Why CTMX Stock Is Soaring 54% Pre-Market Today?

CytomX Therapeutics reported promising Phase 1 expansion results for Varseta-M in late-line metastatic colorectal cancer.
In this photo illustration, the CytomX Therapeutics logo is displayed on the screen of a tablet.
In this photo illustration, the CytomX Therapeutics logo is displayed on the screen of a tablet. (Photo Illustration by Sheldon Cooper/SOPA Images/LightRocket via Getty Images)
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Shivani Kumaresan·Stocktwits
Published Mar 16, 2026   |   7:45 AM EDT
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CytomX Therapeutics, Inc. (CTMX) on Monday announced encouraging early results from its Phase 1 expansion study of varsetatug masetecan (Varseta-M) in patients with late-line metastatic colorectal cancer (CRC). 

The data, as of January 16, indicated the antibody-drug conjugate is showing meaningful response rates at optimized doses.

The CTMX-2051-101 trial, launched in April 2024, enrolled 93 heavily pretreated metastatic CRC patients, with 56 evaluable for efficacy across expansion doses of 7.2 mg/kg, 8.6 mg/kg, and 10 mg/kg administered every three weeks. Confirmed response rates increased with dose; 6% at 7.2 mg/kg, 20% at 8.6 mg/kg, and 32% at 10 mg/kg. 

Following the results, CytomX Therapeutics stock traded over 54% in Monday’s premarket. 

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