Dalbavancin compositions for treatment of bacterial infections   

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. Nos. 60/427,654, filed Nov. 18, 2002, 60/485,694, filed Jul. 8, 2003, 60/495,048, filed Aug. 13, 2003, and 60/496,483, filed Aug. 19, 2003, the disclosures of all of which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to dalbavancin compositions and, in particular, to multimeric forms of dalbavancin. This invention further relates to the use of such multimers in the treatment of bacterial infections.

2. State of the Art

According to the U.S. Center for Disease Control and Prevention, nosocomial bloodstream infections are a leading cause of death in the United States. Approximately five percent of the seven million central venous catheters (CVCs) inserted annually in the United States are associated with at least one episode of bloodstream infection (approximately 350,000 a year). Catheter-related bloodstream infections occur when bacteria enter the bloodstream through an intravenous catheter and can be life threatening.

Skin and soft tissue infections (SSTIs) are a common medical condition and often the consequence of trauma or surgical procedures. Staphylococcus aureus and Streptococcus pyogenes are the pathogens most frequently isolated from patients with deep tissue infections, although any pathogenic organism, including those found on healthy skin, may cause infection. Many SSTIs are mild to moderate in severity, permitting successful treatment with oral antimicrobial agents and local cleansing. In contrast, more severe or complicated infections, which frequently occur in patients with underlying risk factors (e.g., vascular compromise, diabetes) and/or infections caused by difficult-to-treat or multiply-resistant bacteria, may require potent intravenous antimicrobial therapy and aggressive surgical debridement.

Staphylococci are a clinical and therapeutic problem and have been increasingly associated with nosocomial infections since the early 1960s. The coagulase-positive species methicillin-resistant Staphylococcus aureus (MRSA) has long been problematic in both community-acquired and nosocomial infections, and several coagulase-negative staphylococci have been recognized as opportunistic human pathogens, especially in the treatment of critically ill patients in intensive care units. Another major cause for clinical concern is the increasing isolation of penicillin-resistant Streptococcus pneumoniae strains in many parts of the world.

The glycopeptide antibiotics vancomycin and teicoplanin have been used against serious nosocomial infections caused by multi-drug-resistant Gram-positive pathogens, particularly MRSA, coagulase-negative staphylococci (CoNS), and enterococci. Vancomycin and teicoplanin are used for infections caused by MRSA, and until recently, all isolates were uniformly susceptible. However, the isolation of Staphylococcus aureus strains with intermediate susceptibility or resistance to teicoplanin as well as vancomycin has now been reported with increasing frequency. A number of vancomycin-resistant strains, classified “VanA,” “VanB,” or “VanC,” based on the mechanism of resistance, have been reported. Thus, alternative treatment options are needed.

Teicoplanin is at least as active as vancomycin against most Gram-positive bacteria and appears to cause fewer adverse events. Both forms of treatment require at least once daily dosing to effect complete recovery. Currently, the therapeutic options for severe infections caused by some of these pathogens is quite limited. The emerging resistance of Gram-positive pathogens to vancomycin makes the availability of new antibiotics with potential for increased effectiveness highly desirable.

In addition, less frequent dosing regimens than currently-available therapies would be desirable to enhance patient comfort, especially for parenteral, e.g., intravenous or intramuscular, antibiotic administration. Hospital stays are sometimes necessitated by the need for multi-daily antibiotic administration by parenteral means, and less frequent dosing would be advantageous to permit such treatment to be done on an outpatient basis.

Although less frequent dosing is a desirable feature of an antibiotic administration regimen, the “pharmaceutical window,” i.e., the toxicity profile, of the administered antibiotic must be sufficiently acceptable to permit a large single dose to be administered without jeopardizing treatment by causing severe adverse reactions in the treated patient. Further, even when an antibiotic exhibits a suitable pharmaceutical window, less frequent dosing is possible only if the antibiotic exhibits a suitable serum half-life to maintain therapeutic effectiveness over the dosing interval desired. The serum half-life of an antibiotic dictates both the longevity of a drug in vivo and the length of time after administration when the serum level will reach a minimum trough level which is still bactericidally effective. The serum trough level over time after administration of a first dose of antibiotic dictates when a further dose must be administered to retain a minimum bactericidal level of the antibiotic in vivo.

