FDA gives priority review to REGENXBIO gene therapy RGX-121 for the treatment of mucopolysaccharidosis type II, clinical progress attracts attention

Recently, REGENXBIOThe biotechnology company announced its gene therapyClemidogene for the rare genetic disease mucopolysaccharidosis II type (MPS II, also known as Hunter syndrome) Lanparvovec (RGX-121) has been formally accepted for biologics license application (BLA) by the U.S. Food and Drug Administration (FDA). FDA not only accepted the application, but also granted the project priority review status. It is expected to complete the review work before November 9 this year. This indicates that the treatment plan is expected to accelerate its entry into the clinical application stage.

MucopolysaccharidosisII type is a rare X chromosomal recessive genetic disease caused mainly by the lysosomal enzyme iduronic acid-2-Sulfatase (I2S) deficiency leads to abnormal accumulation of glycosaminoglycans (GAGs), especially heparan sulfate (HS), in the body. This accumulation can impair the function of multiple organs and systems, especially the central nervous system, causing severe cognitive and physical impairments in patients. At present, the main treatment for MPS II is enzyme replacement therapy, which supplements the missing I2S enzyme through intravenous injection. However, for patients with neurological symptoms, enzyme replacement therapy has limited efficacy. In addition, some patients require surgery due to abnormal joint development.

RGX-121As an advanced gene therapy, AAV9 viral vector is used to deliver genes encoding human I2S enzymes to the central nervous system. In this way, the patient's brain cells can continue to produce the missing enzyme, breaking through the blood-brain barrier, a treatment difficulty, and potentially achieving a fundamental treatment of the disease. This gene therapy has not only obtained orphan drug status and rare pediatric disease designation from the FDA, but also has many advantages of fast track and regenerative medicine advanced therapy designation. RGX-121 is expected to become the world’s first one-time gene therapy forMPS IICarry out fundamental treatment of the cause.

At the 2024 World Symposium, REGENXBIO announced key data from its multi-phase clinical trial (CAMPSIITE, No. NCT03566043). The trial results showed that MPS treated with RGX-121 In IIpatients, after 16 weeks of administration, the level of the key disease biomarker D2S6 in the cerebrospinal fluid dropped significantly, with an average reduction of 86%, close to the normal range. The reduction of D2S6 represents effective control of brain disease activity. In addition, long-term follow-up data show that 80% of patients do not need to continue receiving traditional enzyme replacement intravenous infusion after treatment, showing significant clinical benefit and good tolerability. As of 2024year1month3day, no 25 patients who have received the treatment have experienced serious adverse reactions, and safety is guaranteed.

Overall, the development and clinical progress of RGX-121 has brought new treatment hope to patients with mucopolysaccharidosis II type. Its one-time gene therapy model not only breaks through the limitations of traditional enzyme replacement therapy, but may also completely change the treatment landscape of diseases. With the progress of FDA approval in the future, this drug is expected to benefit more patients as soon as possible and promote the treatment of rare diseases into a new era.

References:REGENXBIO Announces FDA Acceptance and Priority Review of the BLA for RGX-121 for MPS II. Retrieved May 13, 2025.