Orally bioavailable, indole-based nonpeptide GnRH receptor antagonists with high potency and functional activity

Stereospecific introduction of a methyl group to the indole-3-side chain enhanced activity in our tryptamine-derived series of GnRH receptor antagonists. Further improvements were achieved by variation of the bicyclic amino moiety of the tertiary amide and by adjustment of the tether length to a pyridine or pyridone terminus. These modifications culminated in analogue 24, which had oral activity in a rat model and acceptable oral bioavailability and half-life in dogs and monkeys.

Potent nonpeptide GnRH receptor antagonists derived from substituted indole-5-carboxamides and -acetamides bearing a pyridine side-chain terminus

A pyridine side-chain terminus has been incorporated into the indole-5-carboxamide and indole-5-acetamide series of GnRH antagonists. Potent activity was observed in binding and functional assays. Certain branched or cyclic tertiary amides were identified as preferred in each series. Alkylation of the side-chain secondary amine had generally unfavorable effects. Variations of the gem-dialkyl substituents in the indole-5-acetamide series were also investigated.

Substituted indole-5-carboxamides and -acetamides as potent nonpeptide GnRH receptor antagonists

The 2-aryltryptamine class of GnRH receptor antagonists has been modified to incorporate carboxamide and acetamide substituents at the indole 5-position. With either a phenol or methanesulfonamide terminus on the N-aralkyl side chain, potent binding affinity to the GnRH receptor was achieved. A functional assay for GnRH antagonism was even more sensitive to structural modification and revealed a strong preference for branched tertiary amides.

Structure-activity relationships of biphenyl tetrazoles as metallo-beta-lactamase inhibitors

Resistance to carbapenem antibiotics in gram-negative bacteria is due, in part, to expression of a wide spectrum metallo-beta-lactamase, which renders the drug inactive. Biphenyl tetrazoles containing 3-n-butyl-1-phenylpyrazole-5-carboxylates or the corresponding 5-ethyl esters were found to inhibit metallo-beta-lactamases as well as renal dehydropeptidase I to a lesser extent.

Potent and orally active angiotensin II receptor antagonists with equal affinity for human AT1 and AT2 subtypes

In order to block the effects induced by the interactions between angiotensin II (AII) and both AT1 and AT2 receptors, we have pursued the discovery of orally active non-peptide AII antagonists that exhibit potent and equal affinity for human AT1 and AT2 receptor subtypes. A series of previously prepared nanomolar (IC50) trisubstituted 1,2,4-triazolinone biphenyl-sulfonamide dual-acting AII antagonists has been modified at five different positions in order to increase AT2 binding affinity, maintain AT1 activity, and reduce the human adrenal AT2/AT1 potency ratio (IC50 ratio) from > or = 10. The targeted human adrenal potency ratio of < or = 1 was achieved with a number of compounds possessing an ethyl group at C5 of the triazolinone and a 3-fluoro substituent at the N4-biarylmethyl moiety. The most favored of these was compound 44 which exhibited subnanomolar potency at both the AT1 (rabbit aorta) and AT2 (rat midbrain) receptors, with a slight preference for the latter, and had a human adrenal AT2/AT1 IC50 ratio of 1. This tert-butyl sulfonylcarbamate with an N2-[2-bromo-5-(valerylamino)phenyl] substituent had excellent iv activity at 1 mg/kg (100% peak inhibition, > or = 4 h duration of action) and is orally active at 3 mg/kg with > 6 h duration of action in a conscious rat model. The present study shows that the NH of the amide on the N2-aryl moiety is not required for subnanomolar binding affinity to either receptor subtype, although a keto functionality at this position is essential for acceptable AT2 binding. Receptor-ligand binding interactions derived from the structure-activity relationships are discussed with respect to both receptor subtypes.

