ZN-C5 + abemaciclib

**ZN-C5 + abemaciclib** is an investigational combination therapy evaluated in advanced or metastatic estrogen receptor (ER) positive, HER2-negative breast cancer. ZN-C5 is an oral selective estrogen receptor degrader (SERD) that targets and degrades the estrogen receptor to inhibit breast cancer growth. Abemaciclib is an oral small molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), interfering with cell cycle progression and tumor cell proliferation. The combination aims to enhance anti-tumor activity by simultaneously blocking estrogen receptor signaling (via ZN-C5) and halting cell cycle progression (via abemaciclib). ZN-C5 is being developed by Zentalis Pharmaceuticals, and abemaciclib (brand name Verzenio) is developed and manufactured by Eli Lilly. This combination is under clinical investigation, primarily in Phase 1b trials, for the treatment of ER+/HER2- advanced breast cancer[1][3].