In view of the above, an antibiotic possessing activity against one or more antibiotic resistant bacterial strains, particularly MRSA, which could be administered at a dosing interval of once every 5-7 days or longer, would be of commercial value and would satisfy a long-felt need in the art.

SUMMARY

This invention is directed to the discovery that monomeric dalbavancin reversibly forms a multimer in aqueous solutions wherein the ratio of multimer to monomer increases with higher pH and lower salt concentration.

As pH increases, dalbavancin solubility in aqueous formulations decreases. On the other hand, at pHs below about 3, dalbavancin is typically unstable by virtue of hydrolysis of amide bond(s) and at pHs above about 5.5, dalbavancin is insoluble. Thus, a pH narrow window is available for solubilizing dalbavancin for delivery in vivo.

The solubility of dalbavancin becomes of particular importance because dalbavancin is typically administered intravenously typically from a sterile aqueous solution comprising, e.g., dextrose. Under these circumstances, it is preferred to use solutions with a pH as close to physiological pH as possible. However, solubility considerations require that the solution has a pH of about 3 to 5.5 and typically at about 4.5. At these conditions, it has been found that a large population of the dalbavancin exists in multimeric form.

It has also been found, however, that upon administration in vivo, monomeric dalbavancin binds to endogenous protein to form either a 1:1 protein:dalbavancin complex or a 1:2 protein:dalbavancin complex. In the latter case and without being limited to any theory, it is believed that this complex is, in fact, binding of two monomers of dalbavancin to one protein molecule.

It has now been found that multimeric dalbavancin forms a depot for monomeric dalbavancin when administered to the patient as described above. This is particularly surprising since, when administered, the aqueous dalbavancin composition encounters a much higher pH at physiological conditions which would suggest that even higher populations of multimer are likely to be formed. Accordingly, in one of its composition aspects, this invention is directed to an aqueous composition comprising dalbavancin and dextrose wherein said composition comprises a mixture of dalbavancin monomers and multimers. In another of its composition aspects, this invention is directed to an aqueous composition comprising dalbavancin and deionized water wherein said composition comprises a mixture of dalbavancin monomers and multimers. In another composition aspect, the invention is directed to an aqueous composition comprising dalbavancin and a stabilizer wherein said composition comprises a mixture of dalbavancin monomers and multimers. In yet another composition aspect, the invention is directed to an aqueous composition comprising dalbavancin, dextrose, deionized water, and a stabilizer other than dextrose wherein said composition comprises a mixture of dalbavancin monomers and multimers.

In one preferred embodiment, the aqueous composition is deionized.

In another preferred embodiment, the pH of the aqueous solution is at least about 4.0 and preferably from about 4.0 to about 5.5 and most preferably at about 4.5.

In still another preferred embodiment, the ratio of multimer to monomer in solution is preferably at least about 2:1 and more preferably from about 2:1 to about 8:1 and often from about 4:1 to about 8:1, more often from about 6:1 to about 8:1 and still more often from about 6:1 to about 7:1.

The invention provides compositions, methods and kits for treatment or prevention of a bacterial infection with dalbavancin. Surprisingly, stabilized formulations of dalbavancin have been found to exhibit both a pharmaceutical window as well as a prolonged serum half-life to permit treatment regimens of about once every 5-7 days or longer, while retaining antibacterial properties in vivo.

Accordingly, in one aspect, a pharmaceutical composition is provided that includes a unit dose of dalbavancin in an amount sufficient to provide a therapeutically or prophylactically effective plasma level of dalbavancin in an individual for at least five days, a stabilizer, and a pharmaceutically acceptable carrier.

Pharmaceutical compositions of the invention are generally formulated in a pharmaceutically acceptable form for administration to an individual, such as a pharmaceutically acceptable aqueous formulation. Such pharmaceutical compositions are preferably administered by parenteral, e.g., intravenous or intramuscular, routes. Accordingly, in this preferred embodiment, these pharmaceutical compositions are typically sterile.

In some embodiments, a unit dose of dalbavancin is provided in dry powder (e.g., lyophilized) form and reconstituted in a pharmaceutically acceptable carrier, such as a sterile aqueous formulation, prior to administration to an individual. In one embodiment, the pharmaceutically acceptable carrier includes 5% dextrose in water. A pharmaceutical composition of the invention may be administered to a mammal in need of treatment or prevention of a bacterial infection, such as a human. In some embodiments, a pharmaceutical composition may include at least one antibiotic that is not dalbavancin, such as an antibiotic that is effective (e.g., bactericidal) against a Gram-negative bacterium and/or an antibiotic that is effective against Gram-positive species against which dalbavancin is not effective, such as VanA vancomycin-resistant bacterial strains.

