A LC–tandem MS assay for the simultaneous measurement of new antiretroviral agents: Raltegravir, maraviroc, darunavir, and etravirine

Raltegravir (RAL), maraviroc (MVC), darunavir (DRV), and etravirine (ETV) are new antiretroviral agents with significant potential for drug interactions. This work describes a sensitive and accurate liquid chromatography-tandem mass spectrometry (LC–MS/MS) method for the determination of plasma drug levels. Single-step extraction of RAL, MVC, DRV, ETV and RTV from plasma (100 μl) is performed by protein precipitation using 600 μl of acetonitrile, after the addition of 100 μl darunavir-d9 (DRV-d9) at 1000 ng/ml in MeOH/H2O 50/50 as internal standard (I.S.). The mixture is vortexed, sonicated for 10 min, vortex-mixed again and centrifuged. An aliquot of supernatant (150 μl) is diluted 1:1 with a mixture of 20 mM ammonium acetate/MeOH 40/60 and 10 μl is injected onto a 2.1 × 50 mm Waters Atlantis™-dC18 3 μm analytical column. Chromatographic separations are performed using a gradient program with 2 mM ammonium acetate containing 0.1% formic acid and acetonitrile with 0.1% formic acid. Analytes quantification is performed by electrospray ionisation-triple quadrupole mass spectrometry using the selected reaction monitoring detection in the positive mode. The method has been validated over the clinically relevant concentrations ranging from 12.5 to 5000 ng/ml, 2.5 to 1000 ng/ml, 25 to 10,000 ng/ml, 10 to 4000 ng/ml, and 5 to 2000 ng/ml for RAL, MRV, DRV, ETV and RTV, respectively. The extraction recovery for all antiretroviral drugs is always above 91%. The method is precise, with mean inter-day CV% within 5.1–9.8%, and accurate (range of inter-day deviation from nominal values −3.3 to +5.1%). In addition our method enables the simultaneous assessment of raltegravir–glucuronide. This is the first analytical method allowing the simultaneous assay of antiretroviral agents targeted to four different steps of HIV replication. The proposed method is suitable for the Therapeutic Drug Monitoring Service of these new regimen combinations administered as salvage therapy to patients having experienced treatment failure, and for whom exposure, tolerance and adherence assessments are critical.