Denali surges on FDA approval of first Hunter syndrome drug in 20 years
AVLAYAH marks breakthrough in crossing blood-brain barrier, opening new path for neurological treatments
Denali Therapeutics shares jumped 4% on Wednesday after the U.S. Food and Drug Administration approved AVLAYAH, the first new treatment for Hunter syndrome in nearly two decades and a breakthrough therapy designed to cross the blood-brain barrier.
The South San Francisco-based biotechnology company's stock rose to $21.80, giving it a market capitalization of $3.34 billion, after the regulator granted accelerated approval for AVLAYAH (tividenofusp alfa-eknm) for the treatment of Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II).
The approval represents a significant milestone for Denali, as AVLAYAH becomes the first FDA-approved medicine to leverage the company's proprietary TransportVehicle™ platform to deliver therapeutics across the blood-brain barrier—a longstanding challenge in treating neurological disorders. The platform binds to transferrin receptors to facilitate delivery of enzymes, antibodies, and other biotherapeutics to both the body and brain.
"Today's approval of AVLAYAH marks a major milestone for people living with Hunter syndrome and their families," said Ryan Watts, chief executive officer of Denali Therapeutics. "We are proud to deliver the first FDA-approved medicine designed to address the neurological manifestations of this devastating disease."
Clinical trial data published in the New England Journal of Medicine showed that AVLAYAH achieved a 91% reduction in cerebrospinal fluid heparan sulfate levels from baseline by week 24 of treatment, a reduction that was maintained through week 153. By week 24, 93% of treated patients had CSF HS levels within the range of individuals without Hunter syndrome.
Hunter syndrome is a rare genetic lysosomal storage disorder that primarily affects males, causing progressive damage to organs and tissues. While existing enzyme replacement therapies can treat somatic symptoms, they cannot cross the blood-brain barrier to address the neurological manifestations of the disease, which include cognitive decline and developmental delays.
According to the FDA, AVLAYAH's approval addresses this critical unmet need. However, continued approval for this indication may be contingent upon verification of clinical benefit in a confirmatory trial, a requirement typical of accelerated approvals.
Analysts responded positively to the approval, with BTIG reiterating a "Buy" rating and increasing its price target from $32 to $36. Jefferies maintained a "Buy" rating with a $40 target, while Goldman Sachs and UBS have both issued "Buy" ratings with targets of $35 and $33, respectively.
The consensus among analysts remains bullish, with an average 12-month price target of $32.93 according to MarketBeat data, representing approximately 52% upside from current levels. Of 25 analysts covering the stock, 18 rate it a "Buy" while just one recommends "Hold," with zero "Sell" ratings.
The approval validates Denali's TransportVehicle platform, which the company believes can be applied to other neurological disorders. Denali is developing additional programs using the technology, including treatments for other lysosomal storage disorders and neurodegenerative diseases.
Hunter syndrome affects approximately 1 in 100,000 to 1 in 170,000 male births globally, according to patient advocacy groups. The rarity of the disease means AVLAYAH is likely to command premium pricing, though Denali has not yet disclosed commercial details or launch timing.
The approval comes after a challenging period for Denali. In early 2025, the company reported that its DNL343 program for amyotrophic lateral sclerosis failed to demonstrate a treatment effect on neurofilament light, a biomarker of neuronal damage, in the Phase 2/3 HEALEY ALS Platform Trial. That program followed an earlier setback in January 2025 when the ALS study did not meet its primary endpoint.
With AVLAYAH's approval, Denali transforms from a clinical-stage company to one with a marketed product, potentially improving its cash position and reducing dependence on equity financing. The company had $540.5 million in cash and equivalents at the end of the most recent quarter, according to regulatory filings.
Investors will now focus on the commercial launch of AVLAYAH and Denali's ability to capture market share in the Hunter syndrome treatment landscape, as well as progress on its pipeline of other TransportVehicle-based candidates. The confirmatory trial results required for full FDA approval will be a key catalyst to watch in the coming years.