A Phase 1/2 Multicenter, Open-label, Dose-escalation, Safety, Pharmacodynamic, and Pharmacokinetic Study of Q901Administered Via Intravenous Infusion as Monotherapy and in Combination With Pembrolizumab in Adult Patients With Selected Advanced Solid Tumors With Cohort Expansions at the Recommended Phase 2 Dose

Inclusion Criteria: * Participants with histologically or cytologically confirmed advanced or metastatic ovarian, CRPC, HR+ HER2- breast, endometrial, colorectal, small-cell lung, or pancreatic cancer, who have progressed following standard-of-care therapy or for whom there is no standard therapy that confers clinical benefit * Measurable disease per RECIST v 1.1 * ECOG performance status 0,1 or 2 * Life expectancy of at least 3 months * Age ≥ 18 years * Signed, written IRB-approved informed consent form Exclusion Criteria: * New York Heart Association Class III or IV cardiac disease, or myocardial infarction, severe unstable angina, coronary/peripheral artery bypass graft, congestive heart failure within the past 6 months * Have a corrected QT interval (using Fridericia's correction formula) (QTcF) of \>470 msec (females) and \>450 msec (males) * Active, uncontrolled bacterial, viral, or fungal infections, requiring systemic therapy * Active, poorly controlled autoimmune or inflammatory diseases