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FDA Extends Review of DNLI's Hunter Syndrome Drug by Three Months

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Key Takeaways

  • The FDA extended review of Denali's tividenofusp alfa BLA for Hunter syndrome treatment.
  • The timeline moved from Jan. 5 to April 5, 2026, after Denali submitted new pharmacology data.
  • The extension isn't tied to safety or efficacy, and no extra data was requested by the FDA.

Denali Therapeutics Inc. (DNLI - Free Report) announced that the FDA has extended its review timeline of the Biologics License Application (“BLA”) for pipeline candidate, tividenofusp alfa.

The BLA is seeking accelerated approval of tividenofusp alfa for the treatment of mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome.

The extension is a setback for Denali as it delays a potential approval of its lead pipeline candidate, tividenofusp alfa.

Denali stock went down in after-market trading on Oct. 13. Shares of DNLI have lost 26.5% year to date against the industry’s 9.2% gain.

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More on DNLI’s Hunter Syndrome Drug

The FDA extended the target date from Jan. 5, 2026, to April 5, 2026 as a result of Denali’s submission of updated clinical pharmacology information in response to a request from the regulatory body as part of the standard review process.

The extension is not related to efficacy, safety or biomarkers.

The submission is classified a major amendment to the BLA by the FDA. Hence, the review date has been extended.

Nonetheless, the FDA did not ask for any additional data and hence Denali believes that the updated information submitted in the amendment does not affect the clinical pharmacology or benefit-risk conclusions of the BLA.

Tividenofusp alfa (DNL310) is composed of the iduronate 2-sulfatase (IDS) enzyme fused to Denali’s proprietary TransportVehicle (TV) platform.

The candidate is designed to deliver IDS into the brain and the body, with the goal of addressing behavioral, cognitive and physical symptoms of Hunter syndrome.  

The FDA had earlier granted Fast Track and Breakthrough Therapy designations to tividenofusp alfa for development in the treatment of MPS II. The European Medicines Agency has granted Priority Medicines designation to tividenofusp alfa.

The phase II/III COMPASS study is enrolling participants with MPS II in North America, South America and Europe to support global approval.

DNLI’s Other Pipeline Candidates

Denali is also evaluating DNL126 for the treatment of Sanfilippo syndrome type A (MPS IIIA). The company had earlier reached alignment with the FDA’s Center for Drug Evaluation and Research that cerebrospinal fluid heparan sulfate (CSF HS) may be considered a reasonably likely surrogate endpoint to predict clinical benefit and may therefore be used to support accelerated approval of DNL126 for MPS IIIA.

Another candidate in DNLI’s pipeline is TAK-594/DNL593. Denali has collaborated with Takeda for the co-development and co-commercialization of DNL593, a therapeutic candidate engineered for the delivery of progranulin across the BBB and into lysosomes for the treatment of frontotemporal dementia (FTD) associated with a mutation in the granulin (GRN) gene. Denali is conducting the ongoing phase I/II study of DNL593 in FTD-GRN.

Denali and Biogen (BIIB - Free Report) are jointly evaluating an LRRK2 inhibitor, BIIB122/DNL151, in development to treat Parkinson’s disease (PD).

Biogen is leading the global phase IIb LUMA study, evaluating BIIB122's impact on disease progression in early-stage PD. In May 2025, Biogen announced that the LUMA study was fully enrolled with a readout expected in 2026.

Meanwhile, Denali is conducting the phase IIa BEACON study, specifically enrolling participants with LRRK2-associated PD to assess how LRRK2 inhibition may impact this disease.

Denali expects to submit regulatory applications to begin clinical testing of one to two TV-enabled programs each year over the next three years across its Enzyme TV (ETV), Antibody TV (ATV), and Oligonucleotide TV (OTV) franchises.

Zacks Rank and Key Picks

Denali currently carries a Zacks Rank #3 (Hold).

A couple of better-ranked stocks in the biotech sector are Amicus Therapeutics (FOLD - Free Report) and CorMedix (CRMD - Free Report) . While FOLD sports a Zacks Rank #1 (Strong Buy) at present, CRMD carries a Zacks Rank #2 (Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

In the past 60 days, estimates for Amicus Therapeutics’ 2025 earnings per share (EPS) have remained constant at 31 cents. Earnings per share estimates for 2026 have increased from 68 cents to 70 cents during the same period.

Amicus Therapeutics’ earnings beat estimates in one of the trailing four quarters while missing the same on the remaining three occasions, the average negative surprise being 24.38%.

In the past 60 days, estimates for CorMedix’s 2025 EPS have increased from to $1.22 to $1.85. During the same period, EPS estimate for 2026 has moved north to $2.49 from $2.12. Year to date, shares of CRMD have rallied 30.6%.

CorMedix’s earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 34.85%.

 

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