A multicenter, randomized, double-blind, parallel-group, placebo-controlled study in Japanese patients with post-stroke lower limb spasticity was conducted in 19 Japanese medical institutions in Japan between May 2007 and April 2008. The study was approved by the Institutional Review Board and was conducted according to the Declaration of Helsinki and the GCP; all patients signed informed consent.
Patients
Male or female patients aged 20–80 years and weighing at least 50 kg were eligible if they had had a stroke at least 6 months prior to treatment and had equinus deformity (plantar flexion of the ankle) as demonstrated by a score of >3 for ankle flexors on the Modified Ashworth Scale (MAS) [11].
Exclusion criteria were bilateral hemiplegia or quadriplegia; fixed contractures in the ankle; profound atrophy of the muscles to be injected; prior treatment with surgery, phenol/ethanol block, muscle afferent block (MAB), intrathecal baclofen, or any botulinum toxin serotype; and current use of peripheral muscle relaxants. Women were excluded if they were pregnant, lactating, potentially pregnant, or planning to become pregnant during the course of the study.
Procedures
The primary study objective was to confirm the superior efficacy of a single treatment of BoNTA 300 U over placebo in patients with post-stroke lower limb spasticity using the MAS ankle score. MAS is widely used for the assessment of muscle tone and spasticity in lower limbs [5, 7–10]. Investigators were trained in the procedures to assess the MAS ankle score at the study start. Patients were assessed in the prone position, and the ankle was examined from the edge of the examination table for the MAS ankle score. The study included a screening examination (2–4 weeks before the treatment), a single treatment, and a 12-week follow-up period. Patients visited the center at screening, on the treatment day, and at weeks 1, 4, 6, 8, and 12 for specified examinations, observations, and assessments.
Treatments
Investigational drug
One vial of BoNTA (GSK1358820, BOTOX®, Allergan, Inc., Irvine, CA) contains 100 U of a specific formulation (Formulation 9060X) of botulinum toxin type A, 0.5 mg human serum albumin, and 0.9 mg sodium chloride per vial, which requires reconstitution prior to injection. The indistinguishable placebo contained 0.9 mg sodium chloride per vial. Each vial was reconstituted with 8 ml of non-preserved physiological saline resulting in a final concentration of 1.25 U BoNTA per 0.1 ml or placebo.
Drug dose and muscle selection
Drug dose and muscle selection was based on the Australian package insert [12]. Patients were randomly assigned to receive a single injection of 300 U of BoNTA or placebo and were injected with 75 U of BoNTA or placebo per muscle into each of the following: medial head of the gastrocnemius, lateral head of the gastrocnemius, and soleus muscle and tibialis posterior muscle (divided into three sites per muscle). Patients in the placebo group received the same volume of placebo solution into the same number of injections/muscles.
An EMG or a nerve stimulator, and an EMG injection needle were used to identify the proper muscles and facilitate injection in all patients.
Randomization
After screening, each eligible patient was randomized 1:1 to receive either BoNTA or placebo injection on the treatment day. The person responsible for randomization prepared a randomization code table, and it was concealed from all investigators and all study personnel until data collection and analysis were completed.
Assessments
Efficacy
MAS
The muscle tone of the ankle was assessed by the investigator using the MAS [11] at screening, pre-injection on the treatment day (baseline), and at weeks 1, 4, 6, 8, and 12 or at study withdrawal.
Gait pattern scale (physician’s rating scale)
The investigator assessed the gait pattern while the patient walked 10 m using the Physician’s Rating Scale [13] (Table 1) pre-injection on the treatment day and at weeks 1, 4, 6, 8, and 12 or at study withdrawal. This scale of -1 (worst) to 9 (best) based on three parameters (initial foot contact, foot contact at midstance, and gait-assisting devices) is an observational gait scale originally developed by Koman et al. [14]., modified by Corry [15], and subsequently modified by Boyd et al. [13]. In this study, gait parameters that were suitable for the intended purpose were selected from the original parameters.
Table 1 Gait pattern scale (Physician’s Rating Scale)
Speed of gait
The investigator or clinical research coordinator measured the time (seconds) the patient took to walk 10 m straight ahead pre-injection on the treatment day and at weeks 1, 4, 6, 8, and 12 or at study withdrawal.
Clinical global impression (CGI)
At screening, pre-injection on the treatment day, and at weeks 1, 4, 6, 8, and 12 or at study withdrawal, the global impression of functional disability on the visit day was assessed using the Numeric Rating Scale, with -5 indicating worst possible and 5 best possible rating, by the investigator, the patient, and the physical or occupational therapist.
Safety
Adverse events were recorded throughout the study. Laboratory tests were performed at screening and at week 12 or at study withdrawal. Vital sign assessments (pulse rate and blood pressure) and 12-lead electrocardiography were performed on the treatment day and week 12 or at study withdrawal.
Data analysis
The sample size was chosen based on the previous study [6]. Assuming a mean difference of 5 points in the AUC for the MAS ankle score change between BoNTA and placebo based on the results and a SD value of 7.5 for both treatments, 49 subjects per group were be required to provide 90% power at the 5% level of significance (two-sided) using t-test to achieve superiority over placebo. Assuming approximately 20% of dropouts, the sample size of 60 subjects per group (120 subjects in total) was chosen.
Efficacy data were analyzed using the full analysis set (FAS), defined as all randomized patients that received study treatment and had at least one MAS ankle assessment after treatment.
The AUC of the change from baseline in the MAS ankle score was the primary endpoint. Considering the differences of individual peak efficacy, the assessment over the treatment period by AUC as summary index was considered to provide more accurate evaluation than assessment at a specific time point [16–18], resulting in more accurate evaluation of efficacy of BoNTA compared to placebo. MAS ankle scores at individual time points were also evaluated. For each patient, the change from baseline (the day of the treatment) in the MAS ankle score at each time point was calculated; “1+” was analyzed as score 1.5. Changes from baseline (vertical axis) were plotted against time (horizontal axis), and the area under the resultant curve was obtained. A decrease from baseline resulted in a negative (−) AUC value, while an increase from baseline resulted in a positive (+) AUC value. The difference in the mean AUC between the BoNTA group and the placebo group was tested using a t-test. The point estimate and the 95% CI of the mean group difference were also calculated.
Changes from baseline in the MAS ankle score, the Physician’s Rating Scale, the speed of gait, and the CGI at each time point were summarized by group; the Wilcoxon test was used to determine statistical differences between the BoNTA group and the placebo group.
Safety data were analyzed for the safety population (SP), defined as all patients that received study treatment.