Rifbutin therapeutic methods, uses and compositions

Abstract

A rifobetine formulation is produced from a rifobetine powder in the presence of an acid, water and a solvent adapted to promote dissolution of the rifobetine. A method of preparing a rifobetine formulation, the method comprising: preparing a solution comprising a solvent, water, and an acid; and adding the solution to rifobetine powder, so that the rifobetine is dissolved in the solution. A method of preparing a rifobetine formulation, the method comprising: preparing a solution comprising water and an acid; and adding the solution to a rifobetine solution in a solvent, thereby producing an aqueous rifobetine formulation. A method of treating a bacterial infection in a subject, the method comprising administering a therapeutically effective amount of rifobetine in an injectable formulation or by inhalation.

Description

[0001] Related Applications

[0002] This is a divisional application of a patent application for invention with an application date of August 3, 2020, an application number of 202080005144.X, and an invention title of "Rifabutin Treatment Methods, Uses, and Compositions". Technical Field

[0003] The present invention generally relates to formulations containing the antibiotic rifabutin, methods of making such formulations, and methods of using such formulations to treat bacterial infections. Background Art

[0004] Millions of people die each year from bacterial infections, and this number is increasing due to the spread of antibiotic-resistant bacterial strains. For example, according to official estimates, in the United States, the European Union, and India alone, more than 100,000 people die each year from antibiotic-resistant bacterial infections, and some experts believe that the official statistics are seriously underestimated because the full impact of antibiotic resistance is still unknown. Unfortunately, in recent decades, the process of developing new antibiotics has slowed down, and many existing antibiotics have problems that limit their effectiveness.

[0005] One existing antibiotic that has not reached its full therapeutic potential is rifabutin, also known as LM427 and Although rifabutin is active against a variety of bacteria, its poor water solubility makes it difficult to deliver the antibiotic at an effective dose for treating infections (other than those reported in the label) and difficult to effectively prevent the development of resistance. Based on studies of rifabutin and related antibiotics in the same class, it is believed that high levels of free rifabutin are necessary for killing microorganisms and preventing the development of resistance. Thus, the therapeutic utility of rifabutin is hindered by technical problems, and millions of people continue to suffer from bacterial infections due to the lack of appropriate treatment options. Summary of the Invention

[0006] The present invention provides pharmaceutical formulations containing a high concentration of rifabutin. Preferred compositions of the present invention include rifabutin powder formulated in water, solvents, and acids. The combinations of the present invention allow for the dissolution of rifabutin at high concentrations. The formulated solutions can be diluted without limitation so that the compositions are suitable for the desired route of administration.

[0007] ​The formulations of the present invention allow for the delivery of an effective amount of rifabutin via routes of administration that were not possible with prior rifabutin-containing compositions. For example, the formulations of the present invention enable rifabutin to be provided parenterally (including intravenously or by inhalation). Additionally, the formulations of the present invention eliminate the need to first lyophilize rifabutin and then reconstitute it for administration, which is a rather expensive process.

[0008] In another aspect of the present invention, rifabutin is prepared as a powder, and its shelf life is the same as that of the rifabutin active pharmaceutical ingredient (API). As detailed below, the rifabutin formulations of the present invention preferably comprise rifabutin powder dissolved in an organic solvent.

[0009] According to the present invention, highly concentrated rifabutin formulations are rapidly obtained from any rifabutin API and used as such or optionally further diluted with sterile water or a pharmaceutically acceptable solution. The formulations of the present invention can be used to treat a variety of conditions caused by or associated with bacterial infections, such as, but not limited to, bacteremia, meningitis, ventilator-associated bacterial pneumonia (VABP), hospital-acquired bacterial pneumonia (HABP), and periprosthetic joint infection (PJI).

[0010] In one aspect, the present invention provides a parenteral formulation of rifabutin manufactured by preparing a solution in the presence of an acid suitable for facilitating the dissolution of rifabutin. The solution preferably comprises a solvent and water in proportions suitable for the intended use of the formulation.

[0011] The formulations of the present invention are suitable for any parenteral route of administration. The formulations are suitable for parenteral, intravenous, intra-arterial administration, or pulmonary delivery. The formulations are also suitable for administration by inhalation or by injection.

[0012] The formulations of the present invention are reconstituted solutions that may need to be diluted prior to parenteral administration. The formulations of the present invention comprise a defined proportion of solvent and water. The proportion can be a v / v ratio. The solution can comprise a 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 can comprise a 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.

[0013] The solvent can be polyoxyethylene sorbitan monooleate (Tween 80), sorbitan monooleate polyoxyethylene sorbitan monolaurate (Tween 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerol, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (transcutol HP), or isosorbide dimethyl ether (DMI).

[0014] 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.

[0015] The reconstitution 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), but the concentration of the reconstitution solution can be as high as about 300 mg / ml. In certain embodiments, a more dilute solution is required and it is obtained by adding more water to the solvent. For example, rifabutin with a solvent / water ratio of 1:4 will produce a solution of about 50 mg / ml. However, this dilution will take additional time to dissolve the rifabutin powder. Alternatively, rifabutin can be dissolved in the solvent and then the reconstitution solution is obtained without further modification. Generally, for IV solutions, it is desirable to keep the rifabutin / solvent ratio as low as possible. Appropriate ranges are provided herein.

[0016] The formulations of the present invention are effective in treating bacterial infections. The infection can include one or more of the following: Acinetobacter baumannii, Campylobacter jejuni, Chlamydia trachomatis, Haemophilus ducreyi, Haemophilus influenzae, Helicobacter pylori, Mycobacterium chelonae, Mycobacterium kansasii, Mycobacterium leprae, Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, Neisseria gonorrhoeae, Neisseria meningitidis, Staphylococcus, Streptococcus (e.g., group A Streptococcus), and Toxoplasma gondii or any other pathogen sensitive to rifabutin.

[0017] 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.

[0018] The w / v ratio of rifabutin to the 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. The w / v ratio of rifabutin to the 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.

[0019] On the other hand, the present invention provides a method for preparing a parenteral formulation of rifabutin, which is carried out by: preparing a solution comprising a solvent and distilled water, adding an acid to the solution, and introducing the solution into rifabutin powder, thereby dissolving rifabutin in the solution.

[0020] On the other hand, the present invention provides a method for preparing a parenteral formulation of rifabutin, which is carried out by: preparing a solution of rifabutin in a certain solvent and an aqueous solution of an acid, and then mixing the two solutions.

