Antiviral properties of 3-quinolinecarboxamides: a series of novel non-nucleoside antiherpetic agents.

Novel antiherpetic 3-quinolinecarboxamides were discovered as part of a drug discovery program at Sterling Winthrop Inc. A major goal of this research was to identify novel non-nucleoside agents possessing activity against acyclovir resistant herpes simplex virus. From screening compound libraries in an HSV-2 plaque reduction assay, 1-ethyl-1,4-dihydro-4-oxo-7-(4-pyridinyl)-3-quinolinecarboxamide (1) emerged as an attractive lead structure. By modifying the quinoline ring at the 1-, 2-, 3-, 4-, and 7-positions, analogues were identified that have up to 5-fold increased in vitro potency relative to acyclovir. In a single dose mouse model of infection the 1-(4-FC6H4) analogue 17, one of the most potent derivatives in vitro, displayed comparable oral antiherpetic efficacy to acyclovir at 1/16 the dose; in a multiple dose regimen, however, it was 2-fold less potent. Mechanism of action studies indicate that these new compounds interact with a different, as yet undefined, molecular target than acyclovir.

Synthesis and antibacterial activity of some novel 1-substituted 1,4-dihydro-4-oxo-7-pyridinyl-3-quinolinecarboxylic acids. Potent antistaphylococcal agents.

The palladium-catalyzed coupling of 3- and 4-(trialkylstannyl)pyridines with 7-bromo or 7-chloro 1-substituted 1,4-dihydro-4-oxo-3-quinolinecarboxylates has provided access to the corresponding 1-substituted 1,4-dihydro-4-oxo-7-pyridinyl-3-quinolinecarboxylic acids. The antibacterial activity of these derivatives was studied with the finding that the optimal 1- and 7-position substituents for Gram positive activity are cyclopropyl and 4-(2,6-dimethylpyridinyl), respectively. We find that for the fluorine-substituted derivatives studied, the position of the fluorine on the quinolone nucleus or the number of fluorine atoms does not seem to be important for good Gram positive activity. For 1-cyclopropyl 7-(2,6-dimethyl-4-pyridinyl) derivatives, the 6-fluoro 4a, 8-fluoro 10d, 6,8-difluoro 10b, and 5,6,8-trifluoro 8, all provided equal antibacterial activity against Staphylococcus aureus ATCC 29213. There is also a correlation between the substitution on the 7-(4-pyridinyl) group and the Gram positive activity, particularly for S. aureus, clearly indicating that the 2,6-dimethylpyridinyl group is optimal. The MIC50 value for the most potent agents in this study against S. aureus ATCC 29213 is 0.008 microgram/mL. By comparison, ciprofloxacin and aminopyrrolidine 28 gave values of 0.25 and 0.015 microgram/mL, respectively, against this organism.

4,5-Dihydro-3-(methanesulfonamidophenyl)-1-phenyl-1H-2,4-benzodiazepines: a novel class III antiarrhythmic agents.

A series of 4,5-dihydro-3-[2-(methanesulfonamidophenyl)ethyl]-1-phenyl- 1H-2,4-benzodiazepines has been identified as potential antiarrhythmic agents that interact at the delayed rectifier myocardial potassium channels (IKr) and prolong the ventricular effective refractory period (ERP) in rabbit isolated Langendorff heart preparations. Structure-activity relationship (SAR) studies based upon prolongation of ERP indicate that placement of the sulfonamido group is important for potent activity in this model. Furthermore, methanesulfonamido has enhanced activity over its ethyl or trifluoromethyl analogs. Slightly greater activity was observed in compounds that had a heteroatom in the ethyl bridge that connects the methanesulfonamidophenyl to the benzodiazepine. Further incremental improvements in activity were noted when the 1-phenyl ring was substituted with a variety of substituents. Chirality of the compounds of interest in this series does not appear to influence activity in this model. Several of these compounds were chosen for advanced evaluation, and all possess high selectivity for blockade of potassium current in hearts relative to other ion channels. In addition, these compounds prolong cardiac refractoriness in dogs following oral dosing. Thus, these agents may represent potential new class III agents, but with the potential liability of myocardial IKr blockers.

Synthesis and structure-activity relationships of 6-heterocyclic-substituted purines as inactivation modifiers of cardiac sodium channels.