In vivo pharmacology of L-159,913, a new highly potent and selective nonpeptide angiotensin II receptor antagonist

The present study was designed to characterize the in vivo pharmacology of L-159,913 (4-[[2'-(N-benzoylsulfamoyl)biphenyl-4-yl]-5butyl-2,4-dihydr o-2- [2-(trifluoromethyl)phenyl]-3H-1,2,4-triazol-3-one); a potent All receptor antagonist. In normotensive rats, dogs, rhesus monkeys, and chimpanzees, L-159,913 inhibited All-induced elevations in blood pressure. In conscious rats, the relative potencies (ED50) were 0.51 mg/kg i.v. and 0.72 mg/kg p.o. Duration of action with single i.v. or p.o. doses exceeded 6 hr in rats. L-159,913 was 3 times less potent than losartan in rats and equipotent to losartan in monkeys. All induced elevation of plasma aldosterone in rats was also inhibited by L-159,913. L-159,913 was antihypertensive in high renin hypertensive rats (aortic coarctation). The maximum hypotensive response to an acute dose of L-159,913 (10 mg/kg, po) was equal to that of enalaprilat (0.3 mg/kg, iv) in this renin dependent animal model. In conscious normotensive dogs, L-159,913 had a moderate diuretic, natriuretic and kaliuretic response with no effect on glomerular filtration rate, effective renal plasma flow or filtration fraction, suggesting a tubular site of action. L-159,913 is a selective and potent All receptor antagonist with good oral activity, long duration of action and antihypertensive efficacy.

Triazolinone biphenylsulfonamides as angiotensin II receptor antagonists with high affinity for both the AT1 and AT2 subtypes

Angiotensin II (AII), the endogenous peptide ligand of the AII receptor, has equivalent high affinity for both the AT1 and AT2 receptor subtypes while most of the reported nonpeptide AII antagonists are AT1-selective. In an effort to identify dual AT1/AT2 nonpeptide AII antagonists, we have pursued modifications of previously prepared trisubstituted 1,2,4-triazolinone biphenylsulfonamides which exhibited subnanomolar in vitro AT1 (rabbit aorta) AII antagonism and AT2 (rat midbrain) IC50 values of < 40 nM. Present results show that a suitable amide (or reversed amide) side chain appropriately positioned on the N2-aryl group of these compounds gave > 15-fold enhancement in AT2 binding affinity without sacrificing nanomolar AT1 potency (IC50). This added amide, combined with an appropriate choice of the N-substituent on the sulfonamide and the ortho substituent on the N2-aryl group, led to an analogue (46, L-163,-007) which exhibited subnanomolar AT1 binding affinity and an AT2/AT1 IC50 ratio of 3. This compound showed excellent iv activity at 1 mg/kg and oral efficacy at 3 mg/kg with > 6 h duration in a conscious rat model. Available data suggest that the newly introduced amide side chain, mandatory for low nanomolar binding affinity at the AT2 receptor, is well-tolerated by the AT1 receptor and has minimal effect on the in vivo properties of these molecules.

Triazolinone biphenylsulfonamide derivatives as orally active angiotensin II antagonists with potent AT1 receptor affinity and enhanced AT2 affinity

Several series of 2,4-dihydro-2,4,5-trisubstituted-3H-1,2,4-triazol-3-ones with acidic sulfonamide replacements of tetrazole at the 2'-position of the biphenyl-4-ylmethyl side chain at N4 were prepared and tested as angiotensin II (AII) antagonists. Preferred substituents on the triazolinone ring were n-butyl at C5 and 2-(trifluoromethyl)phenyl at N2. Subnanomolar IC50 values at the AT1 receptor subtype were observed for a variety of acylsulfonamides, including aroyl, heteroaroyl, and cycloalkylcarbonyl derivatives. Certain other acidic sulfonamides, such as sulfonylcarbamates and disulfimides also displayed high affinity for the AT1 receptor. In addition, AT2 binding for some of these compounds was increased by as much as 1000-fold over the corresponding tetrazole (e.g., AT2 IC50 17 nM for the tert-butyl sulfonylcarbamate 92). When evaluated for inhibition of the AII pressor response, the benchmark benzoylsulfonamide 9 (L-159,913) was efficacious in several species and was superior to losartan (1a) in conscious rhesus monkeys. Several subsequent analogues, including the 2-chlorobenzoyl (18), (3-chlorothiophene-2-yl)carbonyl (51), ((S)-2,2-dimethylcyclopropyl)carbonyl (80), and tert-butoxycarbonyl (92) derivatives, were highly effective in rats, surpassing 9 and losartan in duration of action and/or potency. Compound 18 (L-162,223) displayed very prolonged AII antagonism in the rat model (> 24 h at 1 mg/kg iv). At 1 mg/kg po in rats, 18 and 92 (L-162,234) produced 85-87% peak inhibition of the AII pressor response with duration exceeding 6 h. The identification of triazolinone-based sulfonamide derivatives combining high AT1 affinity, considerably enhanced AT2 potency, and favorable in vivo properties provides insights relevant to the design of dual AT1/AT2 receptor antagonists.