[0021] The formulation can have any of the properties described above regarding the formulation. The acid and the solvent can be any of those described above. Water and the solvent can be combined in any of the above ratios.

[0022] The method of the present invention includes diluting the formulated rifabutin solution without limitation so that the composition is suitable for the desired route of administration into a pharmaceutically acceptable diluent (e.g., but not limited to sterile water, sodium chloride (i.e., saline) solution, glucose water, lactated Ringer's solution).

[0023] The step of dissolving rifabutin can include swirling, stirring or agitating the solution. The step of dissolving rifabutin can be carried out for a defined time. The step of dissolving rifabutin can 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.

[0024] Rifabutin can be provided in the form of a solid powder.

[0025] Rifabutin can be provided in the form of a solution in a solvent.

[0026] On the other hand, the present invention provides a method for treating a bacterial infection in a subject by administering a therapeutically effective amount of a parenteral formulation of rifabutin.

[0027] The bacterial infection can include one or more of the following: Acinetobacter baumannii, Campylobacter jejuni, Chlamydia trachomatis, Haemophilus ducreyi, Haemophilus influenzae, Helicobacter pylori, Mycobacterium chelonae, Mycobacterium kansasii, Mycobacterium leprae, Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, Neisseria gonorrhoeae, Neisseria meningitidis, Staphylococcus, Streptococcus (e.g., group A Streptococcus) and Toxoplasma gondii or any other pathogen sensitive to rifabutin.

[0028] The formulation can have any of the properties described above regarding the formulation.

[0029] The formulation can be provided parenterally, intravenously or by inhalation.

[0030] Aspects of the present disclosure provide uses of rifabutin, an acid, a solvent, and a diluent in the manufacture of a medicament for treating bacterial infections.

[0031] In certain embodiments, the diluent is water.

[0032] In certain embodiments, the w / v ratio of rifabutin to the 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.

[0033] In certain embodiments, the w / v ratio of rifabutin to the solvent is about 1:2.

[0034] In certain embodiments, the solvent is polyoxyethylene sorbitan monooleate (Tween 80), sorbitan monooleate polyoxyethylene sorbitan monolaurate (Tween 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerol, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (transcutol HP), or isosorbide dimethyl ether (DMI).

[0035] In certain embodiments, the solvent is DMI or transcutol HP.

[0036] 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.

[0037] In certain embodiments, the solvent and water are present in a ratio of about 1:1 to about 1:2.

[0038] 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.

[0039] In certain embodiments, the acid can be D-glucuronic acid.

[0040] In certain embodiments, the acid can be acetic acid.

[0041] In certain embodiments, the amount of acid relative to rifabutin is between 1 and 3 molar equivalents or between 1 and 2 molar equivalents.

[0042] In certain embodiments, the amount of acid relative to rifabutin can be 1 molar equivalent.

[0043] In certain embodiments, the molar ratio of rifabutin to acid is about 1:1.

[0044] 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.

[0045] In certain embodiments, the bacterial infection is Acinetobacter baumannii, Campylobacter jejuni, Chlamydia trachomatis, Haemophilus ducreyi, Haemophilus influenzae, Helicobacter pylori, Mycobacterium chelonae, Mycobacterium kansasii, Mycobacterium leprae, Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium intracellulare, Neisseria gonorrhoeae, Neisseria meningitidis, Staphylococcus, Streptococcus (e.g., group A Streptococcus), or Toxoplasma gondii.

[0046] On the other hand, the present invention provides a formulation comprising rifabutin, an acid, water, and a solvent suitable for promoting the dissolution of rifabutin.

[0047] The formulation can contain any of the above rifabutin / solvent ratios, any solvent / water ratios, or any rifabutin / acid ratios.

[0048] The formulation can contain any of the above solvents or any acid.

[0049] The formulation can contain rifabutin at any concentration, such as 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, from about 1 mg / ml to about 250 mg / ml, from about 2.5 mg / ml to about 250 mg / ml, from about 5 mg / ml to about 250 mg / ml, from about 10 mg / ml to about 250 mg / ml, from about 20 mg / ml to about 250 mg / ml, from about 50 mg / ml to about 250 mg / ml, from about 100 mg / ml to about 250 mg / ml, from about 1 mg / ml to about 200 mg / ml, from about 2.5 mg / ml to about 200 mg / ml, from about 5 mg / ml to about 200 mg / ml, from about 10 mg / ml to about 200 mg / ml, from about 20 mg / ml to about 200 mg / ml, from about 50 mg / ml to about 200 mg / ml, or from about 100 mg / ml to about 200 mg / ml. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of a method for preparing injectable rifabutin solution or inhalable rifabutin according to an embodiment of the present invention.

[0051] Figure 2 Schematic diagram of an analytical method for a rifabutin formulation.

[0052] Figure 3 Graph showing the solubility of rifabutin in the formulation.

[0053] Figure 4 Graph showing the solubility of rifabutin in the formulation. Detailed Description

[0054] Rifabutin and Challenges in Administering Rifabutin

[0055] The present invention provides compositions and methods for preparing solutions containing rifabutin suitable for parenteral or inhaled administration. Importantly, the present invention enables the administration of rifabutin intravenously in large doses. The rifabutin intravenous formulation allows for the delivery of the compound with higher efficiency and efficacy than can be achieved with existing oral rifabutin formulations. In particular, the present invention discloses the use of a water / solvent mixture as a pharmaceutically acceptable reconstitution solution for rifabutin powder in the presence of an acid to rapidly prepare a stable, highly concentrated reconstitution solution, which can then be diluted without limitation with additional water for injection or a pharmaceutically acceptable diluent to render the composition suitable for the desired route of administration.

[0056] The formulations of the present invention are related to the following requirements: High concentrations of rifabutin at the site of infection are optimal for achieving appropriate pharmacokinetic (PK) parameters (e.g., area under the curve (AUC) and C max ), which are necessary to achieve the highest clinical efficacy and prevent resistance in the treatment of bacterial infections against which rifabutin is active.

[0057] Rifabutin is a dark red-violet powder with the molecular formula C 46 H 62 NO 11 , a molecular weight of 847.02, and its structure is as follows:

[0058]

[0059] Rifabutin has broad-spectrum antibacterial activity. Compared with rifampicin, it has significantly higher activity against MAC, Mycobacterium tuberculosis, and Mycobacterium leprae. It also has activity against most atypical mycobacteria (including Mycobacterium kansasii); however, Mycobacterium chelonae is relatively resistant. Rifabutin also has activity against Staphylococcus spp., group A Streptococcus, Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, Haemophilus ducreyi, Campylobacter jejuni, Helicobacter pylori, Chlamydia trachomatis, Toxoplasma gondii, and Acinetobacter baumannii.

