Zidovudine and tetracycline antibiotic combination

Abstract

The present invention relates to a combination comprising zidovudine or a pharmaceutically acceptable derivative thereof and a tetracycline antibiotic or a pharmaceutically acceptable derivative or prodrug thereof for use in the treatment of microbial infections, particularly bacterial infections such as urinary tract infections.

Description

[Technical field]

[0001] The present invention relates to a combination of zidovudine or a pharma- ceutically acceptable derivative thereof and a tetracycline antibiotic or a pharma- ceutically acceptable derivative or prodrug thereof selected from the group defined herein for use in the treatment of microbial infections. In particular, the present invention relates to the use of such a combination for killing vegetative (i.e. logarithmic phase) microorganisms associated with microbial infections, such as gram-negative infections, such as urinary tract infections. [Background technology]

[0002] Before the introduction of antibiotics, patients suffering from acute microbial infections (e.g. tuberculosis or pneumonia) had a poor chance of survival. For example, the mortality rate from tuberculosis was approximately 50%. This situation changed rapidly with the introduction of antimicrobial drugs in the 1940s and 1950s, but bacteria responded by gradually developing resistance to commonly used antibiotics. There are now antibiotic-resistant bacteria in every country in the world.

[0003] In fact, over 70% of bacteria causing hospital-acquired infections in the United States are resistant to at least one of the major antimicrobial agents typically used to fight infections (Nature Reviews, Drug Discovery, 1, 895-910(2002)). Thus, the World Health Organization classifies antimicrobial resistance as "a serious threat that is no longer a future prediction but is occurring now in every region of the world, potentially affecting people of all ages, in every country" ("Antimicrobial resistance: global report on surveillance", The World Health Organization, April 2014).

[0004] One group of antibiotics facing significant resistance problems are compounds used to treat urinary tract infections (UTIs), specifically urogenital infections. A recent report from Public Health England noted that antimicrobial resistance was common in over one million urinary tract infections caused by bacteria identified by NHS laboratories in 2016 (<English Surveillance Programme for Antimicrobial Utilisation and Resistance (ESPAUR)> >(2017)).

[0005] Thus, there is a desperate need for solutions to the growing problem of resistant bacteria causing urinary tract infections.

[0006] WO2014 / 147405 describes the use of zidovudine in combination with a polymyxin selected from colistin and polymyxin B to treat microbial infections. WO2015 / 114340 describes the use of zidovudine in combination with a polymyxin selected from colistin or polymyxin B; an antituberculous antibiotic selected from rifampicin, rifapentine or rifabutin; and optionally piperine to treat microbial infections. WO2018 / 011562 describes combinations comprising zidovudine and a carbapenem, optionally comprising a polymyxin selected from polymyxin B and polymyxin E. Summary of the Invention

[0007] Surprisingly, and of great importance to the fight against antimicrobial resistance in the treatment of urinary tract infections, applicants have discovered that the antiretroviral drug zidovudine has a synergistic effect with tetracycline antibiotics - in other words, the combination has a biological activity that is greater than the predicted additive effect of each drug at the dosage levels described.

[0008] Zidovudine (AZT) is a nucleoside-related reverse transcriptase inhibitor and a type of antiretroviral drug used to treat HIV / AIDS infection. In addition to its antiretroviral activity, the antibacterial effect of AZT has been demonstrated both in vitro and in vivo using experimental models of Gram-negative infection (Hermann et al., Antimicrob Agents Chemther. 1992 May; 36(5): 1081-1085). It has also been reported that zidovudine is active as an antimicrobial agent when combined with the antibiotic gentamicin (Doleans-Jordheim A. et al., Eur J Clin Microbiol Infect Dis. 2011 Oct;30(10):1249-56).

[0009] When two active agents are used in combination, a synergistic effect cannot be predicted or expected. Thus, the present invention is based on the unexpected finding that zidovudine or a pharma- ceutically acceptable derivative thereof, when used in combination with a tetracycline antibiotic or a pharma- ceutically acceptable derivative or prodrug thereof, exhibits synergistic antimicrobial activity against log-phase (i.e., vegetative) microorganisms. In particular, synergistic effects are seen when the combination is used against gram-negative bacteria.

[0010] The surprising bioactivity of the combination of the present invention provides an opportunity to regenerate the activity of certain urinary tract antibiotics to which bacterial resistance has developed.

[0011] Synergy in the context of antimicrobial agents is measured in a number of ways, with the commonly accepted view being that "synergy is an effect greater than additive." One way to assess whether synergy is observed is to use the "checkerboard" technique, which is an accepted method that generates a value called the fractional inhibitory concentration index (FICI). Orhan et al J. Clin. Microbiol. 2005, 43(1):140, describes the checkerboard method and analysis in paragraphs 140-141, explaining that the FICI value is the ratio of the sum of the MIC (minimum inhibitory concentration) levels of each individual component alone and in the mixture. The combination is considered synergistic if the ΣFIC is ≦0.5, indifferent if the ΣFIC is >0.5 but <4.0, and antagonistic if the ΣFIC is >4.0.

[0012] Another accepted test to determine the presence or absence of synergy is to use the time-kill method, in which the dynamic effect of drug combinations is compared to each drug alone when evaluating the effect on logarithmic or stationary growth of bacteria over time. Again, possible outcomes are in terms of synergy, additive effects, or antagonism.

[0013] In one aspect, the invention provides a combination of zidovudine, or a pharma- ceutically acceptable derivative thereof, and a tetracycline antibiotic, or a pharma- ceutically acceptable derivative or prodrug thereof, for use in the treatment of a microbial infection.

[0014] In another aspect, the invention provides the use of zidovudine, or a pharma- ceutically acceptable derivative thereof, in combination with a tetracycline antibiotic, or a pharma- ceutically acceptable derivative or prodrug thereof, in the manufacture of a medicament for treating a microbial infection.

[0015] In another aspect, the invention provides the use of a tetracycline antibiotic, or a pharma- ceutically acceptable derivative or prodrug thereof, in combination with zidovudine, or a pharma- ceutically acceptable derivative or prodrug thereof, in the manufacture of a medicament for treating a microbial infection.

[0016] In a further aspect, the present invention provides a method for treating a microbial infection comprising administering zidovudine, or a pharma- ceutically acceptable derivative thereof, in combination with a tetracycline antibiotic, or a pharma- ceutically acceptable derivative or prodrug thereof, to a mammal, such as a human.

[0017] In each of the above aspects, the tetracycline antibiotic may be selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, lymecycline, meclocycline, methacycline, minocycline, rolitetracycline, doxycycline, tigecycline, eravacycline, sarecycline, omadacycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a preferred embodiment of each of the above aspects, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, meclocycline, methacycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a more preferred embodiment, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a further preferred embodiment, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a most preferred embodiment, the tetracycline antibiotic is doxycycline or a pharmaceutically acceptable derivative or prodrug thereof.

[0018] There is also provided a pharmaceutical composition comprising a combination of zidovudine or a pharma- ceutically acceptable derivative thereof and a tetracycline antibiotic or a pharma- ceutically acceptable derivative or prodrug thereof, and a pharma- ceutically acceptable adjuvant, diluent or carrier, for use in the treatment of a microbial infection, preferably wherein the microbial infection is a bacterial infection, such as a Gram-negative infection, wherein the tetracycline antibiotic may be defined as above.

