A study of the effect of relabotulinumtoxinA on enlarged jaw muscles (masseter hypertrophy) and facial shape in adults aged 18 to 40 years.
A single group treatment, Phase 4, open-label study to investigate the effectiveness and safety of relabotulinumtoxinA for facial contouring in males/females aged 18-40 years with moderate to severe benign masseter muscle hypertrophy
Aesthetic Maxillofacial Clinic
20 participants
Jan 5, 2026
Interventional
Conditions
Summary
Botulinum toxin type A (BoNTA) is commonly used to temporarily reduce muscle size and activity without surgery. One area of interest is the masseter muscle in the lower face, which can become enlarged and cause a broader jawline. Previous studies using other BoNTA products have shown that the greatest effect occurs about three months after treatment and can last between six and twelve months. Early research with relabotulinumtoxinA (Relfydess) in facial lines suggests it may act more quickly and last longer, but it has not yet been evaluated for jaw muscle enlargement. This study will group participants based on their degree of muscle enlargement and apply treatment according to recent evidence on dosing and injection patterns. The findings may help determine the safety, effectiveness, and duration of action of Relfydess for non-surgical facial contouring.
Eligibility
Inclusion Criteria5
- Age 18 - 40 years.
- Moderate-to-severe masseteric hypertrophy
- No prior neurotoxin treatment within 6 months
- No contraindications to BoNTA
- Signed informed consent
Exclusion Criteria8
- Pregnant or breastfeeding
- History of neuromuscular disorders
- History of adverse reactions to BoNTA
- Received prior BoNTA treatment within 6 months of trial enrollment
- History of soft tissue fillers in the jawline
- History of dental/surgical procedure for lower facial shaping or masseter muscle reduction
- Unwilling or unable to adhere to post-procedure care instructions or the follow-up schedule
- Any condition that could make the patient noncompliant with the study procedures and/or study requirements, as judged by the Investigator.
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Interventions
Eligible participants will undergo an initial (baseline) assessment to measure the size and appearance of their jaw muscles. Based on this assessment participants will be placed into one of two treatment groups. Participants assessed to have Grade 4 muscle masseter hypertrophy will be put into Group 1 and participants who have Grade 5 muscle masseter hypertrophy will be put into Group 2. All participants will receive one treatment at the start of the study. The investigator will administer the treatment by intramuscular injection as follows: Group 1: will receive a total RelabotulinumtoxinA dose of 120 Units (U) administered as 60U (3 injections each of 20U) into the jaw muscle on each side of the face. Group 2: will receive a total RelabotulinumtoxinA dose of 150U, administered as 75U (5 injections each of 15U) into the jaw muscle on each side of the face. After receiving this treatment, participants will be reviewed at regular study visits - week 1, Month 1, Month 3, Month 6, Month 9 and Month 12. Participants whose jawline prominence has returned to the baseline level at the Month 6 visit will be offered an optional repeat treatment at that time. Participants will have a maximum of two treatments over the 12 month trial.
Locations(1)
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ACTRN12625001280493