South San Francisco, California – August 27, 2026
CytomX Therapeutics announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation (FTD) to Varsetatug masetecan (Varseta-M; CX-2051) for patients with relapsed/refractory metastatic colorectal cancer (R/R mCRC). Varseta-M is a potential first-in-class antibody-drug conjugate (ADC) targeting epithelial cell adhesion molecule (EpCAM) and carrying a topoisomerase-1 inhibitor payload. For cGxP.wire, the key development is the FDA Fast Track designation and planned progression of Varseta-M toward a potential registrational study in R/R mCRC in the first half of 2027. The designation follows previously reported encouraging Phase 1 data and is intended to facilitate development and potentially expedite regulatory review for the serious condition with unmet medical need.
CytomX Receives FDA Fast Track Designation for Varseta-M
The FDA granted Fast Track Designation to Varseta-M for the treatment of patients with relapsed/refractory metastatic colorectal cancer, providing a regulatory development milestone for CytomX’s lead oncology program. Fast Track is designed to facilitate the development and review of medicines addressing serious conditions where there is an unmet medical need. CytomX said the designation follows encouraging Phase 1 clinical data previously reported for Varseta-M and supports the company’s plans to advance the program toward a potential first registrational trial. The company currently expects to initiate a potential Varseta-M monotherapy registrational study in the first half of 2027. While Fast Track can provide opportunities for increased interaction with the FDA and potentially more efficient development and review, the designation does not establish efficacy or guarantee future approval. Additional clinical data will be required to
Varseta-M Targets EpCAM With a Topoisomerase-1 Payload
Varseta-M is a masked, conditionally activated ADC directed toward EpCAM, a tumor-associated antigen that is highly expressed in colorectal cancer but has historically presented challenges for drug development because it is also expressed on normal tissues. CytomX designed Varseta-M using its PROBODY® therapeutic platform, which is intended to keep the biologic masked in healthy tissues and enable activation within the tumor microenvironment. The ADC combines EpCAM targeting with a topoisomerase-1 inhibitor payload, creating a targeted approach intended to deliver cytotoxic activity preferentially to tumor tissue. The company believes this conditional activation strategy could potentially improve the therapeutic window of EpCAM-directed treatment. However, Varseta-M remains an investigational clinical-stage therapy, and its ability to translate the platform’s intended tumor-selective activation into meaningful clinical outcomes will need to be demonstrated in larger studies.
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CytomX Prepares Varseta-M for Registrational Development
Following the Fast Track designation, CytomX is preparing Varseta-M for a potential registrational monotherapy study in R/R mCRC targeted to begin in 1H 2027. The program represents one of the company’s key clinical-stage assets and is initially focused on metastatic colorectal cancer, where treatment options remain limited for patients who have progressed after multiple lines of therapy. Varseta-M was discovered through a collaboration with ImmunoGen, now part of AbbVie, and is part of CytomX’s broader pipeline of conditionally activated biologics. The company is also developing CX-801, a masked interferon alpha-2b PROBODY® cytokine initially being evaluated in metastatic melanoma. CytomX has established strategic collaborations with companies including Amgen, Regeneron and Moderna. The next major catalyst for Varseta-M will be the transition into its planned registrational study, but Fast Track designation alone should not be interpreted as evidence that the therapy will succeed in Phase 2/3 development or receive FDA approval.
Source:CytomX Therapeutics,,press relese
