IncobotulinumtoxinA: A Review in Upper Limb Spasticity

Intramuscular incobotulinumtoxinA (Xeomin(®)) is indicated for the treatment or improvement of adult patients with upper limb spasticity (featured indication), cervical dystonia, blepharospasm and glabellar lines. It is a highly purified formulation of botulinum toxin type A that inhibits acetylcholine signalling at neuromuscular junctions, reducing muscle hypertonia. This narrative review discusses the clinical use of incobotulinumtoxinA in adults with upper limb spasticity and summarizes its pharmacological properties. In single-treatment phase 3 trials, compared with placebo, incobotulinumtoxinA treatment improved muscle tone, global spasticity, functional spasticity-related disability and some aspects of carer burden in adults with upper limb spasticity. These beneficial effects of incobotulinumtoxinA on muscle tone were generally maintained in extension studies, in which up to five additional incobotulinumtoxinA treatments were administered. Functional spasticity-related disability and carer burden were also reduced during longer-term incobotulinumtoxinA treatment. IncobotulinumtoxinA was generally well tolerated in clinical trials, with relatively few patients experiencing treatment-related adverse events, most of which were of mild to moderate intensity. No neutralizing antibodies that would potentially cause secondary nonresponse against incobotulinumtoxinA were detected after single and multiple treatments in these trials or in phase 3 and 4 trials of incobotulinumtoxinA in other indications, which may be an advantage of this purified formulation. Further research would help to more fully determine the impact of neurotoxin purification in terms of reducing the potential risk of immunogenic responses during long-term treatment. Hence, incobotulinumtoxinA is a useful treatment option for upper limb spasticity in adult patients.

Safety and efficacy of incobotulinumtoxinA as a potential treatment for poststroke spasticity

Spasticity is a common disabling symptom for several neurological conditions. Botulinum toxin type A injection represents the gold standard treatment for focal spasticity after stroke showing efficacy, reversibility, and low prevalence of complications. In recent years, incobotulinumtoxinA, a new Botulinum toxin type A free of complexing proteins, has been used for treating several movement disorders with safety and efficacy. IncobotulinumtoxinA is currently approved for treating spasticity of the upper limb in stroke survivors, even if several studies described the use also in lower limb muscles. In the present review article, we examine the safety and effectiveness of incobotulinumtoxinA for the treatment of spasticity after stroke.

Clinical and pharmacological properties of incobotulinumtoxinA and its use in neurological disorders

Background

IncobotulinumtoxinA (Xeomin^®) is a purified botulinum neurotoxin type A formulation, free from complexing proteins, with proven efficacy and good tolerability for the treatment of neurological conditions such as blepharospasm, cervical dystonia (CD), and post-stroke spasticity of the upper limb. This article provides a comprehensive overview of incobotulinumtoxinA based on randomized controlled trials and prospective clinical studies.

Summary

IncobotulinumtoxinA provides clinical efficacy in treating blepharospasm, CD, and upper-limb post-stroke spasticity based on randomized, double-blind, placebo-controlled trials with open-label extension periods (total study duration up to 89 weeks). Adverse events were generally mild or moderate. The most frequent adverse events, probably related to the injections, included eyelid ptosis and dry eye in the treatment of blepharospasm, dysphagia, neck pain, and muscular weakness in patients with CD, and injection site pain and muscular weakness when used for treating spasticity. In blepharospasm and CD, incobotulinumtoxinA was investigated in clinical trials permitting flexible intertreatment intervals based on the individual patient’s clinical need; the safety profile of intervals shorter than 12 weeks was comparable to intervals of 12 weeks and longer. There were no cases of newly formed neutralizing antibodies during the Phase III and IV incobotulinumtoxinA trials. Phase III head-to-head trials of incobotulinumtoxinA versus onabotulinumtoxinA for the treatment of blepharospasm and CD have demonstrated therapeutic equivalence of both formulations. Additional Phase III trials of incobotulinumtoxinA in conditions such as lower-limb spasticity, spasticity in children with cerebral palsy, and sialorrhea in various neurological disorders are ongoing.

Conclusion

IncobotulinumtoxinA is an effective, well-tolerated botulinum neurotoxin type A formulation. Data from randomized clinical trials and further observational studies are expected to help physicians to optimize treatment by tailoring the choice of formulation, dose, and treatment intervals to the patient’s clinical needs.