GC Biopharma announced that Phase 3 clinical trial results for Hunterase (idursulfase beta), its investigational treatment for Hunter Syndrome (MPS II), have been published in Genetics in Medicine, an SCIE-indexed journal. The study represents the first Phase 3 trial in Asian patients to validate the clinical efficacy of this enzyme replacement therapy for the rare genetic disorder.
Trial Design and Patient Population
The Phase 3 clinical trial was conducted at Samsung Medical Center and enrolled 24 newly diagnosed Hunter Syndrome patients with no prior treatment. The study evaluated the efficacy and safety of Hunterase over a one-year treatment period, focusing on functional mobility as the primary endpoint.
Hunter Syndrome is an X-linked lysosomal storage disorder affecting approximately 1 in 100,000 male births. The condition is caused by a deficiency of iduronate-2-sulfatase (IDS), an enzyme critical for glycosaminoglycan (GAG) catabolism. This deficiency leads to progressive accumulation of GAGs in various organs and tissues, resulting in multisystemic dysfunction, including joint stiffness and hepatosplenomegaly.
Primary Endpoint Results
In the 6-Minute Walk Test (6-MWT), the study's primary endpoint, patients treated with Hunterase walked an average of 62.2 meters more after treatment. This improvement was more than eight times greater compared to the placebo group, which saw an average increase of just 7.3 meters.
The 6-MWT measures the distance a patient can walk on a flat surface within 6 minutes and serves as a widely used clinical measure for evaluating functional mobility, cardiopulmonary function, muscle strength, and overall physical health. In Hunter syndrome patients, it provides a standardized and meaningful indicator of disease progression and quality of life.
Secondary Endpoints and Metabolic Improvements
The study achieved positive outcomes across multiple secondary endpoints, demonstrating Hunterase's effectiveness in addressing the underlying metabolic dysfunction of Hunter Syndrome. Urinary total glycosaminoglycan (GAG) levels decreased by 71%, while heparan sulfate (HS) and dermatan sulfate (DS) levels decreased by 89% and 88%, respectively.
Additionally, the treatment demonstrated significant effects on organ enlargement commonly associated with the disease. Liver and spleen volumes were reduced by 27% and 26%, respectively, indicating the drug's effectiveness in addressing hepatosplenomegaly.
Safety Profile and Immunogenicity
Hunterase demonstrated a favorable safety profile throughout the one-year treatment period. Most adverse events were mild or moderate, and no patients discontinued treatment due to side effects.
A particularly notable finding was the low rate of neutralizing antibody formation. Only 19% of patients had neutralizing antibodies detected three or more consecutive times, which is significantly lower than the 62.5% observed with existing treatments. This suggests that Hunterase may offer a more sustained therapeutic effect compared to other currently available therapies.
Clinical Significance and Expert Commentary
"This clinical trial is especially meaningful as it represents the first Phase 3 study in Asian patients to validate the clinical efficacy of Hunterase," said Professor Young Bae Sohn of Ajou University School of Medicine and Ajou University Hospital, the journal's first author. "The results showed significant clinical improvement not only in metabolic markers but also in organ size normalization and restoration of physical mobility."
Jae Uk Jeong, Head of R&D at GC Biopharma, stated, "We are thrilled to publish our encouraging phase 3 clinical trial results. Hunterase, developed in Korea using our proprietary technology, has the potential to significantly improve the lives of patients with Hunter syndrome."
Current Treatment Landscape
Hunter Syndrome patients face significant challenges, with severe cases experiencing early death before reaching adulthood, highlighting the critical need for early diagnosis and treatment. Currently, two treatments are widely available worldwide for Hunter Syndrome: GC Biopharma's Hunterase and Takeda's Elaprase.
The publication of these Phase 3 results in a peer-reviewed journal represents an important milestone for GC Biopharma, a South Korean biopharmaceutical company with over half a century of experience in developing plasma derivatives and vaccines. The company has been expanding its global presence, including successful US market entry of Alyglo (intravenous immunoglobulin G) in 2024.
