Pfizer and Olema Collaborate on New Trial for Metastatic Breast Cancer Treatment

Pfizer Inc. (PFE) has announced a new trial collaboration with Olema Pharmaceuticals for metastatic breast cancer. The study will test the safety and effectiveness of combining Olema's drug Palazestrant with Pfizer's investigational drug Atirmociclib. Pfizer will supply Atirmociclib, while Olema will lead the trial. Both companies will jointly own data and inventions from the study, but Olema retains commercial rights for Palazestrant. This is Olema's second trial with Pfizer, following an earlier study with Pfizer's palbociclib.

San Francisco, September 02, 2025 — Pfizer Inc. (PFE) and Olema Pharmaceuticals, Inc. (OLMA) have announced a new clinical trial collaboration to evaluate the safety and efficacy of combining Olema's drug Palazestrant with Pfizer's investigational drug Atirmociclib in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) metastatic breast cancer. The study, a Phase 1b/2 trial, is expected to begin in the second half of 2025 and will involve approximately 35 patients.

The collaboration follows an earlier agreement between the two companies in November 2020, where they evaluated Palazestrant in combination with Pfizer's palbociclib (IBRANCE®) in patients with recurrent, locally advanced or metastatic ER+/HER2- breast cancer.

Under the terms of the new agreement, Pfizer will supply Atirmociclib for use in the Phase 1b/2 study, while Olema will lead the conduct of the study. All clinical data and inventions resulting from the study will be jointly owned by both companies, with Olema retaining full global commercial and marketing rights to Palazestrant.

Sean P. Bohen, M.D., Ph.D., President and Chief Executive Officer of Olema Oncology, expressed enthusiasm about the potential of the combination therapy. "We are excited to assess this combination in the clinic as we seek to establish Palazestrant as a potential backbone endocrine therapy for metastatic breast cancer," he said. "Based on the promising profiles of Palazestrant and Atirmociclib to date, we look forward to evaluating the potential of this novel combination and, if successful, advancing to a pivotal trial in the frontline setting."

This latest collaboration underscores the ongoing efforts of both companies to transform the treatment paradigm for metastatic breast cancer. Olema's first pivotal study of Palazestrant, OPERA-01, is currently underway, and the company's OPERA-02 ribociclib combination trial in frontline metastatic breast cancer is anticipated to initiate this quarter.

[1] https://ir.olema.com/news-releases/news-release-details/olema-oncology-announces-new-clinical-trial-agreement-pfizer
[2] https://www.ainvest.com/news/olema-pharmaceuticals-shares-surge-20-49-intraday-announcing-clinical-trial-collaboration-pfizer-breast-cancer-treatment-2509/
[3] https://www.biospace.com/press-releases/olema-oncology-announces-new-clinical-trial-agreement-with-pfizer-to-combine-palazestrant-with-atirmociclib-in-er-her2-metastatic-breast-cancer