ESPE Abstracts

Background: Treatment adherence to daily subcutaneous rhGH is a burden for GHD patients, with noncompliance reported in up to 77% of patients and significantly associated with reduced efficacy (Rosenfeld Endocr Pract 2008; Cutfield PLoS One 2011). Somavaratan, a novel rhGH fusion protein with t_1/2 >100 h, demonstrated clinically meaningful improvements in height velocity and IGF-I in prepubertal children with GH deficiency (GHD) in a multicenter, randomized, Phase 1b/2a study (Moore JCEM 2016).

Objective and hypotheses: To evaluate treatment adherence to at-home dosing of twice-monthly dosing schedule of somavaratan in an ongoing, long-term extension study.

Method: 64 subjects were initially randomized to weekly, twice-monthly, and monthly dosing groups for total dose of 5.0 mg/kg per month for 6 months. Sixty subjects enrolled in an extension study; all transitioned to somavaratan 3.5 mg/kg twice-monthly by the start of the 2nd treatment year, based on growth and IGF-I responses observed in the first 6-12 months of treatment. During the extension study, injections were administered at home by caregivers. Treatment adherence was reported by caregivers using an electronic patient-reported outcome diary (eDiary; Bracket, Inc.).

Results: Mean age at baseline was 7.5±2.3, 8.0±2.4 and 8.0±2.5 for the weekly, twice-monthly, and monthly dosing groups; mean age for subjects enrolled in the extension study was 8.3±2.4 (Day 1). With at-home dosing facilitated with an eDiary system during the initial 18 months and over 1600 doses administered, dosing adherence was 99.6% and injection adherence was 99.4%. Data on dosing and injection adherence during Year 2 will be presented.

Conclusion: With nearly 100% dosing adherence using the eDiary and the Phase 3 dosing schedule for somavaratan, we present evidence that long-acting rhGH has the potential to improve long-term adherence in children with GHD. A Phase 3 study of 3.5 mg/kg twice-monthly somavaratan using the eDiary to monitor treatment adherence is ongoing (NCT02339090).