Extrapolation refers to the approval of a biosimilar medicine for the treatment of diseases or conditions for which it has not been specifically studied. This approval is based on the high degree of similarity between the biosimilar and the reference biological medicine. For this reason, once efficacy and safety, measured on the basis of clinical criteria and using the most sensitive population possible, have been shown for one indication, the use of the biosimilar could be extrapolated to the rest of the indications for which the brand-name medicine is authorised.