Methods of treatment, uses and compositions of rifabutin

Abstract

To provide formulations comprising rifabutin, methods of making the same, and methods of using the formulations in the treatment of bacterial infections.SOLUTION: A rifabutin formulation formed from rifabutin powder in the presence of an acid, water and a solvent suitable for facilitating the dissolution of rifabutin. A method of preparing a formulation of rifabutin, the method comprising: preparing a solution comprising a solvent, water and an acid; and dissolving the rifabutin in the solution by adding the solution to a rifabutin powder. A method of preparing a formulation of rifabutin comprising: preparing a solution comprising water and an acid; and adding the solution to a solution of rifabutin in a solvent to produce an aqueous rifabutin formulation. A method of treating a bacterial infection in a subject comprising administering a therapeutically effective amount of rifabutin in an injectable formulation or by inhalation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of and priority to U.S. Provisional Patent Application Nos. 62 / 902,019, filed September 18, 2019, 62 / 899,257, filed September 12, 2019, 62 / 941,160, filed November 27, 2019, and 62 / 977,659, filed February 17, 2020, the contents of each of which are incorporated herein by reference in their entirety.

[0002] FIELD OF THE INVENTION The present invention relates generally to formulations containing the antibiotic rifabutin, methods of making such formulations, and methods of using such formulations in the treatment of bacterial infections. [Background technology]

[0003] background Millions of people die from bacterial infections each year, and the number is increasing due to the spread of antibiotic-resistant bacterial strains. For example, according to official estimates, the annual number of deaths due to antibiotic-resistant bacterial infections exceeds 100,000 in the United States, the European Union, and India alone, although some experts believe that official records are a significant underestimate because the full impact of antibiotic resistance is still unknown. Unfortunately, the pipeline for new antibiotic development in recent decades has been sprawling and slow, and many existing antibiotics suffer from problems that limit their effectiveness.

[0004] One existing antibiotic that has failed to reach its full therapeutic potential is rifabutin (also known as LM427 and Mycobutin®). While rifabutin is active against a broad spectrum of bacteria, its poor water solubility makes it difficult to deliver the antibiotic at effective doses to treat infections other than those reported on the Mycobutin® label and to effectively prevent the development of resistance. Based on studies of rifabutin and related antibiotics in the same class, high levels of free rifabutin are believed to be necessary for both bacterial killing and the prevention of resistance development. Consequently, the therapeutic use of rifabutin is hindered by technical problems, and millions of people continue to suffer from bacterial infections due to a lack of adequate treatment options. Summary of the Invention [Means for solving the problem]

[0005] Abstract The present invention provides a pharmaceutical formulation containing high concentrations of rifabutin. A preferred composition of the present invention comprises rifabutin powder formulated in water, a solvent, and an acid. The combination of the present invention allows rifabutin to be dissolved at high concentrations. The formulated solution can be diluted without limit to make the composition suitable for the desired administration route.

[0006] The formulations of the present invention allow for the delivery of effective amounts of rifabutin by routes of administration not possible with previous rifabutin-containing compositions. For example, the formulations of the present invention allow rifabutin to be provided parenterally (including intravenously or by inhalation). Furthermore, the formulations of the present invention obviate the need to lyophilize rifabutin before reconstituting it for administration (a rather costly process).

[0007] In another aspect of the invention, rifabutin is prepared as a powder having a shelf life equivalent to that of the active pharmaceutical ingredient (API) of rifabutin. As described in more detail below, the rifabutin formulations of the invention preferably comprise rifabutin powder dissolved in an organic solvent.

[0008] According to the present invention, highly concentrated rifabutin formulations can be rapidly obtained from any rifabutin API and used as is or further diluted freely with sterile water or a pharmaceutically acceptable solution. The formulations of the present invention are useful for treating various conditions caused by or associated with bacterial infections, including, but not limited to, bacteremia, meningitis, ventilator-associated bacterial pneumonia (VABP), hospital-acquired bacterial pneumonia (HABP), and periprosthetic joint infections (PJI).

[0009] In one aspect, the present invention provides a parenteral formulation of rifabutin prepared by preparing a solution in the presence of an acid suitable for promoting dissolution of rifabutin, the solution preferably comprising a solvent and water in a ratio suitable for the intended use of the formulation.

[0010] The formulations of the present invention are suitable for any parenteral administration route. They are suitable for parenteral administration, intravenous administration, intraarterial administration, or pulmonary delivery. They are also suitable for administration by inhalation or injection.

[0011] The formulations of the present invention are reconstituted solutions that may need to be diluted before parenteral administration. The formulations of the present invention contain a solvent and water in a predetermined ratio. This ratio may be a v / v ratio. The solution may contain the solvent and distilled water in a ratio of about 9:1 to about 1:9, about 9:1 to about 1:4, about 9:1 to about 1:2, about 9:1 to about 1:1, about 4:1 to about 1:9, about 4:1 to about 1:4, about 4:1 to about 1:2, about 4:1 to about 1:1, about 2:1 to about 1:9, about 2:1 to about 1:4, about 2:1 to about 1:2, or about 2:1 to about 1:1. The solution may contain the solvent and distilled water in a ratio of about 9:1, about 4:1, about 2:1, about 1:1, about 1:2, about 1:4, or about 1:9.

[0012] The solvent can be polyoxyethylene sorbitan monooleate (Tween® 80), polyoxyethylene sorbitan monolaurate (Tween® 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerin, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (transcutol HP), or dimethyl isosorbide (DMI).

[0013] The acid can be hydrochloric acid, methanesulfonic acid, phosphoric acid, L-tartaric acid, D-glucuronic acid, L-malic acid, D-gluconic acid, L-lactic acid, acetic acid, L-aspartic acid.

[0014] The reconstituted solution of the present invention preferably contains about 250 mg / ml (1:1 solvent / water) or about 166.7 mg / ml (1:2 solvent / water), although the concentration of the reconstituted solution can be as high as about 300 mg / ml. In certain embodiments, a more dilute solution is required, which can be achieved by adding more water to the solvent. For example, rifabutin in a 1:4 solvent / water ratio results in a solution of about 50 mg / ml. However, such dilution requires additional time to dissolve the rifabutin powder. Alternatively, rifabutin can be dissolved in a solvent, and then the reconstituted solution is obtained without further modification. Generally, for IV solutions, the requirement is to keep the rifabutin / solvent ratio as low as possible. Suitable ranges are provided herein.

[0015] The formulations of the present invention are effective for the treatment of bacterial infections, which may include one or more of the following: A. baumannii, C. jejuni, C. trachomatis, H. ducreyi, H. influenzae, H. pylori, M. chelonae, M. kansasii, M. leprae, M. tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, N. gonorrhoeae, N. meningitidis, staphylococci, streptococci (e.g., group A streptococci), and T. gondii, or any other pathogen susceptible to rifabutin.

