Formulation for pulmonary administration of antifungal agents, and associated methods of manufacture and use

Abstract

Formulations are provided for pulmonary administration of an antifungal agent to a patient. Methods of using the formulations in the treatment of antifungal infections are also provided, including treatment of pulmonary aspergillosis with amphotericin B-containing formulations. Methods of manufacturing the formulations to achieve optimum properties are provided as well.

Description

TECHNICAL FIELD

This invention relates generally to pulmonary drug delivery, and more particularly relates to particulate formulations for the pulmonary administration of an antifungal agent such as amphotericin B. The invention has utility in the fields of drug delivery, pharmaceutical formulation, and medicine.

BACKGROUND

Pulmonary fungal infections, such as invasive filamentous pulmonary fungal infection (IFPFI), are major causes of morbidity and mortality in immunocompromised patients. The immune system of an individual may be compromised by some diseases, such as human immunodeficiency acquired immunodeficiency syndrome (AIDS) and systemic lupus erythematosus (SLE), and/or may be deliberately compromised by immunosuppressive therapy. Immunosuppressive therapy is often administered to patients undergoing cancer treatments and/or patients undergoing a transplant procedure. Immunocompromised patients have an increased susceptibility to pulmonary fungal infections. Severely immunocompromised patients, e.g., patients with prolonged neutropenia and patients requiring long-term prednisone therapy, are particularly susceptible to pulmonary and/or nasal fungal infection.

The most common pulmonary fungal infection in immunocompromised patients is pulmonary aspergillosis. Aspergillosis is a disease caused by Aspergillus fungal species (Aspergillus spp.), which invades the body primarily through the lungs. Most commonly, aspergillosis is due to infection with Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Aspergillus nidulans, or Aspergillus terreus). Fungal infections of the lung which are caused by Aspergillus include, for example, fungal pneumonia and allergic bronchopulmonary aspergillosis. Other filamentous and dimorphic fungi can lead to pulmonary infections as well. These additional mycotic pathogens are usually endemic and include, for example, blastomycosis, disseminated candidiasis, coccidioidomycosis, paracoccidioidomycosis, cryptococcosis, histoplasmosis, mucormycosis, and sporotrichosis, pseudallescheriasis, and pneumocsystis carinii. Though typically not affecting the pulmonary system, infections caused by Candida spp., which are usually systemic and most often result from infections via an indwelling device or IV catheter, wound, or a contaminated solid organ transplant, account for 50 to 67% of total fungal infections in immunocompromised patients.

Amphotericin B is the only approved fungicidal compound currently used to treat aspergillosis and is generally delivered intravenously. Amphotericin B is an amphoteric polyene macrolide obtained from a strain of Streptomyces nodosus. In its commercial form, amphotericin B is present in both amorphous and crystalline forms. Amphotericin B formulated with sodium desoxycholate was the first parental amphotericin B preparation to be marketed. Systemic intravenous therapies are constrained by dose-dependent toxicities, such as renal toxicity and hepatotoxicity, which hamper the effectiveness of the treatment and lessen the desirability of prophylactic use of amphotericin B. Even with the approved therapy, aspergillosis incidence is rising and estimated to cause mortality in more than 50% of those infected who receive treatment.

There are numerous additional drawbacks associated with prior formulations and methods for administration of amphotericin B to treat pulmonary infections. For instance, prior efforts to prepare amphotericin B formulations for pulmonary delivery have resulted in formulations exhibiting inadequate delivery efficiency, particularly with respect to delivery to the lung per se. That is, a substantial fraction of the drug was delivered systemically rather than locally, as is desirable in the treatment of a lung infection. Shelf life has also been problematic, as has the dependence of lung deposition on peak inspiratory flow rate.

There remains a need in the art for a safe and effective method and formulation for administering amphotericin B and other antifungal agents, particularly polyene antifungal agents, to the lungs. Ideally, systemic delivery should be minimized while delivery to the affected tissues of the lung should be maximized, and there should not be any significant dependence of the amount of drug delivered to the lungs on inspiratory flow rate. An ideal formulation would also exhibit long-term stability and be administrable using different types of dosage forms and/or delivery devices.

SUMMARY OF THE INVENTION

The present invention is directed to the aforementioned need in the art, and, in one embodiment, provides a pharmaceutical formulation for pulmonary administration, comprising a plurality of particulates having a mass median diameter less than 20 μm, wherein each particulate comprises: (a) a lipid matrix; and (b) at least one particle of an active agent in the lipid matrix, wherein the active agent has an aqueous solubility of less than 1.0 mg/ml and at least 90% of the active agent particles in the formulation have a geometric diameter less than 3 μm.

