HER2CLIMB-05: This phase III study is trying to understand whether targeted therapy (tucatinib) works better than placebo when given with other drugs (trastuzumab and pertuzumab) to treat people with HER2-positive breast cancer.A Randomized, Double-blind, Phase 3 Study of Tucatinib or Placebo in Combination With Trastuzumab and Pertuzumab as Maintenance Therapy for Metastatic HER2+ Breast Cancer (HER2CLIMB-05)

Summary

Eligible participants will be randomly assigned to either the Experimental Arm or the Control Arm. In the Experimental Arm, participants will receive Tucatinib + trastuzumab + pertuzumab. Tucatinib (300mg) will be given by mouth (orally) twice daily. Tastuzumab will be given intravenously (via IV) at a dose of 6mg/kg or injected under the skin (subcutaneously) at a dose of 600mg, every 21 days. Pertuzumab (420mg) will be given via IV every 21 days. Alternatively, instead of receiving trastuzumab and pertuzumab individually, participants may receive a fixed dose combination of 600mg pertuzumab, 600mg trastuzumab, and 20,000 units hyaluronidase subcutaneously every 21 days. In the Control Arm, participants will receive Placebo + trastuzumab + pertuzumab. Placebo will be given orally, twice daily. Trastuzumab and Pertuzumab will be given as described in the Experimental Arm.