CytomX reports results from interim Phase 1 data for CX-2051

CytomX Therapeutics (CTMX) announced positive interim Phase 1 data for its EpCAM PROBODY ADC candidate, CX-2051, in advanced, late-line CRC. The data are as of an April 7th 2025 data cutoff from the ongoing CTMX-2051-101 Phase 1 study. McCarthy added, “Importantly, we believe these results validate EpCAM as an oncology target and unlock a broad development opportunity for CX-2051 in CRC and potentially many other cancer types where EpCAM is expressed. We are excited to rapidly advance CX-2051 for the benefit of CRC patients and to explore the full potential of this novel ADC.” The CTMX-2051-101 study was initiated in April 2024 with dose escalation proceeding through seven dose levels as of April 2025. 25 advanced metastatic CRC patients were treated with CX-2051 across dose levels 1 through 5 as of the April 7, 2025 data cutoff. CX-2051 was administered on a once every three week schedule. The 2.4 mg/kg and 4.8 mg/kg doses were single patient dose escalation cohorts not anticipated to be therapeutically active. At the 7.2 mg/kg, 8.6 mg/kg, and 10 mg/kg doses, 23 patients were treated in total, 18 of whom were efficacy evaluable, having had at least one post-baseline tumor assessment as of the data cutoff. 28% of patients achieved confirmed partial RECIST v. 1.1 responses. Overall response rates for currently approved therapies in 3rd line or later CRC are in the low to mid-single digit percentages. At the 10 mg/kg dose, 3 of 7 evaluable patients achieved confirmed partial responses. The Disease Control Rate2 was 94% across the three dose groups . Median progression free survival was 5.8 months as of the data cutoff. 10 of 18 patients remained on study treatment as of the data of cutoff.