Combined antibiotic therapy

Abstract

The present invention provides a combination antibiotic therapy for treating A. baumannii infections in a subject. The combination therapy includes rifabutin, and members of the polymyxin class of antibiotics such as, for example, commercially available natural product antibiotics such as polymyxin B and polymyxin E (colistin and its prodrug colistin methanesulfonate (CMS)), and synthetic or semi-synthetic derivatives and analogs such as, for example, SPR206, MRX-8, and QPX9003, and polymyxin-like antibiotics such as, for example, Po17306.

Description

Technical Field

[0001] Field of the Invention The present invention generally relates to rifabutin combination therapy for treating Acinetobacter baumannii infections.

Background Art

[0002] Background The emergence of multi-drug resistant (MDR) or extensively drug resistant (XDR) strains of bacteria over the past few decades has made bacterial infections an increasingly serious public health concern. One bacterial species that poses a major threat to health is Acinetobacter baumannii, which can cause pneumonia, meningitis, and infections of the blood, urinary tract, and skin. Since A. baumannii cells can survive on the surface of artificial objects for long periods, the bacteria are easily transmissible within the hospital environment, and most A. baumannii infections are nosocomial. For example, many soldiers in the Middle East have become infected with A. baumannii while being treated for injuries sustained during combat, and multi-drug resistant strains of this bacterium represent a major complication in the rehabilitation of injured soldiers.

[0003] The treatment of A. baumannii infections is challenging. Through the use of multiple strategies, A. baumannii strains have developed resistance to several different classes of antibiotics, including aminoglycosides, aminocyclitols, tetracyclines, chloramphenicol, and carbapenems. Polymyxins such as colistin generally are used as a last resort due to their serious side effects, but some A. baumannii strains are also resistant to colistin (Zubair et al, 2015, Colistin-resistant Acinetobacter baumannii: beyond carbapenem resistance, Clin Infect Dis. 60(9):1295-303; Trebosc et al, Dissecting Colistin Resistance Mechanisms in Extensively Drug-Resistant Acinetobacter baumannii Clinical Isolates, Therapeutics and Prevention, July / August 2019 Volume 10 Issue 4 e01083-19; the contents of each are incorporated herein by reference). Thus, current tools for treating and preventing diseases caused by this bacterium are inadequate for many patients. Considerable efforts have been made to find solutions for treating these nosocomial pathogens, one of which is combination therapy (Levin et al, 1999; Wood et al, 2003). The combination of two antibiotics has shown different effects on each other, and in many cases, the effects are synergistic or reinforcing, but in some cases, antagonism has been observed (Montero et al, 2004, Tripodi et al, 2007). Unexpected activity of rifabutin, an antibiotic belonging to the rifamycin class, against A. baumannii has recently been reported (US20210077471A1, the content of which is incorporated herein by reference in its entirety).Furthermore, the synergistic effect between rifabutin and polymyxin-class antibiotics has also been recently reported (US20210077472A1, the content of which is hereby incorporated by reference in its entirety). The polymyxin class includes commercially available natural product antibiotics such as polymyxin B and polymyxin E (colistin and its prodrug colistin methanesulfonate (CMS)), SPR206, MRX-8 (Vaara, 2019, Polymyxins and Their Potential Next Generation as Therapeutic Antibiotics, Front. Microbial. 2019;10:1689, the content of which is hereby incorporated by reference in its entirety), and synthetic or semi-synthetic derivatives and analogs currently in clinical development such as QPX9003 (Roberts et al, 2019, the content of which is hereby incorporated by reference in its entirety).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Means for Solving the Problems

[0006] Summary The present invention provides a combination therapy for the treatment of A. baumannii infections, comprising rifabutin and a polymyxin (e.g., colistin, colistin methanesulfonate (CMS), polymyxin B, SPR206, MRX-8, and polymyxin derivatives and analogs such as QPX9003). The present invention is based on the discovery that rifabutin acts synergistically with these antibiotics to inhibit the growth of A. baumannii cells, and that the individual doses of each drug in the combination therapy can be less than the therapeutic doses when given alone. By enabling lower doses of drugs (e.g., polymyxins) that have potential toxicity at their standard therapeutic doses, they can be used more often and at earlier interventions, providing another tool in the fight against A. baumannii infections where drug resistance is a major concern.

