield	0.00%	0.00%
Expected term (in years)	5 years 1 month 6 days	4 years 7 months 6 days
Weighted average fair value per share	$ 1.52	$ 1.77
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	70.00%	95.00%
Risk-free interest rate	5.40%	2.90%
Dividend yield	0.00%	0.00%
Expected term (in years)	6 months	6 months
Weighted average fair value per share	$ 0.55	$ 0.67

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) Activity Segment	Dec. 31, 2022 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of business activities \| Activity	1
Number of operating segments \| Segment	1
Impairment of goodwill	$ 0	$ 0
Impairment of intangible assets	0	0
Impairment loss related to machinery and equipment	$ 0	$ 300,000

Collaboration and License Agreements - Contract Liabilities - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additions to deferred revenue	$ 6,438	$ 69,555
Deductions to deferred revenue recognized during the period	(95,449)	52,989
Deferred revenue	212,315	301,326		$ 284,760
AbbVie Ireland Unlimited Company \| CD71 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue		$ 4,000	$ 4,000
Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 12,800
Deferred Revenue Recognition Maturity Year	2026
Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 31,000
Deferred Revenue Recognition Maturity Year	2026
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 119,900
Deferred Revenue Recognition Maturity Year	2025
ModernaTX, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 24,200
Deferred Revenue Recognition Maturity Year	2027
Regeneron Pharmaceuticals, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 24,400
Deferred Revenue Recognition Maturity Year	2026

Basis of Presentation and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Use of Estimates

Concentration of Credit Risk and Other Risks and Uncertainties

Segments

Cash, Cash Equivalents and Restricted Cash


	December 31
	2023		2022
	(in thousands)
Cash and cash equivalents	$	17,171	$	193,650
Restricted cash - non-current assets		917		917
Total	$	18,088	$	194,567

Investments

Property and Equipment, net


Machinery and equipment		5 years
Computer equipment and software		3 years
Furniture and fixtures		3 years
Leasehold improvements		Shorter of remaining lease term or estimated life of the assets

Maintenance and repairs that do not extend the life or improve the asset are expensed when incurred.

Goodwill and Intangible Assets

Impairment of Long-Lived Assets

Revenue Recognition

Comprehensive Income (Loss)

Contract Balances

Research and Development Expenses

Stock-Based Compensation

Stock-based Compensation

Risk-free interest rate. The risk-free interest rate is based on the U.S. Treasury yield with a maturity equal to the expected term of the stock options in effect at the time of grant.

Dividend yield. The expected dividend is assumed to be zero as the Company has never paid dividends and has no current plan to pay any dividends on its common stock.

Income Taxes

Leases

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	67,310,838	66,228,046
Common stock, shares outstanding	67,310,838	66,228,046
Convertible Preferred Stock
Convertible Preferred stock, par value	$ 0.00001	$ 0.00001
Convertible Preferred stock, shares authorized	10,000,000	10,000,000
Convertible Preferred stock, shares issued	0	0
Convertible Preferred stock, shares outstanding	0	0

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Feb. 29, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	CTMX
Entity Registrant Name	CytomX Therapeutics, Inc.
Entity Central Index Key	0001501989
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity File Number	001-37587
Entity Tax Identification Number	27-3521219
Entity Address, Address Line One	151 Oyster Point Boulevard,
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	515-3185
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.00001 par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Public Float			$ 114.1
Entity Common Stock, Shares Outstanding		67,721,658
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement to be filed for its 2024 Annual Meeting of Stockholders are incorporated by reference into Part III hereof. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the end of the fiscal year covered by this Annual Report on Form 10-K.
Auditor Name	Ernst & Young LLP
Auditor Firm Id	42
Auditor Location	San Jose, California
Document Financial Statement Error Correction [Flag]	true
Document Financial Statement Restatement Recovery Analysis [Flag]	false

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Useful Lives of Property and Equipment (Details)	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	us-gaap:UsefulLifeShorterOfTermOfLeaseOrAssetUtilityMember
Machinery and equipment
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Computer equipment and software
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Furniture and fixtures
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	3 years

