Protein engineering and preclinical development of a GM‐CSF receptor antibody for the treatment of rheumatoid arthritis

Abstract

BACKGROUND AND PURPOSEFor antibody therapies against receptor targets, in vivo outcomes can be difficult to predict because of target-mediated clearance or antigen 'sink' effects. The purpose of this work was to engineer an antibody to the GM-CSF receptor a (GM-CSFRa) with pharmacological properties optimized for chronic, s.c. treatment of rheumatoid arthritis (RA) patients. EXPERIMENTAL APPROACHWe used an in silico model of receptor occupancy to guide the target affinity and a combinatorial phage display approach for affinity maturation. Mechanism of action and internalization assays were performed on the optimized antibody in vitro before refining the modelling predictions of the eventual dosing in man. Finally, in vivo pharmacology studies in cynomolgus monkeys were carried out to inform the predictions and support future clinical development. KEY RESULTSAntibody potency was improved 8600-fold, and the target affinity was reached. The refined model predicted pharmacodynamic effects at doses as low as 1 mg kg -1 and a study in cynomolgus monkeys confirmed in vivo efficacy at 1 mg kg -1 dosing. CONCLUSIONS AND IMPLICATIONSThis rational approach to antibody drug discovery enabled the isolation of a potent molecule compatible with chronic, s.c. self-administration by RA patients. We believe this general approach enables the development of optimal biopharmaceuticals.

Model‐Based Discovery and Development of Biopharmaceuticals: A Case Study of Mavrilimumab

“…The model also assumed a parallel target receptor‐mediated clearance pathway with a 1‐hour receptor turnover half‐life. From simulations, a theoretical affinity (K D ) of 0.1 nM would be required to achieve and maintain >99% occupancy of GM‐CSFRα in blood for over 14 days at a subcutaneous dose of 1 mg/kg in subjects with RA ( Figure ) . A number of biologic agents with various dosing regimens are available for the treatment of RA.…”

“…A lead IgG antibody, 574D04, was subsequently identified and further optimized to achieve <0.1 nM in vitro potency and affinity. Upon entering preclinical and clinical development, 574D04 was named CAM‐3001 and later mavrilimumab …”

“…For target‐binding and nonlinear elimination pathway, the model assumed a 20 pM granulocyte‐macrophage colony‐stimulating factor receptor (GM‐CSFR)α expression level and a 1‐hour receptor internalization rate. Republished with permission of John Wiley and Sons, Inc., from Minter et al …”

“…A starting dose of 0.01 mg/kg was selected based on translational simulations for minimal and transient target receptor blockade. On the other hand, a top dose of 10 mg/kg was recommended for up to 12‐week suppression of GM‐CSF activity for PD evaluation in subjects with RA …”

Affinity maturation of a novel antagonistic human monoclonal antibody with a long VHCDR3 targeting the Class A GPCR formyl-peptide receptor 1

“…18 Therapeutic antibodies are often required to be of higher affinity than is typical for antibodies derived by immunization of animals or selected from na€ ıve in vitro display libraries; however, in vitro affinity maturation of an antibody is ideally carried out using a purified source of the target protein that is structurally and functionally relevant to ensure antibodies with the desired activity are obtained. 19,20 Therefore, affinity optimization of antibodies targeting complex integral membrane proteins such as GPCRs, particularly those with relatively small extracellular regions, is a significant challenge limiting the availability of suitable antibodies to modulate this important group of potential therapeutic targets. FPR1 has small extracellular loops and is unstable in purified form; therefore, it can be seen to exemplify a typically challenging GPCR for antibody generation and engineering.…”