elacestrant + palbociclib + abemaciclib + ribociclib

This is a combination of four orally administered small molecule drugs: **elacestrant** (an oral selective estrogen receptor degrader/antagonist), **palbociclib**, **abemaciclib**, and **ribociclib** (all oral selective CDK4/6 inhibitors). Elacestrant targets and degrades the estrogen receptor (ER), interfering with estrogen-driven proliferation in hormone receptor-positive (HR+) breast cancer. Palbociclib, abemaciclib, and ribociclib inhibit cyclin-dependent kinases 4 and 6 (CDK4/6), arresting cell cycle progression at the G1/S checkpoint. This combination is under clinical investigation for patients with estrogen receptor-positive (ER+), HER2-negative advanced or metastatic breast cancer, with the aim to overcome or prevent resistance to endocrine therapy and CDK4/6 inhibitors, by deeply targeting both ER signaling and cell cycle regulation. The ELEVATE and other ongoing trials are actively evaluating dual and triple combinations of these drugs, though the simultaneous quadruple use of all four in a single regimen (elacestrant + palbociclib + abemaciclib + ribociclib) has not been reported as a tested clinical regimen, as these three CDK4/6 inhibitors are generally used as alternatives, not concurrently[1][3][5][6][9].