2-Amino-benzoxazinones for the treatment of viral infections

Abstract: A class of compounds for the treatment of viral infections. Compounds of particular interest are defined by Formula I or a pharmaceutically-acceptable salt thereof.

Description: FIELD OF THE INVENTION This invention is in the field of antiviral agents and specifically relates to compounds, compositions and methods for treating herpes-related disorders. BACKGROUND OF THE INVENTION There is a great need for new therapies for the treatment of viral diseases. Whereas there has been great progress in developing a variety of therapies for the treatment of bacterial infections, there are few viable therapies for the treatment of viruses. zidovudine is the primary approved treatment for human immunodeficiency virus. Ganciclovir, acyclovir and foscarnet are currently utilized for the treatment of herpesvirus infections. However, these therapies can have substantial side effects based on their deleterious effects on host cell DNA replication or their effect on a limited number of viral infections. In addition, viruses are known to develop resistance to therapies, which causes a progressive decline in efficacy. Viruses are classified into broad categories based on whether they incorporate RNA or DNA. Important virus families classified of the DNA type include adenoviridae, poxviridae, papovaviridae and herpesviridae. Herpesviridae is a family of DNA viruses which include herpes simplex virus type-1 (HSV-1), herpes simplex virus type-2 (HSV-2), cytomegalovirus (CMV), varicella-zoster virus (VZV), Epstein-Barr virus, human herpesvirus-6 (HHV6), human herpesvirus-7 (HHV7), human herpesvirus-8 (HHV8), pseudorabies and rhinotracheitis, among others. It is known that herpesviruses express their genetic content by directing the synthesis of a number of proteins encoded by the herpesvirus DNA in the host cell. One of the important virus-encoded proteins is made as a precursor consisting of an amino terminal-located protease and carboxyl terminal-located assembly protein. This precursor is proteolytically processed in an autocatalytic manner at a specific amino acid sequence known as the "release" site yielding separate protease and assembly protein. The assembly protein is cleaved further by the protease at another specific amino acid sequence known as the "maturation" cleavage site. Recently, EP No. 514,830, published November 25, 1992, describes a virus-specific serine protease which has a role in herpesvirus replication. Additionally, Lui and Roizman [ J. Virol, 65, 5149 (1991)] describe the sequence and activity of a protease and the associated assembly protein encoded by U L 26 of HSV-1. A. R. Welch et al. [Proc. Natl. Acad. Sci. USA, 88, 10792 (1991) and WO93/01291, published Jan. 21, 1993] describe the related protease (also known as assemblin) and assembly protein encoded by U L 80 of CMV. An approach currently being investigated for potential use in the treatment of herpesvirus infections is the development of inhibitors of herpesvirus proteases. 4 H -3,1-Benzoxazinones have been described in the literature as having serine protease activity, among others. While compounds of this type have been reported to have serine protease inhibitory activity, none have been reported to inhibit viral assemblin protease. For example Teshima et al. (J. Biol. Chem., 257 , 5085-5091 (1982)] describe various 2-alkyl-4H-3,1-benzoxazin-4-ones as enzyme inhibitors. Moorman and Abeles [J. Amer. Chem. Soc ., 104, 6785-6786 (1982)] describe 4H-3,1-benzoxazin-2,4-dione as having some enzyme inhibitory activity. R. Stein, et al. [ Biochemistry, 26 , 4126-4130, (1987)] describe 2-alkyl-4H-benzoxazin-4-ones, with further substitution at the 5, 6 and 7 positions, as inhibiting the elastase enzyme. WO publication 92/18488 (published 29 Oct. 1992) describes 2-alkyl-4H-3,1-benzoxazin-4-ones with substitution at the 5 and 7 positions as selective inhibitors of elastase. European Application 206,323 (published 30 Dec. 1985) describes 2-alkoxy-, 2-aryloxy- and 2-aralkoxy-4H-3,1-benzoxazin-4-ones, having substitution at the 5, 6, 7, and 8 positions, as enzyme inhibitors. U. S. Patent 4,745,116, to A. Kranz et al. describes 2-alkoxy, 2-aryloxy- and 2-aralkoxy-4H-3,1-benzoxazin-4-ones, having further substitution at the 5, 7 and 8 positions, as enzyme inhibitors. U.S. Patent 5,428,021, to C. Hiebert et al., describes 6-(aminoacid)amino-2-alkoxybenzoxazinones as elastase inhibitors. WO publication 96/07648, published 14 March 1996, describes 2-phenylamino-benzoxazinones for the treatment of Alzheimer's, and specifically, 6-chloro-2-(2-iodophenylamino)-benzo[d][1,3]oxazin-4-one is described. 