[0016] The amount of acid relative to rifabutin can be between 1 and 3 molar equivalents, or between 1 and 2 molar equivalents. The amount of acid relative to rifabutin can be 1 molar equivalent.

[0017] The w / v ratio of rifabutin to solvent can be about 4:1 to about 1:4, about 2:1 to about 1:3, or about 1:1 to about 1:2. The w / v ratio of rifabutin to solvent can be about 4:1, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, or about 1:4.

[0018] In another aspect, the present invention provides a method for preparing a parenteral formulation of rifabutin by preparing a solution comprising a solvent and distilled water, adding an acid to the solution, introducing the solution into rifabutin powder, and dissolving the rifabutin in the solution.

[0019] In another aspect, the present invention provides a method for preparing a parenteral formulation of rifabutin by preparing a solution of rifabutin in a solvent and a solution of an acid in water, and then mixing the two solutions.

[0020] The formulation may have any of the properties described above for formulations. The acid and solvent may be any of those described above. The water and solvent may be combined in any ratio described above.

[0021] The methods of the present invention include diluting the formulated rifabutin solution into a pharmaceutically acceptable diluent (e.g., including, but not limited to, sterile water, sodium chloride (i.e., saline) solution, dextrose in water, lactated Ringer's solution) to provide a composition appropriate for the desired route of administration.

[0022] The dissolving of rifabutin may include swirling, stirring, or agitating the solution. The dissolving of rifabutin may be carried out for a predetermined period of time. The dissolving of rifabutin may be carried out for about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 30 minutes, about 45 minutes, or about 60 minutes.

[0023] The rifabutin may be provided as a solid powder.

[0024] The rifabutin may be provided as a solution in a solvent.

[0025] In another aspect, the present invention provides a method of treating a bacterial infection in a subject by administering a therapeutically effective amount of a parenteral formulation of rifabutin.

[0026] The bacterial infection may include one or more of A. baumannii, C. jejuni, C. trachomatis, H. ducreyi, H. influenzae, H. pylori, M. chelonae, M. kansasii, M. leprae, M. tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, N. gonorrhoeae, N. meningitidis, staphylococci, streptococci (e.g., group A streptococci), and T. gondii or any other pathogen susceptible to rifabutin.

[0027] The formulation may have any of the properties described above for formulations.

[0028] The formulations may be provided parenterally, intravenously, or by inhalation.

[0029] An aspect of the present disclosure provides the use of rifabutin, an acid, a solvent, and a diluent for the preparation of a medicament for treating a bacterial infection.

[0030] In certain embodiments, the diluent is water.

[0031] In certain embodiments, the w / v ratio of rifabutin to solvent can be about 4:1, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, or about 1:4.

[0032] In certain embodiments, the w / v ratio of rifabutin to solvent is about 1:2.

[0033] In certain embodiments, the solvent is polyoxyethylene sorbitan monooleate (Tween® 80), polyoxyethylene sorbitan monolaurate (Tween® 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerin, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (dichloroisothiazolinone), or methylpropional (methylpropional). HP), or dimethyl isosorbide (DMI).

[0034] In certain embodiments, the solvent is DMI or transcutol HP.

[0035] In certain embodiments, the solvent and water are present in a ratio of about 9:1 to about 1:9, about 9:1 to about 1:4, about 9:1 to about 1:2, about 9:1 to about 1:1, about 4:1 to about 1:9, about 4:1 to about 1:4, about 4:1 to about 1:2, about 4:1 to about 1:1, about 2:1 to about 1:9, about 2:1 to about 1:4, about 2:1 to about 1:2, or about 2:1 to about 1:1.

[0036] In certain embodiments, the solvent and water are present in a ratio of about 1:1 to about 1:2.

[0037] In certain embodiments, the acid is hydrochloric acid, methanesulfonic acid, phosphoric acid, L-tartaric acid, D-glucuronic acid, L-malic acid, D-gluconic acid, L-lactic acid, acetic acid, or L-aspartic acid.

[0038] In certain embodiments, the acid may be D-glucoronic acid.

[0039] In certain embodiments, the acid may be acetic acid.

[0040] In certain embodiments, the amount of acid relative to rifabutin is between 1 and 3 molar equivalents or between 1 and 2 molar equivalents.

[0041] In certain embodiments, the amount of acid to rifabutin may be 1 molar equivalent.

[0042] In certain embodiments, the rifabutin to acid molar ratio is about 1:1.

[0043] In certain embodiments, the w / v ratio of rifabutin to solvent can be from about 4:1 to about 1:4, from about 2:1 to about 1:3, or from about 1:1 to about 1:2.

[0044] In certain embodiments, the bacterial infection is A. baumannii, C. jejuni, C. trachomatis, H. ducreyi, H. influenzae, H. pylori, M. chelonae, M. kansasii, M. leprae, M. tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, N. gonorrhoeae, N. meningitidis, staphylococci, streptococci (e.g., group A streptococci), or T. gondii.

[0045] In another aspect, the present invention provides a formulation comprising rifabutin, an acid, water, and a suitable solvent to promote dissolution of rifabutin.

[0046] The formulations may contain any ratio of rifabutin to solvent, any ratio of solvent to water, or any ratio of rifabutin to acid described above.

[0047] The formulation may include any of the solvents or any of the acids described above.

[0048] The formulations may contain any concentration of rifabutin (e.g., about 250 mg / ml, about 200 mg / ml, about 150 mg / ml, about 100 mg / ml, about 50 mg / ml, about 20 mg / ml, about 10 mg / ml, about 5 mg / ml, about 2.5 mg / ml, about 1 mg / ml, at least about 250 mg / ml, at least about 200 mg / ml, at least about 150 mg / ml, at least about 100 mg / ml, at least about 50 mg / ml, at least about 20 mg / ml, at least about 10 mg / ml, at least about 5 mg / ml, at least about 2.5 mg / ml, at least about 1 mg / ml, at least about 1 mg / ml about 250 mg / ml, about 2.5 mg / ml to about 250 mg / ml, about 5 mg / ml to about 250 mg / ml, about 10 mg / ml to about 250 mg / ml, about 20 mg / ml to about 250 mg / ml, about 50 mg / ml to about 250 mg / ml, about 100 mg / ml to about 250 mg / ml, about 1 mg / ml to about 200 mg / ml, about 2.5 mg / ml to about 200 mg / ml, about 5 mg / ml to about 200 mg / ml, about 10 mg / ml to about 200 mg / ml, about 20 mg / ml to about 200 mg / ml, about 50 mg / ml to about 200 mg / ml, or about 100 mg / ml to about 200 mg / ml. [Brief explanation of the drawings]

