Is Somatrogon different? 6-month clinical outcomes and follow-up data in Turkish children transitioned from Somatropin to Somatrogon.

OBJECTIVE

Long-acting growth hormone (GH) formulations have been developed to reduce treatment burden and improve adherence in children with growth hormone deficiency (GHD). Somatrogon is a long-acting recombinant GH analog designed for once-weekly administration and has demonstrated comparable efficacy to daily somatropin in clinical trials. However, real-world data evaluating growth outcomes after transitioning from daily GH therapy to somatrogon remain limited. This study aimed to evaluate growth outcomes, biochemical responses, and predictors of treatment response during the first six months following the transition from daily somatropin to once-weekly somatrogon.

METHODS

This retrospective cohort study included 121 children with confirmed GHD who had received daily somatropin therapy (35 μg/kg/day) for at least one year before switching to once-weekly somatrogon (0.66 mg/kg/week). Auxological measurements and IGF-1 levels were evaluated at baseline and at 3 and 6 months after treatment transition. Height standard deviation score (SDS) and growth velocity were compared between treatment periods. Correlation analysis was used to evaluate the relationship between IGF-1 SDS and growth response. Multivariable linear regression analysis was performed to identify predictors of growth response.

RESULTS

The mean height gain during the final six months of somatropin therapy was 4.11 ± 2.01 cm, compared with 4.96 ± 1.56 cm during the first six months of somatrogon therapy. Height SDS increased significantly during the first three months following the transition to somatrogon compared with the final three months of somatropin therapy (0.17 ± 0.24 vs 0.08 ± 0.23; p = 0.02). However, the overall six-month change in height SDS did not differ significantly between treatment periods (p = 0.11). Mean IGF-1 SDS increased significantly from 0.12 ± 1.54 at baseline to 0.96 ± 1.96 at six months (p < 0.001). No statistically significant linear association was detected between IGF-1 SDS and height SDS improvement (r = 0.05, p = 0.62). Multivariable regression analysis identified baseline height SDS as the strongest predictor of growth response (β = -0.14, p = 0.003). Prepubertal patients showed greater height SDS improvement compared with pubertal patients (p = 0.04).

CONCLUSION

Switching from daily somatropin therapy to once-weekly somatrogon showed similar short-term growth patterns over a six-month follow-up period within the limitations of a within-patient observational design in children with GHD. Growth response appeared to be influenced primarily by baseline height status and pubertal stage rather than circulating IGF-1 levels alone did not show a detectable linear association with growth response in this cohort. These findings support the use of somatrogon as an effective and practical alternative to daily GH therapy in routine clinical practice. These findings suggest that growth outcomes were maintained following treatment transition; however, results should be interpreted cautiously given the observational design.