Multinational phase 2a study of zanidatamab plus palbociclib and fulvestrant for previously treated HR-positive, HER2-positive metastatic breast cancer

Zanidatamab is a HER2-targeted bispecific anitbody. A multinational phase 2a trial evaluated the combination of zanidatamab plus palbociclib and fulvestrant for previously treated HR-positive, HER2-positive metastatic breast cancer. All patients had at least one treatment-related adverse event of any grade, and 67% of patients had grade 3 or 4 TRAEs; there were no grade 5 TRAEs. Progression-free survival rate at 6 months (primary end point) was 66.7% (95% CI 52.1-79.2). The authors conclude that the chemotherapy-free regimen of zanidatamab plus palbociclib and fulvestrant was generally safe and showed promising antitumor activity for previously treated HR+/HER2+ mBC.