MEDIPAL and JCR Pharmaceuticals Dose First Patient in Global Phase I/II Trial of JR-446 for MPS IIIB
MEDIPAL HOLDINGS CORPORATION and JCR Pharmaceuticals Co., Ltd. (TSE: 4552) announced that the first participant has been dosed in the global Phase I/II clinical trial of JR-446, an investigational therapy being developed for mucopolysaccharidosis type IIIB (MPS IIIB), also known as Sanfilippo syndrome type B.
JR-446 is a blood-brain barrier-penetrating α-N-acetylglucosaminidase developed by JCR Pharmaceuticals using its proprietary J-Brain Cargo® technology. The companies are advancing the program with the goal of developing a treatment option for patients affected by MPS IIIB, an ultra-rare lysosomal storage disorder associated with severe and progressive central nervous system impairment.
The initiation of the global Phase I/II study marks an important milestone for the JR-446 development program and for the MPS IIIB community, where significant unmet medical needs remain. There are currently no approved treatments for the disease, which can profoundly affect neurocognitive development, independence and quality of life.
Under a licensing and collaboration agreement between the companies, MEDIPAL holds commercialization rights for JR-446 outside Japan, while JCR is responsible for leading the global Phase I/II development program on MEDIPAL’s behalf.
JR-446 Advances Into Global Clinical Development
The first participant dosing represents the transition of JR-446 into a new stage of global clinical development. The Phase I/II study is designed as a global, multicenter, open-label trial enrolling patients with MPS IIIB who are under six years of age.
MPS IIIB is caused by deficiency of the lysosomal enzyme α-N-acetylglucosaminidase. The resulting impairment in lysosomal breakdown contributes to the accumulation of substances within cells and can lead to progressive damage across multiple organs and, particularly, the central nervous system.
Because neurological involvement is a defining and particularly serious aspect of MPS IIIB, delivering a therapeutic enzyme to the brain has historically represented a major challenge in developing potential treatments for the disease.
JR-446 has been developed with the objective of addressing this challenge. The therapy incorporates JCR Pharmaceuticals’ proprietary J-Brain Cargo technology, which is designed to facilitate the transport of therapeutic molecules across the blood-brain barrier.
The companies are evaluating whether this approach can enable JR-446 to reach the central nervous system and potentially address aspects of the underlying disease process.
The first participant dosing therefore represents more than a clinical development milestone. It begins an international clinical evaluation of an investigational approach specifically designed to overcome one of the major barriers associated with treating neurological manifestations of lysosomal storage disorders.
Significant Unmet Need in MPS IIIB
MPS IIIB is an ultra-rare lysosomal storage disorder estimated to affect approximately 500 to 1,000 people worldwide.
The disease can have a devastating impact on affected children and their families. Progressive central nervous system impairment can affect neurocognitive development and gradually reduce patients’ ability to maintain independence and perform everyday activities.
The disease is also associated with substantial challenges for caregivers, who may face increasing support needs as the condition progresses.
Despite the serious consequences associated with MPS IIIB, there is currently no approved treatment for the condition. This leaves patients and families with limited options and highlights the need for therapies capable of addressing the underlying biological mechanisms of the disease.
The first patient dosed in the global Phase I/II trial is therefore an important step toward determining whether JR-446 could eventually provide a therapeutic option for this patient population.
Dr. Irene Chang, Principal Investigator and Associate Professor of Pediatrics in the Section of Biochemical Genetics within the Division of Medical Genetics at the University of California, San Francisco (UCSF), described the clinical milestone as significant for the MPS IIIB community.
She emphasized that the disease is a devastating and life-limiting lysosomal storage disorder that can affect neurocognitive development, independence and quality of life. She also highlighted the continuing unmet medical needs faced by patients and their families.
According to Dr. Chang, the research team is encouraged by the opportunity to take another step in evaluating the investigational therapy and expressed appreciation for the patients, caregivers and study teams contributing to the program.
