Brigham Research Institute (BRI) - Brigham and Women's Hospital

Histological or cytological diagnosis of advanced / metastatic solid tumor with the following tumor types in individual study parts: Part 1A (closed to enrollment): Part 1B (closed to enrollment): Part 1C: - Metastatic Castration resistant prostate cancer. Patients should have received either abiraterone and/or enzalutamide treatment and have evidence of prostate cancer progression (per PCWG3) Japan cohort - Castration resistant prostate cancer that is resistant to SOC or for which no local regulatory approved SOC is available that would confer significant clinical benefit in the medical judgement of the investigator. Patients should have received either abiraterone and/or enzalutamide treatment and have evidence of prostate cancer progression (per PCWG3) China cohort - Castration resistant prostate cancer that is intolerant/resistant to SOC or for which no local regulatory approved SOC is available that would confer significant clinical benefit in the medical judgement of the investigator. Patients who refused SOC may be eligible. Patients should have received either abiraterone and/or enzalutamide treatment and have evidence of prostate cancer progression (per PCWG3) Part 2A: • Metastatic Castration resistant prostate cancer. Patients should have received either abiraterone and/or enzalutamide treatment, may have received up to 1 line of chemotherapy and have evidence of prostate cancer progression (per PCWG3) Part 2B/2C: - Metastatic Castration resistant prostate cancer. Patients should have received abiraterone treatment, may have received up to 1 prior line of chemotherapy, have not received prior enzalutamide, apalutamide or darolutamide and have evidence of prostate cancer progression (per PCWG3) - Patients must have radiographic evidence of disease Other inclusion criteria: -Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) of 0 or 1.

• Prior Chemotherapy: Part 1C , Japan cohort and China cohort (CRPC): no more than 2 previous regimens of chemotherapy Part 2A: mCRPC: no more than 1 previous regimen of systemic chemotherapy Part 2B (mCRPC): no more than 1 previous regimen of chemotherapy - Prior irradiation to >25% of the bone marrow. - QTcF interval >480 msec at screening. - Hypertension that cannot be controlled by medications (>150/90 mmHg despite optimal medical therapy). - Known or suspected hypersensitivity to PF 06821497 or any components or enzalutamide (CRPC) - Active inflammatory gastrointestinal disease, chronic diarrhea, known diverticular disease or previous gastric resection or lap band surgery. Gastroesophageal reflux disease under treatment with proton pump inhibitors is allowed. - Current use or anticipated need for food or drugs that are known strong CYP3A4/5 inducers or inhibitors, including their administration within 10 days or 5 half lives of the CYP3A4/5 inhibitor, whichever is longer prior to first dose of investigational product.