DNDI-6148

DNDI-6148 is a promising new oral drug for the treatment of cutaneous leishmaniasis (CL), a parasitic neglected tropical disease that affects impoverished populations worldwide. Preclinical target site pharmacokinetics (PK) studies are necessary to evaluate the actual exposure to DNDI-6148 of Leishmania parasites in the skin. To facilitate these investigations, we have developed and validated a reversed phase ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method to quantify DNDI-6148 in relevant target site PK samples, adhering to the relevant International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) M10 guideline on bioanalytical method validation. Full validation was performed for the surrogate biomatrices human K₂EDTA plasma, enzymatic digestion buffer and skin microdialysate. Partial validation was conducted for mouse K₂EDTA plasma and tissues. The tissue samples, including mouse skin, liver and spleen, were homogenized using a collagenase A-based enzymatic homogenization workflow. This method was found to be 2.9-fold more effective in extracting DNDI-6148 from skin than the commonly used mechanical homogenization. Protein precipitation was subsequently carried out for all biomatrices. A surrogate biomatrix was used for each method and the range was specifically developed for its intended application, resulting in a linear concentration range of 5.00-2000 ng/mL, 2.00-1000 ng/mL, and 3.00-600 ng/mL for human K₂EDTA plasma, enzymatic digestion buffer and microdialysate, respectively. Each biomatrix had intra- and inter-run accuracy and precision within 15 % for all concentration levels. Matrix effects did not affect the determination of DNDI-6148, since the stable isotopically-labelled internal standard for DNDI-6148 effectively compensated for these matrix effects. Total recovery across all methods was between 73.5 % and 81.3 % (CV ≤4.5 %). DNDI-6148 was stable under various conditions in all the tested biomatrices. However, a decrease in its concentration was observed during homogenization, for which the internal standard corrected adequately. The suitability of the method for use in future preclinical research involving DNDI-6148 was demonstrated in a preclinical target site PK study using a CL-infected murine model.