Nucleoside conjugates as potential antitumor agents. 3. Synthesis and antitumor activity of 1-(.beta.-D-arabinofuranosyl)cytosine conjugates of corticosteroids

Abstract

Six 5'-(steroid-21-phosphoryl)-1-(beta-D-arabinofuranosyl)cytosines have been prepared and evaluated against L1210 lymphoid leukemia in culture and in mice (C3D2F1/J). These include the ara-C conjugates of 11-deoxycorticosterone (5a), corticosterone (5b), cortexolone (5c), fludrocortisone (5d), 6 alpha-methylprednisolone (5e), and dexamethasone (5f). When the optimum dosage of ara-C [38 (mumol/kg)/day X 5] was given to mice bearing L1210, the ILS value found was 89%. A simple mixture of each steroid and ara-C gave ILS values that were on the whole significantly less than that of the parent nucleoside. However, of six conjugates, all but two (5d and 5f) were more active than ara-C at their optimal doses. Both corticosterone- (5b) and cortexolone-p-ara-C (5c) were especially effective at the respective optimal doses of 76.7 and 115 (mumol/kg)/day X 5. These gave ILS values of 200% each. All of the conjugates were demonstrated to be enzymatically hydrolyzed to the corresponding steroid and ara-CMP, and the latter was further shown to be hydrolyzed to ara-C by phosphodiesterase I, 5'-nucleotidase, and acid phosphatase. However, they were shown to be resistant to hydrolysis by alkaline phosphatase.