Novartis (Novartis (NVS)) just got some good news on a bet that cost it $12 billion. The company announced Thursday that its experimental therapy del-brax hit its goals in a mid-stage study for facioscapulohumeral muscular dystrophy, or FSHD — a rare genetic disease that causes progressive muscle weakness.

The biomarker cohort of the Phase 1/2 FORTITUDE study met both its primary and key secondary endpoints. That's a fancy way of saying the drug did what it was supposed to do at the molecular level, and it also seemed to help protect muscles from damage.

FSHD affects somewhere between 45,000 and 87,000 people in the U.S. and Europe. It's not a huge market, but for patients who have it, the disease can be devastating — leading to pain, fatigue, and disability as muscles waste away over time.

Novartis reported that del-brax reduced levels of a biomarker called KHDC1L (also known as cDUX), which is regulated by the DUX4 gene — the root cause of FSHD. The drug also lowered creatine kinase levels, a standard marker of muscle damage. According to the company, these results show strong target engagement and a real reduction in muscle injury among treated patients.

Nazem Atassi, Global Head of Neuroscience and Gene Therapy Development at Novartis, said the findings replicate what the company saw in earlier dose-escalation studies. "The data support the dosing regimen selected for the ongoing Phase 3 trial," he said. Atassi added that Novartis is reviewing the full set of biomarker and clinical results and plans to engage with global regulators as development moves forward.

Del-brax is what's known as an antibody oligonucleotide conjugate, or AOC. Think of it as a smart bomb: a monoclonal antibody guides it to muscle cells, where it delivers a small interfering RNA that suppresses the faulty DUX4 gene. Novartis says del-brax is the only investigational therapy that has shown disease-modifying potential for FSHD in clinical studies. It already has Orphan Drug and Fast Track designations from the FDA, plus an Orphan Drug designation from the European Medicines Agency.

The drug joined Novartis' pipeline through the company's acquisition of Avidity Biosciences, which closed in February 2026 for $12 billion. That deal also brought along two other experimental drugs: del-desiran, now in Phase 3 for myotonic dystrophy type 1, and del-zota, in Phase 2 for Duchenne muscular dystrophy.

The ongoing Phase 3 trial, called FORTITUDE-3, is enrolling 200 FSHD patients aged 16 to 70. It's testing del-brax against a range of clinical and patient-reported outcome measures. If the data hold up, Novartis could have a first-in-class treatment for a disease that currently has no approved therapies.

Investors seemed to like the news. Novartis shares were up 2.57% in premarket trading Thursday, at $151.91.