Meloxicam (5), an NSAID in the enol-carboxamide class, was developed on the basis of its antiinflammatory activity and relative safety in animal models. In subsequent screening in microsomal assays using human COX-1 and COX-2, we discovered that it possessed a selectivity profile for COX-2 superior to piroxicam and other marketed NSAIDs. We therefore embarked on a study of enol-carboxamide type compounds to determine if COX-2 selectivity and potency could be dramatically improved by structural modification. Substitution at the 6- and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification were all examined. In addition we explored several related systems including the isomeric 3-oxo-1,2-benzothiazine-4-carboxamides, thienothiazines, indolothizines, benzothienothiazines, naphthothiazines, and 1,3- and 1,4-dioxoisoquinolines. While a few examples were found with greater potency in the COX-2 assay, no compound tested had a better COX-2/COX-1 selectivity profile than that of 5.

A series of tripeptides possessing trifluoromethyl or aryl ketone residues at P1 were prepared and evaluated both in vitro and in vivo as potential inhibitors of human leukocyte elastase (HLE). Tripeptides containing non naturally occurring N-substituted glycine residues at the P2-position have been demonstrated to be potent in vitro inhibitors of HLE, with IC50 values in the submicromolar range. Sterically demanding substituents on the P2-nitrogen have no detrimental effect on in vitro potency. The inhibition process presumably acts via hemiketal formation with the active site Ser195 of HLE, and is facilitated by the strongly electron withdrawing trifluoromethyl functionality. Deletion of the amino acid at the P3-subsite region affords inactive compounds. Valine is the preferred residue at the P1-position, whereas the corresponding glycine, alanine, alpha,alpha-dimethylglycine, or phenylalanine analogues are all inactive. The compounds described herein all confer a high degree of in vitro specificity when tested against representative cysteine, aspartyl, metallo, and other serine proteases. One of the most potent in vitro inhibitors is (3RS)-N-[4-[[[(4-chlorophenyl)sulfonyl]amino]carbonyl]phenyl] oxomethyl]-L-valyl-N-(2,3-dihydro-1H-inden-2-yl)glycine N-[3-(1,1,1-trifluoro-4-methyl-2-oxopentyl)]amide (20i; BI-RA-260) (IC50 = 0.084 microM). Compound 20i was also tested in hamsters in an elastase-induced pulmonary hemorrhage (EPH) model. In this model, intratracheal (it.) administration of 20i, 5 min prior to HLE challenge, effectively inhibited hemorrhage in a dose-dependent manner with an ED50 of 4.8 micrograms. The inhibitor 20i, 20 micrograms administered it. 24, 48, and 72 h prior to HLE challenge, exhibits significant inhibition against hemorrhage at all time points (97%, 64% and 49%, respectively). In a 21-day chronic model of emphysema in hamsters, 200 micrograms of HLE administered it. caused an elastase-induced emphysema in the lungs which can be quantitated histologically utilizing image analysis. In this assay, 20i significantly inhibited pulmonary lesions associated with septal destruction and increased alveolar spaces, when dosed at 20 micrograms it. 5 min prior to challenge with HLE.

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A novel class of lymphocyte function-associated antigen-1 (LFA-1) inhibitors is described. Discovered during the process to improve the physicochemical and metabolic properties of BIRT377 (1, Figure 1), a previously reported hydantoin-based LFA-1 inhibitor, these compounds are characterized by an imidazole-based 5,5-bicyclic scaffold, the 1,3,3-trisubstituted 1H-imidazo[1,2-alpha]imidazol-2-one (i.e. structure 3). The structure-activity relationship (SAR) shows that electron-withdrawing groups at C5 on the imidazole ring benefit potency and that oxygen-containing functional groups attached to a C5-sulfonyl or sulfonamide group further improve potency. This latter gain in potency is attributed to the interaction(s) of the functionalized sulfonyl/sulfonamide groups with the protein, likely polar-polar in nature, as suggested by SAR data. X-ray studies revealed that these bicyclic inhibitors bind to the I-domain of LFA-1 in a pattern similar to that of compound 1.

A series of tripeptides which contain alpha,alpha-difluorostatone residues at P1-P1' and span the S3-S1' subsites have been shown to be potent inhibitors of human leukocyte elastase (HLE). The tripeptides described contain the nonproteinogenic achiral residue N-(2,3-dihydro-1H-inden-2-yl)glycine at the P2-position. This redidue has previously been shown in the case of HLE to be a good bioisosteric replacement for L-proline. Of the peptides prepared, those which contain the alpha,alpha-difluoromethylene keton derivative of L-valine (difluorostatone) are the preferred residue at the P1-primary specificity position. Substitution at P1 by the corresponding alpha,alpha-difluoromethylene ketones of L-leucine and L-phenylalanine gives inactive compounds. Of the tripeptides described the most potent in vitro compound is ethyl N-[N-CBZ-L-valyl-N-(2,3-dihydro-1H-inden-2-yl)glycyl]- 4(S)-amino-2,2-difluoro-3-oxo-5-methylhexanoate (17B) (IC50 = 0.635 microM). It is presumed that the inhibitor 17b interacts with the S3-S1' binding regions of HLE. Additionally extended binding inhibitors were prepared which interact with the S3-S3' binding subsites of HLE. In order to effect interaction with the S1'-S3' subsites of HLE, the leaving group side of cleaved peptides, spacers based upon Gly-Gly, and those linked via the N epsilon of L-lysine were utilized. One of the most potent extended compounds (P3-P3') in vitro is methyl N6-[4(S)-[[N-[N-CBZ-L-valyl-N- (2,3-dihydro-1H-inden-2-yl)glycyl]amino]-2,2-difluoro-3-oxo-5- methylhexanoyl]-2(S)-(acetylamino)-6-aminohexanoate (24b) (IC50 = 0.057 microM). The described in vitro active inhibitors were also evaluated in hamsters in an elastase-induced pulmonary hemorrhage (EPH) model. In this model, intratracheal (it.) administration of 22c, 5 min prior to HLE challenge (10 micrograms, it.) effectively inhibited hemorrhage (94.6%) in a dose-dependent manner. The described alpha,alpha-difluoromethylene ketone inhibitors are assumed to act as transition-state analogs. The inhibition process presumably acts via hemiketal formation with the active site Ser195 of HLE, and is facilitated by the strongly electron withdrawing effect of the alpha,alpha-difluoromethylene functionality.