[0060] In healthy adult volunteers, the mean C max produced by a nominal therapeutic oral dose of 300 mg of rifabutin was 0.375 mg / L, which was reached approximately 3 hours after oral administration (rifabutin product monograph). After single PO administration of 300, 450, and 600 mg to healthy volunteers, the PK of rifabutin was linear, and C max was in the range of 0.4 to 0.7 mg / L (rifabutin product monograph). In a study of HIV-infected patients receiving the recommended rifabutin daily dose (300 mg / day), the steady-state plasma concentration was C max = 0.59 ± 0.33 mg / L, and the AUC was 8.6 ± 8.2 mg*h / L (Hafner et al., 1998). Since rifabutin is approximately 90% protein-bound, the free drug concentration after oral administration is very low. In healthy adult volunteers, at least 53% of the oral dose was absorbed, and in a multiple-dose study, the absolute bioavailability evaluated in HIV-positive patients was 20% on day 1 and 12% on day 28.

[0061] Among closely related rifamycin molecules (e.g., rifampicin), microbicidal activity is related to the ratio of the area under the concentration-time curve to the minimum inhibitory concentration (AUC / MIC), and the inhibition of resistance is related to the ratio of the free peak concentration (C max to the MIC (C max / MIC) but not related to the duration of rifampicin concentration above the MIC. In addition, the duration of the post-antibiotic effect is also related to C maxThe / MIC ratio is most closely related. Gumbo T, Louie A, Deziel MR, Liu W, Parsons LM, Salfinger M, Drusano GL, "Concentration-dependent Mycobacterium tuberculosis killing and prevention of resistance by rifampin", "Antimicrob Agents Chemother", 2007, 51(11): 3781-8, the content of which is incorporated herein by reference. Thus, in order to achieve microbial killing and prevent the emergence of drug resistance in the clinical setting, high plasma and / or high local concentrations of rifabutin are required.

[0062] The emergence of resistance to multiple antimicrobial agents in pathogenic bacteria has become a major public health threat because there are fewer or even no effective antimicrobial agents available for infections caused by these bacteria. Both Gram-positive and Gram-negative bacteria are affected by the emergence and rise of antimicrobial resistance.

[0063] Life-threatening infections caused by these pathogens are best treated in the hospital using optimized dosing regimens, which usually involve parenteral administration and, in some cases, additional use of nebulized antibiotics.

[0064] In this context, the intravenous (IV) and inhalation (IN) administration routes have several advantages over the oral route in terms of achieving high cure rates:

[0065] a) By the oral route, only a variable portion reaches the systemic circulation; the remaining drug either is not absorbed and passes through the gastrointestinal (GI) tract or undergoes a first-pass effect, i.e., metabolic transformation that occurs in the liver, resulting in the excretion of drug metabolites via bile or the kidneys.

[0066] b) By the oral route, C max and t max (time to achieve C max ) is limited by the absorption rate of the drug in the GI tract.

[0067] c) Depending on the age of the patient, the presence of concomitant diseases, and the progression of the infectious disease in the patient, the absorption rate in the human body varies greatly.

[0068] d) In contrast, by the IV route, the drug enters the bloodstream directly, t max is immediate, and C maxIt can be controlled by the concentration of the infused drug and the time over which it is infused. By definition, the AUC is the maximum value achievable relative to any other route of administration.

[0069] e) In contrast, by the IN route, the drug goes directly into the lungs, and the C max and distribution in the lungs can be controlled by the drug concentration and the particle size generated by a specific nebulizer.

[0070] Both the IV and IN routes allow rifabutin to achieve a high AUC / MIC and C max / MIC, which is crucial for efficacy during the treatment of bacterial infections sensitive to the action of rifabutin and for preventing the development of resistance. The IV route of administration allows optimization of these parameters in plasma and any compartment where the drug can be appropriately distributed, and is thus suitable for treating infections such as, for example, bacteremia, meningitis, periprosthetic joint infection (PJI), and severe pulmonary infections (e.g., ventilator-associated bacterial pneumonia (VABP) and hospital-acquired bacterial pneumonia (HABP)); in contrast, by the IN route, higher local concentrations can be achieved in the lungs to treat any bacterial pulmonary infection, in all such cases where the doctor wishes to achieve extremely high drug lung concentrations without exposing other human compartments to excessive drug levels. Alternatively, the doctor may decide to use rifabutin in combination with oral or parenteral antibiotics by the IN route.

[0071] The present invention includes a formulation of rifabutin for intravenous (IV) administration. In another embodiment of the present invention, rifabutin is administered intravenously (IV) or by inhalation (IN).

[0072] Compositions and formulations containing rifabutin

[0073] The present invention provides a composition containing a formulation in which the free base rifabutin is dissolved in water / solvent and an acid.

[0074] Its composition may be provided in the form of a pharmaceutically acceptable salt, such as a non-toxic acid addition salt, which is a salt of an amino group formed with an inorganic acid or an organic acid, said inorganic acids such as, but not limited to, hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, and perchloric acid; said organic acids such as, 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.

[0075] In some embodiments, pharmaceutically acceptable salts include, but are not limited to, adipates, alginates, ascorbates, aspartates, benzenesulfonates, benzoates, bisulfates, borates, butyrates, camphorates, camphorsulfonates, citrates, cyclopentanepropionates, digluconates, dodecyl sulfates, esulfonates, formates, fumarates, glucoheptanoates, glycerophosphates, gluconates, hemisulfates, heptanoates, hexanoates, hydroiodides, 2-hydroxy-esulfonates, lactobionates, lactates, laurates, lauryl sulfates, malates, maleates, malonates, methanesulfonates, 2-naphthalenesulfonates, nicotinates, nitrates, oleates, oxalates, palmitates, pamoates, pectates, persulfates, 3-phenylpropionates, phosphates, picrates, pivalates, propionates, stearates, succinates, sulfates, tartrates, thiocyanates, p-toluenesulfonates, undecanoates, valerates, etc. Preferably, 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 can be used. Most preferably, acetic acid, L-lactic acid, D-gluconic acid or D-glucuronic acid is used.

