SEATTLE – (MS), according to research presented at the annual meeting of the Consortium of Multiple Sclerosis Centers. The regimen is well tolerated.
Spasticity is common in MS, and the traditional treatment is oral baclofen, a GABAB receptor agonist. Therapeutic doses of baclofen may cause side effects that decrease adherence, however. Arbaclofen is a more active R-enantiomer of baclofen, which is a racemic mixture. Arbaclofen extended-release (ER) tablets enable twice-daily administration, which reduces dosing frequency and may decrease the rate of adverse events.
Daniel Kantor, MD, a faculty member at Florida Atlantic University in Boca Raton, and colleagues conducted a multicenter, double-blind, parallel-group study to compare the efficacy and safety of arbaclofen ER with those of placebo and baclofen in patients with MS-related spasticity. They randomized adults in North America and Eastern Europe in equal groups to arbaclofen ER (20 mg b.i.d.), baclofen (20 mg q.i.d.), or placebo. The dose was titrated over 2 weeks, and participants subsequently entered a 12-week maintenance phase. The study’s two primary endpoints were the mean change in Total Numeric-Transformed Modified Ashworth Scale for the most affected limb (TNmAS-MAL) and Clinician Global Impression of Change (CGIC) from baseline through the maintenance period.
Dr. Kantor and colleagues randomized 341 patients in their study. Of this population, 57.5% had relapsing-remitting MS, 38.4% had secondary progressive MS, 2.6% had primary progressive MS, and 0.9% had progressive relapsing MS. Thirteen patients from one site were excluded from analysis after study completion when an audit found irregularities. The mean baseline TNmAS-MAL score was 7.93 in the arbaclofen ER group, 7.75 in the baclofen group, and 7.55 in the placebo group. At the end of the maintenance period, the mean decrease in TNmAS-MAL score was larger with arbaclofen ER than with placebo (least-squares mean [LSMean] −2.90 vs. −1.95). In addition, CGIC was significantly improved for arbaclofen ER, compared with placebo (LSMean 1.00 vs. 0.52).
Furthermore, the change in MS Spasticity Scale (MSSS-88) was greater in the arbaclofen ER group than in the placebo group (−30.1 vs. −16.7). Results on the TNmAS, CGIC, and MSSS-88 did not significantly differ between arbaclofen ER and baclofen. Drowsiness and dizziness were less common in the arbaclofen ER group than in the baclofen group. A total of 63 (57.3%) patients receiving arbaclofen ER, 82 (72.6%) receiving baclofen, and 59 (50.0%) receiving placebo reported treatment-emergent adverse events. The most common adverse events were somnolence, asthenia, and muscle weakness.
The study did not have funding support. Dr. Kantor reported having received consulting fees from AbbVie, Actelion, Bayer, Biogen, Celgene, EMD Serono, Genentech/Roche, Mylan, Novartis, Osmotica, and Sanofi Genzyme.