[0049] [Figure 1] FIG. 1 is a schematic diagram of a method for preparing a rifabutin solution for injection or rifabutin for inhalation according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of the analytical method for rifabutin formulations. [Figure 3] FIG. 3 is a graph showing the solubility of rifabutin in formulations. [Figure 4] FIG. 4 is a graph showing the solubility of rifabutin in formulations. DETAILED DESCRIPTION OF THE INVENTION

[0050] Detailed Description Rifabutin and the Challenges of Rifabutin Administration The present invention provides compositions and methods for preparing solutions containing rifabutin suitable for parenteral or inhalation administration. Importantly, the present invention enables intravenous administration of rifabutin at high doses. Intravenous formulations of rifabutin allow for delivery of the compound with much greater efficiency and effectiveness than can be achieved with previous oral rifabutin formulations. In particular, the present invention discloses the use of a water / solvent mixture in the presence of an acid as a pharmaceutically acceptable solution for reconstitution of rifabutin powder to rapidly prepare a stable, highly concentrated reconstituted solution, which can then be diluted, without limitation, with additional water for injection or a pharmaceutically acceptable diluent to make the composition suitable for the desired route of administration.

[0051] The formulations of the present invention address the requirement that high concentrations of rifabutin at the injection site are optimal to achieve suitable pharmacokinetic (PK) parameters (e.g., area under the curve (AUC) and Cmax) required for maximum clinical efficacy and prevention of resistance in the treatment of bacterial infections in which rifabutin is active.

[0052] Rifabutin is a deep reddish-purple powder with the molecular formula C 46 H 62 NO 11 , molecular weight 847.02 and the following structure: [ka] It has.

[0053] Rifabutin has broad-spectrum antimicrobial activity. It is significantly more active than rifampin against MAC, M. tuberculosis, and M. leprae. It is also active against most atypical mycobacteria, including M. kansasii and M. chelonae, although these are relatively resistant. Rifabutin is also active against staphylococci, group A streptococci, N. gonorrhoeae, N. meningitidis, H. influenzae, H. ducreyi, C. jejuni, H. pylori, C. trachomatis, T. gondii, and A. baumannii.

[0054] In healthy adult volunteers, a nominal therapeutic oral dose of 300 mg rifabutin produces a mean Cmax of 0.375 mg / L, achieved approximately 3 hours after oral administration (Rifabutin Product Monograph). The PK of rifabutin is linear with a Cmax ranging from 0.4 to 0.7 mg / L after single administration of 300 mg, 450 mg, and 600 mg PO to healthy volunteers (Rifabutin Product Monograph). In a study in HIV-infected patients receiving the recommended daily dose of rifabutin (300 mg / day), steady-state plasma concentrations were Cmax = 0.59 ± 0.33 mg / L and the AUC was 8.6 ± 8.2 mg*h / L (Hafner et al., 1998). Rifabutin is approximately 90% protein-bound; therefore, free drug concentrations after oral administration are very low. In healthy adult volunteers, at least 53% of an oral dose is absorbed, whereas absolute bioavailability assessed in HIV-positive patients was 20% on day 1 and 12% on day 28 in a multiple-dose study.

[0055] For closely related rifamycin molecules (e.g., rifampin), microbial kill was related to the area under the concentration-time curve to the minimum inhibitory concentration (MIC) ratio (AUC / MIC), whereas suppression of resistance was related to the free peak concentration (Cmax) to MIC ratio (Cmax / MIC) and not to the duration that rifampin concentrations exceeded the MIC. Furthermore, postantibiotic duration of effect was also most closely related to the Cmax / MIC ratio. Gumbo T, Louie A, Deziel MR, Liu W, Parsons LM, Salfmger M, Drusano GL. Concentration-dependent Mycobacterium tuberculosis killing and prevention of resistance by rifampin. Antimicrob Agents Chemother 2007, 51(11):3781-8, the contents of which are incorporated herein by reference. Thus, high plasma and / or high local concentrations of rifabutin are needed to achieve microbial kill and prevent the emergence of resistance in the clinical setting.

[0056] The emergence of resistance to multiple antimicrobial drugs in pathogenic bacteria poses a serious public health threat because fewer or even no effective antimicrobial drugs are available for infections caused by these bacteria. Both gram-positive and gram-negative bacteria are affected by the emergence and rise of antimicrobial resistance.

[0057] Life-threatening infections caused by these pathogens are best treated in hospitals using optimized dosing regimens that often include parenteral and, in some cases, the additional use of nebulized antibiotics.

[0058] In this context, the intravenous (IV) and inhaled (IN) routes of administration offer several advantages over the oral route in terms of achieving a high cure rate: a) With the oral route, a variable fraction reaches the systemic circulation; the remainder of the drug either passes through the gastrointestinal (GI) tract without being absorbed or is subject to the first-pass effect, i.e., metabolic transformation occurring in the liver leads to excretion of drug metabolites via the bile or kidneys. b) By the oral route, Cmax and tmax (the time at which Cmax is achieved) are limited by the rate of absorption of the drug in the GI tract. c) The rate of absorption in humans is highly variable depending on the age of the patient, the presence of concomitant disease in the patient, and the progression of the infectious disease. d) With the IV route, instead, the drug enters the bloodstream directly, the t is immediate, and the C can be controlled by the concentration of drug infused and the time it is infused. The AUC is, of course, the maximum achievable for any other route of administration. e) In the IN route, the drug instead enters the lungs directly, and the Cmax and distribution in the lungs can be controlled by the drug concentration and by the particle size produced by the particular nebulizer.

[0059] Both the IV and IN routes allow rifabutin to achieve high AUC / MIC and Cmax / MIC. This is important for the efficacy of the drug and for preventing the development of drug resistance during the treatment of bacterial infections sensitive to the action of rifabutin. The IV route of administration allows the drug to be appropriately distributed in plasma, and thus allows optimization of these parameters in any compartment suitable for the treatment of infections such as bacteremia, meningitis, periprosthetic joint infections (PJI), and some severe pulmonary infections (e.g., ventilator-associated bacterial infections (VABP) and hospital-acquired bacterial infections (HABP)). Alternatively, the IN route is intended to achieve high local concentrations in the lungs for the treatment of any bacterial pulmonary infections, in all those cases where physicians prioritize achieving very high drug lung concentrations without unnecessarily exposing other body compartments to excessive drug levels. Alternatively, physicians may decide to use rifabutin via the IN route in combination with oral or parenteral antibiotics.

[0060] The present invention includes rifabutin formulations for intravenous (IV) administration. In another embodiment of the invention, rifabutin is administered intravenously (IV) or by inhalation (IN).

