A Study to Evaluate the Safety and Tolerability of TOS-358 in Adults With Select Solid Tumors

Key Inclusion Criteria Locally advanced, recurrent, or metastatic, incurable (any number of previous lines of therapy is allowed), histologically or cytologically confirmed: colorectal cancer; gastric cancer; non-small cell lung cancer; HER2- breast cancer; squamous cell carcinoma of the head and neck; urothelial cancer; or select gynecologic cancer (ovarian cancer, cervical cancer, or endometrial cancer) Willing and able to provide written informed consent for this study Adults ≥ 18 years old at time of consent Known PIK3CA mutations or amplifications as determined at a CAP/CLIA-certified or equivalently accredited diagnostic laboratory using a validated test Measurable disease by RECIST 1.1 Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 Life expectancy ≥ 3 months, as determined by the investigator Adequate bone marrow, liver, and kidney function within 14 days prior to first dose of investigational product Fasting plasma glucose < 126 mg/dL AND hemoglobin A1c (HbA1c) < 5.7% Available archived or fresh tumor tissue sample for detection of PIK3CA mutation by central laboratory test Key Exclusion Criteria Recent systemic anticancer treatment prior to start of treatment Prior treatment with any PI3K, AKT, or mTOR inhibitor, or any agent whose mechanism of action is to inhibit the PI3K-AKT-mTOR pathway, except for patients with breast cancer Second malignancy (solid or hematologic) within the past 3 years except: Adequately treated basal cell or squamous cell skin cancer; carcinoma in situ of the cervix, or prostate cancer with Gleason score < 6 and undetectable prostate specific antigen over 12 months ;ductal breast carcinoma in situ with full surgical resection (ie, negative margins); treated medullary or papillary thyroid cancer; metaplastic breast cancer History of diabetes of any type Body mass index (BMI) ≥ 30 Cushing syndrome Congestive heart failure (New York Heart Association Class III to IV), symptomatic ischemia, conduction abnormalities uncontrolled by conventional intervention, or myocardial infarction within 6 months prior to the first dose of investigational product Known active central nervous system (CNS) metastases.