Prodrugs of boron compounds and their use in the treatment of bacterial infections

Abstract

This application describes prodrugs of antimicrobial organoboron compounds of Formula I, or salts thereof, and pharmaceutical compositions thereof, as well as methods of using and preparing them.

Description

Technical Field

[0001] This application describes a prodrug of an antibacterial boron organic compound, a pharmaceutical composition thereof, a method of use thereof, and a method of preparation thereof. Background Technology

[0002] The increasing prevalence of bacterial resistance necessitates the development of novel antimicrobial compounds to treat microbial infections. These novel drugs need to possess useful activity against major mammalian pathogens, including Gram-negative bacteria such as *Pseudomonas aeruginosa*, *Acinetobacter baumannii*, *Escherichia coli*, and *Klebsiella pneumoniae*, as well as major Gram-positive bacteria such as multidrug-resistant Staphylococcus and Streptococcus. Drugs acting through novel mechanisms of action are particularly advantageous in avoiding undesirable cross-resistance with existing drugs.

[0003] For many patients with bacterial infections, oral medications are the most suitable option. The advantages of oral administration over intravenous injection include the absence of catheter-related infections, lower drug costs, and reduced hidden costs, such as the need for healthcare professionals and equipment to administer intravenous antibiotics. For patients requiring long-term treatment, oral therapy is particularly important for improving patient adherence.

[0004] Several antibacterial boron organic compounds have been previously described in PCT applications WO 2008 / 157726 and WO 2010 / 080558 and US application US 2009 / 0227541. To date, these compounds have not been approved for use in human anti-infective therapy.

[0005] Boron-containing organic compounds (as shown below) are described in US application US2013 / 0165411. These compounds are particularly active against Gram-negative bacteria such as *Pseudomonas aeruginosa*, *Acinetobacter baumannii*, *Escherichia coli*, and *Klebsiella pneumoniae*. Furthermore, this type of molecule has shown good efficacy in a mouse model of *Pseudomonas aeruginosa* infection with neutropenia after subcutaneous administration. However, no oral formulations of this molecule have been reported to date. In fact, many antibiotics, including cephalosporins, can only be administered intravenously. Drugs with poor oral bioavailability are not suitable for oral drug development due to the lack of adequate drug exposure. Poor oral bioavailability may also require higher doses, which could cause additional side effects.

[0006]

[0007] There are two main approaches to improving membrane permeability, thereby enhancing the oral absorption of compounds. One involves altering the chemical structure, while the other involves developing formulations without changing the molecular structure. The former can be achieved by linking relatively small structurally modifying groups (such as alkyl or acyl groups) to suitable substituents (such as carboxyl or amino groups) within the drug to form a prodrug.

[0008] The preferred compounds provided in this application are stable in prodrug form prior to absorption, and exhibit better absorption due to their unique prodrug form. Upon administration to a mammal requiring treatment, these prodrug molecules are rapidly chemically and / or enzymatically converted into the active drug within body regions such as the intestine, liver, and / or plasma. This desired conversion to the active drug can occur during and / or after absorption.

[0009] However, it is difficult to develop an ideal prodrug that meets all the above conditions. For example, prodrugs with ester bonds may be more prone to hydrolysis, which may affect their chemical stability before absorption. Amide bonds can cause significant changes in physical properties, which in turn may negatively impact membrane permeability (such as oral absorption capacity). Furthermore, amide bonds are less prone to hydrolysis, which may affect the bioconversion of the compound to the active form and the plasma concentration of the active form. In addition, it is difficult to predict the pharmacokinetic characteristics of prodrugs because the enzymes controlling the bioconversion of prodrugs to the active form are substrate-specific; in particular, steric hindrance from the insertion of substituents for prodrug formation can prevent the enzyme reaction. For these reasons, it is impossible to predict how or whether a prodrug will increase the plasma concentration of the active form, whether a prodrug will increase membrane permeability, and / or whether a prodrug will be converted to the active form in vivo. Summary of the Invention

[0010] This application describes novel prodrugs of boron compounds that have high antibacterial activity against Gram-negative bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae.

[0011] It has been found that the prodrug described in this application enhances in vivo exposure to the corresponding active form, as demonstrated in animal experiments using the active form and the prodrug as test drugs.

[0012] In one aspect, this application provides compounds of formula I:

[0013]

[0014] Or its pharmaceutically acceptable salt, complex, or tautomer, wherein:

[0015] R 1 Selected from H, C 1-24 Alkyl-C(=O)-, C 1-24 Alkoxy-C(=O)-, C3-7 Cycloalkyl-C(=O)-, heteroalkyl-C(=O)-, aryl-C(=O)-, heteroaryl-C(=O)-, and (5-methyl-1,3-dioxacyclopenten-2-one-4-yl)methyl; and

[0016] R 2 Selected from C 1-24 Alkyl-C(=O)-, C 1-24 Alkoxy-C(=O)-, C 3-7 Cycloalkyl-C(=O)-, heteroalkyl-C(=O)-, aryl-C(=O)-, heteroaryl-C(=O)-, and (5-methyl-1,3-dioxacyclopenten-2-one-4-yl)methyl; or

[0017] R 1 and R 2 Together they form a heterocyclic group, wherein the heterocyclic group is selected from 1,4-dioxane, 2-C 1-6 -alkyl-1,4-dioxane, 2,2-bis(C 1-6 alkyl)-1,4-dioxane, 2-methyl-1,4-dioxane, 2-aryl-1,4-dioxane, 2-(2-carboxyphenyl)-1,4-dioxane, 2-(4-carboxyphenyl)-1,4-dioxane or 2-C 1-6 -alkylOC(=O)-1,4-dioxane; each of which is optionally surrounded by one to four R 3 replace;

[0018] R 3 Each time it appears, it is independently selected from groups including halogens, hydroxyl groups, C1-C6 alkyl groups, C3-C6 cycloalkyl groups, C1-C6 alkoxy groups, aryl groups, and heteroaryl groups; or

[0019] When bonded to adjacent carbons, the two Rs 3 The groups together with the carbons they are attached to form fused C3-C6 cycloalkyl groups; or when attached to the same carbon, the two R groups form fused C3-C6 cycloalkyl groups. 3 The groups, together with the carbon atoms they are attached to, form spiroC3-C6 cycloalkyl groups;

[0020] Each R 3 It can be optionally substituted independently with one to three fluorine, hydroxyl, or C1-C3 alkyl groups.

