A novel physiologically-based pharmacokinetic model to estimate reduced CYP3A4 activity in cancer patients utilizing the neutrophil-to-lymphocyte ratio as an inflammatory marker.

purposeIn advanced cancer patients the CYP3A4-mediated clearance of drugs is dependent on the severity of inflammation. In a study in patients with advanced cancer (n = 44) with solid tumors, prior to cancer treatment, high inter-patient variability was observed in the plasma pharmacokinetic (PK) parameters of the CYP3A4 substrate midazolam. The neutrophil-to-lymphocyte ratio (NLR) was used to categorize the degree of inflammation of each patient and in turn to correlate increases in NLR to decreases in CYP3A4 expression.

methodsPatients with NLR ≥ 5 were categorized as having high inflammation, and patients with NLR < 5 as having low-to-moderate inflammation. A physiologically-based PK (PBPK) model of midazolam PK and a top-down approach was used to determine the reductions in CYP3A4 abundance in the liver and gut wall needed to match the PK parameters of midazolam in the NLR ≥ 5 and NLR < 5 groups of patients.

resultsThe midazolam mean CL/F was 33 L/h in the NLR < 5 group, and midazolam CL/F was 20 L/h in the NLR ≥ 5 group. To match the PK of midazolam in the NLR < 5 group, the CYP3A4 expression was reduced 40% in both the liver and the gut. In the NLR ≥ 5 group, CYP3A4 expression was reduced approximately 40% in the liver and at least 90% in the gut to produce the best fit.

conclusionOverall, these results support that NLR may be used as an inflammatory marker that broadly correlates to inflammation-driven changes in CYP3A4 activity.