LAUSR

TPS1109Background: Inhibition of CDK4 in preclinical models, demonstrated efficacy in HER2+ breast cancer and enhanced activity of HER2-targeted therapy suggesting a crosstalk between HER2 signaling and the cyclin D/CDK4 signaling pathway in which CDK4 & CDK6 inhibitors may re-sensitize resistant tumors to HER2 blockade.Abemaciclib is a selective inhibitor of CDK4 & CDK6 inhibitor that demonstrates single-agent anti-tumor activity on a continuous dosing schedule in women with hormone receptor positive (HR+) advanced breast cancer. Triple regimens with abemaciclib have been tolerable. Methods: monarcHER is an ongoing Phase 2, open-label, study in postmenopausal women with HR+, HER2+ locally advanced or metastatic breast cancer. Eligible patients (pts) are those previously treated with ≥2 HER2-directed therapies in advanced disease setting; T-DM1 and a taxane in any disease setting; no prior treatment with fulvestrant or any CDK4 & CDK6 inhibitor or with ECOG PS ≤1; LVEF ≥50%; no visceral crisis and no CNS ...