FDA Grants Orphan Drug Status to SLS-005 for Treating Sanfilippo

The U.S. Food and Drug Administration (FDA) has granted orphan drug status to Seelos Therapeutics‘ SLS-005 (trehalose) to treat Sanfilippo syndrome, the company has announced.

Orphan drug designation aims to encourage the development of therapies for rare and serious diseases, through benefits such as seven years of market exclusivity and exemption from FDA application fees.

Seelos has also filed for Rare Pediatric Disease Designation for SLS-005 to the FDA and is awaiting its response. The designation is granted to product applications for diseases that affect fewer than 200,000 children, 18 or younger, in the U.S.

Sanfilippo syndrome is a rare genetic disorder characterized by the loss or dysfunction of enzymes that play a key function in the breakdown of a group of sugar molecules called glycosaminoglycans. The accumulation of these molecules is toxic to cells and tissues.

SLS-005 is a small sugar (trehalose) administered intravenously (directly into the blood). The therapy has the ability to reach the central nervous system (the brain and spinal cord), where it promotes autophagy: a cellular process to dispose of waste. SLS-005 enhances the cells’ ability to eliminate glycosaminoglycans.

Previous preclinical studies in a Sanfilippo type B mouse model showed that SLS-005 extended lifespan, eased inflammation in the brain and retina, and lessened nerve cell degeneration in these animals. Treated mice also showed less hyperactivity and anxiety-related behavior at early stages of the disease.

The FDA accepted Seelos’ investigational new drug application for SLS-005 in August 2019, which allowed the company to initiate a Phase 2b/3 trial to test SLS-005’s safety, tolerability, and efficacy in patients with Sanfilippo syndrome types A or B.

A collaboration between Team Sanfilippo Foundation (TSF) and Seelos additionally prompted a separate expanded access study to include patients with Sanfilippo types C and D, and patients with types A or B who do not meet the Phase 2b/3 trial eligibility criteria.

TSF is a nonprofit founded by parents of children with Sanfilippo syndrome and aims to fund potential therapies, while also helping families gain access to clinical trials, treatments, and compassionate use programs.

Seelos is also in contact with the European Medicines Agency (EMA) and is planning a European clinical study of SLS-005 in patients with Sanfilippo syndrome types A and B.

In two Phase 2 trials involving patients with oculopharyngeal muscular dystrophy (NCT02015481) and spinocerebellar ataxia type 3 (NCT02147886), trehalose was found to be safe and well-tolerated. Moreover, the data demonstrated the therapy’s efficacy in preventing the accumulation of toxic molecules by restoring the cells’ recycling system.

Both the FDA and EMA have granted orphan drug designation to trehalose for spinocerebellar ataxia type 3 and oculopharyngeal muscular dystrophy (OPMD). The treatment for OPMD has also received fast track designation in the U.S., a status intended to accelerate the therapy’s development and expedite its approval by providing more frequent meetings with the FDA and discussions about its development plan.

In February 2019, Seelos acquired the development and commercial rights to trehalose from BioBlast Pharma.