First-in-Human Study of STX-478, a Mutant-Selective PI3Kα Inhibitor as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors

Study STX-478-101 (LY4064809) is a multipart, open-label, phase 1/2 study evaluating the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of STX-478 (LY4064809) in participants with advanced solid tumors with P13Ka mutations. Part 1 will evaluate STX-478 as monotherapy in participants with advanced solid tumors. Part 2 will evaluate STX-478 therapy as combination therapy with fulvestrant in participants with hormone receptor positive (HR+) breast cancer. Part 3 will evaluate STX-478 as combination therapy with endocrine therapy (aromatase inhibitors, fulvestrant, tamoxifen, or imlunestrant) and a CDK4/6 Inhibitor (either Ribociclib, Palbociclib or Abemaciclib) in participants with HR+ breast cancer. Each study part will include a 28-day screening period, followed by treatment with STX-478 monotherapy or combination therapy.

Drug: STX-478, Drug: Fulvestrant, Drug: Ribociclib, Drug: Palbociclib, Drug: Letrozole, Drug: Anastrozole, Drug: Exemestane, Drug: Abemaciclib, Drug: Metformin