Conversion to AbobotulinumtoxinA Increases Waning Time and Efficacy for Cervical Dystonia

BackgroundSymptom 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. ObjectivesTo 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. MethodsThirty-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. ResultsCompared 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. ConclusionsOptimized 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.