New York, Jan 29, 2026, 15:20 EST — Regular session
• Denali Therapeutics shares climbed in afternoon trading, gaining ground while the broader biotech sector remained flat.
• Attention intensified following the FDA’s decision to halt Regenxbio’s rare-disease gene therapy trials.
• Investors are now zeroed in on Denali’s FDA timeline for its Hunter syndrome treatment and the data update expected in early February.
Denali Therapeutics (DNLI.O) shares climbed 3.7% to $21.62 Thursday afternoon, after fluctuating between $20.53 and $21.96 earlier. The iShares Nasdaq Biotechnology ETF (IBB) saw minimal movement.
Traders linked the move to a sudden shake-up in the rare-disease race, as regulators ramp up scrutiny on a potential competitor’s program. This matters now—Denali’s clock is ticking with its lead drug currently under U.S. review.
Denali, based in South San Francisco, is waiting on a U.S. FDA verdict by April 5 for tividenofusp alfa, targeting mucopolysaccharidosis type II (Hunter syndrome) under the accelerated approval route. This faster track allows reliance on early biomarkers but mandates a confirmatory trial. The drug leverages Denali’s TransportVehicle platform to breach the blood-brain barrier—a key obstacle for many treatments—and Phase 1/2 data appeared in The New England Journal of Medicine on Jan. 1. CEO Ryan Watts dubbed 2026 “a defining year for Denali” ahead of a potential launch. The company also plans to unveil initial clinical results for DNL126 in Sanfilippo syndrome type A at the WORLD Symposium from Feb. 3-6, it said. 1
On Wednesday, the FDA slapped clinical holds on Regenxbio’s (RGNX.O) RGX-111 and RGX-121 trials after a brain tumor turned up in a five-year-old treated with RGX-111 about four years ago. Regenxbio said no other tumors have appeared among the 41 patients treated so far. CEO Curran Simpson called the FDA’s decision to halt the RGX-121 program “surprising.” 2
Leerink Partners analyst Mani Foroohar described the hold as “confusing and unexpected,” especially since it arrived just days ahead of the Feb. 8 FDA deadline for RGX-121. He also pointed out that no causal connection between RGX-111 and the tumor has been proven. 3
For Denali, the optics are awkward but also clarifying: gene therapy safety headlines can ripple across drug developers, yet the immediate competitive threat in Hunter syndrome looks less straightforward than it did a week ago.
Regenxbio shares climbed roughly 4.7% on Thursday, rebounding after a steep slide the day before. The move hints that some investors see the hold as a temporary pause, not a full stop.
Still, the situation isn’t one-sided. The FDA might demand additional clinical or manufacturing data from Denali, or delay its review once more. Accelerated approvals often carry strict post-approval conditions and plenty of potential pitfalls.
Coming up soon: Denali’s WORLD Symposium presentation kicks off Feb. 3, while the FDA’s April 5 deadline looms for tividenofusp alfa. Investors will also keep an eye on any updates about Regenxbio’s clinical hold and whether the agency will lift it before the Feb. 8 cutoff.