In another embodiment, the invention provides a method for administering an active agent to the lungs of a patient, comprising activating a dry powder inhaler to emit a dose of a pharmaceutical formulation that comprises a plurality of particulates having a mass median aerodynamic diameter of less than 5 μm and a bulk density of less than 0.5 g/cm³, each particulate comprising a lipid matrix and at least one particle of the active agent in the lipid matrix, wherein the dose is inhaled by the patient and inhalation of the dose by the patient provides a T_max within 15 minutes of inhalation.

In a further embodiment, a method is provided for treating a patient suffering from a fungal infection of the lung, comprising administering an aerosolized formulation of an antifungal agent to the patient in an amount sufficient to maintain a target lung concentration of the antifungal agent that is at least twice the minimum inhibitory concentration of the antifungal agent, for at least one week.

In an additional embodiment, a method is provided for manufacturing a particulate amphotericin B formulation for pulmonary administration, the method comprising:

(a) mixing a phospholipid, amphotericin B particles each having an initial geometric diameter, and a solvent, to form a suspension;

(b) homogenizing the suspension to form solvent-containing particulates in which the geometric diameter of the amphotericin B particles is less than or equal to the initial geometric diameter; and

(c) spray-drying the particulates at a temperature effective to remove the solvent from the microparticles and thereby provide dry formulation particulates of the phospholipid and amphotericin B.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise indicated, the invention is not limited to specific formulations, administration regimens, drug delivery devices, or the like, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an active agent” includes not only a single active agent but also a combination or mixture of two or more different active agents, reference to “a lipid” includes a single phospholipid as well as two or more phospholipids in combination or admixture, and the like.

As used herein, the term “particle” refers to a discrete microparticle of the active agent per se. By contrast, the term “particulate” refers to a discrete unit of the formulation of the invention, and thus includes a lipid matrix containing at least one active agent “particle,” and will typically include at least one additional component as well, e.g., a polyvalent cation. The formulation particulates can assume various shapes and forms (such as hollow and/or porous microstructures) and may include or define voids, pores, defects, interstitial spaces, apertures, and/or perforations, may be spherical, collapsed, deformed, or fractured.

When referring to an active agent, the term encompasses not only the specified molecular entity, but also its pharmaceutically acceptable, pharmacologically active analogs, including, but not limited to, salts, esters, amides, hydrazides, N-alkyl derivatives, N-acyl derivatives, prodrugs, active metabolites, and conjugates. As an example, therefore, the term “amphotericin B” as used herein refers to amphotericin B per se or an analog of amphotericin B as just described.

As used herein, the terms “treating” and “treatment” refer to reduction in severity and/or frequency of symptoms, elimination of symptoms and/or underlying cause, reduction in likelihood of the occurrence of symptoms and/or underlying cause, and/or remediation of damage. Thus, “treating” a patient with an active agent as provided herein includes prevention of a particular condition, disease, or disorder in a susceptible individual as well as treatment of a clinically symptomatic individual.

As used herein, “effective amount” refers to an amount covering both therapeutically effective amounts and prophylactically effective amounts.

As used herein, a “therapeutically effective amount” of an active agent refers to an amount that is effective to achieve a desired therapeutic result. A therapeutically effective amount of a given active agent will typically vary with respect to factors such as the type and severity of the disorder or disease being treated and the age, gender, and weight of the patient. Unless otherwise specified, the term “therapeutically effective amount” includes a “prophylactically effective amount,” i.e., an amount of active agent that is effective to prevent the onset or recurrence of particular condition, disease, or disorder in a susceptible individual.

As used herein, “mass median diameter” or “MMD” refers to the median diameter of a plurality of particles, typically in a polydisperse particle population, i.e., a population of particles in which there is a range of particle sizes. MMD values as reported herein are determined by laser diffraction (Sympatec Helos, Clausthal-Zellerfeld, Germany) unless the context indicates otherwise. The determination typically involves direct addition of powder samples to the feeder funnel of a Sympatec RODOS dry powder dispersion unit. This can be achieved manually or by agitating mechanically from the end of a VIBRI vibratory feeder element. Samples are dispersed to primary particles via application of pressurized air (2 to 3 bar), with vacuum depression (suction) maximized for a given dispersion pressure. Dispersed particles are probed with a 632.8 nm laser beam that intersects the dispersed particles' trajectory at right angles. Laser light scattered from the ensemble of particles is imaged onto a concentric array of photomultiplier detector elements using a reverse-Fourier lens assembly. Scattered light is acquired in time-slices of 5 ms. Particle size distributions are back-calculated from the scattered light spatial/intensity distribution using a proprietary algorithm.

