Repeat Administration and Dose Escalation of <scp>DaxibotulinumtoxinA</scp> in Adductor Type Laryngeal Dystonia

ABSTRACT 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. Level of Evidence 3.