[0007] The combination of antibiotics described herein exhibits a synergistic effect against a wide range of A. baumannii strains. This synergistic effect significantly enhances the susceptibility of A. baumannii cells to rifabutin and polymyxin, with the MIC90 of rifabutin (the minimum inhibitory concentration that inhibits the growth of 90% of the strains in the test panel) being as low as 1 / 32 in the presence of sub-inhibitory / sub-therapeutic exposure to the polymyxin antibiotic. Unexpectedly, the presence of sub-inhibitory / sub-therapeutic exposure to the polymyxin antibiotic results in earlier bactericidal activity by rifabutin and prevents regrowth in time-kill experiments (preventing the selection of resistant colonies).

[0008] Aspects of the invention may include a method for treating A. baumannii infections in a subject, the method comprising providing to a subject infected with A. baumannii a therapeutic or sub-therapeutic dose of rifabutin and a sub-therapeutic dose of polymyxin. The therapeutic dose of rifabutin has been described as a dose capable of achieving a Cmax of about 2 mg / L and a 24-hour exposure amount (AUC) greater than 10 mg * h / L. The sub-therapeutic dose of rifabutin can be defined as any dose that results in a C 最大 less than 2 mg / L and a 24-hour AUC of 10 mg * h / L or less. The sub-therapeutic dose of rifabutin administered intravenously may be about two-thirds or less of the standard therapeutic dose.

[0009] In certain embodiments, the sub-therapeutic dose of the polymyxin antibiotic is defined as a dose that, when administered alone, does not achieve the average fC 最大 , fAUC, and fC トラフ required for clinical efficacy, and the fC トラフ of the polymyxin is between its MIC 5 and its MIC 50 (i.e., the concentration at which the growth of 5 - 50% of the strains in the test panel is inhibited). In certain embodiments, the sub-therapeutic dose of the polymyxin is an fC トラフ that is one-half or less of the therapeutic dose or less fCトラフ is the dosage required to achieve. In certain embodiments, a dosage less than the therapeutic amount of polymyxin is fC that is one-fourth of the therapeutic dosage トラフ or less fC トラフ is the dosage required to achieve. In some embodiments, the therapeutic dosage of intravenous rifabutin can be about 600 mg / day. In some embodiments, a dosage less than the therapeutic amount of intravenous rifabutin can be about 550 mg / day or less. A dosage less than the therapeutic amount of intravenous rifabutin may be about 400 mg / day or less. In various embodiments, a dosage less than the therapeutic amount of intravenous rifabutin can be between about 250 mg / day and about 400 mg / day.

[0010] Rifabutin and polymyxin can be provided in a single formulation suitable for intravenous administration. The polymyxin can be polymyxin B, and a dosage less than the therapeutic amount of polymyxin can be about 60 mg / day or less, or the polymyxin can be colistin methanesulfonate (CMS), and a dosage less than the therapeutic amount of polymyxin can be about 90 mg / day or less.

[0011] In certain embodiments, rifabutin and polymyxin can be provided separately. The polymyxin can be polymyxin B, and a dosage less than the therapeutic amount of polymyxin can be between about 0.5 mg / kg / day and about 0.8 mg / kg / day, or the polymyxin can be colistin methanesulfonate (CMS), and a dosage less than the therapeutic amount of polymyxin can be between about 0.8 mg / kg / day and about 1.6 mg / kg / day.

[0012] In various embodiments, rifabutin can be administered intravenously, or orally, or by inhalation. A. baumannii can include carbapenem-resistant A. baumannii (CRAB). The polymyxin can be SPR206, or QPX9003, or MRX-8, or any other synthetic or semi-synthetic polymyxin, or a polymyxin-like antibiotic (e.g., Pol7306), and a dose less than the therapeutic amount of the polymyxin is about one-third of the standard therapeutic dose.

