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

BACKGROUND

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 preclinical nonhuman primate (NHP) models to inform its clinical development for CNS tumors.

METHODS

5-AZA and 5-AZA+Inulin pharmacokinetics (PK) were evaluated in NHPs ( = 10) following systemic (intravenous [IV]) 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 ultra-high-performance liquid chromatography with tandem mass spectrometric detection assay and inulin via ELISA. PK parameters were calculated using noncompartmental methods.

RESULTS

After IV administration, minimal plasma exposure (area under the curve [AUC] range: 2.4-3.2 hµM) and negligible CSF exposure were noted. CSF exposure was notably higher after IT-V administration (AUC 1234.6-5368.4 hµM) compared to IT-L administration (AUC 7.5-19.3 h*µM). CSF clearance after IT administration exceeded the mean inulin CSF flow rate of 0.018 ± 0.003 ml/min 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.

CONCLUSIONS

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 IC range for IDH-mutated glioma cell lines. Inulin administered with 5-AZA increased the duration of exposure for 5-AZA.