In vitro and in vivo antiviral (RNA) evaluation of orotidine 5′-monophosphate decarboxylase inhibitors and analogues including 6-azauridine-5′-(ethyl methoxyalaninyl)phosphate (a 5′-monophosphate prodrug)

A series of 29 pyrimidines comprising analogues of 6-azauridine (e.g. 2- and 4-thio-6-azauridine), 6-substituted uridines (including several known inhibitors of orotidine 5′-monophosphate decarboxylase, ODCase, e.g. pyrazofurin), and 6-azauridine-5′-(ethyl methoxyalaninyl) phosphate (a potential prodrug of 6-AU-5′-MP) were synthesized and evaluated in vitro and in vivo against five RNA viruses: Japanese encephalitis (JE), yellow fever (YF), sandfly fever (SF), Punta Tora (PT) and Venezuelan equine encephalomyelitis (VEE) viruses. 2-Thio-6-azauridine demonstrated the best In vitro activity against all five viruses. However, in vivo activity was not observed in JE-, PT- and VEE-infected mice. The phosphate prodrug of 6-azauridine was significantly more effective than the parent compound in the PT virus mouse model. Optimum in vivo dose/route/schedule was determined for pyrazofurin in PT-virus-infected mice.

Synthesis and antiviral evaluation of analogs of adenosine-N1-oxide and 1-(Benzyloxy)adenosine

The activity of a series of compounds related to adenosine-N1-oxide (1) and 1-(benzyloxy)adenosine (42) against vaccinia virus has been determined both in vitro and in a vaccinia mouse tailpox model. Significant activities have been found both in vitro and in vivo for a number of the synthetic compounds.

Retinyl substituted-benzyl ethers. Inhibition of mammary carcinogenesis by retinyl 3,4,5-trimethoxybenzyl ether (RTMBE)

Recently, we reported that retinyl 2-propynyl ether (RPE) inhibits MNU-induced mammary cancer in rats and is less toxic than RME and retinyl acetate. The preparation and biological investigations of retinyl ethers have now been extended to retinyl substituted-benzyl ethers, some of which bind to cellular retinol-binding protein. In long-term (160-180 days) experiments, retinyl 3,4,5-trimethoxybenzyl ether (RTMBE) has been shown to be active against MNU-induced mammary cancer in Sprague-Dawley rats. In effectiveness, RTMBE is comparable, at least, to retinyl acetate; but, unlike retinyl acetate, RTMBE is comparatively non-toxic to rats and mice, is not converted enzymatically to retinol, and does not cause significant increases in retinyl palmitate concentrations in the liver. RTMBE reaches high concentrations in mammary tissue. Two of the four RTMBE congeners that were evaluated in 90 day studies were moderately effective in inhibiting mammary carcinogenesis.

Lipophilic antifolates as agents against opportunistic infections. 1. Agents superior to trimetrexate and piritrexim against Toxoplasma gondii and Pneumocystis carinii in in vitro evaluations

2,4-Diaminopteridines (21 compounds) and 2,4-diamino-5-methyl-5-deazapteridines (34 compounds) along with three 2,4-diamino-5-unsubstituted-5-deazapteridines and four 2,4-diaminoquinazolines, each with an aryl groups attached to the 6-position of the heterocyclic moiety through a two-atom bridge (either CH2NH, CH2N(CH3),CH2S, or CH2CH2), were synthesized and evaluated as inhibitors of the growth of Toxoplasma gondii in culture and as inhibitors of dihydrofolate reductase enzymes from T. gondii, Pneumocystis carinii, and rat liver. Exceptionally high levels of combined potency and selectivity as growth inhibitors of T. gondii and as inhibitors of the microbial enzymes relative to the mammalian enzyme were found among the 5-methyl-5-deazapteridines but not for the other heterocyclic types. Thirty of the 34 5-methyl-5-deaza compounds gave growth inhibition IC50 values lower than that of pyrimethamine (0.4 microM) with 14 compounds below 0.1 microM, values that compare favorably with those for piritrexim and trimetrexate (both near 0.02 microM). As inhibitors of T gondii DHFR, all but three of the 34 5-methyl-5-deaza compounds gave IC50 values in the order of magnitude with those of piritrexim (0.017 microM) and trimetrexate (0.010 microM), and 17 compounds of this group gave IC50 values versus P. carinii DHFR similarly comparable with those of piritrexim (0.031 microM) and trimetrexate (0.042 microM). Thirteen of these congeners gave both T. gondii growth inhibition and DHFR inhibition IC50 values of 0.10 microM or less, thus indicating facile penetration of the cell membrane. Eleven of these inhibitors of both T. gondii growth and DHFR have selectivity ratios (IC50 rat liver divided by IC50 T. gondii) of 5 or greater for the parasite DHFR. The highest selectivity ratio of nearly 100 belongs to the 5-methyl-5-deaza compound whose 6-substituent is CH2CH2C6H3(OCH3)2-2,5. This compound is over 10(3)-fold more selective for T. gondii DHFR than bridge homologue piritrexim (selectivity ratio 0.088), a compound now in clinical trials. The candidate with CH2NHC6H3(CH3)2-2,5 in the 6-position gave the highest P. carinii DHFR selectivity ratio of 4.0, which is about 60-fold more selective than trimetrexate (0.071) and 80-fold more selective than piritrexim (0.048) toward this enzyme. The 10 best compounds with respect to potency and selectivity includes six compounds bearing 2,5-disubstituted phenyl groups in the side chain (with little, if any, difference in effects of methyl, methoxy, or ethoxy), two side chains bearing 1-naphthyl groups, and two with 5,6,7,8-tetrahydro-1-naphthyl groups. Bridge groups represented in the 10 choice compounds are CH2NH, CH2N(CH3), CH2CH2, and CH2S. The high levels of both potency and selectivity among these agents suggest that in vivo studies now underway may lead to agents that could replace trimetrexate and piritrexim in treatment of toxoplasmosis and P. carinii pneumonia.