[0021] In a preferred embodiment of formula I, R 1 and R 2 They are all alkyl groups.

[0022] In another preferred embodiment of formula I, R 1 and R 2 They are all C1-C6 alkyl-C(=O)-.

[0023] In another aspect, this application provides compounds of formula II:

[0024]

[0025] Or its pharmaceutically acceptable salt; wherein:

[0026] R 4 Selected from C 1-24 Alkoxy-C(=O)-, C 3-7 Cycloalkyl-C(=O)-, heteroalkyl-C(=O)-, aryl-C(=O)-, heteroaryl-C(=O)- and (5-methyl-1,3-dioxacyclopenten-2-one-4-yl)methyl.

[0027] In another aspect, this application provides a pharmaceutical composition comprising a therapeutically effective amount of a compound of formula I or II, or a pharmaceutically acceptable salt, complex or tautomer thereof, and a pharmaceutically acceptable carrier.

[0028] In another aspect, this application provides a pharmaceutical composition comprising a compound of formula I or formula II or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.

[0029] In another aspect, this application provides a method for treating a mammalian microbial infection, comprising administering to a mammal requiring treatment a therapeutically effective amount of a compound of formula I or II, or a pharmaceutically acceptable salt, complex, or tautomer thereof. The compound of formula I or II, or a pharmaceutically acceptable salt, complex, or tautomer thereof, may be administered orally, parenterally, transdermally, topically, rectally, or intranasally as a pharmaceutical composition, said pharmaceutical composition comprising a solution or powder composition for inhalation.

[0030] In another aspect, the compound or a pharmaceutically acceptable salt, complex or tautomer thereof may be administered orally to mammals in the form of a pharmaceutical composition.

[0031] In another aspect, this application provides a method for treating mycobacterial microbial infections in humans or other warm-blooded animals by administering a therapeutically effective amount of a compound of formula I or II, or a pharmaceutically acceptable salt thereof, to a subject requiring treatment. The compound of formula I or II may be administered orally, parenterally, transdermally, topically, rectally, or intranasally as a pharmaceutical composition.

[0032] On the other hand, this application provides compositions and methods for treating microbial infections caused by microorganisms selected from Gram-negative bacteria, including but not limited to Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae.

[0033] In one embodiment, the method is used to treat skin, soft tissue, respiratory tract, blood, intra-abdominal, urinary, or eye infections.

[0034] In another aspect, this application provides novel intermediates and methods for preparing compounds of formula I. Detailed Implementation

[0035] Unless otherwise stated, the following terms used in the specification and claims have the following meanings.

[0036] The carbon atom content of various hydrocarbon-containing fractions is represented by prefixes indicating the minimum and maximum number of carbon atoms in that fraction, i.e., the prefix C. i-j This represents the carbon atom portion from the integers "i" to "j". Therefore, for example, C 1-7 Alkyl refers to an alkyl group having 1 to 7 carbon atoms (including 1 to 7).

[0037] The terms "alkyl" and "alkenyl" refer to both straight-chain and branched groups, but when referring to a single group, such as "propyl," only the straight-chain group is included, while branched isomers, such as "isopropyl," only the branched group is included. Alkyl, alkenyl, and other groups can optionally be selected from one, two, or three halogens, aryl, and hexyl groups. 1 Or Het 2 Substituents are substituted. Representative examples include, but are not limited to, difluoromethyl, 2-fluoroethyl, trifluoroethyl, -CH=CH-aryl, -CH=CH-Het. 1 , -CH2-phenyl, etc.

[0038] The term "cycloalkyl" refers to a cyclic, saturated, monovalent hydrocarbon group having 3-6 carbon atoms, such as cyclopropyl and cyclohexyl. Cycloalkyl groups may optionally be surrounded by one, two, or three groups selected from halogens, aryl groups, and hexyl groups. 1 Or Het 2 Substituents are substituted.

[0039] The term "heteroalkyl" refers to an alkyl or cycloalkyl group as defined above, having a component selected from N, O, or S(O). n Substituents of heteroatoms, where n is an integer from 0 to 2, including hydroxyl (OH), C 1-4 Alkoxy, amino, and thio (-SH) substituents, etc. Representative substituents include -NR. a R b OR a or -S(O) n R c , where R a It is hydrogen, C 1-4 Alkyl, C 3-6Cycloalkyl, optionally substituted aryl, optionally substituted heterocyclic, or -COR (where R is C 1-4 Alkyl); R b It is hydrogen, C 1-4 Alkyl group, -SO2R (where R is C) 1-4 Alkyl or C 1-4 Hydroxyalkyl), -SO2NRR' (where R and R' are independently hydrogen or C) 1-4 Alkyl group, -CONR'R" (where R' and R" are independently hydrogen or C). 1-4 Alkyl); n is an integer from 0 to 2; and R c It is hydrogen, C 1-4 Alkyl, C 3-6 cycloalkyl, optionally substituted aryl or NR a R b , where R a and R b As defined above. Representative examples include, but are not limited to, 2-methoxyethyl (-CH2CH2OCH3), 2-hydroxyethyl (CH2CH2OH), hydroxymethyl (-CH2OH), 2-aminoethyl (-CH2CH2NH2), 2-dimethylaminoethyl (CH2CH2NHCH3), benzyloxymethyl, thiophene-2-ylthiomethyl, etc.

