PTC Therapeutics, Inc announced that the United States Food and Drug Administration (FDA) has granted priority review for the New Drug Application (NDA) for risdiplam (RG7916) for the treatment of spinal muscular atrophy (SMA). The Prescription Drug User Fee Act (PDUFA) goal date for a decision by the FDA is May 24, 2020. The filing acceptance by the FDA triggers a US$15M milestone payable to PTC by Roche. "The FDA's acceptance of the NDA is an important step towards making risdiplam available to SMA patients in the US," said Stuart W. Peltz, Ph.D, chief executive officer of PTC Therapeutics. "We are proud that risdiplam, the first oral small molecule targeting splicing, was produced from our proprietary splicing platform. Risdiplam's NDA submission includes results from a broad SMA patient population, including type 1, type 2 and type 3 SMA patients demonstrating improvements in motor functions and developmental milestones, and a compelling safety profile. We believe that an oral therapeutic that reaches all affected tissues in the body would mark a significant advancement in the treatment for SMA patients and their families." The FDA has granted risdiplam priority review status, which is designated to drugs that, if approved, would represent significant improvements in the safety or effectiveness of the treatment, diagnosis, or prevention of serious conditions when compared to standard applications. The NDA filing is based on 12-month data from the dose-finding portion of the pivotal FIREFISH and SUNFISH studies, and clinical and preclinical pharmacokinetic and pharmacodynamic data. FIREFISH is an open-label, two-part clinical trial of risdiplam in infants with SMA type 1. SUNFISH is a double-blind, two-part, placebo-controlled trial of risdiplam in patients with type 2 or 3 SMA aged 2-25 years. SUNFISH part 2 recently met its primary endpoint of change from baseline in the Motor Function Measure 32 scale. Results from the study will be presented at an upcoming medical congress. The SMA program is a collaboration between PTC, the SMA Foundation and Roche. Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder that is the leading genetic cause of mortality in infants and toddlers caused by deletion or mutation in the survival of motor neuron 1 (SMN1) gene, which results in reduced levels of SMN protein. The related SMN2 pre-mRNA is alternatively spliced producing only small amounts of functional SMN protein. Insufficient levels of SMN protein result in the progressive loss of motor neurons leading to muscle atrophy and death in its most severe form. It is estimated that 1 in every 11,000 newborn children will develop SMA. Risdiplam is an investigational medicine being studied in a broad range of patients with SMA from birth to 60 years of age. It is designed to provide sustained increase in SMN protein centrally and peripherally through daily dosing and is being evaluated for its potential ability to help the SMN2 gene produce more functional SMN protein throughout the body. Risdiplam is being studied in a clinical trial for patients with type 1 SMA, called FIREFISH, in pre-symptomatic babies, RAINBOWFISH, in patients who have been in previous clinical trials for SMA, JEWELFISH and in SUNFISH, a placebo-controlled study in people aged 2-25 years with type 2 or 3 SMA.