1. PTC923 (sepiapterin) lowers elevated blood phenylalanine in subjects with phenylketonuria: a phase 2 randomized, multi-center, three-period crossover, open-label, active controlled, all-comers study.
- Author
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Bratkovic D, Margvelashvili L, Tchan MC, Nisbet J, and Smith N
- Subjects
- Adolescent, Adult, Biopterins analogs & derivatives, Biopterins cerebrospinal fluid, Cross-Over Studies, Female, Humans, Male, Phenylalanine administration & dosage, Phenylketonurias blood, Pterins adverse effects, Young Adult, Phenylalanine blood, Phenylketonurias drug therapy, Pterins therapeutic use
- Abstract
Background & Aim: PTC923 (formerly CNSA-001), an oral formulation of sepiapterin, a natural precursor of intracellular tetrahydrobiopterin (BH
4 ), has been shown in humans to induce larger increases in circulating BH4 vs. sapropterin dihydrochloride. Sapropterin reduces blood phenylalanine (Phe) by ≥20-30% in a minority of subjects with PKU. This was a Phase 2 randomized, multicenter, three-period crossover, open-label, active controlled, all-comers [regardless of phenylalanine hydroxylase (PAH) variants] comparison of PTC923 60 mg/kg, PTC923 20 mg/kg and sapropterin 20 mg/kg in 24 adults with phenylketonuria (PKU) and hyperphenylalaninemia., Methods: Eligible subjects were adult men or women (18-60 y) with PKU. Subjects enrolled received 7 days of once-daily oral treatment with PTC923 20 mg/kg/day, PTC923 60 mg/kg/day and sapropterin dihydrochloride 20 mg/kg/day each in a random order. Treatments were separated by a 7-day washout. Subjects maintained their usual pre-study diet, including consumption of amino acid mixtures. Blood Phe was measured on Day 1 (predose baseline), Day 3, Day 5, and Day 7 of each treatment period., Results: Least squares mean changes (SE) from baseline in blood Phe were: -206.4 (41.8) μmol/L for PTC923 60 mg/kg (p < 0.0001); -146.9 (41.8) μmol/L for PTC923 20 mg/kg (p = 0.0010); and - 91.5 (41.7) μmol/L for sapropterin (p = 0.0339). Effects of PTC923 60 mg/kg on blood Phe vs. sapropterin were significantly larger (p = 0.0098) and faster in onset with a significantly larger mean reduction in blood Phe at day 3 of treatment, p = 0.0135 (20 mg/kg) and p = 0.0007 (60 mg/kg). Only PTC923 60 mg/kg reduced blood Phe in classical PKU subjects (n = 11, p = 0.0287). The mean blood Phe reduction (PTC923 60 mg/kg) in a cofactor responder analysis (n = 8; baseline Phe ≥300 μmol/L and blood Phe reduction ≥30%) was -463.3 μmol/L (SE 51.5) from baseline. Adverse events were mostly mild to moderate, transient, and similar across treatment groups with no serious adverse events or discontinuations., Conclusions: The substantially significantly better effect of PTC923 60 mg/kg on blood Phe reduction vs. sapropterin supports further clinical development of PTC923 for PKU; ANZCTR number, ACTRN12618001031257., Competing Interests: Declaration of competing interest Neil Smith is an employee and stockholder of PTC Therapeutics Inc., the pharmaceutical sponsor of the investigational treatment evaluated in this study. Drago Bratkovic, Lali Margvelashvili, Michel Tchan, and Janelle Nisbet were clinical investigators for the study and declare that they have no conflicts of interest. Medical writing assistance was provided by Dr. Mike Gwilt, GT Communications, funded by PTC Therapeutics Inc., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2022
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