Objective: This open-label extension (OLE) study evaluated the long-term safety and efficacy of repeat treatment cycles of abobotulinumtoxinA using 2 mL dilution (NCT01753336).

Background: Cervical dystonia (CD) is a chronic neurological movement disorder characterized by sustained involuntary contractions of the neck muscles, leading to disabling postures.

Method: This was an OLE of a 12-week, randomized, placebo-controlled trial. Eligible patients included adults (≥18yr) with primary idiopathic CD who completed the lead-in Week 12 (Wk12) visit or whose Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score decreased ≤15% from baseline (before first abobotulinumtoxinA administration) at lead-in Wk4. For Cycle 1 (C1), patients toxin-naïve at baseline received 500U, and non-naïve patients received 250-500U based on prior onabotulinumtoxinA dose. In C2/C3, dose adjustments were limited to ≤250U/cycle and maximal total dose limited to 1000U/cycle. Re-treatment occurred every 12-16wks, for ≤3 OLE cycles, based on clinical judgment. Endpoints included TWSTRS and safety (treatment-emergent adverse events [TEAEs]).

Results: Of 112 treated patients, 92 completed the Wk36 visit (C3-Wk12). Mean TWSTRS total score was 42.2 at baseline and decreased to 30.1 at C3-Wk12, with a total change from baseline of -11.7 at C3-Wk12. For each cycle, TWSTRS scores decreased from D1 to Wk4 and increased between Wk4 and Wk12, though the Wk12 scores remained lower than D1 scores. Mean TWSTRS scores at Wk4 and Wk12 were primarily lower for each successive cycle (no worsening to baseline). 70 patients (62.5%) reported 220 TEAEs; dysphagia, muscular weakness, and neck pain were the most frequent (10.7% each). Most TEAEs (n=156) were not considered treatment-related by investigators and none led to discontinuation or death.

Conclusion: Results were consistent with the lead-in double-blind study and showed that abobotulinumtoxinA at approved doses using 2 mL dilution remained effective and well tolerated over 4 treatment cycles, demonstrating sustained improvements within and across cycles in CD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/abobotulinumtoxina-using-2-ml-dilution-maintains-durable-functional-improvements-across-multiple-treatment-cycles/