First-in-Human Study of STX-478, a Mutant-Selective PI3Ka; Inhibitor as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors

Key Inclusion Criteria:
*  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 an ECOG performance status score of 0 or 1 at screening
*  Has adequate organ function as defined per protocol

Key Exclusion Criteria:
*  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
*  Has had treatment with any local or systemic antineoplastic therapy or investigational anticancer agent within 14 days or 4 half-lives, whichever is longer, prior to the initiation of study treatment up to a maximum washout period of 28 days. Endocrine therapy does not require a washout period if the patient is enrolling in a cohort with the same combination endocrine therapy.
*  Has toxicities from previous anticancer therapies that have not resolved to baseline levels or CTCAE grade ≤1, with the exception of alopecia and peripheral neuropathy.
*  Has had radiotherapy within 14 days before the initiation of study treatment