An ex vivo potency assay to assess active drug levels of a GLP-1 agonistic peptide during preclinical safety studies

During development of biologics, safety and efficacy assessments are often hampered by immune responses to the treatment. To assess active exposure of a drug peptide in a toxicology study, we developed an ex vivo potency assay which complemented the total drug quantification assay. Compound activity was assessed in samples of treated monkeys by cell-based cAMP measurements. For each animal, activity was compared with its predose sample to which the compound has been added at the postdose concentration as determined by a total LC-MS/MS assay. We were able to show that despite a high total test compound level, activity was reduced tremendously in antidrug-antibody-positive monkeys. Therefore, the applied ex vivo potency assay supplements drug quantification methods to determine active exposures.