Neo-DAB: Darolutamide and Abemaciclib in Prostate Cancer

Inclusion Criteria For Phase 1: * Provision of signed informed consent prior to any study specific procedures, or have a legally authorized representative sign on the participant's behalf. * Ability to swallow oral medications and comply with study procedures and requirements. * Males ≥18 years * Histologically or cytologically confirmed adenocarcinoma of the prostate without histologic variants (including neuroendocrine differentiation, small cell, sarcomatoid, ductal adenocarcinoma, squamous or transitional cell carcinoma) comprising \>50% of the sample as determined by academic medical center pathology review; men without histologic confirmation are eligible provided there is unequivocal evidence of prostate cancer (eg. very high PSA) in the view of the treating physician. * M0 or M1 (by CT/MRI and bone scans) CRPC with evidence of progression at study entry demonstrated during continuous androgen deprivation therapy (LHRH/GnRH agonists/antagonists/post orchiectomy) and castrate level of serum testosterone (≤50 ng/dl). Progression is defined as one or more of the following: * Sequence of at least 2 rising PSA values at a minimum of 1-week intervals with the last result being at least 1.0 ng/mL if confirmed PSA rise is the only indication of progression. Patients who received an anti-androgen (flutamide, bicalutamide or nilutamide) must have PSA progression ≥4 weeks after the last dose. * Radiographic progression per RECIST 1.1 for soft tissue and/or per PCWG3 for bon…