As used herein, the terms “diameter” and “geometric diameter” are used interchangeably to refer to the diameter of a single microparticle (as may be determined by microscopy), which may be an active agent particle or a formulation particulate as those terms are defined above.

As used herein, “mass median aerodynamic diameter” or “MMAD” refers to the median aerodynamic size of a plurality of particles or particulates, typically in a polydisperse population. The “aerodynamic diameter” is the diameter of a unit density sphere having the same settling velocity, generally in air, as a powder and is therefore a useful way to characterize an aerosolized powder or other dispersed particle or particulate formulation in terms of its settling behavior. The aerodynamic diameter encompasses particle or particulate shape, density, and physical size of the particle or particulate. As used herein, MMAD refers to the median of the aerodynamic particle or particulate size distribution of an aerosolized powder as determined by cascade impaction, unless the context indicates otherwise.

As used herein, the term “emitted dose” or “ED” refers to an indication of the delivery of dry powder from an inhaler device after an actuation or dispersion event from a powder unit or reservoir. ED is defined as the ratio of the dose delivered by an inhaler device to the nominal dose (i.e., to the mass of powder per unit dose placed into a suitable inhaler device prior to firing). The ED is an experimentally determined amount, and may be determined using an in vitro system that mimics patient dosing. To determine an ED value, as that term is used herein, a nominal dose of dry powder is placed into a Turbospin® DPI device (PH&T, Italy), described in U.S. Pat. Nos. 4,069,819 and 4,995,385, which are incorporated herein by reference in their entireties. The Turbospin® DPI is actuated, dispersing the powder. The resulting aerosol cloud is then drawn from the device by vacuum (30 L/min) for 2.5 seconds after actuation, at which point it is captured on a tared glass fiber filter (Gelman, 47 mm diameter) attached to the device mouthpiece. The amount of powder that reaches the filter constitutes the delivered dose. For example, for a capsule containing 5 mg of dry powder, capture of 4 mg of powder on the tared filter would indicate an ED of 80% [=4 mg (delivered dose)/5 mg (nominal dose)].

By a “pharmaceutically acceptable” or “ophthalmologically acceptable” component is meant a component that is not biologically or otherwise undesirable, i.e., the component may be incorporated into a pharmaceutical formulation of the invention and administered to a patient as described herein without causing any significant undesirable biological effects or interacting in a deleterious manner with any of the other components of the formulation in which it is contained. When the term “pharmaceutically acceptable” is used to refer to an excipient, it is generally implied that the component has met the required standards of toxicological and manufacturing testing or that it is included on the Inactive Ingredient Guide prepared by the U.S. Food and Drug Administration.

In a first embodiment, a pharmaceutical formulation for pulmonary administration is provided that comprises a plurality of particulates having a mass median diameter less than 20 μm, preferably less than 10 μm, and optimally less than 5 μm, wherein each particulate comprises: (a) a lipid matrix, preferably composed of a phospholipid; and (b) at least one particle of an active agent in the lipid matrix, the active agent having an aqueous solubility of less than 1.0 mg/ml, wherein at least 90% and preferably at least 95% of the active agent particles in the formulation have a geometric diameter less than 3 μm. The active agent is preferably an antifungal agent, e.g., a polyene antifungal agent such as amphotericin B. A detailed description of this embodiment of the invention is provided in the priority applications hereto, incorporated by reference above, particularly U.S. patent application Ser. No. 10/750,934, filed Dec. 31, 2003.

In another embodiment, a method is provided for treating a patient suffering from a fungal infection of the lung, e,g., pulmonary aspergillosis, the method comprising administering to the patient a therapeutically effective amount of the pharmaceutical formulation described above, wherein the formulation is administered via inhalation. A detailed description of this embodiment of the invention is provided in the priority applications hereto, incorporated by reference above, particularly U.S. patent application Ser. No. 10/750,934, filed Dec. 31, 2003.