2-Amino-4 H -3,1-benzoxazinones have been described. A. Krantz et al. [ J. Med. Chem. , 33 , 464-479 (1990)] describe 4H-3,1-benzoxazin-4-ones substituted with alkyl, alkylamino, alkoxy and alkylthio substituents at the 2-position, and with further substitution at the 5, 6 and 7 positions, as elastase inhibitors. Uejima, et al. [J. Pharm. Exp. Ther., 265, 516-522 (1993)] describe 2-alkylamino-5-methyl-7-acylamino-4H-3.1-benzoxazin-4-ones as highly selective elastase inhibitors with significant plasma stability. U. S. Patent 4,657,893, to A. Krantz et al, describes 2-alkylamino- and 2-alkylurido-4H-3,1-benzoxazin-4-ones having further substitution at the 5, 7 and 8 positions, as enzyme inhibitors. F. L. M. Alvarez [An. Quim., 79, 115-17 (1983)] describes the preparation of 2-sulfonylamino-4H-3,1-benzoxazinones. J.G. Tercero et al. [ An. Quim., 83 , 247-50 (1987)] describe the preparation of 2-arylsulfonylamino-4 H -3,1-benzoxazinones. I. Butula et al. [ Croat . Chem. Acta, 54 , 105-8 (1981)] describe the synthesis of 2-alkylamino-4H-3,1-benzoxazinones. H. Ulrich et al. [ J. Org Chem., 32 , 4052-53 (1967)] describe the synthesis of 2-alkylamino-4H-3,1-benzoxazinones. E. Papadopoulos [ J. Heterocyclic. Chem., 21 , 1411-14 (1984)] describes the use of 2-haloalkylamino-4 H -3,1-benzoxazin-4-one as a starting material for the synthesis of phenylureas. European Patent Application 466,944 (published 22 Jan. 1992) describes 2-alkylamino-7-acylamino-5-alkyl-4H-benzoxazin-4-ones as selective enzyme inhibitors of elastase. M. Badawy et al.[ J . Heterocyclic. Chem., 21 , 1403-4 (1984)] describe the use of N-phenyl-2-amino-4H-3,1-benzoxazin-4-one as a starting material for the synthesis of quinazolines. R. Khan and R. Rastogi [ J. Chem. Research(S), 342-43 (1992)] describe the synthesis of 2-[5-aryl-1,3,4-oxadiazol-2-yl]amino-4 H -3,1-benzoxazin-4-ones. 4H-3,1-Benzoxazin-4-ones have not previously been described as selective assemblin protease inhibitors or for the treatment and/or prophylaxis of viral infection. DESCRIPTION OF THE INVENTION The present invention relates to a series of specific substituted benzoxazinones, useful in the therapeutic and prophylactic treatment of viral infections, as defined by general Formula I and selected from a group of compounds consisting of 5-methyl-2[[(1R)-1 phenylethyl]amino]-4H-3,1-benzoxazin-4-one; N α -(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-N ε -[(phenylmethoxy)carbonyl]-L-lysine, 1,1-dimethylethyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yt)-L-phenylalanine, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, 1,1-dimethylethylester; 2-[[2-methoxy-(1S)-(1-phenylmethyl)ethyl]amino]-5-methyl-4H-3,1-benzoxazin-4-one; 3,5-diiodo-N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tyrosine, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl-O-methyl-L-tyrosine, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-phenylglycine, 1,1-dimethylethyl ester; αS-[(5-methyl-4-oxo-4H-3,1 -benzoxazin-2-yl)amino]-4-methoxy-N-methyl-N-(phenylmethyl)benzenepropanamide; 5-methoxy-2-[[(1R)-1 -phenylethyl]amino]-4H-3,1-benzoxazin-4-one; and N-[5-methoxy-4-oxo-4H-3,1 - benzoxazin-2-yl)-O-methyl-L-tyrosine, N-methyl-N-phenylmethylamide, and the pharmaceutically acceptable salts of said selected compounds. The compounds of this invention have been shown to be particularly effective against herpetoviridae. Thus they are particularly useful for the treatment of herpes simplex viruses (HSV-1, HSV-2), cytomegalovirus (CMV), herpes varicella-zoster, Epstein-Barr, HHV6, HHV7, pseudorabies and rhinotracheitis, among others. The invention further involves a method of treating a subject having a viral infection with an effective amount of a compound which can inhibit a virus-specific protease. Preferably, the subject is treated with a herpesvirus protease inhibitor. More preferred is a method wherein the viral protease inhibitor is a CMV protease inhibitor or an HSV protease inhibitor. Even more preferred is a method wherein the subject is treated with an inhibitor of CMV protease, encoded by U L 80, HSV-1 protease or HSV-2 protease encoded by U L 26, such as the 4H-3,1-benzoxazin-4-one compounds of the present invention. Besides being useful for human treatment, these compounds are also useful for veterinary treatment of animals, including companion animals and farm animals, such as, but not limited to, horses, dogs, cats, cows, sheep and pigs. The present compounds may also be used in co-therapies, partially or completely, in place of other conventional antiviral compounds, such as together with antivirals including but not limited to ganciclovir, docosanol, trifluridine, foscarnet, ribavirin, epervudine, interferon, thymostimulin, Ciba-Geigy CGP-16056, sprofen, Efalith, ibuprofen piconol, ufenamate, thymopentin, aciclovir, valaciclovir, edoxudine, famciclovir, idoxuridine, vidarabine, Epavir, zinc acetate, tromantadine, riodoxol, sorivudine, Yakult Honsha LC-9018, cidofovir, bromovinyldeoxyuridine, Lidakol, Stega Pharmaceutical cytokine-releasing agent, CSL ISCOM, penciclovir, Viraplex, Pharmacia & Upjohn THF, Boehringer Ingelheim BIRR-4, NIH peptide T, Virend, zinc glycerolate, and lobucavir. The phrase "therapeutically-effective" is intended to qualify the amount of the compound which will achieve the goal of improvement in severity and the frequency of incidence, while avoiding adverse side effects typically associated with alternative therapies. The phrase "combination therapy" (or "co-therapy"), in defining use of a compound of the present invention and another agent, is intended to embrace administration of each agent in a sequential manner in a regimen that will provide beneficial effects of the drug combination, and is intended as well to embrace coadministration of these agents in a substantially simultaneous manner, such as in a single capsule having a fixed ratio of these active agents or in multiple, separate capsules for each agent. The present invention comprises a pharmaceutical composition comprising a therapeutically-effective amount of a compound of Formula I in association with at least one pharmaceutically-acceptable carrier, adjuvant or diluent. The present invention also comprises a method of therapeutic and prophylactic treatment of viral infections, particularly herpetoviridae infection, in a subject, the method comprising treating the subject having such herpes infection a therapeutically-effective amount of a compound of Formula I. The present invention also comprises a method of inhibiting a viral protease, the method comprising administering a therapeutically-effective amount of a compound of Formula I. Also included in the family of compounds of Formula I are the pharmaceutically-acceptable salts thereof. The term "pharmaceutically-acceptable salts" embraces salts commonly used to form alkali metal salts and to form addition salts of free acids or free bases. The nature of the salt is not critical, provided that it is pharmaceutically-acceptable. Suitable pharmaceutically-acceptable acid addition salts of compounds of Formula I may be prepared from an inorganic acid or from an organic acid. Examples of such inorganic acids are hydrochloric, hydrobromic, hydroiodic, nitric, carbonic, sulfuric and phosphoric acid. Appropriate organic acids may be selected from aliphatic, cycloaliphatic, aromatic, araliphatic, heterocyclic, carboxylic and sulfonic classes of organic acids, example of which are formic, acetic, propionic, succinic, glycolic, gluconic, lactic, malic, tartaric, citric, ascorbic, glucuronic, maleic, fumaric, pyruvic, aspartic, glutamic, benzoic, anthranilic, mesylic, salicylic, p-hydroxybenzoic, phenylacetic, mandelic, embonic (pamoic), methanesulfonic, ethylsulfonic, benzenesulfonic, pantothenic, toluenesulfonic, 2-hydroxyethanesulfonic, sulfanilic, stearic, cyclohexylaminosulfonic, algenic, β-hydroxybutyric, galactaric and galacturonic acid. Suitable pharmaceutically-acceptable base addition salts of compounds of Formula I include metallic salts made from aluminum, calcium, lithium, magnesium, potassium, sodium and zinc or organic salts made from N,N'-dibenzylethylenediamine, choline, chloroprocaine, diethanolamine, ethylenediamine, meglumine (N-methylglucamine) and procaine. All of these salts may be prepared by conventional means from the corresponding compound of Formula I by reacting, for example, the appropriate acid or base with the compound of Formula I. General synthetic procedures for the preparation of the compounds of Formula I are described in the earlier application WO-A-96/37485. The following examples contain detailed descriptions of methods of preparation of compounds of Formula I. All parts are by weight and temperatures are in Degrees centigrade unless otherwise indicated. The following abbreviations are used: EtOAc - ethyl acetate HCl - hydrochloric acid DMSO - dimethylsulfoxide d 6 -DMSO - deuterated dimethylsulfoxide CDCl 3 - deuterated chloroform CHCl 3 - chloroform CD 3 OD - deuterated methanol Et 2 O - diethyl ether MgSO 4 - magnesium sulfate H 2 SO 4 - sulfuric acid NaHCO 3 - sodium bicarbonate KHSO 4 - potassium hydrogen sulfate NMM - N-methylmorpholine DMF - dimethylformamide DMAP - 4-dimethylaminopyridine CDI - carbonyldiimidazole NaOH - sodium hydroxide KOH - potassium hydroxide LiOH - lithium hydroxide Pd(OH) 2 /C - palladium hydroxide on carbon Pd/C - palladium on carbon EDC - 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide·HCl BOC - tert -butyloxycarbonyl TLC - thin layer chromatography MeOH - methanol KI - potassium iodide CH 2 Cl 2 - methylene chloride Example 1 N-(5-Methyl-d-oxo-4H-3,1-benzoxazin-2-yl)-L-alanine, tert-butyl ester (not claimed) To an ice cooled suspension of CDI (0.53 g, 3.27 mmol) in 5 mL of pyridine was added L-alanine t-butyl ester hydrochloride (0.57 g, 3.13 mmol). After stirring at 0°C for 30 minutes, 2-amino-6-methylbenzoic acid (0.43 g, 2.85 mmol) was added. The ice bath was removed and