FDA Approves First Muscle-Targeted Therapy for SMA: A Conversation with Dr. Se-Jin Lee

The FDA has approved Isembyld (apitegromab-mstn), the first therapy designed to target muscle health and regeneration in people living with spinal muscular atrophy (SMA). This milestone adds to the progress made by genetic therapies for SMA and provides families with a new option focused on improving muscle strength and daily function.

Se-Jin Lee, M.D., Ph.D.

To help families understand the science behind this breakthrough, Quest spoke with Dr. Se-Jin Lee, whose pioneering work on muscle biology paved the way for this therapy.

Q: What is the significance of this approval?

Dr. Lee: This is the first therapy for SMA that works directly on the muscles. While current treatments target the genetic cause of SMA, Isembyld is designed to enhance muscle mass and strength, giving patients additional support in their daily lives. Families now have access to a therapy that complements existing options and offers new hope for better mobility and independence.

Q: How does Isembyld work?

Dr. Lee: The therapy targets a protein called myostatin, which normally acts like a brake on muscle growth. Isembyld works by keeping myostatin in its inactive state, preventing it from limiting muscle growth. By doing this, it allows muscles to grow and function more effectively.

Q: What does this mean for families living with SMA?

Dr. Lee: It means more options and more possibilities. Families can feel hopeful that this therapy will help strengthen muscles and improve quality of life when used alongside existing SMA treatments. For me, as a scientist, it’s incredibly rewarding to see basic discoveries from the lab leading to real treatments that make a difference in patients’ lives.

Q: What comes next in myostatin research?

Dr. Lee: SMA is just the beginning. Researchers are already exploring myostatin inhibitors for other neuromuscular conditions and even for age-related muscle loss. With so much progress happening, I believe we’ll continue to see new therapies emerge that expand the possibilities for patients and families.

This approval represents not only a new treatment option for SMA families but also a milestone of progress in neuromuscular research.

Se-Jin Lee, M.D., Ph.D., is an MDA-funded researcher and Professor, The Jackson Laboratory, and Presidential Distinguished Professor at University of Connecticut School of Medicine.