Long-Term Safety and Efficacy of Repeat Treatments with DaxibotulinumtoxinA in Cervical Dystonia: Results from the ASPEN-Open-Label Study.

Background: DaxibotulinumtoxinA (DAXI), a novel botulinum neurotoxin (BoNT) formulation, was shown to be safe, effective, and long-lasting in the treatment of cervical dystonia (CD) over one treatment cycle in the phase 3, randomized, placebo-controlled ASPEN-1 trial.

Objectives: To evaluate the safety, immunogenicity, and efficacy of repeat DAXI treatments for CD over 52 weeks in the phase 3, open-label ASPEN-OLS (NCT03617367).

Methods: Adults with moderate-to-severe CD (Toronto Western Spasmodic Torticollis Rating Scale [TWSTRS] score ≥20) initially received DAXI 125U or 250U based on treatment history and investigator judgment. Retreatment could be titrated (50U-75U) each cycle (maximum 300U) for up to four cycles over 52 weeks. Assessments were conducted at Week 4, 6, 12, and every 4 weeks until retreatment.

Results: In all, 357 subjects received ≥1 dose of DAXI; most subjects (68.9%) received 250U during Cycle 1. Subjects most commonly received three (47.3%) or two (26.6%) treatments over 52 weeks. The average dose increased with successive cycles (Cycle 2: 239U, Cycle 3: 256U, Cycle 4: 270U). Mean (SD) change in TWSTRS score from baseline increased from -15.4 (10.3) in Cycle 1 to -19.9 (13.6) in Cycle 4. Median duration of effect was 20.1 weeks (Cycle 1, 2). No trend was observed between exposure to DAXI and any safety signals or antibody events. The most frequently reported treatment-related adverse events per treatment were muscular weakness (4.9%), injection-site pain (4.2%), and dysphagia (3.9%).

Conclusion: DAXI was safe and efficacious over repeated treatments in adults with CD. Adverse event rates were similar to or potentially lower compared with conventional BoNTs.