Pharmacometabonomic association of cyclophosphamide 4-hydroxylation in hematopoietic cell transplant recipients

Abstract

The widely used alkylating agent cyclophosphamide (CY) has substantive interpatient variability in the area under the curve (AUC) of it and its metabolites. Numerous factors may influence the drug-metabolizing enzymes that metabolize CY to 4-hydroxycyclophosphamide (4HCY), the principal precursor to CY's cytotoxic metabolite. We sought to identify endogenous metabolomics compounds (EMCs) associated with 4HCY formation clearance (ratio of 4HCY/CY AUC) using global metabolomics. Patients who undergo hematopoietic cell transplantation receiving post-transplant CY (PT-CY) were enrolled, cohort 1 (n = 26) and cohort 2 (n = 25) donating longitudinal blood samples before they started HCT (pre-HCT), before infusion of the donor allograft (pre-graft), before the first dose of PT-CY (pre-CY), and 24 h after the first dose of PT-CY (24-h post-CY), which is also immediately before the second dose of CY. A total of 512 and 498 EMCs were quantitated in two cohorts, respectively. Both univariate linear regression with false discovery rate (FDR), and pathway enrichment analyses using a global association test were performed. At the pre-CY time point, no EMCs were associated at FDR less than 0.1. At pre-HCT, cohort 1 had one EMC (levoglucosan) survive the FDR threshold. At pre-graft, cohort 1 and cohort 2 had 20 and 13 EMCs, respectively, exhibiting unadjusted p values less than 0.05, with the only EMCs having an FDR less than 0.1 being two unknown EMCs. At 24-h post-CY, there were three EMCs, two ketones, and threitol, at FDR less than 0.1 in cohort 2. These results demonstrate the potential of pharmacometabonomics, but future studies in larger samples are needed to optimize CY.

FIGURE 1

Study Design. Plasma EMC samples were obtained at obtained before or with the administration of the post‐transplant CY (PT‐CY) regimen is associated with the ratio of 4HCY/CY AUC. Gray boxes show the four longitudinal time‐points at which plasma EMC samples were obtained. The ratio of the 4HCY/CY AUC_0–48 h was measured after both of the two PT‐CY doses; the AUCs are filled with dots or stripes. The HCT conditioning regimen is administered before HCT day −1, the allogeneic graft infusion occurs on HCT day 0, and the PT‐CY doses are administered on HCT day +3 and +4 (72 and 96 h, respectively, after infusion of the allogeneic graft). The EMC time points color coding corresponds to that in Figure 2. 4HCY, 4‐hydroxycyclophosphamide; AUC, area under the curve; AUC0–48 h, area under the curve from zero to 48 h; EMC, endogenous metabolomics compound; HCT, hematopoietic cell transplantation; PT‐CY, post‐transplant cyclophosphamide

FIGURE 2

Change in plasma EMCs from before post‐transplant CY administration (purple, blue, and teal dots) to after administration of the first post‐transplant CY dose (yellow dots). Principal Component Analysis showing differences across time points within cohorts. The time points color coding corresponds to that in Figure 1. CY, cyclophosphamid e, administered as post‐transplant cyclophosphamide ; TX, hematopoietic cell transplant