Title:  Compositions and methods for treatment of staphylococcal infection while suppressing formation of antibiotic-resistant strains

United States Patent:  6,569,830

Issued:  May 27, 2003

Inventors:  Climo; Michael (Richmond, VA); Murphy; Ellen (Bronx, NY); Archer; Gordon (Richmond, VA)

Assignee:  Ambi, Inc. (Purchase, NY)

Appl. No.:  263776

Filed:  March 5, 1999

Co-administration of a lysostaphin or other anti-staphylococcal agent which cleaves cross-links of peptidoglycans of staphylococci cell walls such as lysostaphin and an antibiotic effective against staphylococci due to antibiotic activity mediated by cell-wall activity is effective against staphylococcal infection, even staphylococci that may be resistant to one or other of lysostaphin or the cell-wall active antibiotic. Co-administration simultaneously suppresses the generation of antibiotic-resistant mutant strains. Effective cell-wall active antibiotics include .beta.-lactams and glycopeptides.

SUMMARY OF THE INVENTION

The above goals, and others made clear by the discussions set forth below, are achieved by the simultaneous administration of an anti-staphylococcal agent, such as lysostaphin or other agent whose activity is mediated by cleavage of glycine-containing cross-links in the staphylococcal cell wall peptidoglycan and an antibiotic or antimicrobial agent whose activity is mediated by its ability to affect the cell wall of staphylococci. These cell-wall active agents include .beta.-lactams and glycopeptides. Preferably, the cell-wall active antibiotic is a .beta.-lactam.

There is no evidence of any synergistic effect achieved through the simultaneous administration of an anti-staphyloccocal agent whose activity is mediated by cleavage of glycine-containing cross-links and a cell-wall active antibiotic in a model, in vitro or in vivo, that is predictive of benefit for in vivo administration of antibiotics in a mammal. Indeed, those of ordinary skill in the art will recognize that for resistant staphylococci, such as MRSA, the administration of methicillin is not therapeutically effective in any amount. Surprisingly, Applicants have discovered that the combined administration of an anti-staphyloccocal agent whose activity is mediated by cleavage of glycine-containing cross-links such as lysostaphin and the cell-wall active antibiotic not only effectively treats the infection, but suppresses the formation of staphylococci having resistance to the anti-staphylococcal agent whose activity is mediated by cleavage of glycine-containing cross-links.

While Applicants do not wish to be bound by this explanation, it appears that the spontaneous mutation commonly effective in conferring lysostaphin resistance in staphylococci renders the same highly susceptible to a cell-wall active antibiotic, such as methicillin. This is true even where the organism starts out as methicillin resistant. Simultaneous administration of both appears to be uniformly effective in simultaneously eradicating the infection and suppressing the generation of new resistant strains. Specifically, anti-staphylococcal agents like lysostaphin cleave glycine-containing cross-links. The mutation conferring resistance to this attack renders previously resistant strains sensitive to cell wall active antibiotics.

DETAILED DESCRIPTION OF THE INVENTION

This invention involves the administration of a pharmaceutical composition effective in the treatment of staphylococcal infection, which composition comprises at least two active agents, one an agent like lysostaphin which cleaves the glycine-containing cross-links of the cell wall peptidoglycans of staphylococci, the other a cell-wall active antibiotic. By lysostaphin it is intended to refer herein to any enzyme, including lysostaphin wild type, a mutant or variant, or any recombinant or related enzyme that retains proteolytic activity against glycine-containing cross-links in the cell wall peptidoglycan of staphylococci. Variants may be generated by post-translational processing of the protein (either by enzymes present in a producer strain or by means of enzymes or reagents introduced at any stage of the process) or by mutation of the structural gene. Mutations may include site-deletion, insertion, domain removal and replacement mutations. They may be recombinantly expressed, or otherwise. Other anti-staphylococcal active agents acting by cleavage of the glycine-containing peptidoglycan cross-links include lasA protease and achromopeptidase. Such anti-staphylococcal agents which affect the peptidoglycan cross-links are embraced by the invention, but exemplified herein by reference to lysostaphin.

