A prostate cancer clinical trials consortium trial of disulfiram (D) in men with nonmetastatic recurrent prostate cancer (PCa).

219 Background: Epigenetic silencing of tumor suppressor genes (TSG) by promoter methylation contributes to carcinogenesis and progression. Targeting these epigenetic changes in PCa has been hindered by a paucity of available agents. D potently inhibits PCa growth in vitro and can cause demethylation and re-expression of known TSGs in PCa cells lines. METHODS: To determine if D leads to demethylation changes [i.e. decreased global 5(me)C DNA content from peripheral blood mononuclear cells (PBMC)] we conducted an open-label, dose escalation trial of D in men with non-metastatic recurrent PCa after local therapy. Dose escalation occurred if a demethylating "response" (i.e. >10% decrease in global 5(me)C content) in <3 patients was observed in cohort 1. Cohort 1 and 2 received D 250 mg and 500 mg daily respectively; 1 cycle equaled 4 weeks. The primary endpoint was the proportion of subjects with a demethylation response. Secondary endpoints included rate of PSA progression at 6 months (i.e. confirmed >50% rise over baseline and >2 ng/mL above nadir), changes in PSA doubling time (PSADT) and safety/tolerability. RESULTS: Two patients out of 9 (22.2%) in cohort 1 met our primary endpoint. Cohort 2 accrued a total of 10 patients, 3 (30.0%) of which had >10% decrease in global 5(me)C content. Only 5 subjects were on trial for ≥6 months, all were in cohort 1 and all had PSA progression by 6 months. Median PSADT change post-treatment was not significantly different between responders and non-responders (266.9 vs -7.8 days, P=0.18) or between cohorts 1 and 2 (22.5 vs -39.7 days, P=0.54). While there were no grade (G) 4 adverse events (AE), the drug was poorly tolerated with 6 patients experiencing G3 AE (3 per cohort). There was a trend toward fewer median number of completed cycles in cohort 2 vs cohort 1 (5 vs 9 cycles, P=0.12). Common AE included: fatigue, GI toxicity, ataxia/dizziness, and constitutional symptoms. CONCLUSIONS: A minority of patients had global PBMC demethylation changes, consistent with D acting as a probable demethylating agent in those individuals. Given the toxicities associated with D and no significant clinical benefits, further development of this agent should not be pursued in this population. CLINICAL TRIAL INFORMATION: NCT01118741.

Duke Scholars

Author Andrew John Armstrong Medicine, Medical Oncology