Improvement of Lower Facial Shape After Treatment With OnabotulinumtoxinA: Secondary Results From a Phase 2 Dose Escalation Study.

Summary

In a phase 2 randomized, placebo-controlled trial (n=187), intramuscular onabotulinumtoxinA (24–96 U) significantly reduced lower facial width and mandibular angle at day 90 versus placebo (P<0.001), with effects persisting through day 180. Investigators’ MMPS ratings and patient-reported psychosocial impact and satisfaction also improved.

Key Findings

• All onabotulinumtoxinA doses (24, 48, 72, 96 U) reduced lower facial width and mandibular angle versus placebo at day 90 (P<0.001).
• Benefits in facial shape metrics persisted to day 180.
• Improved MMPS grades, reduction in MMP signs, and higher satisfaction and psychosocial outcomes were observed at day 90.

Clinical Implications

Supports onabotulinumtoxinA as an effective option for masseter muscle prominence to achieve a slimmer lower face with benefits lasting up to 6 months; informs dose ranges and outcome measures for practice.

Limitations

• Phase 2 sample and demographics (≈80% Asian, 82% female) may limit generalizability.
• Safety and optimal dosing beyond 180 days were not established.

Future Directions

Conduct phase 3 trials with diverse populations, longer follow-up, and head-to-head dosing regimens; integrate 3D morphometrics and patient-reported outcomes as standardized endpoints.