REGENXBIO announced it has aligned with the FDA on the next steps for potential accelerated approval of NAVSUNLI for Mucopolysaccharidosis II, with the agency confirming existing clinical data is sufficient and no additional studies or untreated control arm are required, enabling a BLA resubmission in the third quarter of 2026.

Key Highlights

  • The FDA confirmed existing NAVSUNLI data is sufficient for accelerated approval consideration, removing the previously recommended untreated control arm requirement that would have extended development by years.
  • A Type A meeting is scheduled for July, with BLA resubmission targeted for Q3 2026 and FDA review on an expedited basis, with labelling discussions beginning shortly after.
  • Shares surged more than 14% to $8.92, touching an intraday high of $9.12, as investors processed the removal of the programme's most significant regulatory obstacle.

REGENXBIO Inc. (NASDAQ: RGNX) announced Monday that it has reached alignment with the FDA on the regulatory pathway for potential accelerated approval of NAVSUNLI, its one-time gene therapy for Mucopolysaccharidosis II. Shares surged more than 14% to $8.92, with the stock reaching an intraday high of $9.12, as the FDA's confirmation that no additional studies or control arm are required reversed the most commercially consequential element of the February 2026 Complete Response Letter.

MPS II affects approximately 2,000 patients worldwide, making a traditional controlled trial with an untreated arm both ethically complex and practically difficult. The FDA's reversal reflects the agency's renewed commitment under current leadership to applying the accelerated approval pathway appropriately for ultra-rare diseases. The Type A meeting is expected in July, after which the company will resubmit the BLA rapidly in Q3 2026.

NAVSUNLI is designed to deliver the iduronate-2-sulfatase gene to the central nervous system through a one-time administration, providing a permanent source of I2S protein beyond the blood-brain barrier. Current enzyme replacement therapies cannot cross the blood-brain barrier, leaving MPS II's neurological manifestations unaddressed. Following potential approval, NAVSUNLI will be commercialised in the US by NS Pharma, a subsidiary of Nippon Shinyaku. Approval could also generate a Priority Review Voucher whose full proceeds REGENXBIO retains.