Nonpeptide angiotensin II antagonists derived from 1H-pyrazole-5-carboxylates and 4-aryl-1H-imidazole-5-carboxylates

Two series of potential angiotensin II antagonists derived from carboxyl-functionalized "diazole" heterocycles have been prepared and evaluated. Initially, a limited investigation of 4-arylimidazole-5-carboxylates led to 2-n-butyl-4-(2-chlorophenyl)-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-y l] methyl]-1H-imidazole-5-carboxylic acid (12b), which was found to be a highly potent antagonist of the rabbit aorta AT1 receptor (IC50 0.55 nM). In conscious, normotensive rats, 12b at 0.1 mg/kg iv inhibited the pressor response to AII by 88%, with a duration of > 6 h. More extensively studied was an isosteric series of 3-alkyl-4-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-pyrazole -5- carboxylates bearing aryl, alkyl, or aralkyl substituents at N1. These compounds were available in highly regioselective fashion via condensation of a substituted hydrazine hydrochloride with a 2-(methoxyimino)-4-oxoalkanoate intermediate. In vitro, the most potent pyrazolecarboxylic acids had n-butyl at C3 and were substituted at N1 by such groups as 2,6-dichlorophenyl (19h), 2-(trifluoromethyl)phenyl (19k), benzyl (19t), and phenethyl (19u), all with IC50 values of 0.18-0.24 nM. Although less potent in the receptor assay, 3-n-propylpyrazolecarboxylic acids were at least as effective as their butyl counterparts in vivo. Several of the pyrazolecarboxylic acid derivatives demonstrated potent, long-lasting oral activity in rats. At 1 mg/kg po, the 1-benzyl-3-butyl (19t), 1-(2,6-dichlorophenyl)-3-propyl (19v), 3-propyl-1-(2,2,2-trifluoroethyl) (19y), and 1-benzyl-3-propyl (19z) analogues all gave > or = 75% inhibition of the AII pressor response in the rat model, with duration of action > 23 h.

Triazolinones as nonpeptide angiotensin II antagonists. 1. Synthesis and evaluation of potent 2,4,5-trisubstituted triazolinones

A series of 2,4-dihydro-2,4,5-trisubstituted-3H-1,2,4-triazol-3-ones was prepared via several synthetic routes and evaluated as AII receptor antagonists in vitro and in vivo. The preferred compounds contained a [2'-(5-tetrazolyl)biphenyl-4-yl]methyl side chain at N4 and an n-butyl group at C5. A number of these bearing an alkyl or aralkyl substituent at N2 showed in vitro potency in the nanomolar range (rabbit aorta membrane receptor), and several of these, e.g., the 2,2-dimethyl-1-propyl analogue (54, IC50 = 2.1 nM), effectively blocked the AII pressor response in conscious rats with significant duration (2.5 h at 1 mg/kg orally for 54). Among analogues possessing aryl substituents at N2, ortho substitution on the phenyl moiety resulted in several derivatives with in vitro potency in the low nanomolar range. One of these, featuring a 2-(trifluoromethyl)phenyl substituent at N2 (25, IC50 = 1.2 nM), was effective at 1 mg/kg orally in the rat model, with a duration of > 6 h. Implications for hydrophobic and hydrogen-bonding interactions with the AT1 receptor are discussed.

