Activity of 2-fluoro-5-methylarabinofuranosyluracil against mouse leukemias sensitive to and resistant to 1-beta-D-arabinofuranosylcytosine

A new pyrimidine nucleoside, 2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil, previously has been shown to be active against the herpes group of viruses in vitro and in vivo. It is also active against mouse and human leukemic cells in culture and against mouse leukemias L1210, P388, and P815 in vivo. In contrast to other 1-beta-D-arabinofuranosylcytosine (ara-C) derivatives, 2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil, when given either i.p. or p.o., is highly active against lines of leukemias P815 and L1210 made resistant to ara-C. Against P815/ara-C and L1210/araC, it is more effective than is 5-azacytidine, a drug which has shown definite effectiveness in patients with acute leukemia whose disease has become resistant to ara-C. For these reasons, 2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil would seem to merit clinical trial in patients with acute nonlymphocytic leukemia whose disease has become resistant to ara-C.

C(2')-substituted purine nucleoside analogs. Interactions with adenosine deaminase and purine nucleoside phosphorylase and formation of analog nucleotides

Four C(2')-substituted 2'-deoxyadenosines were examined as substrates for human erythrocytic adenosine deaminase and for formation of intracellular nucleotide analogs in human erythrocytes, lymphocytes and murine Sarcoma 180 cells: 9-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl)adenine, 9-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)adenine, 9-(2'-azido-2'-deoxy-beta-D-ribofuranosyl)adenine (2'-N3-riboA) and 9-(2-azido-2'-deoxy-beta-D-arabinofuranosyl)adenine. All four adenosine analogs were substrates of human erythrocytic adenosine deaminase, but the corresponding inosine analogs (synthesized by the adenosine deaminase reaction) were highly resistant to cleavage by human erythrocytic purine nucleoside phosphorylase. Only 9-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl)hypoxanthine underwent very slow phosphorolysis, and no inhibition of inosine phosphorolysis was detected when a 30 microM concentration of any studied inosine analog was added to a reaction mixture containing 30 microM inosine (the Km concentration). Kinetic parameters were determined for the deamination of the adenosine analogs. The greatest affinity for adenosine deaminase was found with 2'-N3-ribo A (Ki = 2 microM), but the reaction velocity was highest with the F-substituted analogs. All four adenosine analogs formed triphosphate nucleotides after incubation with human erythrocytes, murine Sarcoma 180 cells, or human lymphocytes (tested only with the F analogs) in the presence of deoxycoformycin.

Incorporation of metabolites of 2'-fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine into deoxyribonucleic acid of neoplastic and normal mammalian tissues

The radioactivity of 14C-labeled 2'-fluoro-5-iodo-1-beta-D-arabinofuranosylcytosine ([2-14C]-FIAC), a new and potent antiherpetic agent, was shown previously to be incorporated into the DNA fractions of mammalian and neoplastic tissues. The present work was undertaken to learn the nature of the incorporated moieties. Enzyme degradation of highly purified DNA from the small intestine of mice treated with [2-14C]FIAC and analysis of the resulting nucleosides failed to reveal the presence of unchanged FIAC. Rather, three metabolites were found, namely, the 2'-fluoro-1-beta-D-arabinofuranosyl nucleosides of cytosine (FAC), thymine (FMAU) and 5-iodouracil (FIAU). Labeled metabolites of FIAC were also found in the DNA isolated from P815 leukemic cells in mice given [2-14C]FIAC. It is of interest to note that FMAU, FIAU and FAC are, like FIAC, potent antiherpetic agents.

Synthesis of 3-methylpseudouridine and 2'-deoxy-3-methyl-pseudouridine

The first chemical synthesis of 3-methyl-psi-uridine (5) and its 2'-deoxy analogue (9) has been achieved. psi-Uridine was trimethylsilylated and the crude product was treated with acetyl chloride, to give the 1-acetyl derivative (3). Crude 3 was methylated with dimethoxymethyldimethylamine and then saponified, to give crystalline 5 in 82% overall yield. Treatment of 5 with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane afforded the 3'5'-protected product, which was converted into the 2'O-[(imidazol-1-yl) thiocarbonyl] derivative 7. Reduction of 7 with tributyltin hydride followed by deblocking of the product gave crystalline 2'-deoxy-3-methyl-psi-uridine (9) in 35% yield form 5.