[0061] Compositions and formulations containing rifabutin The present invention provides compositions comprising a formulation in which free base rifabutin is dissolved in water / solvent and acid.

[0062] The compositions may be provided as pharmaceutically acceptable salts (e.g., non-toxic acid addition salts), which are salts of amino groups formed with inorganic acids (e.g., including, but not limited to, hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, and perchloric acid) or with organic acids (e.g., including, but not limited to, acetic acid, maleic acid, tartaric acid, citric acid, succinic acid, methanesulfonic acid, glucuronic acid, malic acid, gluconic acid, lactic acid, aspartic acid, or malonic acid).

[0063] In some embodiments, pharmaceutically acceptable salts include, but are not limited to, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecyl sulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, iodine salts, and hydroxybenzoates. Acid salts include chlorate, 2-hydroxyethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, and valerate. Hydrochloric acid, methanesulfonic acid, phosphoric acid, L-tartaric acid, D-glucuronic acid, L-malic acid, D-gluconic acid, L-lactic acid, acetic acid, and L-aspartic acid are preferably used. Acetic acid, L-lactic acid, D-gluconic acid, and D-glucuronic acid are most preferably used.

[0064] The pharmaceutical composition can be administered in dosage forms, formulations, or via suitable delivery devices or implants containing conventional non-toxic pharmaceutically acceptable carriers, solvents, diluents, and adjuvants, by injection, infusion, implant (intravenous, intramuscular, subcutaneous, etc.), or by inhalation. The formulation and preparation of such compositions are well known to those skilled in the art of pharmaceutical formulation.

[0065] The compositions of the present invention for parenteral use can be provided in unit dosage form (e.g., in single-dose ampoules and vials), in vials containing several doses and to which appropriate preservatives (see below) can be added, in pre-filled syringes, or in pre-filled IV bags. The pharmaceutical compositions described herein can be in a form suitable for sterile injection. As shown in Figure 1, to prepare such a composition, a solution of water and acid in a solvent is added to rifabutin in powder form to promote dissolution. Alternatively, such a composition can be prepared by preparing rifabutin in a solvent and mixing it with the aqueous solution containing the acid.

[0066] Thus, the present invention provides a method for preparing an intravenous formulation of rifabutin. The method may include preparing a solution containing a solvent and distilled water. Preferably, the solution is in a 1:1 or 1:2 ratio. The solvent may be any solvent, but is preferably DMI or trascutol HP. An acid may be added to the container. The acid may be suitable for promoting the dissolution of rifabutin. The acid may be any acid, but is preferably acetic acid or D-glucuronic acid. The solution containing the acid may be added to rifabutin powder. Thus, the acid dissolves rifabutin in the aqueous solution.

[0067] The rifabutin solution may be added to a pharmaceutically acceptable diluent, which may be 0.9% saline.

[0068] For example, to prepare a 20 mg / ml solution of rifabutin in 4% DMI, first, a 1:1 solution of dimethyl isosorbide (DMI) in distilled water is prepared. Then, 0.169 ml of glacial acetic acid can be added to 9.831 ml of the 1:1 DMI / water solution to form the reconstitution solvent (RS). Then, 1 ml of RS is added to 250 mg of rifabutin to create a 250 mg / ml solution. This RS-rifabutin solution is stirred or shaken until the rifabutin dissolves, forming a deep, deep red solution. Complete dissolution should occur in approximately 15-20 minutes. The concentrated solution is then diluted with 11.5 ml of water to create a final solution of 20 mg / ml rifabutin in 4% DMI. The pH of the final solution is between 5 and 6.

[0069] In another example of preparing an intravenous solution of 2.5 mg / ml rifabutin in 0.5% DMI / 0.9% sodium chloride solution, first, a 1:1 solution of dimethyl isosorbide in distilled water is prepared. Then, 0.169 ml of glacial acetic acid can be added to 9.831 ml of the above 1:1 DMI / water solution to form the RS. Then, 1 ml of RS is added to 250 mg of rifabutin to create a 250 mg / ml solution. This RS-rifabutin solution is stirred or shaken until the rifabutin is completely dissolved (approximately 15-20 minutes). The concentrated solution is then diluted with 99 ml of 0.9% saline for injection to create a final solution of 2.5 mg / ml rifabutin in 0.5% DMI in 0.9% saline with a pH between 5.0 and 6.0.

[0070] 5mg / ml in 1% transcutol HP / 0.9% sodium chloride solution In another example of preparing an intravenous solution of rifabutin, first, a 1:2 solution of transcutol HP in distilled water is prepared. Then, 0.169 ml of glacial acetic acid can be added to 14.831 ml of the above 1:2 transcutol HP / water solution to form the RS. Then, 1.5 ml of RS is added to 250 mg of rifabutin to create a 166.7 mg / ml solution. This RS-rifabutin solution is stirred or shaken until the rifabutin is completely dissolved (approximately 15-20 minutes). The concentrated solution is then diluted with 48.5 ml of 0.9% saline for injection to create a final solution of 5 mg / ml rifabutin in 1% transcutol HP in 0.9% saline, with a pH between 5.0 and 6.0.

[0071] In another example, an intravenous solution of 40 mg / ml rifabutin in 8% DMI / 0.9% sodium chloride solution is prepared by using a solution of 250 mg rifabutin in 0.5 ml of DMI and adding 0.5 ml of a solution of 114.6 mg / ml D-glucuronic acid in distilled water. After vortexing for 5 minutes, the resulting 250 mg / ml RS-rifabutin solution is diluted with 5.25 ml of 0.9% saline for injection to produce a final solution of 40 mg / ml rifabutin in 8% DMI in 0.9% saline with a pH between 5.0 and 6.0.

[0072] Depending on the patient's needs and clinical condition, administering the composition by IV administration may be more convenient than oral administration because it allows for rapid introduction of the antibiotic into the systemic circulation, provides complete bioavailability, allows for better control of the pharmacokinetic parameters that drive pharmacological efficacy, and avoids stability and absorption issues in the gastrointestinal tract.

[0073] A typical dose of rifabutin is one that can achieve plasma or local levels where rifabutin Cmax is >2 mg / L but <50 mg / L and AUC is 10 mg*h / L <200 mg*hL.

[0074] The rifabutin solution can be further diluted with a pharmaceutically acceptable diluent. For example, a 20 mg / ml IV solution of rifabutin can be further diluted with 0.9% saline to obtain a lower concentration of rifabutin in order to deliver a less concentrated solution to a subject. Filtration can also be required for the IV formulations of rifabutin disclosed herein. If necessary, filtration can be performed on both the concentrated rifabutin solution or the final rifabutin solution.

