Spinal and Bulbar Muscular Atrophy

Background: SBMA is an inherited chronic disease. It affects males in mid to late adulthood. It causes slowly progressive weakness of muscles and hand tremors. Researchers want to learn more about the effects of SBMA. Objective: To identify measurements that change over time in SBMA, including tests of muscle strength and function, as well as measurements of muscle and fat size. Eligibility: Men over the age of 18 both with and without a history of SBMA. Design: Participants will have a medical history, physical exam, and blood and urine tests. They will have neuromuscular ultrasound. They will have a lumbar puncture to obtain spinal fluid. For this, a needle will be inserted into the spinal canal in the lower back. Participants will have muscle strength and function tests. These tests may include pushing, pulling, rising from a chair and sitting back down, and/or walking. During these tests, they may wear an accelerometer (activity tracker) on their wrist. Participants will get an activity tracker to wear on their wrist for 10 days at home every 3 months. Participants with SBMA will also have lower limb magnetic resonance imaging (MRI) and optional whole-body MRI. They will have lung function tests. They will have speech and swallow tests. They will complete questionnaires. They may have optional body scans to measure bone density and lean body mass. They may have optional muscle biopsies. For biopsies, a needle will be used to take a small piece of muscle from the leg. Participants with SBMA will have 5 study visits over 2 years (every 6 months). Participants without SBMA will have 1 study visit.

The purpose of this clinical trial is to evaluate the efficacy and safety of mexiletine hydrochloride in patients with spinal and bulbar muscular atrophy. The main questions it aims to answer are: Does mexiletine hydrochloride improve the ALSFRS-R score in spinal and bulbar muscular atrophy patients? Participants will: Take mexiletine hydrochloride or a placebo every day for 3 months Visit the hospital once every 4 weeks for evaluations.

There is no cure to arrest or delay SBMA progression. It is estimated that \~1000 individuals are affected by SBMA in Italy at any given time (prevalence: 1.5/100000) with an annual incidence of 0.19/100000 males. Here, we are going to test the potential of beta2-agonist stimulation on muscle as a therapeutic avenue for SBMA. We have provided pre-clinical evidence that β-agonist stimulation may be a therapeutic strategy for SBMA. Moreover, we have shown that beta2-agonists are effective in improving motor function without relevant adverse events in a small cohort of SBMA patients. To establish safety and efficacy of clenbuterol as a cure for SBMA, we are conducting a multicenter, phase II, randomized, double-blind, parallel-group, single dose, placebo-controlled trial. Indeed, based on our preliminary data, some concerns remain to be addressed.