CytomX Therapeutics Inc (NASDAQ: CTMX) Announces Phase 2 Findings For Praluzatamab Ravtansine in Breast Cancer

CytomX Therapeutics Inc (NASDAQ: CTMX) has announced that its second phase study of praluzatamab rvtansine in individuals with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 (HER2)-non-amplified breast cancer attained its primary efficacy goal of confirmed objective response rate (ORR) of more than 10% by central radiology review. The product candidate is a DM4-conjugated, conditionally activated antibody-drug conjugate that targets CD166 wholly-owned by CytomX.

Study to evaluate 47 patients with advanced HER2-non-amplified cancer 

Around 47 patients with advanced HR+/HER2-non-amplified breast cancer who were not chosen for CD166 expression at the time of the dataset cutoff on May 13, 2022, might be evaluated for the primary effectiveness objective. The central radiology review’s ORR was 15%. The clinical benefit rate after 24 weeks by the investigator (CBR24) was 40%; the median progression-free survival was 2.6 months. According to the protocol, CBR24 is defined as any reaction (unconfirmed or confirmed) or steady disease for 24 weeks.

All participants in Arm A received treatment every three weeks at the 7 mg/kg Phase 2 dose range. Participation in Arms B and C will end as a result of Arm B failing to cross the protocol-defined futility limit (ORR was below 10%) in participants with advanced triple-negative breast cancer (TNBC).

Results support single-agent activity in HER2+ breast cancer. 

CEO and Chairman of Cytomx Sean McCarthy said, “These results from our Phase 2 evaluation of praluzatamab ravtansine support single-agent activity of this novel drug candidate in hormone receptor-positive breast cancer where significant unmet need remains. However, we do not believe the median progression-free survival at 7 mg/kg supports further evaluation at this dose. While we are encouraged by the emerging safety profile of 6 mg/kg, we do not plan to further advance this program alone given current financial market conditions and will be seeking a partnership.”

Lead investigator  and Ballve Lantero, Professor of Oncology Kathy Miller, said, “In this Phase 2 study, praluzatamab ravtansine showed single-agent activity in an unselected population of patients with advanced HR+/HER2-non-amplified breast cancer; additional clinical studies at 6 mg/kg are warranted.”