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

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Biochemistry
• Analytical Chemistry

Background:

• Ligand-binding assays (LBAs) were initially used to measure PRM-151 (recombinant human pentraxin-2) exposure.
• The LBA exhibited limitations, including a lack of dose-dependent exposure in certain preclinical species and inability to distinguish infused PRM-151 from endogenous PTX-2 in nonhuman primates.

Purpose of the Study:

• To develop a reliable method for measuring PRM-151 (PTX-2) drug exposure.
• To resolve discrepancies observed in preclinical pharmacokinetic studies.

Main Methods:

• A liquid chromatography-mass spectrometry (LC-MS) assay was developed to measure 'total' drug.
• This LC-MS method avoided interference from PTX-2's multiple binding partners, unlike the previous LBA.
• No immunoaffinity capture reagents were required for the LC-MS assay.

Main Results:

• The LC-MS assay confirmed the findings of the original LBA, including the lack of dose-dependent exposure.
• The LC-MS data provided a clearer understanding of PRM-151 pharmacokinetics.
• The observed exposure patterns were attributed to the drug's complex biodistribution.

Conclusions:

• The lack of dose-dependent exposure for PRM-151 is a genuine pharmacokinetic characteristic, not an assay artifact.
• The complex biodistribution, driven by diverse targets and functions of PTX-2, explains the observed exposure profile.
• LC-MS is a suitable method for measuring total drug exposure for complex molecules like PRM-151.