OnabotulinumtoxinA 72 U reduces masseter prominence versus placebo in adults.

BACKGROUND: Masseter muscle prominence (MMP) may be aesthetically bothersome to some individuals, leading them to seek treatment for a slimmer lower face. OBJECTIVES: The aim of this study was to evaluate the safety and efficacy of onabotulinumtoxinA for the treatment of MMP, including patient-reported outcomes (PROs). METHODS: 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. RESULTS: 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. CONCLUSIONS: OnabotulinumtoxinA effectively reduced the appearance of MMP and improved PROs, with effects lasting up to 6 months and a favorable safety profile.