RGNX Retail Investors See Hope As FDA Reopens Door For Regenxbio’s Hunter Syndrome Therapy

The U.S. Food and Drug Administration has agreed to reconsider Regenxbio’s application for its experimental gene therapy Navsunli.

• Regenxbio plans to resubmit its application for Navsunli in the third quarter.
• Navsunli is a one-time gene therapy intended to replace the faulty gene responsible for Hunter syndrome.
• Regenxbio CEO Curran Simpson said FDA could allow for a faster review process once the application is refiled.

Shares of Regenxbio (RGNX) jumped 12% in pre-market trading on Monday, as the biotech firm received a major boost after the U.S. Food and Drug Administration agreed to reconsider its application for its experimental gene therapy designed to treat Hunter syndrome.

Regenxbio said the FDA indicated that its review of Navsunli could be completed in as little as two months following the therapy’s resubmission.

Regenxbio To Resubmit Navsunli Application in Q3

The FDA had initially agreed to a study design that did not include a placebo group. The company tested Navsunli in 13 patients based on the discussions with the agency. However, in 2025, the FDA requested additional data and raised concerns about the lack of a placebo arm.

The agency ultimately rejected the application in February 2026 and called for a new placebo-controlled trial.

Regenxbio plans to resubmit its application in the third quarter, following a formal dispute-resolution meeting with the FDA, expected in July. Regenxbio CEO Curran Simpson said recent discussions with FDA officials have been encouraging and could lead to a faster review process once the application is refiled.

Navsunli Approval Could Be A Game Changer

Navsunli is a one-time gene therapy intended to replace the faulty gene responsible for Hunter syndrome. The treatment aims to restore production of a critical protein that prevents harmful substances from accumulating in the brain and other tissues.

Hunter syndrome affects roughly 2,000 people worldwide, primarily boys, and often causes progressive neurological decline, irreversible brain damage, and premature death.

Approvals After FDA Leadership Overhaul

The development follows a similar breakthrough for Replimune (REPL), which recently reached an agreement with the FDA to resubmit its application for RP1, a treatment for advanced melanoma. Replimune’s filing had been rejected twice before regulators outlined a path forward.

The agreement came shortly after a leadership change at the FDA, with agency chief Marty Makary stepping down in May. During his tenure, several companies criticized the agency’s handling of drug reviews and approval decisions.

RGNX Traders Remain Bullish

Retail sentiment on Stocktwits surrounding RGNX remained in the ‘extremely bullish’ territory over the past 24 hours, accompanied by ‘extremely high’ message volumes. It was among the top trending tickers at the time of writing.

One user believes the stock may finally cross $9 “after a long time.”

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RGNX shares have crashed more than 44% so far this year.

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