[0075] The formulations of the present invention may be for any parenteral administration. For example, the compositions may be formulated for injection or infusion. The injection or infusion may be subcutaneous or intravenous. Preferably, the compositions are formulated for intravenous administration. Preferably, the compositions are formulated for intravenous or inhalation administration. Thus, the formulations of the present invention may also contain a pharmaceutically acceptable diluent. The pharmaceutically acceptable diluent may be in a concentration sufficient to deliver a therapeutically effective amount of rifabutin in an IV formulation to a patient suffering from an infectious disease. The pharmaceutically acceptable diluent may be saline or sterile water. Preferably, the diluent is 0.9% saline. The solution may be administered with a therapeutically effective amount of rifabutin to treat a patient suffering from an infectious disease.

[0076] It should be noted that the various formulations of the present invention described herein may be used with any of the methods of the present invention, and therefore the methods are not limited to any one formulation.

[0077] Method for preparing formulations containing rifabutin The present invention provides a method for preparing a formulation of rifabutin.

[0078] Figure 1 is a representative schematic diagram illustrating a method for preparing a rifabutin solution for injection or rifabutin for inhalation according to an embodiment of the present invention. Intravenous rifabutin formulations can be manufactured by a process that includes preparing a sterile, pharmaceutically acceptable solution for reconstitution containing a solvent and distilled water in a 1:1 ratio in the presence of a suitable acid to promote dissolution of rifabutin. Rifabutin can be in a solid form that is soluble in a liquid medium or in a liquid powder form. Rifabutin can be dissolved in an aqueous solution of solvent and distilled water. Rifabutin can be soluble in an aqueous solution of 50% solvent (i.e., 1:1 solvent-distilled water) in the presence of an acid.

[0079] Rifabutin is soluble in aqueous solutions of 33.3% solvent (ie, 1:2 solvent-distilled water) in the presence of acid.

[0080] The formulation may be suitable for any parenteral route of administration. The formulation may be suitable for parenteral, intravenous, or intraarterial administration. The formulation may be suitable for administration by inhalation.

[0081] The formulation may be a reconstituted solution that needs to be diluted prior to parenteral administration.The formulation may be a reconstituted solution suitable for parenteral administration.

[0082] The solution may include mixing the solvent and distilled water in a predetermined ratio. The ratio may be v / v. The solution may contain the solvent and distilled water in a ratio of about 9:1 to about 1:9, about 9:1 to about 1:4, about 9:1 to about 1:2, about 9:1 to about 1:1, about 4:1 to about 1:9, about 4:1 to about 1:4, about 4:1 to about 1:2, about 4:1 to about 1:1, about 2:1 to about 1:9, about 2:1 to about 1:4, about 2:1 to about 1:2, or about 2:1 to about 1:1. The solution may contain the solvent and distilled water in a ratio of about 9:1, about 4:1, about 2:1, about 1:1, about 1:2, about 1:4, or about 1:9.

[0083] The solvent can be polyoxyethylene sorbitan monooleate (Tween® 80), polyoxyethylene sorbitan monolaurate (Tween® 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerin, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (transcutol HP), or dimethyl isosorbide (DMI).

[0084] The acid can be hydrochloric acid, methanesulfonic acid, phosphoric acid, L-tartaric acid, D-glucuronic acid, L-malic acid, D-gluconic acid, L-lactic acid, acetic acid, or L-aspartic acid.

[0085] The formulation may include diluting the rifabutin-containing solution with a diluent. The diluent may be sterile water, sodium chloride (i.e., saline), dextrose water, or lactated Ringer's solution. The sodium chloride solution may be a 0.9% sodium chloride solution. The dextrose solution may be a 5% dextrose solution or a 10% dextrose solution.

[0086] The resulting solution may require further dilution in a pharmaceutically acceptable solvent, such as, but not limited to, sterile water, mannitol (e.g., 3-5% mannitol, 3% mannitol, 4% mannitol, 4.3% mannitol, and 5% mannitol), phosphate, acetate, additional tartrate, saline (e.g., normal saline (0.9%), half normal saline (0.45%), 0.5% normal saline, etc.). For intravenous formulations, normal saline (0.9%) is the preferred diluent or carrier.

[0087] Rifabutin can be reconstituted in a solution containing an amount of acid comprised between 1 and 3 molar equivalents in a mixture of solvent and water in a ratio of about 9:1 to about 1:9 v / v. The solvent ratio (w / v) can be 4:1 to 1:4. The dissolution time to obtain the formulation can be less than 60 minutes. In particular, the amount of acid can be 1 molar equivalent, the acid can be acetic acid or D-glucuronic acid, the solvent can be DMI or transcutol HP mixed with water at a v / v ratio of 1:1 or 1:2, the rifabutin to solvent w / v ratio can be 1:2, and the dissolution time can be less than 20 minutes.

[0088] The formulation (i.e., the reconstituted rifabutin solution) may be used as is or may be prepared by diluting it into a predetermined volume of diluent. The volume of diluent may be expressed relative to the volume of the reconstituted solution. The volume of diluent may be about 1.0 to about 2.0 volumes, about 1.25 to about 2.25 volumes, about 1.5 to about 2.5 volumes, about 1.75 to about 2.75 volumes, about 2.0 to about 3.0 volumes, about 1.80 to about 2.10 volumes, about 1.90 to about 2.05 volumes, or about 1.95 to about 2.0 volumes of the reconstituted rifabutin solution. The reconstituted rifabutin solution can be added to about 20.5 to about 30 volumes, about 21 to about 29 volumes, about 22 to about 28 volumes, about 23 to about 27 volumes, about 23 to about 26 volumes, about 23 to about 25 volumes, about 23 to about 24 volumes, about 22.5 to about 23.5 volumes, or about 23.0 to about 23.5 volumes of 0.9% saline for injection. Thus, 1 volume of diluent will yield a final solution of about 125 mg / ml, 4 volumes will yield a final solution of about 50 mg / ml, 9 volumes will yield a final solution of about 25 mg / ml, 24 volumes will yield a final solution of about 10 mg / ml, and 99 volumes will yield a final solution of about 2.5 mg / ml. Those skilled in the art will understand how to obtain a solution having any desired final concentration.

[0089] The formulation may contain any suitable concentration of rifabutin, such as those described above.

[0090] The formulations can contain any concentration of DMI, such as that derived from the diluents described above.

[0091] The formulations may contain transcutol HP in any concentration (eg, derived from the diluents described above).

[0092] The amount of acid relative to rifabutin can be between 1 and 3 molar equivalents, or between 1 and 2 molar equivalents. The amount of acid relative to rifabutin can be 1 molar equivalent.

[0093] The w / v ratio of rifabutin to solvent can be about 4:1 to about 1:4, about 2:1 to about 1:3, or about 1:1 to about 1:2. The w / v ratio of rifabutin to solvent can be about 4:1, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, or about 1:4.

