Dried blood spot LC-MS/MS quantification of voclosporin in renal transplant recipients using volumetric dried blood spot sampling

Abstract

Voclosporin is a potent immunosuppressive agent currently approved for treating active lupus nephritis. Based on its potential antiviral activity, it has also been investigated as an immunosuppressive drug in an investigator-initiated study involving SARS-CoV-2 positive kidney transplant recipients. As with many immunosuppressive agents, optimizing dosing regimens to maintain therapeutic efficacy while minimizing toxicity remains a key challenge in clinical practice. To balance the prevention of organ rejection and the risk of infection, precise therapeutic drug monitoring is essential.

Dried blood spot (DBS) sampling has enabled the development of remote voclosporin monitoring. In this study, we report the development and analytical validation of a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for quantifying voclosporin in dried blood spots. Method development built upon existing assays for tacrolimus, everolimus, sirolimus, cyclosporin, mycophenolic acid, creatinine, and iohexol in DBS, as well as voclosporin quantification in whole blood using LC-MS/MS. HemaXis™ volumetric blood spot devices were used for sample collection, and sample purification relied on extracting voclosporin from DBS samples. Stable isotopically labeled voclosporin-D4 served as the internal standard.

Bland–Altman and Passing–Bablok analyses were conducted for cross-validation between whole blood and DBS samples. The method was successfully validated according to the ICH M10 guidelines. The dynamic range of the assay was 10–600 µg/L, with an excellent mean correlation coefficient of 0.9978. Both within-run and between-run precision and accuracy met all acceptance criteria. Cross-validation against the whole blood method showed highly comparable results. This validated DBS LC-MS/MS method offers an efficient and accessible workflow for therapeutic drug monitoring in kidney transplant recipients and supports remote pharmacokinetic studies in lupus nephritis patients receiving voclosporin treatment.