J-Brain Cargo Technology Supports JR-446 Development
A central element of JR-446 is JCR Pharmaceuticals’ proprietary J-Brain Cargo technology.
The blood-brain barrier presents a significant challenge for the development of therapies targeting diseases affecting the central nervous system. While the barrier serves an essential protective function, it can also restrict the movement of therapeutic molecules from the bloodstream into the brain.
JCR’s J-Brain Cargo platform was developed to facilitate delivery of therapeutic molecules across the blood-brain barrier. JR-446 is an α-N-acetylglucosaminidase engineered using this technology with the objective of enabling enzyme replacement within the central nervous system.
For MPS IIIB, this approach is particularly relevant because neurological disease is a major component of the disorder.
The clinical development program will provide an opportunity to assess the safety, tolerability and other characteristics of JR-446 in young patients with the disease, while continuing to evaluate the potential of the blood-brain barrier-penetrating approach.
The companies have not stated that the investigational therapy has demonstrated clinical efficacy in the current global Phase I/II study. Accordingly, JR-446 remains an investigational product and its potential benefits and risks will need to be established through clinical development.
Global Phase I/II Trial Focuses on Young Patients
The newly initiated study is a global, multicenter, open-label Phase I/II clinical trial involving patients with MPS IIIB who are younger than six years of age.
The trial is registered under ClinicalTrials.gov identifier NCT07640984.
Conducting the study across multiple centers is intended to support the evaluation of JR-446 in an international patient population affected by this rare disease. The enrollment of young children reflects the importance of evaluating potential treatment approaches early in the course of a progressive pediatric disorder.
Because MPS IIIB can cause progressive neurological deterioration, earlier intervention may be an important consideration in the development of future therapies. However, the clinical study will be necessary to determine the safety and potential therapeutic effects of JR-446 in the intended patient population.
The open-label design means that participants and investigators are aware of the treatment being administered. As with other early-stage clinical studies, data generated through the Phase I/II program will help guide subsequent development decisions.
Japan-Based Clinical Development Also Continues
The global Phase I/II program builds on an existing clinical development effort for JR-446 in Japan.
A separate Phase I/II study, designated JR-446-101 and registered under ClinicalTrials.gov identifier NCT06488924, is ongoing in Japan under the companies’ co-development agreement.
The Japanese program represents another component of the companies’ efforts to evaluate JR-446 and establish its potential as a treatment for MPS IIIB.
The continuation of clinical development in Japan alongside the global program reflects the companies’ broader strategy of advancing the therapy across multiple geographic markets.
The companies entered into their collaboration in September 2023. The agreement established a framework for commercialization and development of JR-446 in Japan and internationally.
MEDIPAL Holds Commercialization Rights Outside Japan
MEDIPAL and JCR entered into a licensing agreement in September 2023 covering commercialization of JR-446 for MPS IIIB outside Japan, alongside a co-development and commercialization agreement for the Japanese market.
Under the arrangement, MEDIPAL holds exclusive worldwide commercialization rights outside Japan, including the right to sublicense.
JCR Pharmaceuticals is leading the global Phase I/II trial and related development activities as the sponsor on behalf of MEDIPAL.
The collaboration combines JCR’s expertise in developing therapies and its J-Brain Cargo technology with MEDIPAL’s commercialization capabilities and international strategy.
For an ultra-rare disease such as MPS IIIB, collaboration can be particularly important because patient populations are geographically dispersed and clinical development requires specialized expertise and coordinated recruitment.
The companies’ partnership is intended to support the advancement of JR-446 across key markets while maintaining a coordinated development strategy.
Orphan Drug Designations in Three Regions
JR-446 has also received orphan drug designation in the United States, the European Union and Japan.
The designations were granted in 2025 and reflect the rare nature of MPS IIIB and the significant unmet medical need associated with the disease.
Orphan drug frameworks are intended to encourage the development of therapies for rare diseases, where small patient populations can create significant challenges for conventional drug development and commercialization.