[0013] Aspects of the invention can include a combination therapy comprising rifabutin and polymyxin in a therapeutically effective amount for treating A. baumannii infections in a subject, where rifabutin and polymyxin are present in amounts that would be considered less than the therapeutic amount if provided alone.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0015] Detailed Description The present invention provides a combination therapy for treating A. baumannii infections in a subject. The combination therapy is based on the discovery that rifabutin acts synergistically with polymyxin B and polymyxin E (colistin), as well as polymyxin antibiotics such as synthetic or semi-synthetic derivatives and analogs currently in clinical development, such as SPR206, MRX-8, and QPX9003, to inhibit the growth of A. baumannii cells even when the individual antibiotics are administered at sub-therapeutic doses when given alone. Thus, while polymyxins such as colistin are last resort antibiotics due to potential toxicity and adverse events, their ability to reduce their dosage when used in combination with rifabutin opens up new uses and can provide another tool in the fight against increasingly drug-resistant infections.

[0016] The activity of rifabutin against A. baumannii, including multi-drug resistant (MDR) and carbapenem-resistant A. baumannii (CRAB), has recently been reported in US20210077471A1, along with the intravenous dosage form of rifabutin in US20210077470A1, the entire contents of each of which are incorporated herein by reference in their entirety. Further, the synergistic effect between rifabutin and the polymyxin class of antibiotics has been reported in US20210077472A1, the entire contents of which are incorporated herein by reference.

[0017] The surprising benefit of this synergistic effect is that patients afflicted with A. baumannii infections such as CRAB can be administered a low dose (about one-quarter of the normal prescription dose) of a member of the polymyxin class of antibiotics, together with a low dose of rifabutin (about one-quarter of the effective dose) required to achieve a Cmax of about 2 mg / L and / or an AUC greater than 10 mg * h / L and less than 300 mg * h / L.

[0018] Accordingly, the methods and formulations of the present invention include combination therapies of rifabutin at therapeutic or sub-therapeutic doses and polymyxin at sub-therapeutic doses. In various embodiments, rifabutin can be administered together with a member of the polymyxin class of antibiotics in a single vial (co-formulation) for reconstitution and dilution with a diluent appropriate for injection into humans. Alternatively, rifabutin and a member of the polymyxin class of antibiotics can be contained in separate vials, reconstituted independently with an appropriate diluent just prior to injection into humans, and combined. In still other embodiments, rifabutin and a member of the polymyxin class of antibiotics can be administered either separately to a patient, consecutively at the same injection site, or in parallel at two different injection sites. Also, rifabutin can be administered orally, and a member of the polymyxin class of antibiotics can be administered by injection or any other appropriate route of administration (e.g., inhalation). Indeed, rifabutin and a member of the polymyxin class of antibiotics can be administered together or separately by inhalation.

[0019] The therapeutic dose of intravenous rifabutin is about 300 mg BID (i.e., 600 mg / day). When used in combination with polymyxin according to the methods of the present invention, the amount of rifabutin administered intravenously (IV) in the combination therapy can be less than about 600 mg / day (e.g., sub-therapeutic if given alone). In some embodiments, the IV "sub-therapeutic" rifabutin dose can be more than about 150 mg / day, and in preferred embodiments, can be about 250 to about 500 mg / day (125 - 250 mg BID).

[0020] The standard treatment polymyxin dosing is discussed in Tsuji BT, Pogue JM, Zavascki AP, et al. International Consensus Guidelines for the Optimal Use of the Polymyxins: Endorsed by the America College of Clinical Pharmacology (ACCP), European Society of Clinical Microbiology and Infectious Diseases (ESCMID), Infectious Diseases Society of America (IDSA), International Society for Anti-infective Pharmacology (ISAP), Society of Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP). Pharmacotherapy 2019;39(1):10-39, the entire text of which is incorporated herein by reference.

[0021] The standard treatment dose of polymyxin B can be about 1.5 to about 2.5 mg / kg / day. When administered separately from rifabutin, polymyxin B can be dosed in mg / kg units and can be about 0.5 to about 0.8 mg / kg / day. When co-formulated with rifabutin, polymyxin B can be provided at a fixed dose, for example, about 60 mg / day (30 mg BID).

