Current botulinum toxin labeling indicates injections once every 12 weeks but few studies have assessed the treatment interval after repeated injections. In a recent double-blind (DB) study followed by an open-label (OL) extension abobotulinumtoxinA (aboBoNT-A, Dysport^®) was efficacious and demonstrated a favourable safety profile in adult patients with upper limb spasticity (ULS) after single and repeated injections (Gracies et al. Lancet Neurol 2015; Brashear et al. Am Acad Neurol 2016). This additional analysis focuses on the retreatment intervals after repeated injections of aboBoNT-A.

Phase III, international, multicentre, DB, single-treatment study of aboBoNT-A in adults with ULS, followed by a long-term OL extension study with a maximum of 4 additional treatment cycles over a maximum of 18 months. Retreatment was per investigator's clinical judgment and possible at weeks 12, 16, 20, and 24.

Among the subjects who received aboBoNT-A in the DB study and were treated in cycle 1 of the OL extension, 37% were re-injected at week 16 or later (17% at week 16, 10% at week 20, 10% at week 24 or later). For those who received a second cycle of treatment in the OL phase, 35% of subjects were re-injected at week 16 or later (20% at week 16, 7.0% at week 20, 8% at week 24 or later). For those who received a third cycle of treatment in the OL phase, 24% of subjects were re-injected at week 16 or later (19% were retreated at week 16, 3% at week 20, 2% at week 24 or later).

These data show that 24% to 37% of subjects did not require reinjection before week 16 across multiple cycles. This long duration of clinical effect leads to longer intervals between injections, and thus may reduce the burden associated with frequency of injections for patients and their caregivers/families. This also highlights the needs for a tailored approach in the treatment of patients with ULS.