Assessment of Biosimilar Somatropin Use in Italian Routine Care: A 6-Year, Multicenter, Retrospective Study Using a Database Network

Somatropin (recombinant growth hor- mone, rGH) is a biological product approved for growth disturbances due to GH deficiency/Turner or Prader-Willi syndrome/chronic kidney disease or in children born small for gestational age. From 2006, biosimilar rGH is available in Italy, but population- based data about its prescribing pattern in Italian rou- tine care are lacking. Objectives: To explore the prescribing pattern of biosimilar/originator rGH in five Italian geographic areas, where various healthcare policies promoting biosimilar use were taken. Methods: This drug utilization study was conducted using administrative databases of Tuscany and Umbria Region and Caserta, Treviso and Palermo Local Health Units in the years 2009-2014 (“Assessment of short and long term risk-benefit profile of biologics through healthcare database network in Italy” project, funded by the Italian Ministry of Health). Characterization of naïve rGH users and prevalence of biosimilar and orig- inator use over time and across centers were assessed. Results: In the study years, 4,103 (0.1% of the total residents in the catchment areas) patients used rGH. Of these, naïve users were 2,707 (66.0%), most ofwhom were 6-11 years old (N = 1,075, 39.7%). The main indication for use was growth disturbance due to GH deficiency (N = 942, 34.8%). The overall preva- lence of rGH use was rather stable across years (0.2- 0.3 per 1,000 inhabitants). The proportion of biosimilar users increased from 5.7% (2009) to 11.1% (2014), but heterogeneity across different areas was reported, with greater increase in Tuscany (from 5.2% to 16.9%) and lower in Umbria (from 5.6 to 7.5%). Conclusions: In comparison to other biosimilars (e.g. filgrastim and epoetin alpha), the proportion of biosimilar rGH users was low in recent years, despite a slight increase. Notably, relevant heterogeneity in the biosimilar rGH use across centers was docu- mented. Differences may be due to different policies across centers, which may be specific per type of biosimilar drug. Since somatropin accounts for most of the pharmaceutical expenditure in hormonal prepa- rations in Italy, these data warrant more research.