One or more stabilizing substances are employed to inhibit degradation of one or more dalbavancin components during storage as a dry powder (e.g., lyophilized) formulation and/or as an aqueous formulation prior to administration to an individual. Over time, degradation can result in the undesirable formation of less active and/or inactive components which could potentially cause adverse effects in vivo. Preferred stabilizers include nonionic components such as sugars or sugar alcohols, e.g., a mono-, di-, or polysaccharide, or derivative thereof, such as, for example, mannitol, lactose, sucrose, sorbitol, glycerol, cellulose, trehalose, maltose, or dextrose, or mixtures thereof.

In another aspect, methods are provided for treating a bacterial infection in an individual in need thereof, including administering at least one unit dose of dalbavancin in an amount sufficient to provide a therapeutically effective plasma level of dalbavancin in the individual for at least five days, and a pharmaceutically acceptable carrier. A therapeutically effective plasma level of dalbavancin is generally at least about 4 mg of dalbavancin per liter of plasma. In one embodiment, the dosage amount of dalbavancin administered is an amount that is clinically effective and also has reduced adverse side effects in comparison to the standard of care with drugs such as teicoplanin and vancomycin.

Dalbavancin may be administered as a single dose or as multiple doses. In some embodiments, a single dose of about 100 mg to about 4000 mg, for example 3000 mg, of dalbavancin is administered. In various embodiments, a single dalbavancin dose may include at least about any of 0.1, 0.25, 0.5, 1, 1.5, 2, 2.5, or 3 grams.

In other embodiments, two doses are administered about five to about ten days apart, such as about one week apart. The first dose may be about 500 to about 5000 mg of dalbavancin and the second dose may be about 250 mg to about 2500 mg of dalbavancin. Often, the first dose includes at least about twice as much of the amount of dalbavancin contained in the second dose. For example, the first dose may be about 1000 mg and the second dose may be about 500 mg of dalbavancin. In methods in which two doses are administered, the plasma trough level of dalbavancin in an individual prior to administration of the second dose is generally at least about 4 mg, often at least about 10 mg, often at least about 20 mg, more often at least about 30 mg dalbavancin per liter of plasma, and still more often at least about 40 mg dalbavancin per liter of plasma.

Often, methods of the invention include parenteral administration, for example, intravenous administration. In some embodiments, administration is intravenous with the rate of administration controlled such that administration occurs over at least about 30 minutes or longer.

Methods of the invention may be used to treat a Gram-positive bacterial infection, such as, for example, a Staphylococcus aureus or Streptococcus pyogenes skin and soft tissue infection. In some embodiments, the infection is penicillin-resistant and/or multi-drug resistant.

In another aspect, a method for preventing a bacterial infection is provided which includes administering an aqueous composition comprising dalbavancin and dextrose wherein said composition comprises a mixture of dalbavancin monomers and multimers. Preferably, the amount of dalbavancin administered is an amount sufficient to provide a prophylactically effective plasma level of dalbavancin in the individual for at least five days, often at least one week, often at least ten days or longer, and a pharmaceutically acceptable carrier. The dosage of dalbavancin may be, for example, about 100 mg to about 1000 mg. In some embodiments, dalbavancin is administered prior, during, or subsequent to a medical procedure or a stay in the hospital.

Therapeutic or prophylactic methods of the invention may include administration of at least one antibiotic that is not dalbavancin, preferably an antibiotic that is effective against a Gram-negative bacterium and/or an antibiotic that is effective against Gram-positive strains that dalbavancin is not effective against, such as VanA strains.

In another aspect, kits are provided that include a first and a second dose of a composition comprising a mixture of dalbavancin monomers and multimers and a stabilizer, wherein the amount of the second dose is about half or less than the amount of the first dose and wherein the kit further comprises instructions for use in the treatment of a bacterial infection. In yet another aspect, kits are provided that include a mixture of dalbavancin monomers and multimers, a stabilizer, and a non-dalbavancin antibiotic. Kits may contain two unit dosages, with a second dosage including about half or less of the amount of dalbancin included in a first dose. Kits may also include an antibiotic that is not dalbavancin, preferably effective against a Gram-negative bacterium.

