A 3+3 design was used to determine the recommended phase II dose (RP2D) for PT-112 (28-day cycle IV days 1, 8, 15) with avelumab 800 mg (days 1 and 15) in pts with progressing solid tumors, with no available effective therapy (Tx). Previous ICI Tx was allowed...Two CRPC pts responded: one with durable improved PSA and bone metastases, PFS 11.4 months (150mg/m2, MSI stable); another with confirmed RECIST partial response (66% reduction), PSA reduction (94%), bone scan improvement, and ongoing PFS 9.5 months (200 mg/m2, PIK3CBmut and PTEN loss, prior ICI Tx). 4 of 18 total CRPC pts had reductions in PSA ≥50%; 15 of 18 in alkaline phosphatase.