Evaluation of the antiherpetic activity of 2'-fluoro-5-iodo-ara-C in rabbit eyes and cell cultures

2-Fluoro-5-iodo-ara-C (FIAC), a new and potent drug, was tested for antiviral activity against several strains of herpes simplex virus (HSV), types 1 and 2. Effective dose-50% (ED-50) determinations for FIAC ranged from 0.023 to 0.51 muM for HSV-2. FIAC-treated cells did not exhibit any toxicity until the drug concentration was increased 2000-fold above the ED-50 level. Ocular herpetic keratitis in New Zealand white rabbits was treated with 1.0%, 0.1%, 0.01% FIAC beginning 3 days after inoculation wit HSV-1 (McKrae strain). Topical chemotherapy was administered five times per day for 7 consecutive days. After 4 days of treatment, corneal epithelial involvement, conjunctivitis, iritis, and clouding were not detectable in eyes receiving 1.0% FIAC. Toxic reactions were not observed in rabbit eyes treated with FIAC drug. HSV was not prevented from spreading into the central nervous system when topical FIAC therapy was initiated on day 3 after inoculation.

Differential activity of potential antiviral nucleoside analogs on herpes simplex virus-induced and human cellular thymidine kinases

Potential antiviral nucleoside analogs 1-beta-D-arabinofuranosylthymine, the 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-nucleosides of -5-methyluracil, -5-iodouracil, -5-methylcytosine, -5-iodocytosine, and -E-5-(2-bromovinyl)uracil, E-5-(2-bromovinyl)-2'-deoxyuridine, E-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil, and 9-(2-hydroxyethyoxymethyl)guanine were studied to compare their phosphorylation rates relative to thymidine by purified thymidine kinases from human and herpes simplex virus sources. Most of these analogs are capable of being phosphorylated by both human and viral enzymes. On the assumption that inhibition constants (Ki) reflect binding affinity, Ki values were determined for these analogs with the same thymidine kinases. In general, these analogs have a greater affinity for the viral enzymes. The amount of the analogs phosphorylated to the monophosphate form, which is presumably necessary to produce cytotoxic effects, was determined by the combined effects of phosphorylation rates and binding affinities. All of these analogs act as preferential substrates for the viral thymidine kinases at low concentrations, which may be one of the main reasons for their selective antiviral action.

Nucleosides. 114. 5'-O-Glucuronides of 5-fluorouridine and 5-fluorocytidine. Masked precursors of anticancer nucleosides

5'-O-Glucuronides of anticancer nucleosides, 5-fluorouridine and 5-fluorocytidine, were synthesized by three different methods. The best preparative procedure was the one starting from benzyl 5-O-(methyl 2', 3', 4'-tri-O-acetyl-beta-D-glucopyranosyluronate)-2,3-O-isopropylidene-beta-D-ribof uranoside (15) that was obtained almost quantitatively by condensation of benzyl 2,3-O-isopropylidene-beta-D-ribofuranoside (8) with methyl (2,3,4-tri-O-acetyl-alpha-D-glucopyranosyl bromide)uronate (2). After de-O-isopropylidenation of 15, the crystalline product, benzyl 5-O-(methyl 2', 3', 4'-tri-O-acetyl-beta-D-glucopyranosyluronate)-beta-D-ribofuranoside (16), was de-O-benzylated catalytically to 5-O-(methyl 2', 3', 4'-tri-O-acetyl-beta-glucopyranosyluronate)-D-ribofuranose (17). Compound 17 was acetylated to crystalline 5-O-(methyl 2',3',4'-tri-O-acteyl-beta-D-glucopyranosyluronate)-1,2,3-tri-O-acetyl-beta-D-ribofuranose (18) and condensed with trimethylsilylated 5-fluorouracil of 5-fluorocytosine in the presence of SnCl4 to afford the corresponding protected nucleosides 5 and 19 in good yields. Saponification of these compounds gave 5'-O-beta-D-glucuronides of 5-fluorouridine and 5-fluorocytidine (20 and 21) isolated as their crystalline N salts. These glucuronides were substrates of both bacterial and bovine beta-glucuronidase. They were, as expected, much less toxic against several leukemia cell lines in tissue culture.

