OKI-219 + trastuzumab + tucatinib

**OKI-219 + trastuzumab + tucatinib** is a combination therapy under investigation for advanced, locally advanced, unresectable, or metastatic breast cancer with HER2 positivity and the PI3KαH1047R mutation. OKI-219 is an allosteric, direct-mutation inhibitor selective for the PI3KαH1047R mutant (PIK3CA), designed to inhibit the mutated PI3K pathway prevalent in certain cancers. Trastuzumab is a monoclonal antibody that targets the HER2 receptor (ERBB2), while tucatinib is a small molecule inhibitor that selectively inhibits the HER2 receptor's kinase activity. The rationale for the combination is to simultaneously inhibit the PI3K signaling (which drives tumorigenesis in PIK3CA mutant cancers) and HER2 signaling (critical in HER2+ breast cancer), potentially overcoming resistance and improving efficacy. This combination is currently being evaluated in early-phase clinical trials for safety, tolerability, and preliminary efficacy in the above patient population[2][3][5][7].