In one embodiment, kits are provided that include a first container containing a dry powder (e.g., lyophilized) dalbavancin composition and a second container containing a predetermined amount of a physiologically acceptable aqueous solution for admixing with the dalbavancin composition. Such solutions are preferably sterile aqueous solutions. In one embodiment, kits include a delivery means for administering the dalbavancin composition to an individual, for example a syringe or intravenous administration means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts dalbavancin plasma concentration versus time following a single 1000 mg intravenous infusion of dalbavancin.

FIG. 2 depicts isothermal titration calorimetry data for dalbavancin binding to human serum albumin (top) and a graphical representation of the data fitted to a curve determined from a 2:1 binding model of dalbavancin:protein (bottom).

FIG. 3 depicts an electrospray ionization mass spectrum of dalbavancin.

FIG. 4 is a graph of dalbavancin concentration vs. population ratio of dalbavancin multimer to monomer and depicts an increase in population ratio of dalbavancin multimer to monomer with increasing dalbavancin concentration.

FIG. 5 is a graph of pH vs. population ratio of dalbavancin multimer to monomer and depicts an increase in population ratio of dalbavancin multimer to monomer with increasing pH.

FIG. 6 depicts an electrospray ionization mass spectrum of dalbavancin in an ammonium formate 5 mM pH 5 solution.

FIG. 7 depicts an electrospray ionization mass spectrum of dalbavancin in an ammonium formate 50 mM pH 5 solution.

FIG. 8 depicts an electrospray ionization mass spectrum of dalbavancin in an ammonium formate 100 mM pH 5 solution.

FIG. 9 depicts an electrospray ionization mass spectrum of teicoplanin (50 μg/mL) in water.

FIG. 10 depicts an electrospray ionization mass spectrum of teicoplanin (100 μg/mL) in water.

FIG. 11 depicts the effect of HSA on the apparent dissociation constant for dalbavancin/tri-peptide binding at 26° C. (pH 7.4).

FIG. 12 depicts a comparison of isothermal calorimetry (ITC) data for binding of tri-peptide to vancomycin and dalbavancin under identical conditions, using the same tri-peptide solution.

FIGS. 13A and 13B depict the possible interaction of dalbavancin monomers and multimers (including dimers) with tri-peptide ligand and HSA.

FIG. 13(A) depicts dalbavancin in monomer-dimer equilibrium in solution, binding as monomer to two separate sites on HSA; FIG. 13(B) depicts ligand binding to dalbavancin dimer in solution and more weakly to dalbavancin monomers attached to HSA.

DETAILED DESCRIPTION

The present invention provides improved dosage regimes and novel compositions of dalbavancin, and improved methods of treatment of antibiotic-resistant bacterial infections. In particular, the invention provides dalbavancin compositions having activity against one or more antibiotic resistant strains of bacteria, such as MRSA, which may be administered in a dosing regimen of once every 5-7 days or longer.

Dalbavancin, which is also referred to in the scientific literature as BI 397 or VER001, is a semi-synthetic glycopeptide mixture, the properties of which have been reported in U.S. Pat. Nos. 5,606,036, 5,750,509, 5,843,679, and 5,935,238.

As used herein, the term “dalbavancin” refers to compositions comprising one or more, preferably two or more, closely related homologs, termed “A0,” “A1,” “B0,” “B1,” “C0,” and “C1,” as described below, or monomers, multimers (i.e., dimer or higher order multimer), tautomers, esters, solvates, or pharmaceutically acceptable salts thereof. As used herein, “dimer” or “multimer” refers to either a homodimer or homomultimer, i.e., a dimer or multimer composed of monomers of the same dalbavancin homolog, or a heterodimer or heteromultimer, i.e., a dimer or multimer composed of monomers of at least two different dalbavancin homologs. Dalbavancin often includes “MAG,” a non-homolog variant described below. Individually, dalbavancin homologs and MAG are sometimes referred to herein as “dalbavancin components.”

Dalbavancin is prepared by chemical modification of the natural glycopeptide complex A-40,926 as described in Malabarba and Donadio (1999) Drugs of the Future 24(8):839-846. The predominant component of dalbavancin is Factor B0, which accounts for >75% of the whole complex.

