FDA Grants Fast Track Designation to Muscular Dystrophy Drug

Resolaris treats limb girdle muscular dystrophy 2B.

Manufacturer aTyr Pharma recently announced that Resolaris received fast track designation from the FDA to treat patients with limb girdle muscular dystrophy 2B (LGMD2B).

Limb girdle muscular dystrophy is a group of rare genetic diseases with more than 20 subtypes, none of which have approved drug therapies. These diseases affect approximately 16,000 patients.

Specifically, LGMD2B is caused by a toxic loss of function in the dysferlin gene, and affects approximately 3000 patients, according to a press release from aTyr. The disease is characterized by progressive muscle weakness, atrophy, and immune cell invasion into skeletal muscle.

Resolaris is the first investigational LGMD2B drug to receive fast track designation, aTyr reported. The drug is derived from natural proteins released by skeletal muscle cells, and is administered intravenously.

The FDA has also chosen to remove its partial clinical hold on dosing in clinical trials of Resolaris.

"This Fast Track designation, which is granted to drug candidates addressing serious conditions and that demonstrate the potential to address unmet medical needs, represents another step forward for our first product candidate based on the Physiocrine pathway," said John Mendlein, PhD, CEO of aTyr Pharma. "Combined with our Phase1b/2 data in LGMD2B, adult facioscapulohumeral muscular dystrophy (FSHD) and early onset FSHD patients, we believe we are building a clinical and regulatory foundation for future development of Resolaris to treat patients across multiple rare genetic myopathies with an immune component."

Positive results from a phase 1b/2 dose escalation clinical trial were announced. In the study, 9 patients with LGMD2B received biweekly doses of Resolaris up to 3-mg/kg. By week 14, 78% of patients had improvements in muscle function, which was measured by a manual muscle test.

Patients experienced an average of 6.2% improvement from baseline, according to the press release. The manufacturer reported that Resolaris had consistently demonstrated a favorable safety profile without immunosuppression in all clinical trials.

If approved, Resolaris would offer a first-in-class intravenous treatment for patients with LGMD2B, who currently do not have any treatment options.

"We appreciate the FDA's responsiveness to our request to remove the partial clinical hold that provides dosing flexibility based on our data for Resolaris," said Sanjay Shukla, MD, MS, chief medical officer of aTyr Pharma. "We also believe that during our safety and dose ranging Phase 1b/2 clinical trials we have potentially identified a dose for the next phase of clinical development with a favorable safety profile and potential clinical activity across different rare muscle indications."