[0040] The term "halogen" refers to fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0041] The term "aryl" refers to phenyl, biphenyl, or naphthyl, which may optionally be substituted with 1 to 3 substituents, said substituents being independently selected from halogens, -C 1-4 Alkyl, -OH, -OC 1-4 Alkyl group, -S(O) n C 1-4 Alkyl group, wherein n is 0, 1 or 2, -C 1-4 Alkyl NH2, -NHC 1-4 Alkyl, -C(=O)H or -C=N-OR d , where R d It is hydrogen or -C 1-4 alkyl.

[0042] Het 1 Each occurrence is independently a C-linked 5- or 6-membered heterocycle, containing 1 to 4 heteroatoms selected from oxygen, nitrogen, and sulfur. 2 Each time it appears, it is independently an N-linked 5 or 6-membered heterocycle with 1 to 4 nitrogen atoms and optionally an oxygen or sulfur atom within the ring.

[0043] "Optional" or "optionally" means that an event or situation described below may occur but does not have to occur, and the description includes instances where the event or situation occurs and instances where it does not occur. For example, "aryl group optionally mono- or di-substituted with alkyl" means that an alkyl group may but does not have to be present, and the description includes cases where the aryl group is mono- or di-substituted with an alkyl group and cases where the aryl group is not substituted with an alkyl group.

[0044] Compounds with the same molecular formula but different atomic bonding properties, sequences, or spatial arrangements are called "isomers." Isomers with different spatial arrangements of atoms are called "stereoisomers."

[0045] Stereoisomers that are not mirror images of each other are called "diastereomers," while stereoisomers that are not superimposed mirror images of each other are called "enantiomers." For example, when a compound has an asymmetric center, it is bonded to four different groups, and a pair of enantiomers is possible. Enantiomers can be characterized by the absolute configuration of their asymmetric center and described by the (R)- and (S)-steroidal chemistry rules of Cahn and Prelog, or by the plane of molecular rotational polarization, and are designated as dextrorotatory or levorotatory (i.e., (+) or (-)-isomers, respectively). Chiral compounds can exist as individual enantiomers or mixtures thereof. A mixture containing equal proportions of enantiomers is called a "racemic mixture."

[0046] The compounds described in this application may have one or more asymmetric centers; such compounds can therefore be produced as individual (R)- or (S)- stereoisomers or mixtures thereof. Unless otherwise stated, the description or naming of a particular compound in the specification and claims is intended to include its individual enantiomers and mixtures, racemic or other forms. Methods for determining stereochemistry and separating stereoisomers are well known in the art (see discussion in Chapter 4 of "Advanced Organic Chemistry," 4th edition, J. March, John Wiley and Sons, New York, 1992).

[0047] "Pharmaceutically acceptable carrier" refers to a carrier that can be used to prepare a pharmaceutical composition, which is generally safe and non-toxic, has no biological significance or other undesirable content, and includes carriers that can be used in veterinary and human pharmaceuticals. The term "pharmaceutically acceptable carrier" as used in the specification and claims includes one or more such carriers.

[0048] A "pharmaceutically acceptable salt" of a compound refers to a pharmaceutically usable salt that possesses the pharmacological activity required by the parent compound. Such salts include:

[0049] (1) Acid addition salts, formed from inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, etc.; or from organic acids such as acetic acid, propionic acid, hexanoic acid, cyclopentylpropionic acid, glycolic acid, pyruvic acid, lactic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, 3-(4-hydroxybenzoyl)benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, 1,2-ethanedisulfonic acid, 2-hydroxybenzoic acid, etc. Acetic acid, benzenesulfonic acid, 4-chlorobenzenesulfonic acid, 2-naphthalenesulfonic acid, 4-toluenesulfonic acid, camphorsulfonic acid, 4-methylbicyclo[2.2.2]oct-2-en-1-carboxylic acid, glucohepanoic acid, 4,4'-methylenebis(3-hydroxy-2-en-1-carboxylic acid), 3-phenylpropionic acid, trimethylacetic acid, tert-butylacetic acid, lauryl sulfate, gluconic acid, glutamic acid, hydroxynaphthoic acid, salicylic acid, stearic acid, mucoconic acid, etc.; or

[0050] (2) Salts formed when acidic protons present in the parent compound are replaced by metal ions, such as alkali metal ions, alkaline earth ions or aluminum ions; or salts formed by combination with organic bases such as ethanolamine, diethanolamine, triethanolamine, glycerolamine, N-methylglucosamine, etc.

[0051] The term "tautomer" refers to two or more forms or isomers of an organic compound that can interconvert through a common chemical reaction called tautomerization, often similar to the reaction described by Smith et al. in Advanced Organic Chemistry. 2001, 5th Ed. NY: Wiley Interscience., pp. 1218–1223. The concept of tautomerization is also known as tautomerization. Tautomerization can involve a change from a ring structure to an open structure, for example, as observed in the interconversion between the cyclic pyran form and the open-chain form of glucose via the formation and cleavage of CO bonds. The extent of tautomerization is often influenced by solvent effects, such as hydration with water and the acidity of the medium. Relevant processes involving cyclic boron compounds may involve the formation and cleavage of BO bonds, as follows:

[0052]

[0053] The “treatment” of the disease includes:

[0054] (1) Disease prevention, that is, preventing the development of clinical symptoms of the disease in mammals that may be exposed to or susceptible to the disease but have not yet experienced or exhibited symptoms of the disease.

