Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Radical -xh acid – or anhydride – acid halide or salt thereof...
Reexamination Certificate
2001-07-20
2003-04-08
Weddington, Kevin E. (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Radical -xh acid, or anhydride, acid halide or salt thereof...
Reexamination Certificate
active
06545051
ABSTRACT:
This invention relates to the use of hydroxamic acid derivatives as antibacterial agents.
BACKGROUND TO THE INVENTION
In general, bacterial pathogens are classified as either Gram-positive or Gram-negative. Many antibacterial agents (including antibiotics) are specific against one or other Gram-class of pathogens. Antibacterial agents effective against both Gram-positive and Gram-negative pathogens are therefore generally regarded as having broad spectrum activity.
Many classes of antibacterial agents are known, including the penicillins and cephalosporins, tetracyclines, sulfonamides, monobactams, fluoroquinolones and quinolones, aminoglycosides, glycopeptides, macrolides, polymyxins, lincosamides, trimethoprim and chloramphenicol. The fundamental mechanisms of action of these antibacterial classes vary.
Bacterial resistance to many known antibacterials is a growing problem. Accordingly there is a continuing need in the art for alternative antibacterial agents, especially those which have mechanisms of action fundamentally different from the known classes.
Amongst the Gram-positive pathogens, such as Staphylococci, Streptococci, Mycobacteria and Enterococci, resistant strains have evolved/arisen which makes them particularly difficult to eradicate. Examples of such strains are methicillin resistant
Staphylococcus aureus
(MRSA), methicillin resistant coagulase negative Staphylococci (MRCNS), penicillin resistant
Streptococcus pneumoniae
and multiply resistant
Enterococcus faecium.
Pathogenic bacteria are often resistant to the aminoglycoside, &bgr;-lactam (penicillins and cephalosporins), and chhloramphenicol types of antibiotic. This resistance involves the enzymatic inactivation of the antibiotic by hydrolysis or by formation of inactive derivatives. The &bgr;-lactam (penicillin and cephalosporin) family of antibiotics are characterised by the presence of a &bgr;-lactam ring structure. Resistance to this family of antibiotics in clinical isolates is most commonly due to the production of a “penicillinase” (&bgr;-lactamase) enzyme by the resistant bacterium which hydrolyses the &bgr;-lactam ring thus eliminating its antibacterial activity.
Recently there has been an emergence of vancomycin-resistant strains of enterococci (Woodford N. 1998 Glycopeptide-resistant enterococci: a decade of experience. Journal of Medical Microbiology. 47(10):849-62). Vancomycin-resistant enterococci are particularly hazardous in that they are frequent causes of hospital based infections and are inherently resistant to most antibiotics. Vancomycin works by binding to the terminal D-Ala-D-Ala residues of the cell wall peptidioglycan precursor. The high-level resistance to vancomycin is known as VanA and is conferred by a genes located on a transposable element which alter the terminal residues to D-Ala-D-lac thus reducing the affinity for vancomycin.
In view of the rapid emergence of multidrug-resistant bacteria, the development of antibacterial agents with novel modes of action that are effective against the growing number of resistant bacteria, particularly the vancomycin resistant enterococci and &bgr;-lactam antibiotic-resistant bacteria, such as methicillin-resistant
Staphylocccus aureus
, is of utmost importance.
The natural antibiotic actinonin (see for example J. C. S Perkin I, 1975, 819) is a hydroxamic acid derivative of Structure (A):
In ddition to actinonin, various structural analogues of actinonin have also been shown to have antibacterial activity (see for example Broughton et al. (Devlin et al. Journal of the Chemical Society. Perkin Transactions 1 (9):830-841, 1975; Broughton et al. Journal of the Chemical Society. Perkin Transactions 1 (9):857-860, 1975).
The matlystatin group of compounds, share a number of structural similarities with actinonin. Both are peptidic molecules with functional hydroxamic acid metal binding groups (Ogita et al., J. Antibiotics. 45(11):1723-1732; Tanzawa et al., J. Antibiotics. 45(11):1733-1737; Haruyama et al., J. Antibiotics. 47(12):1473-1480; Tamaki et al., J. Antibiotics. 47(12):1481-1492).
