The FDA’s priority review acceptance of BridgeBio’s BBP-418 is another step toward what William Blair previously dubbed a “diversified commercial portfolio.” It also adds to the rapidly building momentum in muscular dystrophy more broadly.
The FDA has accepted BridgeBio’s BBP-418 for priority review, setting up what William Blair analysts called the first of three potential blockbuster launches—and possibly paving the way for the first approved therapy for a rare type of muscular dystrophy.
The FDA has set a target action date of November 27 for BBP-418’s new drug application in limb-girdle muscular dystrophy type 2I/R9 (LGMD2I/R9) and is not planning to hold an advisory committee meeting to discuss the application, BridgeBio announced on Wednesday, representing “incremental positives for an approval and launch of the product in late 2026 or early 2027,” William Blair said in a note to investors.
BridgeBio shares rose 3% premarket Wednesday in response to the news, according to the firm, but were back down to $65.96 at the time of publication.
BridgeBio is supporting BBP-418’s application with data from the Phase 3 FORTIFY trial, in which the oral therapy met all primary and secondary endpoints at the pre-specified 12-month interim analysis, according to the biotech’s announcement, “showing treated individuals improving while placebo recipients declined across every key measure.”
Patients also saw increases in ambulatory and pulmonary function, and a 5% increase in predicted pulmonary volume versus placebo, BridgeBio reported in October 2025. Jefferies analysts at the time said the data represent a “best-case” scenario, adding that BBP-418 compares favorably with Sarepta Therapeutics’ SRP-9003, an investigational gene therapy for LGMD. That asset is currently in a Phase 3 trial.
LGMD2I/R9 occurs when mutations in the FKRP protein diminish but do not totally abolish its function, resulting in skeletal muscle damage, first to the lower and then the upper limbs. Pulmonary muscle and cardiac muscle involvement occur later in the disease process, and “patients ultimately die from respiratory failure,” BridgeBio Neuromuscular CEO Christine Siu said in a prepared statement on Wednesday.
“Data from the Phase III FORTIFY study have painted an impressive picture of the efficacy and safety of BBP-418, with consistent, highly statistically significant functional and biomarker efficacy over placebo in LGMD2I/R9 patients,” William Blair said on Wednesday. The analysts estimated worldwide sales of $1.1 billion in 2035 for the program.
In a note on Wednesday, Jefferies analysts declared “90%+ confidence” in full approval of BBP-418 based on the FORTIFY interim results. “Net-net, $1B+ peak sales seems reasonable,” the firm added, modeling $600M+ in the U.S.
For BridgeBio, the priority review of BBP-418 is just one step on the company’s ladder toward what William Blair in a May 12 note called a “diversified commercial portfolio.” That note referenced the NDA submission that day of encaleret for autosomal dominant hypocalcemia type 1—another possible blockbuster, according to the analysts. A third potential blockbuster, William Blair said, is infigratinib in hypochondroplasia, for which BridgeBio is on track to submit an NDA in the third quarter of this year, per a May 8 note.
Muscular dystrophy momentum
BridgeBio’s news adds to the rapidly building momentum across a range of muscular dystrophies. Duchenne muscular dystrophy, in particular, has seen positive news of late. Dyne Therapeutics submitted a Biologics License Application to the FDA earlier this week for its exon 51 skipper DYNE-251, while REGENXBIO, Wave Life Sciences and Capricor Therapeutics are also all nearing the regulatory finish line in DMD.
Meanwhile, Novartis will soon learn whether its $12 billion buyout of Avidity last October was worth the risk. The company is anticipating data from a Phase 3 trial of the DMPK-targeting therapy del-desiran in 159 patients with myotonic dystrophy type 1 in the second half of this year. When asked by BioSpace whether this readout will make or break the acquisition, Oppenheimer’s Kostas Biliouris said “Mostly, yes. . . . This is perhaps 80% of the acquisition.”
