Japan's Ministry of Health, Labor and Welfare (MHLW) has granted Orphan Regenerative Medicine Product Designation to OTL-200 (atidarsagene autotemcel), an investigational ex vivo autologous hematopoietic stem cell gene therapy developed by Kyowa Kirin and Orchard Therapeutics for treating early-onset metachromatic leukodystrophy (MLD). The designation covers pre-symptomatic late infantile, pre-symptomatic early juvenile, and early-symptomatic early juvenile forms of the disease.
Addressing an Ultra-Rare Fatal Disease
MLD is an ultra-rare, rapidly progressive, irreversible and ultimately fatal neurometabolic disease that affects approximately one in 100,000 live births. The condition is caused by an error in the gene responsible for encoding the enzyme arylsulfatase A (ARSA), leading to neurological damage and developmental regression.
In the most severe form of MLD, babies develop normally but in late infancy start to rapidly lose the ability to walk, talk and interact with the world around them. These children eventually deteriorate into a vegetative state, which may require 24-hour intensive care, and the majority pass away within five years of symptom onset. In its late infantile form, mortality at five or ten years from onset is estimated at 75 percent and 100 percent, respectively.
Currently, there are no approved therapies for MLD in Japan beyond supportive and end-of-life care, creating an enormous emotional and financial burden on families.
Gene Therapy Mechanism
OTL-200 aims to correct the underlying genetic cause of MLD by inserting one or more functional copies of the human ARSA gene ex vivo (outside the body) into the genome of a patient's own hematopoietic stem cells (HSCs) using a lentiviral vector. The genetically repaired cells are infused back into the patient, where, once engrafted, they differentiate into multiple cell types, some of which migrate across the blood-brain barrier into the central nervous system and express the functional enzyme.
"This designation underscores the importance of OTL-200 as an innovative treatment for young patients suffering from MLD, a life-threatening and severe neurodegenerative disease for which no treatment has existed until now," said Takeyoshi Yamashita, Ph.D., Executive Vice President and Chief Medical Officer of Kyowa Kirin.
Global Regulatory Progress
Beyond Japan, OTL-200 has received Orphan Drug Designation and Priority Review from the Saudi Food and Drug Authority (SFDA) for the treatment of early-onset MLD. The SFDA programs are intended to encourage development of new therapies for rare and ultra-rare diseases by streamlining and expediting the review process.
Orchard Therapeutics is working to qualify a treatment center in the Kingdom of Saudi Arabia to administer the therapy to eligible children with MLD from the country and surrounding regions through pre-approval access pathways and eventually commercially, if approved.
OTL-200 is already approved as Lenmeldy in the United States and Libmeldy in Europe, making it the only therapy intended to correct the underlying cause of MLD for eligible patients.
Clinical Development Plans
Kyowa Kirin is currently preparing the potential initiation of a clinical trial for OTL-200 in children with pre-symptomatic late infantile, pre-symptomatic early juvenile, and early-symptomatic early juvenile MLD in Japan.
"Our hematopoietic stem cell gene therapy approach continues to demonstrate great promise in addressing diseases for which current treatments are limited or do not exist," said Bobby Gaspar, M.D., Ph.D., chief executive officer of Orchard Therapeutics. "Bringing these potentially transformative therapies to children and families in need is central to our mission of ending the devastation caused by severe genetic diseases."
Disease Pathophysiology
MLD is caused by an error in the arylsulfatase-A (ARSA) gene that results in the accumulation of sulfatides in the brain and other areas of the body, including the liver, gallbladder, kidneys, and spleen. Over time, the nervous system is damaged, leading to neurological problems such as motor, behavioral and cognitive regression, severe spasticity, and seizures. Patients with MLD gradually lose the ability to move, talk, swallow, eat and see.
