Inosine 5′-monophosphate dehydrogenase activity as a biomarker in the field of transplantation

Inosine 5′monophosphate dehydrogenase (IMPDH) is the rate limiting enzyme in the de novo synthesis of guanine nucleotides. The direct determination of target enzyme activity as a biomarker of mycophenolic acid (MPA) may help to estimate better the individual response to the immunosuppressant. However, the assessment of the clinical utility of this approach is limited by the diversity of the assay systems, which has not yet allowed the prospective assessment of this enzyme in larger patient cohorts. A recently validated and standardized assay allows the investigation of IMPDH activity in larger clinical studies. Although descriptive results from observational studies hold promise for a more individualized therapy in transplant medicine, more studies are needed to prospectively validate this approach.

► IMPDH activity reflects pharmacokinetic and pharmacodynamic variability of MPA.
► Large differences in pre-analytical performance exist.
► Standardized IMPDH assay has the potential to be a tool in management of MPA therapy.