The First of Two One-Year, Multicenter, Open-Label, Repeat-Dose, Phase II Safety Studies of PrabotulinumtoxinA for the Treatment of Moderate to Severe Glabellar Lines in Adult Patients

Background PrabotulinumtoxinA is a 900-kDa botulinum toxin type A produced by Clostridium botulinum. Objectives The authors sought to investigate the safety of prabotulinumtoxinA for treatment of glabellar lines. Methods This was a multicenter, open-label, repeat-dose, 1-year phase II safety study. Adults with moderate to severe glabellar lines at maximum frown, as assessed by the investigator on the validated 4-point photonumeric Glabellar Line Scale (0 = no lines, 1 = mild, 2 = moderate, 3 = severe), were enrolled. On day 0, patients received an initial treatment of 20 U prabotulinumtoxinA (4 U/0.1 mL freeze-dried formulation injected into 5 target glabellar sites). On and after day 90, patients received a repeat treatment (RT) if their Glabellar Line Scale score was >= 2 at maximum frown by investigator assessment. Safety was evaluated throughout the study. Results The 352 study patients received a median total dose of 60 U, that is, 3 treatments per year. Fifty-one patients (14.5%) experienced adverse events (AEs) assessed as possibly study drug related; 11.1% experienced study drug-related AEs after the initial treatment. With each RT, progressively lower percentages of patients experienced study drug-related AEs. Six patients (1.7%) experienced study drug-related AEs of special interest: 3 eyelid ptosis (0.9%), 2 speech disorder (0.6%), and 1 blepharospasm (0.3%). Seven patients (2.0%) experienced serious AEs; none were study drug related. Of the 2393 samples tested, 2 patients (0.6%) tested positive for antibotulinum toxin antibodies at a single postbaseline visit. Conclusions The safety of RTs of 20 U of prabotulinumtoxinA for moderate to severe glabellar lines was first established in this early phase II study based on a broad range of outcomes. Level of Evidence: 2