The MOBILE Study-A Phase IIa Enriched Enrollment Randomized Withdrawal Trial to Assess the Analgesic Efficacy and Safety of ASP8477, a Fatty Acid Amide Hydrolase Inhibitor, in Patients with Peripheral Neuropathic Pain

Objective. To evaluate the analgesic efficacy and safety of ASP8477 in patients with peripheral neuropathic pain (PNP). Design. Enriched enrollment randomized withdrawal. Setting. Centers in Poland (four), Czech Republic (six), and the United Kingdom (two). Subjects. Patients aged 18 years or older with PNP resulting from painful diabetic peripheral neuropathy or postherpetic neuralgia. Methods. A four-week screening period followed by a single-blind period (six-day dose titration and three-week maintenance period with ASP8477 [20/30mg BID]). Treatment responders (defined as a >= 30% decrease in the mean average daily pain intensity during the last three days of the single-blind period) were stratified by disease and randomized to receive placebo or continue ASP8477 during a three-week, double-blind, randomized withdrawal period. The primary end point was change in mean 24-hour average numeric pain rating scale (NPRS) from baseline to end of double-blind period. Results. Among 132 patients who enrolled, 116 entered the single-blind period and 63 (ASP8477, N=31; placebo, N=32) completed the double-blind period. There was no difference in mean 24-hour average NPRS score (P=0.644) or in time-to-treatment failure (P=0.485) between ASP8477 and placebo. During the single-blind period, 57.8% of patients were treatment responders. ASP8477 was well tolerated. During the single-blind period, 22% of patients experienced at least one treatment-related adverse event (TEAE); during the doubleblind period, 8% in the ASP8477 arm and 18% in the placebo arm experienced at least one TEAE. Conclusions. ASP8477 was well tolerated in patients with PNP; however, ASP8477 did not demonstrate a significant treatment difference compared with placebo.