Reduction of masseter muscle prominence after treatment with onabotulinumtoxinA: Primary results from a randomized phase 2 study.

Abstract

OnabotA is used to treat masseter muscle prominence (MMP). To assess the safety and efficacy of OnabotA for MMP in a randomized study. This 12-month, multicenter, double-blind, placebo-controlled, phase 2 study randomized adults (18-50 years of age) with marked/very marked bilateral MMP (≥4 on the Masseter Muscle Prominence Scale [MMPS]) to OnabotA (24, 48, 72, or 96 U) or placebo; retreatment occurred at day 180 if MMPS ≥4. Lower facial volume at day 90 was measured using Vectra 3-dimensional photography. Safety assessments included computed tomography and dental exams. Evaluations occurred monthly through day 360. Among 187 randomized subjects, significant lower facial volume reductions and percentage of responders (MMPS grade ≤3) were greater with OnabotA versus placebo at day 90 (P < .001 and ≤.008, respectively). Similar efficacy was observed with retreatment. No dose-related safety trends or clinically relevant changes in the mandible or teeth occurred. Localized impact on smile was reported with 96 U OnabotA (n = 4). Limited sample size per individual treatment group. OnabotA administered in 1 or 2 treatments over 1 year was associated with significant reductions in masseter muscle volume and MMP severity, with an acceptable safety profile.