Accrued Liabilities

12 Months Ended

Dec. 31, 2023

Accrued Liabilities, Current [Abstract]

Accrued Liabilities

7. Accrued Liabilities

Accrued liabilities consisted of the following:


	December 31,
	2023		2022
	(in thousands)
Research and clinical expenses	$	8,435	$	13,089
Payroll and related expenses		8,160		8,060
Legal and professional expenses		690		1,413
Restructuring expenses		—		1,627
Other accrued expenses		314		261
Total	$	17,599	$	24,450

Collaboration and License Agreements - Regeneron Pharmaceuticals, Inc - Additional Information (Details) - USD ($) $ in Thousands		12 Months Ended
	Nov. 16, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized		$ 101,214	$ 53,163
Deferred revenue		212,315	301,326	$ 284,760
Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		24,400
Collaborative Arrangement \| Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	$ 30,000
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	30,000
Total transaction price	39,200
Research and development service fees	$ 9,200
Estimated research service period	4 years
Estimated research service termination month & year	2026-11
Deferred revenue		24,400	30,000
Amount due from customer		$ 1,100	$ 0
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	$ 800,000
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc \| Maximum \| Additional Contingent Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	$ 1,200,000

Intangible Asset (Tables)

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets


	December 31,
	2023			2022
	(in thousands)
PROBODY platform intangible asset	$	1,750		$	1,750
Less accumulated amortization		(1,021	)		(875	)
	$	729		$	875

Description of the Business

12 Months Ended

Dec. 31, 2023

Disclosure Text Block [Abstract]

Description of the Business

1. Description of the Business

CytomX Therapeutics, Inc. (the “Company”) is a clinical-stage, oncology-focused biopharmaceutical company developing potent biologics designed to be preferentially localized to tumors. The Company aims to build a commercial enterprise to maximize its impact on the treatment of cancer. The Company is advancing potential first-in-class and best-in-class antibody-based therapeutics created using its PROBODY® therapeutic technology platform that could meaningfully improve outcomes for cancer patients. Its proprietary and unique PROBODY technology platform is designed to enable “conditional activation” of antibody-based drugs in the tumor microenvironment while minimizing drug activity in healthy tissues and in circulation. The Company is located in South San Francisco, California and was incorporated in the state of Delaware in September 2010.

Intangible Asset

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Asset

6. Intangible Asset

The intangible asset is being amortized over the estimated lives of the patents which average 12 years. The amortization expense for each of the years ended December 31, 2023 and 2022 was $0.1 million.


	December 31,
	2023			2022
	(in thousands)
PROBODY platform intangible asset	$	1,750		$	1,750
Less accumulated amortization		(1,021	)		(875	)
	$	729		$	875

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following:


	December 31
	2023			2022
	(in thousands)
Laboratory equipment	$	14,119		$	14,002
Computer equipment and software		1,125			1,942
Furniture and fixtures		1,051			1,054
Leasehold improvements		1,983			1,742
Construction in progress		368			705
		18,646			19,445
Less: accumulated depreciation and amortization		(14,688	)		(14,373	)
	$	3,958		$	5,072

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2017
Income Tax Contingency [Line Items]
Deferred tax asset, net change in total valuation allowance increase during period	$ 5.1	$ 9.4	$ 22.7
Unrecognized tax benefits,income tax penalties and interest expense,		3.9
Unrecognized tax benefits would affect company's effective tax rate		2.3	$ 2.3
Penalties accrued		1.0
Interest accrued		0.6
Minimum
Income Tax Contingency [Line Items]
Percentage of change in ownership				50.00%
Federal
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 269.7
Operating loss carryforwards expiration year		2034
Operating loss carryforwards to expire if not utilized		$ 65.6
Operating loss carryforwards not subject to expiration		204.1
Federal \| Research and Development Tax Credits
Income Tax Contingency [Line Items]
Tax credit carry forwards		$ 24.4
Tax credit carryforward, expiration		2031
State
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 26.7
Operating loss carryforwards expiration year		2031
State \| Research and Development Tax Credits
Income Tax Contingency [Line Items]
Tax credit carry forwards		$ 13.7

