Repeat Administration and Dose Escalation of DaxibotulinumtoxinA in Adductor Type Laryngeal Dystonia.

[OBJECTIVES] During initial comparison of DaxibotulinumtoxinA-lanm (Daxi) to botulinum toxin A (BtxA) in adductor laryngeal dystonia (AdLD) (Phase 1), Daxi administration was found to be safe and efficacious. This study sought to determine the reproducibility of Daxi results (Phase 2) and safety/results for Daxi dose escalation (Phase 3) in patients who previously had been successfully treated with Daxi.

[METHODS] Thirteen AdLD patients with consistent benefit from BtxA were enrolled in an open-label prospective clinical trial involving repeat administration and/or up-titration of Daxi dose. Duration of voice benefit (DVB) and safety of dose escalation were primary outcomes. PROMs and voice recordings were obtained pre- and post-injection.

[RESULTS] Twenty-nine total injections (21 repeat dose, 8 dose escalation) were performed in 13 patients (85% female, mean age = 60.4). No adverse events occurred, and there was no difference in EAT-10 pre- to post-injection (repeated dose p = 0.08, dose escalation p = 0.12). In patients who experienced greater benefit with Daxi, average DVB was 112.75 days, 33.5% longer than their average BtxA duration (mean = 84.2 days, p = 0.003). 54% (7/13) had longer DVB with Daxi, and 46% (6/13) had equivocal DVB compared to BtxA DVB by the end of the study. Daxi DVB was comparable to an earlier study, demonstrating reproducibility of Daxi injection results (p = 0.332, SD = 13.6 days).

[CONCLUSIONS] Our results were variable but showed reproducible results with Daxi, with overall longer DVB with Daxi in 42.8% of total injections, with an average of 33.5% longer DVB than BtxA in a cohort of known Daxi-responsive patients. Daxi dose escalation did not result in significant dysphagia or adverse events. Further studies are needed to determine the clinical utility of Daxi in the treatment of AdLD.