Development of a Meso Scale Discovery ligand-binding assay for measurement of free (drug-unbound) target in nonhuman primate serum

Aim: To quantify the free form of a protein as a target-engagement biomarker in nonhuman primate serum, a Meso Scale Discovery ligand-binding assay was developed and qualified. Results: The initial assay produced an unexpected artifact when used to measure the free target in study samples dosed with drug. By using incurred study samples dosed with high drug levels to test assay performance, we developed an alternative assay that does not suffer from drug interference. Conclusion: Our work demonstrated that an assay designed to measure free target may not necessarily deliver reliable quantitation. In our case, incurred study samples dosed with drug proved to be useful in developing an alternative free assay that does not suffer from drug interference.