Purine-based analogs of SDZ 211-500 (5) were prepared and evaluated as inactivation modifiers of guinea pig or human cardiac sodium (Na) channels expressed in Xenopus oocytes. Substances which remove or slow the Na channel inactivation process in cardiac tissue are anticipated to prolong the effective refractory period and increase inotropy and thus have potential utility as antiarrhythmic agents. Heterocyclic substitution at the 6-position of the purine ring resulted in compounds with increased Na activity and potency, with 5-membered heterocycles being optimal. Only minor modifications to the benzhydrylpiperazine side chain were tolerated. Selected compounds which delayed the inactivation of Na channels were found to increase refractoriness and contractility in a rabbit Langendorff heart model, consistent with the cellular mechanism. Activity in both the oocyte and rabbit heart assays was specific to the S enantiomers. Preliminary in vivo activity has been demonstrated following intravenous infusion. The most promising compound on the basis of in vitro data is the formylpyrrole (S)-74, which is 25-fold more potent than DPI 201-106 (1) in the human heart Na channel assay.

Synthesis and evaluation of 6,11-ethanohexahydrobenzo[b]quinolizidines: a new class of noncompetitive N-methyl-D-aspartate antagonists.

The synthesis and in vitro and in vivo evaluation of 12,13-cycloalkyl-6,11-ethanobenzo[b]-quinolizidines, a new class of noncompetitive N-methyl-D-aspartate (NMDA) antagonists acting at the PCP site on the NMDA receptor complex, is reported. Structure-activity relationship studies led to the identification of 10-hydroxy-(6 alpha,11 alpha,11 alpha beta,12R*,13S*)-1,3,4,6,11,11a,13,14,15,16-decahydro-12H- 6,11[1',2']-endo-cyclopenta-2H-pyrido[1,2-b]isoquinoline hydrobromide (5h) and 9-hydroxy-(6 alpha,11 alpha,11a beta,12R*,13S*)- 1,3,4,6,11,11a,13,14,15,16-decahydro-12H-6,11-[1',2']-endo-cycl ope nta-2H- pyrido[1,2-b]isoquinoline hydrobromide (5i), the most potent members of this series with Ki values of 2.3 +/- 0.2 and 2.3 +/- 0.5 nM, respectively. Molecular modeling studies revealed that this series of compounds occupies both lipophilic sites of the Andrews PCP receptor model and shares structural features which are common to other classes of known noncompetitive NMDA antagonists such as MK-801.

Novel NMDA antagonists: replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with heteroisoquinolinium cations.

Replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with thiazolium (4a and 4b) and N-methylimidazolium (4c and 4d) resulted in equipotent compounds in the [3H]TCP binding assay. The corresponding N-methyl-1,2,4-triazolium analogs were less potent in this assay. The thiazolium derivative 4b, with a Ki = 2.9 nM, is being evaluated as a possible neuroprotective N-methyl-D-aspartic acid (NMDA) antagonist.

Orally bioavailable benzisothiazolone inhibitors of human leukocyte elastase.

Human leukocyte elastase (HLE) has been proposed as a primary mediator of pulmonary emphysema and other inflammatory airway diseases. HLE is capable of cleaving many proteins, including elastin, other components of connective tissue, certain complement proteins, and receptors. Under normal conditions an appropriate balance exists in the lung between HLE and endogenous inhibitors, which scavenge the released enzyme before it exerts deleterious effects in the lung. Emphysema is thought to result from an imbalance in the lung between HLE and endogenous inhibitor (elevated elastase or insufficient inhibitor) that leads to the destruction of alveoli. We have identified WIN 64733 (2) and WIN 63759 (3) as potent (Ki* = 14 and 13 pM, respectively), selective, mechanism-based inhibitors of HLE which are orally bioavailable in the dog (absolute bioavailability 46% and 21%, respectively). In this series the in vitro stabilities of the inhibitors in blood, jejunal homogenates, and liver S9 homogenates are useful predictors of oral bioavailability. After being administered orally (30 mg/kg) to dogs, compounds 2 and 3 are found in the lung, being detected in the epithelial lining fluid obtained by bronchoalveolar lavage (Cmax of 2.5 and 0.47 microgram/mL, respectively).

An evaluation of the antirhinoviral activity of acetylfuran replacements for 3-methylisoxazoles. Are 2-acetylfurans bioisosteres for 3-methylisoxazoles?

