Senior Principal Scientist Merck & Co., Inc. West Point, Pennsylvania
Islatravir (MK-8591), ISL is a nucleoside reverse transcriptase translocation inhibitor in phase 2 clinical trials. The compound is targeted to treat and prevent HIV infection. Intracellular Islatravir-triphosphate (ISL-TP) is the active metabolite, and its concentration levels are generally measured in peripheral blood mononuclear cells (PBMCs) samples. Typically, PBMC isolation requires large blood volumes, processing and analysis are laborious and complicated, and data quality relies on the PBMC isolation skills of the clinical staff. In addition, triphosphates are inherently unstable compounds, and samples require special handling and storage. Our aim was to develop a patient centric approach involving the measurement of ISL-Diphosphate (ISL-DP) and ISL-TP concentrations in dried blood to replace PBMC collection in future studies. Our research focused on the development of a method using Volumetric Absorptive Microsampling (VAMS) that could be employed for home sampling and could be used to monitor compliance in support of HIV trials.
In this talk we will describe the method development strategy and assessments to measure free or total Islatravir (ISL-DP + ISL-TP) in VAMS blood. Indirect analysis of ISL-phosphates was performed by monitoring the total ISL from samples after enzymatic hydrolysis at 37C using acid phosphatase. The typical assay performance characteristics necessary for VAMS method qualification including accuracy, precision, selectivity, sensitivity, recovery/matrix effect, hematocrit effects, stability and extractability will be presented.
The assay for total Islatravir was applied to support on-going clinical studies with Islatravir where smart sampling techniques, namely, venous and fingerstick VAMS, and Tasso (OnDemand-Capillary) were implemented. Based on preliminary results and PK assumptions, we will show that SMART PK sampling may eliminate clinic visits and/or PBMC collection through bridging of PK with Total-ISL in VAMS blood vs ISL-TP in PBMC or ISL in plasma. We’ll also present the issues and challenges with the different sampling techniques, and the subjects’ preferences in the clinical trial.
develop indirect methods for the analysis of unstable small molecules (i.e. nucleoside phosphates) in dried blood (VAMS)
identify bioanalytical issues in the analysis of unstable compounds in dried blood
evaluate strategies to improve mass spectrometer sensitivity in support of microsampling
gain insights into the issues and challenges with the different micro sampling techniques, as well as into subjects’ preferences in the clinical trial.