In a further embodiment, a method is provided for administering an active agent to the lungs of a patient, comprising activating a dry powder inhaler to emit a dose of a pharmaceutical formulation that comprises a plurality of particulates having a mass median aerodynamic diameter of less than 5 μm and a bulk density of less than 0.5 g/cm³, each particulate comprising a lipid matrix and at least one particle of the active agent in the lipid matrix, wherein the dose is inhaled by the patient and inhalation of the dose by the patient provides a T_max within 15 minutes of inhalation. A detailed description of this embodiment of the invention is provided in the priority applications hereto, incorporated by reference above, particularly U.S. patent application Ser. No. 10/751,342, filed Dec. 31, 2003.

In another embodiment, the invention provides a method for manufacturing a particulate amphotericin B formulation for pulmonary administration, the method comprising:

(a) mixing a phospholipid, amphotericin B particles each having an initial geometric diameter, and a solvent, to form a suspension;

(b) homogenizing the suspension to form solvent-containing particulates in which the geometric diameter of the amphotericin B particles is less than or equal to the initial geometric diameter; and

(c) spray-drying the particulates at a temperature effective to remove the solvent from the microparticles and thereby provide dry formulation particulates of the phospholipid and amphotericin B.

A detailed description of this embodiment of the invention is provided in the priority applications hereto, incorporated by reference above, particularly U.S. patent application Ser. No. 10/750,934, filed Dec. 31, 2003.

It should be noted that the examples and figures of the priority applications are included herein by virtue of those applications standing incorporated by reference into this disclosure. The examples and figures of the priority applications hereto are incorporated by reference herein for all purposes. It should also be noted that certain embodiments of the invention may include combinations of subject matter disclosed in the applications to which the present application claims priority.

Claims

1. A pharmaceutical formulation for pulmonary administration, comprising a plurality of particulates having a mass median diameter less than 20 μm, wherein each particulate comprises: (a) a lipid matrix; and (b) at least one particle of an active agent in the lipid matrix, said active agent having an aqueous solubility of less than 1.0 mg/ml, wherein at least 90% of the active agent particles in the formulation have a geometric diameter less than 3 μm.

2. The pharmaceutical formulation of claim 1 wherein the plurality of particulates has a mass median diameter less than 10 μm.

3. The pharmaceutical formulation of claim 2, wherein the plurality of particulates has a mass median diameter less than 5 μm.

4. The pharmaceutical formulation of claim 1, wherein at least at least 95% of the active agent particles have a geometric diameter less than 3 μm.

5. The pharmaceutical formulation of claim 4, wherein at least 50% of the active agent particles have a geometric diameter between 0.5 μm and 3 μm.

6. The pharmaceutical formulation of claim 5, wherein at least 50% of the active agent particles have a geometric diameter between 1 μm and 3 μm.

7. The pharmaceutical formulation of claim 1, wherein the lipid matrix comprises a phospholipid.

8. The pharmaceutical formulation of claim 7, wherein the phospholipid has a gel to liquid phase transition temperature greater than about 40° C.

9. The pharmaceutical formulation of claim 8, wherein the phospholipid has a gel to liquid phase transition temperature greater than about 60° C.

10. The pharmaceutical formulation of claim 9, wherein the phospholipid has a gel to liquid phase transition temperature greater than about 80° C.

11. The pharmaceutical formulation of claim 7, wherein the phospholipid is a phosphoglyceride.

12. The pharmaceutical formulation of claim 7, wherein the phospholipid is a saturated phospholipid.

13. The pharmaceutical formulation of claim 7, wherein the particulates further include a polyvalent cation effective to increase the gel-to-liquid transition temperature of the phospholipid.

14. The pharmaceutical formulation of claim 1, wherein the particulates further include a polyvalent cation.

15. The pharmaceutical formulation of claim 14, wherein the polyvalent cation is a divalent cation.

16. The pharmaceutical formulation of claim 15, wherein the divalent cation is Ca2+, Mg2+, or Zn2+.

17. The pharmaceutical formulation of claim 1, wherein the active agent is an antifungal agent.

18. The pharmaceutical formulation of claim 17, wherein the antifungal agent is a polyene.

19. The pharmaceutical formulation of claim 18, wherein the antifungal agent is selected from ambruticin, amphotericin B, hamycin, natamycin, nystatin, and pimaricin.

20. The pharmaceutical formulation of claim 19, wherein the antifungal agent is amphotericin B.

21. The pharmaceutical formulation of claim 1, further including particles of the active agent that are not incorporated in the particulates.