CytomX's Breast Cancer Candidate Meets Primary Goal Of Objective Response Rate

CytomX Therapeutics Inc's CTMX Phase 2 study of praluzatamab ravtansine in hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 (HER2)-non-amplified breast cancer (Arm A) met its primary efficacy endpoint of confirmed objective response rate (ORR) of more than 10%.
As of the data cutoff on May 13, 47 patients unselected for CD166 expression with advanced HR+/HER2-non-amplified breast cancer were evaluable for the primary efficacy endpoint.
The ORR was 15% in 47 evaluable patients. The clinical benefit rate at 24 weeks was 40%, and the median progression-free survival was 2.6 months.
All patients in Arm A were treated at the initial Phase 2 starting dose of 7 mg/kg administered every three weeks. Arm B did not pass the protocol-defined futility boundary (ORR was less than 10%) in patients with advanced triple-negative breast cancer (TNBC).
Enrollment into Arms B and C will be discontinued.
The safety profile of praluzatamab ravtansine in Arm A was generally consistent with toxicities observed in Phase 1. 30% of patients discontinued treatment for an adverse event.
Biomarker analysis is ongoing. CytomX intends to submit data from this study for presentation at a medical conference in 2H of 2022.
Price Action: CTMX shares are down 18.8% at $1.60 during the premarket session on the last check Thursday.