Iron sucrose: assessing the similarity between the originator drug and its intended copies

Iron sucrose (IS) is a complex nanocolloidal intravenous suspension used in the treatment of iron-deficiency anemia. Follow-on IS products (iron sucrose similars (ISSs)) have obtained marketing authorization by the generic pathway, implying that identical copies of IS may be manufactured. However, recent prospective and retrospective clinical studies showed discrepancies in clinical outcomes, which might be related to differences in physicochemical properties. The aim of this work is to measure and compare the physicochemical properties of IS and three ISSs available in the market using innovative analytical procedures. The comprehensive elucidation of size, size distribution, morphology, and stability of these complex drugs revealed very significant differences between the products. This study serves to provide the basis to define critical quality attributes that may be linked to differences in clinical outcome and thus may contribute to an adequate regulatory approach for IS and its follow-on products.