[0019] In a further aspect, the invention relates to a product comprising zidovudine or a pharma- ceutically acceptable derivative thereof and a tetracycline antibiotic or a pharma- ceutically acceptable derivative or prodrug thereof as a combination drug for simultaneous, separate or sequential use in killing vegetative microorganisms associated with a microbial infection, preferably for killing vegetative bacteria associated with a bacterial infection, such as a Gram-negative infection. The tetracycline antibiotic may be as defined in the other aspects of the invention above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] As used herein, the terms "combination of" and "in combination with" are intended to encompass separate, sequential, and simultaneous administration of agents. Unless otherwise specified, the terms are also intended to exclude additional active agents, e.g., "a combination of zidovudine and doxycycline" means that zidovudine and doxycycline are administered separately, sequentially, or simultaneously, but no other active agent is administered.

[0021] When the agents are administered sequentially, either the zidovudine or the tetracycline antibiotic can be administered first. When administered simultaneously, the agents can be administered in the same or different pharmaceutical compositions. Adjunctive therapy, i.e., one agent is used as a primary treatment and the other agent is used to support the primary treatment, is also an embodiment of the present invention.

[0022] The combination of the present invention can be used to treat microbial infection.In particular, it can be used to kill proliferative and / or clinically latent microorganisms associated with microbial infection, preferably proliferative microorganisms associated with microbial infection, such as proliferative bacteria associated with gram-negative infection.Therefore, when referring to the treatment of microbial infection in this specification, it includes killing proliferative and / or clinically latent microorganisms associated with such infection.

[0023] As used herein, "kill" refers to loss of viability as assessed by lack of metabolic activity.

[0024] As used herein, a "clinically latent microorganism" refers to a microorganism that is metabolically active but has a growth rate below a threshold for infectious disease manifestation, which refers to a growth rate threshold below which there are no symptoms of infectious disease in the host.

[0025] The metabolic activity of clinically latent microorganisms can be measured by several methods known to those skilled in the art, for example by measuring the mRNA level in the microorganism or by measuring the uridine incorporation rate of the microorganism. In this respect, clinically latent microorganisms exhibit a lower, but still significant, metabolic activity in comparison to microorganisms under logarithmic growth conditions (in vitro or in vivo). (I) mRNA levels (e.g., 0.0001 to 50%, e.g., 1 to 30%, 5 to 25%, or 10 to 20% of the level of mRNA); and / or (II) Uridine (e.g. [ 3 H]uridine) incorporation levels (e.g., [ 3 0.0005 to 50%, e.g., 1 to 40%, 15 to 35%, or 20 to 30%, of the level of [H]uridine incorporation) has.

[0026] A clinically latent microorganism typically has a number of distinguishing characteristics. For example, it may be viable but non-culturable; that is, the microorganism is not normally detectable by standard culture techniques, but is detectable and quantifiable by techniques such as broth dilution counting, microscopy, or molecular techniques such as polymerase chain reaction. Additionally, a clinically latent microorganism is phenotypically resistant and thus susceptible (in log phase) to the bacteriostatic effects of conventional antimicrobial agents (i.e., microorganisms for which the minimum inhibitory concentration (MIC) of a conventional antimicrobial agent remains substantially unchanged), but has a greatly reduced susceptibility to drug-induced killing (e.g., microorganisms for which the ratio of minimum bactericidal concentration (e.g., minimum bactericidal concentration, MBC) to MIC is 10 or greater for any given conventional antimicrobial agent).

[0027] As used herein, the term "microbial" refers to fungi and bacteria. References herein to "microbial," "antimicrobial," or "antimicrobially" are to be construed accordingly. For example, the term "microbial" refers to "fungal" or "bacterial," and "microbial infection" refers to a fungal infection or a bacterial infection.

[0028] In various embodiments of the invention, one or more of the above combinations are used to treat bacterial infections, and in particular, the combinations can be used to kill vegetative and / or clinically latent microorganisms associated with bacterial infections, preferably vegetative bacteria associated with bacterial infections. As used herein, the term "bacteria" (and derivatives thereof, such as "microbial infection") includes, but is not limited to, reference to the following classifications and specific types of organisms (or infections by organisms):