[0094] The method may include dissolving rifabutin by swirling, stirring, or agitating the solution. The dissolving may be carried out for a predetermined period of time. The dissolving may be carried out for about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 30 minutes, about 45 minutes, or about 60 minutes.

[0095] Methods for Treating Bacterial Infections The present invention provides a method for treating a bacterial infection, comprising administering a liquid formulation of rifabutin to a subject with a bacterial infection. The liquid formulation may contain rifabutin, a solvent, and an acid.

[0096] The formulations may be provided by intravenous, intraarterial, or pulmonary administration. The formulations may be provided by inhalation or by injection.

[0097] The liquid formulation can be a solution of rifabutin and diluent to be administered intravenously to a subject with bacterial infection.The formulation for IV administration can include a pharmaceutically acceptable solvent.The method can include administering any IV formulation of rifabutin described herein to a subject suffering from bacterial infection.

[0098] An IV formulation containing rifabutin can be administered together with another antibiotic or therapeutic agent. Sequential or alternating administration can include providing an IV formulation containing rifabutin exclusively for a certain period of time and providing another therapeutic agent exclusively for a certain period of time. Sequential administration can include an overlapping period in which both an IV formulation containing rifabutin and a formulation containing another therapeutic agent are provided to the subject. The exclusive period and the overlapping period can independently be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 2 months, 3 months, 4 months, 5 months, 6 months, 8 months, 10 months, 12 months, 18 months, or 24 months. Alternatively, the pharmaceutical formulations of the present invention, or soluble components within the formulations, can contain rifabutin and another therapeutic agent.

[0099] Without wishing to be bound by theory, any formulation of the present invention may be used in any of the methods of the present invention.

[0100] In another aspect of the present invention, a method includes treating a bacterial infection in a subject. The method may include administering a therapeutically effective amount of a formulation containing rifabutin or a salt thereof. The rifabutin formulation may be formulated for intravenous administration. The intravenous formulation is produced by a process including preparing a solution of a solvent and distilled water in a 1:1 ratio in the presence of an acid suitable for promoting dissolution of the rifabutin. Preferably, the solvent is DMI. Preferably, the solvent is transcutol HP. Preferably, the intravenous formulation is approximately 2.5 mg / ml rifabutin in a 0.5% DMI and 0.9% sodium chloride solution.

[0101] In another embodiment, the method may include providing a combination therapy of an IV formulation of rifabutin or its salt and another therapeutic agent to a subject suffering from a bacterial infection. The IV formulation may include a pharmaceutically acceptable solvent. The therapeutic agent may be in a formulation for IV administration.

[0102] An IV formulation containing rifabutin and a formulation containing another therapeutic agent can be provided or administered simultaneously, sequentially in any order, or in an alternating manner. Sequential administration or alternating administration can include providing an IV formulation containing rifabutin exclusively for a certain period of time and providing a formulation containing another therapeutic agent exclusively for a certain period of time. Sequential administration can include an overlapping period during which the subject receives both an IV formulation containing rifabutin and a formulation containing another therapeutic agent. The exclusive period and the overlapping period can independently be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 2 months, 3 months, 4 months, 5 months, 6 months, 8 months, 10 months, 12 months, 18 months, or 24 months.

[0103] In another embodiment, rifabutin is filled into glass vials and sterilized using one of the procedures used for terminal sterilization, which are well known to those skilled in the art and can be performed using gamma irradiation or heat sterilization.

[0104] A 50:50 sterile solution of water for injection and a solvent containing approximately one molar equivalent of acid is then added to the sterile rifabutin to form a concentrated reconstituted solution.

[0105] In another embodiment, the reconstituted rifabutin formulation is sterile filtered.

[0106] In another embodiment, the diluted rifabutin formulation is sterile filtered. [Example]

[0107] Example 1 Preliminary evaluation of solubility in solvent: To determine whether a pharmaceutically acceptable solvent can dissolve rifabutin powder and at what concentration, an appropriate volume of solvent sufficient to achieve a maximum target solubility of 300 mg / ml was added to a small amount of rifabutin powder. After stirring at room temperature for 24 hours, the sample was centrifuged and the supernatant was analyzed by HPLC. The chromatographic peak area of ​​rifabutin was compared to the titration curve. The results of this preliminary screening are reported in Table 1.

[0108] [Table 1]

[0109] A "thermodynamic" solubility screen showed dimethyl isosorbide (DMI) as the best solvent. While interesting, the 24-hour solubility data is irrelevant to the antibiotic powder reconstitution process, because the reconstitution solvent must be able to dissolve the antibiotic within minutes—a practical time for an operator to prepare rifabutin for injection or inhalation.

[0110] Dissolution of rifabutin in DMI at concentrations of ≥ 250 mg / ml was possible but proved to take longer than reasonably acceptable. Furthermore, dilution of the DMI rifabutin solution with a pharmaceutically acceptable solution (e.g., saline) was not possible because the DMI-rifabutin solution separated from the aqueous solution.

[0111] Unexpectedly, the addition of acid to the DMI / water solution allowed for rapid dissolution of the rifabutin powder, and the highly concentrated, reconstituted rifabutin solution could be freely diluted with water or 0.9% saline without any rifabutin precipitation.

[0112] Example 2 Small-scale solubility screen of solvents and acids: Amounts of rifabutin powder consisting of between 100 and 200 mg were weighed into 1.8 ml glass vials. Exemplary solutions for reconstitution were prepared by mixing water containing various solvents and various acids in the amounts specified in Table 2. The solutions were stirred for 15 minutes at room temperature using a magnetic stir bar and briefly vortexed. The samples were filtered using a centrifugal filter (0.2 μm PTFE filter), and the concentrations of the reconstituted solutions were determined by HPLC analysis. Rifabutin chromatographic peak areas were compared to the titration curve. The results are reported in Table 2.

[0113] [Table 2-1] [Table 2-2]

[0114] [Table 3]

[0115] [Table 4-1] [Table 4-2]

[0116] Example 3: Large-scale evaluation of rifabutin reconstitution and further dilution with 0.9% saline: 1.50 g (1.77 mmol) of rifabutin powder was weighed into a 40 mL glass vial. An equimolar amount of acid (1.77 mmol) dissolved in 6 mL of dimethyl isosorbide / water 50 / 50 (v / v) was added. The solution was vortexed for 30 seconds, stirred vigorously using a magnetic stir bar at room temperature for 15 minutes, and vortexed again for 30 seconds.

[0117] The samples were filtered using a syringe and filter (0.2 μm PTFE filter), and the concentration of the reconstituted rifabutin solution was determined by HPLC analysis. Aliquots (1 mL) of the undiluted solution were stored at room temperature and 5° C. for 24 hours.