Common Stock - Summary of Company's warrants (Details)	Dec. 31, 2023 $ / shares shares
Pre-Funded Warrant [Member]
Class of Warrant or Right [Line Items]
Number of Warrants Outstanding \| shares	14,423,077
Exercise price of warrants \| $ / shares	$ 0.00001
Tranche One Warrant [Member]
Class of Warrant or Right [Line Items]
Number of Warrants Outstanding \| shares	5,769,231
Exercise price of warrants \| $ / shares	$ 4.16
Tranche Two Warrant [Member]
Class of Warrant or Right [Line Items]
Number of Warrants Outstanding \| shares	5,769,231
Exercise price of warrants \| $ / shares	$ 6.24

Collaboration and License Agreements - Schedule of Revenue by Collaboration Partners (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 101,214	$ 53,163
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	3,688	18,563
Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	5,739	4,967
Astellas
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	24,453	20,491
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	49,300	9,142
Regeneron
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	7,194	0
Moderna
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 10,840	$ 0

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
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Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
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-Name Accounting Standards Codification
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-Paragraph 1A
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
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-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (SX 210.13-01(a)(5))
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-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Subparagraph (SX 210.13-02(a)(4)(i))
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-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479557/942-235-S99-1

+ Details

Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Accrued Liabilities, Current [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following:


	December 31,
	2023		2022
	(in thousands)
Research and clinical expenses	$	8,435	$	13,089
Payroll and related expenses		8,160		8,060
Legal and professional expenses		690		1,413
Restructuring expenses		—		1,627
Other accrued expenses		314		261
Total	$	17,599	$	24,450

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

The Company derives its income only from the United States. The components of the provision for income taxes are as follows (in thousands):


	Years Ended December 31,
	2023		2022
Current:
Federal	$	—	$	—
State		3,892		—
Total current		3,892		—
Deferred:
Federal		—		—
State		—		—
Total deferred		—		—
Provision for income taxes	$	3,892	$	—

A reconciliation of the Company’s effective tax rate to the statutory U.S. federal rate is as follows:


	Years Ended December 31,
	2023			2022
U.S. federal taxes at statutory rate		21.0	%		21.0	%
State tax, net of federal benefit		(478.7	)		1.7
Stock compensation		47.2			(2.1	)
Tax credits		242.7			2.4
Change in valuation allowance		283.2			(22.8	)
162(m) limitation		1.2			(0.2	)
Other		0.5			-
Total		117.1	%		0.0	%

The types of temporary differences that give rise to significant portions of the Company’s deferred income tax assets and liabilities are set out below (in thousands):


	Year Ended December 31,
	2023			2022
Net operating loss carryforwards	$	56,767		$	58,193
Research and development credits		22,149			24,700
Lease liability		3,501			3,802
Intangible assets		4,400			3,708
Deferred revenue		47,286			49,919
Accrued liabilities		2,425			1,504
Stock-based compensation		9,600			8,066
Sec 174 capitalized research and development costs		32,630			19,709
Other		55			31
Total gross deferred income tax assets		178,813			169,632
Less: valuation allowance		(175,454	)		(166,037	)
Deferred tax assets, net of valuation allowance		3,359			3,595
Fixed assets		(105	)		(43	)
Right-of-use assets		(3,061	)		(3,358	)
Prepaid expenses		(193	)		(194	)
Deferred tax liabilities		(3,359	)		(3,595	)
Net deferred income tax liabilities	$	—		$	—

The Company has established a valuation allowance against all of its net deferred tax assets. Management considered all available evidence, both positive and negative, including but not limited to our historical operating results, income or loss in recent periods, cumulative losses in recent years, forecasted earnings, future taxable income, and significant risk and uncertainty related to forecasts, and concluded the deferred tax assets are not more likely than not to be realized. The net change in the total valuation allowance for the years ended December 31, 2023 and 2022 was an increase of $9.4 million and $22.7 million, respectively.

