Characterization of anti-drug antibody responses to the T-cell engaging bispecific antibody cibisatamab to understand the impact on exposure

Abstract

An appropriately designed pharmacokinetic (PK) assay that is sensitive for anti-drug antibody (ADA) impact on relevant exposure is an alternative strategy to understand the neutralizing potential of ADAs. However, guidance on how to develop such PK assays and how to confirm the functional ADA impact on exposure is missing. Here, the PK assay of a T-cell-engaging bispecific antibody, cibisatamab, was developed based on its mechanism of action (MoA). Using critical monoclonal anti-idiotypic (anti-ID) antibody positive controls as ADA surrogates, the impact on exposure was evaluated pre-clinically. In a phase I clinical trial (NCT02324257), initial data suggest that the combination of ADA and PK assays for correlation of the ADA response with cibisatamab exposure. To understand the neutralizing potential of patient-derived ADAs on drug activity, advanced ADA characterization has been performed. Structural binding analysis of ADAs to antibody domains of the drug and its impact on targeting were assessed. For this purpose, relevant patient ADA binding features were identified and compared with the specific monoclonal anti-ID antibody-positive controls. Comparable results of target binding inhibition and similar impacts on exposure suggest that the observed reduction of Cmax and Ctrough levels in patients is caused by the neutralizing potential of ADAs and allows a correlation between ADA response and loss of exposure. Therefore, the described study provides important functional aspects for the development of an appropriately designed PK assay for bispecific antibodies as an alternative option towards understanding the neutralizing ADA impact on exposure.

Keywords: ADA; PK; T cell engager; exposure; immunogenicity.

Figure 1

Development of a mechanism of action (MoA) based Pharmacokinetic (PK) assay that is sensitive for ADA impact on exposure. (A) Schemata of the MoA of cibisatamab with its dual functionality (dual fct). (B) Schemata of the PK Assay concept with its dual functionality (dual fct).

Figure 2

Correlation of persistent ADA response and loss of exposure using MoA-based PK assay. Increase in cibisatamab ADA titer and associated decrease in active cibisatamab exposure (patient B) in contrast to ADA negative patient with maintained active exposure (patient A).

Figure 3

ADA anti-CD3/CDR domain specificity characterization: Binding characteristics of four different monoclonal anti-idiotypic antibodies to modified anti-CD3 domains analyzed by ELISA (A) and biolayer interferometry (B). HC, heavy chain; LC, light chain; CDR, complementarity-determining region.

Figure 4

Inhibition of cell-based target CD3 receptor mediated luciferase activity by four different monoclonal anti-idiotypic antibodies as potential ADA positive controls. (A) Schemata of CD3ε-receptor mediated reporter cell line using anti-CD3 antibodies as stimulating control. (B) Effect of the four anti-idiotypic antibodies in CD3-mediated luciferase activation.

Figure 5

Patient-derived ADAs inhibit CD3ε-receptor mediated activation. (A) 10 selected patient samples with high titer ADA detection were tested in the CD3ε receptor mediated reporter assay with a complete loss of signal (B) Sample of patient 5 diluted in ADA-free human control serum to recovery CD3ε mediated activity.

Figure 6

Increase in Cibisatamab ADA titer and associated decrease in cibisatamab exposure. Dose-normalized cibisatamab Cmax and Ctrough by highest ADA-titer 4 weeks after treatment start. In patients with high ADA-titers (>810), both Cmax and Ctrough/min were relevantly decreased. Patients with low ADA titers (<810) tended to have Cmax values that were not relevantly smaller than in ADA-negative patients, although decrease in Ctrough/min may be more pronounced.