Nonpeptide angiotensin II antagonists derived from 4H-1,2,4-triazoles and 3H-imidazo[1,2-b][1,2,4]triazoles

By a variety of synthetic routes, we have synthesized a series of 3,4,5-trisubstituted 4H-1,2,4-triazoles and a related series of 3H-imidazo[1,2-b][1,2,4]triazoles and evaluated them in vitro and in vivo as angiotensin II (AII) antagonists. Principal efforts focused on triazoles bearing an n-alkyl substitutent at C3 and a 4-[(2-carboxybenzoyl)amino]benzyl, (2'-carboxybiphenyl-4-yl)methyl, or [2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl side chain at N4. Among numerous variations at C5, benzylthio groups gave the best potency. Particularly noteworthy was 3-n-butyl-5-[(2-carboxybenzyl)thio]-4-[[2'-(1H-tetrazol-5-yl )biphenyl-4 - yl]methyl]-4H-1,2,4-triazole (71, IC50 1.4 nM), which blocked the AII pressor response in conscious rats at 0.3 mg/kg iv with a duration of action of approximately 6 h, similar to that of DuP 753. Although 71 was active orally only at a 10-fold higher dose level, good oral bioavailability was demonstrated for a monoacidic analogue 62. Most potent among the bicyclic derivatives was 2-n-butyl-5,6-dimethyl-3-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]meth yl]- 3H-imidazo[1,2-b][1,2,4]triazole (93, IC50 7.8 nM). The effects of hydrophobic, hydrogen-bonding, and ionic interactions with the AT1 receptor are considered.

Assessment of a selective inhibitor of herpes simplex virus thymidine kinase (L-653,180) as therapy for experimental recurrent genital herpes

Herpes simplex virus (HSV)-coded thymidine kinase (TK) is important in efficient reactivation of latent infection. These studies were designed to investigate whether treatment of latently infected animals with a TK inhibitor altered the natural history of recurrent HSV disease. 9-([(Z)-2-(hydroxymethyl)cyclohexyl]methyl) guanine (L-653,180) is a potent and selective nonsubstrate inhibitor of HSV TK which can suppress or delay reactivation of HSV-1 from latently infected cells in vitro without affecting viral replication. In an initial study, six female Hartley guinea pigs were treated with L-653,180 in their diet (25 mg/30 g of food) and water (300 mg/liter) for 7 days. Blood, urine, kidney, liver, spinal cord, and cerebral cortex specimens were collected. L-653,180 was detected in all specimens at concentrations which, although low, were higher than the in vitro 50% inhibitory concentration of the drug against HSV TK. In the second study, 20 female Hartley guinea pigs were randomized into two groups following recovery from primary genital HSV-2 infection. One group received L-653,180 in diet and water for 4 weeks beginning 21 days postinoculation. Animals were examined daily for recurrent lesions for 10 weeks. Treated animals experienced fewer recurrences during the treatment period but the results were not significantly different from results with controls. During the first 2-week posttreatment period, L-653,180-treated animals had significantly fewer recurrences than control animals (P = 0.02). Over the entire 10-week observation period, treated animals experienced fewer recurrences (P = 0.06). These results suggest that inhibitors of viral TK may be useful in limiting reactivation of latent virus and thus recurrent infections. In these experiments, the amount of drug that could be administered to the animals was limited by its poor solubility. Further studies with more potent and soluble inhibitors of HSV TK appear to be warranted.

Inhibitors of human renin with C-termini derived from amides and esters of alpha-mercaptoalkanoic acids

New transition-state analogues bearing C-termini derived from alpha-mercaptoalkanoic acids, esters, and amides were prepared and evaluated as inhibitors of human renin. Addition of alpha-mercaptoalkanoate esters to a chiral Boc-amino epoxide intermediate led ultimately to the target [(2R,3S)-3-(BocPheHis-amino)-4-cyclohexyl-2-hydroxy-1-butyl]thio derivatives. The corresponding sulfoxide and sulfone analogues were also investigated. Some of these derivatives, including one with a stable BocPhe replacement, were relatively potent inhibitors of human plasma renin, having IC50 values below 10 nM. When selected compounds were administered intravenously to sodium-deficient rhesus monkeys (Macaca mulatta) at 0.06-1 mg/kg, they reduced plasma renin activity by 87-94%. However, the accompanying drop in blood pressure was of short duration.