Nucleosides. 116. 1-(beta-D-Xylofuranosyl)-5-fluorocytosines with a leaving group on the 3' position. Potential double-barreled masked precursors of anticancer nucleosides

Syntheses of five pairs of cytosine and 5-fluorocytosinexylofuranosyl nucleosides in which the 3'-hydroxyl group is replaced by Cl, Br, OMs, or OTs are described. Those xylosyl nucleosides with a good leaving group at the 3' position exhibit good inhibitory activity against L5178Y and P815 mouse leukemic cells in vitro at rather low concentrations, and like that of ara-C this cytotoxicity is reversed by 2'-deoxycytidine but not by thymidine. Xylosylcytosines are not active against ara-C resistant lines of L5178Y and P815 cells; however, the corresponding 5-fluorocytosine analogues exhibit significant cytotoxicity against these ara-C resistant leukemic cell lines, and this activity is reversed by thmidine but not by deoxycytidine. These data support the "double-barreled" masked precursor hypothesis in that xylosyl-5-fluorocytosines substituted at the 3' position by a good leaving group exhibit activity akin to that of ara-C in the ara-C sensitive lines, while these nucleosides act as 5-fluoropyrimidines in the ara-C resistant lines.

2'-fluoro-5-iodo-aracytosine, a potent and selective anti-herpesvirus agent

A newly synthesized pyrimidine analog, 2'-fluoro-5-iodo-aracytosine (FIAC), suppressed by 90% the replication of various strains of herpes simplex virus types 1 and 2 at concentrations of 0.0025 to 0.0126 microM. Cytotoxicity was minimal, as determined by trypan blue dye exclusion with norman Vero, WI-38, and NC-37 cell proliferation; the 50% inhibitory dose was 4 to 10 microM in a 4-day assay. When compared with other antiviral drugs, FIAC was active at much lower concentrations than arabinosylcytosine, iododeoxyuridine, and arabinosyladenine. It was slightly more active against herpes simplex virus type 1 than acycloquanosine and slightly more toxic to normal cells. FIAC was about 8,000 times more active against the replication of wild-type herpes simplex virus type 1 than against a mutant strain lacking the expression of virus-specified thymidine kinase. Since FIAC appears to be preferentially phosphorylated by the viral enzyme, this is probably responsible, at least in part, for the selectivity of its antiviral actions. Although FIAC appears to be an arabinosylcytosine analog, its antiviral activity was not reversed by deoxycytidine. The minimal cytotoxicity exhibited by FIAC for normal cells, however, was reversed by equimolar concentrations of deoxycytidine. Thymidine, which reversed the antiviral activity, was effective only when used in great excess.

Solitary toy play and time out: a family treatment package for children with aggressive and oppositional behavior

The behavior of four boys, 5 to 8 years of age, who were referred for a number of oppositional, rule violating, and aggressive behaviors, was assessed by direct observation and parent reports. Following baseline measurement, several interventions were successively applied to each child's behavior. Use of a social play contract to reduce problem behaviors by teaching appropriate social behaviors resulted either in no improvement or in worsening of the problem behaviors in observations made when the contract was not in effect. Changing the contract behavior to solitary toy play resulted in reduced oppositional behavior during the observation sessions, fewer reports from the parents of low-rate problem behaviors, and improvements in the parents' attitudes toward the children. However, these changes during the observation sessions were short-lived, because the data on these measures began to show a reversal during later sessions. Inclusion of a time-out contingency with the solitary play contract recovered the earlier improvements in the children's behavior during observation sessions and the parents' reports. These results gave support to the view that for children whose behavior is severely oppositional and aggressive, a treatment approach emphasizing productive, solitary behaviors may be superior to one stressing appropriate social interaction. However, a combined strategy of reinforcement for solitary play and punishment for problem behaviors appears necessary to ensure more durable treatment effects.

