Clinical and immunologic impact of short course enzalutamide without androgen deprivation therapy for biochemically recurrent prostate cancer

Authors

• R Amrit Madan
• J Hodge
• J Schlom
• JL Gulley
• WL Dahut

Abstract

Background: Enzalutamide (enz) is FDA approved for advanced prostate cancer, but studies are evaluating enz in earlier stages of disease. We have conducted a clinical trial (NCT01875250) of enz ± a therapeutic vaccine in biochemically recurrent prostate cancer. Methods: Eligible patients (pts) had a PSA between 2.0-20.0 ng/ml, no metastatic disease and normal testosterone (T). Treatment for all pts included enz 160 mg daily for 84 days (D), but no T lowering therapy was permitted. This analysis evaluated all pts for the impact of enz on PSA and T regardless of randomization. Pts treated with Enz alone were evaluated for immune responses. The impact of the vaccine will be evaluated after protocol-defined requisite follow-up. Results: Median age for all pts (n = 34) was 66 years (range: 52-87), with a median on-study baseline PSA of 4.55 ng/ml (2.02-19.43). Common adverse events included fatigue and breast tenderness, but no pts discontinued enz for toxicity. The median PSA decline was 99% (range: 52% to > 99%) with 11/34 pts having undetectable nadirs. Median time to first PSA rise after 84 D course of enz was 29 D (13-70) and median recovery to baseline PSA in 25 evaluable pts was 190 D (84-469). T increased above normal limits in 18/34 pts (median Tmax = 802 ng/dl). Immune analysis (n = 12) indicated enz alone increased naïve T-cells and NK cells, and decreased several subsets of myeloid derived suppressor cells with a highly suppressive phenotype. Conclusions:

Scientific Focus Area: Institute, Center, and Scientific Directors

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