Inclusion Criteria:
* Phase 1 Dose Escalation cohorts, Phase 1 Backfill cohorts, and Phase 2 Tumor Type-Specific cohort(s): must meet one of the following criteria:
* HER2- metastatic breast cancer:
1. Hormone refractory hormone receptor positive metastatic breast cancer with progression on or after treatment with CDK4/6 inhibitor plus at least one line of systemic chemotherapy in the advanced setting
2. Triple negative metastatic breast cancer with progression after at one line of systemic chemotherapy in the advanced setting.
* Patients with advanced solid tumors that progressed on or following treatment with Enhertu and/or Trodelvy per label
* mCRPC: Histologically confirmed, metastatic castration resistant adenocarcinoma of the prostate
1. May have received up to 2 prior chemotherapies in mCRPC setting
2. Prior therapy with PARP (poly-ADP ribose polymerase) inhibitor, PLUVICTO, Radium-223, or Provenge is allowed
* Pancreatic cancer: PDAC (pancreatic ductal adenocarcinoma) with progression on or after treatment with at least one line of systemic chemotherapy in the advanced setting.
* PROC: Histologically or cytologically confirmed platinum-resistant high-grade serous ovarian, fallopian, or primary peritoneal cancer;
* Phase 1 Dose Escalation cohorts, Phase 1 Backfill cohorts, and Phase 2 Tumor Type-Specific cohorts (except mCRPC; see inclusion criterion 2 above): must have measurable disease per RECIST 1.1
* Phase 2 All Comers cohort: Patients with advanced solid tumors that have progressed during or after treatment with approved therapies or for whom there is no standard effective therapy available.
* Adequate bone marrow and organ function.
* Provide informed consent, which includes compliance with protocol-specified requirements and restrictions
Exclusion Criteria:
* Chemotherapy, hormonal therapy (with the exception of ongoing luteinizing hormone-releasing hormone analogs in male patients and premenopausal females), radiation therapy, or biological anticancer therapy within 14 days before the first dose of study treatment
* Treatment with an investigational agent for any indication within 14 days before the first dose of study treatment for non-myelosuppressive agent, or within 21 days or \<5 half-lives before the first dose of study treatment, whichever is longer, for a myelosuppressive agent
* Ongoing or active infection requiring systemic therapy, or an infection requiring hospitalization or intravenous therapy within 2 weeks before the first dose of study treatment
* Resting left ventricular ejection fraction (LVEF) of \<50% obtained by echocardiography or multigated acquisition scan (MUGA)
* History of significant cardiac disease, including myocardial infarction, New York Heart Association Class II/III/IV heart failure, unstable angina, unstable cardiac arrhythmias (eg, ventricular tachycardia, ventricular fibrillation), syncope of cardiovascular etiology, or cardiac arrest:
* Known immunosuppressive disease or active systemic autoimmune disease such as systemic lupus erythematosus, human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV) infections not currently controlled by current disease-specific therapy. The following exceptions apply:
* Major surgical procedure within 2 weeks before the first dose of study treatment, or an anticipated need for major surgery during the course of the study
* Other cancer within 2 years before the first dose of study treatment with metastatic or local recurrence potential that could negatively impact survival and/or potentially confound tumor response assessments. Patients with a history of other cancers in the past 2 years should be discussed with the Medical Monitor.
* Female patients who are pregnant or breastfeeding
