Long-term safety of repeated administrations of a new formulation of botulinum toxin type A in the treatment of glabellar lines: interim analysis from an open-label extension study.

Background: A new formulation of botulinum toxin type A (BoNT-A) (Dysport) has recently been approved in the United States for the treatment of glabellar lines.
Objective: We sought to evaluate the long-term safety of repeated administrations of this BoNT-A formulation.
Methods: In all, 768 individuals (1500 planned) from phase III clinical trials received as many as 6 repeated treatments of open-label BoNT-A (50 U) over 17 months, with a minimum of 85 days between treatments. Participants received a telephone call at day 7 postinjection to check for adverse event (AE), with clinical evaluations on days 14 and 30, and monthly until retreatment, study completion, or early termination. Safety end points were AEs, changes in vital signs, and assessment of serum-neutralizing antibodies to BoNT-A.
Results: Of the 285 participants reporting at least one treatment-emergent AE at the interim analysis cutoff, only 74 (26%) reported at least one possibly or probably related event after 2259 treatments with BoNT-A. The incidence of treatment-emergent AEs around the injection sites and eyes was low (< or = 3%). Ten participants (1%) experienced 10 instances of ptosis. No participants developed neutralizing antibodies to BoNT-A or clinically significant changes in vital signs.
Limitations: This is an interim analysis of a larger multicenter extension study.
Conclusions: Multiple treatments with BoNT-A (50 U) over 17 months were well tolerated.