Study on the Preparation and Antileukemic Activity of New Lipophilic 1-β-D-arabinofuranosylcytosine Derivatives

Abstract

Cytarabine (1-β-D-arabinofuranosylcytosine, Ara-C), isolated from a Caribbean sponge species Tethyacrypta, is the first antitumor drug from a marine resource. In 1980, the US Food and Drug Administration approved this drug for the treatment of different types of leukemia. This drug has a short plasma half-life, low stability, limited bioavailability, and severe side effects. To improve stability and bioavailability, we synthesized nine novel derivatives by blocking the cytarabine metabolic sites and improving lipophilicity. The cLogP values of the newly synthesized compounds were calculated. All the synthesized compounds were more lipophilic than cytarabine, resulting in membrane permeability and bioavailability improvement. The antitumor activities against leukemia cell line HL-60 were evaluated by using the MTT assay. The bioassay results revealed that the IC₅₀ values of compounds 5, 8 and 9 were 0.080, 0.090 and 0.057 μmol L⁻¹, respectively, which was similar with that of cytarabine (0.056 μmol L⁻¹). In comparison, compound 4 with a phosphate group at O5’ was inactive. Because phosphoester bonds are easily hydrolyzed by alkaline phosphatase and are commonly used in producing prodrug strategies, compound 4 might also be metabolized in vivo and generate compound 3 or even cytarabine through a multi-step reaction. Thus, compound 4 might be a promising compound to be developed as a prodrug.