A Study To Assess the Safety of OnabotulinumtoxinA (BOTOX) Intramuscular Injection in Adult Participants With Platysma Prominence

Phase 3, Multicenter Open-label Extension Study to Evaluate the Safety of BOTOX (Botulinum Toxin Type A) Purified Neurotoxin Complex for the Treatment of Platysma Prominence

This is a Phase 3, open-label extension study to evaluate the long-term safety of repeat BOTOX treatments in adult participants with Platysma Prominence. Participants who completed the lead-in Phase 3 Study M21-309 and met eligibility requirements could enroll in this open-label extension study.

Planned study enrollment was approximately 270 participants. Participants who met treatment criteria could receive up to 3 administrations of BOTOX. Day 1 (study entry) was the same day as Day 120/study exit visit of the lead-in Phase 3 study. The first administration of study drug could occur at the Day 1 visit, and the last administration of study drug could occur at the Day 180 visit (60 days prior to Day 240/study exit). Once a subject was enrolled in this study, monthly follow-up visits occurred.

Inclusion Criteria:

- Completion of all phases of the lead-in Phase 3 study (Screening Period, Treatment Period [randomization/treatment with 4-month follow-up visit] and Study Exit visit)

Exclusion Criteria:

• Any medical condition that may put the participant at increased medical risk with exposure to BOTOX, including diagnosed myasthenia gravis, Eaton-Lambert syndrome, amyotrophic lateral sclerosis, or any other condition that might interfere with neuromuscular function
• Participant has an anticipated need for treatment with botulinum toxin of any serotype for any indication during the study (other than study intervention)
• Anticipated need for surgery or overnight hospitalization during the study
• Females who are pregnant or breastfeeding and are considering becoming pregnant or donating eggs during the study
• Known immunization or hypersensitivity to any botulinum toxin serotype
• History of clinically significant (per investigator's judgment) drug or alcohol abuse within the last 6 months
• Tattoos, jewelry, or clothing that cannot be removed, and that obscure the target area of interest