Phase Ib trial of docetaxel, prednisone, and pazopanib, in men with metastatic castration resistant prostate cancer (mCRPC).
275 Background: Docetaxel prednisone (DP) is a standard of care for men with metastatic castrate resistant prostate cancer (mCRPC) with median progression-free survival (PFS) of 4-6 months and overall survival (OS) of 19 months, supporting a need for further treatment options. Pazopanib (PAZO) is a multi-targeted kinase inhibitor of VEGF receptors approved for treatment of kidney cancer and sarcoma. We performed a two center, Phase Ib study of DP + PAZO to evaluate the safety and early efficacy in mCRPC. Methods: This is a 2 site phase 1 DOD Prostate Cancer Clinical Trials Consortium trial of DP + PAZO once daily with ongoing ADT in men with mCRPC. The primary endpoint was safety; secondary endpoints included evaluation of a maximum tolerated dose (MTD) through a dose escalation and expansion design, pharmacokinetic assessments, PSA and radiographic responses, and toxicity. Results: Twenty-five men were treated over 6 dose levels using a 3+3 design. Pegfilgrastim (Neu) was added to the regimen after myelosuppression limited dose escalation. With Neu, our target MTD of D 75 mg/m2; P 10 mg QD and PAZO 800 mg QD was reached. Eleven additional patients were accrued at this dose level for a total of 36 patients. 17 patients had received prior Abi and/or Enza. The most common AEs were alopecia (86%), fatigue (69%), diarrhea (58%), and nausea (53%), and the most common Grade 3-5 SAEs were neutropenia (33%) and leukopenia (19%). Three deaths attributed to study treatment occurred: one from pneumonitis, one from respiratory failure, and one from intracranial hemorrhage. The proportion of 30%, 50% and 90 % PSA declines were 69%, 58% and 25%, respectively. The objective response rate was 31% (11/36). Median PFS was 18.6 months (95% CI: 6.5, 27.7) and OS was 22.2 months (95% CI: 14.7, -). Predicted median OS using the Halabi nomogram was 20.9 months (95% CI: 19.2, 23.0) with 23%, 34% and 43% of patients in low, intermediate and high risk groups, respectively. Conclusions: DP + PAZO (with Neu) were tolerable at full doses and demonstrated a surprisingly long PFS and high objective response rate in a relatively poor risk group of mCRPC patients. These data support further randomized studies of DP + Pazo in Abi/Enza refractory patients. Clinical trial information: NCT01385228.
George, DJ; Halabi, S; Healy, P; Gemberling, S; Winters, C; Mundy, K; Harrison, MR; Szmulewitz, RZ; Armstrong, AJ
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