Synthesis and antineoplastic evaluation of alpha-substituted alkanesulfonates: analogues of clomesone

2-Chloroethyl (methylsulfonyl)methanesulfonate (clomesone) is highly effective against certain experimental neoplasma and is now undergoing initial clinical trials. Two groups of analogues have been prepared to explore further the anticancer activity of this type of sulfonates. The first group is comprised of several 2-chloroethyl sulfonates that have electron-attracting groups alpha to the sulfonate group; among these, the alpha-chloroethanesulfonate and the (trifluoromethyl)-methanesulfonate caused increases in lifespan of 45 and 72%, respectively, in tests against P388 leukemia in mice. The second group is comprised of several (methylsulfonyl)methanesulfonates that possess alkylating groups other than the 2-haloethyl groups. 2-Hydroxyethyl (methylsulfonyl)methanesulfonate was active against P388 leukemia (increases in lifespan, 66 and 94%), but was less effective than clomesone, which effects cures. The 3-chloropropyl and the propyl derivatives caused modest increases in lifespan. Therefore, several 2-chloroethyl alpha-substituted methanesulfonates are less effective against P388 leukemia than is the alpha-(methylsulfonyl) derivative (clomesone), and several substituted alkyl (methylsulfonyl)methanesulfonates are also less effective than is the 2-chloroethyl derivative (clomesone). The synthesis of clomesone was simplified to one operational step from methanesulfonyl chloride.

Terminal bifunctional retinoids. Synthesis and evaluations related to cancer chemopreventive activity

Retinoids that have two functional groups at the side-chain terminus have been synthesized. The two terminal functional groups are combinations of the carboxyl, carbethoxy, and N-(ethylamino)carbonyl groups. The synthesis route is based on the sodium amide catalyzed condensation of (E,E)-beta-ionylideneacetaldehyde with diethyl isopropylidenemalonate. Ethyl 14-carboxyretinoate (6), the initial bifunctional analogue, undergoes isomerization in unbuffered aqueous ethanol and reaches a state of equilibrium with ethyl 14-carboxy-13-cis-retinoate. Both of the possible amide-esters and amide-acids were obtained. The structures of the isomeric bifunctional analogues were established by studies of nuclear Overhauser effects. The bifunctional analogues induce differentiation of mouse embryonal carcinoma cells, and those analogues that have a free carboxyl group bind to cellular retinoic acid binding protein.

2-Chloroethyl (methylsulfonyl)methanesulfonate and related (methylsulfonyl)methanesulfonates. Antineoplastic activity in vivo

2-Haloethyl and ethyl (methylsulfonyl)methanesulfonates were prepared via sulfene intermediates. 2-Chloroethyl (methylsulfonyl)methanesulfonate is highly active against P388 leukemia in vivo; the majority of leukemic mice treated with this compound at 50 mg/kg per day, qd 1-5, survived more than 30 days and about 37% survived for more than 60 days. 2- Fluoroethyl (methylsulfonyl)methanesulfonate is also highly effective against P388 cells in vivo, but it is more toxic. Other (methylsulfonyl)methanesulfonate esters are more active than the analogous methanesulfonates and chloromethanesulfonates .

2-haloethylating agents for cancer chemotherapy. 2-haloethyl sulfonates

Because certain (2-chloroethyl)triazenes and (2-haloethyl)nitrosoureas have high antineoplastic activity, 2-chloroethyl and 2-fluoroethyl sulfonates were prepared to try to develop additional types of 2-haloethylating agents. In this initial study, it was demonstrated that antineoplastic activity much superior to that of the prototype, 2-chloroethyl methanesulfonate, could be found among 2-chloroethyl sulfonates. Among a variety of 2-chloroethyl alkane- and arenesulfonates, several substituted methanesulfonates displayed significant activity against P388 leukemia in mice; the chloromethanesulfonate showed high activity (T/C = 218%). None of the arenesulfonates were active in this test.

Synthesis of analogues of N-(2-chloroethyl)-N'-(trans-4-methylcyclohexyl)-N-nitrosourea for evaluation as anticancer agents

The superior activity of N-(2-chloroethyl)-N'-(trans-4-methylcyclohexyl)-N-nitrosourea (MeCCNU) against advanced murine Lewis lung carcinoma in comparisons with the cis form and other nitrosoureas prompted the synthesis of a number of MeCCNU analogues, including several cis-trans pairs. The methyl group was replaced by a variety of substituents (CO2H, CH2CO2H, CO2Me, CH2OAc, CH2Cl, OMe); the trans-3-methylcyclohexyl, cis-2-methyl-1,3-dithian-5-yl, cis- and trans-2-methyl-1,3-dithian-5-yl-tetraoxide, and 1-methylhexyl (open-chain) analogues were also prepared. Preliminary tests against murine leukemia L1210 revealed therapeutic indices (ED50/LD10) ranging from 0.26 to 0.79; all but three analogues effected 50% cure rates at nontoxic doses, the open-chain analogue being one of the least active. In terms of therapeutic index, diequatorial (trans-4) isomers were, with one exception, as active as or, in four of the eight examples, somewhat more active than the corresponding axial-equatorial (cis-4) isomers. In this series, four of the five 2-fluoroethyl analogues prepared were clearly inferior to the corresponding 2-chloroethyl analogues.