The amount of each of the components present in a dalbavancin composition is dictated by a variety of factors, including, for example, the fermentation conditions employed in the preparation of the natural glycopeptide complex A-40926, which is the precursor to dalbavancin (see, e.g., U.S. Pat. No. 5,843,679), the conditions employed to recover A-40926 from the fermentation broth, the chemical reactions employed to selectively esterify the carboxyl group of the sugar moiety of A-40926, the conditions employed to amidate the peptidyl carboxyl group, the conditions employed to saponify the ester of the carboxyl group of the N-acylaminoglucuronic acid function, the conditions employed to recover dalbavancin from the synthetic mixture, and the like.

In preferred embodiments, dalbavancin compositions comprise at least about 80 to about 98% by weight of the B0 component. In particularly preferred embodiments, dalbavancin comprises the following amounts of B0:

TABLE 1 Preferred Amounts of B0 Component in Dalbavancin Composition Preferred1 More Preferred1 Even More Preferred1 80-98 80-97 80-96 81-98 81-97 81-96 82-98 82-97 82-96 83-98 83-97 83-96 84-98 84-97 84-96 85-98 85-97 85-96 86-98 86-97 86-96 87-98 87-97 87-96 88-98 88-97 88-96 89-98 89-97 89-96 90-98 90-97 90-96 1each range represents the mole % of Bo relative to the total dalbavancin components present in the dalbavancin composition including MAG

The chemical structure of several of the dalbavancin components is depicted in Formula I below:

I Dalbavancin Component R Molecular Weight Ao —CH(CH3)2 1802.7 A1 —CH2CH2CH3 1802.7 Bo —CH2CH(CH3)2 1816.7 B1 —CH2CH2CH2CH3 1816.7 C0 —CH2CH2CH(CH3)2 1830.7 C1′ —CH2CH2CH2CH2CH3 1830.7

All of the above dalbavancin components are bactericidally active against a number of Gram-positive bacteria. However, one non-homologous dalbavancin component, termed “MAG,” which lacks an acylglucoronamine moiety present in other components, is less bactericidally effective, both in vivo and in vitro, than other dalbavancin components. MAG is thought to be a decomposition product of one or more of the other dalbavancin components. Accordingly, in a preferred embodiment, the amount of MAG in dalbavancin is less than about 4, 3.5, 3, 2.5, 2, 1.5, 1, or 0.5 mole percent of all dalbavancin components present, including MAG.

Dalbavancin is thought to inhibit the biosynthesis of the bacterial cell wall by binding to D-alanyl-D-alanine-terminating precursors of peptidoglycans. Dimeric or higher order multimers of dalbavancin may possess further antibacterial properties by interaction of the lipophilic side chains with the cytoplasmic membrane of bacteria. See, for example, Malabarba and Ciabatti, et al. (2001) Current Medicinal Chemistry 8:1759-1773.

In vitro, nonclinical, and clinical data indicate dalbavancin to be of benefit for the treatment of serious Gram-positive infections caused by MRSA and CoNS, and all streptococcal and non-VanA enterococcal species, including VanB and VanC phenotypes poorly susceptible or resistant to vancomycin.

Dalbavancin is more active in vitro against staphylococci (including some teicoplanin-resistant strains) than teicoplanin and vancomycin. Dalbavancin has better activity against streptococci, including penicillin-resistant strains, than teicoplanin or vancomycin. Dalbavancin is active in vitro and in vivo against a number of Gram-positive bacteria, including most drug resistant strains.

Dalbavancin is typically administered to an individual as a dalbavancin composition. As used herein, the term “dalbavancin composition” or “dalbavancin formulation” refers to a composition, typically a pharmaceutical composition comprising dalbavancin, as defined above, and one or more other non-dalbavancin components such as, for example, a pharmaceutically acceptable carrier, a stabilizer, a buffers, or other similar components.

As shown in Example 1, dalbavancin is effective at dose intervals of one week. Thus, an advantage of dalbavancin versus other treatment options is the ability to administer this antibiotic on a once-weekly basis, thereby maximizing patient compliance and potentially minimizing the need for or decreasing the length of a hospital stay for parenteral antibiotic administration. Less frequent dosing often permits treatment on an out-patient basis, thus decreasing treatment costs. As further shown in Example 1, a second dose of dalbavancin approximately one week after administration of the first dosage, where the second dose is approximately one-half the first dose, unexpectedly provides significant improvement in the efficacy of treatment.