[0029] Gram-positive cocci, such as Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophyticus, Staphylococcus auricularis, Staphylococcus capitis capitis, Staphylococcus c. ureolyticus, Staphylococcus caprae, Staphylococcus cohnii cohnii, Staphylococcus c. urealyticus, Staphylococcus aequorum, equorum, Staphylococcus gallinarum, Staphylococcus haemolyticus, Staphylococcus hominis hominis, Staphylococcus hominis novobiosepticius, Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus lugdunensis, Staphylococcus pasteuri, Staphylococcus saccharolyticus, Staphylococcus schleiferi schleiferi schleiferi schleiferi, Staphylococcus schleiferi coagulans, Staphylococcus sciuri, Staphylococcus simulans, Staphylococcus warneri and Staphylococcus xylosus.xylosus), Streptococci (e.g., β-hemolytic pyogenes streptococci (Streptococcus agalactiae, Streptococcus canis, Streptococcus dysgalactiae dysgalactiae, Streptococcus dysgalactiae equisimilis, Streptococcus equi equi, Streptococcus equi zooepidemicus, Streptococcus iniae, Streptococcus porcinus, and Streptococcus pyogenes). pyogenes), microaerophilic pyogenous streptococci (Streptococcus "milleri" e.g., Streptococcus anginosus, Streptococcus constellatus constellatus, Streptococcus constellatus pharyngidis and Streptococcus intermedius), "mitis" (α-haemolytic Streptococcus "viridans" e.g., Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus cristatus, etc.). cristatus, Streptococcus gordonii and Streptococcus parasanguinis), "salivarius" (non-hemolytic, e.g., Streptococcus salivarius and Streptococcus vesicularis).vestibularis) and oral streptococci of the group "mutans" (tooth surface streptococci, e.g. Streptococcus criceti, Streptococcus mutans, Streptococcus ratti and Streptococcus sobrinus), Streptococcus acidominimus, Streptococcus bovis, Streptococcus faecalis, Streptococcus equinus, Streptococcus pneumoniae and Streptococcus suis. suis) or streptococci otherwise classified as group A, B, C, D, E, G, L, P, U or V streptococci); Gram-negative cocci, such as Neisseria gonorrhoeae, Neisseria meningitidis, Neisseria cinerea, Neisseria elongata, Neisseria flavescens, Neisseria lactamica, Neisseria mucosa, Neisseria sicca, Neisseria subflava and Neisseria weaveri; Bacillaceae, such as Bacillus anthracis, Bacillus subtilis, Bacillus thuringiensis, Bacillus thuringiensis, Bacillus stearothermophilus and Bacillus cereus; Enterobacteriaceae, e.g., Escherichia coli, Enterobacter spp. (e.g., Enterobacter aerogenes, Enterobacter agglomerans and Enterobacter cloacae), Citrobacter spp. (e.g., Citrobacter freundii and Citrobacter divernis), Hafnia spp. (e.g., Hafnia alvei), Erwinia spp. (e.g., Erwinia persicinus), Morganella morganii, morganii), Salmonella (Salmonella enterica and Salmonella typhi), Shigella (e.g., Shigella dysenteriae),dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei), Klebsiella species (e.g. Klebs. pneumoniae, Klebs. oxytoca, Klebs. ornitholytica, Klebs. planticola, Klebs. ozaenae, Klebs. terrigena, Klebs. granulomatis, (Calymmatobacterium granulomatis and Klebsiella rhinoscleromatis), the genus Proteus (e.g., Pr. mirabilis, Pr. rettgeri and Pr. vulgaris), the genus Providencia (e.g., Providencia alcalifaciens, Providencia rettgeri and Providencia stuartii), the genus Serratia (e.g., Serratia marcescens and Serratia liquifaciens) and the genus Yersinia (e.g., Yersinia enterocolitica). enterocolitica, Yersinia pestis and Yersinia pseudotuberculosis); enterococci (e.g., Enterococcus avium, Enterococcus casseliflavus, Enterococcus secerosum,Enterococcus cecorum, Enterococcus dispar, Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Enterococcus flavescens, Enterococcus gallinarum, Enterococcus hirae, Enterococcus malodoratus, Enterococcus mundtii, Enterococcus pseudoavium, Enterococcus raffinosus and Enterococcus solitarius. solitarius); Helicobacter spp. (e.g., Helicobacter pylori, Helicobacter cinaedi, and Helicobacter fennelliae); Acinetobacter spp. (e.g., Acinetobacter baumanii, Acinetobacter calcoaceticus, Acinetobacter haemolyticus, Acinetobacter johnsonii, Acinetobacter junii, Acinetobacter lwoffi, and Acinetobacter radioresistens); Pseudomonas spp. (e.g., Ps. aeruginosa, aeruginosa), Pseudomonas maltophilia (Stenotrophomonas maltophilia), Pseudomonas alcaligenes (Ps.alcaligenes, Pseudomonas chlororaphis, Pseudomonas fluorescens, Pseudomonas luteola, Pseudomonas mendocina, Pseudomonas monteilii, Pseudomonas oryzihabitans, Pseudomonas pertocinogena, Pseudomonas pseudalcaligenes, Pseudomonas putida and Pseudomonas stutzeri; Bacteriodes fragilis fragilis; Peptococcus spp. (e.g., Peptococcus niger); Peptostreptococcus spp.; Clostridium spp. (e.g., Clostridium perfringens, Clostridium difficile, Clostridium botulinum, Clostridium tetani, Clostridium absonum, Clostridium argentinense, Clostridium baratii, Clostridium bifermentans, Clostridium beijerinckii, Clostridium butyricum, Clostridium cadaveris, cadaveris, Clostridium carnis, Clostridium ceratum, Clostridium clostridioforme, Clostridium cochlearium, Clostridium cocleatum, Clostridium fallax, Clostridium ghonii, Clostridium glycolicumglycolicum, Clostridium haemolyticum, Clostridium hastiforme, Clostridium histolyticum, Clostridium indolis, Clostridium innocuum, Clostridium irregulare, Clostridium leptum, Clostridium limosum, Clostridium malenominatum, Clostridium novyi, Clostridium oroticum, Clostridium paraputrificum, Clostridium piliforme, Clostridium putrefaciens putrefasciens, Clostridium ramosum, Clostridium septicum, Clostridium sordelii, Clostridium sphenoides, Clostridium sporogenes, Clostridium subterminale, Clostridium symbiosum and Clostridium tertium; Mycoplasma species (e.g., Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium and Mycoplasma urealyticum); Mycobacterium spp. (e.g., Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium fortuitum, Mycobacterium marinum)marinum, Mycobacterium kansasii, Mycobacterium chelonae, Mycobacterium abscessus, Mycobacterium leprae, Mycobacterium smegmitis, Mycobacterium africanum, Mycobacterium alvei, Mycobacterium asiaticum, Mycobacterium aurum, Mycobacterium bohemicum Mycobacterium bohemicum, Mycobacterium bovis, Mycobacterium branderi, Mycobacterium brumae, Mycobacterium celatum, Mycobacterium chubense, Mycobacterium confluentis, Mycobacterium conspicuum, Mycobacterium cookii, Mycobacterium flavescens, Mycobacterium gadium, Mycobacterium gastri gastri, Mycobacterium genavense, Mycobacterium gordonae, Mycobacterium goodii, Mycobacterium haemophilumhaemophilum, Mycobacterium hassicum, Mycobacterium intracellulare, Mycobacterium interjectum, Mycobacterium heidelberense, Mycobacterium lentiflavum, Mycobacterium malmoense, Mycobacterium microgenicum, Mycobacterium microti, Mycobacterium mucogenicum, Mycobacterium neoaurum neoaurum, Mycobacterium nonchromogenicum, Mycobacterium peregrinum, Mycobacterium phlei, Mycobacterium scrofulaceum, Mycobacterium shimoidei, Mycobacterium simiae, Mycobacterium szulgai, Mycobacterium terrae, Mycobacterium thermoresistabile, Mycobacterium triplex triplex), Mycobacteria Mycobacterium triviale, Mycobacterium tusciae, Mycobacterium ulcerans, Mycobacterium vaccae, Mycobacterium wolinskyi, and Mycobacterium xenopi; Haemophilus spp. (e.g., Haemophilus influenzae, Haemophilus ducreyi, Haemophilus aegyptius, Haemophilus parainfluenzae, Haemophilus haemolyticus, Haemophilus Actinobacillus species (e.g., Actinobacillus actinomycetemcomitans, Actinobacillus equuli, Actinobacillus hominis, Actinobacillus lignieresii, Actinobacillus suis, and Actinobacillus ureae); Actinomyces species (e.g., Actinomyces israelii); Brucella species (e.g., Brucella abortus, Brucella canis, Brucella canis, Brucella melintensis and Brucella suis);Campylobacter spp. (e.g., Campylobacter jejuni, Campylobacter coli, Campylobacter lari, and Campylobacter fetus); Listeria monocytogenes; Vibrio spp. (e.g., Vibrio cholerae, and Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio carchariae, Vibrio fluvialis, Vibrio furnissii, Vibrio holisae, Vibrio hollisae, Vibrio metschnikovii, Vibrio mimicus and Vibrio vulnificus; Erysipelothrix rhusopathiae; Corynebacterium (e.g. Corynebacterium diphtheriae, Corynebacterium jeikeum and Corynebacterium urealyticum);Spirochetaceae, for example the genus Borrelia (e.g. Borrelia recurrentis, Borrelia burgdorferi, Borrelia afzelii, Borrelia andersonii, Borrelia bissettii, Borrelia garinii, Borrelia japonica, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, Borrelia valaisiana, Borrelia caucasiaca, Borrelia caucasica, Borrelia crocidurae, Borrelia duttoni, Borrelia graingeri, Borrelia hermsii, Borrelia hispanica, Borrelia latyschewii, Borrelia mazzottii, Borrelia parkeri, Borrelia persica, Borrelia turicatae and Borrelia venezuelensis) and the genus Treponema (Treponema pallidum ssp. pallidum, Treponema pallidum ssp. endemicum, Treponema pallidum ssp. pertenue and Treponema carateum);The genus Pasteurella (e.g., Pasteurella aerogenes, Pasteurella bettyae, Pasteurella canis, Pasteurella dagmatis, Pasteurella gallinarum, Pasteurella haemolytica, Pasteurella multocida multocida, Pasteurella multocida gallicida, Pasteurella multocida septica, Pasteurella pneumotropica and Pasteurella stomatis) stomatis); the genus Bordetella (e.g. Bordetella bronchiseptica, Bordetella hinzii, Bordetella holmseii, Bordetella parapertussis, Bordetella pertussis and Bordetella trematum); the family Nocardiaceae, for example the genus Nocardia (e.g. Nocardia asteroides and Nocardia brasiliensis); the genus Rickettsia (e.g. Ricksettsii or Coxiella burnetii);Legionella spp. (e.g., Legionalla anisa, Legionalla birminghamensis, Legionalla bozemanii, Legionalla cincinnatiensis, Legionalla dumoffii, Legionalla feeleii, Legionalla gormanii, Legionalla hackeliae, Legionalla israelensis, Legionalla jordanis, Legionalla lansingensis, Legionalla longbeche, Legionalla longbeachae, Legionella maceachernii, Legionella micdadei, Legionella oakridgensis, Legionella pneumophila, Legionella sainthelensi, Legionella tucsonensis and Legionella wadsworthii; Moraxella catarrhalis; Cyclospora cayetanensis; Entamoeba histolytica; Giardia lamblia; Trichomonas vaginalis vaginalis);Toxoplasma gondii;Stenotrophomonas maltophilia;Burkholderia cepacia;Burkholderia mallei and Burkholderia pseudomallei; Francisella tularensis; Cardnerella spp. (e.g. Gardneralla vaginalis and Gardneralla mobiluncus); Streptobacillus moniliformis; Flavobacteriaceae, e.g. Capnocytophaga spp. (e.g. Capnocytophaga canimorsus, Capnocytophaga cynodegmi, Capnocytophaga gingivalis, Capnocytophaga granulosa ... granulosa, Capnocytophaga haemolytica, Capnocytophaga ochracea and Capnocytophaga sputigena; Bartonella spp. (Bartonella bacilliformis, Bartonella clarridgeiae, Bartonella elizabethae, Bartonella henselae, Bartonella quintana and Bartonella vinsonii arupensis);Leptospira (e.g., Leptospira biflexa, Leptospira borgpetersenii, Leptospira inadai, Leptospira interrogans, Leptospira kirschneri, Leptospira noguchii, Leptospira santarosai and Leptospira weilii); Spirillium (e.g., Spirillum minus);The genus Bacteroides (e.g., Bacteroides caccae, Bacteroides capillosus, Bacteroides coagulans, Bacteroides distasonis, Bacteroides eggerthii, Bacteroides forsythus, Bacteroides fragilis, Bacteroides merdae, Bacteroides ovatus, Bacteroides putredinis, Bacteroides pyogenes, Bacteroides pyogenes, Bacteroides splanchinicus, Bacteroides stercoris, Bacteroides tectus, Bacteroides thetaiotaomicron, Bacteroides uniformis, Bacteroides ureolyticus and Bacteroides vulgatus);The genus Prevotella (e.g., Prevotella bivia, Prevotella buccae, Prevotella corporis, Prevotella dentalis (Mitsuokella dentalis), Prevotella denticola, Prevotella disiens, Prevotella enoeca, Prevotella heparinolytica, Prevotella intermedia, Prevotella loeschii, Prevotella melaninogenica, Prevotella nigrescens, Prevotella nigrescens, Prevotella oralis, Prevotella oris, Prevotella oulora, Prevotella tannerae, Prevotella venoralis and Prevotella zoogleoformans; Porphyromonas spp. (e.g., Porphyromonas asaccharolytica, Porphyromonas cangingivalis, Porphyromonas cano; ris, Porphyromonas cansulci, Porphyromonas catoniae, Porphyromonas circumdentaria, Porphyromonas crevioricanis, Porphyromonas endodontalis, Porphyromonas gingivalis, Porphyromonas gingivicanis, Porphyromonas levii and Porphyromonas macacae); Fusobacterium species (e.g. Fusobacterium gonadiaformans (F. gonadiaformans, Fusobacterium mortiferum, Fusobacterium naviforme, Fusobacterium necrogenes, Fusobacterium necrophorum necrophorum, Fusobacterium necrophorum fundiliforme, Fusobacterium nucleatum nucleatum, Fusobacterium nucleatum fusiforme, Fusobacterium nucleatum polymorphum, Fusobacterium nucleatum vincentii vincentii, Fusobacterium periodonticum, Fusobacterium russii, Fusobacterium ulcerans and Fusobacterium varium.varium); Chlamydia (e.g., Chlamydia trachomatis); Cryptosporidium (e.g., C. parvum, C. hominis, C. canis, C. felis, C. meleagridis, and C. muris); Chlamydophila (e.g., Chlamydophila abortus, (Chlamydia psittaci), Chlamydophila pneumoniae, (Chlamydia pneumoniae) and Chlamydophila psittaci (Chlamydia psittaci); the genus Leuconostoc (e.g., Leuconostoc citreum, Leuconostoc cremoris, Leuconostoc dextranicum, Leuconostoc lactis, Leuconostoc mesenteroides and Leuconostoc pseudomesenteroides); the genus Gemella (e.g., Gemella bergeri, Gemella haemolysans, Gemella haemolysans, Gemella morbillorum and Gemella sanguinis); and Ureaplasma species (e.g., Ureaplasma parvum and Ureaplasma urealyticum).

