Immunogenicity Assays Used in Support of Marketing Applications of Oligonucleotide Therapeutics

Oligonucleotide therapeutics (ONT) continue to emerge as a versatile new class of medicines. While relatively small in terms of molecular weight, ONT may trigger formation of anti-drug antibodies (ADA), which in turn may impact pharmacokinetics, pharmacodynamics, efficacy, and safety. Bioanalytical methodology for detection of ADA against protein-based therapeutics is well established, however, detection of ADA against ONT presents its own unique challenges. In this manuscript, the Immunogenicity Sub-team of AAPS Bioanalytical Community Oligonucleotide Discussion Group, reviewed bioanalytical assays used to detect and characterize ADA as reported in documents supporting marketing applications of oligonucleotide therapeutics. Based on the available data and the Authors' own experience, a direct ELISA is by far the most common format used for detection of ADA against ONT. Characterization of ADA neutralizing activity is not performed. No issues with insufficient drug tolerance have been reported and postmarketing requirements to improve assay sensitivity are rare. Data generated in the Authors' laboratories indicate that difficulties with low sensitivity of immunogenicity assays for ONT appear to stem from difficulties in raising and purifying high affinity positive control antibodies. Given the inherently low immunogenic potential of ONTs, generation of positive controls with sufficient affinity and titer may necessitate multiple immunizations with immunogens incorporating repetitive sequence motifs, together with alternation of carrier proteins across immunization cycles.