Evolution of phage display libraries for therapeutic antibody discovery

Abstract

Monoclonal antibodies (mAbs) and their derivatives have emerged as one of the most important classes of biotherapeutics in recent decades. The success of mAb is due to their high versatility, high target specificity, excellent clinical safety profile, and efficacy. Antibody discovery, the most upstream stage of the antibody development pipeline, plays a pivotal role in determination of the clinical outcome of an mAb product. Phage display technology, originally developed for peptide directed evolution, has been extensively applied to discovery of fully human antibodies due to its unprecedented advantages. The value of phage display technology has been proven by a number of approved mAbs, including several top-selling mAb drugs, derived from the technology. Since antibody phage display was first established over 30 years ago, phage display platforms have been developed to generate mAbs targeting difficult-to-target antigens and tackle the drawbacks present in in vivo antibody discovery approaches. More recently, the new generation of phage display libraries have been optimized for discovery of mAbs with "drug-like" properties. This review will summarize the principles of antibody phage display and design of three generations of antibody phage display libraries.

Keywords: Antibody developability; antibody selection; library design; phage display; therapeutic antibody discovery.

Figure 1.

Types of antibody phage display libraries (upper left panel), library construction (lower left panel) and antibody selection (right panel). According to source of diversity, antibody phage display libraries can be categorized into three types: natural library, synthetic library, and semisynthetic library. In a typical phagemid system, variable regions of light and heavy chains, either cloned from a natural immunoglobulin repertoire or designed and synthesized in vitro, are cloned into a phage display vector (phagemid), with one of the chains genetically fused to pIII of phage for display. The library pool is then transformed to E.Coli host cells. By infection with helper phage, which provides all the components for phage production, a phage library is generated. Taking solid-phase panning as an example, the phage library is incubated with immobilized antigen. After washing, nonspecific phages are removed and antigen-specific phages stay with the antigen. The bound phages are then dissociated from the antigen by diverse methods, e.g., low-Ph elution, enzymatic cleavage. Lastly, eluted phages are subjected to propagation in E.Coli host cells. After iterative rounds of panning, antigen-specific clones are enriched. Typically, output phages from middle and late rounds of panning are subjected to sequencing and binding characterization for obtaining both sequence diversity and high affinity, respectively.