[0076] The pharmaceutical composition can be administered by injection, infusion, implantation (intravenous, intramuscular, subcutaneous, etc.) or by inhalation dosage form, formulation or via a suitable delivery device or implant containing conventional non-toxic pharmaceutically acceptable carriers, solvents, diluents and adjuvants. The formulation and preparation of such compositions are well known to those skilled in the art of pharmaceutical formulation.

[0077] The compositions of the present invention for parenteral use can be provided in unit dosage forms (e.g., single-dose ampoules and vials) in multiple vials containing multiple doses and in which a suitable preservative (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 Figure 1 shown, to prepare such a composition, a solution of rifabutin in a solvent and an acid in water is added to the rifabutin in powder form to facilitate dissolution. Alternatively, such a composition can be prepared by preparing a rifabutin-containing solvent and mixing it with an aqueous solution containing an acid.

[0078] Thus, the present invention provides a method for preparing an intravenous formulation of rifabutin. The method can include preparing a solution containing a solvent and distilled water. Preferably, the ratio of the solution is 1:1 or 1:2. The solvent can be any solvent, but preferably DMI or transcutol HP. An acid can be added to the solution. The acid may be suitable for promoting the dissolution of rifabutin. The acid can be any acid, but preferably acetic acid or D-glucuronic acid. The solution containing the acid can be added to the rifabutin powder. Thus, the acid dissolves rifabutin in the aqueous solution.

[0079] Rifabutin solution can be added to a pharmaceutically acceptable diluent. The diluent can be 0.9% saline.

[0080] For example, to prepare a solution of 20 mg / ml rifabutin in 4% DMI, first prepare a distilled aqueous solution of 1:1 isosorbide dimethyl ether (DMI). Then, 0.169 ml of glacial acetic acid can be added to 9.831 ml of 1:1 DMI / aqueous solution to form a reconstitution solvent (RS). Then, 1 ml of RS is added to 250 mg of rifabutin to make a 250 mg / ml solution. Stir or shake this RS-rifabutin solution until the rifabutin dissolves to form a dark crimson solution. Complete dissolution should occur within about 15 - 20 minutes. Then, the concentrated solution is diluted with 11.5 ml of water to make the final solution of 20 mg / ml rifabutin in 4% DMI. The pH of the final solution is between 5 and 6.

[0081] In another example, for preparing an intravenous solution of 2.5 mg / ml rifabutin in 0.5% DMI / 0.9% sodium chloride solution, first prepare a distilled aqueous solution of 1:1 isosorbide dimethyl ether. Then, 0.169 ml of glacial acetic acid can be added to 9.831 ml of 1:1 DMI / aqueous solution to form RS. Then, 1 ml of RS is added to 250 mg of rifabutin to make a 250 mg / ml solution. Stir or shake this RS-rifabutin solution until the rifabutin is completely dissolved (about 15 - 20 minutes). Then, the concentrated solution is diluted with 99 ml of 0.9% injectable saline to make the final solution of 2.5 mg / ml rifabutin in 0.9% saline containing 0.5% DMI, whose pH is between 5.0 and 6.0.

[0082] In another example, to prepare an intravenous solution of 5 mg / ml rifabutin in 1% transcutol HP / 0.9% sodium chloride solution, first prepare a distilled aqueous solution of 1:2 transcutol HP. Then, 0.169 ml of glacial acetic acid can be added to 14.831 ml of 1:2 transcutol HP / aqueous solution to form RS. Then, 1.5 ml of RS is added to 250 mg of rifabutin to make a 166.7 mg / ml solution. Stir or shake this RS-rifabutin solution until the rifabutin is completely dissolved (about 15 - 20 minutes). Then, the concentrated solution is diluted with 48.5 ml of 0.9% injectable saline to make the final 5 mg / ml rifabutin in 0.9% saline with 1% transcutol HP, whose pH is between 5.0 and 6.0.

[0083] In another example, an intravenous solution of rifabutin at 40 mg / ml in 8% DMI / 0.9% sodium chloride solution was prepared using 0.5 ml of a DMI solution of 250 mg rifabutin (to which 0.5 ml of a distilled aqueous solution of 114.6 mg / ml D-glucuronic acid was added). After swirling for 5 minutes, the resulting 250 mg / ml solution of RS-rifabutin was diluted with 5.25 ml of 0.9% injectable saline to make a final 0.9% saline solution of 8% DMI of rifabutin at 40 mg / ml, having a pH between 5.0 and 6.0.

[0084] Depending on the needs and clinical condition of the patient, administering the composition by IV may be more advantageous compared to oral administration as it allows for rapid introduction of the antibiotic into the systemic circulation, provides complete bioavailability, allows for better control of the pharmacokinetic parameters driving pharmacological efficacy, and avoids stability and absorption issues in the gastrointestinal tract.

[0085] A typical dose of rifabutin is a dose that is capable of achieving a plasma or local level of rifabutin >2 mg / L but <50 mg / L and an AUC of 10 mg*h / L <200 mg*h / L. max >2 mg / L but <50 mg / L and an AUC of 10 mg*h / L <200 mg*h / L.

[0086] The rifabutin solution can be further diluted with a pharmaceutically acceptable diluent. For example, a 20 mg / mL rifabutin IV solution can be further diluted with 0.9% saline to obtain a lower concentration of rifabutin for delivering a lower concentration solution to a subject. The rifabutin IV formulations disclosed herein may also require filtration. If needed, the concentrated solution or the final rifabutin solution can be filtered.

[0087] The formulations of the present invention can be used for any parenteral administration. For example, the composition can be formulated for injection or infusion. The injection or infusion can be subcutaneous or intravenous. Preferably, the composition is formulated for intravenous administration. Preferably, the composition is formulated for intravenous or inhalation administration. Thus, the formulations of the present invention can also contain a pharmaceutically acceptable diluent. The pharmaceutically acceptable diluent can have a concentration sufficient to deliver a therapeutically effective amount of rifabutin in the IV formulation to a patient suffering from an infection. The pharmaceutically acceptable diluent can be saline or sterile water. Preferably, the diluent is 0.9% saline. The solution can be administered together with a therapeutically effective amount of rifabutin to treat a patient suffering from an infection.

[0088] It should be noted that the various formulations of the present invention described herein can be used with any method of the present invention, and thus the method is not limited to any single formulation.

[0089] Method for preparing a formulation containing rifabutin

[0090] The present invention provides a method for preparing a rifabutin formulation.

