Pilot Study Exploring the Physiologic, Pharmacodynamic, and Clinical Responses of Skeletal Muscle in Patients With Spinal Muscular Atrophy Treated With SMN-Directed Therapies
In this observational study, researchers are looking at the effects of spinal muscular atrophy (SMA) drugs on the muscles and nerve cells in patients with SMA. Primary Objectives * To evaluate the feasibility and reliability of performing MR functional imaging in exercising muscle in patients with SMA. * To evaluate patients with SMA types 2 and 3 at baseline and longitudinally at 6 and 12 months Secondary Objectives * To describe the MR functional bioenergetics response in the leg muscles in four potential groups of patients with spinal muscular atrophy: untreated, actively treated with nusinersen (Spinraza®) or onasemnogene abeparvovec (Zolgensma®), actively treated with risdiplam (Evrysdi®), and switching from Spinraza or Zolgensma to Evrysdi. * To identify changes in motor function in patients with SMA types 2 and 3 who initiate treatment with risdiplam. * To obtain biomarkers in blood, urine, and muscle tissue to provide proof-of-concept support for risdiplam effect on skeletal muscle. * To obtain quality of life and disability data from participants in this study.
• Genetic confirmation of SMA with homozygous deletion of SMN1 or compound heterozygous deletion/mutation of SMN1
• Two, three, or four copies of SMN2
• Age 5 to 20 years
• Non-ambulatory participants: maximum function sitting or standing with support, never walked independently, still able to sit independently for 5 seconds at screening, with active ankle plantar flexion strength of at least 3 N with hand-held myometry and capable of performing repetitive maximal plantar flexion effort for 120 seconds. HFMSE score at screening between 10 and 45 points.
• Ambulatory participants: minimum function of independent walking, able to walk unassisted a minimum of 100 meters at screening, ankle plantar flexion strength of at least 10 N with hand-held myometry and capable of performing repetitive maximal plantar flexion for 120 seconds. HFMSE score at screening between 40 and 60.
• SMN-directed therapy inclusion:
‣ Current Evrysdi prescription
• Must have Evrysdi prescription through their treating physician but have not yet initiated treatment OR
⁃ Current Spinraza or Zolgensma prescription
• For patients on Spinraza, must have been taking Spinraza for at least 12 months at screening (4 loading and 2 maintenance doses) and following the FDA-recommended dosing schedule
∙ For patients on Zolgensma, must have been dosed at least one year prior to screening
∙ Must have Spinraza or Zolgensma prescription through their treating physician OR
⁃ Changing from Spinraza or Zolgensma to Evrysdi
• For patients on Spinraza, must have been taking Spinraza for at least 12 months at screening (4 loading and 2 maintenance doses) and following the FDA-recommended dosing schedule
∙ For patients on Zolgensma, must have been dosed at least one year prior to screening
∙ Must have voluntarily decided to switch therapies based on discussion with their treating physician
∙ Must have Evrysdi prescription through their treating physician but have not yet initiated treatment OR
⁃ Have never received any SMN-directed therapies