Main Patient Groups in Sapropterin Trials
Sapropterin (Kuvan), approved for phenylketonuria (PKU), was tested primarily in patients with hyperphenylalaninemia due to tetrahydrobiopterin (BH4)-responsive PKU. Pivotal trials focused on individuals aged 4 years and older with blood phenylalanine (Phe) levels between 10 and 30 mg/dL who showed at least 30% Phe reduction after a BH4 challenge.[1][2]
Key phase 3 trials (PKU-004 and PKU-006) enrolled:
- Children (4-12 years): 89 patients in PKU-004, assessing Phe control over 6 weeks and 10 years long-term.
- Adolescents and adults (13+ years): 245 patients in PKU-006, evaluating 6-week efficacy and long-term safety.[2]
Earlier studies like PKU-001 and PKU-002 included smaller groups of children and adults responsive to BH4 loading tests.[1]
Trials in Infants and Toddlers
A dedicated phase 3 trial (PKU-015) targeted BH4-responsive infants aged 1-3 years with Phe 10-30 mg/dL. It enrolled 19 patients, showing sustained Phe reduction over 4 weeks, with extensions up to 6 years. This group had milder hyperphenylalaninemia at baseline.[2][3]
Patients with Severe or Classical PKU
Most trials excluded severe classical PKU (Phe >30 mg/dL unresponsive to BH4). Responsive patients typically had milder mutations allowing partial BH4 cofactor activity. Subgroup analyses showed better response in those with specific PAH genotypes.[1][4]
Exclusion Criteria Across Trials
Common exclusions: Phe <10 mg/dL or >30 mg/dL, non-BH4 responsive, pregnancy, severe organ issues, or concurrent drugs affecting Phe. Trials required confirmed PKU diagnosis via newborn screening or genotyping.[2]
Long-Term Data on Patient Demographics
Open-label extensions tracked over 1,000 patients (ages 0-50+), with 60% children/adolescents at entry. Demographics skewed female (55-60%) and white (90%+), reflecting PKU prevalence.[2][5]
[1]: FDA Label for Kuvan
[2]: BioMarin Clinical Trial Summaries (PKU Studies)
[3]: Trefz et al., Mol Genet Metab 2011;102:18-23
[4]: Burton et al., Mol Genet Metab 2007;92:63-70
[5]: Long-term registry data, Levy et al., Pediatrics 2013;132:e268-e274