[0022] The standard treatment dose of CMS can be about 2.5 to about 5.0 mg / kg / day. When administered separately from rifabutin, CMS can be dosed in mg / kg units and can be about 0.8 to about 1.6 mg / kg / day. When co-formulated with rifabutin, CMS can be provided at a fixed dose, for example, about 90 mg / day (45 mg BID).

[0023] Generally, doses below the therapeutic dose of polymyxin antibiotics are considered doses at which the mean fC 最大 , fAUC and fC トラフ are not achieved, and / or the fC トラフ of polymyxin is between its MIC5 and its MIC50 (i.e., the concentration at which growth of 5 - 50% of the strains is inhibited in a test panel of recent A. baumannii clinical isolates with more than 100). fC 最大 should be understood to be the pharmacokinetically maximum free drug concentration achieved by the drug at the dose administered at steady state. fC トラフ should be understood to be the pharmacokinetically minimum free drug concentration achieved by the drug between doses at steady state at the dose administered. fAUC should be understood to be the pharmacokinetic free drug area under the curve (i.e., generally the total exposure within 24 hours) achieved by the drug at the dose administered at steady state.

[0024] Combination therapy The combination therapy of the present invention comprises two antibiotics that act synergistically to inhibit the growth of A. baumannii cells. The synergistic effect between an antibiotic such as rifabutin and polymyxin B or colistin, or a synthetic or semi-synthetic derivative or analog, or a polymyxin-like antibiotic in clinical development such as SPR206, MRX-8, QPX9003 or Pol7306 can be determined by any suitable method.

[0025] In the combination therapy of the present invention, one of the antibiotics is rifabutin. As the combination therapy, polymyxin B or colistin, or a synthetic or semi-synthetic derivative or analog, or a polymyxin such as SPR206, MRX-8, QPX9003 or Pol7306 that acts synergistically with rifabutin, such as a polymyxin-like antibiotic in clinical development, can be mentioned. Clinically, colistin can be provided as colistin methanesulfonate or colistin sulfate. In the case of polymicrobial infections, the inclusion of any additional antibiotics in the combination therapy is contemplated herein and will be apparent to those skilled in the art and may include 3, 4, 5, or more different antibiotics. Exemplary additional antibiotics can include aminocyclitol, aminoglycoside, β-lactam, β-lactamase inhibitor, carbapenem, cephalosporin, quinolone, rifamycin, sulfonamide, minocycline, eravacycline, sulbactam, or tetracycline. Each antibiotic can independently be amikacin, trimethoprim-sulfamethoxazole, cefepime, cefiderocol, ceftazidime, chloramphenicol, ciprofloxacin, colistin, doripenem, gentamicin, imipenem, levofloxacin, meropenem, penicillin, piperacillin, polymyxin B, rifampicin, tazobactam, or tigecycline.

[0026] Any additional antibiotics can be administered by any suitable route of administration. For example, but not limited to, each antibiotic can independently be administered intravenously, orally, parenterally, subcutaneously, by inhalation, by injection, and / or by infusion.

[0027] Additional antibiotics can be administered according to the same dosing regimen. One or more antibiotics can be administered according to different dosing regimens. A dosing regimen can include dosing, schedule or administration, or both. Dosing can be described by the absolute amount of the drug (e.g., mg) or by the relative amount of the drug to the subject (e.g., mg / kg). The schedule of administration can be described by the interval between doses. For example, the interval between doses can be about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 6 hours, about 8 hours, about 12 hours, about 24 hours, about 36 hours, about 48 hours, about 3 days, about 4 days, about 5 days, about 6 days, about 7 days, or more, but is not limited thereto.

[0028] Formulation One or more antibiotics can be provided in a single formulation. One or more antibiotics can be provided in separate formulations. Each formulation can be prepared for delivery by a specific route of administration such as intravenously, orally, parenterally, subcutaneously, by inhalation, by injection, and / or by infusion, etc.

