Validation of an Electrospray Ionization LC-MS/MS Method for Quantitative Analysis of Raltegravir, Etravirine, and 9 Other Antiretroviral Agents in Human Plasma Samples

Background: Raltegravir is the first human immunodeficiency virus-1 (HIV-1) integrase inhibitor used in treatment-experienced patients who have evidence of viral replication and HIV-1 strains resistance to multiple antiretroviral regimens. Etravirine is a novel NNRTI, active against HIV-1 strains harboring multiple NNRTI mutations. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of raltegravir, etravirine, and 9 other antiretroviral agents (amprenavir, atazanavir, darunavir, efavirenz, indinavir, lopinavir, ritonavir, saquinavir, and tipranavir) in plasma at the concentrations associated with therapy. Materials and Methods: The ritonavir analog, methyl indinavir, and lopinavir-d8 were used as internal standards, added to 100 μL of plasma sample prior to a protein precipitation using methanol. Chromatographic separation was achieved on a C18 HPLC column (Waters Sunfire 100 × 2.1 mm, 3.5 μm) with a mobile phase gradient at a flow rate of 0.3 mL/min. Five μL of sample were injected into the LC-MS/MS system (Waters Quattro Premier XE) to determine concentrations of raltegravir, etravirine, and other antiretroviral agents. Results and Discussion: This method showed an excellent linearity for all calibration curves (r 2 > 0.998). The lower limit of quantification was established at 5 ng/mL for raltegravir and 40 ng/mL for etravirine, with precision and accuracy within ±20% and 80% to 120% for all analytes. Intraassay and interassay precision and inaccuracy ranged from -9.2% to 6.9% for raltegravir and from —14.3% to 12.3% for etravirine and were less than 15% for all other compounds. No matrix effect was observed for any of the antiretrovirals studied. Conclusion: A rapid, specific, and sensitive LC-MS/MS method for quantification of raltegravir, etravirine, and 9 other antiretrovirals in human plasma was developed and was successfully applied for routine therapeutic drug monitoring.