[0091] Figure 1 FIG. is a schematic diagram showing a method for preparing an injectable rifabutin solution or an inhalable rifabutin according to an embodiment of the present invention. An intravenous rifabutin formulation can be manufactured by a process comprising: preparing a sterile pharmaceutically acceptable reconstitution solution in the presence of an acid suitable for promoting the dissolution of rifabutin, which comprises a solvent and distilled water in a ratio of 1:1. Rifabutin can be in solid form or in powder form soluble in a liquid medium. Rifabutin can be dissolved in an aqueous solution of a 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.

[0092] Rifabutin is soluble in an aqueous solution of 33.3% solvent (i.e., 1:2 solvent-distilled water) in the presence of an acid.

[0093] The formulation can be suitable for any non-oral administration route. The formulation can be suitable for parenteral, intravenous, intra-arterial administration. The formulation can be suitable for administration by inhalation.

[0094] The formulation can be a reconstitution solution that needs to be diluted before non-oral administration. The formulation can be a reconstitution solution suitable for non-oral administration.

[0095] Dissolution can comprise mixing a solvent and distilled water in a defined ratio. The ratio can be a v / v ratio. The solution can comprise a 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 can comprise a 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.

[0096] The solvent can be polyoxyethylene sorbitan monooleate (Tween 80), sorbitan monooleate polyoxyethylene sorbitan monolaurate (Tween 20), polyethylene glycol (PEG), propylene glycol, N-methyl-2-pyrrolidone (NMP), glycerol, ethanol, dimethylacetamide (DMA), diethylene glycol monoethyl ether (transcutol HP) or isosorbide dimethyl ether (DMI).

[0097] 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.

[0098] Formulation can include diluting a rifabutin-containing solution into a diluent. The diluent can be sterile water, a sodium chloride (i.e., saline) solution, a dextrose solution or a lactated Ringer's solution. The sodium chloride solution can be a 0.9% sodium chloride solution. The dextrose solution can be a 5% dextrose solution or a 10% dextrose solution.

[0099] The resulting solution may need to be further diluted 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., physiological saline (0.9%), 1 / 2 physiological saline (0.45%) and 0.5% saline), etc. For intravenous formulations, physiological saline (0.9%) is the preferred diluent or carrier.

[0100] Rifabutin can be reconstituted in a solution containing an acid, the amount of which is between 1 and 3 molar equivalents in a solvent and water mixture with a v / v ratio of about 9:1 to about 1:9. The w / v ratio of rifabutin to the solvent can be from 4:1 to 1:4. The dissolution time for obtaining the formulation can be less than 60 minutes. In particular, the amount of the 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 in a 1:1 or 1:2 v / v ratio, the w / v ratio of rifabutin to the solvent can be 1:2, and the dissolution time is less than 20 minutes.

[0101] The formulation (i.e., the reconstituted rifabutin solution) can be used as such or can be made by diluting it to a defined volume of diluent. The volume of the diluent can be expressed relative to the volume of the reconstituted solution. The volume of the diluent can be from 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% injectable saline. Thus, one volume of diluent results in a final solution of about 125 mg / ml, 4 volumes result in a final solution of about 50 mg / ml, 9 volumes result in a final solution of about 25 mg / ml, 24 volumes result in a final solution of about 10 mg / ml, and 99 volumes result in a final solution of about 2.5 mg / ml. A person skilled in the art understands how to make a solution with any desired final concentration.

[0102] The formulation can contain rifabutin at any suitable concentration (e.g., the concentrations described above).

[0103] The formulation can contain DMI at any concentration (e.g., those from the dilutions described above).

[0104] The formulation can contain transcutol HP at any concentration (e.g., those from the dilutions described above).

[0105] 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.

[0106] The w / v ratio of rifabutin to the solvent can be from 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 the 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.

[0107] The method can include dissolving rifabutin by vortexing, stirring, or agitating the solution. The dissolving step can be carried out for a defined time. The dissolving step can 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.

[0108] Method for treating a bacterial infection

[0109] The present invention provides a method for treating a bacterial infection. The method comprises administering to a subject suffering from a bacterial infection a rifabutin liquid formulation. The liquid formulation may comprise rifabutin, a solvent, and an acid.

[0110] The formulation may be provided by intravenous, intra - arterial, or pulmonary administration. The formulation may be provided by inhalation or injection.

[0111] The liquid formulation may be a solution of rifabutin and a diluent to be administered intravenously to a subject suffering from a bacterial infection. The formulation for IV administration may comprise a pharmaceutically acceptable solvent. The method may comprise administering an IV formulation of any rifabutin formulation described herein to a subject suffering from a bacterial infection.

[0112] The IV formulation containing rifabutin may be administered together with another antibiotic or therapeutic agent. Sequential or alternating administration may comprise providing only the IV formulation containing rifabutin for a period of time and only the other therapeutic agent for a period of time. Sequential administration may comprise an overlapping time of providing to the subject the IV formulation containing rifabutin and the formulation containing the other therapeutic agent simultaneously. The exclusive time and the overlapping time may 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 formulation of the present invention or the soluble components within the formulation may contain rifabutin and another therapeutic agent.

[0113] Without wishing to be bound by theory, any formulation of the present invention may be used in any method of the present invention.

[0114] In another aspect of the present invention, the method comprises treating a bacterial infection in a subject. The method may comprise administering a therapeutically effective amount of a formulation comprising rifabutin or a salt thereof. The rifabutin formulation may be formulated for intravenous administration. The intravenous formulation is manufactured by a process comprising preparing a solution of a solvent and distilled water in a ratio of 1:1 in the presence of an acid suitable for facilitating the dissolution of said rifabutin. Preferably, the solvent is DMI. Preferably, the solvent is transcutol HP. Preferably, the intravenous formulation is a solution of rifabutin at about 2.5 mg / mL in 0.5% DMI and 0.9% sodium chloride solution.

[0115] In another embodiment, the method may comprise providing a combination therapy of an IV formulation of rifabutin or a salt thereof and another therapeutic agent to a subject suffering from a bacterial infection. The IV formulation may comprise a pharmaceutically acceptable solvent. The therapeutic agent may be present in the formulation for IV administration.

[0116] An IV formulation containing rifabutin and a formulation containing another therapeutic agent can be provided or administered simultaneously, provided or administered in any order sequentially, or provided or administered in an alternating manner. Sequential administration or alternating administration can include providing only the IV formulation containing rifabutin for a period of time and only the formulation containing another therapeutic agent for a period of time. Sequential administration can include an overlapping time of providing the IV formulation containing rifabutin and the formulation containing another therapeutic agent to a subject simultaneously. The exclusive time and the overlapping time 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.