Since this invention is concerned with the use of hydroxamic acid derivatives, it is noted that many hydroxamic acid derivatives have previously been disclosed as inhibitors of matrix metalloproteinases (MMP), enkephalinase, angiotensin and other natural enzymes which play various roles in several human disease states. (For a review of the compounds known in the MMP inhibitor context, see Beckett, Exp. Opin. Ther. Patents (1996) 6:1305-1315 and Beckett & Whittaker, Ibid. (1998) 8(3):250-282). However, it appears the only hydroxamic acid derivatives previously disclosed as having antibacterial activity are the actinonin and matlystatin classes referred to above.
BRIEF DESCRIPTION OF THE INVENTION
WO 98/11063 and WO 99/46241 (British Biotech) disclose the use of certain ester and thioester compounds containing a hydroxamic acid group as inhibitors of the proliferation of rapidly dividing tumour cells, and claim that use together with a class of such esters and thioesters per se. This invention is based on the finding that a subset of the ester and thioester compounds containing a hydroxamic acid group with which WO 98/11063 and WO 99/46241 are concerned have antibacterial activity, against members of the Gram-positive and/or Gram-negative classes.
Although it may be of interest to establish the mechanism of action of the compounds with which the invention is concerned, it is their ability to inhibit bacterial growth that makes them useful. However, it is presently believed that their antibacterial activity is due, at least in part, to intracellular inhibition of bacterial polypeptide deformylase (PDF; EC 3.5.1.31).
All ribosome-mediated synthesis of proteins starts with a methionine residue. In prokaryotes the methionyl moiety carried by the initiator tRNA is N-formylated prior to its incorporation into a polypeptide. Consequently, N-formylmethionine is always present at the N-terminus of a nascent bacterial polypeptide. However, most mature proteins do not retain the N-formyl group or the terminal methionine residue. Deformylation is required prior to methionine removal, since methionine aminopeptidase does not recognise peptides with an N-terminal formylmethionine residue (Solbiati et al., J. Mol. Biol. 290:607-614, 1999). Deformylation is, therefore, a crucial step in bacterial protein biosynthesis and the enzyme responsible, PDF, is essential for normal bacterial growth. Although the gene encoding PDF (def) is present in all pathogenic bacteria for which sequences are known (Meinnel et al., J. Mol. Biol, 266:939-49, 1997), it has no eukaryotic counterpart, making it an attractive target for antibacterial chemotherapy.
The isolation and characterisation of PDF has been facilitated by an understanding of the importance of the metal ion in the active site (Groche et al., Biophys. Biochem. Res. Commun., 246:324-6, 1998). The Fe
2+
form is highly active in vivo but is unstable when isolated due to oxidative degradation (Rajagopalan et al., J. Biol. Chem. 273:22305-10, 1998). The Ni
2+
form of the enzyme has specific activity comparable with the ferrous enzyme but is oxygen-insensitive (Ragusa et al., J. Mol. Biol. 1998, 280:515-23, 1998); The Zn
2+
enzyme is also stable but is almost devoid of catalytic activity (Rajagopalan et al., J. Am. Chem. Soc. 119:12418-12419, 1997).
Several X-ray crystal structures and NMR structures of
E. coli
PDF, with or without bound inhibitors, have been published (Chan et al., Biochemistry 36:13904-9, 1997; Becker et al., Nature Struct. Biol. 5:1053-8, 1998; Becker et al., J. Biol. Chem. 273:11413-6, 1998; Hao et al., Biochemistry, 38:4712-9, 1999; Dardel et al., J. Mol. Biol. 280:501-13, 1998; O'Connell et al., J. Biomol. NMR, 13:311-24, 1999), indicating similarities in active site geometry to metalloproteinases such as thermolysin and the metzincins.
Recently the substrate specificity of PDF has been extensively studied (Ragusa et al., J. Mol. Biol. 289:1445-57, 1999; Hu et al., Biochemistry 38:643
Beckett Raymond Paul
Clements John Martin
Hunter Michael George
Whittaker Mark
Banner & Witcoff , Ltd.
British Biotech Pharmaceuticals Ltd.
Weddington Kevin E.
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