Conversion to AbobotulinumtoxinA Increases Waning Time and Efficacy for Cervical Dystonia

BACKGROUND: Symptom re‐emergence before re‐injection negatively impacts cervical dystonia (CD) patients receiving botulinum toxin type A (BoNT‐A) therapy. Longer waning time is associated with abobotulinumtoxinA (abo‐BoNT‐A) as compared to onabotulinumtoxinA (ona‐BoNT‐A)/incobotulinumtoxinA (inco‐BoNT‐A) formulations. OBJECTIVES: To compare waning time and treatment outcomes when chronically injected CD patients experiencing early waning despite being optimized on BoNT‐A (ona‐BoNT‐A/inco‐BoNT‐A) were converted to abo‐BoNT‐A. METHODS: Thirty‐three chronically injected CD participants with a waning time of ≤8 weeks were converted to abo‐BoNT‐A (1:2.5 dose ratio) for three injections every 12‐weeks. The second and third injection patterns were kinematically optimized. Participants were converted back to their original BoNT‐A for the fourth injection (1:2.5) using the same third abo‐BoNT‐A pattern. Participant‐perceived waning times were collected post‐injections. Clinical scales (Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)) and kinematic measures were collected 12‐weeks post‐injection and at three peak effect time‐points. RESULTS: Compared to baseline, waning time (12–22 days) significantly increased following all abo‐BoNT‐A treatments (P < 0.005) but was not significantly different at the fourth injection (original BoNT‐A reconversion). TWSTRS sub‐scores significantly reduced following all abo‐BoNT‐A treatments (P < 0.0001) and at peak effect following the third injection compared to original BoNT‐A. Dysphagia and muscle weakness were reported and comparable to safety of original BoNT‐A formulations. CONCLUSIONS: Optimized patients experiencing waning had significant improvement in the peak benefit as well as the duration of effect when converted to abo‐BoNT‐A. This effect was toxin dependent as reconversion to the original BoNT‐A using the kinematically optimized pattern failed to produce an improvement in waning.