the reaction was stirred at 65°C for 2 hours. The reaction mixture was diluted with EtOAc and washed with 1N HCl, dried (MgSO 4 ), filtered and evaporated under reduced pressure. The crude product (0.30 g) was dissolved in 5 mL of CH 2 Cl 2 . Triethylamine (0.15 g, 1.47 mmol) and EDC (0.28 g, 1.47 mmol) were added sequentially. After stirring at room temperature for 2 hours the reaction mixture was diluted with EtOAc and washed with 1N HCl, dried (MgSO 4 ), filtered and evaporated under reduced pressure. Silica gel chromatography of the residue (1:1 EtOAc/hexane) afforded 113 mg of N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-alanine, t-butyl ester: Anal. Calc'd. for C 16 H 20 N 2 O 4 : C, 63.14; H, 6.62; N, 9.21. Found: C, 62.90; H, 6.97; N, 9.11. 1 H-NMR (300 MHz, CDCl 3 ) δ 1.49 (s, 9H), 1.50 (d, J = 7 Hz, 3H), 2.70 (s, 3H), 4.48 (pent, J = 7 Hz, 1H), 5.68 (br. s, 1H, exchangeable), 6.95 (d, J = 8 Hz, 1H), 6.99 (d, J = 8 Hz, 1H), 7.45 (t, J = 8 Hz, 1H). Proceeding in a like manner but replacing L-alanine t-butyl ester hydrochloride with other appropriately substituted amines or amine hydrochlorides, the following compound were prepared: (1i) N α -(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-N ε -[(phenylmethoxy)carbonyl)-L-lysine, 1,1-dimethylethyl ester: 1 H-NMR (300 MHz, CDCl 3 ) δ 1.40-1.63 (m, 13H), 1.75-1.95 (m, 2H), 2.65 (s, 3H), 3.18 (m, 3H), 4.42 (m, 1H), 5.08 (s, 2H), 5.47 (br. t, J = 7 Hz, 1H, exchangeable), 6.25 (br. d, J = 7 Hz, 1H, exchangeable), 6.88 (d, J = 8 Hz, 1H), 7.05 (d, J = 8 Hz, 1H), 7.20-7.35 (m, 5H), 7.39 (t, J = 8 Hz, 1H). (1k) N-(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-phenylalanine, methyl ester: Anal. Calc'd. for C 19 H 15 N 2 O 4 : C, 67.44; H, 5.36; N, 8.28. Found: C, 67.20; H, 5.57; N, 8.05. (1m) N-(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, methyl ester: 1 H-NMR (300 MHz, CDCl 3 ) δ 2.67 (s, 3H), 3.40 (m, 2H), 3.70 (s, 3H), 4.93 (m, 1H), 5.47 (br. d, J = 7 Hz, 1H, exchangeable), 6.90-7.20 (m, 5H), 7.30 (d, J = 8 Hz, 1H), 7.43 (t, J = 8 Hz, 1H), 7.55 (d, J = 8 Hz, 1H), 8.44 (s, 1H, exchangeable). (1n) N-(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, 1,1-dimethylethyl ester: 1 H-NMR (300 MHz, CDCl 3 ) δ 1.38 (s, 9H), 2.63 (s, 3H), 3.33 (m, 2H), 4.78 (m, 1H), 5.68 (br. d, J = 7 Hz, 1H, exchangeable), 6.85-7.15 (m, 5H), 7.26 (d, J = 8 Hz, 1H), 7.37 (t, J = 8 Hz, 1H), 7.60 (d, J = 8 Hz, 1H), 8.65 (s, 1H, exchangeable). (10) N-(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-phenylglycine, 1,1-dimethylethyl ester: 1 H-MMR (300 MHz, CDCl 3 ) δ 1.42 (s, 9H), 2.62 (s, 3H), 5.50 (d, J = 7 Hz, 1H), 6.38 (br. s 1H, exchangeable), 6.86 (d, J = 8 Hz, 1H), 7.02 (d, J = 8 Hz, 1H), 7.25-7.38 (m, 4H), 7.47 (d, J = 8 Hz, 2H). (1p) 2-[[2-Methoxy-(1S)-(1-phenylmethyl)ethyl]amino]-5-methyl-4H-3,1-benzoxazin-4-one: Anal. Calc'd. for C 19 H 20 N 2 O 3 : C, 70.35; H, 6.22; N, 8.64. Found: C, 70.00; H, 6.28; N, 8.54. (1q) 3,5-Diiodo-N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tyrosine, methyl ester: 1 H-NMR (300 MHz, CDCl 3 ) δ 2.72 (s, 3H), 3.09 (m, 2H), 3.79 (s, 3H), 4.86 (t, J = 7 Hz, 1H), 5.50 (br. s, 1H, exchangeable), 7.01 (d, J = 8 Hz, 1H), 7.13 (d, J = 8 Hz, 1H), 7.49 (t, J = 8 Hz, 1H), 7.52 (s, 2H). (1r) N-(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-O-methyl-L-tyrosine, methyl ester: 1 H-NMR (300 MHz, CDCl 3 ) δ 2.66 (s, 3H), 3.15 (m, 2H), 3.73 (s, 3H), 3.74 (s, 3H), 4.85 (br. m, 1H), 5.68 (br. s, 1H, exchangeable), 6.80 (d, J = 8 Hz, 2H), 6.92 (d, J = 8 Hz, 1H), 7.07 (m, 3H), 7.42 (t, J = 8 Hz, 1H). (1s) αS-[(5-Methyl-4-oxo-4H-3,1-benzoxazin-2-yl)amino]-4-methoxy-N-methyl-N- (phenylmethyl) benzenepropanamide: Anal. Calc'd. for C 27 H 27 N 3 O 4 : C, 70.88; H, 5.95; N, 9.18. Found: C, 70.65; H, 6.03; N, 9.06. Proceeding in a like manner but replacing 2-amino-6-methylbenzoic acid with 2-amino-6-methoxybenzoic acid [c.f. S. Gould and R. Eisenberg, J. Org. Chem., 56 , 6666-6671 (1991)] and replacing L-alanine tert-butyl ester hydrochloride with other appropriate amines or amine hydrochlorides, the following compounds are prepared: (1t) 5-Methoxy-2-[[(1R)-1-phenylethyl]amino]-4H-3,1-benzoxazin-4-one; and (1u) N-[5-Methoxy-4-oxo-4H-3,1-benzoxazin-2-yl]-O-methyl-L-tyrosine, N-methyl-N-phenylmethylamide. Example 3 2-Ethylamino-5-methyl-4H-3,1-benzoxazin-4-one (not claimed) To a stirred solution of 2-(3-ethylureido)-6-methylbenzoic acid (250 mg, 1.125 mmol) and triethylamine (170 mg, 1.69 mmol) in 10 mL CH 2 Cl 2 at room temperature was added EDC (501 mg, 1.69 mmol). After stirring at room temperature for 3 hours, the reaction mixture was diluted with EtOAc and washed sequentially with 1N HCl and sat'd. NaHCO 3 . The organic fraction was dried (MgSO 4 ), filtered and evaporated under reduced pressure. Silica gel chromatography of the residue (1:1 EtOAc/hexane) afforded 127 mg of product: Anal. Calc'd. for C 11 H 12 N 2 O 2 ·0.25 H 2 O: C, 63.30; H, 6.04; N, 13.42. Found: C, 63.32; H, 5.92; N, 13.10. 