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Efficacy and Safety of a Tailored Dosing Strategy with High-Dose IncobotulinumtoxinA at Flexible Injection Intervals
Akira Tamagawa1, Masahiro Horiuchi2, Takenori Abe3
1Tamagawa Clinic, Yokohama 241-0814, Japan.
Background:
This prospective, multicenter, open-label, single-arm study (jRCT2031230690) evaluated the efficacy and safety of a tailored dosing strategy of incobotulinumtoxinA, including high doses (up to 500 U) and flexible injection intervals (as short as 6 weeks), in Japanese patients with cervical dystonia (CD).
Methods:
Of 30 enrolled patients, Group A included 27 patients with idiopathic CD for the primary evaluation of efficacy and safety, whereas Group B included 3 patients with tardive dyskinesia (cervical) or tardive CD for exploratory safety assessment. Patients received up to seven injection cycles of incobotulinumtoxinA (120-500 U) over 48 weeks, with minimum 6-week intervals. The primary endpoint, evaluated in Group A, was the change in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score from baseline to Week 4 after the first injection.
Results:
Using a mixed model for repeated measures, the least squares mean ± standard error of the change was -11.0 ± 1.77 (95% confidence interval: -14.6, -7.3). The primary efficacy endpoint was achieved in Group A. Due to the small sample size (n = 3), efficacy in Group B was evaluated only for exploratory purposes, although safety findings were broadly consistent with those in Group A. The overall safety profile was consistent with previous studies. Across the study, the most common related adverse events were dysphagia (33.3%) and muscular weakness (22.2%) in Group A and dysphagia (33.3%) in Group B. All cases of dysphagia were mild to moderate in severity and transient, with no apparent dose- or injection interval-related trend observed.
Conclusions:
IncobotulinumtoxinA was associated with improvements in symptoms and manageable safety profile at high doses and flexible injection intervals in Japanese patients with CD. While these findings suggest a potential treatment option for individualized dose optimization, the absence of a control group and the exploratory nature of the assessment in Group B necessitate cautious interpretation.
