Phase Ib Trial of Cabazitaxel and Tasquinimod in Men With Heavily Pretreated Metastatic Castration Resistant Prostate Cancer (mCRPC): The CATCH Trial

BACKGROUND. Tasquinimod is an immunomodulating and anti-antiangiogenic oral agent with anti-prostate cancer activity in preclinical studies and in clinical trials of men with metastatic castration resistant prostate cancer (mCRPC), including single agent activity and in combination with taxanes. We sought to identify the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of tasquinimod in combination with cabazitaxel and prednisone in men with chemorefractory mCRPC. METHODS. Men with mCRPC who had failed prior docetaxel chemotherapy received cabazitaxel 25mg/m2 every 3 weeks with oral tasquinimod at 1 of 3 escalating dose levels (0.25, 0.5, and 1.0mg once daily) with prednisone and PEG-filgastrim support, using a 3+3 dose escalation design. Treatment continued until progressive disease or unacceptable toxicity. RESULTS. We enrolled 25 men with chemorefractory mCRPC. The RP2D was 0.5mg tasquinimod based on excess DLTs (two of three men) observed at dose level 3 (1.0 mg) including grade 3 sensory neuropathy and grade 3 atrial fibrillation. Dose level 2 was expanded to 14 men, where 3 DLTs were observed: grade 3 fatigue, grade 4 febrile neutropenia, and grade 3 liver function abnormalities. The proportion of men with a >= 30% PSA decline was 63% and the median composite progression-free survival (PFS) was 8.5 months (95% CI 4.2-16.4 months) based on 12 PFS events. The median number of cycles of cabazitaxel was 6 (range 1-13), with six men receiving > 10 cycles. Best overall RECIST responses (CR+PR) were observed in three men (12%), with stable disease in 12 (48%). No pharmacokinetic interactions were observed. CONCLUSIONS. We determined the RP2D of tasquinimod combined with cabazitaxel to be 0.5mg daily following a 3 week lead-in of tasquinimod 0.25mg with growth factor support. No unexpected toxicities occurred. (C) 2016 Wiley Periodicals, Inc.