Evorpacept Plus Zanidatamab Yields 100% ORR, 22.1-Month PFS in HER2+ mBC
ALX Oncology reported a 100% objective response rate and 22.1-month median progression-free survival in high CD47-expressing HER2-positive metastatic breast cancer patients treated with evorpacept plus zanidatamab. Patients with low CD47 expression had a 25% response rate and 3.4-month PFS, while high-expression tumors saw a 20.2-month median duration of response.
1. Phase 1b/2 Trial Results
ALX Oncology presented exploratory data from a Phase 1b/2 trial combining its CD47 inhibitor evorpacept with zanidatamab in heavily pre-treated HER2-positive metastatic breast cancer patients, showing an overall confirmed ORR of 33% (8/24) and median PFS of 3.6 months across all participants.
2. Biomarker-Driven Response
Among 10 ccHER2-positive patients evaluable for CD47 expression, those with high CD47 levels (>20%) achieved a 100% ORR (5/5), median PFS of 22.1 months and median duration of response of 20.2 months versus 25% ORR and 3.4-month PFS in the low-expression group.
3. Trial Design and Patient Profile
The open-label, multi-center trial enrolled patients with a median of five prior HER2-targeted therapies, all post-ENHERTU, administering zanidatamab plus evorpacept at 20 mg/kg or 30 mg/kg, with 17 of 24 tumor samples evaluable for CD47 biomarker analysis.
4. Next Steps and Webcast Details
ALX Oncology will host a webcast on May 8 to review Q1 2026 financial results and discuss these trial findings; the company is advancing a biomarker-driven ASPEN-09-Breast Phase 2 trial of evorpacept plus trastuzumab and chemotherapy to validate patient selection and response durability.