What patient demographics were predominantly studied with sapropterin?

Primary Demographics in Sapropterin Studies

Sapropterin (Kuvan), approved for phenylketonuria (PKU), was mainly studied in patients with PKU aged 4 years and older. Pivotal trials focused on children and adults with moderate to severe hyperphenylalaninemia (Phe levels 10-30 mg/dL), excluding those with classic PKU (Phe >30 mg/dL unresponsive to treatment). Over 70% of participants were pediatric (4-18 years), with smaller adult cohorts.[1][2]

Age Breakdown Across Key Trials

• PKU-004 trial: 89 patients aged 8-48 years; median age 20 years; 57% male.[1]
  
• PKU-005 trial: 245 patients aged 4-50 years; mean age 15 years; included 8-12 year-olds (n=90) and adolescents/adults (n=155).[2]
  
• PKU-006 extension: Long-term data on 261 patients aged 4+; mostly followed from pediatric trials into adulthood.[3]
  Younger children under 4 were not included due to higher risks of Phe fluctuations.
  
  

Gender and Severity Focus

Studies showed balanced gender distribution (roughly 50-60% male), but emphasized tetrahydrobiopterin (BH4)-responsive PKU variants. Milder forms (Phe 10-20 mg/dL) responded best, with 20-30% Phe reduction in responders.[1][2] No significant racial/ethnic breakdowns reported, though U.S./European cohorts predominated.

What About Infants or Non-Responders?

Infants under 4 months (tetrahydrobiopterin deficiency trials, n=13) were studied separately but not for standard PKU approval. Non-responders (no Phe drop after 8-week challenge) were excluded from efficacy analyses.[3] Real-world data later expanded to broader ages, but trials targeted treatment-naive or diet-managed PKU patients.

[1] FDA Label for Kuvan (sapropterin dihydrochloride)
[2] NEJM: Phase 3 Trial of Sapropterin in PKU (2007)
[3] BioMarin Clinical Data Summary