The Company had net operating loss carryforwards for federal and state income tax purposes of approximately $269.7 million and $26.7 million, respectively, as of December 31, 2023, available to reduce future taxable income. Of the federal net operating loss carryforwards, $65.6 million will begin to expire in 2034, if not utilized and $204.1 million will carryforward indefinitely. The state net operating loss carryforwards will begin to expire in 2031, if not utilized.

The Company also has federal and state research and development tax credits carryforwards of $24.4 million and $13.7 million, respectively, as of December 31, 2023 available to reduce future income taxes. The federal research and development tax credits will begin to expire in 2031 if not utilized. The state research and development tax credits will carryforward indefinitely.

Internal Revenue Code section 382 (“IRC Section 382”) places a limitation (the “Section 382 Limitation”) on the amount of taxable income that can be offset by net operating loss (“NOL”) carryforwards after a change in control (generally greater than 50% change in ownership) of a loss corporation. California has similar rules. The Company has performed an IRC Section 382 analysis and determined there was an ownership change in 2017 that resulted in 382 limitations. When an ownership change occurs, IRC Section 382 limits the use of NOLs and credits in subsequent periods based on the annual 382 limitations. The annual 382 limitations may limit the full use of available tax attributes in one year but the identified ownership changes may not result in expiration of tax attributes for use prior to expiration of their respective carryforward periods. Accordingly, none of the tax attributes have been reduced but limited the full use in 2018. The Company has determined that, while an ownership change has occurred, the applicable limits would not impair the value or anticipated use of the Company’s federal and state net operating losses. Although realization is not assured, management believes it is more likely than not that any limitation under IRC Section 382 will not impair the realizability of the deferred income tax assets related to federal and state net operating loss carryforwards. The Company updated its Section 382 analysis through the year ended December 31, 2023 and concluded no ownership changes occurred in current year which would result in a reduction of its net operating loss or in its research and development credits expiring unused. If additional ownership change occurs, the utilization of net operating loss and credit carryforwards could be significantly reduced.

A reconciliation of the beginning and ending unrecognized tax benefit amount is as follows (in thousands):


	Year Ended December 31,
	2023		2022
Balance at the beginning of the year	$	9,269	$	7,780
Additions based on tax positions related to current year		527		1,391
Adjustment based on tax positions related to prior years		9,581		98
Balance at end of the year	$	19,377	$	9,269

Of the unrecognized tax benefits as of December 31, 2023 and 2022, approximately $2.3 million would affect the Company’s effective tax rate if recognized. Penalties and interest of $1.0 million and $0.6 million, respectively, have been accrued for the year ended December 31, 2023.

The Company files income taxes in the U.S. federal jurisdiction, the state of California and various other U.S. states. The state of California contested the Company’s tax position on revenue apportionment for upfront and milestone payments resulting from the Company’s collaboration and licensing agreements for the years 2017 and 2018. In September 2023, the Company received Notice of Proposed Assessment (“NOPA”) from the Franchise Tax Board. The Company recorded an uncertain tax position of $3.9 million in long term liabilities for the proposed tax assessment, penalties and interest through December 31, 2023. Additional utilization of carryforward attributes and indirect federal tax effects of the assessment would result in a reduction in deferred tax assets of $5.1 million. The Company filed a protest to contest the proposed assessment in November 2023. Due to the ongoing nature of the examination and discussions with the state of California, the Company is unable to estimate a date by which this matter will be resolved.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Name Accounting Standards Codification
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-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Collaboration and License Agreements - AbbVie Ireland Unlimited Company - Additional Information (Details) $ in Thousands	1 Months Ended					12 Months Ended
	Jan. 31, 2022 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	May 31, 2018 USD ($)	Apr. 30, 2016 USD ($) AccountingUnit Target Agreement	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2017 Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized						$ 101,214	$ 53,163
Type of Revenue [Extensible List]						us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Deferred revenue						$ 212,315	$ 301,326		$ 284,760
AbbVie Ireland Unlimited Company
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized		$ 26,600		$ 9,900
AbbVie Ireland Unlimited Company \| ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					$ 30,000
Milestone payment received					14,000
Total transaction price					39,800
Estimated sublicense fees					$ 4,200
Number of accounting units \| AccountingUnit					2
AbbVie Ireland Unlimited Company \| Second Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Change in estimated collaboration amount	$ 4,400
AbbVie Ireland Unlimited Company \| Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of collaboration agreements \| Agreement					2
Percentage of net profits or net losses related to development and commercialization costs					35.00%
AbbVie Ireland Unlimited Company \| CD71 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments received						100,000
Total transaction price					$ 29,800
Milestone payment received		$ 40,000		21,000
Deferred revenue							4,000	$ 4,000
AbbVie Ireland Unlimited Company \| CD71 Agreement \| Transferred over Time
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Type of Revenue [Extensible List]		us-gaap:LicenseAndServiceMember
AbbVie Ireland Unlimited Company \| CD71 Agreement \| ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					20,000
Estimated sublicense fees					4,200
Milestone payment received					14,000
AbbVie Ireland Unlimited Company \| Seattle Genetics Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense fees paid				$ 4,000
AbbVie Ireland Unlimited Company \| Seattle Genetics Agreement \| ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense fees paid					1,000
AbbVie Ireland Unlimited Company \| Discovery Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					10,000
Number of targets selected \| Target										1
Total transaction price					10,000
Deferred revenue						$ 0	$ 0
AbbVie Ireland Unlimited Company \| Discovery Agreement \| ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					10,000
AbbVie Ireland Unlimited Company \| Discovery Agreement \| Second Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments received			$ 10,000		$ 10,000
AbbVie Ireland Unlimited Company \| Discovery Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets \| Target					2

