• Histologically confirmed locally advanced or metastatic castration-resistant prostate cancer, pancreatic cancer, or HPV-negative SCCHN for which no other lines of standard therapy with demonstrated clinical benefit are available or appropriate as treatment.

• Appropriate to enter a clinical trial with a minimum estimated life expectancy of at least 3 months.

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.

• Measurable disease as defined by RECIST 1.1. Patients with castration-resistant prostate cancer can have measurable or evaluable disease per PCWG3 criteria. Patients with evaluable disease must have documented evidence of PD as defined by any of the following:

‣ PSA progression: minimum of 2 rising values (3 measurements) obtained a minimum of 7 days apart with the last result being at least ≥4.0 ng/mL.

⁃ New or increasing non-bone disease per RECIST 1.1 criteria.

⁃ Positive bone scan with 2 or more new lesions (PCWG3).

• Adequate bone marrow function as defined by the following laboratory test results obtained within 7 days of Cycle 1 Day 1:

‣ White blood cell count ≥2500 cells/mm3.

⁃ Absolute neutrophil count ≥1500 cells/mm3.

⁃ Absolute lymphocyte count \>500 cells/mm3.

⁃ Hemoglobin ≥9 g/dL.

⁃ Platelets ≥75,000 cells/mm3.

• Adequate liver function as defined by the following laboratory test results obtained within 7 days of Cycle 1 Day 1:

‣ Bilirubin ≤1.5 × institutional ULN; for patients with known Gilbert's syndrome, ≤3 × institutional ULN.

⁃ Aspartate aminotransferase (SGOT) and alanine aminotransferase (SGPT) ≤3 × institutional ULN; if liver metastases are present, then ≤5 × ULN is allowed.

• At least 3 weeks from previous cytotoxic chemotherapy or radiation therapy and at least 5 half-lives or 6 weeks, whichever is shorter, from targeted or biologic therapy with the exception of CTLA-4, PD-1, or PD-L1 blocking antibodies for which only a 2 week interval is required. Patients with prostate cancer, unless they have undergone prior orchiectomy, may continue to receive androgen deprivation therapy, anti-androgen therapy, or therapy that interferes with androgenic stimulation.

• All patients must be willing to undergo a biopsy to provide a new tumor sample within 14 days of Cycle 1 Day 1. Patients who are unable to undergo a biopsy at screening must submit archival tumor tissue retrieved within the last 6 calendar months. Patients must also consent to undergo a biopsy between Day 15 of Cycle 2 and Day 8 of Cycle 3 in those subjects which it is clinically safe and attainable. A biopsy is not required for participants with metastatic prostate cancer with bone-only disease or inaccessible soft tissue lesions.

• Calculated creatinine clearance ≥ 60 mL/min (by the Cockcroft Gault formula) within 7 days of Cycle 1 Day 1