[0055] (2) Suppressing the disease, that is, preventing or reducing the development of the disease or its clinical symptoms, or

[0056] (3) Relieve disease, that is, cause the disease or its clinical symptoms to subside.

[0057] "Therapeutic effective dose" refers to the amount of a compound that is sufficient to affect the treatment of a disease when administered to a mammal. The "therapeutic effective dose" varies depending on the compound, the disease and its severity, and the age and weight of the mammal being treated.

[0058] "Prodrug" refers to any compound that releases an active parent drug in vivo when taken by a mammalian subject, according to the compound described in this application. The prodrugs of the compounds of this invention are prepared by modifying the functional groups present in the compounds of this invention, such modification being capable of cleavage in vivo to release the parent compound. In some embodiments, the prodrug includes the compound described in this application, wherein the hydroxyl, thiol, amide, or amino groups in the compound are bound to any group capable of cleavage in vivo to regenerate free hydroxyl, amide, amino, or thiol groups, respectively.

[0059] The term "mammal" refers to all mammals, including humans, livestock, and companion animals.

[0060] "Patient" refers to an animal, such as a mammal, including non-primates (e.g., cows, pigs, horses, cats, dogs, rats, and mice) and primates (e.g., monkeys, such as cynomolgus monkeys, chimpanzees, and humans), and, for example, humans. In some implementations, the patient is a human.

[0061] The compounds described in this application are generally named according to the IUPAC or CAS nomenclature system. Abbreviations well known to those skilled in the art may be used (e.g., "Ar" for aryl, "Ph" for phenyl, "Me" for methyl, "Et" for ethyl, "h" for hour or hour, "rt" or "rt" for room temperature).

[0062] Illustrative Examples

[0063] The specific and preferred values ​​for groups, substituents, and ranges listed below are for illustrative purposes only; they do not exclude other defined values ​​for groups and substituents or other values ​​within the defined ranges.

[0064] In some of the preferred compounds described in this application, C 1-4 The alkyl group can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, or its isomers.

[0065] In some of the preferred compounds described in this application, C 3-6 The cycloalkyl group can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or its isomers.

[0066] In some of the preferred compounds described in this application, C 1-4 The heteroalkyl group can be hydroxymethyl, hydroxyethyl, or 2-methoxyethyl.

[0067] In some of the preferred compounds described in this application, the halogen may be fluorine (F) or chlorine (Cl).

[0068] A preferred group of compounds of formula I includes:

[0069]

[0070] Another preferred group of compounds of formula I includes:

[0071]

[0072] Another preferred group of compounds of formula I includes:

[0073]

[0074] It also includes another set of preferred compounds of formula I.

[0075]

[0076] In some embodiments, the preferred pharmaceutically acceptable salt of the compound is a hydrochloride salt.

[0077] General Synthesis Method

[0078] In some embodiments, the compounds described in this application can be prepared according to one or more of the methods discussed below. These methods can be used directly or can be significantly modified by a trained chemist to prepare the key intermediates and certain compounds described in this application.

[0079] Other general methods for preparing some bicyclic boron compounds are described, for example, in publications US applications US2013 / 0165411 and US2009 / 0227541 and PCT application WO 2010 / 080558.

[0080] It should also be understood that, if necessary, any racemic compound or intermediate described in this application can be isolated into asymmetric chiral materials of the desired optically active isomers using conventional methods, including but not limited to chiral liquid chromatography or co-crystallization with chiral auxiliary reagents (such as commercially available chiral acids or amines).

[0081] Suitable synthetic sequences can be readily selected based on the specific structures described in this application, but are also known within the realm of individual practice of organic synthesis, for example, methods summarized in available chemical databases, such as CAS Scifinder and Elesevier Reaxys. Based on these general methods, the preparation of the compounds described in this application is straightforward and can be practiced within the scope of general expertise. Some general synthetic methods for preparing the compounds described in this application are illustrated in Schemes 1-6 below (non-limiting, illustrative only).

[0082] A general method for synthesizing the compound of formula I described in this application is illustrated in general embodiment 1.

[0083] Option 1. Universal synthesis of prodrugs.

[0084]

[0085] Non-limiting examples of esterifying agents used for the conversion described in (a) include, but are not limited to, acyl chlorides, acid anhydrides, or acids having EDC;

[0086] The deprotecting agent used for the transformation described in (b) depends on the protecting group used. For example, in some embodiments, R a and R b Independently selected from H, Bn, Boc, Fmoc, Cbz, etc.

[0087] Other detailed synthetic methods for synthesizing the specific compounds described in this application are illustrated by the methods described in the following examples.

[0088] Example

[0089] The embodiments described in this application are illustrated in the following examples, which are intended to be illustrative and not to limit the scope of this disclosure. Common abbreviations familiar to those skilled in the art are used throughout. 1 ¹H NMR spectra (δ, ppm): Unless otherwise specified, recorded using DMSO-d6 on a 300 MHz instrument. Mass spectrometry data for positive ionization methods are provided. Unless otherwise specified, chromatography refers to silica gel chromatography. TLC refers to thin-layer chromatography. HPLC refers to reversed-phase HPLC. Unless otherwise specified, all reagents are either commercially available or prepared using conventional methods described in existing literature.

[0090] Example 1

[0091] (2S)-3-acetoxy-1-{[(3S)-3-(aminomethyl)-1-hydroxy-1,3-dihydrobenzo[2,1-c][1,2]oxobor-7-yl]oxy}propane-2-ylacetate hydrochloride

[0092]

[0093] Preparation scheme of the compound in Example 1:

[0094]

[0095] Intermediate 2. Ac2O (32 μL, 0.33 mmol) was added dropwise to a solution of intermediate 1 (60 mg, 0.26 mmol, prepared as described in US application US2013 / 0165411) and pyridine (31 μL, 0.33 mmol) in DCM (2 mL), and the resulting mixture was stirred for 2 hours. After the reaction was complete, the solvent was removed by concentration, and the residue was purified by pre-HPLC to give intermediate 2 (25 mg): MS (m / z): 438 [m+H].

