Nitrosoureidonucleosides

Antiproliferative and protein kinase binding activities of Some N6, 5'-bis-ureido 5'-amino-5'-deoxyadenosine derivatives

Two novel N(6),5'-bis-ureido 5'-amino-5'-deoxyadenosine derivatives are shown to inhibit tumor cell growth in the NCI 60 human tumor cell panel. Compounds 2c and 2d exhibited GI(50) values of 1-6 microM in 35 and 14 cell lines, respectively. Compound 2c was shown to selectively inhibit binding of protein kinases to immobilized ATP-binding site ligands via a competitive binding assay (11 of 353 protein kinases inhibited by > or =30% at 10 microM compound concentration). Enzyme inhibition assays revealed modest inhibition for PAK4 and FMS (21 and 17%, respectively). A brief SAR study suggests that a 2'-O-TBDMS is necessary for antiproliferative activity.

Design, synthesis, and antiviral evaluation of some 3'-carboxymethyl-3'-deoxyadenosine derivatives

3'-Carboxymethyl-3'-deoxyadenosine derivatives were prepared from 2'-O-TBDMS-3'-[(ethoxycarbonyl)methyl]-3'-deoxyadenosine (1) via simple and efficient procedures. Conversion of 1 to its 5'-azido-5'-deoxy derivative 5 was accomplished via a novel one-pot method employing 5'-activation (TosCl) followed by efficient nucleophilic displacement with tetramethylguanidinium azide. Compound 5 was converted to 5'-[(N-methylcarbamoyl)amino] derivative 8 via one-pot reduction/acylation employing H(2)/Pd-C followed by treatment with p-nitrophenyl N-methylcarbamate. N(6)-phenylcarbamoyl groups were introduced by treatment with phenylisocyanate, and an efficient new method for lactonization of 2'-O-TBDMS-3'-[(ethoxycarbonyl)methyl]-3'-deoxyadenosines to give corresponding 2',3'-lactones was also developed. Target compounds were evaluated for anti-HIV and anti-HIV integrase activities, but were not active at the concentrations tested.

Molecular basis for thymidine modulation of the efficacy and toxicity of alkylating agents

The antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in mice previously was shown to be markedly enhanced by co-administration of thymidine. We have examined the cellular mechanisms underlying the augmentation effect of thymidine. It was found that thymidine did not increase the cytotoxicity of BCNU for B16/F10 melanoma or L1210 leukemia cells in vitro. Instead, thymidine appeared to augment the activity of tumor-specific cytotoxic T-cells in tumor-bearing mice, which specifically rejected a secondary challenge with the B16/F10 tumor. Thus, development of an antitumor immune response is facilitated by thymidine in BCNU-induced immunosuppressed mice. These preclinical studies suggested that combination therapy with alkylating agents and thymidine may be a more efficacious and less toxic anticancer therapy. The potential efficacy of the sequential administration of dacarbazine (DTIC), BCNU, and thymidine in patients with advanced malignant melanoma was investigated. As predicted from animal studies, sequential administration of DTIC, BCNU, and thymidine is a relatively nontoxic therapy for metastatic melanoma. This treatment induced durable responses in up to 35% of patients, and hence is superior to many commonly used toxic combination chemotherapies. The mechanism of action, although not well characterized, is thought to be mediated through protection of the cellular immune process, as well as organ function, from alkylating agent toxicity through modulation of DNA repair enzymes such as O(6)-alkylguanine-DNA alkyltransferase in normal tissue. Thus, thymidine is a biomodulator, which not only protects patients from hematologic, pulmonary, and hepatic toxicities associated with DTIC and BCNU chemotherapy, but also potentiates therapeutic efficacy.

Preparation of N'-substituted anilino-N-methyl-N'nitrosoureas as candidate antitumor agents

Various N'-substituted anilino-N-methyl-N'-nitrosoureas(2a-n) were easily prepared from the reaction of substituted phenylhydrazines (3-, 4-CH3, 3-, 4-OCH3, 3-, 4-F, 3-, 4-Cl, 4-Br, 2-, 3-, 4-NO2, 2, 4-(NO2)2 with methyl isocyanate, followed by the nitrosation with 99% HCOOH and dry sodium nitrite powder. Surprisingly of these series of analogus, the anilino-nitrosoureas substituted with electron-withdrawing nitro groups (2k-n) showed significantly low ED50 values of 1.4-3.4 micrograms/ml. In addition, none of these compounds substituted with electron-donating groups exhibited cytotoxicities.

