REGENXBIO and FDA Collaborate on Accelerated Approval for NAVSUNLI™ Gene Therapy

REGENXBIO Moves Forward with NAVSUNLI™ Gene Therapy

In a significant stride towards addressing the critical needs of patients suffering from Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome, REGENXBIO Inc. has announced alignment with the U.S. Food and Drug Administration (FDA) regarding the next steps for the accelerated approval of its gene therapy, NAVSUNLI™ (clemidsogene lanparvovec-sngl, RGX-121). This therapy represents a pioneering one-time treatment option for a debilitating condition that has long required novel solutions.

FDA's Support of Accelerated Approval Route

On June 22, 2026, REGENXBIO declared that recent discussions with the FDA indicated no further studies are necessary. The FDA confirmed that they would review existing clinical data from the CAMPSIITE® study, which will be considered under the accelerated approval pathway. This marks a pivotal moment since it negates the need for enrolling additional patients or conducting further studies that were previously recommended.

The company plans to resubmit the Biologics License Application (BLA) in the upcoming third quarter of 2026, with a Type A meeting with the FDA scheduled for July. During this meeting, REGENXBIO will discuss the analysis of long-term data, which serves to bolster the case for the therapy’s approval. Following the resubmission, the division of the FDA will begin discussions on labeling almost immediately, indicating an efficient process moving forward.

Patrick Simpson, REGENXBIO’s President and CEO, expressed optimism about the FDA’s responsiveness under the new leadership, recognizing their commitment to rare diseases. Simpson highlighted the urgency of providing solutions for families affected by Hunter syndrome, emphasizing that it is a progressive and devastating condition.

The Urgency of Treatment

Scott Loiler, Ph.D., the Chief Scientific Officer of the National MPS Society, articulated the sentiment strongly held within the MPS community. He acknowledged the pressing necessity for innovative treatments and praised the FDA's commitment to reviewing NAVSUNLI through an accelerated lens. This resonates deeply, as the majority of individuals living with Hunter syndrome encounter severe symptoms and developmental delays as early as 18 to 24 months.

MPS II is an incredibly rare, X-linked recessive disorder stemming from a deficiency in the enzyme iduronate-2-sulfatase (I2S). This deficiency leads to the detrimental accumulation of glycosaminoglycans (GAGs) in various tissues, ultimately causing extensive dysfunction across cells, tissues, and organs, including the central nervous system (CNS).

Understanding NAVSUNLI™

NAVSUNLI is designed to administer the IDS gene directly to the CNS. The ultimate goal is to provide a continuous supply of the I2S protein beyond the blood-brain barrier, potentially resulting in long-term treatment efficacy. Notably, the therapeutic protein expressed by NAVSUNLI is structurally identical to the natural I2S protein, ensuring compatibility and effectiveness. The FDA has already recognized NAVSUNLI with multiple designations, including Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT).

Once approved, NAVSUNLI will be commercially made available through NS Pharma, Inc., a subsidiary of Nippon Shinyaku, with an opportunity for REGENXBIO to obtain a Priority Review Voucher. The company retains full rights related to any potential revenue associated with the voucher, indicating a significant commercial potential if NAVSUNLI receives approval.

Looking Ahead

With contingencies structured around the upcoming BLA resubmission, REGENXBIO aims to keep the momentum moving swiftly to ensure that boys diagnosed with Hunter syndrome gain access to what could be a transformative one-time treatment. The commitment displayed by REGENXBIO, along with the FDA’s approach to facilitating the approval process, highlights a beacon of hope in an arena that has historically faced enormous challenges. As REGENXBIO continues to pioneer AAV gene therapy solutions, the impact of NAVSUNLI could extend beyond specific patients, setting a precedent for innovative treatment pathways in rare diseases.

For more comprehensive information about REGENXBIO and its notable advancements, including NAVSUNLI, feel free to visit www.REGENXBIO.com.