[0030] Preferably, the bacterial infection treated by the combinations described herein is a Gram-negative infection. Particular Gram-negative bacteria treatable using the combinations of the present invention include the following: Enterobacteriaceae, such as Escherichia coli, Klebsiella (e.g., Klebs. pneumoniae and Klebs. oxytoca) and Proteus (e.g., Proteus mirabilis, Proteus rettgeri and Proteus vulgaris); Haemophilus influenzae; Mycobacterium, such as Mycobacterium tuberculosis; and Enterobacter (e.g., Enterobacter cloacae). Preferably, the bacteria are enterobacteria, such as Escherichia coli and Klebsiella (e.g., Klebs. pneumoniae and Klebs. oxytoca). Particularly preferred are Escherichia coli and Klebs. pneumoniae (e.g., Klebs. Pneumoniae subsp. pneumoniae).

[0031] In all embodiments, it is preferred that the combination therapy is synergistic compared to the administration of either component of the combination alone.

[0032] The combinations of the invention are particularly useful in the treatment of (multiple) drug resistant ((M)DR) bacteria. For Enterobacteriaceae, drug resistance is most often developed against carbapenemases, i.e. carbapenemase resistant strains and "extended spectrum β-lactamase" (ESBL) strains, such as New Delhi metallo-β-lactamase-1 (NDM-1) resistant Klebsiella pneumoniae and NDM-1 Escherichia coli.