Metabolism and effects of 5-(beta-D-ribofuranosyl)isocytosine in P815 cells

5-(beta-D-Ribofuranosyl)isocytosine (psi l Cyd), a C-nucleoside, has been shown to be active against P815 leukemia in mice. In P815 cells treated with [2-14C]psi l Cyd, we have detected radioactivity in nucleotide fractions and in RNA and DNA. Degradation to nucleosides of the labeled triphosphate nucleotide fraction and of RNA showed that the radioactivity present was chromatographically identical to psi l Cyd. Half-saturation concentrations for the incorporation of [2-14C]psi l Cyd into the triphosphate nucleotide fraction and into RNA and DNA were 370, 280, and 94 microgram/ml, respectively, which were greater than 100-fold higher than those for tritiated cytidine. The incorporation of psi l Cyd was competitively inhibited by cytidine. Phosphorylation and incorporation of psi l Cyd into nucleic acids of P815 cells and of a P815 subline resistant to 1-beta-D-arabinofuranosylcytosine are about 2- to 20-fold higher than in P815 sublines resistant to psi l Cyd or to both 5-azacytidine and 1-beta-D-arabinofuranosylcytosine. These data suggest that the phosphorylation of psi l Cyd and possibly its incorporation into nucleic acids are essential for therapeutic activity in P815 leukemias. In vitro metabolic studies also suggest that psi l Cyd and 5-azacytidine are cross-resistant and that P815 cells resistant to psi l Cyd are collaterally sensitive to 1-beta-D-arabinofuranosylcytosine. These predictions were confirmed by therapeutic experiments carried out in mice bearing P815 leukemias.

Nucleosides. 110. Synthesis and antiherpes virus activity of some 2'-fluoro-2'-deoxyarabinofuranosylpyrimidine nucleosides

A series of 5-substituted 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)cytosines 7a-d and their corresponding uracils 9a-d,f were prepared by condensation of 3-O-acetyl-5-O-benzoyl-2-deoxy-2-fluoro-D-arabinosyl bromide (5) with appropriately trimethylsilylated pyrimidines followed by saponification of the protected nucleosides 6 or 8. 1-(2-Deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (7e) was obtained by iodination of 7a. Iodination of 8a followed by removal of the protecting acyl-protecting groups afforded the 5-iodo nucleoside 9e. Several of these 2'-fluoro-substituted nucleosides completely obviated replication of herpes simplex virus type 1 (HSV-1) in monolayers of Vero cells at concentrations of 10-100 microgram/mL. The 5-iodocytosine analogue 7e was the most effective, showing 99.5% suppression of viral replication even at concentrations of 0.1 microgram/mL. The cytotoxicity of 7e to L5178Y or P815 cells in culture was minimal. A comparison of the efficacy of 7e against HSV-1 with other known nucleoside antiviral agents indicates that further in vitro and in vivo evaluation of 7e is warranted.

Nucleosides. CVI. Syntheses of 1-N-methyl-5-(beta-D-ribofuranosyl)uracil (1-N-methyl-phi-uridine) and its identity with a metabolite elaborated by Streptomyces platensis var. clarensis

Very recently, 1-N-methyl-psi-uridine was isolated from the culture filtrate of Streptomyces platensis var. clarensis along with an antibacterial and antiviral antibiotic, U-44590. We achieved chemical syntheses of 1-N-methyl-psi-uridine by selective methylation of psi-uridine in two different routes and established the identity of the synthetic nucleoside with the natural product.

Nucleosides. 102. Synthesis of some 3'-deoxy-3'-substituted arabinofuranosylpyrimidine nucleosides

The synthesis of some 3'-deoxy-3'-substituted arabinofuranosylcytosine (4a-d) and uracil (7a-d, 8a-d, X =Br, I, N3, SCN) nucleosides was accomplished by treatment of the requisite 2',3'-anhydrolyxofuranosylpyrimidine nucleoside (5,6a,b) with the appropriate ammonium salt in refluxing ethanol. Cleavage of the oxirane ring provided the desired 3'-deoxy-3'-substituted pyrimidine nucleosides (4a-d, 7a-d, and 8a-d). In vitro screening of compounds 4a-d, and 7a-d, with L5178Y cells in culture showed no significant inhibitory properties.