This study is being done to see if tucatinib works better than placebo when given with other drugs to treat participants with HER2-positive breast cancer. A placebo is a pill that looks the same as tucatinib but has no medicine in it. This study will also test what side effects happen when participants take this combination of drugs. A side effect is anything a drug does to the body besides treating your disease. Participants will have cancer that has spread in the body near where it started (locally advanced) and cannot be removed (unresectable) or has spread through the body (metastatic). In this study, all participants will get either tucatinib or placebo. Participants will be assigned randomly to a group. This is a blinded study, so patients and their doctors will not know which group a participant is in. All participants will also get trastuzumab and pertuzumab. These are 2 drugs used to treat this type of cancer.
Phase 3 trials are pivotal studies with large patient populations (hundreds to thousands) designed to prove efficacy and safety for FDA submission. A successful Phase 3 readout is typically the last major hurdle before a New Drug Application (NDA) or BLA filing.
Enrollment is complete. The trial is in its follow-up or data collection phase — a readout may occur on or near the primary completion date.
Pfizer Inc (PFE) is the sponsoring company for this trial. BiotechSign currently grades this company F (33/100) based on composite catalyst signals across its full pipeline. This trial is one data point in that overall catalyst picture.