[0033] It should be noted that while the claimed combinations can first be shown to be functional in the treatment of (M)DR strains, they can then be used to treat non-resistant strains. This is particularly beneficial since the first-line therapy for Enterobacteriaceae, such as Escherichia coli and Klebsiella (e.g., Klebs. pneumoniae and Klebs. oxytoca), is expensive patent-protected antimicrobial drugs. Substituting such "prescription" drugs with "generic" antibiotic combinations would be useful from a therapeutic standpoint as well as a financial / economic standpoint at a time when governments are seeking to reduce healthcare costs.

[0034] The combinations of the present invention may be used to treat infections associated with any of the above bacterial organisms, and in particular they may be used to kill proliferative and / or clinically latent microorganisms associated with such infections, e.g. gram-negative bacterial infections.

[0035] Particular diseases which can be treated using the combinations of the invention include those caused by gram-negative bacteria, such as abscesses, asthma, bacterial dysentery, bacterial conjunctivitis, bacterial keratitis, bacterial vaginosis, bone and joint infections, bronchitis (acute or chronic), brucellosis, burns, cat scratch fever, cellulitis, chancroid, cholangitis, cholecystitis, cystic fibrosis, cystitis, nephritis, diffuse panbronchiolitis, dental caries, upper respiratory tract disease, sinusitis, endocarditis, endometritis, typhoid fever, and the like. fever), enteritis, epididymitis, epiglottitis, eye infections, furuncles, Gardnerella vaginitis, gastrointestinal infections (gastroenteritis), genital infections, gingivitis, gonorrhea, granuloma inguinale, Haverhill fever, infected burns, infections after dental surgery, infections of the oral area, infections associated with prosthetic devices, intra-abdominal abscesses, legionnaires' disease, leptospirosis, listeriosis, liver abscess, Lyme disease, lymphogranuloma venereum, mastitis, mastoiditis, meningitis and infections of the nervous system, non-specific urethritis, eye inflammation (e.g. ophthalmia neonatorum) , osteomyelitis, otitis (e.g., otitis externa and otitis media), orchitis, pancreatitis, paronychia, pelvic peritonitis, peritonitis, peritonitis associated with appendicitis, pharyngitis, pleural effusion, pneumonia, postoperative wound infection, postoperative gas gangrene, prostatitis, pseudomembranous colitis, psittacosis, pyelonephritis, Q fever, rat-bite fever, Litter's disease, salmonellosis, salpingitis, septic arthritis, septic infection, septicemia, systemic infection, tonsillitis, trachoma, typhoid, urethritis, urinary tract infection, wound infection; or Escherichia coli coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Proteus rettgeri, Proteus vulgaris, Haemophilus influenzae, Enterococcus faecalis, Enterococcus faecium, and Enterobacter cloacae.

[0036] In one embodiment the combination of the present invention is used to treat urinary tract infections.

[0037] It will be appreciated that reference herein to "treatment" extends to prophylaxis as well as the treatment of an existing disease or condition.

[0038] As used herein, the term "pharmaceutical acceptable derivative" means (a) a pharma- ceutically acceptable salt; and / or (b) Solvates (hydrates, etc.) means.

[0039] Pharmaceutically acceptable salts of the compounds included in the combination of the present invention include suitable acid addition or base salts thereof. A review of suitable pharmaceutical salts can be found in Berge et al, J Pharm Sci, 66, 1-19 (1977).

[0040] Suitable acid addition salts include carboxylates (e.g., formate, acetate, trifluoroacetate, propionate, isobutyrate, heptanoate, decanoate, caprate, caprylate, stearate, acrylate, caproate, propiolate, ascorbate, citrate, glucuronate, glutamate, glycolate, α-hydroxybutyrate, lactate, tartrate, phenylacetate, mandelate, phenylpropionate, phenylbutyrate, benzoate, chlorobenzoate, methylbenzoate, hydroxybenzoate, methoxybenzoate, dinitrobenzoate, o-acetoxybenzoate, salicylate, nicotinate, isonicotinate, cinnamate, oxalate, malonate, succinate, sucrose ... Suitable base salts include salts of the following basic salts: berates, sebacates, fumarates, malates, maleates, hydroxymaleates, hippurates, phthalates or terephthalates), halides (e.g. chlorides, bromides or iodides), sulfonates (e.g. benzenesulfonates, methyl-, bromo- or chloro-benzenesulfonates, xylenesulfonates, methanesulfonates, ethanesulfonates, propanesulfonates, hydroxyethanesulfonates, 1- or 2-naphthalenesulfonates or 1,5-naphthalenedisulfonates) or sulfates, pyrosulfates, bisulfates, sulfites, hydrogensulfites, phosphates, monohydrogenphosphates, dihydrogenphosphates, metaphosphates, pyrophosphates or nitrates. Suitable base salts include metal salts, e.g. sodium salts, calcium salts and amine salts.

[0041] For example, tetracycline hydrochloride, chlortetracycline hydrochloride, oxytetracycline hydrochloride, oxytetracycline hydrate, oxytetracycline dihydrate, demeclocycline hydrochloride, demeclocycline hydrochloride hydrate, meclocycline sulfosalicylate, methacycline hydrochloride, minocycline hydrochloride, doxycycline hyclate, doxycycline hydrochloride, doxycycline monohydrate, tigecycline hydrate, or sarecycline hydrochloride.

[0042] As used herein, the term "prodrug" refers to an antimicrobial compound in which one or more groups have been modified such that the modifications are reversible upon administration to a human or mammalian subject. Such reversal is usually effected by enzymes naturally present in such subjects, although a second agent can be administered along with such a prodrug to effect such reversal in vivo.

[0043] Examples of such modifications include ester formation (e.g., any of those described above), where reversal can be accomplished by, for example, an esterase. Other such systems will be known in the art. For example, zidovudine is a prodrug that must be phosphorylated to its active 5'-triphosphate metabolite.

[0044] The present invention includes the use of pharma- ceutically acceptable derivatives and prodrugs thereof.

[0045] The present invention also includes, where appropriate, all enantiomers and tautomers of the compounds. Compounds that have optical properties (one or more chiral carbon atoms) or tautomeric characteristics will be recognized by those skilled in the art. The corresponding enantiomers and / or tautomers can be isolated or prepared by methods known in the art.

[0046] Some of the compounds included in the combinations of the present invention can exist as stereoisomers and / or geometric isomers, e.g., they can have one or more asymmetric and / or geometric centers, and therefore can exist in two or more stereoisomeric and / or geometric isomeric forms. The present invention contemplates the use of all individual stereoisomers and geometric isomers of the inhibitors, as well as mixtures thereof. The terms used in the claims encompass these forms, provided that they retain the appropriate functional activity (although not necessarily to the same degree).

[0047] The present invention also includes all suitable isotopic forms of the compound or its pharma- ceutically acceptable salts. An isotopic form or its pharma- ceutically acceptable salt is defined as one in which at least one atom is replaced by an atom having the same atomic number but an atomic mass different from the atomic mass usually found in nature. Examples of isotopes that can be incorporated include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, fluorine and chlorine, e.g., 2 H, 3 H, 13 C. 14 C. 15 N, 17 O. 18 O. 31 P, 32 P, 35 S, 18 F and 36 Cl. Certain isotopic forms, e.g. 3 H or 14 Incorporating a radioactive isotope, such as C, is useful in drug and / or substrate tissue distribution studies. Tritiated, i.e. 3 H, and carbon-14, i.e. 14 C isotope is particularly preferred as it is easy to prepare and detectable. Additionally, deuterium, i.e. 2 Substitution with isotopes such as H may be preferred in some circumstances due to the potential for greater metabolic stability and therefore certain therapeutic advantages, such as increased in vivo half-life or reduced dosage requirements. Isotopic forms can be prepared by conventional procedures using the appropriate isotopic forms of suitable reagents.