[0096] Example 1

[0097] Intermediate 2 was dissolved in a 5M HCl (2 mL) solution of dioxane at room temperature, and the resulting mixture was stirred for 1 hour. The mixture was then lyophilized to give the compound of Example 1 (16.9 mg) as a pale yellow powder. MS (m / z): 338 [M+H]. 1 H NMR: (400MHz, D2O): 7.48 (t, J=8.0Hz, 1H); 7.01 (d, J=7.6Hz, 1H); 6.92 (dd, J=12.0, 8.0Hz, 1H); 5.35 (dd, J=7.4, 3 .0Hz, 1H); 4.35~4.17(m, 5H); 3.73~3.60(m, 1H); 3.56~3.51(m, 2H); 3.08~3.01(m, 1H); 1.99(s, 3H), 1.98(s, 3H).

[0098] The following compounds were synthesized according to the steps described in Example 2.

[0099]

[0100] Example 4

[0101] [(2S,6S)-2-(aminomethyl)-4-boron-3,5,8-trioxane[7.3.1.04,13]tetane-1(12),9(13),10-trien-6-yl]methyl-2-propionate methyl chloride

[0102]

[0103] The compound of Example 4 was prepared according to the method described in US application US2013 / 0165411.

[0104] Example 5

[0105] [(2S,6R)-2-(aminomethyl)-4-boron-3,5,8-trioxane[7.3.1.04,13]tetane-1(12),9(13),10-trien-6-yl]methanol hydrochloride

[0106]

[0107] The compound of Example 5 was prepared according to the method described in US application US2013 / 0165411.

[0108] Example 7

[0109] [(2S,6S)-2-(aminomethyl)-4-boron-3,5,8-trioxane[7.3.1.04,13]tetane-1(12),9(13),10-trien-6-yl]methyl acetate hydrogen chloride

[0110]

[0111] The compound of Example 7 was prepared according to the method described in US application US2013 / 0165411.

[0112] Example 8

[0113] [(2S,6S)-2-(aminomethyl)-4-boron-3,5,8-trioxane[7.3.1.04,13]tetadecan-1(12),9(13),10-trien-6-yl]methyl propionate hydrogen chloride

[0114]

[0115] The compound of Example 8 was prepared according to the method described in US application US2013 / 0165411.

[0116] Utility and Testing

[0117] The compound described in this application is a prodrug, which is expected to be converted into a parent boron compound to exert its antibacterial effect. The antibacterial activity of the parent boron compound has been disclosed in US Application US2013 / 0165411. Therefore, the compound described in this application is a useful antimicrobial agent and can be effective against many human and veterinary pathogens, including Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae.

[0118] The in vitro activity of the compounds described in this application can be assessed using standard testing procedures, such as the determination of the minimum inhibitory concentration (MIC) as described in the Approved Standard, Methods for Dilution, Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, 3rd ed., 1993, published by the National Clinical Laboratory Standards Committee in Villanova, Pennsylvania, USA. A low MIC value indicates high antimicrobial activity, while a high MIC value indicates reduced antimicrobial activity (in the latter case, a higher drug concentration is required to eradicate the pathogen). Generally, an MIC value of approximately ≤4-8 μg / mL indicates therapeutic potency (i.e., suitable for treatment) of the antimicrobial drug, while an MIC value ≥16 μg / mL indicates a lack of therapeutically useful activity for the tested compound.

[0119] The useful in vitro activity (potency) of the representative compounds described in this application against mycobacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae is shown in the MIC data in Table 1 below.

[0120] As can be clearly seen from the data in Table 1, the reference compound of Example 5 exhibits high activity (MIC range of 2-4 μg / mL) against many Gram-negative bacteria, including Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae. Typical prodrug derivatives, such as the prodrugs of Examples 5, including the compounds of Examples 2, 3, 4, and 8, are considered inactive.

[0121] Table 1. In vitro antibacterial activity of representative examples.

[0122]

[0123]

[0124] Besides in vitro activity (potency defined as MIC), the efficacy or ability to eradicate bacterial pathogens in vivo is crucial to the survival of mammals under treatment. It is well known that compounds with similar in vitro antimicrobial potency (MIC) can exhibit significantly different activities in vivo. This can result in some effective compounds producing the desired therapeutic effect, or others lacking any useful anti-infective effect. This is critical to actual treatment outcomes and is determined by a variety of factors influencing the behavior of compounds in vivo, such as their absorption, distribution, metabolism, and excretion.

[0125] In addition, in vivo activity (or efficacy) is usually the most critical activity for prodrug compounds, which are typically inactive in vitro and release their active drug upon administration to the mammal in need of treatment.

[0126] To establish the in vivo efficacy of the compounds described in this application, a mouse model of *Pseudomonas aeruginosa* lung infection was implemented by administering the test compounds in a manner similar to that described by Andes et al. in *Antimicrobial Agents and Chemotherapy*, 2002, 46(11), 3484-3489. In this model, a greater reduction in colony-forming units (CFU) indicated a more favorable therapeutic effect (more bacterial eradication), while a smaller reduction in CFU indicated a less favorable effect (less bacterial eradication). In vivo antimicrobial effect is also referred to as "efficacy," while the term "potency" is generally used for in vitro activity (expressed as MIC).