1 H-NMR (300 MHz, d 6 -DMSO) δ 1.14 (t, J = 7 Hz, 3H), 2.60 (s, 3H), 3.27 (pent, J = 7 Hz, 2H), 6.95 (d, J = 8 Hz, 1H) , 7.02 (d, J = 8 Hz, 1H) , 7.50 (t, J = 8 Hz, 1H), 7.90 (br. t, J = 7 Hz, 1H, exchangeable). Proceeding in a like manner but replacing 2-(3-ethylureido)-6-methylbenzoic acid with the appropriately substituted benzoic acid, the following compound was prepared: (3c) 5-Methyl-2-[((1R)-1-phenylethyl]amino]-4H-3,1-benzoxazin-4-one: Anal. Calc'd. for C 17 H 16 N 2 O 2 : C, 72.84; H, 5.75; N, 9.99. Found: C, 72.51; H, 5.88; N, 9.97. BIOLOGICAL EVALUATION The compounds of this invention exhibited antiviral activity as indicated by inhibition in vitro of herpesvirus protease and HCMV infectivity. The antiviral activity of the compounds of this invention illustrated in the Examples was determined by the following methods. Enzymatic Assay for HCMV Protease (Assemblin) Inhibitors Assemblin protease activity was determined using a chromogenic para-nitroanilide (pNA) substrate based on the hCMV maturation cleavage site, succinyl-AGVVNA-para-nitroanilide. Incubation of this substrate with assemblin resulted in cleavage of the alanyl para-nitroanilide amide bond, releasing free para-nitroaniline which could be determined by absorbance at 405 nm. Potential protease inhibitors were dissolved in DMSO and 10 µL were added to the wells of a 96-well plate (Dynatech, Immulon 1). Enzyme was diluted to 4.8 µg/mL in assay buffer (10 mM sodium phosphate, pH 7.4, 150 mM sodium acetate, 0.1% CHAPS, 20% glycerol) and 100 µL were added to each well. Following a 30 minute incubation at room temperature, 50 µL substrate (1 part 20 mM succinyl-AGVVNA-paranitroanilide (SEQID:1) in DMSO plus 9 parts assay buffer) were added, and periodic readings taken in a microplate reader at 405 nm relative to 650 nm. Activities were expressed as milliabsorbance unit (mAU) change per minute. Inhibitor potency was determined by comparison with incubations lacking inhibitor, which under these conditions gave an increase of 0.5-1 mAU/min. No increase was seen when enzyme was omitted. Results are included in Table 1. Assay Components: Recombinant HCMV protease: HCMV protease was purified from E. coli expressing a DNA construction encoding the protease domain of the U L 80 open reading frame of human cytomegalovirus strain AD169. The construction also encoded six additional histidine residues at the amino terminus of the protease. These additional histidine residues provided an affinity ligand by which it was purified using nickel-nitriloacetic acid-agarose (Qiagen). The purified protease was stored as a 1-3 mg/ml stock solution in 20 mM HEPES buffer, pH 7.4; containing 20% (v/v) glycerol. This stock was diluted with assay buffer to 4.8 µg/ml. A 100 µL aliquot of this solution was used in the enzyme reaction. A specific substrate was synthesized based on the cleavage specificity of HCMV protease at the "maturation site" of the assembly protein (F. Liu and B. Roizman, J. Virol. , 65, 5149 (1991), and A.R. Welch, et al, J. Virol., 65, 4091 (1991)). The assembly protein maturation site has the sequence ...AGVVNA*SCRLATA...; the substrate used was succinyl-AGVVNA-PNA ( SEQID:1 ) which was prepared by standard peptide synthetic methods such as that described in Bodansky and Bodansky, "The Practice of Peptide Synthesis" (1984), and was stored as a stock solution at 20 mM in dimethyl sulfoxide. This was diluted 10-fold with assay buffer to give a concentration of 2 mM just before use. An aliquot of 50 µL was used in the reaction An assay Buffer (10 mM sodium phosphate buffer, pH 7.4; 150 mM sodium acetate; 0.1% CHAPS; and 20% (v/v) glycerol) was used to dilute stock solutions of enzyme and substrate. Antiviral Assays These complimentary assays tested the ability of a compound to inhibit the production of new virus and the toxicity of the compound to the host cells. It was important that both assays be performed simultaneously in order to compare the results directly since, toxicity may indirectly reduce viral yield. Abbreviations: DMEM - Dulbecco's Modified Eagle Medium; commercially available. FBS - fetal bovine serum; commercially available and contains unknown factors necessary for growth of cells in culture. PBS - phosphate buffered saline: 10 mM sodium phosphate buffer, pH 7.4, 120 mM sodium chloride, 2.7 mM potassium chloride. Viral yield was estimated by measuring the amount of a viral antigen produced 4 days post infection with a monoclonal antibody to an abundant "immediate early" viral protein. An enzyme-linked (horseradish peroxidase) secondary antibody specific to the primary (mouse) antibody was used to measure the amount of viral antigen. Test compounds were diluted to 2-times the desired final concentration in DMEM + 5% FBS. One hundred microliters of this solution