As a probe of the 3-methylisoxazole portion of our broad-spectrum antipicornaviral series, a panel of 2-acetylfuran analogues was prepared as replacements for the 3-methylisoxazole ring. Comparison of the two series showed remarkable similarity in potency, spectrum of activity, logP, and electrostatic parameters. X-ray studies of 21b bound to human rhinovirus-14 showed that the 2-acetyl group adopted a syn conformation and the carbonyl oxygen acts as a hydrogen bond acceptor with ASN219 in much the same way as the nitrogen of the isoxazole. The importance of the syn conformation and the hydrogen-bonding capability was confirmed by the reduced antiviral activity of the 2-methylfuran and 2-formylfuran analogues. From the results of this study, it is apparent that the syn-2-acetylfuran ring is acting as a bioisostere for the 3-methylisoxazole.

4,5-Dihydro-1-phenyl-1H-2,4-benzodiazepines: novel antiarrhythmic agents.

A series of 4,5-dihydro-1-phenyl-1H-2,4-benzodiazepines has been identified as potential antiarrhythmic agents that interact with sodium and potassium channels and prolong the ventricular effective refractory period (ERP) in anesthetized guinea pigs. Concomitant displacement of radiolabeled bactrachotoxin from site II in Na+ channels and of radiolabeled dofetilide from delayed rectifier K+ channels was evident with all members of this chemical series at a concentration of 10 microM. Structure-activity relationship (SAR) studies using a paced guinea pig model to assess prolongation of the ERP indicated that methyl or ethyl at the 1-position had little effect on activity, while larger groups caused a diminution of activity. Compounds with substituents at either the 3- or 4-position that increased lipophilicity generally were more potent; however, too many lipophilic substituents simultaneously at positions 1, 3, and 4 resulted in less active compounds. Substituents on either aromatic ring had little influence on activity, and phenyl at the 5-position resulted in a significant reduction in antiarrhythmic activity. When two sets of enantiomerically pure compounds were tested in the guinea pig, chirality was shown to be important for activity of 8, where the (R)-enantiomer was the more active, but not in the case of 15, where the enantiomers were equiactive. Several compounds in this series increased the threshold for ventricular fibrillation and refractoriness in myocardially-infarcted anesthetized cata and delayed the onset of aconitine-induced arrhythmias in anesthetized guinea pigs following intravenous dosing. Moreover, these compounds possessed oral antiarrhythmic activity in conscious myocardially-infarcted dogs. Compound R-15 has been advanced for further biological and toxicological evaluations.

3-Quinolinecarboxamides. A series of novel orally-active antiherpetic agents.

A series of novel 3-quinolinecarboxamides that are structurally similar to the quinolone class of antibacterial agents possess excellent antiherpetic properties. By modifying the quinoline ring at the 1-, 2-, 3-, and 7-positions, analogues were identified that have up to 5-fold increased HSV-2 plaque-reduction potency relative to acyclovir. In a single-dose mouse model of infection, one of the most potent derivatives in vitro, 1-(4-fluorophenyl)-1,4-dihydro-4-oxo-7-(4-pyridinyl)-3-quinolinecarbo xamide (97), displayed comparable oral antiherpetic efficacy to acyclovir at 1/16 the dose; in a multiple-dose regimen, however, 97 was 2-fold less potent. In mice dosed orally with 97, sustained plasma drug levels were evident that may account for the high efficacy observed. The molecular mechanism of action of these agents is not known; however, based on in vitro studies with acyclovir resistant mutants, it is likely that the mechanism differs from that of acyclovir. In vitro plaque-reduction potency was not generally predictive of oral efficacy in mice. An X-ray crystal structure of 97 corroborated the assignment of structure and provided useful insights as to the effect of conformation on plaque-reduction potency.

Antirhinoviral activity of heterocyclic analogs of Win 54954.

A variety of heterocyclic analogs of Win 54954 have been synthesized and tested in vitro against human rhinovirus type 14 (HRV-14) in a plaque reduction assay. The more active compounds were tested against 14 additional serotypes, and the concentration which inhibited 80% of the serotypes tested (MIC80) was measured. One compound, 37, exhibited activity comparable to Win 59454. Physicochemical as well as electrostatic parameters were calculated and the results subjected to a QSAR analysis in an effort to explain differences in activity observed between these compounds; however, no meaningful correlation with biological activity was found with any of these parameters.

