Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies

Aims Idarucizumab, a humanized monoclonal anti-dabigatran antibody fragment, is effective in emergency reversal of dabigatran anticoagulation. Pre-existing and treatment-emergent anti-idarucizumab antibodies (antidrug antibodies; ADA) may affect the safety and efficacy of idarucizumab. This analysis characterized the pre-existing and treatment-emergent ADA and assessed their impact on the pharmacokinetics and pharmacodynamics (PK/PD) of idarucizumab. Methods Data were pooled from three Phase I, randomized, double-blind idarucizumab studies in healthy Caucasian subjects; elderly, renally impaired subjects; and healthy Japanese subjects. In plasma sampled before and after idarucizumab dosing, ADA were detected and titrated using a validated electrochemiluminescence method. ADA epitope specificities were examined using idarucizumab and two structurally related molecules. Idarucizumab PK/PD data were compared for subjects with and without pre-existing ADA. Results Pre-existing ADA were found in 33 out of 283 individuals (11.7%), seven of whom had intermittent ADA. Titres of pre-existing and treatment-emergent ADA were low, estimated equivalent to