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<!-- Created: Thu Apr 30 20:15:25 UTC 2026 -->
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="ctmx_ChrisOgdenMember_lbl" xml:lang="en-US">Chris Ogden [Member]</label>
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    <loc xlink:type="locator" xlink:label="ctmx_SeanAMcCarthyDPhilMember" xlink:href="ctmx-20260617.xsd#ctmx_SeanAMcCarthyDPhilMember"/>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="ctmx_SeanAMcCarthyDPhilMember_lbl" xml:lang="en-US">Sean A. McCarthy, D. Phil [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_lbl" xml:lang="en-US">Net Income (Loss) Available to Common Stockholders, Basic</label>
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