atezolizumab + cyclophosphamide + doxorubicin + nab-paclitaxel

This is a combination regimen consisting of four drugs: - **Atezolizumab** is a monoclonal antibody that acts as an immune checkpoint inhibitor by targeting programmed death-ligand 1 (PD-L1), thereby enhancing the immune system's ability to detect and destroy cancer cells[1][7][9]. - **Cyclophosphamide** is an alkylating agent that interferes with DNA replication, leading to cell death, particularly in rapidly dividing cancer cells. - **Doxorubicin** is an anthracycline antibiotic that intercalates DNA and inhibits topoisomerase II, resulting in inhibition of DNA synthesis and apoptosis. - **Nab-paclitaxel** (nanoparticle albumin-bound paclitaxel) is a microtubule inhibitor formulated with albumin nanoparticles for improved delivery; it disrupts mitosis by stabilizing microtubules. This combination has been studied primarily in breast cancer settings, including triple-negative breast cancer (TNBC), where it has shown high clinical and pathologic response rates. The addition of atezolizumab introduces immunotherapy into the chemotherapeutic backbone of cyclophosphamide, doxorubicin, and nab-paclitaxel[8][10]. Each component targets different aspects of tumor biology—immune evasion (atezolizumab), DNA damage (cyclophosphamide/doxorubicin), and mitotic arrest (nab-paclitaxel).