A Randomized Study of Safety and Efficacy of Two Doses of Ambrisentan to Treat Pulmonary Arterial Hypertension in Pediatric Patients Aged 8 Years up to 18 Years

OBJECTIVE: To assess the safety and efficacy of the endothelin receptor antagonist ambrisentan in pediatric pulmonary arterial hypertension (PAH). STUDY DESIGN: In this open-label, phase IIb study, patients with PAH aged 8 to <18 years were randomized to low- or high-dose ambrisentan for 24 weeks. Most patients were receiving other PAH medication(s) that could not be changed during the trial. The primary outcome was safety (treatment-emergent adverse events [TEAEs]); secondary outcome was efficacy (including change from baseline to week 24 in 6-minute walking distance and World Health Organization functional class). Study staff were blinded to treatment. No statistical testing was performed. RESULTS: Most of the 41 patients randomized (80%) experienced ≥1 TEAE; most were mild (22%) or moderate (49%) in severity (no difference between dose groups). Most common TEAEs were headache (24%), nausea (17%), abdominal pain (12%), and nasopharyngitis (12%). Eight patients had serious TEAEs; 2 were fatal (unrelated to study treatment). Improved 6-minute walking distance was observed from baseline to week 24: total mean (SD) change, +40.69 (84.58) meters; World Health Organization functional class was maintained or improved in 70% and 27% patients, respectively. CONCLUSIONS: Ambrisentan was well tolerated; TEAEs were consistent with the adult safety profile. Efficacy was similar to previous findings in adult PAH; however, interpretation is limited by small sample size. Findings support a potentially similar benefit:risk profile in pediatric (8 to <18 years) and adult patients with PAH. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01332331