Key Takeaways:
The Food and Drug Administration will reverse its rejection of Regenxbio Inc.'s experimental gene therapy for a fatal childhood brain disorder, the company said Monday, the third such regulatory reversal in two months.
"Following discussions with the FDA, the agency has indicated it will accept a resubmission of our biologics license application," Steve Pakola, chief medical officer at Regenxbio, said in a statement.
The agency dropped its demand that Regenxbio include a placebo arm in its clinical trial, a requirement that led to the initial rejection four months ago. The therapy targets mucopolysaccharidosis type II, or Hunter syndrome, a rare X-linked genetic disorder affecting roughly one in 100,000 male births. An enzyme-replacement therapy, Takeda Pharmaceutical Co.'s Elaprase, has long been available for the condition, but the enzyme cannot cross the blood-brain barrier, leaving children with the neurological form to experience progressive cognitive decline and early death.
The reversal follows a similar pattern at UniQure NV, which last week received clearance to submit a gene therapy for Huntington's disease after the agency had previously rejected the application. The string of reversals points to a potential shift in FDA posture toward rare disease treatments, with implications for a pipeline of gene therapies targeting central nervous system disorders.
Regenxbio's therapy, RGX-121, delivers a functional copy of the iduronate-2-sulfatase gene directly to the brain using the company's NAV AAV9 vector platform. The approach addresses the underlying enzyme deficiency that causes toxic accumulation of glycosaminoglycans in neurons, leading to neurodegeneration. The therapy is designed as a one-time administration intended to provide sustained enzyme production in the central nervous system.
The company plans to refile its application in the coming months. Under the FDA's priority review framework, a decision could come within six months of submission.
The broader implications extend beyond Regenxbio. The FDA's willingness to reconsider rejection decisions — particularly by relaxing placebo requirements — could accelerate development timelines for other gene therapy developers targeting rare neurological conditions. Companies such as Solid Biosciences, Voyager Therapeutics, and Sangamo Therapeutics, all pursuing CNS gene therapies, may benefit from a more flexible regulatory environment.
The reversal also comes as the FDA undergoes leadership changes after senior officials appointed by the previous administration resigned or were fired in recent months, the Wall Street Journal reported. Former FDA Commissioner Marty Makary had appeared to publicly disparage the UniQure gene therapy on national television before the agency's latest reversal.
The reversal removes a major regulatory hurdle for Regenxbio, whose shares trade on the Nasdaq under the ticker RGNX. The company's path to market now hinges on a successful resubmission and FDA review, with a decision expected within six months of filing under priority review.
This article is for informational purposes only and does not constitute investment advice.