was placed in each well of a 96-well plate. This was performed once for the antiviral 96-well plate and again for a cytotoxicity plate. Two controls were also included for both plates; a no drug control and a no virus control. Ganciclovir was routinely tested in antiviral and cytotoxicity plates as a reference standard because it has known antiviral activity for HCMV. All cells were prepared by harvesting human foreskin fibroblasts, with trypsin and re-suspending at a concentration of 5 X 10 5 cells per ml in DMEM. Infected cells were prepared by infecting these with HCMV (strain AD169) at a multiplicity of infection = 0.2. One hundred microliters of uninfected cells (5 x 10 4 cells) were added to the appropriate wells of the cytotoxicity plate. In a similar manner 100 µl of infected cells (5 x 10 4 cells) were added to the appropriate wells of the antiviral plate. Additionally, uninfected cells not treated with test compound were included as controls on the antiviral plate. Plates were incubated for 96 hours at 37°C in 5% CO 2 atmosphere and processed to measure the amount of viral antigen and toxicity. Results are included in Table 1. Enzyme Linked ImmunoSorbant Assay (ELISA) for HCMV Antigens: The following was performed on the antiviral plate only. Media was removed and cells were fixed with 1:1 acetone:methanol for 15 minutes at -20°C. Fixative was removed and cells were washed once with PBS containing 0.05% Tween20. In order to block nonspecific binding of antibodies, each well was incubated with PBS containing 3% (w/v) bovine serum albumin (BSA) for 1 hour at 22°C. The blocking solution was removed and the cells were washed once with PBS containing 0.05% Tween20 before incubating with 1:100 dilution of primary antibody in PBS containing 3% BSA for 2 hours at 22°C. The primary antibody was a monoclonal antibody (mouse source) specific to the immediate early nuclear antigen of HCMV and was commercially available (Dupont). The 1° antibody solution was removed and the plate was rinsed 5 times with PBS containing 1% (v/v) Triton X-100 (PBST) before incubating with secondary antibody diluted 1:1000 in PBS containing 3% BSA for 2 hours at 22°C. The secondary antibody (goat source) recognized the murine-specific determinants of the 1° antibody and was covalently linked to horseradish peroxidase (Sigma). The plate was rinsed 5 times with PBST and once with deionized water before adding 100 µl TMB substrate solution and incubating 30 minutes at 22°C. The reaction was stopped by adding 100 µL of phosphoric acid and the OD at 450 nm recorded. TMB (3,3',5,5' tetramethylbenzidine) was the substrate for the horseradish peroxidase linked to the 2° antibody. It was made from a commercially available kit (Kirkegaard & Perry Laboratories, Inc.). Antiviral activity was calculated by comparing the amount of viral antigen produced in drug treated wells with that produced in wells absent of drug. Results are included in Table 1. Recombinant Human Cytomegalovirus Antiviral Assay In this assay, HCMV replication was monitored by the production of E. coli beta-galactosidase by the engineered virus RC256 [Spaete and Mocarski, Proc.Nat.Acad.Sci., 84, 7213-7217 (1987)]. One antiviral assay and one cytotoxicity assay were done for each compound. Dilutions of test compounds and infection of cells in a 96-well plate was essentially as described above for the HCMV ELISA except for the following. Human foreskin fibroblasts at 3.5 x 10 5 cells per milliliter were infected in solution with RC256 at 0.05 pfu per cell. Compounds and cells were incubated 3 days and processed at 2 days post infection. For the beta galactosidase detection, the supernatant was aspirated from the antiviral assay plates and 50 µl Reporter Lysis Buffer (Promega, diluted to 1X with water) was added per well. The plates were incubated at room temperature at least 30 minutes and plates were frozen at -20 °C at this point for later processing. 50 µl of 2X assay buffer [120 mM Na 2 HPO 4 , 80 mM NaH 2 PO 4 , 2 mM MgCl 2 , 100 mM 2-mercaptoethanol, 4.4 mM ONPG (Sigma)] was added per well and incubated at room temperature 30 to 45 minutes. The reaction was stopped with 100 µl 1M CAPS buffer, pH = 11.0, per well and the optical density was read at 410 nanometers. Ganciclovir was used as a positive control and the EC50 was determined as described above for the HCMV ELISA. Results are included in Table 1. Chymotrypsin Assay The chymotrypsin assay was modified from the method of Delmar et al [Anal. Biochem., 99, 316-320 (1979)]. Bovine pancreas α-chymotrypsin (type II, Sigma) was dissolved in 0.001 N HCl at 1 mg/ml and further diluted 1/600 in assay buffer (0.1 M Tris, pH 7.8, containing 0.1 M CaCl 2 ) before use. 20 µl of test compound in DMSO (or DMSO alone), 100 µl of assay buffer and 30 µl of enzyme were added to 96 well plates, mixed and pre-incubated for 30 minutes at ambient