trilaciclib + trastuzumab + pertuzumab

This is a combination regimen of three drugs: - **Trilaciclib** is an intravenous small molecule cyclin-dependent kinase 4/6 (CDK4/6) inhibitor developed to protect hematopoietic stem and progenitor cells as well as immune cells from chemotherapy-induced damage by inducing transient cell cycle arrest. It also has immunomodulatory effects that may enhance antitumor immunity[7]. - **Trastuzumab** is a recombinant humanized monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2), inhibiting HER2-mediated signaling and proliferation in HER2-overexpressing cancer cells[5]. - **Pertuzumab** is a monoclonal antibody that binds to a different epitope on HER2 than trastuzumab, blocking dimerization with other HER family receptors (especially HER3), thereby inhibiting downstream signaling pathways involved in cell growth and survival[5]. This combination would be considered investigational; while dual anti-HER2 therapy with trastuzumab plus pertuzumab is approved for HER2-positive breast cancer, trilaciclib has primarily been studied for myeloprotection during chemotherapy in small cell lung cancer and triple-negative breast cancer. There are no approvals or major clinical trials identified for this specific triple-drug combination.