First-in-Human Study of STX-478 as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors

Key Who May Qualify: - 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 your organs (liver, kidneys, etc.) are working well enough based on blood tests as defined per protocol Key Who Should NOT Join This Trial: - 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 waiting period after previous treatment of 28 days. Endocrine therapy does not require a waiting period after previous treatment 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 Always talk to your doctor about whether this trial is right for you.