New York, May 14, 2026, 15:10 EDT
- REGENXBIO reported that its pivotal trial for Duchenne muscular dystrophy hit the primary endpoint with RGX-202.
- Shares dropped hard, with investors eyeing two serious adverse events and scrutinizing the FDA approval path.
- The company is gearing up for a potential accelerated approval, eyeing a commercial launch in 2027.
REGENXBIO Inc. stock dropped Thursday, despite the company reporting that its experimental gene therapy for Duchenne muscular dystrophy hit the primary endpoint in a late-stage trial. Investors zeroed in on lingering safety issues and a murky regulatory path forward, eclipsing the positive trial result.
This isn’t just another data release. RGX-202 sits at the core of the Rockville, Maryland biotech’s pipeline, and investors are closely tracking whether it can carve out a place in Duchenne gene therapy—a space already shadowed by liver-safety worries.
The stock slid roughly 37% to $6.31, hitting an intraday bottom of $6.02 along the way. Volume topped 8.6 million shares—well beyond typical levels for the small-cap biotech.
REGENXBIO reported that 93% of evaluable patients showed over 10% microdystrophin expression by week 12 in the pivotal Phase III portion of its AFFINITY DUCHENNE trial. Microdystrophin—a truncated form of the dystrophin protein absent or faulty in Duchenne muscular dystrophy—was measured as part of the study.
The study included 31 ambulatory boys, all at least 1 year old. According to REGENXBIO, the average microdystrophin expression among participants with biopsy results landed at 71.1%. For boys over 8—a group where functional decline is usually seen—that figure was 41.6%.
Steve Pakola, the company’s Chief Medical Officer, called the link between microdystrophin expression and functional gains a “landmark distinction” for Duchenne gene therapy. At Arkansas Children’s Hospital, principal investigator Aravindhan Veerapandiyan described both the expression results and the “manageable safety profile” as encouraging. Pat Furlong, representing Parent Project Muscular Dystrophy, noted that families “cannot wait” for new treatments. Regenxbio Inc
The primary endpoint didn’t pose the issue. Everything else in the package did.
REGENXBIO flagged two serious adverse events: an 8-year-old developed subacute myocarditis, a type of heart muscle inflammation, and a 10-year-old showed asymptomatic liver injury. According to the company, both incidents were handled and cleared up within weeks, with no lingering effects.
Mani Foroohar at Leerink Partners called the data more mixed than the brokerage wanted, flagging both adverse events and uncertainty around the FDA’s stance as likely flashpoints for debate. BioSpace, in a separate piece, quoted Leerink calling the update a “mixed bag.” Reuters
REGENXBIO intends to take the data to the FDA and seek accelerated approval—a route that lets drugs through if a surrogate marker is “reasonably likely” to signal clinical benefit. According to a company filing, the results reached investors via an 8-K. The company added that it’s getting ready for a potential launch in 2027. SEC
The FDA wants a randomized controlled trial, according to REGENXBIO. Still, the company noted the agency has signaled that externally controlled trials could be acceptable under certain conditions—specifically, if the treatment effect proves strong enough. Negotiation appears possible, but certainty isn’t on the table.
REGENXBIO has faced a bruising period for its rare-disease programs. In January, the FDA slapped clinical holds on RGX-111 and RGX-121 after a brain tumor appeared in a patient receiving RGX-111. The following month, the agency declined to approve RGX-121 for Hunter syndrome, pointing to lingering doubts about the trial design.
REGENXBIO announced Thursday that the FDA has lifted the partial clinical hold on RGX-121. The company also said it has appealed the complete response letter—a regulatory step that comes when the FDA turns down an approval. For the first quarter, REGENXBIO posted a net loss of $90.1 million, swinging from net income of $6.1 million the previous year, after revenue tumbled to $6.4 million from $89.0 million.
Competition complicates things further. Sarepta Therapeutics’ Elevidys, the standard Duchenne gene therapy investors look to, drew criticism following two deaths tied to acute liver failure, Reuters reported last year.
The bear case is straightforward enough. Functional data for RGX-202 are still sparse—just one year’s worth from only nine patients so far. Clinicians not involved with the trial will want to see more time on the clock for heart, liver, and durability outcomes. Contemporary Pediatrics described the biomarker data as robust, but flagged the functional readout as thin, not randomized, and reliant on external controls.
