A Study of Mevrometostat for Treatment of Relapsed/Refractory SCLC, Castration Resistant Prostate Cancer, and Follicular Lymphoma

Part 1 and Part 2 (Closed for enrollment). Part 3 Key Inclusion Criteria: * Histological or cytological diagnosis of castration resistant prostate cancer. * Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) of 0-2 with expected life expectancy of at least 6 months. * Adequate bone marrow, renal, and liver function Part 3 Key Exclusion Criteria: * 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. * Current use or anticipated need for food or drugs that are known strong and moderate CYP3A4/5 inducers or inhibitors * Prior enzalutamide within the last 4 weeks * DDI SUBSTUDY: * history of CHF or evidence of ventricular dysfunction * fructose intolerance * coadministration of CYP3A4 substrates