temperature. Reaction was initiated by addition of 50 µl of 0.2 mM N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide (Sigma; 2 mM in DMSO diluted 1/10 in assay buffer before use). The increase in absorbance at 405 nm was monitored for 10 minutes with a Biotek EL340 plate reader. Results are included in Table 1. Human Leukocyte Elastase Assay Human leukocyte elastase (HLE) (gift of R. Senior, Washington University) was dissolved in saline at 1 mg/ml and further diluted 1/20 in assay buffer (0.2 M Tris, pH 8.0) before use. 10 µl of test compound in DMSO (or DMSO alone), 100 µl of assay buffer and 50 µl of enzyme were added to 96 well plates, mixed and pre-incubated for 30 minutes at ambient temperature. Reaction was initiated by addition of 40 µl of 2.5 mM methoxysuccinyl-Ala-Ala-Pro-Val-p-nitroanilide (Sigma; 25 mM in DMSO diluted 1/10 in assay buffer before use). The increase in absorbance at 405 nm was monitored for 10 minutes with a Biotek EL340 plate reader. Results are shown in Table 1. Also embraced within this invention is a class of pharmaceutical compositions comprising one or more compounds of Formula I in association with one or more non-toxic, pharmaceutically-acceptable carriers and/or diluents and/or adjuvants (collectively referred to herein as "carrier" materials) and, if desired, other active ingredients. The compounds of the present invention may be administered by any suitable route, preferably in the form of a pharmaceutical composition adapted to such a route, and in a dose effective for the treatment intended. The compounds and composition may, for example, be administered orally, intravascularly, intraperitoneally, subcutaneously, intramuscularly or topically. For oral administration, the pharmaceutical composition may be in the form of, for example, a tablet, capsule, suspension or liquid. The pharmaceutical composition is preferably made in the form of a dosage unit containing a particular amount of the active ingredient. Examples of such dosage units are tablets or capsules. The active ingredient may also be administered by injection as a composition wherein, for example, saline, dextrose or water may be used as a suitable carrier. The amount of therapeutically active compound that is administered and the dosage regimen for treating a disease condition with the compounds and/or compositions of this invention depends on a variety of factors, including the age, weight, sex and medical condition of the subject, the severity of the disease, the route and frequency of administration, and the particular compound employed, and thus may vary widely. The pharmaceutical compositions may contain active ingredient in the range of about 0.1 to 2000 mg, preferably in the range of about 0.5 to 500 mg and most preferably between about 1 and 100 mg. A daily dose of about 0.01 to 100 mg/kg body weight, preferably between about 0.1 and about 50 mg/kg body weight and most preferably between about 1 to 20 mg/kg body weight, may be appropriate. The daily dose can be administered in one to four doses per day. For therapeutic purposes, the compounds of this invention are ordinarily combined with one or more adjuvants appropriate to the indicated route of administration. If administered per os , the compounds may be admixed with lactose, sucrose, starch powder, cellulose esters of alkanoic acids, cellulose alkyl esters, talc, stearic acid, magnesium stearate, magnesium oxide, sodium and calcium salts of phosphoric and sulfuric acids, gelatin, acacia gum, sodium alginate, polyvinylpyrrolidone, and/or polyvinyl alcohol, and then tableted or encapsulated for convenient administration. Such capsules or tablets may contain a controlled-release formulation as may be provided in a dispersion of active compound in hydroxypropylmethyl cellulose. Formulations for parenteral administration may be in the form of aqueous or non-aqueous isotonic sterile injection solutions or suspensions. These solutions and suspensions may be prepared from sterile powders or granules having one or more of the carriers or diluents mentioned for use in the formulations for oral administration. The compounds may be dissolved in water, polyethylene glycol, propylene glycol, ethanol, corn oil, cottonseed oil, peanut oil, sesame oil, benzyl alcohol, sodium chloride, and/or various buffers. Other adjuvants and modes of administration are well and widely known in the pharmaceutical art. For infections of the eye or other external tissues, e.g., mouth and skin, the formulations are preferably applied as a topical ointment or cream containing the active ingredient(s) in a total amount of, for example, 0.075 to 30% w/w, preferably 0.2 to 20% w/w and most preferably 0.4 to 15% w/w. When formulated in an ointment, the active ingredients may be employed with either paraffinic or a water-miscible ointment base. Alternatively, the active ingredients