[0029] The antibiotic can be provided as a pharmaceutically acceptable salt such as a non-toxic acid addition salt, which is a salt of an amino group formed with an inorganic acid such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid and perchloric acid, but is not limited thereto, or a salt of an amino group formed with an organic acid such as acetic acid, maleic acid, tartaric acid, citric acid, succinic acid, methanesulfonic acid, glucuronic acid, malic acid, gluconic acid, lactic acid, aspartic acid or malonic acid, but is not limited thereto.

[0030] The formulation can be administered by injection, infusion, implant (intravenous, intramuscular, subcutaneous or the like) or dosage form, by inhalation in the formulation, or via a suitable delivery device or implant containing a conventional non-toxic pharmaceutically acceptable carrier, solvent, diluent, and adjuvant. The formulation and preparation of such compositions are well known to those skilled in the art of pharmaceutical formulations.

[0031] Formulations for parenteral use may be provided in unit dosage forms (e.g., in single-dose ampoules and vials), in vials containing multiple doses, and in vials to which suitable preservatives may be added (see below), in pre-filled syringes, or in pre-filled IV bags. The pharmaceutical compositions described herein may be in a form suitable for sterile injection.

[0032] The formulation may comprise a solution containing rifabutin. The rifabutin solution and the method of manufacturing the rifabutin solution are described in US20210077470A1, the content of which is hereby incorporated by reference in its entirety.

[0033] Depending on the patient's needs and clinical condition, administration of the composition by IV may be preferred over oral administration. This is because IV administration allows for rapid introduction of the antibiotic into the systemic circulation, provides complete bioavailability, enables better control of the pharmacokinetic parameters driving pharmacological efficacy, and avoids issues of stability and absorption in the gastrointestinal tract.

[0034] Treatment of A. baumannii infections The combination therapy of the present invention is useful for the treatment of A. baumannii infections in a subject. The subject may be a human. The subject may be a pediatric, neonatal, newborn, infant, child, adolescent, preteen, teenager, adult, or elderly. The subject may be in a critical care, intensive care, neonatal intensive care, pediatric intensive care, coronary care, cardiothoracic care, surgical intensive care, medical intensive care, long-term intensive care, operating room, ambulance, field hospital, or out-of-hospital site environment.

[0035] The subject may be infected with A. baumannii infections that are resistant to antibiotics or multiple classes of commercially available antibiotics, such as MDR, XDR, or PDR A. baumannii infections. Importantly, the combination therapy of the present invention is useful for the treatment of infections caused by A. baumannii strains having elevated MICs against rifabutin and / or polymyxin B or colistin, or synthetic or semi-synthetic derivatives or analogs in clinical development, such as SPR206, MRX-8, QPX9003, or Pol7306.

[0036] The antibiotics in the combination therapy of the present invention can be administered simultaneously or sequentially. Sequential or alternating administration can include providing each antibiotic exclusively for a certain period. Sequential administration can include overlapping periods in which both a formulation containing rifabutin and a formulation containing polymyxin are provided to the subject.

Example

[0037] Example 1 The MIC90 (minimum inhibitory concentration that inhibits the growth of 90% of the strains in the test panel) of rifabutin was 2 mg / L or 1 mg / L when tested by RPMI / FCS microdilution or MHA / PIH agar dilution, respectively, against a panel of 293 carbapenem-resistant Acinetobacter baumannii (CRAB) (Trebosc V, et al. 2020. In vitro activity of rifabutin against 293 contemporary carbapenem-resistant Acinetobacter baumannii clinical isolates and characterization of rifabutin mode of action and resistance mechanisms. J Antimicrob Chemother. 75(12):3552-3562, which is incorporated herein by reference).

