In vitro inhibition of human nucleoside transporters and uptake of azacitidine by an isocitrate dehydrogenase-2 inhibitor enasidenib and its metabolite AGI-16903

Abstract

1. The present study investigated inhibitory effects of enasidenib and its metabolite AGI-16903 on (a) recombinant human nucleoside transporters (hNTs) in hNT-producing Xenopus laevis oocytes, and (b) azacitidine uptake in a normal B-lymphoblast peripheral blood cell line (PBC) and acute myeloid leukemia (AML) cell lines.

2. Enasidenib inhibited hENT1, hENT2, hENT3, and hENT4 in oocytes with IC₅₀ values of 7, 63, 27, and 76 μM, respectively, but exhibited little inhibition of hCNT1-3. AGI-16903 exhibited little inhibition of any hNT produced in oocytes.

3. Azacitidine uptake was more than 2-fold higher in AML cells than in PBC. Enasidenib inhibited azacitidine uptake into OCI-AML2, TF-1 and PBC cells in a concentration-dependent manner with IC₅₀ values of 0.27, 1.7, and 1.0 µM in sodium-containing transport medium, respectively.

4. IC₅₀ values shifted approximately 100-fold higher when human plasma was used as the incubation medium (27 µM in OCI-AML2, 162 µM in TF-1, and 129 µM in PBC), likely due to high human plasma protein binding of enasidenib (98.5% bound).

5. Although enasidenib inhibits hENTs and azacitidine uptake in vitro, plasma proteins attenuate this inhibitory effect, likely resulting in no meaningful in vivo effects in humans.

Keywords:

• Acute myeloid leukemia
• azacitidine
• enasidenib
• nucleoside transporter
• isocitrate dehydrogenase-2 inhibitor

Disclosure statement

No potential conflict of interest was reported by the authors.