[0117] In another embodiment, rifabutin is filled into glass vials and sterilized using one of the procedures for terminal sterilization. These procedures are well known to those skilled in the art and can be carried out using gamma radiation or heat sterilization.

[0118] Then, a sterile solution of 50:50 water for injection and a solvent containing approximately 1 molar equivalent of acid is added to the sterile rifabutin to form a concentrated reconstitution solution.

[0119] In another embodiment, the reconstituted rifabutin formulation is sterile filtered.

[0120] In another embodiment, the diluted rifabutin formulation is sterile filtered.

[0121] Example

[0122] Example 1

[0123] Preliminary assessment of solubility in solvents: To determine whether a pharmaceutically acceptable solvent can dissolve rifabutin powder and at what concentration, a sufficient volume of solvent sufficient to achieve a maximum target solubility of 300 mg / ml was added to an aliquot of rifabutin powder. After stirring at room temperature for 24 hours, the sample was centrifuged and the supernatant was analyzed by HPLC. The rifabutin chromatographic peak area was compared with the titration curve. The results of this preliminary screening are reported in Table 1.

[0124] Table 1. Solubility results in formulation vehicles

[0125]

[0126]

[0127] The "thermodynamic" solubility screening results showed that dimethyl isosorbide (DMI) was the best solvent. Although interesting, the 24-hour solubility data was irrelevant in the reconstitution process of the antibiotic powder, as the reconstitution solvent had to be able to dissolve the antibiotic within a few minutes, which was sufficient in practice for the operator to prepare rifabutin for injection or inhalation.

[0128] Rifabutin could be dissolved in DMI at a concentration of ≥250 mg / ml, but was shown to have a dissolution time longer than the acceptable one. In addition, since the DMI-rifabutin solution was separated from the aqueous solution, the DMI-rifabutin solution could not be diluted with a pharmaceutically acceptable solution (e.g., saline).

[0129] Surprisingly, the addition of acid to the DMI / aqueous solution allowed the rapid dissolution of rifabutin powder, and the highly concentrated reconstituted rifabutin solution could be arbitrarily diluted with water or 0.9% saline without any rifabutin precipitation.

[0130] Example 2

[0131] Small-scale solubility screening of solvents and acids: Weighed rifabutin powder (in an amount between 100 and 200 mg) was placed in a 1.8-ml glass vial. Examples of reconstitution solutions were prepared by mixing different solvents in the amounts specified in Table 2 and water containing different acids. The solutions were stirred for 15 minutes at RT using a magnetic stir bar and briefly vortexed. The samples were filtered using a centrifugal filter (0.2-μm PTFE filter), and the concentration of the reconstituted solution was determined by HPLC analysis. The rifabutin chromatographic peak area was compared with the titration curve, and the results were reported in Table 2.

[0132] Table 2. Small-scale solubility screening

[0133]

[0134]

[0135] Table 3. Solubility of rifabutin reconstitution solutions at t = 0 and t = 24 hours

[0136]

[0137] Table 4. Solubility and pH of rifabutin reconstitution solutions diluted with 0.9% saline at t = 0 and t = 24 hours

[0138]

[0139]

[0140] Example 3:

[0141] Recovery of rifabutin and large-scale evaluation of further dilution with 0.9% saline: Weigh 1.50 g (1.77 mmol) of rifabutin powder and place it in a 40 mL glass vial. Add an equimolar amount of acid (1.77 mmol) dissolved in 6 mL of isosorbide dimethyl ether / water 50 / 50 (v / v). Vortex the solution for 30 seconds, stir vigorously for 15 minutes at RT using a magnetic stir bar, and then vortex again for 30 seconds.

[0142] Filter the sample using a syringe and filter (0.2 μm PTFE filter), and determine the concentration of the recovered rifabutin solution by HPLC analysis. Aliquots (1 mL) of the undiluted solution are stored at RT and 5 °C for 24 hours.

[0143] Figure 2 It is a schematic diagram showing the analytical method of the rifabutin formulation. Aliquots (500 μL) of the filtrate are diluted 10-fold and 100-fold in 0.9% saline. These dilutions are prepared in triplicate. The diluted samples are visually inspected to determine the presence of immediate precipitation and filtered after 15 minutes. The concentration of the API is determined by HPLC analysis and the pH is recorded. The diluted samples are stored at RT for 24 hours.

[0144] After 24 hours of storage, the diluted and undiluted samples are reanalyzed by HPLC analysis to determine the API concentration, and the pH value is recorded.

[0145] The experimental details, results, and recorded pH values of the solubility test of the undiluted sample are shown in Tables 5, 6, and 7, and are graphically represented in Figure 3 and 4 graphically.

[0146] Table 5. Concentration and pH of the recovered rifabutin solution at t = 0 and stored at 5 °C and room temperature for 24 hours

[0147]

[0148] Figure 3 It is a graph showing the solubility of rifabutin in the formulation. Larger-scale undiluted samples are analyzed at t0 (blue bars), after 24 hours at room temperature (red bars), and after 24 hours at 5 °C (green bars).

[0149] Table 6. Concentration and pH of the rifabutin solution with a nominal concentration of 25 mg / ml stored at room temperature for 24 hours*.

[0150]

[0151] *The experiment has been performed in triplicate.

[0152] For solutions formed from acetic acid, L-lactic acid, D-gluconic acid, and D-glucuronic acid, the osmolarities of these solutions were 632, 644, 622, and 645 mOsm / kg, respectively.

[0153] Table 7. Concentration and pH of rifabutin solutions with a nominal concentration of 2.5 mg / ml stored at room temperature for 24 hours*.

[0154]

[0155] *Experiments were performed in triplicate.

[0156] For solutions formed from acetic acid, L-lactic acid, D-gluconic acid, and D-glucuronic acid, the osmolarities of these solutions were 323, 319, 316, and 318 mOsm / kg, respectively.

[0157] Figure 4 is a graph showing the solubility of rifabutin in the formulation.

[0158] Diluted samples were analyzed at t0 (blue bars, 10-fold dilution; gray bars, 100-fold dilution) and after 24 hours at room temperature (orange bars, 10-fold dilution; yellow bars, 100-fold dilution).