[0118] Figure 2 is a schematic diagram illustrating the analytical method for rifabutin formulations. Aliquots (500 μL) of the filtrate were diluted 10-fold and 100-fold in 0.9% saline. These dilutions were prepared in triplicate. The diluted samples were visually inspected for immediate precipitation and filtered after 15 minutes. The concentration of API was determined by HPLC analysis, and the pH was recorded. The diluted samples were stored at room temperature for 24 hours.

[0119] After a storage period of 24 hours, the diluted and undiluted samples were re-analyzed by HPLC analysis for determination of API concentration and the pH was recorded.

[0120] The experimental details, results and recorded pH values ​​of the solubility tests of the undiluted samples are shown in Tables 5, 6 and 7 and graphically in Figures 3 and 4.

[0121] [Table 5]

[0122] Figure 3 is a graph showing rifabutin solubility in formulations. Undiluted samples were analyzed on a larger scale at t0 (blue bars), after 24 hours at room temperature (red bars), and after 24 hours at 5°C (green bars).

[0123] [Table 6]

[0124] The osmolality of these solutions was 632, 644, 622 and 645 mOsm / kg for solutions made from acetic acid, L-lactic acid, D-gluconic acid and D-glucuronic acid, respectively.

[0125] [Table 7]

[0126] The osmolality of these solutions was 323, 319, 316 and 318 mOsm / kg for solutions made from acetic acid, L-lactic acid, D-gluconic acid and D-glucuronic acid, respectively.

[0127] Figure 4 is a graph showing rifabutin solubility in formulations. Diluted samples were analyzed at t0 (blue bars, 10x dilution; gray bars, 100x dilution) and after 24 hours at room temperature (orange bars, 10x dilution; yellow bars, 100x dilution). was analyzed.

[0128] Example 4 Reconstitution of rifabutin from a solution of rifabutin in transcutol HP and further dilution with 0.9% saline: 1.50 g (1.77 mmol) of rifabutin powder was weighed into a 40 mL glass vial. 3 mL of DMI or 3 mL of transcutol HP was added, and the very thick suspension was swirled for approximately 6 hours and 18 hours, respectively, to obtain a very thick solution. The solution was sterilized by filtration through a 0.2 μm filter (PTFE filter). To 1 mL aliquots of the two solutions containing approximately 500 mg (approximately 0.590 mmol) of rifabutin, 1 mL of a solution containing 0.590 mmol of acetic acid in water was added with gentle swirling. Complete dissolution occurred immediately. Analysis before and after filtration (0.2 μm PTFE filter) showed similar potencies for all solutions, consistent with the results reported in Example 3.

[0129] To separate 1 ml aliquots of each of the two solutions containing approximately 500 mg (approximately 0.590 mmol) of rifabutin, 5 ml of a 1:4 water / 0.9% saline solution containing 0.590 mmol of acetic acid was added. A complete solution was immediately formed. Analysis before and after filtration (0.2 μm PTFE filter) showed similar potencies of all solutions, ranging from approximately 46.7 to 48.2 mg / ml.

[0130] Example 5 Analytical method and sample preparation for solubility determination: Dilutions for solubility determination were prepared by adding 25 μL of mother liquor to 500 μL of 0.1% TFA in acetonitrile (dilution 1 21 fold). If necessary, a second dilution was prepared by adding 25 μL of dilution 1 to 500 μL of 0.1% TFA in acetonitrile (dilution 441 fold).

[0131] LCMS method HPLC: Agilent 1200 Detector 1: DAD set to 276 nm Detector 2: Mass analyzer

[0132] HPLC conditions: Column: Sunfire C18 (100 × 4.6 mm × 3.5 μm) Column temperature: 35℃ Flow cell: 10mm channel Mobile phase A: 0.1% TFA in water Mobile phase B: 0.1% TFA in acetonitrile Flow rate: 1.0ml / min

[0133] [Table 11]

[0134] Rifabutin had a retention time of 6.8-6.9 minutes. The peak area observed from the UV detector for the compound of interest was used to calculate the concentration of the component in the solution. No interference with the vehicle components was verified.

[0135] Tables 3 and 5 report the concentration of rifabutin in solutions containing 1 molar equivalent of acid in dimethyl isosorbide / water 50 / 50 (v / v) or transcutol HP / water 33.3 / 66.7 (v / v), freshly prepared and after 24 hours of storage at room temperature (RT) or 5°C.

[0136] The reconstituted solution can be stored at RT and 5°C for 24 hours.

[0137] Tables 4, 6, and 7 report the concentrations of rifabutin after up to 100-fold dilution in 0.9% saline and storage at RT for 24 hours. The pH and osmolality of the solutions were also recorded.

[0138] The reconstituted solution may be diluted without limit to make the composition suitable for the desired route of administration.

[0139] Dilution of the reconstituted solution with 0.9% saline will have a final pH that depends on the pKa of the acid used; preferred acids should have a pKa value greater than 2, preferably greater than 3. Preferably, such acids are D-glucuronic acid, D-gluconic acid, L-lactic acid, and acetic acid. Most preferably, the acid is acetic acid or D-glucuronic acid.

[0140] Example 6 Reconstitution of Rifabutin from a Large Solution of Rifabutin in DMI and Further Dilution with 0.9% Saline: Preparation of vial 1: 1200 ml of DMI was heated in a 5 L glass tank at 40°C, and 600 g (0.708 mol) of rifabutin powder was added portionwise while stirring at 40°C. Complete dissolution was achieved in approximately 6 hours, and the solution was allowed to return to room temperature. The solution was then filtered through a PVDF (polyvinylidene fluoride), Nylon, or PTFE (polytetrafluoroethylene) 0.22 μm sterile filter. A volume of the solution equivalent to 500 mg (0.590 mmol) of rifabutin was transferred via sterile tubing to a 10 ml sterile, depyrogenated vial, which was then sealed with a Fluorotec rubber stopper and a flip-off overseal. Additionally or alternatively, the vial was subjected to terminal sterilization in an autoclave at 121°C for 20 minutes. This procedure was repeated starting with two different rifabutin batches.

[0141] Analytical and stability data after terminal sterilization are reported in Tables 8 and 9, respectively.

[0142] Preparation of Vial 2: A solution of 4% w / v acetic acid in sterile water for injection was transferred via sterile tubing to a 10 ml sterile depyrogenated vial, which was sealed with a Fluorotec rubber stopper and flip-off overseal and placed in an autoclave for terminal sterilization.

[0143] Reconstitution of rifabutin before use: 1 ml of sterile 4% w / v acetic acid (0.66 mmol) in water for injection was drawn from vial 2 with a 1 ml syringe and added to vial 1 with gentle swirling.

