Substitution of therapy implies the medical practice in which a physician decides to replace a product that is currently used in a patient’s treatment with another product. The practice in which a physician decides to switch between different biological molecules is not new. Usually, substitution is motivated by a clinical decision to find the appropriate therapy for the patient due to inadequate efficacy and / or tolerance to the previous product.
Biological medicines, including biosimilar medicines, are medical products, commonly obtained from proteins produced by the use of living organisms. Biological medicines are generally larger and more complex than small molecule medicines, for which the clinical response depends on several factors, associated to the patient, the disease and the product, and for which the best judgment is given by the physician.