Renin inhibitors containing C-termini derived from mercaptoheterocycles

A series of transition-state analogues having heterocyclythio C-termini has been synthesized and evaluated for inhibition of human renin. Addition of mercaptoheterocycles to a chiral Boc-amino epoxide intermediate led, after several steps, to the target [(2R,3S)-3-(BocPheHis-amino)-4-cyclohexyl-2-hydroxy-1-butyl]thio derivatives. Oxidation of the thioether to sulfone was also investigated. Several of the compounds, especially those derived from N1-substituted-5-mercaptotetrazoles or N4-substituted-3-mercapto-5-(trifluoromethyl)-1,2,4-triazoles, were moderately potent inhibitors of human plasma renin, having IC50 values of 30-40 nM. When selected compounds were administered intravenously to sodium-deficient rhesus monkeys at 0.3-1.2 mg/kg, they reduced plasma renin activity by 75-98%. However, this inhibition and the accompanying drop in blood pressure were of short duration.

Synthesis and antiherpetic activity of (+/-)-9-[[(Z)-2-(hydroxymethyl)cyclopropyl]methyl]guanine and related compounds

A series of analogues of acyclovir and ganciclovir were prepared in which conformational constraints were imposed by incorporation of a cyclopropane ring or unsaturation into the side chain. In addition, several related base-modified compounds were synthesized. These acyclonucleosides were evaluated for enzymatic phosphorylation and DNA polymerase inhibition in a staggered assay and for inhibitory activity against herpes simplex virus types 1 and 2 in vitro. Certain of the guanine or 8-azaguanine derivatives were good substrates for the viral thymidine kinase and were further converted to triphosphate, but none was a potent inhibitor of the viral DNA polymerase. Nevertheless, one member of this group, (+/-)-9-[[(Z)-2-(hydroxymethyl)cyclopropyl]methyl]guanine (3a), displayed significant antiherpetic activity in vitro, superior to that of the corresponding cis olefin 4a. Another group, typified by (+/-)-9-[[(E)-2-(hydroxymethyl)cyclopropyl]methyl]adenine (17b), possessed modest antiviral activity despite an apparent inability to be enzymatically phosphorylated. The relationship of side-chain conformation and flexibility to biological activity in this series is discussed.

5-Halo-6-phenyl pyrimidinones and 8-substituted guanosines: biological response modifiers with similar effects on B cells

5-Halo-6-phenyl pyrimidinones, represented by 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP) and 2-amino-5-iodo-6-phenyl-4(3H)-pyrimidinone (AIPP), and 8-substituted guanosines, represented by 8-bromoguanosine (8-BrGuo) and 8-mercaptoguanosine (8-MGuo), are well-documented biological response modifiers. We have found that these substituted pyrimidinones and guanosines are very similar in their abilities to activate B cells. ABPP, AIPP, 8-BrGuo, and 8-MGuo induced murine B cells to polyclonally proliferate and differentiate in vitro. The maximal B-cell response levels and the kinetics of the responses elicited with both classes of compounds were comparable; however, ABPP and AIPP were approximately 10-fold more potent than 8-BrGuo and 8-MGuo. An additional similarity observed between the two classes was that polyclonal activation of B cells by ABPP, AIPP, 8-BrGuo, and 8-MGuo was limited to large B cells which had probably been activated previously in vivo. This is in contrast to lipopolysaccharide which is capable of inducing both large, activated B cells and small, resting B cells to proliferate and differentiate. Although substituted pyrimidinones and guanosines were not able to induce new DNA synthesis or antibody production in small B cells, both classes of compounds increased the expression of Ia antigens on the surface of both small and large B cells. These data, together with the recent observations that 8-BrGuo, like ABPP and AIPP, can stimulate NK and cytotoxic macrophage activity via the induction of interferon, strongly suggest that 5-halo-6-phenyl pyrimidinones and 8-substituted guanosines belong to the same structural class of biological response modifiers. Thus, the residues held in common by these two classes of stimulators may interact with the same cellular constituent in the target cells.