[0159] Example 4

[0160] Recovery of rifabutin from a rifabutin solution in transcutol HP and further dilution with 0.9% saline: Weighed 1.50 g (1.77 mmol) of rifabutin powder and placed it in a 40 mL glass vial. Added 3 ml of DMI or 3 ml of transcutol HP and vortexed the very concentrated suspension for about 6 hours and 18 hours, respectively, to obtain a very thick solution. The solution was sterile filtered through a 0.2 μm filter (PTFE filter).

[0161] With gentle vortexing, 1 ml of an aqueous solution containing 0.590 mmol of acetic acid was added to 1 ml aliquots of two solutions containing approximately 500 mg (about 0.590 mmol) of rifabutin. A perfect solution was immediately formed. Analysis before and after filtration (0.2 μm PTFE filter) showed that the titers of all solutions were similar, consistent with the results reported in Example 3.

[0162] To another 1 ml aliquot of two solutions containing approximately 500 mg (about 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 perfect solution was immediately formed. Analysis before and after filtration (0.2 μm PTFE filter) showed that the titers of all solutions were similar, approximately 46.7 to 48.2 mg / ml.

[0163] Example 5

[0164] Analytical method and sample preparation for solubility determination: A dilution solution (diluted 121 times) for solubility determination was prepared by adding 25 μL of the stock solution to 500 μL of an acetonitrile solution containing 0.1% TFA. If necessary, a second dilution solution (diluted 441 times) can be prepared by adding 25 μL of dilution solution 1 to 500 μL of an acetonitrile solution containing 0.1% TFA.

[0165] LCMS method

[0166] HPLC: Agilent 1200

[0167] Detector 1: DAD, set at 276 nm

[0168] Detector 2: Mass spectrometer

[0169] HPLC conditions:

[0170] Column: Sunfire C18 (100x 4.6 mm x 3.5 μm)

[0171] Column temperature: 35 °C

[0172] Flow cell: 10 mm optical path

[0173] Mobile phase A: 0.1% aqueous TFA solution

[0174] Mobile phase B: 0.1% acetonitrile solution of TFA

[0175] Flow rate: 1.0 ml / min

[0176] HPLC Mobile Phase Gradient. Time (minutes) Mobile Phase A (%) Mobile Phase B (%) 0 90 10 9 10 90 10 90 10 11 90 10

[0177] The retention time of rifabutin was 6.8 - 6.9 minutes. The concentration of the components in the solution was calculated using the peak area observed by the UV detector of the compound of interest. It was confirmed that there was no interference with the components of the vehicle.

[0178] Tables 3 and 5 report the concentrations of rifabutin in isosorbide dimethyl ether / water 50 / 50 (v / v) or transcutol HP / water 33.3 / 66.7 (v / v) solutions containing 1 molar equivalent of acid, freshly prepared and after storage at room temperature (RT) or 5 °C for 24 hours.

[0179] The reconstituted solution can be stored at RT and 5 °C for 24 hours.

[0180] Tables 4, 6, and 7 report the concentrations of rifabutin after dilution up to 100-fold in 0.9% saline and storage at RT for 24 hours. The pH and osmolality of the solutions were also recorded.

[0181] The reconstituted solution can be diluted without limit to render the composition suitable for the desired route of administration.

[0182] The final pH of the reconstituted solution diluted with 0.9% saline depends on the pKa of the acid used, and the pKa value of the preferred acid is greater than 2, preferably greater than 3. Preferably, such acid is D-glucuronic acid, D-gluconic acid, L-lactic acid, and acetic acid. Most preferably, the acid is acetic acid or D-glucuronic acid.

[0183] Example 6

[0184] Reconstitution of rifabutin from a large-scale solution of rifabutin in DMI and further dilution with 0.9% saline:

[0185] Preparation of Vial 1: 1200 ml of DMI was heated in a 5 L glass jar at 40 °C, and 600 g (0.708 mol) of rifabutin powder was added in portions with stirring at 40 °C. Complete dissolution was obtained in about 6 hours, and the solution was allowed to return to room temperature. Then, the solution was filtered through a 0.22 μm sterile filter of PVDF (polyvinylidene fluoride), nylon, or PTFE (polytetrafluoroethylene). A volume of the solution equivalent to 500 mg (0.590 mmol) of rifabutin was transferred via a sterile tube to a 10 ml sterile and pyrogen-free vial, and the vial was sealed with a Fluorotec rubber stopper and a flip-top seal. Additionally or alternatively, the vial was terminally sterilized in an autoclave at 121 °C for 20 minutes. This procedure was repeated starting from two different batches of rifabutin.

[0186] The analytical and stability data after terminal sterilization were recorded in Tables 8 and 9, respectively.

[0187] Preparation of Vial 2: A sterile aqueous solution for injection of 4% w / v acetic acid was transferred via a sterile tube to a 10 ml sterile and pyrogen-free vial, and the vial was sealed with a Fluorotec rubber stopper and a flip-top seal and terminally sterilized in an autoclave.

[0188] Reconstitution of Rifabutin Before Use: 1 ml of the sterile aqueous solution of 4% w / v acetic acid (0.66 mmol) was withdrawn from vial 2 with a 1 ml syringe and added to vial 1 with gentle vortexing.

[0189] Dilution of Reconstituted Rifabutin Solution in 0.9% Saline:The total volume of the reconstitution solution was made up to 10 ml by adding a sterile solution of 0.9% NaCl solution (saline for injection) to achieve a final concentration of rifabutin of 50 mg / ml.

[0190] The analytical data are listed in Table 10.

[0191] Alternatively, the reconstitution solution can be withdrawn from the vial with a syringe and injected directly into an infusion saline bag.

[0192] Table 8. Analysis of Vial 1 Prepared from Two Different Batches of Rifabutin

[0193]

[0194] * Change in the impurity content of rifabutin in Vial 1 compared to the rifabutin drug substance (API). Data are in % impurities and are reported as % impurities in Vial 1 - % impurities in the API.

[0195] Table 9. Stability Results of Vial 1 Stored at 2 - 8 °C and 25 °C ± 2 °C / 60% RH ± 5% RH

[0196]

[0197] * Change in the impurity content of rifabutin in Vial 1 after storage under different conditions. Data are in % impurities and are recorded as % impurities in Vial 1 on Day 15, Day 30, and Day 90 - % impurities in Vial 1 on Day 0.

[0198] Table 10. Analysis of the Reconstitution Solution after Dilution to 50 mg / ml in 0.9% Saline

[0199]

[0200] * Change in the impurity content of rifabutin after reconstitution and dilution with 0.9% saline. Data are in % impurities and are recorded as % impurities in the reconstitution / dilution solution - % impurities in Vial 1.

