Key Takeaways
- The FDA has placed clinical holds on two Regenxbio gene therapies, RGX-111 and RGX-121, following the discovery of a CNS tumor in a patient.
- Regenxbio’s stock dropped 32% to $9.16 in premarket trading amid the announcement.
- The tumor was found in a recipient of RGX-111, a therapy for mucopolysaccharidosis type I, which aims to deliver the IDUA gene to the CNS.
Details on the FDA’s Clinical Holds
The FDA’s recent decision to impose clinical holds on Regenxbio’s RGX-111 and RGX-121 gene therapy programs arises from the discovery of a central nervous system (CNS) tumor in a patient treated with RGX-111. The finding coincides with a crucial approval decision expected in less than two weeks, significantly impacting Regenxbio’s share price, which plummeted 32% to $9.16 in premarket trading.
RGX-111 targets severe mucopolysaccharidosis type I (MPS I), or Hurler syndrome, a rare disease linked to developmental delays and decreased life expectancy. The therapy utilizes an AAV9 vector for delivering the IDUA gene directly to the CNS, aiming to improve patient outcomes. Despite the adverse event, Regenxbio’s CEO Curran Simpson expressed surprise at the FDA’s decision to extend the clinical hold to RGX-121, a therapy developed for MPS II, or Hunter syndrome. The FDA previously delayed an approval decision on RGX-121, and a new verdict is anticipated by February 8.
The clinical hold was triggered by the detection of an intraventricular CNS tumor during a routine MRI on a 5-year-old patient who had received RGX-111 four years prior. Although this incident raised concerns, Regenxbio highlighted that the patient remains asymptomatic, and the treating physician has reported positive developmental progress. Importantly, other recipients of RGX-111 have not shown any signs of neoplasm.
Initial analysis of the resected tumor revealed an integration of the AAV vector genome, which is linked to the overexpression of the PLAG1 proto-oncogene, known for its vulnerability to chromosomal rearrangements. An ongoing investigation aims to determine if the tumor is directly related to the RGX-111 treatment.
In 2023, Regenxbio decided to deprioritize RGX-111 while initiating a search for a partnership, which resulted in a collaboration with Nippon Shinyaku last year. Despite the setback with RGX-111, Regenxbio continued to focus on RGX-121, which is also part of the Nippon Shinyaku deal.
The implications from the FDA’s action and the ongoing investigation into RGX-111 and RGX-121 may influence future gene therapy developments and regulatory approaches, especially regarding safety profiles for similar therapies. The biotech company remains committed to addressing these concerns while advancing its ongoing research.
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