MEDIPAL and JCR Pharmaceuticals Dose First Participant in Global Phase I/II Trial of JR-446 for MPS IIIB

Global Clinical Trial Begins for Rare Sanfilippo Syndrome Type B

MEDIPAL HOLDINGS CORPORATION and JCR Pharmaceuticals Co., Ltd. have announced that the first participant has been dosed in the global Phase I/II clinical trial of JR-446.

JR-446 is being developed as a potential treatment for mucopolysaccharidosis type IIIB (MPS IIIB), also known as Sanfilippo syndrome type B.

The investigational therapy is designed to cross the blood-brain barrier and deliver treatment into the brain. JCR Pharmaceuticals developed JR-446 using its proprietary J-Brain Cargo technology.

MEDIPAL holds commercialization rights for JR-446 outside Japan.

JR-446 Is Being Developed for MPS IIIB

MPS IIIB is an ultra-rare lysosomal storage disorder that can cause serious problems in the central nervous system.

Lysosomal storage disorders happen when the body's cells cannot properly break down certain substances. In MPS IIIB, a substance called heparan sulfate builds up in cells, including cells in the brain.

This buildup can cause progressive neurological problems.

MPS IIIB is estimated to affect around 500 to 1,000 people worldwide. There is currently no approved treatment specifically for the disease.

The condition can affect speech, behavior, sleep and neurocognitive development. As the disease progresses, patients may lose skills and independence, creating significant challenges for both patients and their families.

Global Phase I/II Trial Has Started

The new global Phase I/II trial is being conducted in multiple countries and clinical centres.

The study is an open-label trial, meaning participants and researchers know that the investigational treatment is being given rather than using a blinded design.

The trial is enrolling children with MPS IIIB who are under six years of age.

The study will help researchers evaluate JR-446 in this young patient population and collect information about its safety, tolerability and potential treatment effects.

The trial is registered on ClinicalTrials.gov under identifier NCT07640984.

Why Crossing the Blood-Brain Barrier Matters

One of the major challenges in treating diseases that affect the brain is getting medicines from the bloodstream into the central nervous system.

The blood-brain barrier is a natural protective system that limits the movement of many substances from the blood into the brain.

For diseases such as MPS IIIB, this creates an important treatment challenge because the disease can cause significant damage in the brain.

JR-446 has been designed to address this problem.

JCR developed the medicine using its J-Brain Cargo technology, which is designed to help therapeutic proteins cross the blood-brain barrier and reach the central nervous system.

What Is J-Brain Cargo Technology?

J-Brain Cargo is JCR Pharmaceuticals' proprietary technology for delivering biotherapeutic medicines across the blood-brain barrier.

The platform is designed to help medicines reach both the body and the brain.

This approach is particularly relevant for lysosomal storage disorders in which disease-related material can accumulate in the central nervous system.

JCR has already developed a medicine using the same platform. IZCARGO, whose international nonproprietary name is pabinafusp alfa, is approved in Japan and the United Arab Emirates for the treatment of a lysosomal storage disorder.

JR-446 is another program in which the companies are applying this approach to a different rare disease.

JR-446 Targets an Enzyme Deficiency

JR-446 is a blood-brain barrier-penetrating α-N-acetylglucosaminidase.

In simple terms, the treatment is designed to provide an enzyme that is needed to help break down substances that accumulate because of MPS IIIB.

MPS IIIB is caused by pathogenic mutations in the NAGLU gene. This gene provides instructions for making an enzyme involved in breaking down heparan sulfate.

When this enzyme does not work properly, heparan sulfate can accumulate, including in the central nervous system.

JR-446 is being developed to help address this underlying biological problem by delivering the enzyme to areas of the body and brain affected by the disease.

Researchers See a Major Unmet Need

The start of the Phase I/II trial is particularly important because people living with MPS IIIB currently have no approved treatment option.

Dr. Irene Chang, the principal investigator and an associate professor of pediatrics at the University of California, San Francisco, said the first patient dosing is an important step for the MPS IIIB community.

She highlighted the impact the disease can have on neurocognitive development, independence and quality of life.

She also acknowledged the patients, caregivers and clinical teams involved in making the study possible.

JR-446 Has Also Been Studied in Japan

The global Phase I/II trial is not the only clinical study evaluating JR-446.

A separate Phase I/II study, known as JR-446-101, is already ongoing in Japan.

This Japanese study is being conducted under the co-development agreement between MEDIPAL and JCR.

Data from the clinical development program will help the companies better understand the safety and potential benefits of JR-446 as development continues.

JR-446 Received Orphan Drug Designations

JR-446 has also received orphan drug designation in several major regions.

In 2025, the investigational treatment received orphan drug designation in the United States, the European Union and Japan.

Orphan drug programs are intended to support the development of medicines for rare diseases where patient populations are small and treatment options may be limited.

These designations reflect the rare-disease focus of the JR-446 development program.

MEDIPAL and JCR Signed Their Collaboration in 2023

MEDIPAL and JCR began their partnership for JR-446 in September 2023.

Under their agreement, the companies are working together on the development and commercialization of the treatment.

MEDIPAL holds exclusive worldwide commercialization rights for JR-446 outside Japan and has the right to sublicense those rights.

JCR is responsible for leading the global Phase I/II clinical trial and development activities on behalf of MEDIPAL as the study sponsor.

In Japan, the companies are working under a separate co-development and commercialization agreement.

What Happens Next for JR-446?

The global Phase I/II study will now continue to evaluate JR-446 in young patients with MPS IIIB.

Researchers will collect clinical data as participants receive treatment and will continue monitoring the safety and potential effects of the therapy.

The results from this study, together with the ongoing Japanese Phase I/II trial, will help determine the next steps in the clinical development program.

MEDIPAL and JCR said they remain focused on advancing JR-446 with the aim of developing a new treatment option for people living with MPS IIIB.

About MEDIPAL HOLDINGS CORPORATION

MEDIPAL HOLDINGS CORPORATION is a Japanese holding company that manages and supports businesses within the MEDIPAL Group.

The group operates across areas including prescription pharmaceutical wholesale, cosmetics and over-the-counter pharmaceutical wholesale, animal health products, food processing raw materials and related businesses.

MEDIPAL is responsible for the commercialization of JR-446 outside Japan under its agreement with JCR Pharmaceuticals.

About JCR Pharmaceuticals

JCR Pharmaceuticals is a specialty pharmaceutical company based in Japan that develops medicines for rare diseases and other complex healthcare conditions.

The company has a long history of developing treatments in areas such as growth disorders, MPS II, Fabry disease, acute graft-versus-host disease and renal anemia.

JCR is also developing treatments for several other rare diseases, including MPS I, MPS IIIA and MPS IIIB.

Its J-Brain Cargo platform remains an important part of the company's work to deliver biotherapeutic medicines into the central nervous system.

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