Up to 5 years of weekly somatrogon in children with growth hormone deficiency: final data from the global phase 3 study

Abstract Purpose This open-label extension (OLE) study aimed to evaluate the long-term efficacy and safety of once-weekly somatrogon in pediatric patients with growth hormone deficiency (GHD) following up to 5 years of somatrogon treatment. Methods Patients who had previously completed 12 months of treatment (somatrogon or somatropin) in a phase 3, randomized, active-controlled study (NCT02968004) were eligible to enroll into this OLE study; somatropin-treated patients were switched to somatrogon (0.66 mg/kg/week), and somatrogon-treated patients received somatrogon at their previous dose. Results A total of 212 patients entered the OLE. Mean annualized height velocity at the end of OLE Year 1 (Y1), Y2, Y3, and Y4 was 8.11, 7.91, 7.02, and 6.56 cm/year, respectively. Mean height SDS increased in each year of the OLE and approached 0 SDS by OLE Y4. Mean (SD) IGF-I SDS was positive and within the normal range throughout the OLE. The incidence of adverse events (AEs) was 53.8% to 72.3%, with most being mild to moderate. The incidence of serious AEs in each year was low (0-4.7%), and none were related to treatment. The most common treatment-related AEs were injection-site pain and injection-site erythema. The presence of antidrug antibodies did not appear to impact safety or efficacy outcomes. Conclusion Based on the final data from the largest cohort of somatrogon-treated patients to date, once-weekly somatrogon demonstrated sustained efficacy and an acceptable safety profile during the OLE period. Once-weekly somatrogon constitutes a valuable long-term alternative to once-daily somatropin, offering potentially improved adherence and treatment outcomes.