Impact of DaxibotulinumtoxinA for Injection on Brow Position and Frontalis Muscle Activity Following Treatment of Glabellar Lines

Background: Botulinum toxin type A (BoNTA) injections for the treatment of facial lines may lead to pleasant or undesirable changes in eyebrow height and position. Objectives: The aim of this study was to evaluate the impact of glabellar injection of DaxibotulinumtoxinA for Injection (DAXI), a novel BoNTA formulation, on eyebrow position and frontalis activity. Methods: This study involved the post hoc analysis of adult patients from the Phase 2a forehead lines (FHL, N = 60) and open-label safety (OLS, N = 175) studies who received a single dose of DAXI 40 U to the glabella and for whom facial photographs were taken at rest and at maximum eyebrow elevation. Median vertical and horizontal displacement of the brows and median forehead strain (an objective quantitative assessment of frontalis activity) from baseline to 2 weeks after glabellar DAXI injection were measured. Results: Two weeks after glabellar DAXI injection, vertical eyebrow movement (at rest) of the lateral brow was observed. In both studies, vertical movement was greatest in the lateral (0.6-0.9 mm) and mid (0.5-0.7 mm) brow regions; movement in the medial brow was negligible (0-0.23 mm). In both studies, a graded reduction in forehead strain was observed 2 weeks post glabellar DAXI injection, with the greatest reduction being in the lower segment (FHL, -73%; OLS, -82%). Treatment with DAXI showed improvements in FHL wrinkle severity. Conclusions: Glabellar injection of DAXI showed a positive reduction in dynamic frontalis activity that maintained or had a positive effect on eyebrow position. Vertical movement of the brow was suggestive of an improved eyebrow shape with a mild lateral arch.