PTC Therapeutics (NASDAQ: PTCT) outlined clinical progress for its phenylketonuria treatment Sephience at the 2026 Annual Symposium of the Society for the Study of Inborn Errors of Metabolism in Helsinki, Finland, scheduled for August 25-28.
The company presented 17 abstracts and scientific communications focused on Sephience, including data from the AMPLIPHY study. In a subset of participants with baseline phenylalanine levels at or above 900 µmol/L, the drug demonstrated a 100% greater reduction in blood phenylalanine levels compared to sapropterina at screening within 14 days. Clinically significant reductions were observed in this group within the two-week period.
Sephience, approved in the U.S., EU/European Economic Area, Japan, and other regions, acts as a natural precursor to the BH4 enzyme cofactor essential for phenylalanine metabolism. The treatment is indicated for pediatric patients aged one month and older, as well as adults, when combined with a phenylalanine-restricted diet. Real-world data presented at the symposium indicated that Sephience enabled diet liberalization in adolescents with BH4-responsive PKU mutations and classic BH4-non-responsive PKU while maintaining metabolic control within recommended targets.
Safety findings highlighted potential risks, including increased bleeding risk, hypophenylalaninemia in certain pediatric patients, and interactions with levodopa. The most common adverse reactions reported were diarrhea, headache, abdominal pain, hypophenylalaninemia, stool discoloration, and oropharyngeal pain.
Phenylketonuria, a rare inherited metabolic disorder, affects an estimated 58,000 people globally. Left untreated, it leads to phenylalanine accumulation and associated neurological complications. PTC’s stock (PTCT) was trading at $70.23, up 0.59%, at the time of the article’s data snapshot.
