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Background: Recombinant human growth hormone (rhGH, somatropin) therapy is approved in children with Prader–Willi syndrome (PWS).

Objectives: To report safety and effectiveness data for children with PWS treated with biosimilar rhGH (Omnitrope®, Sandoz) in the PAtients TReated with Omnitrope (PATRO) Children study.

Design: PATRO Children was a multicenter, non-interventional, postmarketing surveillance study.

Methods: Children with PWS received Omnitrope according to standard clinical practice. Adverse events (AEs) were monitored for the duration of Omnitrope treatment. Effectiveness outcomes were also assessed, including height standard deviation (SD) scores (HSDS).

Results: As of July 2020 (study completion), 235 patients with PWS had been enrolled. At baseline, 95.7% (n = 225) of patients were prepubertal and 86.4% (n = 203) were rhGH treatment-naïve. At analysis, the median (range) treatment duration in the study was 56.8 (2.9–155.8) months. AEs were reported in 192 patients (81.7%) and were suspected as treatment-related in 39 patients (16.6%). Serious AEs (SAEs) were reported in 96 patients (40.9%) and were suspected as treatment-related in 22 patients (9.4%). The most frequent treatment-related SAEs were sleep apnea syndrome (n = 11; 4.7%), tonsillar hypertrophy (n = 4; 1.7%), and adenoidal hypertrophy (n = 4; 1.7%). Development of scoliosis was considered treatment-related in two patients; development of impaired glucose tolerance in one patient and type 2 diabetes mellitus in another patient were considered treatment-related. Effectiveness outcomes were primarily assessed in 153 patients who completed 3 years of treatment. Among the 151 prepubertal patients (135 treatment-naïve), mean (SD) change from baseline in HSDS after 3 years was +1.50 (1.07) across all patients and +1.57 (1.07) for treatment-naïve patients.

Conclusion: These data suggest that biosimilar rhGH is well tolerated and effective in patients with PWS managed in real-life clinical practice. Patients with PWS should continue to be closely monitored for well-known safety issues (including respiratory, sleep, and glucose metabolism disorders, and scoliosis) during rhGH treatment.