CytomX Reports Positive Interim Results from Phase 1 Study of CX-2051 in Advanced Colorectal Cancer

CytomX Therapeutics, a leader in the development of conditionally activated biologics, has released promising interim results from its ongoing Phase 1 trial of CX-2051, a novel PROBODY® antibody-drug conjugate (ADC) designed for the treatment of advanced, late-line colorectal cancer (CRC). The announcement was made on May 12, 2025, highlighting significant findings as of an April 7, 2025 data cutoff.

CX-2051 targets the epithelial cell adhesion molecule (EpCAM), a protein highly expressed in many cancers but challenging to target due to its presence in normal tissues. However, CytomX's innovative masking technology appears to have overcome this historical challenge, showing potential for improved therapeutic outcomes in CRC.

The interim results indicate a confirmed response rate of 28% in the study's patient population, with doses ranging from 7.2 mg/kg to 10 mg/kg administered every three weeks. Notably, at the upper expansion dose of 10 mg/kg, 43% of evaluable patients demonstrated confirmed responses. The median progression-free survival time observed was 5.8 months, suggesting that CX-2051 provides a valuable clinical benefit for patients with late-stage CRC, a disease known for its treatment difficulties and high unmet medical needs.

Safety data from the study shows that CX-2051 is generally well tolerated, with no dose-limiting toxicities reported as of the data cutoff. This encouraging safety profile complements the drug's efficacy, highlighting the potential of CytomX's PROBODY® platform to safely target tumor antigens like EpCAM.

CytomX's CEO, Sean McCarthy, expressed optimism about these findings, underscoring that the results not only validate EpCAM as a viable target in oncology but also open avenues for further development of CX-2051 in CRC and possibly other cancers expressing EpCAM. This progress underscores the potential of CX-2051 to meet significant medical needs in oncology, particularly for patients with CRC who have limited treatment options.

Looking forward, CytomX is planning to initiate a Phase 2 study in the first half of 2026. This next phase will be crucial in further exploring the therapeutic potential of CX-2051, building on the foundation of the positive Phase 1 results.

The company also hosted an investor conference call on May 12, 2025, to discuss these findings and future plans for CX-2051. The robust pipeline of CytomX, which includes other promising candidates like CX-801, continues to advance, showcasing the potential of their PROBODY® platform across various cancer treatments.

CX-2051 was developed in collaboration with ImmunoGen, part of AbbVie, and represents a significant advancement in the therapeutic targeting of EpCAM, potentially transforming the treatment landscape for epithelial cancers. As CytomX continues to leverage its innovative technology to create more effective cancer therapies, the results from CX-2051 offer hope for improved outcomes for patients battling difficult-to-treat tumors.