This study is an open-label, single-center, single-arm, longitudinal clinical trial designed to evaluate the use of daxibotulinumtoxinA (DAXI) for injection in twenty adult participants with blepharospasm (BSP). Each subject will be eligible to receive between two and three treatment cycles with DAXI over a twelve-month period. The timing of reinjection will depend on each participant's duration of benefit, as determined using the Blepharospasm Severity Tracker Form (BSTF). Treatments must be spaced at least ninety days apart but not more than one hundred eighty days. Participants will decide when to receive another injection and may use topical lidocaine cream, cooling spray, or other anesthetic methods to reduce pain during the procedure.
The study will enroll adults of any race or gender, aged eighteen or older, who are in generally good health and have a clinical diagnosis of blepharospasm. Eligible participants may have either isolated blepharospasm, which could be focal or part of segmental or generalized dystonia, or blepharospasm as a complication of a parkinsonian condition. To qualify, participants must have a baseline blepharospasm severity rating of at least two points on the Blepharospasm Severity Rating Scale (BSRS) and must already be receiving either onabotulinumtoxinA or incobotulinumtoxinA with less than twelve weeks of benefit from that treatment.
For each injection session, the study drug will be prepared by the injector or a qualified staff member by diluting one milliliter of Bacteriostatic Sodium Chloride Injection (0.9%) with one hundred units of DAXI to create a final concentration of ten units per 0.1 milliliter for intramuscular injection. The specific dose, muscles injected, and number of injection sites will be determined by the injector. Only four muscles may be treated: the corrugators, procerus, orbicularis oculi, and nasalis. Use of electromyography or ultrasonography for guidance is optional but generally unnecessary for facial injections.
The initial DAXI dose will be based on the participant's previous injection cycle. Those currently treated with onabotulinumtoxinA will convert on a one-to-one unit basis, while those treated with incobotulinumtoxinA will use a 1.5:1 conversion ratio, meaning 1.5 units of incobotulinumtoxinA is equivalent to one unit of DAXI. If the previous dose resulted in excessive weakness or related side effects such as eyelid drooping, double vision, or dry eye, dosing will be adjusted accordingly. Subsequent DAXI dosing may be further modified at the injector's discretion, and efforts will be made for each subject to be treated by the same injector throughout the study.
Following each treatment, efficacy will be evaluated at the time of peak response, which typically occurs about one month after injection. The first DAXI administration occurs around day ninety-five (visit three), and this timing determines when follow-up evaluations, usually by remote visit, are performed. Future injection cycles will follow similar timing, although exact intervals will vary depending on individual responses. The overall study period for each subject spans roughly one year, ending with either an end-of-study or early-termination visit between days 365 and 460.
The primary measure of efficacy is the median time to reinjection, serving as an indicator of the duration of DAXI's therapeutic effect. Secondary outcomes include the participant's perceived duration of benefit, changes in blepharospasm severity, quality-of-life improvements, and overall treatment satisfaction. Specific evaluation tools include the Blepharospasm Severity Tracking Form (BSTF), Blepharospasm Severity Rating Scale (BSRS), Craniocervical Dystonia Questionnaire (CDQ-24), Clinical Global Impression of Change (CGIC), Patient Global Impression of Change (PGIC), and a Treatment Satisfaction Questionnaire.
Safety monitoring is a critical component of the trial. Assessments will include pregnancy testing for women of childbearing potential, physical and neurological examinations, the Columbia-Suicide Severity Rating Scale (C-SSRS), vital signs, and inspection of injection sites. Investigators will also record concomitant medications and monitor all adverse events, including any deemed to be of special interest.
