REGENXBIO Inc. (NASDAQ:RGNX) today announced it has aligned with the U.S. Food and Drug Administration (FDA) regarding the next steps needed for a potential accelerated approval of NAVSUNLI™ (clemidsogene lanparvovec-sngl, RGX-121), the only potential one-time treatment and gene therapy for Mucopolysaccharidosis II (MPS II), an ultra-rare neurodegenerative disease also known as Hunter syndrome.

Through a recent collaborative discussion, as part of the Company's appeal of the February 2026 NAVSUNLI Complete Response Letter, the FDA acknowledged the existing NAVSUNLI clinical data is sufficient to be considered for the accelerated approval pathway and that the Company does not need to enroll additional patients or conduct additional studies, including the FDA's previously recommended incorporation of an untreated control arm. The FDA asked the Company to request a Type A meeting to review existing longer-term biomarker and clinical data and to resubmit the Biologics License Application (BLA) following this meeting. The FDA stated that it would review REGENXBIO's resubmission on an expedited basis, with labeling discussions to begin shortly following the resubmission. The FDA emphasized its commitment to advancing new therapies for rare diseases under the accelerated approval pathway.

REGENXBIO expects the Type A meeting to take place in July and to resubmit the BLA rapidly following the meeting in Q3 2026.