HIV combination drug therapies: development and validation of an LC-MS-MS method for simultaneous quantitation of abacavir, dolutegravir, and lamivudine in rat matrices in support of toxicology studies.

Abacavir (ABC), Dolutegravir (DTG), and Lamivudine (3TC) are part of a fixed-dose combination medication for the treatment of HIV. The three drugs offer different but complementary mechanisms of action by inhibiting reverse transcriptase and integrase, and ultimately inhibiting HIV replication. Due to the lack of information regarding long-term safety following in utero exposure, we are evaluating potential toxicity to offspring following in utero exposure to this combination therapy in Hsd:Sprague Dawley®SD® (HSD) rats, including cardiovascular toxicity and neurotoxicity. Generating internal exposure data are integral to putting toxicological findings into context. The objective of this work was to develop and validate a method to simultaneously quantitate ABC, DTG, and 3TC in rat matrices following exposure to this combination. The method used protein precipitation of plasma, fetal, placental, brain, or heart homogenate, followed by ultra-performance liquid chromatography-tandem mass spectrometry. In adult Sprague Dawley rat plasma, the method was linear (r ≥ 0.99) over the range 10/15/5 to 10,000/15,000/5000 ng/mL for ABC/DTG/3TC and recovery was ≥92% for all three analytes at all concentration levels. The limits of detection were 2.22, 3.69, and 0.978 ng/mL for ABC, DTG, and 3TC, respectively. Intra- and inter-day precision was ≤8.7% relative standard deviation (RSD), and relative error (RE) ≤±12.0% for standards prepared at 20/30/10, 400/600/200, and 5000/7500/2500 ng/mL. Matrix standards as high as 40/60/20 µg/mL could be diluted into the calibration range (RE≤±3.5% and RSD ≤2.4%). The method was evaluated for HSD rat maternal plasma and fetal, placental, brain, and heart homogenates (mean RE ≤±15.0% and RSD ≤8.6%). Analyte stability was demonstrated in extracted plasma for 2 days at different temperatures, and in various matrices stored at -80°C for at least 32 days (80-113% of Day 0 concentrations). These data demonstrate that this simple and efficient method is suitable for quantitation of ABC, DTG, and 3TC in rat matrices generated from toxicology studies. The method can easily be adapted to other biological matrices and species (e.g. human).