A Mixed Treatment Comparison (Mtc) To Compare The Efficacy Of Botulinum Toxin Type A Treatments For Cervical Dystonia

Objective: This research was conducted to provide a systematic pairwise comparison of all commercially available botulinum neurotoxin (BoNT) type A treatments for cervical dystonia (CD) in the US: AbobotulinumtoxinA, OnabotulinumtoxinA and IncobotulinumtoxinA, as there is a lack of direct head‐to‐head clinical trial evidence. Pairwise efficacy comparisons were performed based on clinical results in the public domain. Design: Multi‐armed, randomized, controlled trials (RCT) identified using a Systematic Literature Review. Setting: Mixed Treatment Comparison using a Bayesian hierarchical model allowing indirect comparison of the efficacies of the interventions. Participants: 1004 subjects randomly assigned to the AbobotulinumtoxinA (n=256), OnabotulinumtoxinA (n=347), IncobotulinumtoxinA (n=159) or Placebo (n=242) groups. Interventions: Botulinum toxins AbobotulinumtoxinA, OnabotulinumtoxinA and IncobotulinumtoxinA. Main Outcome Measures: The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score was the efficacy outcome for assessment Results or Clinical Course: The systematic literature review identified 6 RCTs with a total of 14 arms. The network of identified RCTs formed a linear series of "steps" which facilitated the comparison of all BoNT type A treatments of interest. Due to the limitation of available clinical data, this study only investigated the main effect of toxin treatments without explicitly considering potential confounding factors such as gender and formulation differences. There was reasonable agreement between the number of unconstrained data points, residual deviance and pair‐wise results, suggesting a coherent network. The results for TWSTRS total scale change from baseline for all treatments were the following: Placebo (mean ‐4.15, SE 1.323), AbobotulinumtoxinA (mean ‐12.37, SE 1.729), OnabotulinumtoxinA (mean ‐12.12, SE 1.839) and IncobotulinumtoxinA (mean ‐10.37, SE 1.902); where a negative number indicates symptom improvement. Conclusions: Consistent with the previously reported model, this MTC analysis confirms that all BoNT type A treatments were effective compared to placebo in CD without significant efficacy differences between AbobotulinumtoxinA, OnabotulinumtoxinA and IncobotulinumtoxinA.