To the Editor; A Commentary on “Switching From Originator to Biosimilar Human Growth Hormone Using a Dialogue Teamwork: Single-Center Experience From Sweden”

The manuscript by Flodmark et al. [1] recently published in the open-access journal Biologics in Therapy describes a single-center experience in Sweden of a switch from an originator biologic to a biosimilar human growth hormone (rhGH) using a dialogue teamwork approach [1]. Unfortunately, the authors fail to mention several limitations to their study which call into question their conclusions. To evaluate the effect on growth of switching from originator to biosimilar rhGH, Flodmark et al. [2] applied a modeling approach previously developed based on limited Phase 3 clinical trial data. However, there are several questions regarding the suitability of this modeling approach and the methods used to compare the effect of originator and biosimilar rhGH on growth. First, it is unclear from either the current or the previously published manuscript whether the applied model has been suitably validated using an appropriate study population, with adequate sample sizes and suitable treatment duration. In this regard, the analysis described by the authors in their current report appears to be one of prediction model assessment, rather than treatment comparison. Second, given the heterogeneity in the diagnoses and pubertal status of the population treated with growth hormone, it is not clear whether the same prediction model would be appropriate for the different patient or diagnostic groups included in the current analysis (see, e.g., Ranke et al. [3]. Third, treatment history is not addressed by the applied model, an important issue given that prior treatment duration and history would be expected to affect growth performance. Fourth, the model employed by the authors [2] was derived from a small number of patients treated with originator rhGH for only 9 months, Mats Ekelund no longer works at Pfizer, but this was his affiliation at time of writing.