[0048] The compounds used in the combinations of the present invention, including pharma- ceutically acceptable derivatives or prodrugs, are commercially available and / or can be prepared by synthetic methods known in the art. Zidovudine, tetracycline, tetracycline hydrochloride, chlortetracycline, chlortetracycline hydrochloride, oxytetracycline, oxytetracycline hydrochloride, oxytetracycline hydrate, oxytetracycline dihydrate, demeclocycline hydrochloride, demeclocycline hydrochloride hydrate, meclocycline sulfosalicylate, methacycline hydrochloride, minocycline hydrochloride, doxycycline, doxycycline hyclate, doxycycline hydrochloride, doxycycline monohydrate, tigecycline, tigecycline hydrate and sarecycline hydrochloride are available, for example, from Sigma-Aldrich®.

[0049] Other commercial suppliers are known in the art.

[0050] Zidovudine is 1-[(2R,4S,5S)-4-azido-5-(hydroxymethyl)oxolan-2-yl]-5-methylpyrimidine-2,4-dione and is available by prescription under the trade name Retrovir®. It is also known as 3'-azido-3'-deoxythymidine or "AZT" and has the following chemical structure:

[0051] [ka]

[0052] Tetracycline is an antibiotic used to treat many infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. It is taken orally and has broad-spectrum antibacterial activity. It was originally produced from a bacterium of the Streptomyces type, and is available in tablets, particularly under the trade name Sumycin, as tetracycline hydrochloride. Its IUPAC chemical name is (4S,6S,12aS)-4-(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxonaphthacene-2-carboxamide.

[0053] The chemical structure of tetracycline is:

[0054] [ka]

[0055] Chlortetracycline is a tetracycline substituted with chlorine on the phenol ring. It was the first tetracycline identified and is available under the trade name Aureomycin. It has the IUPAC chemical name (4S,4aS,5aS,6S,12aR)-7-chloro-4-(dimethylamino)-1,6,10,11,12a-pentahydroxy-6-methyl-3,12-dioxo-4,4a,5,5a-tetrahydrotetracene-2-carboxamide and the following chemical structure:

[0056] [ka]

[0057] Oxytetracycline was the second broad-spectrum tetracycline group antibiotic to be discovered. It is used to treat infections caused by Chlamydia, such as the chest infection psittacosis, the eye infection trachoma, and the genital infection urethritis, as well as infections caused by Mycoplasma, such as pneumonia. Oxytetracycline is also used to treat acne and infections caused by Haemophilus influenzae, such as chronic bronchitis. It is available in tablets as oxytetracycline dihydrate, or as an ointment as oxytetracycline hydrochloride combined with hydrocortisone (Terra-Cortril Ointment). It has the IUPAC chemical name (4S,4aR,5S,5aR,6S,12aS)-4-(dimethylamino)-3,5,6,10,11,12a-hexahydroxy-6-methyl-1,12-dioxo-4,4a,5,5a,6,12,12a-octahydrotetracene-2-carboxamide and has the following chemical structure:

[0058] [ka]

[0059] Demeclocycline is available under the trade names Declomycin, Declostatin, Ledermycin, Biotercyclin, Deganol, Detclo, Detravis, Meciclin, Mexocine and Clortetrin. It is a tetracycline antibiotic produced from a mutant strain of Streptomyces aureofaciens. Demeclocycline is indicated for the treatment of various bacterial infections, such as Lyme disease, acne, and bronchitis. Its IUPAC chemical name is (4S,4aS,5aS,6S,12aS)-7-chloro-4-(dimethylamino)-3,6,10,12,12a-pentahydroxy-1,11-dioxo-1,4,4a,5,5a,6,11,12a-octahydro-2-tetracenecarboxamide and has the following structure:

[0060] [ka]

[0061] Lymecycline is a broad-spectrum antibiotic sold by Galderma and is used to treat a variety of infections. Lymecycline is available in capsule form and is sold under various trade names, such as Tetralysal. Its IUPAC name is (2S)-6-[[[(4S,4aS,5aS,6S,12aR)-4-(dimethylamino)-1,6,10,11,12a-pentahydroxy-6-methyl-3,12-dioxo-4,4a,5,5a-tetrahydrotetracene-2-carbonyl]amino]methylamino]-2-aminohexanoic acid and has the following structure:

[0062] [ka]

[0063] Meclocycline is a topical tetracycline antibiotic. It has the IUPAC name (4S,4aR,5S,5aR,12aR)-7-chloro-4-(dimethylamino)-1,5,10,11,12a-pentahydroxy-6-methylidene-3,12-dioxo-4,4a,5,5a-tetrahydrotetracene-2-carboxamide and the following chemical structure:

[0064] [ka]

[0065] Methacycline is used as a precursor in the industrial synthesis of doxycycline hydrate, which is itself a tetracycline antibiotic. It is available under the trade names Esarondil, Physiomycine, Rotilen, among others. Its IUPAC name is (4S,4aR,5S,5aR,12aR)-4-(dimethylamino)-1,5,10,11,12a-pentahydroxy-6-methylidene-3,12-dioxo-4,4a,5,5a-tetrahydrotetracene-2-carboxamide and its chemical structure is:

[0066] [ka]

[0067] Minocycline, sold under the trade name Minocin, among others, is a tetracycline antibiotic used to treat many bacterial infections, including pneumonia. It is also used to treat acne and rheumatoid arthritis, along with other skin infections, such as MRSA and Lyme disease. Minocycline is a tetracycline analog that has a dimethylamino group at the 7-position and lacks the methyl and hydroxy groups at the 5-position. The IUPAC name for minocycline is (4S,4aS,5aR,12aR)-4,7-bis(dimethylamino)-1,10,11,12a-tetrahydroxy-3,12-dioxo-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide, and it has the following chemical structure:

[0068] [ka]

[0069] Rolitetracycline is a tetracycline antibiotic that is an N-Mannich base prodrug made from tetracycline by condensation with pyrrolidine and formaldehyde. It is available under the trade names Reverin or Synterin and has the IUPAC name (2Z,4S,4aS,5aS,6S,12aS)-4-dimethylamino-6,10,11,12a-tetrahydroxy-2-[hydroxy-(pyrrolidin-1-ylmethylamino)methylidene]-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione and the following chemical structure:

[0070] [ka]

[0071] Doxycycline is an antibiotic used to treat infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, early Lyme disease, cholera, and syphilis, among many other infections. It is available under the trade names Doryx, Doxyhexal, and Doxylin, among others. It is a tetracycline in which the 5β hydrogen of tetracycline is replaced by a hydroxy group and the 6α hydroxy group is replaced by a hydrogen. The IUPAC name for doxycycline is (4S,4aR,5S,5aR,6R,12aR)-4-(dimethylamino)-1,5,10,11,12a-pentahydroxy-6-methyl-3,12-dioxo-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide, and its chemical structure is as follows:

[0072] [ka]

[0073] Tigecycline is an intravenous antibiotic for many bacterial infections. It is sold by Pfizer under the trade name Tygacil and is used to treat various types of bacterial infections, such as complicated skin and tissue infections, complicated intraperitoneal infections, and community-acquired bacterial pneumonia. It has the IUPAC name (4S,4aS,5aR,12aR)-9-[[2-(tert-butylamino)acetyl]amino]-4,7-bis(dimethylamino)-1,10,11,12a-tetrahydroxy-3,12-dioxo-4a,5a,6-tetrahydro-4H-tetracene-2-carboxamide and the following chemical structure:

[0074] [ka]

[0075] Eravacycline, known under the trade name Xerava (Tetraphase Pharmaceuticals), is a synthetic halogenated tetracycline antibiotic administered parenterally. It has broad-spectrum activity against a variety of Gram-positive and Gram-negative bacteria, including multidrug-resistant strains such as MRSA and carbapenem-resistant Enterobacteriaceae. The IUPAC name for eravacycline is (4S,4aS,5aR,12aR)-4-(dimethylamino)-7-fluoro-1,10,11,12a-tetrahydroxy-3,12-dioxo-9-[(2-pyrrolidin-1-ylacetyl)amino]-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide, and it has the following chemical structure:

[0076] [ka]

[0077] Sarecycline (brand name Seysara) is an orally administered tetracycline antibiotic approved by the FDA for the treatment of moderate to severe acne vulgaris. It has the IUPAC name (4S,4aS,5aR,12aR)-4-(dimethylamino)-1,10,11,12a-tetrahydroxy-7-[[methoxy(methyl)amino]methyl]-3,12-dioxo-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide and the following chemical structure:

[0078] [ka]

[0079] Omadacycline is a broad-spectrum antibiotic that belongs to the aminomethylcycline subclass of tetracycline antibiotics. Both omadacycline and sarecycline are third-generation tetracycline compounds. Omadacycline is known by the trade name Nuzyra and is used orally to treat moderate to severe infections such as community-acquired pneumonia and acute bacterial skin and skin structure infections. The IUPAC name for omadacycline is (4S,4aS,5aR,12aR)-4,7-bis(dimethylamino)-9-[(2,2-dimethylpropylamino)methyl]-1,10,11,12a-tetrahydroxy-3,12-dioxo-4a,5,5a,6-tetrahydro-4H-tetracene-2-carboxamide, and it has the following chemical structure:

[0080] [ka]

[0081] In various embodiments of the invention, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, lymecycline, meclocycline, methacycline, minocycline, rolitetracycline, doxycycline, tigecycline, eravacycline, sarecycline, omadacycline, and pharmaceutically acceptable derivatives and prodrugs thereof.

[0082] In a preferred embodiment, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, meclocycline, methacycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a more preferred embodiment, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, demeclocycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. In a most preferred embodiment, the tetracycline antibiotic is selected from the group consisting of tetracycline, chlortetracycline, oxytetracycline, doxycycline, and pharmaceutically acceptable derivatives and prodrugs thereof. For example, the tetracycline antibiotic can be doxycycline or a pharmaceutically acceptable derivative or prodrug thereof.

[0083] The compounds for use according to the present invention can be administered as bulk substances, but are preferably provided in the form of pharmaceutical compositions.The compounds can be used as separate formulations or as a single combined formulation.When combined in the same formulation, it will be clear that the two compounds must be stable and compatible with each other and with the other components of the formulation.

[0084] The formulations of the present invention include those suitable for oral, parenteral (e.g. subcutaneous, intrathecal, intramuscular and intravenous, e.g. depot, etc., by injection or depot tablet), and rectal administration, or in a form suitable for inhalation or insufflation administration. The most suitable route of administration may depend on the condition and disorder of the patient. Preferably, the compositions of the present invention are formulated for oral administration.

[0085] The formulations can be conveniently provided in unit dosage forms and can be prepared by any method known in the art of pharmacy, for example, as described in "Remington: The Science and Practice of Pharmacy", Lippincott Williams and Wilkins, 21st Edition, (2005). A suitable method includes combining the active ingredient with the carrier, which constitutes one or more excipients. In general, the formulations are prepared by uniformly and intimately admixing the active ingredient with liquid carriers or finely divided solid carriers, or both, and then shaping the mixture, if necessary, into the desired formulation. It will be apparent that when these two active ingredients are administered independently, each can be administered by different means.

[0086] When formulated with excipients, the active ingredient may be present in a concentration of 0.1 to 99.5% (such as 0.5 to 95%) by weight of the total mixture, conveniently 30 to 95% for tablets and capsules, and 0.01 to 50% (e.g. 3 to 50%) for liquid formulations.

[0087] Formulations suitable for oral administration can be presented as discrete units such as capsules, cachets or tablets (e.g., chewable tablets, particularly for pediatric administration), each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or suspension in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water or water-in-oil emulsion. The active ingredient may also be presented as a bolus, electuary, or paste.

[0088] Tablets can be produced by compression or molding, optionally with one or more excipients. Compressed tablets can be produced by compressing the active ingredient in a free-flowing form, such as powder or granules, in a suitable machine, optionally with other conventional excipients, such as binders (e.g., syrup, acacia, gelatin, sorbitol, tragacanth, starch paste, polyvinylpyrrolidone and / or hydroxymethylcellulose), fillers (e.g., lactose, sugar, microcrystalline cellulose, corn starch, calcium phosphate and / or sorbitol), lubricants (e.g., magnesium stearate, stearic acid, talc, polyethylene glycol and / or silica), disintegrants (e.g., potato starch, croscarmellose sodium and / or sodium starch glycolate) and wetting agents (e.g., sodium lauryl sulfate). Molded tablets can be produced by molding a mixture of the powdered active ingredient with an inert liquid diluent in a suitable machine. The tablets may be coated or scored and may be formulated so as to provide controlled release of the active ingredient, e.g. delayed, sustained or pulsed release, or a combination of immediate and controlled release.

[0089] Alternatively, the active ingredient can be incorporated into oral liquid preparations such as aqueous or oily suspensions, solutions, emulsions, syrups or elixirs. Formulations containing the active ingredient can also be presented as a dry product for reconstitution with water or another suitable vehicle before use.

[0090] Such liquid formulations may contain conventional additives such as suspending agents (e.g., sorbitol syrup, methylcellulose, glucose / sugar syrup, gelatin, hydroxymethylcellulose, carboxymethylcellulose, aluminum stearate gel, and / or hydrogenated edible fats), emulsifying agents (e.g., lecithin, sorbitan monooleate, and / or acacia), non-aqueous vehicles (e.g., edible oils such as almond oil, coconut oil, oily esters, propylene glycol, and / or ethyl alcohol) and preservatives (e.g., methyl or propyl p-hydroxybenzoate and / or sorbic acid).

[0091] The combinations for use according to the invention can be presented in a pack or dispenser device which can contain one or more unit dosage forms containing the active ingredients. The pack can, for example, comprise metal or plastic foil, such as a blister pack. When the compositions are intended to be administered as two separate compositions, they can be presented in the form of a twin pack.