Collaboration and License Agreements - Astellas Pharma Inc - Additional Information (Details) $ in Thousands		1 Months Ended	3 Months Ended
	Mar. 23, 2020 USD ($) Target	Jan. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				$ 212,315	$ 301,326	$ 284,760
Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				31,000
Collaboration and License Agreement \| Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets selected \| Target	1
Number of additional collaboration target \| Target	3
Upfront payment received	$ 80,000
Total transaction price	103,200
Research and development service fees	$ 23,200
Milestone payments received		$ 5,000	$ 5,000
Deferred revenue				31,000	44,500
Amount due from customer				$ 2,200	$ 1,000
Collaboration and License Agreement \| Astellas Pharma Inc. \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets \| Target	4
Right to expand the number of additional collaboration target \| Target	5
Contingent milestone payments receivable	$ 1,600,000
Collaboration and License Agreement \| Astellas Pharma Inc. \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Right to expand the number of additional collaboration target \| Target	3

Collaboration and License Agreements (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Revenue by Collaboration Partners

The following table summarizes the revenue by collaboration partner:


	Year Ended December 31,
	2023		2022
	(in thousands)
AbbVie	$	3,688	$	18,563
Amgen		5,739		4,967
Astellas		24,453		20,491
Bristol Myers Squibb		49,300		9,142
Regeneron		7,194		—
Moderna		10,840		—
Total revenue	$	101,214	$	53,163

Summary of Contract Liabilities

The following table presents changes in the Company’s total contract liabilities for the years ended in December 31, 2023 and 2022 (in thousands):


	Deferred Revenue
	(in thousands)
Balance at 12/31/2021		284,760
Additions		69,555
Revenue Recognized		(52,989	)
Balance at 12/31/2022		301,326
Additions		6,438
Revenue Recognized		(95,449	)
Balance at 12/31/2023		212,315

Fair Value Measurements and Investments - Schedule of Investments Subject to Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 17,171	$ 193,650
Aggregate Fair Value	175,364	95,574
Gross Unrealized Holding Gains	95	10
Amortized Cost	175,269	95,564
Level I \| Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	17,109	64,706
Level I \| Restricted cash (money market funds)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted cash	917	917
Level 2 \| U.S.Treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments, Amortized Cost	157,243	29,941
Investments, Gross Unrealized Gains	95	10
Investments, Aggregate Fair Value	$ 157,338	$ 29,951

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Supplemental Information Related to Leases

Supplemental information related to leases are as follows:


	Year Ended
	December 31, 2023			December 31, 2022
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$	5,420		$	5,273