[0038] In CAMHB / PIH, the fC of various members of the polymyxin class of antibiotics トラフ (free drug concentration in the trough), when tested by microdilution in the presence of approximately one-fourth of the rifabutin MIC, the MIC of rifabutin in the presence of 0.125 mg / L polymyxin B, 0.125 mg / L colistin, and 0.03 mg / L SPR206 90 was significantly reduced to 0.06 - 0.25 mg / L. At each of these polymyxin concentrations, 0%, 3%, and < 5% of the strains could be sensitive to each polymyxin. Figure 1 shows the cumulative index as well as the MIC 50 and MIC 90 of rifabutin in the presence of members of the polymyxin family of antibiotics at sub-MIC (sub-trough concentration), demonstrating the synergistic effect discussed above.

[0039] In addition, when tested in MHA / PIH, the MIC distribution of rifabutin showed three distinct subpopulations. Population 1 (MIC < 0.125 mg / L) represented 72% of the strains, population 2 (MIC ≥ 0.125 to < 16 mg / L) represented 27% of the strains, and population 3 (MIC ≥ 16 mg / L) represented 1% of the strains (Trebosc V, et al. 2020. In vitro activity of rifabutin against 293 contemporary carbapenem-resistant Acinetobacter baumannii clinical isolates and characterization of rifabutin mode of action and resistance mechanisms. J Antimicrob Chemother. 75(12):3552 - 3562, which is hereby incorporated by reference in its entirety). In CAMHB / PIH, when tested by microbroth dilution in the presence of approximately one-fourth of the fC trough (free drug concentration at the trough) of various members of the polymyxin class of antibiotics, the MIC distribution of rifabutin showed only one major strain population with 99% of the strains having an MIC of 1 mg / L or less. This indicates that this combination is active against strains with elevated rifabutin MIC. Importantly, 45, 40, and 18 strains had an MIC higher than 2 mg / L against colistin, polymyxin B, and SPR206, respectively, indicating that this combination is active against polymyxin-resistant strains. Collectively, these results suggest that this combination is active against strains with elevated rifabutin MIC, polymyxin-resistant strains, or both. Figure 2 illustrates the MIC distribution of rifabutin in the presence of members of the polymyxin family of antibiotics at sub-MIC (subtrough concentration) and shows the synergistic effect discussed above.

[0040] Example 2 Based on the data of Example 1, the bactericidal activity and resistance expression of rifabutin and fixed rifabutin / polymyxin concentrations were evaluated in time-kill curve experiments. The concentrations were fixed at 0.25 mg / L for rifabutin (1 / 8 of the average rifabutin MIC 90 ), 0.125 mg / L and 0.03 mg / L for colistin and polymyxin B, respectively (1 / 4 or lower of the fC トラフ of these polymyxins), and 0.03 mg / L for SPR206 (the concentration that inhibits the growth of less than 5% of the strain when given alone). The low-concentration rifabutin + low-concentration members of the polymyxin class of antibiotics were as bactericidal as at least the full dose of rifabutin or the full dose of polymyxin antibiotics and completely prevented resistance expression as shown in Figures 3 and 4. Figures 3 and 4 show time-kill curve experiments for two different A. baumannii strains (Popl and Pop2) with widely different rifabutin MICs. As shown, 0.25 mg / L of rifabutin, and 0.125 or 0.03 mg / L of colistin or polymyxin B, or 0.03 mg / L of SPR206 are either poorly bactericidal or allow regrowth in either population. However, the combination of one of the polymyxins and rifabutin provided together at low dosages has high and rapid bactericidal activity, shows a synergistic effect in this combination, and prevents resistance expression (bacterial regrowth).

[0041] Figure 3 shows the time-kill curve of rifabutin against the A. baumannii Pop1 strain (rifabutin MIC = 0.016 mg / L) in the presence of members of the polymyxin family of antibiotics at sub-MIC (subtrough concentration).

[0042] Figure 4 shows the time-kill curve of rifabutin against the A. baumannii Pop2 strain (rifabutin MIC = 1 mg / L) in the presence of members of the polymyxin family of antibiotics at sub-MIC (subtrough concentration).

[0043] Method Antibacterial agent Rifabutin (batch number BV-015-3219-001-03) was manufactured by Olon S.p.A. and a stock solution of 10 g / L was prepared in DMSO. The stock solution of rifampicin (Sigma R3501) was prepared at 10 mg / mL in DMSO. The stock solutions of colistin sulfate (Sigma C4461), polymyxin B sulfate (Sigma P4932), and SPR206 acetate (MedChemExpress, HY-128780B) were prepared at 10 mg / mL in water. The stock solutions were stored at -20 °C until use.