[0144] Dilution of reconstituted rifabutin solution in 0.9% saline: The reconstituted solution was brought to a total volume of 10 ml by adding a sterile solution of 0.9% NaCl solution (saline for injection) to give a final concentration of rifabutin of 50 mg / ml.

[0145] The analytical data are reported in Table 10.

[0146] Alternatively, the reconstituted solution can be drawn from the vial by syringe and injected directly into a saline bag for infusion.

[0147] [Table 8]

[0148] [Table 9]

[0149] [Table 10]

[0150] Example 7 Analytical methods and sample preparation for stability testing and impurity determination

[0151] HPLC conditions HPLC Instrument: HPLC with UV detector or equivalent Waters Alliance Software: Empower 3 System or equivalent Column: C8, 5 μm, 4.5 × 150 mm, Waters Spherisorb Flow rate 10ml / min Injection volume 10μ1 Wavelength 254nm Mobile phase: 55% ACN + 45% 13.6 g / L (0.1 M) potassium dihydrogen phosphate. This mixture must be adjusted to pH 6.5 ± 0.1 with 2 N NaOH. Elution: Isoconcentration Run time: 2.5 times the retention time of rifabutin RRT Rifabutin: 1 (approximately 9 minutes) (Based on rifabutin) Impurity E: approx. 0.5 Impurity B: approx. 0.6 Impurity D: approx. 0.8 Impurity C: approx. 1.4

[0152] Sample preparation

[0153] Blank solution Mobile phase as is

[0154] Test Solution 1 - For determination of the concentration of rifabutin in the bulk solution: 0.5 mg of rifabutin in DMI (accurately weighed) was transferred to a 10 mL volumetric flask and diluted to volume with acetonitrile. 1.5 mL of the resulting solution was transferred to a 50 mL volumetric flask, diluted to volume with mobile phase, and mixed (0.5 mg / mL).

[0155] Test Solution 2 - For vial content determination: After removal of the vial flip-off, approximately 5 ml of the ACN in the sealed vial was transferred using a 10 ml syringe. The resulting solution was then transferred to a 50 ml volumetric flask and washed with ACN at least five times to ensure accurate recovery of the total volume of the vial's solution by adding the wash solution to the 50 ml volumetric flask. The seal and stopper were then removed, and the vial was washed two more times. The volume was then diluted with ACN. Finally, the resulting solution was diluted to 1 ml to 20 ml with mobile phase and mixed (0.5 mg / ml).

[0156] Standard solution: Approximately 25 mg of rifabutin CRS (accurately weighed) was transferred to a 50 mL volumetric flask. 5 mL of acetonitrile was added and the solution was diluted to volume with mobile phase and mixed (0.5 mg / mL).

[0157] Diluted standard solution: 1 ml of rifabutin standard solution was diluted to 100 ml with mobile phase (0.005 mg / ml).

[0158] Separation solution: Approximately 10 mg of rifabutin CRS was dissolved in 2 ml MeOH, 1 ml of 2N NaOH was added, and the solution was allowed to stand for approximately 4 minutes. 1 ml of 2N HCl was added, and the solution was diluted to 50 ml with the mobile phase.

[0159] System Suitability Regarding the separation solution: The chromatogram showed a major peak for the surfactant, two minor peaks for degradants, and a major peak for rifabutin at RRTs of approximately 0.5, 0.6, 0.8, and 1.0, respectively. The resolution between the rifabutin peak eluting at a relative retention time of approximately 0.8 and the degradant peak was greater than 1.3. -For standard preparations: the column efficiency was greater than 2000 theoretical plates and the relative standard deviation of replicate injections was less than 2.0%.

[0160] Calculations for Test Solution 1 The amount of rifabutin (in mg) in each g of sample is calculated using the following formula:

number

[0161] The calculation of the percentage of each impurity is done using the following formula:

number

[0162] Calculations for Test Solution 2 The content of rifabutin (in g) in each vial is calculated using the following formula:

number

[0163] The calculation of the percentage of each impurity is done using the following formula:

number

[0164] Incorporation by Reference References and citations to other documents (e.g., patents, patent applications, patent publications, journals, books, articles, web content) are made throughout this disclosure. All such documents are incorporated herein by reference in their entirety for all purposes.

[0165] equivalent Various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the entire contents of this document, including reference to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification, and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof.

Claims

1. A rifabutin formulation comprising: a) rifabutin; b) an acid having a pKa greater than 2; c) water; and d) an organic solvent selected from the group consisting of dimethyl isosorbide (DMI), diethylene glycol monoethyl ether, and dimethylacetamide (DMA).

2. The formulation of claim 1, wherein the acid is selected from the group consisting of hydrochloric acid, methanesulfonic acid, phosphoric acid, L-tartaric acid, D-glucuronic acid, L-malic acid, D-gluconic acid, L-lactic acid, and acetic acid.

3. The formulation described in claim 2, wherein the acid is acetic acid or D-glucuronic acid.

4. A formulation described in any one of claims 1 to 3, wherein the amount of acid relative to rifabutin is 1 to 3 molar equivalents.

5. The formulation of claim 4, wherein the molar ratio of rifabutin to acid is 1:

1.

6. The formulation of claim 1, wherein the w / v ratio of rifabutin to organic solvent is 2:1 to 1:

3.

7. The formulation of claim 6, wherein the w / v ratio of rifabutin to organic solvent is 1:

2.

8. A formulation according to any one of claims 1 to 7, comprising at least a 10 mg / ml rifabutin solution.

9. A formulation according to any one of claims 1 to 8, comprising at least a 50 mg / ml rifabutin solution.

10. A method for preparing a formulation of rifabutin, comprising: preparing a solution comprising an organic solvent, water, and an acid; adding said solution to rifabutin powder, thereby dissolving said rifabutin in said solution; wherein the acid is an acid having a pKa greater than 2 and the organic solvent is selected from the group consisting of dimethyl isosorbide (DMI), diethylene glycol monoethyl ether, and dimethylacetamide (DMA).

11. A method for preparing a formulation of rifabutin, comprising: preparing a solution comprising water and an acid; adding said solution to a solution of rifabutin in a solvent to form an aqueous rifabutin formulation. wherein the acid is an acid having a pKa greater than 2 and the organic solvent is selected from the group consisting of dimethyl isosorbide (DMI), diethylene glycol monoethyl ether, and dimethylacetamide (DMA).

12. The method of claim 10 or claim 11, wherein the w / v ratio of rifabutin to organic solvent is 2:1 to 1:

3.

13. A pharmaceutical composition for treating bacterial infection, characterized in that it is administered by injection or inhalation, and comprises a rifabutin formulation described in any one of claims 1 to 9.

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