Botox for Masseter Prominence Reduction

Sabrina Fabi, MD, double board-certified dermatologist, dermatologic cosmetic surgeon, and assistant clinical professor at the University of California, San Diego, recently presented study results (NCT02010775) evaluating onabotulinumtoxinA (Botox; Allergan) for the treatment of Masseter Muscle Prominence (MMP) at the American Academy of Dermatology Virtual Meeting Experience 2021 (AAD VMX).¹

The phase 2b study, a 6-month, multicenter, randomized, double-blind, dose comparison, placebo-controlled trial, had the objective to evaluate the efficacy and safety of onabotulinumtoxinA compared with placebo as treatment for MMP.

MMP reduction with onabotulinumtoxinA at 48 units and 72 units was evaluated in adults with symmetrical bilateral MMP rated as masseter muscle prominence scale (MMPS) Grade 4 or 5, considered as marked or very marked, respectively, by the investigator, and MMPS-P Grade 4 or 5, defined as pronounced or very pronounced by the participant. 

The primary endpoint of the study was the proportion of patients achieving clinician assessed MMPS Grade ≤ 3 at Day 90. Secondary endpoints included response rates for patient assessed MMPS-P Grade ≤ 3 and participant self-assessment of change (PSAC) Grade improvement of ≥ 2. This scale is a 5-point ranking based on the extent to which the masseter muscles protrude and the width of jawline, defined as much improved to much worse. 

The study included 150 patients randomized to a 1:1:1 ratio. 116 of the 150 patients completed the study. 

“This did occur during COVID-19 and so many discontinued as a result,” Fabi explained.

More than 90% of participants that received either 48 units or 72 units of onabotulinumtoxinA were MMPS responders at Day 90, compared to only 21.7% placebo. For MMPS-P, 96.2% using 48 units and 93.5% using 72 units of onabotulinumtoxinA were responders, compared to 47.8% of placebo patients. 

“You can see that there was really no significant difference between either 48 units or 72 units in achieving this primary endpoint,” Fabi said.

PSAC scores improved by 2 or more in 90.6% of the 48 units group and 73.9% of the 72 units group. 

Adverse events (AEs) occurred in 12.2%, 9.4%, and 0% of the 72 units, 48 units, and placebo treatment arms, respectively. Rates of treatment emergent adverse events (TEAEs) were similar for both doses of onabotulinumtoxinA. TEAEs were considered mild and resolved by the end of Month 6. The most common TEAE was nasopharyngitis. Other AEs included injection site pain, muscular weakness mastication disorder, and facial paresis. 

Disclosures:

Sabrina Fabi, Derek Jones, Brian Biesman, and Alexander Rivkin are investigators for Allergan Aesthetics, an AbbVie Company. Grace Pan, Beta Bowen, Elizabeth Lee, and Mitchell Brin are employees of AbbVie and may own company stock. 

References:

1. Fabi. S. Efficacy and Safety of 2 Does of OnabotulinumtoxinA for the Treatment of Masseter Muscle Prominence: A Phase 2b Placebo-Controlled Study. Presented at the: American Academy of Dermatology Virtual Meeting Experience 2021 (AAD VMX); Virtual.