Francjan van Spronsen, Heidi Peters, Lali Margvelashvili, Dodo Agladze, Ida Vanessa D. Schwartz, Maria Giżewska, Takashi Hamazaki, Laura Guilder, Anita MacDonald, Suresh Vijay, Anita Inwood, Maria Avanise Yumi Minami, Olivia Fjellbirkeland, Allan Lund, Melissa Lah, Janet A. Thomas, Nicola Longo, Ertuğrul Kiykim, Mika Ishige, Alberto Burlina, Amaya Bélanger-Quintana, Frank Rutsch, Thomas Opladen, Neslihan Önenli Mungan, Fatih Ezgü, Drago Bratkovic, Anupam Chakrapani, Tetsuya Ito, Arlindo Guimas, Roberto Zori, Michel Tchan, Stephanie Sacharow, Anabela Oliveira, Patrícia Janeiro, Ixiu-Cabrales Guerra, Jaume Campistol Plana, Yılmaz Yıldız, Ebru Canda, Aneal Khan, Jerry Vockley, Margo Sheck Breilyn, Filippo Manti, Alex Larkin, Catalina Hughes, Enwu Liu, Lan Gao, Kimberly Ingalls, Neil Smith, Ania C. Muntau
To report interim results from the ongoing, open-label, phase 3 APHENITY Extension Study (NCT05166161), evaluating long-term treatment with sepiapterin in patients with phenylketonuria.
PURPOSE: To report interim results from the ongoing, open-label, phase 3 APHENITY Extension Study (NCT05166161), evaluating long-term treatment with sepiapterin in patients with phenylketonuria. METHODS: Participants received an age-based dose of oral sepiapterin daily; those with mean blood phenylalanine (Phe) levels <360 μmol/L (<5.95 mg/dL) after 2 weeks underwent a 26-week dietary Phe tolerance assessment, wherein dietary Phe intake was adjusted and blood Phe levels monitored. Other participants continued treatment with optional diet liberalization. Primary endpoints included change from baseline to week 26 in dietary Phe intake and treatment-emergent adverse events (TEAEs). RESULTS: As of September 2, 2024, 169 participants received sepiapterin (median [minimum, maximum] age: 14.0 [0.2, 55.0] years, median exposure: 72.9 weeks); 102 participants underwent dietary Phe tolerance assessments. Mean (SD) dietary Phe intake increased from 27.6 (18.0) mg/kg/day at baseline to 62.5 (41.5) mg/kg/day at week 26 (least-squares mean change [SE]: 36.4 [2.8] mg/kg/day from baseline) (P < .0001 from post hoc analysis). The incidence of treatment-related TEAEs was 29.0%; 3 participants (1.8%) discontinued treatment owing to treatment-related TEAEs. There were no treatment-related serious TEAEs or deaths. CONCLUSION: Interim results support the long-term safety of sepiapterin and demonstrate the potential for diet liberalization in adults and children with phenylketonuria. GOV IDENTIFIER: NCT05166161 (https://www. CLINICALTRIALS: gov/study/NCT05166161; date of registration, December 8, 2021).