Concerted application of LC-MS and ligand binding assays to better understand exposure of a large molecule drug.

AIM: A ligand-binding assay (LBA) was used to measure exposure of PRM-151, the recombinant form of human pentraxin-2 (PTX-2), a complex pentamer with multiple binding partners. However, the assay showed a lack of dose-dependent exposure in select preclinical species and it could not differentiate the infused PRM-151 from the endogenous PTX-2 in nonhuman primates. MATERIALS & METHODS: Instead of assessing interference from its multiple binding partners, which could be time consuming and laborious, a LC-MS assay avoid of these interference was implemented to measure 'total' drug without the use of immunoaffinity capture reagents. RESULTS & CONCLUSION: The resultant LC-MS data confirmed the original data and the lack of dose-dependent exposure is now understood to be due to the multiple and diverse targets and functions and resultant complex biodistribution rather than an assay artifact.