Peripheral blood mononuclear cells isolation from mouse and rabbit blood to quantify active nucleotide and define brincidofovir dose for smallpox.

Aim: Brincidofovir has been approved by the US FDA for the treatment of smallpox via the "Animal Rule". The active moiety, cidofovir diphosphate (CDV-PP), was measurable in human peripheral blood mononuclear cells (PBMCs), but quantitation in animals was challenging given their limited blood volume. The aim of this study was to optimize PBMC isolation from rabbit and mouse blood to allow quantitation of CDV-PP.Materials & methods: PBMC isolation methods using various separation media were evaluated using blood from naive and brincidofovir-dosed animals. CDV-PP was quantified using liquid chromatography tandem mass spectrometry.Results & conclusion: PBMC isolation yields were increased by >fourfold compared with yields obtained using human methods, allowing cross-species exposure comparisons.