| Summary: | <p><strong>Background:</strong> To determine whether botulinum toxin treatment history affected the outcomes of a study comparing the safety and efficacy of incobotulinumtoxinA with placebo in subjects with cervical dystonia (CD).</p><p><strong>Methods: </strong>This was a prospective, double‐blind, randomized, placebo‐controlled, multicenter trial in botulinum toxin‐treated or toxin‐naïve CD subjects. Subjects received a fixed dose of either 120 U or 240 U of incobotulinumtoxinA or placebo. The primary outcome measure was change from baseline to Week 4 in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score. Treatment‐emergent adverse events (TEAEs) were also evaluated. This report represents a subgroup analysis of botulinum toxin‐treated or toxin‐naïve subjects.</p><p><strong>Results:</strong> Participants (N = 233; 38.6% toxin‐naïve) had a mean age of 52.8 years. IncobotulinumtoxinA significantly improved TWSTRS total scores from baseline to Week 4 in both dose groups versus placebo, and the improvement persisted through the end of the study (≤20 weeks). Both the previously toxin‐treated and toxin‐naïve subjects demonstrated significant improvements in TWSTRS total scores at Week 4 compared to baseline. The most frequent TEAEs in the incobotulinumtoxinA groups were dysphagia, neck pain, and muscular weakness, which were generally mild. TEAEs were more common in the 240 U group and toxin‐naïve subjects. <strong>Discussion:</strong> Overall, incobotulinumtoxinA was safe and effective in CD, regardless of toxin therapy history. A lower starting dose may be better tolerated among toxin‐naïve subjects without sacrificing efficacy.</p>
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