Population pharmacokinetics and exposure-response of trastuzumab emtansine in advanced breast cancer previously treated with ≥2 HER2-targeted regimens.

Exposure-response relationships for efficacy were inconsistent across exposure metrics. HRs for survival in patients in the lowest T-DM1 exposure quartile vs. matched TPC-treated patients suggest that, compared with TCP, the approved T-DM1 dose is unlikely to be detrimental to patients with low exposure.