Precision BioSciences Wins FDA Fast Track for First Gene-Editing Therapy Targeting Duchenne Muscular Dystrophy, Prepares to Dose Children in Phase 1/2 Trial

Precision BioSciences announced on March 9 that the U.S. Food and Drug Administration has granted Fast Track designation to PBGENE-DMD, an investigational gene-editing therapy for Duchenne muscular dystrophy. The designation, which expedites regulatory review for drugs that address serious conditions with unmet medical needs, arrives days before the company presented new preclinical data at the 2026 Muscular Dystrophy Association Clinical and Scientific Conference showing durable dystrophin restoration and functional improvements in animal models lasting nine months.

Duchenne muscular dystrophy is a progressive, fatal genetic disease caused by mutations in the gene encoding dystrophin, a structural protein essential for muscle fiber integrity. It affects approximately one in every 3,500 to 5,000 male births worldwide, with most patients losing the ability to walk by their early teens and facing life-threatening cardiac and respiratory complications by their twenties. While one gene therapy, Sarepta Therapeutics’ Elevidys, received FDA approval in 2023, it delivers a truncated micro-dystrophin that is substantially smaller than the native protein, and its label carries a boxed warning for acute serious liver injury.

A different approach: gene excision rather than gene replacement

PBGENE-DMD takes a fundamentally different approach from existing treatments. Rather than delivering a shortened substitute for dystrophin, the therapy uses Precision BioSciences’ proprietary ARCUS gene-editing platform to permanently edit the patient’s own dystrophin gene. A single adeno-associated virus vector encodes two ARCUS nuclease proteins, each designed to make a precise cut at either end of the exon 45-55 region where the majority of Duchenne-causing mutations cluster. The intervening faulty exons are excised, and the cell’s natural repair machinery joins the remaining gene segments, producing a near full-length, functional dystrophin protein.

This exon excision strategy could potentially address mutations found in up to 60 percent of boys with Duchenne, a substantially broader population than any single exon-skipping therapy can reach. Because the edit is permanent and occurs at the DNA level, it also has the theoretical advantage of persisting through cell division, including in muscle satellite stem cells responsible for long-term muscle regeneration.

Preclinical data show durable muscle recovery

Data presented at the MDA conference on March 10 came from a GLP-compliant study in humanized Duchenne mouse models engineered to replicate the progressive muscle degeneration seen in patients. At 90 days after a single dose, treated animals showed a 50 to 65 percent reduction in creatine kinase levels, a blood biomarker that rises when muscle fibers break down. Additional markers of muscle damage, ALT and AST, also improved.

Functional assessments were more striking. Through nine months of follow-up, treated mice maintained approximately 81 to 84 percent of the maximal force output and 89 to 92 percent of the tetanic force output observed in healthy controls. The improvements emerged between months three and six and then held steady through the study endpoint. Histological analysis confirmed increasing dystrophin-positive fiber counts across quadriceps, gastrocnemius, cardiac, and diaphragm tissues over the nine-month observation period.

The FUNCTION-DMD trial

The Phase 1/2 clinical study, called FUNCTION-DMD and registered as NCT07429240, plans to enroll ambulatory patients between the ages of 2 and 7 who carry mutations in exons 45 through 55. The trial will evaluate safety, tolerability, and efficacy at a dose of 1 times 10 to the 14th viral genomes per kilogram, with early efficacy measured by dystrophin protein expression from muscle biopsies. The company has stated it expects to dose 3 to 5 children in 2026, with initial multi-patient data anticipated by year end.

PBGENE-DMD has now accumulated three FDA regulatory designations: Fast Track, Rare Pediatric Disease, and Orphan Drug. The Rare Pediatric Disease designation makes the therapy eligible for a priority review voucher upon approval, while Orphan Drug status provides seven years of market exclusivity. CEO Michael Amoroso said in a statement that the Fast Track designation “reflects the significant unmet need in DMD.”

Competitive landscape

The Duchenne treatment landscape has expanded rapidly but remains defined by compromise. Sarepta’s Elevidys, the only approved gene therapy, delivers a micro-dystrophin roughly one-third the size of the native protein and cannot be redosed because patients develop neutralizing antibodies to the AAV vector after treatment. Its label excludes patients with certain exon 8 or 9 deletions and those with preexisting antibodies to the AAVrh74 vector. Several antisense oligonucleotide exon-skipping therapies are also approved but each targets only a single exon, limiting individual drugs to narrow patient subsets.

PBGENE-DMD’s gene excision approach, if validated in humans, would be the first gene-editing therapy for Duchenne to enter clinical testing. Its promise of producing near full-length dystrophin rather than a truncated surrogate could represent a meaningful advance, though the transition from mouse models to human muscle physiology has historically been a challenging step for Duchenne therapies. The first clinical data later this year will begin to clarify whether the durable preclinical results translate to patient benefit.