Our ex vivo and in vivo CU-PC01 PDX preclinical studies corroborate clinical findings that AR-negative mCRPC tumours are resistant to ARTT (enzalutamide) and chemotherapy (docetaxel) [2,8,83] mirroring the donor patient, and strengthen the rationale to explore PARP inhibitors in AR-negative mCRPC variants with a BRCA2 mutation. This evidence concerns the gene AR and neoplasm.