PIK3CA H1047X

Study STX-478-101 is a multipart, open-label, phase 1/2 study evaluating the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of STX-478 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 fulvestrant and a CDK4/6 Inhibitor (either Ribociclib or Palbociclib) 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.

This is a Phase 1, first-in-human, open-label study designed to evaluate the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of RLY-5836 in advanced solid tumors in participants harboring a PIK3CA mutation in blood and/or tumor per local assessment. The study consists of 2 parts, a dose escalation (Part 1) and a dose expansion (Part 2).