The masseter muscle is one of the muscles in the lower face used for chewing. Prominence of the masseter muscle can appear as a widened and square lower face shape, which is an aesthetic concern for individuals who prefer a narrower and more ovoid lower face shape. Treatments are available for masseter muscle prominence (MMP), but researchers are looking for new non-surgical treatments. This study will assess adverse events and effectiveness of BOTOX in adult participants with MMP. BOTOX is being investigated for the treatment of MMP. Participants are placed in 1 of 4 groups, called treatment arms. Each group receives a different treatment. There is 1 in 5 chance that participants will be assigned to placebo. Around 250 adult participants with MMP will be enrolled in the study at approximately 20 sites in Japan. Participants will receive either BOTOX or Placebo administered as 6 intramuscular injections to each masseter muscle on Day 1. Participants who are eligible for retreatment will be given BOTOX on either Day 180, 210, 240, or 270 and will be followed until approximately Day 360. There may be a higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, facial photography, checking for side effects and completing questionnaires.
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Percentage of Participants who Achieve >= 2-Grade Improvement on Investigator-Rated Masseter Muscle Prominence Scale (MMPS)
Timeframe: Baseline to Day 90
Number of Participants with Adverse Events (AEs)
Timeframe: Up to approximately 12 months