The Irony of Humanization: Alemtuzumab, the First, But One of the Most Immunogenic, Humanized Monoclonal Antibodies.

David Baker,Meleri Jones,Andrew Goodman,Gavin Giovannoni,Klaus Schmierer,Sharmilee Gnanapavan,Liaqat Ali,Lawrence Samkoff,Gareth Pryce,Gauri Saxena,Angray S Kang,Kathleen C Munger

doi:10.3389/fimmu.2020.00124

Abstract

Alemtuzumab was designed to reduce the immunogenicity of the parent CD52-specific rat immunoglobulin. Although originally marketed for use in cancer (Mabcampath®), alemtuzumab is currently licensed and formulated for the treatment of relapsing multiple sclerosis (Lemtrada®). Perhaps due to its history as the first humanized antibody, the potential of immunogenicity of the molecule has been considered inconsequential, and anti-drug antibodies (ADA) responses were similarly reported as being clinically insignificant. Nonetheless, despite humanization and depletion of peripheral T and B cells, alemtuzumab probably generates the highest frequency of binding and neutralizing ADA of all humanized antibodies currently in clinical use, and they occur rapidly in a large majority of people with MS (pwMS) on alemtuzumab treatment. These ADA appear to be an inherent issue of the biology of the molecule—and more importantly, the target—such that avoidance of immunogenicity-related effects has been facilitated by the dosing schedule used in clinical practice. At the population level this enables the drug to work in most pwMS, but in some individuals, as we show here, antibody neutralization appears to be sufficiently severe to reduce efficacy and allow disease breakthrough. It is therefore imperative that efficacy of lymphocyte depletion and the anti-drug response is monitored in people requiring additional cycles of treatment, notably following disease breakthrough. This may help inform whether to re-treat or to switch to another disease-modifying treatment.

Highlights

Alemtuzumab is a monoclonal antibody that is specific for the 21–28 kDa lymphocyte cell surface CD52 glycoprotein [1, 2]
To support clinical use of alemtuzumab in our clinical practice—as it is a valuable treatment for many people with multiple sclerosis (MS), and the possibility of third and fourth courses of treatment were available [5, 48]—we developed a novel assay to detect anti-drug antibodies (ADA) against alemtuzumab, using a synthetic recombinant construct Alem GloBody [64]
We have developed a stable adherent CHO cell line expressing human CD52 for use in a competition assay with sera and alemtuzumab conjugated with Alexa-488 [65]

Summary

INTRODUCTION

Alemtuzumab is a monoclonal antibody that is specific for the 21–28 kDa lymphocyte cell surface CD52 glycoprotein [1, 2]. Dosing schedule of alemtuzumab *(5), the occurrence of anti-drug antibodies (ADA), binding (BAbs), and neutralizing (NAbs) and adverse effects in people with multiple sclerosis (pwMS) following the treatment cycles in the pivotal CARE-MS I and II trials **(12, 13) and the biology, such as the kinetics of antibody formation [18, 19], which could influence the generation and/or action of ADA. Regulatory cells recover faster than potentially pathogenic memory T and B cells, allowing for control of MS [12] This early loss of immune tolerance may allow the generation of antibody-mediated secondary autoimmunity to develop, which occurs at a high frequency (∼40–50%) in pwMS within 5 years from infusion [5, 20, 48]. Consistent with this view, vaccine responses to common virus and recall antigens persist following alemtuzumab treatment, and the ability to mount responses to novel antigens is retained

CONCLUSIONS

Findings

ETHICS STATEMENT