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.
Has an advanced or refractory solid tumor malignancy that is metastatic or locally advanced and unresectable (as specified by Cohort)
Has a new or recent tumor biopsy (collected at screening, if feasible) or will provide an adequate tissue sample prior to screening
Has a tumor that harbors a documented PI3Kα mutation (cohort specific criterion for cohort-specific mutation types)
Is ≥18 years of age at the time of signing the ICF
Has history (within ≤2 years before screening) of a solid tumor or hematological malignancy that is histologically distinct from the cancers being studied
Has symptomatic brain or spinal metastases
Has an established diagnosis of uncontrolled diabetes mellitus (defined as HbA1c ≥8% and/or FBG ≥140 mg/dL [7.7 mmol/L] and/or requiring or required insulin).
Has had prior treatment with PI3K/AKT/mTOR inhibitor(s), except in certain circumstances