Sapropterin For Phenylketonuria: A Japanese Post-Marketing Surveillance Study.

BACKGROUND: To assess the long-term safety and efficacy of sapropterin in a real-world setting in Japanese patients with tetrahydrobiopterin (BH4)-responsive phenylketonuria (PKU).

METHODS: This post-marketing surveillance study enrolled all patients in Japan with confirmed BH4-responsive PKU who were administrated sapropterin between July 2008 and October 2017. Patients were observed at least every 3 months during follow-up, with key data collected on treatment exposure/duration, effectiveness according to physician judgement, serum phenylalanine levels, and adverse events.

RESULTS: Of 87 enrolled patients, 85 patients (male, 42.4%; outpatients, 96.5%) were included in the safety and efficacy analysis sets. Treatment started at age <4 years in 43 (50.6%) patients and the most common starting daily dose was 5-10 mg/kg (n=41 [48.2%]) with the overall duration of treatment between 0.2 and 17.2 years. Serum phenylalanine levels according to loading tests reduced from a baseline level of 9.66 mg/dL (range 0.48-36.80 mg/dL) by >30% in 84 patients. Treatment was deemed effective in 79 of 85 patients (92.9%, 95% CI 85.3-97.4). One (1.2%) patient experienced an adverse drug reaction (alanine aminotransferase increased) 50 days after the start of administration, which resolved without complications with continued treatment.

CONCLUSIONS: Sapropterin appears well tolerated and highly effective in Japanese patients treated in a real-world setting, including those who start treatment at age <4 years and pregnant women.