[0201] Example 7

[0202] Analytical Methods and Sample Preparation for Stability Studies and Impurity Determination

[0203] HPLC Conditions

[0204]

[0205] Sample Preparation

[0206] Blank Solution : Mobile phase as received.

[0207] Test Solution 1 - for Determining the Concentration of Rifabutin in the Bulk Solution:

[0208] Transfer 5 mg of rifabutin to a DMI solution, weigh accurately, transfer to a 10 mL volumetric flask, and dilute to a certain volume with acetonitrile. Transfer 1.5 mL of the resulting solution to a 50 mL volumetric flask, dilute to a certain volume with the mobile phase, and mix (0.5 mg / mL).

[0209] Test Solution 2 - for Determining Vial Content:

[0210] After removing the flip-off cap of the vial, transfer approximately 5 mL of ACN from the sealed vial by using a 10 mL syringe. Then, transfer the resulting solution to a 50 mL volumetric flask and wash at least 5 times with ACN by adding the wash solution to the 50 mL volumetric flask in order to accurately recover the total amount of solution in the vial. Then, remove the seal and the stopper, and wash the vial two more times. Then, dilute the volume with ACN.

[0211] Finally, dilute the resulting solution from 1 mL to 20 mL with the mobile phase and mix (0.5 mg / mL).

[0212] Standard Solution Weigh accurately approximately 25 mg of rifabutin CRS and transfer to a 50 mL volumetric flask. Add 5 mL of acetonitrile, and dilute the solution to a certain volume with the mobile phase, and mix (0.5 mg / mL).

[0213] Diluted Standard Solution Dilute 1 mL of the rifabutin standard solution to 100 mL with the mobile phase (0.005 mg / mL).

[0214] Resolution Solution Dissolve approximately 10 mg of rifabutin CRS in 2 mL of MeOH, add 1 mL of 2N NaOH, and allow the solution to stand for approximately 4 minutes. Add 1 mL of 2N HCl, and dilute the solution to 50 mL with the mobile phase.

[0215] System Suitability

[0216] - For the resolution solution: The chromatogram shows that the RRTs of the main peak of the degradant, the two minor peaks of the degradant, and the main peak of rifabutin are approximately 0.5, 0.6, 0.8, and 1.0, respectively. The resolution between the eluted rifabutin peak and the degradant peak with a relative retention time of approximately 0.8 is not less than 1.3.

[0217] - Regarding Standard Preparation The column efficiency is not less than 2000 theoretical plates, and the relative standard deviation of repeated injections is not more than 2.0%.

[0218] Calculation of Test Solution 1

[0219] Calculate the amount of rifabutin in each g of the sample (in mg) using the following formula:

[0220]

[0221] Where

[0222] C = concentration of the standard (mg / mL)

[0223] P = potency of the standard (μg / mg),

[0224] W = weight of the sample (g)

[0225] AT = peak area of the sample

[0226] AS = average peak area of the standard

[0227] Calculate the percentage of each impurity using the following formula:

[0228]

[0229] Where

[0230] C = concentration of the diluted standard (mg / mL)

[0231] P = potency of the standard (μg / mg)

[0232] W = weight of the sample (g)

[0233] AI = peak area of the impurity

[0234] AS = peak area of the standard

[0235] R = mg of rifabutin per g of the sample, calculated concentration (mg / g)

[0236] Calculation of Test Solution 2

[0237] Calculate the content of rifabutin in each vial (in g) using the following formula:

[0238]

[0239] Where

[0240] C = concentration of the standard (mg / mL)

[0241] P = potency of the standard (μg / mg),

[0242] W = weight of the sample (g)

[0243] AT = peak area of the sample

[0244] AS = average peak area of the standard

[0245] Calculate the percentage of each impurity using the following formula:

[0246]

[0247] Where

[0248] C = concentration of the diluted standard (mg / mL)

[0249] P = potency of the standard (μg / mg)

[0250] W = weight of the sample (g)

[0251] AI = area of the impurity peak

[0252] AS = area of the standard peak

[0253] R = number of mg of rifabutin in each vial

[0254] Incorporated by Reference

[0255] Throughout this disclosure, other documents have been cited and referenced, such as patents, patent applications, patent publications, impurities, books, papers, and web content. All of these documents are hereby incorporated by reference for all purposes.

[0256] Equivalent

[0257] Based on the entire content of this document (including the citations to scientific and patent literature herein), various modifications of the present invention and many other embodiments thereof will become apparent to those skilled in the art. The subject matter of this document contains important information, illustrations, and guidance that can be adapted to practice the present invention in its various embodiments and their equivalents.

Claims

1. A rifabutin formulation produced from rifabutin powder in the presence of an acid, water, and a solvent suitable for promoting the dissolution of said rifabutin.

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

2.

3. The formulation according to claim 1, wherein the solvent is selected from the group consisting of PEG, propylene glycol, NMP, ethanol, DMA, transcutol HP, and dimethyl isosorbide (DMI).

4. The formulation according to claim 3, wherein the solvent is DMI or transcutol HP.

5. The formulation according to claim 1, wherein the v / v ratio of the solvent to water is from about 1:1 to about 1:

2.

6. The formulation according to 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, acetic acid, and L-aspartic acid.

7. The formulation according to claim 6, wherein the acid is acetic acid or D-glucuronic acid.

8. The formulation according to claim 1, wherein the molar ratio of rifabutin to the acid is about 1:

1.

9. The formulation according to claim 1, wherein the formulation is diluted to produce a composition suitable for a desired route of administration.

10. A method for preparing a rifabutin formulation, the method comprising: preparing a solution comprising a solvent, water, and an acid; and adding the solution to rifabutin powder, thereby dissolving the rifabutin in the solution.

11. The method according to claim 10, wherein the solvent is selected from DMI and transcutol HP.

12. The method according to claim 10, wherein the acid is selected from acetic acid and D-glucuronic acid.

13. A method for preparing a rifabutin formulation, the method comprising: preparing a solution comprising water and an acid; and adding the solution to a rifabutin solution in a solvent, thereby producing an aqueous rifabutin formulation.

14. The method according to claim 13, wherein the solvent is selected from DMI and transcutol HP.

15. The method according to claim 13, wherein the acid is selected from acetic acid or D-glucuronic acid.

16. A method for treating a bacterial infection in a subject, the method comprising administering a therapeutically effective amount of rifabutin in an injectable formulation or by inhalation.

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