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Arginase-2 Inhibitory Antibody
Cancer Research Horizons
Antibody
Oncology
Hit To Lead or Lead Optimization
Abstract
Affinity maturation is a powerful technique in antibody engineering for the in vitro evolution of antigen binding interactions. Key to the success of this process is the expansion of sequence and combinatorial diversity to increase the structural repertoire from which superior binding variants may be selected. However, conventional strategies are often restrictive and only focus on small regions of the antibody at a time. In this study, we used a method that combined antibody chain shuffling and a staggered-extension process to produce unbiased libraries, which recombined beneficial mutations from all six complementarity-determining regions (CDRs) in the affinity maturation of an inhibitory antibody to Arginase 2 (ARG2). We made use of the vast display capacity of ribosome display to accommodate the sequence space required for the diverse library builds. Further diversity was introduced through pool maturation to optimize seven leads of interest simultaneously. This resulted in antibodies with substantial improvements in binding properties and inhibition potency. The extensive sequence changes resulting from this approach were translated into striking structural changes for parent and affinity-matured antibodies bound to ARG2, with a large reorientation of the binding paratope facilitating increases in contact surface and shape complementarity to the antigen. The considerable gains in therapeutic properties seen from extensive sequence and structural evolution of the parent ARG2 inhibitory antibody clearly illustrate the advantages of the unbiased approach developed, which was key to the identification of high-affinity antibodies with the desired inhibitory potency and specificity.
We have developed a first-in-class, therapeutic-quality antibody that inhibits human Arginase-2 and are seeking a partner with interest in arginase in tumour immunosuppression and other areas. Originating from the Cancer Research Horizons–AstraZeneca Antibody Alliance Laboratory, lead-optimised molecule C0021061 was developed using phage display technology, and shown to demonstrate potent nM inhibition of Arg2 enzymatic activity in vitro, favourable pharmacokinetics and a novel allosteric mechanism of non-competitive Arg2 inhibition (as revealed by X-ray crystallographic studies). The rationale for exploring the role of Arginase-2 (Arg2) in tumour immunosuppression is based on Frank Mussai’s early work showing that AML creates an arginase-dependent immunosuppressive microenvironment.
Since then, dysregulated expression of Arg2 in the tumour microenvironment resulting in an immunosuppressive niche has been reported in other papers as well. As a result of these findings, we sought to explore the hypothesis that an Arg2-specific inhibitory monoclonal antibody might restore anti-tumour immunity in cancer patients. Data showing that C0021061 is able to reverse the Arg2-mediated suppression of T cell proliferation in vitro, taken with other information, supports that these original findings indeed seem worth further exploration.
• Lead-optimised antibody that is potent and highly specific to human Arginase-2
• Potent nM inhibition of Arg2 enzymatic activity in vitro and ability to fully reverse Arg2-mediated suppression of T cell proliferation in vitro
• A novel allosteric mechanism of non-competitive Arg2 inhibition as revealed by X-ray crystallographic studies
• Favourable pharmacokinetics
• Arg2 overexpression documented in various cancer and non-cancer indications
Torquil Jackson
PCT-EP2020-073579 (2020.08.21)
Patent Family: KR, US, EP, JP, CN
• "Structural and functional characterization of C0021158, a high-affinity monoclonal antibody that inhibits Arginase 2 function via a novel non- competitive mechanism of action". Mark Austin et al. MAbs. 2020 Jan-Dec;12(1):1801230
• "Extensive sequence and structural evolution of Arginase 2 inhibitory antibodies enabled by an unbiased approach to affinity maturation". Denice T. Y. Chan et al. Proc Natl Acad Sci U S A. 2020 Jul 21;117(29):16949-16960