Structure-activity studies of 5-[[4-(4,5-dihydro-2-oxazolyl) phenoxy]alkyl]-3-methylisoxazoles: inhibitors of picornavirus uncoating.

A series of substituted phenyl analogues of 5-[[4-(4,5-dihydro-2-oxazolyl) phenoxy]alkyl]-3-methylisoxazoles has been synthesized and evaluated in vitro against several human rhinovirus (HRV) serotypes. Substituents in the 2-position greatly enhanced activity when compared to the unsubstituted compound. Many of these compounds exhibited mean MICs (MIC) against five serotypes as low as 0.40 microM. The mean MIC correlated well (r = 0.83) with the MIC80 (the concentration that inhibited 80% of the serotypes tested). A quantitative structure-activity relationship study indicated a strong dependency of MIC on lipophilicity (log P) in combination with inductive effects (sigma m) and bulk factors (MW).

Antiviral activity of Win 41258-3, a pyrazole compound, against herpes simplex virus in mouse genital infection and in guinea pig skin infection.

Win 41258-3 (4-[6-(2-chloro-4-methoxyphenoxy)hexyl]-3,5-diethyl-1H-pyrazole methane sulfonate) has in vitro and in vivo activity against herpes simplex virus types 1 and 2. In cell culture, a concentration of 2 microgram/ml produced a greater than 50% inhibition of plaque formation of herpes simplex virus type 2, and 3 microgram/ml produced a 100% reduction of herpes simplex virus type 1. Win 41258-3 was effective against herpes simplex virus types 1 and 2 in mouse genital infection after intravaginal administration. Win 41258-3 was administered to mice at 4 h postinfection with solutions containing 1.25, 2.5, 5, or 10% of the compound in saturated tampons. Therapy resulted in a high survival rate (80 to 100%) of treated animals versus 20 to 30% of placebo-treated controls. Win 41258-3 was also effective in guinea pig skin infection produced by herpes simplex virus type 1. Solutions of 2.5, 5, and 10% Win 41258-3, applied to the skin starting 24 h postinfection, resulted in rapid suppression of development of herpetic vesicles and significant reduction of the virus titers in the lesion sites.

Antiviral activity of some beta-diketones. 4. Benzyl diketones. In vitro activity against both RNA and DNA viruses.

The synthesis and in vitro antiviral evaluation of a series of substituted benzyl beta-diketones are described. The introduction of a styryl group onto the phenyl ring enhanced activity against herpesvirus type 2. The 4-methoxystyryl homologue 8 was evaluated extensively in vitro and was found to be effective against both RNA and DNA viruses. Compound 8 was evaluated in the mouse vagina against herpes simplex type 1 and produced a significant increase in survival rate as well as in survival time.

Antiviral activity of some beta-diketones. 3. Aryl bis(beta-diketones). Antiherpetic activity.

A series of bis(beta-diketones) was synthesized and tested in vitro for antiviral actitity against herpes simplex type 2. Two parameters which were studied in an effort to optimize activity were the nature of the aryl group and the length of the alkyl bridge. One of the more active compounds, 4,4'-[(1,4-phenylenedioxy)bis(6,1-hexanediyl)]-bis[3,5-heptanedione] (6), was evaluated more extensively and found to inhibit the cytopathic effect in tissue culture of herpes simplex virus type 1 as well as type 2. Compound 6 was evaluated in vivo topically against herpes simplex type 1 in experimentally induced skin infections in guinea pigs. A topical treatment with 2% of 6 in a vanishing cream base, administered 24 h postinfection applied five times daily for 4 days, significantly reduced the number and size of herpetic vesicles.

Antiviral activity of some beta-diketones. 2. Aryloxy alkyl diketones. In vitro activity against both RNA and DNA viruses.

A series of aryloxy alkyl diketones II was synthesized and screened in vitro for antiviral activity. The effect of various substituents on the phenyl ring, as well as the length of the alkyl bridge, was examined to establish the requirements for optimum activity. One of the most active members of the series, 4-[6-(2-chloro-4-methoxy)phenoxy]hexyl-3,5-heptanedione (56), exhibited a high level of activity against both DNA and RNA viruses in both the tissue culture and organ culture screens and was particularly effective against herpesvirus type 1 and 2.