PTC Therapeutics Reveals New Sepiapterin Data From Phase 3 Study In Patients With Inherited Disorder, FDA Decision Expected In July

On Thursday, PTC Therapeutics, Inc. PTCT shared new data from the Phase 3 APHENITY trial and subsequent open-label extension study at the 2025 American College of Medical Genetics and Genomics (ACMG) Annual Clinical Genetics Meeting.

These data provide further evidence of the potential benefits of sepiapterin treatment for the full spectrum of phenylketonuria (PKU) patients.

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Phenylketonuria is an inherited disorder that increases the levels of a substance called phenylalanine in the blood.

Untreated phenylketonuria can lead to brain damage, intellectual disabilities, behavioral symptoms or seizures.

“These new data provide further evidence of the meaningful benefit sepiapterin can provide for children and adults with PKU, including those with the most severe form of the disease,” said Matthew Klein, CEO of PTC Therapeutics. “Furthermore, the treatment benefit demonstrated in individuals with mutations not responsive to BH4 and consistent with classical disease phenotype support the potential to penetrate all key patient segments.”

Treatment includes a strict diet with limited protein.

Key data presented include:

• Over 97% of subjects participating in the Phe tolerance protocol of the APHENITY open-label extension study demonstrate the ability to liberalize their diet while on sepiapterin treatment, with a mean increase in protein intake of 126%.
• 66% of subjects participating in the Phe tolerance sub study reached or exceeded the age-adjusted recommended daily allowance of protein intake for an individual without PKU, while maintaining control of blood Phe levels.
• Genetic variant analysis of subjects participating in the APHENITY study demonstrates that over 70% had a Genotype-Phenotype Value (GPV) consistent with classical PKU.

PTC submitted FDA regulatory approval applications in 2024 for sepiapterin for children and adults with PKU, with a target regulatory action date of July 29, 2025.

PTC also submitted several additional marketing authorization applications outside the U.S. for sepiapterin in 2024. The CHMP opinion on sepiapterin MAA is expected in the second quarter of 2025. A regulatory decision in Japan is expected in the fourth quarter of 2025.

Price Action: PTCT stock is down 0.18% at $56.88 on Thursday’s last check.

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