PTC Therapeutics Submits Sepiapterin NDA to FDA

PTC Therapeutics, Inc., based in Warren, New Jersey, has announced the submission of a New Drug Application (NDA) for sepiapterin to the U.S. Food and Drug Administration (FDA). The NDA seeks approval for the treatment of both pediatric and adult patients with phenylketonuria (PKU), a rare inherited metabolic disorder.

Dr. Matthew B. Klein, CEO of PTC Therapeutics, expressed optimism about the submission, noting its significance for those living with PKU in the United States. He emphasized that the comprehensive clinical trial data, which includes results related to phenylalanine (Phe) tolerance, underscores sepiapterin’s potential to address the substantial unmet medical needs of many PKU patients.

The NDA is primarily supported by results from the phase 3 APHENITY trial, which revealed highly significant and clinically meaningful outcomes. On average, patients treated with sepiapterin experienced a 63% reduction in Phe levels, with an even greater reduction of 69% observed in those with classical PKU. Additionally, 84% of participants managed to maintain Phe levels below the treatment guideline of 360 µmol/L, and 22% of them achieved normalization of Phe levels.

Further evidence for sepiapterin's efficacy comes from the APHENITY open-label extension study, which highlights the drug’s durability, and a Phe tolerance sub-study. This sub-study found that about 60% of participants were able to achieve protein intake levels above the age-adjusted recommended daily allowance for unaffected individuals, while still keeping Phe levels under 360 µmol/L. These findings suggest that sepiapterin could allow patients to have a more liberal diet without losing Phe control, a change that could significantly improve quality of life and facilitate wider acceptance among healthcare providers and insurers.

In addition to the FDA submission, PTC Therapeutics is also pursuing regulatory approval in other regions. The European marketing authorization application is currently under review, and the company plans to submit applications in Japan and Brazil later in 2024.

Sepiapterin, also known as PTC923, is an oral synthetic compound that acts as a precursor to tetrahydrobiopterin, an essential cofactor in the metabolism and synthesis of various metabolic products. Sepiapterin is more bioavailable than synthetic BH4 administered externally and is expected to benefit a broad spectrum of PKU patients.

PKU is a rare genetic disorder that impairs the metabolism of phenylalanine, an amino acid found in many proteins and foods. Without proper management, phenylalanine can accumulate to toxic levels, causing severe and irreversible neurological damage, including intellectual disabilities, seizures, developmental delays, and behavioral issues. PKU is usually diagnosed through newborn screening programs, and there are approximately 58,000 people affected by the condition globally.

PTC Therapeutics is a biopharmaceutical company dedicated to discovering, developing, and commercializing innovative medicines for rare disorders. The company aims to address the needs of patients with limited treatment options by leveraging its scientific and clinical expertise. PTC’s strategic focus on developing a robust pipeline of transformative medicines supports its mission to provide access to best-in-class treatments for underserved patient populations.

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