[0092] Pharmaceutical compositions may also be prescribed to patients in "patient packs" that contain the entire course of treatment in a single package, usually a blister pack. Patient packs have the advantage over traditional prescriptions, where a pharmacist portions out a patient's supply of medication from a bulk supply, that the patient always has access to the package insert contained in the patient pack, which typically gets lost with traditional prescriptions. The inclusion of a package insert has been shown to improve patient compliance with physician's instructions.

[0093] Administration of the combination of the invention in a single patient pack, or patient packs for each composition, containing package inserts instructing the patient on the correct use of the invention is a desirable feature of the invention.

[0094] According to another embodiment of the invention there is provided a patient pack comprising at least one active agent of the combination according to the invention and an instruction leaflet with instructions for the use of the combination according to the invention.In another embodiment of the invention there is provided a double pack comprising, upon separate administration, an antimicrobial agent, preferably having biological activity against clinically latent microorganisms, and one or more compounds as disclosed herein, preferably having biological activity against clinically latent microorganisms.

[0095] The amount of active ingredient required for use in treatment varies depending on the nature of the disease being treated and the age and condition of the patient, and is ultimately at the discretion of the attending physician. In general, however, the dose used for treatment of an adult typically ranges from 0.02 to 5000 mg / day, preferably 1 to 1500 mg / day. The desired dose can be conveniently expressed as a single dose or as a divided dose administered at appropriate intervals, for example as two, three or more partial doses per day.

[0096] Suitable dosages and formulations for administration of zidovudine are described in the product labeling for Retrovir® oral solution or capsules, available at http: / / www.medicines.org.uk / emc / medicine / 12444 / SPC / Retrovir+250mg+Capsules / .

[0097] Suitable dosages and formulations for administration of tetracycline antibiotics are described, for example, in the product labeling of tetracycline tablets, oxytetracycline tablets or ointments such as oxytetracycline hydrochloride, demeclocycline hydrochloride capsules, lymecycline capsules, minocycline hydrochloride capsules or tablets, doxycycline hyclate capsules or tablets, doxycycline monohydrate capsules or tablets, or tigecycline powder for infusion solutions. Such labels can be readily found by those skilled in the art, for example by searching for tetracycline antibiotics at "https: / / www.medicines.org.uk / emc / browse-ingredients#".

[0098] Thus, this information would be readily available and understandable to one of ordinary skill in the art.

[0099] Biological testing Test procedures that can be used to determine the biological activity (e.g., bactericidal or antimicrobial activity) of an active ingredient include: (a) bactericidal activity against clinically latent bacteria; and (b) Antimicrobial activity against log-phase bacteria These include those known to those skilled in the art for measuring

[0100] With regard to (a) above, methods for measuring activity against clinically latent bacteria include measuring the minimum stationary bactericidal concentration ("MSC") or minimum dormant bactericidal concentration ("MDC") for a test compound under conditions known to those of skill in the art, such as those described in Nature Reviews, Drug Discovery 1, 895-910 (2002), the disclosure of which is incorporated herein by reference.

[0101] By way of example, WO2000 / 028074 describes a suitable method for screening compounds to determine their ability to kill clinically latent microorganisms. A representative method includes the following steps: (1) growing a bacterial culture to stationary phase; (2) selecting for a phenotypically resistant subpopulation by treating the stationary phase culture with one or more antimicrobial agents at a concentration and / or for a time sufficient to kill vegetative bacteria; (3) incubating samples of the phenotypically resistant subpopulation with one or more test compounds or drugs; and (4) assessing antimicrobial efficacy against phenotypically resistant subpopulations may include.

[0102] According to this method, the phenotypically resistant subpopulation can be viewed as representing clinically latent bacteria that remain metabolically active in vivo and can cause recurrent or progressive disease.

[0103] With regard to (b) above, methods for measuring activity against log-phase bacteria include measuring the minimum inhibitory concentration ("MIC") or minimum bactericidal concentration ("MBC") for the test compound under standard conditions (i.e., conditions known to those of skill in the art, such as those described in WO2005 / 014585, the disclosure of which is incorporated herein by reference). Specific examples of such methods are described below. EXAMPLES

[0104] In vitro synergistic effects of zidovudine (AZT) and doxycycline. The checkerboard method used in Example 1 was in accordance with the protocol described in detail in Antimicrob Chemo (2013) 68, 374-384. Zidovudine and doxycycline were obtained from commercial sources. The bacteria used were BAA2469 NDM-1 Escherichia coli, BAA2470 NDM-1 Klebsiella pneumoniae, BAA2471 NDM-1 Escherichia coli, BAA2472 NDM-1 Klebsiella pneumoniae, and NCTC13443 NDM-1 Klebsiella pneumoniae. All strains were obtained from commercial sources, and logarithmic phase growth of the bacteria was performed using methods known in the art.

[0105] The efficacy of the combinations of the present invention was examined by calculating the fractional inhibitory concentration index (FICI) of each combination as follows: (MIC of drug A, tested in combination) / (MIC of drug A, tested alone) + (MIC of drug B, tested in combination) / (MIC of drug B, tested alone)

[0106] Combination interactions were defined as follows: FICI ≦0.5 indicates synergy, FICI >0.5 but <4.0 indicates no interaction, and FICI >4.0 indicates antagonism.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] [Table 5]

[0112] [Table 6]

[0113] A MIC reduction of 4-fold or greater indicates synergy. Doxycycline + AZT showed synergy against all strains tested, for example, BAA2469 NDM-1 E. coli or BAA2470 NDM-1 K. pneumoniae, where the doxycycline MIC for those strains was 64 mg / L, when combined with 0.5 mg / L AZT, the MIC for those strains was reduced to 4, a reduction of 16-fold.

Claims

1. A combination comprising zidovudine or a pharma- ceutically acceptable salt and / or solvate thereof and the tetracycline antibiotic doxycycline or a pharma- ceutically acceptable salt and / or solvate thereof for use in the treatment of a microbial infection.

2. 2. The combination for use according to claim 1, wherein said combination is for use in killing proliferative microorganisms associated with a microbial infection.

3. 3. The combination for use according to claim 1 or claim 2, wherein the microbial infection is a bacterial infection and the microorganism is a bacterium.

4. The combination for use according to claim 3, wherein the infection is a gram-negative bacterial infection.

5. The combination for use according to any one of claims 1 to 4, wherein the infection is a urinary tract infection.

6. The combination for use according to any one of claims 1 to 5, wherein the bacterial infection is caused by the family Enterobacteriaceae.

7. The combination for use according to any one of claims 1 to 6, wherein the infection is caused by a drug-resistant strain of bacteria.

8. A pharmaceutical composition comprising a combination of zidovudine or a pharma- ceutical acceptable salt and / or solvate thereof and the tetracycline antibiotic doxycycline or a pharma- ceutical acceptable salt and / or solvate thereof, and a pharma- ceutical acceptable adjuvant, diluent or carrier, for use in the treatment of a microbial infection.

9. A product comprising zidovudine or a pharma- ceutically acceptable salt and / or solvate thereof and the tetracycline antibiotic doxycycline or a pharma- ceutically acceptable salt and / or solvate thereof as a combination drug for simultaneous, separate or sequential use in the treatment of microbial infections.

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