may be formulated in a cream with an oil-in-water cream base. If desired, the aqueous phase of the cream base may include, for example at least 30% w/w of a polyhydric alcohol such as propylene glycol, butane-1,3-diol, mannitol, sorbitol, glycerol, polyethylene glycol and mixtures thereof. The topical formulation may desirably include a compound which enhances absorption or penetration of the active ingredient through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogs. The compounds of this invention can also be administered by a transdermal device. Preferably topical administration will be accomplished using a patch either of the reservoir and porous membrane type or of a solid matrix variety. In either case, the active agent is delivered continuously from the reservoir or microcapsules through a membrane into the active agent permeable adhesive, which is in contact with the skin or mucosa of the recipient. If the active agent is absorbed through the skin, a controlled and predetermined flow of the active agent is administered to the recipient. In the case of microcapsules, the encapsulating agent may also function as the membrane. The oily phase of the emulsions of this invention may be constituted from known ingredients in a known manner. While the phase may comprise merely an emulsifier, it may comprise a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabilizer. It is also preferred to include both an oil and a fat. Together, the emulsifier(s) with or without stabilizer(s) make-up the so-called emulsifying wax, and the wax together with the oil and fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations. Emulsifiers and emulsion stabilizers suitable for use in the formulation of the present invention include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate, and sodium lauryl sulfate, among others The choice of suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the active compound in most oils likely to be used in pharmaceutical emulsion formulations is very low. Thus, the cream should preferably be a non-greasy, non-staining and washable product with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic alkyl esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters may be used. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or other mineral oils can be used. Formulations suitable for topical administration to the eye also include eye drops wherein the active ingredients are dissolved or suspended in suitable carrier, especially an aqueous solvent for the active ingredients. The antiviral active ingredients are preferably present in such formulations in a concentration of 0.5 to 20%, advantageously 0.5 to 10% and particularly about 1.5% w/w.

Claims: A compound of general Formula I selected from a group of compounds consisting of 5-methyl-2[1(1R)-1 phenylethyl]amino]-4H-3,1-benzoxazin-4-one; N α -(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-N ε -[(phenylmethoxy)carbonyl]-L-lysine, 1,1-dimethylethyl ester; N-(5-methyl-4-oxo-4H-3,1,-benzoxazin-2-yl)-L-phenylalanine, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-tryptophan, 1,1-dimethylethylester; 2-[[2-methoxy-(1 S)-(1-phenylmethyl)ethyl]amino]-5-methyl-4H-3,1-benzoxazin-4-one; 3,5-diiodo-N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2 yl)-L-tyrosine, methyl ester; N-(5-rnethyl-4-oxo-4H-3,1-benzoxazin-2-yl)-O-methyl-L-tyrosine, methyl ester; N-(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)-L-phenylglycine, 1,1-dimethylethyl ester; αS-[(5-methyl-4-oxo-4H-3,1-benzoxazin-2-yl)aminol-4-methoxy-N-methyl-N-(phenylmethyl)benzeneprapanamide; 5-methoxy-2-([(1R)-1-phenylethyl]amino]-4H-3,1-benzoxazin-4-one; and N-[5-methoxy-4-oxo-4H-3,1-benzoxazin-2-yl-O-methyl-L-tyrosine. N-methyl-N-phenylmethylamide, and the pharmaceutically acceptable salts of said selected compounds. A pharmaceutical composition comprising a therapeutically-effective amount of a compound according to claim 1 and a pharmaceutically-acceptable carrier or diluent. Use of a compound according to claim 1 for preparing a medicament for the treatment of a viral infection in a subject. Use of a compound according to claim 1 for preparing a medicament for inhibiting a viral protease. Use according to claim 3 wherein the viral infection is caused by a herpesvirus. Use according to claim 5 wherein the viral infection is caused by CMV, HSV-1 or HSV-2.

Inventors: ABOOD NORMAN, BAX BRIAN M, BECKER DANIEL P, BEDELL JOHN L, BENNETT MICHAEL J, FLYNN DANIEL L, LI HUI, NOSAL ROGER A, SCHRETZMAN LORI A, VILLAMIL CLARA I, WILLIAMS KENNETH, ABOOD, NORMAN, BAX, BRIAN M., BECKER, DANIEL P., BEDELL, JOHN L., BENNETT, MICHAEL J., FLYNN, DANIEL L., LI, HUI, NOSAL, ROGER A., SCHRETZMAN, LORI A., VILLAMIL, CLARA I.., WILLIAMS, KENNETH
Applicants: SEARLE & CO, G.D. SEARLE & CO.
Application year: 1996
Main classification: C07D265
IPC codes: C07D413, A61P31, C07D265