[0044] Bacterial strain The A. baumannii clinical isolates used in this study were from the strain collection of BioVersys. The strains were stored at -80 °C as 20% (v / v) glycerol stock cultures.

[0045] Antibacterial susceptibility and synergy testing The MIC of rifabutin in combination at a fixed concentration of a specific polymyxin was determined by the microbroth dilution method according to the CLSI guidelines. The medium used for the determination of MIC was cation-adjusted Mueller-Hinton broth (CAMHB) supplemented with 0.1 mM pyridoxal isonicotinoyl hydrazone (PIH). As previously described by Trebosc et al. 2020, the MIC of rifabutin in this medium can be affected by the skip-well phenomenon, and wells that grow at concentrations above the concentration of the first inhibitory well do not reflect the appropriate MIC of this strain. Therefore, the MIC value was evaluated by visual inspection of the test plate and set as the first minimum rifabutin concentration that prevented growth.

[0046] Time-kill curve The time-kill rate theory was carried out with CAMHB added to 0.1 mM PIH medium. Rifabutin was tested at 0.25 mg / L regardless of the presence or absence of a specific concentration of polymyxin agent. Samples were taken at 0, 2, 4, 8, and 24 hours to determine colony-forming units (cfu). Bactericidal activity was defined as a decrease in cfu of 3 logs or more compared to the cfu present in the inoculum (0 hours). The synergistic effect of the combinations tested was defined as a decrease in cfu of 2 logs or more compared to the cfu of the most active agent in the combination.

[0047] Incorporation by reference References and citations to other documents such as patents, patent applications, patent gazettes, journals, books, papers, web content, etc. are made throughout this disclosure. All such documents are hereby incorporated by reference in their entirety for all purposes.

[0048] Equivalents In addition to what is shown and described herein, various modifications and many further embodiments of the present invention will become apparent to those skilled in the art from the entire contents of this document, including references to scientific and patent literature cited herein. The subject matter of this specification includes important information, exemplification, and guidance applicable to practice in various embodiments and equivalents of the present invention.

Claims

1. A combination for use in a method for treating A. baumannii infection in a subject, wherein the combination comprises rifabutin and polymyxin, wherein the polymyxin is present in a dose less than the therapeutic dose and the rifabutin is present in a therapeutic dose or less than the therapeutic dose.

2. A dose of polymyxin less than the therapeutic dose is required for the average fC necessary for clinical efficacy. 最大 , fAUC and fc トラフ The combination according to claim 1, wherein the dose is one that is not achieved when administered alone; and / or a dose of the polymyxin less than the therapeutic dose results in an fC trough that inhibits growth in about 5% to about 50% of the strains in a test panel of 100 or more recent A. baumannii clinical isolates; and / or the dose of the polymyxin less than the therapeutic dose is less than about half of the standard therapeutic dose.

3. The combination according to claim 1, wherein the standard therapeutic dose of rifabutin is approximately 600 mg / day.

4. The combination according to claim 1, wherein the dose of rifabutin less than the therapeutic dose is about two-thirds or less than the standard therapeutic dose.

5. The combination according to claim 1, wherein the dose of rifabutin less than the therapeutic dose is about 550 mg / day or less.

6. The combination according to claim 5, wherein the dose of rifabutin less than the aforementioned therapeutic dose is approximately 250 mg / day to approximately 400 mg / day.

7. The combination according to claim 1, wherein the rifabutin and the polymyxin are provided in a single formulation.

8. The combination according to claim 7, wherein the polymyxin is polymyxin B, and the dose of the polymyxin less than the therapeutic dose is about 60 mg / day or less.

9. The combination according to claim 7, wherein the polymyxin is colistin methanesulfonic acid (CMS), and the dose of the polymyxin less than the therapeutic dose is about 90 mg / day or less.