	December 31, 2023			December 31, 2022
	(in thousands)
Weighted-average remaining lease term (in years)
Operating lease	2.75				3.75
Weighted-average discount rate
Operating lease		8.25	%		8.25	%

Schedule of Maturity of Operating Lease Liabilities


	December 31, 2023
	(in thousands)
Maturity of operating lease liabilities
2024		5,572
2025		5,729
2026		4,387
Total lease payments		15,688
Less imputed interest		(1,714	)
Present value of lease liabilities		13,974

Schedule Of Subleasing


	December 31, 2023
	(in thousands)
Future sublease income payments
2024		1,333
2025		1,379
2026		1,067
Total sublease income payments	$	3,779

Collaboration and License Agreements - Amgen, Inc - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Sep. 29, 2017 USD ($) Target	Oct. 31, 2017 USD ($) $ / shares shares	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 212,315	$ 301,326	$ 284,760
Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					12,800
Collaboration and License Agreement \| Amgen Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received	$ 40,000	$ 40,000
Common stock, shares issuable under agreement \| shares		1,156,069
Common stock, shares issuable under agreement, price per share \| $ / shares		$ 17.3
Common stock, value of shares issued in connection with agreement		$ 20,000
Number of targets selected \| Target	1
Number of additional collaboration target \| Target	2
Total transaction price	$ 51,200
Portion of transaction price allocated to premium on sale of common stock	500
Estimated fair value of products	10,700
Collaboration and License Agreement \| Amgen Inc \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments payable	203,000
Collaboration and License Agreement \| Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total transaction price	46,400
Estimated research service period			7 years	8 years
Deferred revenue					$ 12,800	18,000
Collaboration and License Agreement \| Amgen Inc \| EGFR Products \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable	$ 460,000
Percentage share of profit and losses	50.00%
Collaboration and License Agreement \| Amgen Inc \| Amgen Products \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable	$ 950,000
Number of targets \| Target	3
Collaboration and License Agreement \| Amgen Inc \| Amgen Other Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total transaction price	$ 4,800
Estimated research service period	6 years
Revenue recognition upon performance obligation	$ 4,800
Deferred revenue						$ 600
Sublicense Agreement \| Amgen Inc \| Maximum \| UC Regents
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense payment percentage	7.50%

Net Loss Per Share - Summary of Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net loss	$ (569)	$ (99,317)
Shares used to compute net loss per share, basic and diluted
Weighted-average common shares outstanding	66,655,971	65,739,844
Weighted-average pre-funded warrants	7,152,266
Shares used to compute net loss per share, Basic	73,808,237	65,739,844
Shares used to compute net loss per share, Diluted	73,808,237	65,739,844
Net loss per share, basic and diluted
Basic	$ (0.01)	$ (1.51)
Diluted	$ (0.01)	$ (1.51)

Stock-based Compensation - Schedule of Activities Under Company's Stock Option Plans (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Number of Options
Balances, beginning of the period \| shares	13,289,838
Options granted \| shares	1,938,573
Options exercised \| shares	(16,535)
Options cancelled \| shares	(2,262,264)
Balances, end of the period \| shares	12,949,612
Options Exercisable, end of the period \| shares	8,672,013
Options Outstanding, Weighted-Average Exercise Price Per Share
Balances, beginning of the period \| $ / shares	$ 7.67
Options granted \| $ / shares	2.2
Options exercised \| $ / shares	1.57
Options cancelled \| $ / shares	5.95
Balances, end of the period \| $ / shares	7.16
Options Exercisable, end of the period \| $ / shares	$ 9.03
Options Outstanding, Weighted- Average Remaining Contractual Life (years)
Balances, end of the period	6 years 6 months 3 days
Options Exercisable, end of the period	5 years 6 months 7 days
Options Outstanding, Aggregate Intrinsic Value
Options exercised \| $	$ 5,000
Balances at December 31, 2022 \| $	70,500
Options Exercisable-December 31, 2022 \| $	$ 4,700

Defined Contribution Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Company contributions to defined contribution plan	$ 0.5	$ 0.9