While orphan drug designation does not establish that a medicine is safe or effective, it can provide a regulatory framework intended to support the development of treatments for conditions affecting relatively small patient populations.
For MEDIPAL and JCR, the orphan designations across the three regions provide an important component of the regulatory development pathway for JR-446 as the program progresses through clinical testing.
Advancing an Investigational Treatment for MPS IIIB
The first participant dosing in the global Phase I/II trial represents a major development milestone for JR-446 and follows several years of research and collaboration between MEDIPAL and JCR.
The program is focused on a particularly challenging disease area in which patients can experience severe central nervous system impairment and progressive effects on development and quality of life.
JCR’s use of the J-Brain Cargo technology in the development of JR-446 is intended to address the blood-brain barrier and potentially enable delivery of the enzyme to the central nervous system.
The ongoing clinical studies will be important in determining whether the investigational therapy can demonstrate an acceptable safety profile and meaningful therapeutic potential in patients with MPS IIIB.
The companies remain focused on advancing JR-446 as efficiently as possible, with the stated goal of bringing a new treatment option to patients and families affected by the disorder.
For the MPS IIIB community, where no approved treatment is currently available, the start of the global Phase I/II trial provides a new stage of clinical investigation into a potential disease-directed therapy.
As the international study progresses, data from the program will help determine the future development path for JR-446. MEDIPAL and JCR will continue to evaluate the investigational therapy through their global collaboration, while JCR maintains responsibility for leading the clinical development program on behalf of MEDIPAL.
The first participant dosing ultimately marks the beginning of an important global evaluation of JR-446 and its potential to address the substantial unmet needs associated with MPS IIIB.
About Mucopolysaccharidosis Type IIIB (Sanfilippo Syndrome Type B)
Mucopolysaccharidosis type IIIB, or Sanfilippo syndrome type B, is an autosomal recessive disease caused by pathogenic mutations in the NAGLU gene, encoding a lysosomal enzyme involved in the degradation of heparan sulfate. With the accumulation of heparan sulfate in the central nervous system in the brain, individuals with this condition present rapid neurological decline, including sleep disorders, loss of speech, and behavioral changes, which may significantly affect the quality of life of patients and their families.
About the J-Brain Cargo® Platform Technology
JCR Pharmaceuticals has developed a proprietary blood-brain barrier (BBB)-penetrating technology, J-Brain Cargo®, to bring biotherapeutics into the central nervous system (CNS). The first drug developed based on this technology is IZCARGO™ (INN: pabinafusp alfa), which is approved in Japan and the United Arab Emirates for the treatment of a lysosomal storage disorder (LSD). With J-Brain Cargo®, JCR and MEDIPAL seek to address the unresolved clinical challenges of LSDs by delivering the enzyme to both the body and the brain.
About MEDIPAL HOLDINGS CORPORATION
MEDIPAL is a holding company which controls, administers and supports the operating activities of companies in which it holds shares in the Prescription Pharmaceutical Wholesale Business; the Cosmetics, Daily Necessities and OTC Pharmaceutical Wholesale Business; and the Animal Health Products and Food Processing Raw Materials Wholesale and Related Business, and conducts business development for the MEDIPAL Group. For more information, visit https://www.medipal.co.jp/english/.
About JCR Pharmaceuticals Co., Ltd.
JCR Pharmaceuticals Co., Ltd. is a global specialty pharmaceutical company that develops treatments that go beyond rare diseases to solve the world’s most complex healthcare challenges. JCR continues to build upon our 50-year legacy in Japan while expanding its global footprint into the US, Europe, and Latin America. JCR’s innovative therapies address conditions like growth disorder, MPS II, Fabry disease, acute graft-versus-host disease, and renal anemia. JCR is also developing treatments for rare diseases like MPS I, MPS II, MPS IIIA and B, and more. For more information, visit https://jcrpharm.com/.