Bi-specific and tri-specific antibodies- the next big thing in solid tumor therapeutics

Abstract

Antibody-based therapy has revitalized the world of cancer therapeutics since rituximab was first approved for the treatment of Non-Hodgkin's Lymphoma. Monoclonal antibodies against cancer antigens have been successful strategies for only a handful of cancer types due to many reasons including lack of antibody specificity and complex nature of tumor milieu which interfere with antibody efficacy. Polyspecific antibodies are promising class of anti-cancer agents which can be directed at multiple tumor antigens to eradicate tumor cells more precisely and effectively. They may overcome some of these limitations and have already changed treatment landscape for some malignancies such as B cell acute lymphoblastic leukemia. Pre-clinical studies and early phase clinical trials have demonstrated that this approach may be an effective strategy even for solid tumors. This review focuses on the development of bispecific and trispecific antibody therapy for the treatment of solid tumor malignancies and highlights the potential they hold for future therapies to come.

Keywords: Bispecific antibody; Immunotherapy; Solid tumor; Trispecific antibody.

Fig. 1

a: Some formats of IgG –like bispecific antibodies and a trispecific antibody. (A) Quadroma created by combining the light and heavy chains of two different monoclonal antibodies resulting in two antigen binding sites aimed at different tumor antigens eg. Catumaxomab (B) Two antibody chains with engineered CH3 domain to create a “knob” in one heavy chain and a “hole” in the other to promote heterodimerization. This allows only specific pairing of heavy chains to reduce mispairing. (C) Variable domains of two mABs fused to create a dual- specific antibody (D) CrossMab exchanging of the CH1 domain of one heavy chain with the constant domain of the corresponding light chain for better light chain pairing (E) Bispecific antibody with two unique antigen-binding sites and a chemotherapy payload attached to the constant domain (F) Trispecific antibody engineered to bind to three different ligands on tumor cell. b: Some formats of bispecific antibody fragments and fusion proteins. (A) scFvs – Combination of the variable region of one light chain with the variable region of one heavy chain fragment is the basic element for antigen binding. (B) bi-Nanobody- Combination of two different single variable heavy chain domains which are able to bind different tumor antigens. (C) BiTE- Tandem single chain variable fragments from different antibodies joined by a flexible peptide chain. (D) Diabody – Bivalent molecules composed of two chains each comprising a variable light chain and variable heavy chain domain, either from the same or different antibodies. (E) TandAbs - Two pairs of variable light chain and variable heavy chain domains are connected in a single polypeptide chain to form a tetravalent tandAb. (F) DNL-Fab3 – Trivalent bispecific antibody composed of three Fab fragments joined by the utilization of the specific interaction between the regulatory subunits of cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) and the anchoring domains of A kinase anchoring proteins (AKAP). (G) DART – Two polypeptide chains derived from the variable heavy chain from one molecule linked to a variable light chain of another molecule. (H) DART-Fc - DARTs with a Fc fragment designed to prolong serum retention time. (I) scFv-HAS-scFV- Association of two single chain variable fragments through modified dimerization domains

Fig. 2

Schematic showing different formats of immunotherapy binding to the antigen on the tumor cell: (1) monoclonal antibody, (2) bispecific antibody, (3) trispecific antibody, (4) bispecific T cell engager made from two single chain antibody fragments, and (5) CAR T cell therapy which is comprised of light chain and heavy chain variable fragments joined by a flexible linker

Fig. 3

Trispecific antibody. Usually created by using variable domain genes if specific monoclonal antibodies. In this case, antigen-binding site 1 is bivalent and engages with an antigen on effector cell, antigen-binding sites 2 and 3 engage antigens 1 and 2 on tumor cells