Abstract One of the most spectacular advances in the history of scientific knowledge was the discovery of deoxyribonucleic acid (DNA) by Watson and Crick in 1953. This enabled certain proteins to be
prepared in this way for their therapeutic use in clinical practice. Today, in the first decade of the
21st century, hundreds of therapeutic proteins have been produced recombinantly and about 50 of them have been approved for clinical use. Because of the specific procedure used for obtaining these products, which is based on expressing a atherapeutica gene from a fragment of DNA in a cell to produce a functional protein that is free from any human or animal component, they ar especially acleana and thus the therapy of choice for many current diseases. The immediate question is: why are recombinant products not used more extensively given their high efficacy an maximum safety? In short, we are faced with an interesting but also unfortunate paradox o pharmacology that greater progress in therapeutic procedures is not always associated wit greater introduction of those resources that are safest, for the simple reason that they are mor costly.