Inhibition of the mammalian beta-lactamase renal dipeptidase (dehydropeptidase-I) by (Z)-2-(acylamino)-3-substituted-propenoic acids

The title enzyme deactivates the potent carbapenem antibiotic imipenem in the kidney, producing low antibiotic levels in the urinary tract. A series of (Z)-2-(acylamino)-3-substituted-propenoic acids (3) are specific, competitive inhibitors of the enzyme capable of increasing the urinary concentration of imipenem in vivo. Many of the compounds were prepared in one step from an alpha-keto acid and a primary amide. The optimum R2 groups are 2,2-dimethyl, -dichloro, and -dibromocyclopropyl. With R2 = 2,2-dimethylcyclopropyl (DMCP), a wide variety of R3 groups including alkyl, oxa- and thiaalkyl, and alkyl groups containing acidic, basic, and neutral substituents give effective inhibitors with Ki values of 0.02-1 microM and a range of pharmacokinetic properties. By resolution of enantiomers and X-ray crystallography, the enzyme-inhibitory activity of the DMCP group was found to reside with the 1S isomer. The cysteinyl compound 176 (cilastatin, MK-0791) has the desired pharmacological properties and has been chosen for combination with imipenem.

Inhibition of human purine nucleoside phosphorylase by acyclic nucleosides and nucleotides

In an effort to develop more potent inhibitors of human purine nucleoside phosphorylase (PNP) as immunosuppressive and cancer chemotherapeutic agents, the affinity of the erythrocytic enzyme for 30 acyclic nucleosides, nucleotides and related compounds was determined. Among the acyclonucleosides, 2'-nordeoxyguanosine [2'NDG, 9-(1,3-dihydroxy-2-propoxymethyl)guanine] had a 3-fold greater affinity than acyclovir, and 8-amino-2'NDG was the best inhibitor with Ki = 2.6 X 10(-7) M. The ether moiety of the acyclovir and 2'NDG side-chains was not important for binding. Phosphorylated 2'NDG analogs appeared to act as multisubstrate analogs with optimal binding at low (1 mM) phosphate concentration. The 2'NDG mono- and triphosphates had higher affinities than those reported for the phosphorylated acyclovir derivatives but the diphosphate had a similar Ki value of 9 X 10(-9) M. Poor affinity, independent of phosphate concentration, was found for 9-(2-phosphonoethyl)guanine. The 3'-phosphate derivative of 8-(3-hydroxypropyl)-9-methylguanine inhibited with a Ki = 2 X 10(-5) M in 1 mM phosphate. The chemical syntheses of new analogs are described.

Enzymatic phosphorylation of the antiherpetic agent 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine

The antiherpetic agent 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine (iNDG) is phosphorylated by HSV1 thymidine kinase, and its phosphorylated products inhibit DNA polymerase activity. iNDG exists in two enantiomeric forms, each with a primary and a secondary hydroxyl; thus, a number of possibilities for preferential phosphorylation exist, which were explored in this study. HSV1 thymidine kinase phosphorylates the primary hydroxyl of both the R and the S isomers of iNDG. This was established by comparison with analogues in which either the primary or the secondary hydroxyl was replaced by fluorine or hydrogen and also by a study of the NMR spectrum of the monophosphate. GMP kinase phosphorylates the R and the S monophosphates to the respective diphosphates. Further phosphorylation, however, is much more efficient with the S than with the R isomer. Furthermore, (S)-iNDG triphosphate is a more potent inhibitor of HSV1 DNA polymerase than (R)-iNDG triphosphate. These differences in the biochemical specificities of the two isomers account for the observed higher antiviral potency of (S)-iNDG as compared to that of (R)-iNDG.

Synthesis and antiherpetic activity of (S)-, (R)-, and (+/-)-9-[(2,3-dihydroxy-1-propoxy)methyl]guanine, linear isomers of 2'-nor-2'-deoxyguanosine

Racemic 9-[(2,3-dihydroxy-1-propoxy)methyl]guanine [(+/-)-iNDG], a new analogue of acyclovir (ACV) and a structural analogue of 2'-nor-2'-deoxyguanosine (2'NDG), was synthesized and found to inhibit the replication of herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). Subsequently, its optical isomers, (R)- and (S)-iNDG, were prepared from chiral intermediates. The chloromethyl ethers of 1,2-di-O-benzyl-D- and -L-glycerol were made and reacted with tris(trimethylsilyl)guanine to give the 9-alkylated guanines, which were deprotected by catalytic hydrogenolysis. Against HSV-1 and HSV-2 in cell culture, (S)-iNDG was approximately 10- to 25-fold more active than the R enantiomer and had an ED50 comparable to those for ACV and 2'NDG. The inferior activity of (R)-iNDG paralleled the poor inhibition of viral DNA polymerase by its phosphorylation products. In mice infected intraperitoneally or orofacially with HSV-1 or intravaginally with HSV-2, (S)-9-[(2,3-dihydroxy-1-propoxy)methyl]guanine [(S)-iNDG] was less efficacious than 2'NDG but comparable to or more active than ACV.

