Objective: To report preliminary 24-week outcomes of an open-label trial of daxibotulinumtoxinA for injection (RT002) for the treatment of isolated cervical dystonia (CD). (ClinicalTrials.gov ID: NCT02706795)

Background: Botulinum neurotoxins (BoNT) are considered first-line therapy for CD. The typical duration of beneficial effects has been reported to be about 3 months.  RT002, a novel lyophilized product of BoNT containing purified 150 kDa BoNT type A formulated with an excipient RTP004, is hypothesized to extend treatment duration.

Methods: This study enrolled 37 CD patients with the Toronto Western Spasmodic Torticollis Scale (TWSTRS)-Total score ≥20 and the TWSTRS-Severity subscale ≥15, and who were BoNT naïve or had not received BoNT within the last 6 months. With escalation of RT002 dose from up to 200 Units (U), 200-300 U, and 300-450 U depending on safety evaluation of the prior cohort, the study enrolled 12, 12 and 13 subjects respectively for the 3 cohorts. Primary efficacy endpoint was change from baseline TWSTRS-Total score at Week 4. Subjects were followed up to 24 weeks to evaluate safety and treatment duration.

Results: As of 8 December 2016, the study had follow-up data of 24 weeks for Cohort 1, 16 weeks for Cohort 2 and 4 weeks for Cohort 3. Of all 37 subjects enrolled, the mean age was 56 years, 76% were females, and mean CD duration was 7.6 years.  Mean baseline TWSTRS-Total score was 44.1 and TWSTRS-Severity score was 21.1. At Week 4, a mean reduction of 16.8 points (or 38%) in TWSTRS-Total Score, considered clinically meaningful, was observed. The median duration of effect, as defined by time since treatment till subjects losing ≥80% of improvement achieved at Week 4 in TWSTRS-Total score was > 24 weeks for Cohort 1. Treatment-related adverse events (AE’s) occurred in 35.1% of subjects, including mild, transient dysphagia (10.8%), injection site erythema (8.1%), neck weakness (5.4%).  All AE’s were mild to moderate, except for a case of severe neck pain that lasted for two days. No serious AE’s were reported. 

Conclusions: This phase 2, open-label trial provides preliminary evidence that an injection of up to 450 U of daxibotulinumtoxinA into cervical muscles appears to be generally safe and well tolerated, and results in a clinically meaningful reduction in CD symptoms with a possible extended duration of effect.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-phase-2-open-label-dose-escalating-study-to-evaluate-the-safety-and-preliminary-efficacy-of-daxibotulinumtoxina-for-injection-rt002-in-isolated-cervical-dystonia/