Have you ever heard of Orphan Drug designation before? The FDA grants Orphan Drug designation to drugs or biologics intended to treat, diagnose, or prevent rare diseases or conditions. In America, a rare disease is one affecting under 200,000 individuals. Drug developers whose products are granted Orphan Drug designation also receive a variety of benefits, including fee waivers, tax credits, increased regulatory assistance, and 7 years of market exclusivity upon approval. On March 15, 2022, gene therapy company SwanBio Therapeutics (“SwanBio”) shared that its therapeutic candidate SBT101, for adrenomyeloneuropathy (AMN), received Orphan Drug designation.
SBT101 is an adeno-associated virus (AAV)-based gene therapy designed to provide a working copy of ABCD1 in those with adrenomyeloneuropathy. Currently, ABCD1 mutations, inherited in an X-linked pattern, cause AMN. Normally, ABCD1 provides instructions for the adrenoleukodystrophy protein; this protein moves very long chain fatty acids into peroxisomes, where they are broken down. In those with AMN, there are not enough proteins, causing fatty acid accumulation and related symptoms.
About Adrenomyeloneuropathy (AMN)
As explained above, ABCD1 gene mutations cause adrenomyeloneuropathy (AMN), which falls under the umbrella of adrenoleukodystrophy (ALD). This X-linked adrenoleukodystrophy normally manifests when patients are in their 20s, and affects the spinal cord. Symptoms can include:
- Walking difficulties and gait changes
- Progressive muscle weakness and stiffness in the legs
- Nausea and unintended weight loss
- Sexual dysfunction (such as impotence)
- Adrenal insufficiency
- Hypertonia (abnormally high muscle tone)
- Difficulty articulating words
- Ataxia
- Hearing and vision loss
- Bladder control issues
- Seizures