[0127] In lung infection of Pseudomonas aeruginosa ICR mice (mice were randomly assigned to groups of 6), the reference compound of Example 5 was administered orally at a dose of 10 mg / kg once daily. Compared with the untreated control group, the reference compound of Example 5 showed weak antibacterial efficacy and caused a 0.53 log decrease in CFU in the lungs. As prodrugs for oral administration, the compounds of Examples 2 and 8 were also administered orally by gavage at a dose of 10 mg / kg once daily. Although the prodrugs themselves did not have antibacterial efficacy, they showed good in vivo efficacy. Surprisingly, when administered at 10 mg / kg, the compounds of Examples 2 and 8 were significantly more effective than the reference compound of Example 5, with decreases in CFU in the lungs of 1.77 and 0.82 log, respectively. This data strongly supports the conversion of the prodrugs of Examples 2 and 8 to the reference compound of Example 5 to exert antibacterial activity after oral administration. This data also supports a high conversion rate.

[0128] Table 2. Data from a mouse model of Pseudomonas aeruginosa lung infection.

[0129]

[0130]

[0131] po, oral administration, refers to the oral suspension used in this application.

[0132] To further elucidate the therapeutic potential of drug compounds, pharmacokinetic (PK) data were used to establish key parameters for predicting treatment outcomes, such as the area under the curve (AUC) monitoring systemic drug concentration over time. Therefore, a higher AUC value indicates greater exposure to the drug, which is generally associated with greater therapeutic potential because a higher amount of drug is available to combat mammalian infections. Conversely, a lower AUC value indicates reduced exposure to the drug under investigation, resulting in a reduced amount of antibiotic available to combat bacterial infections. For this purpose, the compounds described in this application were tested in an orally administered rat PK model, using methods similar to those described in the monograph *Current Protocols in Pharmacology*, 2005, 7.1.1-7.1.26, John Wiley & Sons, Inc.

[0133] All compounds were administered to SD rats via intravenous (iv) or oral gavage (rats were randomly assigned to groups of 3). Since the prodrugs were expected to be converted to the parent molecule in vivo, only the parent compound (the compound of Example 5) was tested for all samples. As shown in Table 3, the parent compound of Example 5 exhibited only a low oral bioavailability of 15%. This low bioavailability, along with low exposure (AUC) and C... max This makes it unsuitable for development as an oral drug. Surprisingly, pharmacokinetic data for the compounds of this invention showed significant improvements in systemic exposure (AUC) and Cmax at the same dose of 5 mg / kg. The AUC of Examples 1, 2, 3, 4, 6, 7, and 8 were all significantly higher than that of Example 5, despite the higher molecular weight of these prodrugs compared to Example 5. For example, the compound of Example 2 showed significantly higher AUC and Cmax. max The values ​​were 2906 ng*h / mL and 870 ng / mL, respectively. This unexpected result indicates that the exposure level and C... max The efficacy was significantly increased by 3.4-fold and 3-fold, respectively, consistent with the efficacy improvements described in Table 2. Since prodrugs typically have larger molecular weights due to the introduction of the prodrug substructure, the AUC per mole was obtained by dose- and molecular weight (MW) correction to compare the efficacy between prodrugs. Importantly, the compound of Example 2 also showed a significantly higher AUC per mole compared to the compound of Example 4 previously described in US2013 / 0165411.

[0134] Table 3 shows the pharmacokinetic studies of selected examples in rats.

[0135]

[0136]

[0137] AUC per mole is corrected for by dose and molecular weight.

[0138] Furthermore, in a lung distribution study conducted in Balb / C mice (three mice at each time point), the lung exposure of Example 2 was significantly higher than the plasma exposure (assessed by the area under the lung / plasma concentration-time curve (AUC)). As shown in Table 4, the compounds of Examples 5 and 2 were administered intravenously and orally at 10 mg / kg, respectively. In the analysis of Example 2, the concentrations of the parent compound (Example 5) and the prodrug (Example 2) in plasma and lung were determined. The prodrug (Example 2) rapidly converted to Example 5, becoming almost undetectable in plasma. The oral bioavailability of Example 5 generated by Example 2 in mice was 83.95% compared to the AUC of Example 5 administered intravenously. Despite the rapid conversion of the prodrug, surprisingly, more Example 5 was detected in the lung, with a lung / plasma AUC ratio of 5.24, almost 2.2 times that of Example 5 administered intravenously. The higher accumulation of the drug in the lung is particularly useful for treating pneumonia, which is also consistent with the superior efficacy of Example 2 in a mouse model of Pseudomonas aeruginosa lung infection (Table 2).

[0139] Table 4 shows the lung and plasma distribution of the drug in Example 5 and its prodrug in Example 2 in mice.

[0140]

[0141] The significant increase in in vivo exposure (AUC) in plasma and lungs after oral administration of the compound of Example 2 was entirely unexpected and quite surprising. Other related compounds provided in this application have also shown surprising increases in in vivo exposure. Therefore, pharmacokinetic data from an orally administered rat model of the compound of Example 2 showed that, compared to the parent compound of Example 5, the in vivo exposure and CUC were significantly improved. max Significantly improved.

[0142] The complete and representative data above reveal the surprisingly superior therapeutic potential of the compounds described in this application, offering beneficial and unexpected advantages in terms of potency, efficacy, and exposure. The significant and surprising improvements in three distinctly different key parameters of the antimicrobial compounds provided in this application offer significant benefits for treatment in humans or mammals, including but not limited to convenient long-term oral administration, reduced effective drug dose, and reduced potential side effects.

[0143] Dosage and drug formulation

[0144] Generally, the compounds described in this application are administered in therapeutically effective amounts via any acceptable mode of administration used in formulations for similar purposes. For example, the compounds described in this application may be administered orally, parenterally, transdermally, topically, rectally, or intranasally. The actual amount of the compound described in this application (i.e., the active ingredient) will depend on many factors, such as the severity of the disease to be treated (i.e., infection), the age and relative health of the subject, the potency of the compound used, the route and form of administration, and other factors, all of which are within the scope of the attending clinician.

