Plasma and cerebrospinal fluid pharmacokinetics of the DNA methyltransferase inhibitor, 5-azacytidine, alone and with inulin, in nonhuman primate models

Abstract

Epigenetic modifiers are being investigated for a number of CNS malignancies as tumor-associated mutations such as Isocitrate dehydrogenase mutations (IDH1/IDH2) and H3K27M mutations, which result in aberrant signaling, are identified. We evaluated the CNS exposure of the DNA methyltransferase inhibitor, 5-azacytidine (5-AZA), in pre-clinical nonhuman primate (NHP) models to inform its clinical development for CNS tumors. 5-AZA and 5-AZA+Inulin pharmacokinetics (PK) were evaluated in non-human primates (NHP) (n=10) following systemic (intravenous) and intrathecal [intraventricular (IT-V), intralumbar (IT-L), and cisternal (IT-C)] administration. Plasma, cerebrospinal fluid (CSF), cortical extracellular fluid (ECF), and tissues were collected. 5-AZA levels were quantified via an uHPLC-MS/MS assay and inulin via ELISA. PK parameters were calculated using non-compartmental methods. After IV administration, minimal plasma exposure [Area Under the Curve (AUC) range: 2.4-3.2 hr*uM] and negligible CSF exposure were noted. CSF exposure was notably higher after intraventricular administration (AUC_INF 1234.6-5368.4 hr*uM) compared to intra-lumbar administration (AUC_INF 7.5-19.3 hr*uM). CSF clearance (CL) after intrathecal administration exceeded the mean Inulin CSF flow rate of 0.018 ml/min + 0.003 as determined by inulin IT-V administration. 5-AZA IT-V administration with inulin increased the 5-AZA CSF duration of exposure by 2.2-fold. IT-C administration yielded no quantifiable 5-AZA ECF concentrations, but resulted in quantifiable tissue levels. IT administration of 5-AZA is necessary to achieve adequate CNS exposure. IT administration results in pronounced and prolonged 5-AZA CSF exposure above the reported IC50 range for IDH-mutated glioma cell lines. Inulin administered with 5-AZA increased the duration of exposure for 5-AZA.