Efficacy and Safety of ASP0819 in Patients with Fibromyalgia: Results of a Proof-of-Concept, Randomized, Double-Blind, Placebo-Controlled Trial

Purpose: ASP0819 is a novel, non-opioid K(Ca)3.1 channel opener that reverses abnormal nerve firing of primary sensory afferent nerves. Currently available treatments for fibromyalgia provide only modest relief and are accompanied by a host of adverse side effects. Patients and Methods: In this phase 2a, double-blind trial (NCT03056690), adults meeting fibromyalgia diagnostic criteria were randomized 1:1 to receive either 15 mg/day of oral ASP0819 (n=91) or placebo (n=95). The primary endpoint was the change from baseline to Week 8 in the mean daily average pain score. Changes in the Fibromyalgia Impact Questionnaire Revised (FIQR) symptoms, function, and overall impact subscales, as well as changes in the patients' global impression of change, were secondary endpoints; treatment effects on FIQR total score and impact on sleep were exploratory analyses. Results: There was no statistically significant difference between ASP0819 and placebo for the primary endpoint (P=0.086); however, ASP0819 versus placebo significantly improved daily average pain at Weeks 2, 6, and 7 (all P<0.05). Numerical improvements were observed on the FIQR total score and several sleep items showed statistically significant improvements with ASP0819 versus placebo. There were no major safety concerns with ASP0819. Headache was the most common treatment-emergent adverse event (TEAE) occurring in both study arms; most TEAEs were mild or moderate in severity and no TEAEs suggestive of potential drug abuse were observed, as assessed by TEAE reporting and/or safety evaluations. Withdrawal effects also were not observed. Conclusion: ASP0819 demonstrated some signals suggestive of efficacy and had a good tolerability profile in patients with fibromyalgia. Further studies are required to determine if ASP0819 can be a novel non-opioid treatment option in this patient group.