$810 Million Turned Into a Rare Disease Revolution with Japan’s Nippon Shinyaku’s and USA’s REGENXBIO’s Partnership

REGENXBIO Inc. and Nippon Shinyaku Co., Ltd. announced a strategic partnership to advance the development and commercialization of RGX-12 and RGX-111. These therapies target Mucopolysaccharidosis II (MPS II) for Hunter syndrome and Mucopolysaccharidosis I (MPS I) Hurler syndrome.

Nippon Shinyaku to Lead Commercialization While REGENXBIO Retains Full Rights to PRV for Gene Therapies 

As part of the agreement, REGENXBIO will receive $110 million upon closing, with the potential to earn up to $700 million in additional milestone payments. This includes $40 million tied to development and regulatory achievements and $660 million linked to sales milestones. The company will also gain significant double-digit royalties on net sales within the U.S. and Asia, the designated Licensed Territory.

Nippon Shinyaku will oversee the commercialization of RGX-121 and RGX-111 in the Licensed Territory, while REGENXBIO will lead future clinical development efforts for both products. REGENXBIO retains full rights to the Priority Review Voucher (PRV) for RGX-121 and will receive 100% of any proceeds from its sale upon potential approval.

REGENXBIO will be responsible for manufacturing both products for clinical and commercial supply in the region. The company also retains the right to develop and commercialize these therapies in other markets. The parties expect to close the transaction by the end of the first quarter of 2025, pending customary conditions and regulatory approvals.

“The structure of the agreement allows us to leverage our expertise in gene therapy manufacturing while also capturing milestones and a meaningful share of future product revenues. RGX-121 could become the first gene therapy for MPS II with potential FDA approval as early as late 2025, and RGX-111 has shown very promising results in the Phase 1/2 study. With Nippon Shinyaku’s expertise in rare disease and strong commercial capabilities, we look forward to working together to get both of these promising candidates across the finish line for patients,” said Curran M. Simpson, President and Chief Executive Officer, REGENXBIO.

RGX-111 and RGX-121 Advancing AAV-Based Gene Therapies for MPS II and MPS I Treatment

Researchers designed RGX-121 as a potential one-time AAV therapeutic to treat boys with MPS II. The protein expressed by RGX-121 is structurally identical to normal iduronate-2-sulfatase (I2S), an enzyme that breaks down specific molecules in the body. The therapy aims to deliver the IDS gene, which encodes I2S, to cells in the central nervous system (CNS). This delivery could provide a continuous supply of I2S beyond the blood-brain barrier, enabling long-term correction of cells throughout the brain and spinal cord.

This therapy has received several designations from the FDA, including Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy. It also holds an advanced therapy medicinal product (ATMP) classification from the European Medicines Agency.

RGX-111 uses the AAV9 vector, a type of virus, to deliver the α-l-iduronidase (IDUA) gene to the CNS. By rapidly delivering IDUA to the brain, RGX-111 could potentially prevent the cognitive decline that typically occurs in patients with MPS I. In February 2023, researchers reported positive interim data from a Phase I/II trial of RGX-111. The product has also received Orphan Drug Product, Rare Pediatric Disease, and Fast Track designations from the FDA.

“RGX-121 and RGX-111 represent one-time gene therapies that can potentially change the course of MPS disease, and we are very pleased to be partnering with REGENXBIO, experts in gene therapy development and manufacturing,” said Toru Nakai, President and Representative Director of Nippon Shinyaku. “We are confident these therapies can bring tremendous value to those living with MPS II and I.”

MPS I and MPS II GAG Buildup Leading to Cognitive and Physical Symptoms

MPS II is a genetic disorder caused by a deficiency in the enzyme I2S, leading to the buildup of glycosaminoglycans (GAGs) in the body. This results in progressive symptoms such as developmental delays, joint stiffness, and organ damage, particularly affecting the nervous system. A deficiency in the enzyme IDUA causes MPS I, leading to GAG accumulation and symptoms such as developmental delays and skeletal abnormalities. Both conditions are life-threatening without treatment.

Currently, enzyme replacement therapies (ERT) are the primary treatments for both MPS I and MPS II. For MPS II, idursulfase (Elaprase) helps replace the missing I2S enzyme, while laronidase (Aldurazyme) serves the same function for MPS I by replacing IDUA. While these treatments alleviate some symptoms, they do not address neurological damage. Hematopoietic stem cell transplantation (HSCT) is another option, but its benefits are limited to early-stage disease. Researchers are developing new therapies, such as gene therapy, to offer more comprehensive and long-term solutions for these rare diseases.

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Author

Denisse Sandoval