[0145] Data obtained from cell culture assays and animal studies can be used to formulate a range of dosages for human use. The preferred dosages for these compounds include those with low or no toxicity. 50 The dosage can vary within this range, depending on the dosage form and route of administration used. For any compound used in the methods described in this application, the therapeutically effective dose can be initially estimated from cell culture assays. Doses can be formulated in animal models to achieve a range of circulating plasma concentrations that includes the IC50 values ​​determined in cell culture. 50 (That is, the concentration of the test compound that achieves maximum inhibition of half of the symptoms). Such information can be used to more accurately determine the useful dose for humans. Plasma levels can be measured, for example, by high-performance liquid chromatography.

[0146] When used as a pharmaceutical, the compounds described in this application are typically administered in the form of pharmaceutical compositions. These compounds can be administered via a variety of routes, including oral, parenteral, transdermal, topical, rectal, and intranasal administration.

[0147] These compounds are effective as both injectable and oral compositions. Such compositions can be prepared in a manner well known in the pharmaceutical field and contain at least one active compound.

[0148] This application also describes pharmaceutical compositions containing one or more of the compounds described herein and a pharmaceutically acceptable carrier as the active ingredient. In preparing the compositions described herein, the active ingredient is typically mixed with an excipient, which is then diluted or encapsulated within such a carrier, which may be in the form of a capsule, sachet, paper, or other container. When the excipient is used as a diluent, it can be a solid, semi-solid, or liquid material that acts as a medium, carrier, or conduit for the active ingredient. Therefore, the compositions can be in the form of tablets, pills, powders, lozenges, sachets, capsules, elixirs, suspensions, emulsions, solutions, syrups, aerosols (solid or in a liquid medium), ointments containing, for example, up to 10% by weight of the active compound, soft and hard gelatin capsules, suppositories, sterile injectable solutions, and sterile packaged powders.

[0149] When preparing formulations, it may be necessary to grind the active compound to provide a suitable particle size before combining it with other ingredients. If the active compound is substantially insoluble, it is typically ground to a particle size of less than 200 mesh. If the active compound is substantially water-soluble, the particle size is typically adjusted by grinding to provide a substantially uniform distribution in the formulation, for example, about 40 mesh.

[0150] Examples of suitable excipients include lactose, glucose, sucrose, sorbitol, mannitol, starch, gum arabic, calcium phosphate, alginate, astragalus gum, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, sterile water, syrup, and methylcellulose. Formulations may also include: lubricants such as talc, magnesium stearate, and mineral oil; wetting agents; emulsifiers and suspending agents; preservatives such as methyl and propyl hydroxybenzoates; sweeteners; and flavoring agents. The compositions described in this application can be prepared using procedures known in the art to provide a rapid, sustained, or delayed release of the active ingredient after administration to a patient.

[0151] The amount of active ingredient (i.e., the compound described in this application) in a pharmaceutical composition and its unit dosage form can vary widely or be adjusted depending on the specific application, the potency of the specific compound, and the required concentration.

[0152] The composition is preferably formulated in unit dosage forms, each dose containing about 5 to about 100 mg, more typically about 10 to about 30 mg of the active ingredient. The term "unit dosage form" refers to a physically discrete unit suitable as a unit dose for human subjects and other mammals, each unit containing a predetermined amount of the active substance, calculated together with suitable pharmaceutical excipients to produce the desired therapeutic effect. Preferably, the compound described in this application comprises no more than about 20% by weight of the pharmaceutical composition, more preferably no more than about 15% by weight, with the remainder being a pharmaceutically inert carrier.

[0153] The active compound is effective over a wide dose range and is typically administered at pharmaceutically or therapeutically effective amounts. However, it should be understood that the actual amount of compound administered will be determined by the physician based on relevant circumstances, including but not limited to the condition to be treated, the severity of the bacterial infection being treated, the route of administration chosen, the actual compound administered, the individual patient's age, weight and response, and the severity of the patient's symptoms.

[0154] In therapeutic use for treating or combating bacterial infections in warm-blooded animals, the compound or pharmaceutical composition thereof may be administered orally, topically, transdermally, and / or parenterally in a dose to obtain and maintain a concentration, i.e., a dose, or the blood level of the active ingredient in the animal being treated, which would be antibacterially effective. Typically, such an antibacterial or therapeutically effective dose (i.e., effective dose) of the active ingredient will be in the range of about 0.1 mg / kg to about 100 mg / kg body weight / day, more preferably about 1.0 mg / kg to about 50 mg / kg body weight / day.

[0155] To prepare solid compositions such as tablets, the main active ingredient is mixed with a pharmaceutical excipient to form a solid preform composition containing a homogeneous mixture of the compounds described in this application. When these preform compositions are referred to as homogeneous, it means that the active ingredient is uniformly dispersed throughout the composition, allowing the composition to be readily subdivided into equivalent unit dose forms, such as tablets, pills, and capsules. The solid preforms are then subdivided into unit dose forms of the type described above, containing, for example, 0.1 to about 500 mg of the active ingredient described in this application.

[0156] The tablets or pills described in this application may be coated or otherwise compounded to provide a dosage form with the advantage of prolonged action. For example, a tablet or pill may include an inner dose component and an outer dose component, the latter being an encapsulated form on top of the former. These two components can be separated by an enteric coating, which resists disintegration in the stomach and allows the inner component to enter the duodenum intact or with delayed release. A variety of materials can be used for such an enteric coating or coating, including various polymeric acids and mixtures of polymeric acids with materials such as shellac, cetyl alcohol, and cellulose acetate.

[0157] The compositions described in this application, when incorporated into liquid forms for oral or injectable administration, include aqueous solutions, appropriately flavored syrups, aqueous or oil suspensions, emulsions flavored with edible oils such as corn oil, cottonseed oil, sesame oil, coconut oil, or peanut oil, as well as elixirs and similar drug carriers.

