Atirmociclib — Investigational Agent
Other · Phase 3 · Pfizer
Mechanism of Action
Atirmociclib is an oral, highly selective inhibitor of CDK4, sparing CDK6. First-generation CDK4/6 inhibitors (palbociclib, ribociclib, abemaciclib) inhibit both kinases, and CDK6 inhibition contributes to neutropenia and limits target coverage. By selectively targeting CDK4, atirmociclib blocks phosphorylation of the retinoblastoma protein and arrests HR+ breast cancer cells in G1, potentially with a wider therapeutic window and less hematologic toxicity, permitting more complete and sustained CDK4 inhibition. It is being developed in combination with endocrine therapy (fulvestrant,…
Investigational Indications
- HR+/HER2- advanced or metastatic breast cancer
- HR+/HER2- breast cancer after prior CDK4/6 inhibitor progression
- First-line HR+/HER2- metastatic breast cancer