GC Biopharma, a South Korean pharmaceutical company, announced that the Phase 3 clinical trial results for Hunterase (idursulfase beta), its investigational drug for Hunter Syndrome (MPS II), have been published in Genetics in Medicine, an SCIE-indexed journal.

Conducted at Samsung Medical Center, the Phase 3 clinical trial enrolled 24 newly diagnosed Hunter Syndrome patients with no prior treatment. It evaluated the efficacy and safety of Hunterase over a one-year treatment period.

Hunter Syndrome is a rare genetic disorder caused by a deficiency of iduronate-2-sulfatase (IDS), an enzyme critical for glycosaminoglycan (GAG) catabolism. This deficiency leads to the progressive accumulation of GAGs in various organs and tissues, resulting in multisystemic dysfunction, including joint stiffness and hepatosplenomegaly.

The clinical trial results demonstrated that Hunterase significantly enhanced functional mobility, reduced urinary GAG concentrations, and markedly alleviated hepatosplenomegaly.

In the 6-Minute Walk Test (6-MWT), the primary endpoint of the study, 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. It is a widely used clinical measure for evaluating functional mobility, cardiopulmonary function, muscle strength, and overall physical health. In the context of Hunter syndrome, it serves as a standardized and meaningful indicator of disease progression and quality of life.

In addition to the primary endpoint, the study also achieved positive outcomes in secondary endpoints, including changes in urinary total glycosaminoglycan (GAG) levels, as well as heparan sulfate (HS) and dermatan sulfate (DS) levels. The GAG levels decreased by 71%, while HS and DS levels decreased by 89% and 88%, respectively. Moreover, liver and spleen volumes were reduced by 27% and 26%, respectively, demonstrating the drug’s effectiveness in addressing organ enlargement commonly associated with the disease.

Hunterase also demonstrated a favorable safety profile. Most adverse events were mild or moderate, and no patients discontinued treatment due to side effects. Notably, only 19% of the patients had neutralizing antibodies detected three or more consecutive times, which is significantly lower than the 62.5% observed with the existing treatments. This suggests that Hunterase may offer a more sustained therapeutic effect compared to other currently available therapy.

“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.”

“We are thrilled to publish our encouraging phase 3 clinical trial results”, stated Jae Uk Jeong, Head of R&D at GC Biopharma. “Hunterase, developed in Korea using our proprietary technology, has the potential to significantly improve the lives of patients with Hunter syndrome.”

Hunter Syndrome is an X-linked lysosomal storage disorder, affecting approximately 1 in 100,000 male births. In severe cases, the patients experience early death before they reach adulthood, highlighting the need for early diagnosis and treatment. Currently, two treatments are widely available worldwide for Hunter Syndrome: GC Biopharma’s Hunterase and Takeda’s Elaprase.