Direct Comparison of Radioimmunoassay and LC–MS/MS for PK Assessment of Insulin Glargine in Clinical Development

BACKGROUND: A direct comparison of radioimmunoassay (RIA) and LC-MS/MS for insulin glargine quantification in human plasma is provided. RESULTS: Compared with the RIA, the LC-MS/MS assay exhibited comparable/improved sensitivity (LLOQ at 0.1 ng/ml [˜16.7 pM or 2.8 μU/ml] for glargine and its metabolites M1 and M2, respectively) and ruggedness. Most importantly, it demonstrated a superior specificity advantage against the interference from endogenous insulin, exogenous insulin analogs (e.g., Novolog(®), Humalog(®) or Levemir(®), routine treatment for diabetes mellitus) and potentially pre-existing anti-insulin antibodies in patient samples. The data obtained from diabetic patients suggested the LC-MS/MS assay substantially improved pharmacokinetic characterization of glargine. CONCLUSION: LC-MS/MS overcame common limitations of RIA, and provided critically needed specificity to support glargine clinical development, without sacrificing assay sensitivity and ruggedness.