10. The combination according to claim 1, wherein the rifabutin and the polymyxin are provided separately.

11. The combination according to claim 10, wherein the polymyxin is polymyxin B, and the dose of the polymyxin less than the therapeutic dose is about 0.5 mg / kg / day to about 0.8 mg / kg / day.

12. The combination according to claim 10, wherein the polymyxin is colistin methanesulfonic acid (CMS), and the dose of the polymyxin below the therapeutic dose is about 0.8 mg / kg / day to about 1.6 mg / kg / day.

13. The polymyxin is SPR206, QPX9003, MRX-8, or Pol7306, and doses of the polymyxin less than the therapeutic dose inhibit the growth of approximately 5% to 50% of the strains in a test panel of 100 or more recent A. baumannii clinical isolates. トラフ The combination according to claim 1, which brings about the following.

14. A composition for use in a method for treating A. baumannii infection in a subject, characterized in that the composition comprises a therapeutic dose or a dose less than the therapeutic dose of rifabutin and is administered in combination with a dose less than the therapeutic dose of polymyxin.

15. A composition for use in a method for treating A. baumannii infection in a subject, characterized in that the composition comprises a dose less than a therapeutic dose of polymyxin and is administered in combination with a therapeutic dose or less than a therapeutic dose of rifabutin.

16. A combination comprising a therapeutically effective dose of rifabutin and polymyxin for treating A. baumannii infection in a subject, wherein the polymyxin is present in an amount that may be less than a therapeutic dose when provided alone.

17. The combination according to claim 16, wherein the rifabutin is present in a standard therapeutic dose of about 600 mg / day.

18. The combination according to claim 16, wherein the rifabutin, when provided alone, is present in an amount of about two-thirds or less of a standard therapeutic dose or less.

19. The average fC required for clinical efficacy when the polymyxin is administered alone 最大 , fAUC, and fc トラフ The combination according to claim 16, which exists in an amount that does not achieve the desired result.

20. A dose of polymyxin less than the therapeutic dose inhibits the growth of approximately 5% to 50% of the strains in a test panel of 100 or more recent A. baumannii clinical isolates. トラフ The combination according to claim 16, which brings about the following.

21. The combination according to claim 16, wherein the polymyxin, when provided alone, is present in about half or less of a standard therapeutic dose or a lower dose.

22. The combination according to claim 16, comprising approximately 550 mg / day or less of rifabutin.

23. The combination according to claim 16, comprising approximately 250 mg / day to approximately 400 mg / day of rifabutin.

24. The combination according to claim 16, wherein the rifabutin and the polymyxin are provided in a single formulation.

25. The combination according to claim 24, wherein the polymyxin is polymyxin B and is present in an amount of about 60 mg / day or less.

26. The combination according to claim 24, wherein the polymyxin is colistin methanesulfonic acid (CMS) and is present in an amount of about 90 mg / day or less.

27. The combination according to claim 16, wherein the rifabutin and the polymyxin are provided separately.

28. The combination according to claim 27, wherein the polymyxin is polymyxin B and is present in an amount of about 0.5 mg / kg / day to about 0.8 mg / kg / day.

29. The combination according to claim 27, wherein the polymyxin is colistin methanesulfonic acid (CMS) and is present in an amount of about 0.8 mg / kg / day to about 1.6 mg / kg / day.

30. The combination according to claim 16, wherein the polymyxin is SPR206, QPX9003, MRX-8, or Pol7306, and doses of the polymyxin less than the therapeutic dose result in an fC trough that inhibits growth in about 5% to about 50% of the strains in a test panel of 100 or more recent A. baumannii clinical isolates.

31. A composition for treating A. baumannii infection in a subject, characterized in that the composition comprises rifabutin and is administered in combination with polymyxin, wherein the polymyxin is present in an amount that may be less than a therapeutic dose when provided alone.

32. A composition for treating A. baumannii infection in a subject, characterized in that the composition comprises polymyxin and is administered in combination with rifabutin, wherein the polymyxin is present in an amount that may be less than a therapeutic dose when provided alone.

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