No abstract

Antibody display technologies enable the successful isolation of antigen-specific antibodies with therapeutic potential. The key feature that facilitates the selection of an antibody with prescribed properties is the coupling of the protein variant to its genetic information and is referred to as genotype phenotype coupling. There are several different platform technologies based on prokaryotic organisms as well as strategies employing higher eukaryotes. Among those, phage display is the most established system with more than a dozen of therapeutic antibodies approved for therapy that have been discovered or engineered using this approach. In recent years several other technologies gained a certain level of maturity, most strikingly mammalian display. In this review, we delineate the most important selection systems with respect to antibody generation with an emphasis on recent developments.

Bispecific antibodies (bsAbs) and antibody-drug conjugates (ADCs) have already demonstrated benefits for the treatment of cancer in several clinical studies, showing improved drug selectivity and efficacy. In particular, simultaneous targeting of prominent cancer antigens, such as EGF receptor (EGFR) and c-MET, by bsAbs has raised increasing interest for potentially circumventing receptor cross-talk and c-MET-mediated acquired resistance during anti-EGFR monotherapy. In this study, we combined the selectivity of EGFR × c-MET bsAbs with the potency of cytotoxic agents via bispecific antibody-toxin conjugation. Affinity-attenuated bispecific EGFR × c-MET antibody-drug conjugates demonstrated high in vitro selectivity toward tumor cells overexpressing both antigens and potent anti-tumor efficacy. Due to basal EGFR expression in the skin, ADCs targeting EGFR in general warrant early safety assessments. Reduction in EGFR affinity led to decreased toxicity in keratinocytes. Thus, the combination of bsAb affinity engineering with the concept of toxin conjugation may be a viable route to improve the safety profile of ADCs targeting ubiquitously expressed antigens.

Bispecific antibodies (bsAbs) pave the way for novel therapeutic modes of action along with potential benefits in several clinical applications. However, their generation remains challenging due to the necessity of correct pairings of two different heavy and light chains and related manufacturability issues. We describe a generic approach for the generation of fully human IgG-like bsAbs. For this, heavy chain repertoires from immunized transgenic rats were combined with either a randomly chosen common light chain or a light chain of an existing therapeutic antibody and screened for binders against tumor-related targets CEACAM5 and CEACAM6 by yeast surface display. bsAbs with subnanomolar affinities were identified, wherein each separate binding arm mediated specific binding to the respective antigen. Altogether, the described strategy represents a combination of in vivo immunization with an in vitro selection method, which allows for the integration of existing therapeutic antibodies into a bispecific format.

Bispecific IgG-like antibodies can simultaneously interact with two epitopes on the same or on different antigens. Therefore, these molecules facilitate novel modes of action, which cannot be addressed by conventional monospecific IgGs. However, the generation of such antibodies still appears to be demanding due to their specific architecture comprising four different polypeptide chains that need to assemble correctly. This review focusses on different strategies to circumvent this issue or to enforce a correct chain association with a focus on common-chain bispecific antibodies.

No abstract

Yeast surface display emerged as a viable tool for the generation of human and murine monoclonal antibodies. This platform technology enables the careful definition of selection conditions, the potential for high‐throughput screening, as well as the isolation of antibodies recognizing predefined epitopes. In this study, the applicability of yeast surface display in combination with fluorescence‐activated cell sorting (FACS) for the isolation of antigen‐specific chicken‐derived antibodies is demonstrated. To this end, yeast‐displayed recombinant antibody libraries from splenic mRNA of chickens immunized with epidermal growth factor receptor (EGFR) and human chorionic gonadotropin (hCG) were constructed as single chain variable fragments (scFv) by overlap extension polymerase chain reaction. A large number of antigen binding scFvs were readily isolated in a convenient screening process. Target‐specific scFv‐Fc molecules were produced as soluble proteins and more extensively characterized by confirming specificity, thermostability and high affinity. Essentially, we demonstrated the biotechnological applicability of binders directed against both antigens via specific cellular binding for EGFR and in the context of a lateral flow test by utilizing hCG‐binding scFvs as capturing antibodies for pregnancy detection. Altogether, the described strategy using yeast surface display expands the repertoire of display methods for the isolation of antibodies resulting from chicken immunization campaigns.

Abstract:Monoclonal antibody therapeutics have proven to be successful treatment options for patients in various indications. Particularly in oncology, therapeutic concepts involving antibodies often rely on the so-called effector functions, such as antibody dependent cellular cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC), which are programed in the antibody Fc region. However, Fc-mediated effector mechanisms often seem to be insufficient in properly activating the immune system to act against tumor cells. Furthermore, long term treatments can lead to resistance against the applied drug, which is monospecific by nature. There is promise in using specific antibodies to overcome such issues due to their capability of recruiting and activating T-cells directly at the tumor site, for instance. During the last decade, two of these entities, which are referred to as Blinatumomab and Catumaxomab, have been approved to treat patients with acute lymphoblastic leukemia and malignant ascites. In addition, Emicizumab, which is a bispecific antibody targeting clotting factors IXa and X, was recently granted market approval by the FDA in 2017 for the treatment of hemophilia A. However, the generation of these next generation therapeutics is challenging and requires tremendous engineering efforts as two distinct paratopes need to be combined from two different heavy and light chains. This mini review summarizes technologies, which enable the generation of antibodies with dual specificities.