# A new SMA drug goes after the muscle itself

> Isembyld is the first SMA therapy cleared to treat muscle loss directly, and it works on top of the drugs patients already take.
- Title: A new SMA drug goes after the muscle itself · Dallas Express
- Summary: Isembyld is the first SMA therapy cleared to treat muscle loss directly, and it works on top of the drugs patients already take. Existing SMA drugs protect…
- Keywords: sma, fda, rare disease, drug approval, neuromuscular, news, politics, drug, goes, muscle, itself, Dallas Express
- Source: Dallas Express — https://dallasexpress.com/health/fda-approves-isembyld-first-sma-treatment-to-target-muscle-loss
- Author: Dallas Express
- Published: 2026-09-13T18:00:55+00:00
- Read time: 1 min
- Topics: sma, fda, rare disease, drug approval, neuromuscular, news, politics
## FDA clears Isembyld
Scholar Rock said on September 11 that the FDA approved Isembyld, also called apitegromab-mstn, for spinal muscular atrophy. Shipments start within days.
## Who can get it
Approval covers patients aged 2 and up who are already on an SMN2-targeted treatment. It is an add-on, not a replacement.
## Why muscle is the gap
SMA comes from a faulty SMN1 gene, starving motor neurons of a protein they need. Current drugs restore that protein, but people with advanced disease still lose movement.
## It blocks myostatin
Myostatin is a protein that limits muscle growth. Isembyld stops it from activating, making this the first approved SMA therapy aimed at muscle loss itself.

> This is what progress looks like
## The trial numbers
In a 52-week trial of 188 people aged 2 to 21, 34.2% of treated children aged 2 to 12 hit clinically meaningful motor improvement versus 13.5% on placebo.
## The risks are real
Fractures, including serious ones, went up. Respiratory infections, vomiting, cough and headache were common, and the FDA flagged possible fetal harm and reproductive effects.
## Key takeaway

Existing SMA drugs protect motor neurons but don't stop muscle decline. Isembyld is the first approved add-on aimed at the muscle itself, with a real fracture risk attached.