OBJECTIVEA previous 12-month comparative trial with Criscy™ (r-hGH Cristália), a biosimilar recombinant growth hormone, demonstrated equivalent efficacy and safety to Genotropin™. This extension trial evaluated the effects of switching patients treated with Genotropin™ to the biosimilar Criscy™ over an additional 6-month treatment period, comparing efficacy, safety, and immunogenicity parameters with patients remaining in the Criscy™ arm.DESIGNThis extension study included 11 research centers and 81 patients who participated in the CERES study (Czepielewski et al., 2019 [1]). Participants from the Genotropin™ arm (n = 39) had the drug replaced by Criscy™ and the remaining participants were kept in the Criscy™ arm (n = 42) for an additional 6-month period to evaluate immunogenicity, efficacy (growth rate, height SDS), and safety (laboratory tests, and adverse events).RESULTSBefore the switch, both Criscy™ and Genotropin groups were similar concerning demographics, and auxological measures: age, sex, height, height SDS, weight, and BMI. Height velocity (HV) after 18 months of treatment was 8.7 ± 1.56 cm/year for Criscy™ group and 8.9 ± 1.36 cm/year for Genotropin™ group in the ITT population (p = 0.43). The auxological parameters and IGF-1 and IGFBP-3 SDS were comparable between both groups of patients. No participants were excluded from the study due to adverse events. There were no clinical or statistical relevant differences between the treatment groups concerning frequency, distribution, intensity, and AEs outcome. Similarly, no new anti-r-hGH (ADA) cases among patients that switched from Genotropin™ to Criscy™ were reported. No neutralizing antibody (nAb) was detected in either group.CONCLUSIONSThis trial showed that switching from originator recombinant human growth hormone to Criscy™ had no impact on efficacy, safety, nor immunogenicity as compared to continued treatment with Criscy™. Growth rates and ADA incidence remained the same as seen before the switch.