OBJECTIVES: To avoid the waste of market shares, me-toos of established top selling biopharmaceuticals enter the market before their patent expiry. After switching the sales to the me-too, called “step-innovation” by the provider, the possible savings of biosimilars diminish as the sales are parked at the me-toos. The objective of the study is to analyse this hypothesis for the 2 substance classes Erythropoiesis- Stimulating Agents ESA und granulocyte colony-stimulating factors G-CSF. METHODS: By analysing the account data of regional Austrian sickness funds, the share of prescriptions of Filgrastim in GCSF (Filgrastim plus Lenograstim plus Pegfilgrastim) and of Epoetin in ESA (Epoetin plus Darbepoetin) are correlated to the costs per package. These data are shown for several periods, six month before the availability of Biosimilars, six month after their availability and two further half-years for ESA. To take regional influence into consideration the data are shown for all nine regional sickness funds of Austria. RESULTS: The shares of prescription for Epoetin in ESA show a huge regional dispersion from 42 % to 88 % and those of Filgrastim in GCSF from 23 % to 66 %. The average costs per package have an inverse relation to their market share. These data are reconfirmed through data of the other periods. The average costs per package have been declined with increased market share of the biosimilars. The influence of the market share of the me-toos is though overwhelming. CONCLUSIONS: For pharmaceutical companies it is a profit-maximising strategy to substitute their products in time before patent expiry. The less the substitution by patent-protected alternatives succeeds the higher the achievable cost saving potential for the sickness funds is.