[0158] Compositions for inhalation or inhalation include pharmaceutically acceptable solutions and suspensions, aqueous or organic solvents or mixtures thereof, and powders. Liquid or solid compositions may contain suitable pharmaceutically acceptable excipients as described above. Preferably, the compositions are administered via oral or nasal inhalation routes to achieve local or systemic effects. Compositions in preferred pharmaceutically acceptable solvents may be nebulized using an inert gas. The nebulized solution may be inhaled directly from a nebulizer, or the nebulizer may be connected to a mask tent or intermittent positive pressure respirator. Solution, suspension, or powder compositions may be administered from a device for delivering the formulation in a suitable manner, preferably orally or nasally.

[0159] Another preferred formulation used in the method described in this application employs a transdermal drug delivery device (“patch”). Such transdermal patches can be used to deliver the compound described in this application in controlled amounts via continuous or discontinuous infusion. The construction and use of transdermal patches for delivering pharmaceutical formulations are well known in the art. See, for example, U.S. Patent 5,023,252, issued June 11, 1991, which is incorporated herein by reference. Such patches can be constructed for continuous, pulsatile, or on-demand delivery of pharmaceutical formulations.

[0160] Typically, it is desirable or necessary to introduce a pharmaceutical composition directly or indirectly into the brain. Direct techniques generally involve placing a drug delivery catheter in the host's ventricular system to bypass the blood-brain barrier. An implantable delivery system for delivering biological agents to specific anatomical regions of the body is described in U.S. Patent 5,011,472, which is incorporated herein by reference.

[0161] Preferred indirect techniques typically involve formulating compositions that provide drug latency by converting hydrophilic drugs into lipid-soluble drugs. Latency is usually achieved by blocking hydroxyl, carbonyl, sulfate, and primary amine groups present on the drug, making the drug more soluble in lipids and easier to transport across the blood-brain barrier. Alternatively, delivery of hydrophilic drugs can be enhanced by intra-arterial infusion of a hypertonic solution that can instantaneously open the blood-brain barrier.

[0162] Other suitable formulations for use with the compounds described in this application can be found in Remington's Pharmaceutical Sciences, Mace Publishing Company, Philadelphia, PA, 17th edition (1985).

[0163] As described above, the compounds described in this application are applicable to the various drug delivery systems described above. Furthermore, to improve the in vivo serum half-life of the administered compound, the compound can be encapsulated, introduced into the lumen of a liposome, prepared as a colloid, or other conventional techniques that provide extended serum half-life of the compound can be employed. Various methods can be used to prepare liposomes, as described, for example, in U.S. Patents 4,235,871, 4,501,728, and 4,837,028 to Szoka et al., each of which is incorporated herein by reference.

[0164] As described above, the compounds administered to patients are in the form of the aforementioned pharmaceutical compositions. These compositions can be sterilized using conventional sterilization techniques or can be aseptically filtered. The resulting aqueous solutions can be used as is or lyophilized, with the lyophilized formulation bound to a sterile aqueous carrier prior to administration. The pH of the compound formulation is typically 3 to 11, more preferably 5 to 9, and most preferably 7 to 8. It should be understood that the use of certain of the aforementioned excipients, carriers, or stabilizers may result in the formation of drug salts.

[0165] The disclosure of every patent, patent application, and publication (e.g., journals, articles, and / or textbooks) cited in this application is incorporated herein by reference in its entirety. Furthermore, as used in this application and the appended claims, singular articles such as “a,” “an,” and “one” are intended to refer to either the singular or the plural. Although embodiments are described in conjunction with preferred aspects in this application, changes, substitutions of equivalents, and other types of alterations to the embodiments described herein can be made by those skilled in the art upon reading the foregoing specification. Each aspect described above may also include or incorporate such variations or aspects disclosed with respect to any or all other aspects. The description of this application is not limited to the specific aspects described herein, and is intended as a single illustration of the various aspects provided herein. Many modifications and variations described herein can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods within the scope of this specification, in addition to those listed in this application, will be apparent to those skilled in the art from the foregoing description. It should be understood that this specification is not limited to specific methods, reagents, process conditions, materials, etc., although these methods, reagents, and materials can certainly vary. It should also be understood that the terminology used in this application is for describing specific aspects only and is not intended to be limiting. Therefore, this specification is to be considered exemplary.

Claims

1. A compound having the following structure: ###0001### or a pharmaceutically acceptable salt thereof. 。 2. The compound of claim 1, or a pharmaceutically acceptable salt thereof, wherein, The pharmaceutically acceptable salt is a hydrochloride salt.

3. Use of a compound of claim 1 or 2, or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for the treatment of a microbial infection in a mammal, comprising administering to a mammal in need of treatment a therapeutically effective amount of a compound of claim 1 or 2, or a pharmaceutically acceptable salt thereof.

4. Use according to claim 3, characterized in that, The compound, or a pharmaceutically acceptable salt thereof, is administered orally or topically to the mammal in the form of a pharmaceutical composition.

5. Use according to claim 4, characterized in that, The topical administration is transdermal, rectal or intranasal administration.

6. Use according to claim 4, characterized in that, The compound, or a pharmaceutically acceptable salt thereof, is administered orally to the mammal in the form of a pharmaceutical composition.

7. Use according to claim 3, characterized in that, The microbial infection is caused by a Gram-negative bacteria selected from the group consisting of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli and Klebsiella pneumoniae.

8. Use according to claim 3, characterized in that, The infection is a skin, soft tissue, respiratory tract, blood, intra-abdominal, urinary or ocular infection.

9. A pharmaceutical composition, characterized by, A therapeutically effective amount of a compound according to claim 1 or 2, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

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