Tenofovir Alafenamide Plasma Concentrations Are Reduced in Pregnant Women Living With Human Immunodeficiency Virus (HIV): Data From the PANNA Network.

BACKGROUND: Tenofovir alafenamide (TAF), a prodrug of tenofovir (TFV), is included in the majority of the recommended first-line antiretroviral regimens for patients living with human immunodeficiency virus (HIV), but there are limited data on TAF use in pregnant women. We aimed to examine the plasma pharmacokinetics of TAF and TFV in pregnant women from Europe. METHODS: Pregnant women living with HIV were included from treatment centers across Europe, and intensive pharmacokinetic sampling in the third trimester and postpartum was performed. Pharmacokinetic parameters of TAF and TFV were determined with noncompartmental analysis. The proportion of women with a TAF area under the curve (AUClast) below the target of 53.1 ng∗h/mL was determined. Clinical efficacy and safety outcome parameters were reported. RESULTS: In total, 20 pregnant women living with HIV were included. At the third trimester, geometric mean TAF AUClast and Cmax were decreased by 46% and 52%, respectively, compared with postpartum. TFV AUC0-24h, Cmax, and Ctrough decreased by 33%, 30%, and 34%, respectively. The proportion of women with a TAF AUClast < 53.1 ng∗h/mL was 6% at third trimester and 0% postpartum. One out of 20 women had a viral load > 50 copies/mL at third trimester and no mother-to-child transmission occurred. CONCLUSIONS: TAF plasma concentrations were reduced by about half in women living with HIV during third trimester of pregnancy but remained above the predefined efficacy target in the majority of the pregnant women. TFV concentrations were reduced by approximately 30% during third trimester. Despite the observed exposure decrease, high virologic efficacy was observed in this study.

Quantification of cobimetinib, cabozantinib, dabrafenib, niraparib, olaparib, vemurafenib, regorafenib and its metabolite regorafenib M2 in human plasma by UPLC-MS/MS.

A sensitive and selective ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous determination of seven oral oncolytics (two PARP inhibitors, i.e. olaparib and niraparib, and five tyrosine kinase inhibitors, i.e. cobimetinib, cabozantinib, dabrafenib, vemurafenib and regorafenib, plus its active metabolite regorafenib M2) in EDTA plasma was developed and validated. Stable isotope-labelled internal standards were used for each analyte. A simple protein precipitation method was performed with acetonitrile. The LC-MS/MS system consisted of an Acquity H-Class UPLC system, coupled to a Xevo TQ-S micro tandem mass spectrometer. The compounds were separated on a Waters CORTECS UPLC C18 column (2.1 × 50 mm, 1.6 µm particle size) and eluted with a gradient elution system. The ions were detected in the multiple reaction monitoring mode. The method was validated for cobimetinib, cabozantinib, dabrafenib, niraparib, olaparib, vemurafenib, regorafenib and regorafenib M2 over the ranges 6-1000, 100-5000, 10-4000, 200-2000, 200-20,000, 5000-100,000, 500-10,000 and 500-10,000 µg/L, respectively. Within-day accuracy values for all analytes ranged from 86.8 to 115.0% with a precision of <10.4%. Between-day accuracy values ranged between 89.7 and 111.9% with a between-day precision of <7.4%. The developed method was successfully used for guiding therapy with therapeutic drug monitoring in cancer patients and clinical research programs in our laboratory.

Development and Validation of a Bioanalytical Method to Quantitate Enzalutamide and its Active Metabolite N-Desmethylenzalutamide in Human Plasma: Application to Clinical Management of Patients With Metastatic Castration-Resistant Prostate Cancer.

BACKGROUND: Enzalutamide is a potent androgen-signaling receptor inhibitor and is licensed for the treatment of metastatic castration-resistant prostate cancer. N-desmethylenzalutamide is the active metabolite of enzalutamide. A method to quantitate enzalutamide and its active metabolite was developed and validated according to the European Medicine Agency guidelines. METHODS: Enzalutamide and N-desmethylenzalutamide were extracted by protein precipitation, separated on a C18 column with gradient elution and analyzed with tandem quadrupole mass spectrometry in positive ion mode. A stable deuterated isotope (D6-enzalutamide) was used as an internal standard. The method was tested and stability was studied in real-life patients with metastatic castration-resistant prostate cancer patients treated with enzalutamide. RESULTS: The calibration curve covered the range of 500-50,000 ng/mL. Within- and between-day precisions were <8% and accuracies were within 108% for both enzalutamide and N-desmethylenzalutamide. Precisions for lower limit of quantification level were <10% and accuracies within 116% for enzalutamide and N-desmethylenzalutamide. Enzalutamide and N-desmethylenzalutamide stability was proven for 24 hours for whole blood at ambient temperature and 23 days for plasma at both ambient temperature and 2-8°C. Long-term patient plasma stability was shown for 14 months at -40°C. CONCLUSIONS: This bioanalytical method was successfully validated and applied to determine plasma concentrations of enzalutamide and N-desmethylenzalutamide in clinical studies and in routine patient care.

Analytical challenges in quantifying abiraterone with LC-MS/MS in human plasma.

A method was developed and validated to quantify abiraterone in human plasma. During assay development, several analytical challenges were encountered: limited stability in patient samples, adsorption to glass, coelution with metabolites and carry-over issues. Limited stability (2 h) was found for abiraterone in fresh plasma as well as whole blood at ambient temperature. When kept at 2-8°C, abiraterone in plasma was stable for 24 h and in whole blood for 8 h. Adsorption of abiraterone to glass materials was addressed by using polypropylene throughout the method. Carry-over was reduced to acceptable limits by incorporating a third mobile phase into the gradient. The chromatographic separation of abiraterone with its multiple metabolites was addressed by using a longer analytical column and adjusting the gradient. Abiraterone was extracted by protein precipitation, separated on a C18 column with gradient elution and analyzed with tandem quadrupole mass spectrometry in positive ion mode. A stable deuterated isotope was used as the internal standard. The assay ranges from 1 to 500 ng/mL. Within- and-between-day precisions and accuracies were below 13.4% and within 95-102%. This bioanalytical method was successfully validated and applied to determine plasma concentrations of abiraterone in clinical studies and in regular patient care for patients with metastatic castration-resistant prostate cancer.