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

• The trial, started in April 2024, involved 93 advanced late-line metastatic colorectal cancer patients (CRC).
•  Across all dose levels, 88% of patients showed signs of disease control.
• The company plans to engage with the FDA later this year on a potential registrational trial for the therapy.

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 across higher dose levels. 

Following the results, CytomX Therapeutics stock traded over 54% in Monday’s premarket. On Stocktwits, retail sentiment around the stock changed to ‘extremely bullish’ from ‘bullish’ territory the previous day. Message volume shifted to ‘extremely high’ from ‘high’ levels in 24 hours. 

Promising Early Efficacy Signals In Phase 1 Study 

The CTMX-2051-101 trial, which began in April 2024, included 93 patients with advanced colorectal cancer who had already received multiple treatments. Out of these 56 could be assessed for how well the treatment worked.

Participants received increasing doses of 7.2 mg/kg, 8.6 mg/kg, or 10 mg/kg every three weeks. Treatment responses improved as the dose increased. 6% of patients responded at 7.2 mg/kg, 20% at 8.6 mg/kg, and 32% at 10 mg/kg. Overall, 88% of patients across all doses experienced some level of disease control.

CytomX plans to present additional Phase 1 data at medical meetings later in 2026. The company will engage with the FDA mid-year to discuss registrational trial design for Varseta-M monotherapy in advanced CRC.

Financial Performance: Revenue Declines As Collaboration Milestones End

Revenue fell 44.8% year-on-year (YoY) to $76.2 million from $138.1 million in 2025, largely due to the completion of Bristol Myers Squibb collaboration obligations and slower recognition from Moderna, Astellas, and Regeneron partnerships. 

Operating expenses dropped 12.8% YoY to $98.6 million, with R&D costs decreasing to $68.7 million following restructuring and strategic pipeline focus. CytomX closed 2025 with $137.1 million in cash, cash equivalents, and investments, providing a runway into Q2 2027. 

CTMX stock has gained over 642% in the last 12 months.

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