METHODS: Data were pooled from 2 multicenter, double-blind, placebo-controlled, parallel-group, 14-week treatment studies of mirogabalin conducted at ∼350 study sites (Japan, South Korea, Taiwan, Singapore, Malaysia, and Thailand). Eligible patients in both studies were randomized in a 2:1:1:1 ratio, stratified according to a baseline average daily pain score (ADPS) of <6 or ≥6, to placebo, mirogabalin 15-mg once daily (QD), mirogabalin 10-mg twice daily (BID), or mirogabalin 15-mg BID treatment groups. Safety was assessed based on treatment-emergent adverse events identified from the adverse events collected throughout both studies. The primary efficacy end point of both studies was the change from baseline in ADPS at week 14.

FINDINGS: In total, 1587 patients (824 with diabetic peripheral neuropathic pain; 763 with post-herpetic neuralgia) who received at least 1 dose of study drug were analyzed (633 received placebo, 954 treated with mirogabalin). Treatment-emergent adverse events included somnolence (3.8%, 10.8%, 14.5%, and 19.1%) and dizziness (2.7%, 5.7%, 9.1%, and 13.1%) in patients receiving placebo, mirogabalin 15 mg QD, mirogabalin 10 mg BID, and mirogabalin 15 mg BID, respectively. In patients treated with mirogabalin 15 mg QD, 2 (0.6%) of 316 patients discontinued due to somnolence. In the mirogabalin 10-mg BID group, somnolence, edema, and peripheral edema each resulted in 3 (0.9%) of 318 patient discontinuations. In the mirogabalin 15-mg BID group, 6 (1.9%) of 320 patients discontinued due to dizziness and 3 (0.9%) due to somnolence. At week 14, mirogabalin 10 mg BID and 15 mg BID statistically significantly improved ADPS versus placebo, with least squares mean changes (95% CI) of -0.31 (-0.55, -0.08) and -0.63 (-0.86, -0.40). Post hoc analysis showed a statistically significant difference 2 days after administration in the mirogabalin 10-mg and 15-mg BID groups compared with placebo. Female sex, age ≥65 years, and baseline weight <60 kg may influence the safety of mirogabalin, particularly regarding the incidence of somnolence and dizziness, but had no notable impact on efficacy. ClinicalTrials.gov identifiers: NCT02318706 and NCT02318719.