FDA Grants Orphan Drug Designation to SLS-005 for Slowing ALS Progression

The U.S. Food and Drug Administration (FDA) has awarded orphan drug designation to Seelos Therapeutics‘ SLS-005 (trehalose), a medication designed to slow the progression of amyotrophic lateral sclerosis (ALS), the company announced in a recent press release.

The designation confers several benefits, meant to encourage drugmakers to further develop therapies for rare and serious diseases. These include exemption from certain FDA application fees, trial protocol assistance, and seven years of market exclusivity upon approval.

The active ingredient in SLS-005, trehalose, is a naturally occurring sugar molecule found in various bacteria, plants, fungi, and invertebrates — but not in human cells.

Trehalose has been shown, in past studies, to have the ability to access neurons by crossing the brain’s semi-permeable protective layer known as the blood-brain barrier. While this barrier protects the brain from infections, it also poses a significant obstacle for many therapies, preventing them from entering the central nervous system (CNS), composed of the brain and spinal cord.

In ALS, motor neurons in the CNS progressively become damaged and die, often from being unable to clear away clumps of proteins that grow to toxic levels.

Trehalose appears to function by stabilizing proteins and activating a cellular process called autophagy, which removes and recycles old and damaged cellular components, including the toxic protein clumps. In preclinical studies, SLS-005 increased the removal or decreased the formation of several protein clumps relevant to ALS. These proteins include TDP-43, SOD1, and SQSM1/p62.

Stopping or reversing the buildup of those proteins delays the progression of ALS, keeps motor neurons healthy longer, and increases the size of muscle fibers.

The FDA earlier this year cleared Seelos to conduct a Phase 2b/3 clinical trial investigating SLS-005 for the treatment of ALS. The trial plans to enroll approximately 160 patients with either familial or sporadic ALS to evaluate the medication’s ability to slow disease progression.

Participants will be randomly assigned to receive either SLS-005 or a placebo for 24 weeks (about six months). For each patient receiving a placebo in the trial, three will be given SLS-005.

The trial’s primary goal is to determine whether SLS-005 is better than the placebo at slowing disease progression, as measured by changes in the ALS Functional Rating Scale (ALSFRS-R) over the six months of treatment. The ALSFRS-R assesses patients for speech, swallowing, handwriting, walking, climbing stairs, and breathing, among other measures.

Secondary trial endpoints will include changes in slow vital capacity — a measure of lung function — muscle strength, quality of life, and any additional signs of disease progression.

SLS-005 has also received orphan drug status for several other rare diseases. Both the FDA and the European Medicines Agency (EMA) granted such status for the treatment of Sanfilippo syndrome, spinocerebellar ataxia type 3, and oculopharyngeal muscular dystrophy.