Recombinant Anti-idiotypic Antibodies in Ligand Binding Assays for Antibody Drug Development

HPLC-MS/MS-based quantification of human monoclonal antibodies targeting SARS-CoV-2 in the presence of endogenous SARS-CoV-2 antibodies in human serum

Antibodies for treatment and prophylaxis against SARS-CoV-2 are needed particularly for immunocompromised individuals, who cannot adequately benefit from vaccination. To address this need, Aerium Therapeutics is developing antibodies targeting the SARS-CoV-2 spike protein. A bioanalytical method to quantify fully human monoclonal antibodies in a population with widely varying anti-spike antibody titers is required to investigate the pharmacokinetics of these antibodies in clinical trials. To eliminate interference from endogenous anti-spike protein antibodies, an HPLC-MS/MS assay was developed to quantify the investigational monoclonal antibodies (AER001 and AER002) by targeting signature peptides spanning the monoclonal antibodies' CDR regions. By optimizing and comparing affinity capture and ammonium sulphate precipitation, it was demonstrated that both procedures allowed accurate and precise quantification of AER001 and AER002 in human serum with comparable sensitivity. Ammonium sulphate precipitation outperformed immunocapture due to its simplicity and speed at lower cost and a full bioanalytical method validation was performed in human serum. The assay was also validated for human nasal lining fluid extract with a 50-fold lower limit of quantification and was shown to deliver similar sensitivity to previously published affinity capture HPLC-MS/MS assays. Finally, the CDR-derived signature peptides were also generated by tryptic digestion of blank serum in some individuals, an important caveat for HPLC-MS/MS strategies targeting human monoclonal antibodies. In summary, the presented results show that ammonium sulphate precipitation and HPLC-MS/MS allow accurate and precise quantification of monoclonals in clinical studies. The developed methods demonstrate that HPLC-MS/MS can reliably quantify human monoclonal antibodies even when endogenous antibodies with overlapping specificities are present and are crucial for the clinical testing of two investigational COVID-19 monoclonals.

Peptide Mimotope-Enabled Quantification of Natalizumab Arm Exchange During Multiple Sclerosis Treatment

BACKGROUND

Natalizumab, a therapeutic antibody used to treat multiple sclerosis, undergoes in vivo Fab arm exchange to form a monovalent bispecific antibody. Although highly efficacious, the immunosuppressive activity of natalizumab has been associated with JC polyomavirus-driven progressive multifocal leukoencephalopathy (PML). Development of assays that can distinguish between and quantify bivalent (unexchanged) and monovalent (exchanged) forms of natalizumab in clinical samples may be useful for optimizing extended interval dosing and reducing the risk of PML.

METHODS

In vitro natalizumab arm exchange was conducted, along with peptide mimotope and anti-idiotype surface capture chemistry, to enable the development of enzyme-linked immunosorbent assays.

RESULTS

An assay using a unique peptide Veritope TM was developed, which can exclusively bind to bivalent natalizumab. In combination with enzyme-linked immunosorbent assays that quantifies total natalizumab, the assay system allows quantification of both natalizumab forms.

CONCLUSIONS

In this article, a novel assay for the quantification of unexchanged and exchanged natalizumab variants in clinical samples was developed. This assay will enable investigations into the clinical significance of the relationship of PK/PD with the monovalent-to-bivalent ratio, as it relates to the efficacy of the drug and risk of PML.

Development of an immunoassay for aglycosylated murine IgG1 in mouse serum via generation of a specific tool antibody

Aim: To develop a method for the quantitation of effector functionless mouse surrogate IgG1 drug molecules in mouse matrices. Materials & methods: A panel of antibodies that bound specifically to N297G mutation-containing mouse IgG molecules was generated in rats. The panel was screened to identify an antibody that could be used as both the capture and detection reagent in an electrochemiluminescent immunoassay. Results & conclusion: The quantitative assay developed with the N297G-specific antibody passed acceptance criteria across multiple IgG1 fragment crystallizable (Fc)-containing protein formats and provides accurate quantitation of the total levels of mouse surrogate protein Fc present in in vivo mouse serum samples. These results are useful in understanding drug integrity and the development of precise pharmacokinetic/pharmacodynamic relationships.