In the search for new anticancer drugs. XXIII: Exploration of a predictive design for anticancer drugs of carbohydrates containing N-nitrosochloroethylamino, N-nitrosomethyl, and N-nitrosoaminoxyl components

The spin-labeled glucose nitrosoureas 13-16, streptozotocin (18), chlorozotocin (31), streptozotocin analogues of galactosyl 24 and mannosyl 28, and their tetra-O-acetyl derivatives 25 and 29, MCNU (Cymerin, 34), and glucamine (21) were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 13-16, 18, 24, 28, 31, and 34 possessed activities ranging from 33 to 603% increase in life span (%ILS), whereas 21, 25, and 29 were inactive (%ILS = 9 to 10). All CD2F1 male mice treated with the most active compounds (13, 14, and 34) at 20 mg/kg were alive after 30 days, whereas all mice treated with the clinical drug streptozotocin (18) and clinically tested chlorozotocin (31) succumbed. Compounds 13-16, 18, 31, and 34 were further evaluated for their antineoplastic activity against lymphoid leukemia L1210. Compounds 13 and 34 on day 60 exhibited %ILS values of 557 and 713, respectively, as compared with %ILS values of 646 and 713 for CCNU (1) and the spin-labeled SLCNU (3), respectively. The lipophilicities of 13-16, 18, 21, 24, 25, 28, 29, 31, and 34 were determined using EPR and/or UV methods. A predictive design pattern was observed, with the most active drug (34) possessing some hydrophobic property (log P = 1.24), followed by 13 (log P = 1.87) and 14 (log P = 1.81) as the more active drugs with higher hydrophobicity than 34. The clinical drugs streptozotocin (18) and chlorozotocin (31) were distinctly hydrophilic and less active. Finally, it was concluded that various scattered results of anticancer activity in the literature can be explained by a linear correlation of activities with lipophilicities.

Nitrosoureas from chemist to physician: classification and recent approaches to drug design

Molecular design of chemotherapeutic nitrosoureas is reviewed in the light of a chemical classification of N-(2-chloroethyl)-N-nitrosoureas (CNUs), particularly those recently introduced and earlier compounds tested in the clinic. Of the six categories, three are rather arbitrarily based on physicochemical properties: the original, lipid-soluble drugs, water-soluble sugar derivatives, and amides of intermediate character. Others deal with more complex drug designs incorporating antimetabolites (5-fluorouracil), steroids, redox delivery systems, or hypoxia-selective 2-nitroimidazoles. Current attempts to modify the standard 2-chloroethyl group, with implications for interstrand cross-linking of DNA, are considered. Two unfortunate factors influencing the choice of drugs for clinical trial have been prejudice from the physician and commercial interests. The latter requires no further comment, but a strong plea is made for recognition of the CNU group as one of comparatively few valuable tools for rational drug design requiring appropriate pharmacokinetic evaluation, rather than as a somewhat boring hallmark of repetitive chemists.

The effect of the nitrosourea analog of thymidine, 3'-[3-(2-chloroethyl)-3-nitrosoureido]-3'-deoxythymidine, on Escherichia coli thymidine kinase

Escherichia coli thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) is irreversibly inactivated by incubation with 3'-[3-(2-chloroethyl)-3-nitrosoureido]-3'-deoxythymidine (3'-CTNU). The inactivation of the enzyme followed first-order kinetics even after loss of 96% of the original activity. This indicates that the inactivation process is a one-kill phenomenon and not a generation of less active enzyme. The addition of a preincubated aqueous solution of 3'-CTNU to the enzyme reaction mixture did not inactivate the enzyme. ATP . Mg2+ but not thymidine protects the enzyme from inactivation by 3'-CTNU. The allosteric regulators, dTTP, dCTP and dCDP also afforded complete protection of the enzyme from inactivation by 3'-CTNU. These data indicate that the dimer form of the enzyme is completely resistant to inactivation by 3'-CTNU, but the monomer form of the enzyme is sensitive. The specificity of the protection is supported by the finding that neither ATP . Mg2+ nor thymidine protect yeast alcohol dehydrogenase from inactivation by this nitrosourea analog of thymidine.