Antitumor activity of 2-fluoro-2'-deoxyadenosine against tumors that express Escherichia coli purine nucleoside phosphorylase.
ABSTRACT The selective expression of Escherichia coli purine nucleoside phosphorylase (PNP) in solid tumors has been successfully used to activate two purine nucleoside analogs [9-(2-deoxy-beta-D-ribofuranosyl)-6-methylpurine (MeP-dR) and 9-beta-D-arabinofuranosyl-2-fluoroadenine (F-araA)] resulting in lasting tumor regressions and cures. E. coli PNP also cleaves 2-fluoro-2'-deoxyadenosine (F-dAdo) to 2-F-adenine, which is the toxic purine analog liberated from F-araA that has high bystander activity and is active against nonproliferating tumor cells. As F-dAdo is 3000 times better than F-araA as a substrate for E. coli PNP, we have evaluated its antitumor activity against D54 gliomas that express E. coli PNP and have characterized its in vivo metabolism in order to better understand its mechanism of action with respect to the other two agents. Like MeP-dR and F-araA-5'-monophosphate (F-araAMP, a prodrug of F-araA), treatment of mice bearing D54 tumors that express E. coli PNP with F-dAdo resulted in excellent antitumor activity. Although F-dAdo was as active as MeP-dR and better than F-araAMP, it was not dramatically better than either compound because of its short plasma half-life and the limited activation of F-adenine to toxic metabolites. Regardless, these results indicated that F-dAdo was also an excellent prodrug for use with gene vectors that deliver E. coli PNP to tumor cells.
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ABSTRACT: Outcome of patients with relapsed acute myeloid leukemia (AML) remains unsatisfactory. Clofarabine is a nucleoside analog with activity in adult AML. Combinations with cytarabine in AML are feasible and effective. Idarubicin is another active AML drug, which has not yet been tested with clofarabine. The authors therefore designed a phase I study of clofarabine +/- cytarabine, plus idarubicin. Patients with primary refractory or first-relapse AML were assigned to either clofarabine plus idarubicin (CI) if previously exposed to cytarabine with a response lasting <12 months, or clofarabine and idarubicin plus cytarabine (CIA) for responses > or = 12 months, or if never exposed to cytarabine. A standard "3 + 3" phase 1 design was followed to define maximum tolerated dose (MTD). Forty-four patients were treated (23 CI; 21 CIA). Dose-limiting toxicities were hyperbilirubinemia and hepatic transaminase elevations for CI-treated patients in addition to mucositis and diarrhea for CIA-treated patients. MTD for CI was clofarabine 22.5 mg/m(2) intravenously daily x 5 and idarubicin 10 mg/m(2) intravenously daily x 3. MTD for CIA was clofarabine 22.5 mg/m(2) intravenously x 5, idarubicin 6 mg/m(2) intravenously x 3, and cytarabine 0.75 g/m(2) intravenously x 5 days. A phase 2 randomized trial is in process to compare activity between treatment arms.Cancer 09/2008; 113(8):2090-6. · 4.77 Impact Factor