Circumventing immunization by in vitro directed evolution and selection of human antibodies from large surface display libraries Ao.Univ.Prof. DI Dr.nat.techn Florian Rüker (Head of Institute of Molecular Biotechnology, BOKU) Monoclonal antibodies are currently the most important class of biological therapeutics. They are used for the treatment of a wide range of diseases, including cancer and autoimmune disorders. In the year 2018, 10 monoclonal antibodies were among the 15 largest selling drugs worldwide. Adalimumab (Humira) has been the top selling drug for many years now and is a prime example for an antibody that was generated entirely by in vitro methods, completely circumventing immunization. This seminar will focus on methods how this can be accomplished. Bacteriophage, yeasts or mammalian cells, and even ribosomes allow the formation of so-called genetic packages, where a recombinant protein like e.g. an antibody or an antibody fragment is expressed on its surface, and the encoding genetic information is contained in the inside of the package. This direct link between genotype and phenotype allows the creation of large and diverse libraries of antibody fragments, in which all clones differ within the region that contacts antigen. Typical sizes of antibody fragment libraries are in the range of 109 to 1011 independent clones. Libraries can be enriched and selected for clones that bind to an antigen of interest, thus mimicking immune selection. Selected clones can be isolated and further engineered, resulting in human antibodies of high affinity and specificity, which can then be expressed and purified in large scale from cell cultures in vitro and used clinically for therapy in humans. Examples of such antibodies will be presented and compared to other methods of antibody generation.