The Phase 1a part of the study is a dose escalation of STP938 as a monotherapy.

The Phase 1b part of the study is a safety expansion cohort of STP938 as a monotherapy.

Main Inclusion Criteria:

• Signed and dated informed consent, and able to comply with the study procedures and any locally required authorization.
• Male or female aged ≥ 18 years.
• Advanced disease not curable by available therapies and requires systemic therapy.
• Histologically confirmed diagnosis of eligible cancer type.
• Must have tumor tissue available for biomarker testing.
• Measurable disease (Part 1) and measurable disease per RECIST (Part2)
• Eastern Cooperative Oncology Group (ECOG) performance status ≤2.
• Life expectancy > 3 months as assessed by the Investigator.
• Adequate organ function (bone marrow, hepatic, renal function and coagulation).
• All toxicities (except alopecia) from prior cancer treatments or procedures must have resolved to ≤Grade 1 or returned to baseline levels prior to enrollment.

Main Exclusion Criteria:

• Pregnant or breastfeeding females and women of childbearing potential or males unwilling to comply with contraception requirements.
• Known active or symptomatic CNS metastases, carcinomatous meningitis, leptomeningeal disease or a history of spinal cord compression
• Active malignancy within 2 years of study enrollment
• Prior radiation within 2 weeks of start of therapy.
• Systemic cancer treatments, monoclonal antibody-directed therapies, other investigational agents within 4 weeks before enrollment, or <5 half-lives since completion of previous investigational therapy, whichever is shorter.
• Uncontrolled intercurrent illness.
• Immunocompromised subjects with increased risk of opportunistic infections or history of opportunistic infection in the last 12 months.
• Known active or chronic hepatitis B or active hepatitis C virus (HCV) infection.
• Subjects with corrected QT interval >470 msec based on averaged triplicate electrocardiogram (ECG) readings at the Screening Visit using the QT interval corrected for heart rate using Fridericia's method (QTcF).