FDA Delays Decision on Denali's Hunter Syndrome Drug, Highlighting Industry-Wide Trend
Denali Therapeutics has become the latest biotech company to face a delay in the U.S. Food and Drug Administration's (FDA) review process, as the agency pushes back its decision on the company's enzyme replacement therapy for Hunter syndrome. This development underscores a growing pattern of regulatory delays in the pharmaceutical industry, affecting multiple companies and potential breakthrough treatments.
Denali's Tividenofusp Faces Three-Month Review Extension
The FDA has extended its review period for Denali's tividenofusp (tivi) by three months, moving the decision date from January 5, 2026, to April 5, 2026. This delay comes after Denali submitted updated clinical pharmacology information as part of the application review process. Despite the setback, Denali maintains that the new information does not affect the drug's efficacy, safety, or biomarkers.
Ryan Watts, Ph.D., CEO of Denali, stated, "We appreciate the FDA's continued collaboration throughout the review process. We continue to prepare for the potential approval and commercial launch of tividenofusp alfa."
The delay reportedly stems from a discrepancy in the molecular weight of the drug listed on a public source, which Denali proactively flagged to the FDA. This led to the agency requesting updated molecular weight information directly from the biotech company.
Tividenofusp: A Potential Breakthrough for Hunter Syndrome
Tividenofusp is an engineered version of the iduronate 2-sulfatase enzyme, designed to penetrate the blood-brain barrier by binding to transferrin receptor 1. The drug aims to treat Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II), a rare genetic disorder characterized by the body's inability to break down certain sugars.
Denali's application is based on a phase 1/2 open-label trial involving 47 boys around the age of 5. The study demonstrated a significant reduction in the biomarker heparan sulfate in both cerebrospinal fluid and urine after 24 weeks, with levels dropping by an average of about 90% from baseline.
FDA Delays: A Growing Trend in the Pharmaceutical Industry
The delay in Denali's application review is part of a broader trend affecting the pharmaceutical industry. Despite FDA Commissioner Marty Makary, M.D.'s June pledge that the agency was on track to meet all of its PDUFA deadlines, several companies have experienced delays or missed decision dates this year.
Notable examples include:
- Regenxbio's gene therapy for Hunter syndrome
- Stealth Therapeutics' rare disease candidate
- KalVista Pharmaceuticals' angioedema asset
- Omeros' transplant drug
These delays come amid concerns about FDA staffing cuts and have raised questions about the agency's ability to process applications efficiently.
References
- Denali's Hunter syndrome drug latest to be hit by FDA decision delay
Denali Therapeutics has become the latest on a growing list of biotechs to experience an FDA review delay in recent months.
Explore Further
What is the projected market size for tividenofusp as a treatment for Hunter syndrome?
What are the key differentiators between tividenofusp and Regenxbio's gene therapy for Hunter syndrome?
How do FDA delays impact the commercial launch timeline and revenue projections for Denali’s drug pipeline?
What are the potential implications of FDA staffing cuts on the review process for rare disease treatments?
What were the major findings from the phase 1/2 trial of tividenofusp and how do they compare to existing treatments for Hunter syndrome?