CytomX Cancer Drug Shows 32% Response Rate in Trial

Cancer Drug Achieves 32% Response Rate in Phase 1

CytomX Therapeutics announced on March 16, 2026, that its lead drug candidate, varsetatug masetecan (Varseta-M), delivered positive results in a Phase 1 study for patients with advanced colorectal cancer (CRC). The data, from a January 16, 2026 cutoff, showed a confirmed overall response rate of 32% in the patient cohort receiving a 10 mg/kg dose. This group also experienced an estimated progression-free survival of 7.1 months. A lower dose of 8.6 mg/kg yielded a 20% response rate.

These results are significant for a patient population with few therapeutic alternatives. The treatment also demonstrated a manageable safety profile, with a Grade 3 diarrhea rate of 10% in ongoing dose optimization cohorts. Varseta-M is an antibody-drug conjugate (ADC) designed to target EpCAM, a protein highly expressed on tumor cells, which has historically been difficult to target without affecting healthy tissue.

These exciting clinical data demonstrate that Varseta-M can drive consistent and durable responses with a manageable tolerability profile in patients with heavily pretreated CRC, supporting its promise as a potential new treatment option for advanced CRC.

— Dr. Kimmie Ng, Associate Chief, Division of Gastrointestinal Oncology at Dana-Farber Cancer Institute.

Results Follow $17.4M Full-Year 2025 Loss

The encouraging clinical update arrived alongside the company's 2025 financial results, which fell short of analyst expectations. CytomX reported a fourth-quarter loss of $26.5 million, or 22 cents per share, wider than the 8-cent loss forecasted by analysts surveyed by Zacks. Quarterly revenue was just $663,000, missing the consensus estimate of $7.4 million.

For the full year ended December 31, 2025, the company posted a net loss of $17.4 million on revenue of $76.2 million. Despite the loss, CytomX maintains a solid financial position, ending the year with $137.1 million in cash, cash equivalents, and investments. The company projects this cash runway is sufficient to fund operations into the second quarter of 2027, providing critical capital to advance its clinical programs.

CytomX Eyes FDA Talks in Mid-2026 for Path to Market

With the positive Phase 1 data in hand, CytomX has defined a clear strategic priority for 2026: engaging with the U.S. Food and Drug Administration (FDA) to finalize a registrational trial design for Varseta-M in late-line CRC. This step is crucial for moving the drug from clinical development toward a potential market approval. The company is targeting these FDA interactions for mid-year.

In parallel, CytomX is working to expand the drug's potential application. A Phase 1 study combining Varseta-M with bevacizumab has already started, and another study combining it with chemotherapy is planned to begin by the end of 2026. These efforts reflect a broader strategy to position Varseta-M for use in earlier lines of treatment and build CytomX into a commercial-stage company.