What's Happening?
The U.S. Food and Drug Administration (FDA) has rejected REGENXBIO's investigational gene therapy, RGX-121, intended for the treatment of Hunter syndrome, a rare neurodegenerative disorder. The rejection follows a three-month delay and is based on concerns
outlined in a complete response letter (CRL) from the FDA. The agency expressed uncertainty over the eligibility criteria used in the study and questioned the use of natural history external controls and the surrogate endpoint of cerebrospinal fluid biomarker levels as a basis for approval. The FDA recommended that REGENXBIO conduct a new study with more patients, longer follow-up periods, and an untreated comparator group. Despite these recommendations, REGENXBIO described these options as challenging due to the ultra-rare nature of Hunter syndrome. The company plans to seek a Type A meeting with the FDA to discuss the path forward and provide additional evidence supporting the therapy's effectiveness.
Why It's Important?
The FDA's decision to reject RGX-121 highlights the regulatory challenges faced by companies developing treatments for rare diseases. The rejection is significant as it underscores the FDA's cautious approach to granting accelerated approvals without placebo-controlled data, which could impact other companies, such as Denali Therapeutics, awaiting FDA decisions on similar therapies. The decision also affects the families of patients with Hunter syndrome, who have limited treatment options. The rejection has financial implications for REGENXBIO, as reflected in the company's stock price drop. The outcome of the FDA's decision could influence future regulatory strategies and the development of gene therapies for rare diseases.
What's Next?
REGENXBIO intends to engage with the FDA in a Type A meeting to discuss the next steps for RGX-121. The company aims to provide additional evidence from experts to support the therapy's effectiveness. The outcome of these discussions will determine the future of RGX-121 and could set a precedent for other gene therapies targeting rare diseases. Meanwhile, Denali Therapeutics is awaiting the FDA's decision on its Hunter syndrome therapy, tividenofusp alfa, which could be influenced by the FDA's stance on placebo-controlled data. The broader gene therapy industry will be closely monitoring these developments, as they may impact regulatory strategies and approval processes for similar treatments.
