FDA Approves Biologics License Application for Mucopolysaccharidosis II Therapy

NS Pharma, Inc., based in Paramus, New Jersey, has announced that the U.S. Food and Drug Administration (FDA) has accepted the Biologics License Application (BLA) for RGX-121, an investigational gene therapy developed by REGENXBIO Inc. RGX-121 is designed to treat Mucopolysaccharidosis II (MPS II), a rare genetic disorder. The application has been granted Priority Review, with a decision expected by November 9, 2025. This development follows a strategic partnership formed in January 2025 between Nippon Shinyaku, the parent company of NS Pharma, and REGENXBIO to develop and commercialize RGX-121 and another therapy, RGX-111, which targets MPS I. If approved, NS Pharma will oversee the commercialization of RGX-121 in the United States.

Dr. Yukiteru Sugiyama, President of NS Pharma, expressed optimism about the FDA's decision, highlighting the potential impact of RGX-121 on the MPS community. He emphasized the significance of the partnership with REGENXBIO in offering new treatment possibilities for families affected by MPS.

RGX-121, known scientifically as clemidsogene lanparvovec, is an innovative one-time therapy utilizing AAV (adeno-associated virus) to deliver the iduronate-2-sulfatase (IDS) gene directly to the central nervous system (CNS). This delivery aims to ensure a continuous supply of the IDS enzyme, which is structurally similar to the naturally occurring enzyme, thereby enabling long-term cross-correction of cells across the CNS. The FDA has recognized RGX-121 with several designations, including Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy, underscoring its potential to address unmet medical needs.

MPS II, also known as Hunter Syndrome, is an X-linked recessive condition caused by a deficiency in the IDS enzyme. This deficiency leads to the accumulation of glycosaminoglycans (GAGs) such as heparan sulfate in tissues, resulting in dysfunction of cells, tissues, and organs, including the CNS. Severe cases of MPS II can show developmental delays as early as 18 to 24 months. Current treatments fail to adequately address the neurological aspects of MPS II, highlighting an urgent need for innovative therapeutic options. Biomarkers like heparan sulfate (HS) D2S6 are pivotal in correlating the neurocognitive symptoms of the disorder.

REGENXBIO Inc., headquartered in Rockville, Maryland, is at the forefront of developing gene therapies. Established in 2009, the company is dedicated to improving health outcomes through the potential of gene therapy, particularly in the field of AAV therapeutics. Their collaboration with Nippon Shinyaku and NS Pharma underscores their commitment to advancing treatments for rare genetic disorders like MPS II.

NS Pharma, a subsidiary of Japan-based Nippon Shinyaku Co., Ltd., plays a crucial role in bringing advanced medical therapies to the U.S. market. Through its partnership with REGENXBIO, NS Pharma aims to provide new hope for patients and families impacted by MPS II by potentially delivering a groundbreaking treatment option that addresses both the systemic and neurological challenges of the disease.