LC-MS/MS method for quantifying the HIV-1 broadly neutralizing antibody PGT 121.414.LS in human serum

Quantitation of human immunodeficiency virus-1 (HIV-1) broadly neutralizing antibodies (bNAbs) in human serum is required for clinical trials investigating the pharmacokinetics, pharmacodynamics, and drug interactions of these treatments. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is gaining interest as an alternative to ligand binding for therapeutic antibody quantitation in serum. We report the validation of a method using nonspecific purification and targeted LC-MS/MS to quantify PGT 121.414.LS (a bNAb in development for HIV-1 prevention and treatment) in human serum. High-resolution spectra of tryptic peptides derived from the variable region were obtained on an Orbitrap for surrogate peptide selection, followed by multiple reaction monitoring using triple quadrupole mass spectrometry. Surrogate peptides were evaluated for linearity and reproducibility across the therapeutic concentration range using immunopurification or ammonium sulfate precipitation. Using ammonium sulfate precipitation, linear calibration curves were validated over 10–500 μg/mL (LLOQ at 10 μg/mL) using stable isotope labeled peptide internal standards. Method accuracy and reproducibility were evaluated using quality control samples (QCs) at four concentrations in the linear range. The average concentrations of all QCs fell within ICH M10 acceptance criteria. Matrix effects were investigated at the low and high QC concentrations across six lots of human serum. Dilutional integrity, stability, and effects of hemolysis were also assessed. The method exhibits minimal carryover and negligible crosstalk. The assay provides accurate quantification of PGT 121.414.LS in serum over the range of concentrations anticipated in specimens from treated persons living with HIV (PLWH) after initial dosing and prior to subsequent dosing of PGT 121.414.LS.