9-([2-hydroxy-1-(hydroxymethyl)ethoxy]methyl)guanine: a selective inhibitor of herpes group virus replication

9-([2-Hydroxy-1-(hydroxymethyl)ethoxy]methyl)guanine (2'-nor-2'-deoxyguanosine; 2'NDG) selectively inhibits the replication of herpes group viruses. In cell culture studies 2'NDG was at least 10-fold more potent than acyclovir (ACV) in inhibition of human cytomegalovirus replication and Epstein-Barr virus-induced lymphocyte transformation and was about as effective as ACV in inhibition of herpes simplex viruses 1 and 2 and varicella zoster virus. Orally administered 2'NDG was 6- to 50-fold more efficacious than ACV in treating systemic or local HSV-1 infection or HSV-2 intravaginal infection in mice. The mode of action of 2'NDG appears to involve phosphorylation by herpes simplex virus thymidine kinase and subsequent phosphorylations by cellular kinases to produce 2'NDG triphosphate, which is a potent inhibitor of herpes virus DNA polymerase. Compared to ACV, 2'NDG was a more efficient substrate for HSV-1 thymidine kinase (Vmax/Km for 2'NDG 30-fold higher than that of ACV), whereas 2'NDG monophosphate is a more efficient substrate for GMP kinase (Vmax/Km for 2'NDG monophosphate 492-fold higher than that for ACV monophosphate). The combined effect is more rapid production of the inhibitory triphosphate from 2'NDG than from ACV.

Chemical and enzymatic properties of riboflavin analogues

The chemical and enzymatic properties of 26 analogues of riboflavin are presented. These analogues include both endo- and exocyclically substituted isoalloxazines with redox potentials from -370 to -128 mV. Physical and chemical data such as the electronic absorption spectra, pKas, and redox potentials of the analogues are presented and are discussed with respect to preferred tautomeric and resonance forms. Like riboflavin, most of the analogues are shown to be catalytic oxidants of dihydro-5-deazaflavins. Analogue binding to egg white binding apoprotein has been quantitated and serves to determine the origins of binding site specificity for this protein. Nearly all of the analogues that possess D-ribityl groups are found to be processed to the FAD level by the flavokinase/FAD synthetase system of Brevibacterium ammoniagenes. Most extensively studied are the reactivities of the analogues with the NAD(P)H:flavin oxidoreductase of Beneckea harveyi. Many of the analogues are substrates in this enzymatic redox reaction, and a linear free energy-rate relation (log Vmax vs. E0' of the analogue) is seen that parallels similar relationships in the nonenzymatic oxidation of dihydro-5-deazaflavins. This suggests a common mechanism for the reactions of such diverse flavins as riboflavin, 5-deazariboflavin, and 1-deazariboflavin.

Synthesis and evaluation of 6-arylactamido-2,4-diaminoquinazolines and related compounds as folic acid antagonists

A series of 2,4-diaminoquinazolines bearing an aryl function attached to the 6 position through an acetamido or related linkage was synthesized. Each compound was evaluated as an inhibitor of rat liver dihydrofolate reductase as well as for suppressive antimalarial effects against Plasmodium berghei in mice. Significant in vivo activity was found to reside primarily with 5-chloro-6-arylacetamido derivatives. Most of these compounds were also tested for prophylactic activity against sporozoite-induced Plasmodium gallinaceum in chicks. Thirteen compounds, each of which possesses a 5-Cl or 5-CH3 group, displayed curative activity in this test system. Since several of these showed markedly greater potency against the avian infection, selective inhibitory action upon preerythrocytic forms of the malaria parasite is thus implied.