The US Food and Drug Administration (FDA) has granted rare paediatric disease designation to ArmaGen Inc's AGT-181, a potential treatment for patients with Hurler syndrome, a disease that is also known as mucopolysaccharidosis type I (MPS I).

AGT-181 is a novel, investigational enzyme replacement therapy (ERT) for the treatment of neurological complications in patients with Hurler syndrome. Using ArmaGen’s proprietary technology, AGT-181 takes advantage of the body’s natural system for transporting products across the blood-brain barrier (BBB) by targeting the same receptor that delivers insulin to the brain. ArmaGen developed AGT-181 by re-engineering IDUA as an immunoglobulin G (IgG) fusion protein. The fusion protein binds to insulin receptors located on the surface of the BBB, enabling its passage into the brain.

The FDA previously granted AGT-181 Orphan Drug status, based on the prevalence of Hurler syndrome, which affects approximately 3,000 patients worldwide. The designation of rare pediatric disease status will make ArmaGen eligible to request a Rare Paediatric Disease Priority Review Voucher (Rare Paediatric DPRV) upon approval of AGT-181 by the FDA.

Commercially available treatments for Hurler syndrome do not penetrate the blood-brain barrier (BBB), and therefore do not address the severe and progressive neurological complications of the disease. AGT-181 is designed to utilize the body’s natural system for transporting products non-invasively across the BBB and into the central nervous system by targeting the receptor that delivers insulin to all cells of the body.

“Receipt of rare pediatric disease designation strengthens ArmaGen’s commitment to providing children, families and physicians with treatment options for the currently unaddressed complications of Hurler syndrome,” said James Callaway, Ph.D., chief executive officer of ArmaGen.

“As we advance this therapeutic option towards approval, ArmaGen will be positioned to utilize the Rare Pediatric DPRV to expedite review of future investigational products, or leverage its sale to reinvest in other programs in our pipeline.”

The FDA defines a “rare paediatric disease” as a disease that affects fewer than 200,000 individuals in the US primarily aged from birth to 18 years. Under the FDA’s Rare Paediatric DPRV programme, a sponsor who receives an approval of a new drug application (NDA) or biologics license application (BLA) for a rare pediatric disease may be eligible for a voucher, which can be redeemed to obtain expedited FDA review for any subsequent marketing application. The DPRV may be sold or transferred by the recipient.

Hurler syndrome is a rare, hereditary, lysosomal storage disease that arises from a deficiency or absence of the enzyme iduronidase (IDUA), which is needed to break down complex sugars produced by the body. Hurler syndrome affects the brain and spinal cord in children, resulting in debilitating signs and symptoms that include developmental delay, progressive mental decline, loss of physical function, impaired language development (due to hearing loss and an enlarged tongue), corneal and retinal damage, carpal tunnel syndrome, and restricted joint movement.

Hurler syndrome is also known as mucopolysaccharidosis I, or MPS I. Attenuated or less severe forms of MPS I include Hurler-Scheie and Scheie syndromes. Patients with Hurler-Scheie syndrome may suffer from mild cognitive impairment or problems with attention. Patients with Scheie syndrome generally have a later onset and milder symptoms with a slower disease progression, although they can develop significant systemic morbidity.