Trastuzumab emtansine (T-DM1) and ribociclib, an oral inhibitor of cyclin dependent kinase 4 and 6 (CDK 4/6), for patients with metastatic HER2-positive breast cancer.

Abstract

1028 Background: Current therapeutic efforts in the management of HER2+ MBC focus on targeting the HER receptor family, however co-inhibition of targets downstream of the HER2 pathway, such as cyclin D-CDK 4/6, could enhance therapeutic efficacy. We conducted a phase 1b study of the CDK4/6 inhibitor ribociclib and T-DM1 in patients (pts) with HER2+ MBC. The primary objective was to determine the recommended phase 2 dose (RP2D) of ribociclib plus T-DM1. Secondary objectives included safety, PK assessments, and efficacy. Methods: Pts with HER2+ MBC who previously received at least 1 taxane and trastuzumab-containing regimen in any setting were eligible. Pts with previous CDK4/6 inhibitor expo..