OnabotulinumtoxinA Treatment for Masseter Muscle Prominence: 6-Month Safety and Efficacy Results, Including Patient-Reported Outcomes, From a Phase 3, Randomized, Placebo-Controlled, Multiregional Trial.

Abstract

Masseter muscle prominence (MMP) may be aesthetically bothersome to some individuals, leading them to seek treatment for a slimmer lower face. The aim of this study was to evaluate the safety and efficacy of onabotulinumtoxinA for the treatment of MMP, including patient-reported outcomes (PROs). This was a prospective, multicenter trial including a randomized, double-blind, placebo-controlled period (Days 1-180) in which adults rated Grade 4 or 5 (marked/very marked) on the investigator-assessed MMP Scale (MMPS) were randomized to onabotulinumtoxinA 72 U or placebo. Efficacy endpoints were assessed at Day 90. The primary endpoint was ≥2-grade improvement from baseline on the investigator-assessed MMPS. Secondary endpoints included achieving Grade ≤3 on the MMPS and participant-assessed MMPS-Participant (MMPS-P), ≥2-grade improvement on the participant-assessed MMPS-P, and change from baseline in lower-facial width. Outcomes were assessed using validated measures. Adverse events (AEs) were monitored. Of 376 enrolled participants (onabotulinumtoxinA, n = 283; placebo, n = 93), 310 (82.4%) completed the study. At Day 90, a greater proportion of onabotulinumtoxinA-treated participants vs placebo achieved MMPS ≥2-grade improvement (51.2% vs 2.2%, P < .0001), and more onabotulinumtoxinA-treated participants vs placebo achieved the secondary endpoints (all P < .0001), with a mean lower-facial width reduction of -5.24 mm for onabotulinumtoxinA vs -0.04 mm for placebo (P < .0001). Participants reported benefits for onabotulinumtoxinA vs placebo in self-perceived change in MMP, treatment satisfaction, and psychosocial impact. Improvements were sustained through Day 180. Most AEs were mild, nonserious, and resolved. OnabotulinumtoxinA effectively reduced the appearance of MMP and improved PROs, with effects lasting up to 6 months and a favorable safety profile.