Cell-wall active antibiotics include .beta.-lactams and glycopeptides. .beta.-lactams are preferred. Suitable .beta.-lactams include, but are not limited to, penicillins, such as penicillin, nafcillin, oxacillin, methicillin, amoxicillin and cloxacillin. Other .beta.-lactams include cephalosporins and carbapenems. Representative cephalosporins include cephalothin, cefazolin, cefamandole, ceftazidime and others. Suitable carbapenems include imepenem and meropenem.

Suitable glycopeptides include vancomycin, teicoplanin and ramoplanin.

These two agents can be combined with further agents, adjuvants and the like, but are effectively administered in a pharmaceutically acceptable carrier. Administration is typically systemic, and may be intravenous (IV), intramuscular (IM), subcutaneous (SC), intraperitoneal (IP), intrathecal or topical. No synergistic effect of combining lysostaphin and a .beta.-lactam or glycopeptide or cell-wall active antibiotic has been noted in a model predictive of in vivo mammalian administration. Accordingly, each agent of the effective combination must be administered in a therapeutically effective amount. It is to be noted, in this regard, that the amount to be administered is that which is therapeutically effective when the lysostaphin and cell-wall active agent are administered together. Those of skill in the art will of course recognize that there is no therapeutically effective amount for, e.g.,methicillin if the staphylococcal infection is an MRSA infection. Nonetheless, administration of therapeutic amounts of methicillin as determined against non-MRSA, combined with an amount of lysostaphin effective against staphylococci that are not lysostaphin-resistant will effectively treat staphylococcal infections even where the infection is resistant to one or other antibiotic. Accordingly, applicants have referred herein to "therapeutically effective amounts" to mean amounts effective to therapeutically treat sensitive S. aureus infection. This simultaneous administration, as opposed to sequential administration typified by the prior art, also surprisingly results in the suppression of strains resistant against either antibiotic, or their combination.

Any of a wide variety of pharmaceutically acceptable carriers and diluents, typically buffered, may be used. Appropriate pharmaceutical carriers are known to those of skill in the art. The formulations of this invention comprise a therapeutic amount of lysostaphin and a therapeutic amount of a cell-wall active antibiotic, such that when co-administered, the staphylococcal infection, either S. aureus or coagulase negative staphylococci, is treated, while the generation of resistant strains is suppressed. Other active agents that do not interfere with the activity of the two antibiotics may be co-administered.

Therapeutic values will range substantially given the nature of the staphylococcal infection, the individual, and the antibiotic being used in conjunction with lysostaphin. Representative values for anti-staphyloccocal active agents such as lysostaphin, range from approximately 15-150 mg/kg body weight/day for human administration, with a preferred range of 25-100 mg/kg/day. Values for .beta.-lactams based on nafcillin range from 50-250 mg/kg/day, with a preferred range of 100-220 mg/kg/day and glycopeptides like vancomycin are administered over a range of 10-75 mg/kg/day, with a preferred range of 15-50 mg/kg/day.

The administration course is not substantially different from that currently administered in single antibiotic treatments, and can range from 7-28 days, although typically, courses of 7-21 days are employed, and effective in treating a wide variety of staphylococcal infections.

Claim 1 of 10 Claims

What is claimed is:

1. A pharmaceutical composition in dosage form for treating a staphylococcal infection in a human subject, said composition comprising:

lysostaphin in an amount of from 15 to 150 mg/kg body weight of the human subject; and

a .beta.-lactam antibiotic in an amount of from 50 to 250 mg/kg body weight of the human subject,

wherein said composition, when administered to the human subject for a period of time sufficient to eradicate said infection, suppresses formation of staphylococcal strains resistant to said lysostaphin, said cell-wall active antibiotic and said composition, and wherein said amount of lysostaphin is an amount effective in treating, in a human, a staphylococcal infection that is not lysostaphin-resistant and wherein said amount of the cell-wall active antibiotic is an amount effective in treating, in a human, a staphylococcal infection that is not resistant to the cell-wall active antibiotic.

 

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.