Olema Pharmaceuticals, Inc. has announced a new clinical trial collaboration and supply agreement with Pfizer Inc. to evaluate a combination therapy in metastatic breast cancer. The Phase 1b/2 study will investigate the safety and combinability of palazestrant with atirmociclib, Pfizer's investigational CDK4 inhibitor, in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) metastatic breast cancer. The study is set to include approximately 35 patients, with initiation expected in the second half of 2025. Results from this study will inform a potential pivotal Phase 3 trial for the treatment in the frontline metastatic breast cancer setting. Under the agreement, Pfizer will provide atirmociclib, while Olema will lead the study's conduct. All resulting clinical data and inventions will be jointly owned, with Olema retaining commercial and marketing rights to palazestrant. Results have not yet been presented.