Botulinum toxin type B vs. type A in toxin-naïve patients with cervical dystonia: Randomized, double-blind, noninferiority trial.

The objective of this study was to compare efficacy, safety, and duration of botulinum toxin type A (BoNT-A) and type B (BoNT-B) in toxin-naïve cervical dystonia (CD) subjects. BoNT-naïve CD subjects were randomized to BoNT-A or BoNT-B and evaluated in a double-blind trial at baseline and every 4-weeks following one treatment. The primary measure was the change in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) from baseline to week 4 post-injection. Secondary measures included change in TWSTRS-subscale scores, pain, global impressions, and duration of response and safety assessments. The study was designed as a noninferiority trial of BoNT-B to BoNT-A. 111 subjects were randomized (55 BoNT-A; 56 BoNT-B). Improvement in TWSTRS-total scores 4 weeks after BoNT-B was noninferior to BoNT-A (adjusted means 11.0 (SE 1.2) and 8.8 (SE 1.2), respectively; per-protocol-population (PPP)). The median duration of effect of BoNT-A and BoNT-B was not different (13.1 vs. 13.7 weeks, respectively; P-value = 0.833; PPP). There were no significant differences in the occurrence of injection site pain and dysphagia. Mild dry mouth was more frequent with BoNT-B but there were no differences for moderate/severe dry mouth. In this study, both BoNT-A and B were shown to be effective and safe for the treatment of toxin-naive CD subjects.