Pilot trial of clenbuterol in spinal and bulbar muscular atrophy

Objective: To test the efficacy and tolerability of clenbuterol in patients with spinal and bulbar muscular atrophy (SBMA). Methods: Twenty patients with a diagnosis of SBMA were given oral clenbuterol (0.04 mg/d) for 12months. The primary efficacy end point was the change from baseline of the walking distance covered in 6 minutes at 12 months. Secondary end points included the change over time in muscle strength assessed with the Medical Research Council scale, the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R), and forced vital capacity values. Safety was assessed by a series of laboratory and instrumental tests, as well as reporting of adverse events. Results: Sixteen patients completed the study. There was a significant and sustained increase in walking distance covered in 6 minutes and forced vital capacity between the baseline and the 12-month assessments (p < 0.001). No differences were recorded in Medical Research Council or ALSFRS-R scores between baseline and follow-up assessments. Serious side effects, including those on heart function, were absent. A significant increase in serum creatine kinase levels was observed. Conclusions: Our findings suggest a positive effect of clenbuterol on SBMA disease progression. Classification of evidence: This study provides Class IV evidence that clenbuterol is effective in improving motor function in SBMA.