Title:  Spray drying of macromolecules to produce inhaleable dry powders

United States Patent:  6,582,728

Issued:  June 24, 2003

Inventors:  Platz; Robert M. (Half Moon Bay, CA); Patton; John S. (San Carlos, CA); Foster; Linda (Sunnyvale, CA); Eljamal; Mohammed (San Jose, CA)

Assignee:  Inhale Therapeutic Systems, Inc. (San Carlos, CA)

Appl. No.:  423515

Filed:  April 14, 1995

Abstract

According to the subject invention, dispersible dry powder pharmaceutical-based compositions are provided, including methods for their manufacture and dry powder dispersion devices. A dispersible dry powder pharmaceutical-based composition is one having a moisture content of less than about 10% by weight (%w) water, usually below about 5%w and preferably less than about 3%w; a particle size of about 1.0-5.0 .mu.m mass median diameter (MMD), usually 1.0-4.0 .mu.m MMD, and preferably 1.0-3.0 .mu.m MMD; a delivered dose of about >30%, usually >40%, preferably >50%, and most preferred >60%; and an aerosol particle size distribution of about 1.0-5.0 .mu.m mass median aerodynamic diameter (MMAD), usually 1.5-4.5 .mu.m MMAD, and preferably 1.5-4.0 MMAD. Such composition are of pharmaceutical grade purity.

COMPOSITIONS OF THE INVENTION

One aspect of this invention is a dispersible pharmaceutical-based dry powder composition for pulmonary delivery, the composition comprising a therapeutically effective amount of a pharmaceutical in combination with a pharmaceutically acceptable carrier.

In general, the composition of this invention are suitable for pulmonary delivery because of their dispersibility characteristics. Such compositions were not previously known in the art. In the dry state, the pharmaceutical may be in crystalline or amorphous form. Some examples of pharmaceutical compositions suitable for formulation into dispersible dry powders are listed in Table 1. These include macromolecule and non-macromolecule-based pharmaceuticals, usually macromolecules, with insulin, interleukin-1 receptor, parathyroid hormone (PTH-34), alpha-1 antitrypsin, calcitonin, low molecular weight heparin, heparin, interferon, and nucleic acids being preferred.

A therapeutically effective amount of active pharmaceutical will vary in the composition depending on the biological activity of the drug employed and the amount needed in a unit dosage form. Because the subject compounds are dispersible, it is highly preferred that they be manufactured in a unit dosage form in a manner that allows for ready manipulation by the formulator and by the consumer. This generally means that a unit dosage will be between about 0.5 mg and 15 mg of total material in the dry powder composition, preferably between about 2 mg and 10 mg. Generally, the amount of drug in the composition will vary from about 0.05%w to about 99.0%w. Most preferably the composition will be about 0.2% to about 97.0%w drug.

The amount of the pharmaceutically acceptable carrier is that amount needed to provide the necessary stability, dispersibility, consistency and bulking characteristics to ensure a uniform pulmonary delivery of the composition to a subject in need thereof. Numerically the amount may be from about 0.05%w to about 99.95%w, depending on the activity of the drug being employed. Preferably about 5%w to about 95%w will be used.

The carrier may be one or a combination of two or more pharmaceutical excipients, but will generally be substantially free of any "penetration enhancers." Penetration enhancers are surface active compounds which promote penetration of a drug through a mucosal membrane or lining and are proposed for use in intranasal, intrarectal, and intravaginal drug formulations. Exemplary penetration enhancers include bile salts, e.g., taurocholate, glycocholate, and deoxycholate; fusidates, e.g., taurodehydrofusidate; and biocompatible detergents, e.g., Tweens, Laureth-9, and the like. The use of penetration enhancers in formulations for the lungs, however, is generally undesirable because the epithelial blood barrier in the lung can be adversely affected by such surface active compounds. The dry powder compositions of the present invention are readily absorbed in the lungs without the need to employ penetration enhancers.

The types of pharmaceutical excipients that are useful as carriers in this invention include stabilizers such as human serum albumin (HSA), bulking agents such as carbohydrates, amino acids and polypeptides; pH adjusters or buffers; salts such as sodium chloride; and the like. These carriers may be in a crystalline or amorphous form or may be a mixture of the two.

It has been found that HSA is particularly valuable as a carrier in that it provides improved dispersibility.

Bulking agents that are particularly valuable include compatible carbohydrates, polypeptides, amino acids or combinations thereof. Suitable carbohydrates include monosaccharides such as galactose, D-mannose, sorbose, and the like; disaccharides, such as lactose, trehalose, and the like; cyclodextrins, such as 2-hydroxypropyl-.beta.-cyclodextrin; and polysaccharides, such as raffinose, maltodextrins, dextrans, and the like; alditols, such as mannitol, xylitol, and the like. A preferred group of carbohydrates includes lactose, trehalose, raffinose maltodextrins, and mannitol. Suitable polypeptides include aspartame. Amino acids include alanine and glycine, with glycine being preferred.

Additives, which are minor components of the composition of this invention, may be included for conformational stability during spray drying and for improving dispersibility of the powder. These additives include hydrophobic amino acids such as tryptophan, tyrosine, leucine, phenylalanine, and the like.

Suitable pH adjusters or buffers include organic salts prepared from organic acids and bases, such as sodium citrate, sodium ascorbate, and the like; sodium citrate is preferred.

The unit dosage form, method of treatment, and process of preparation of this invention are described hereafter.

Unit Dosage Form

Another aspect of this invention is a unit dosage form for pulmonary delivery of dispersible dry powder pharmaceutical-based compositions, which dosage form comprises a unit dosage receptacle containing a pharmaceutical-based dry powder composition, which composition comprises a therapeutically effective amount of a pharmaceutical in combination with a pharmaceutically acceptable carrier.

In this aspect of the invention, the composition of this invention (as discussed hereinbefore) is placed within a suitable dosage receptacle in an amount sufficient to provide a subject with drug for a unit dosage treatment. The dosage receptacle is one that fits within a suitable inhalation device to allow for the aerosolization of the dry powder composition by dispersion into a gas stream to form an aerosol and then capturing the aerosol so produced in a chamber having a mouthpiece attached for subsequent inhalation by a subject in need of treatment. Such a dosage receptacle includes any container enclosing the composition known in the art such as gelatin or plastic capsules with a removable portion tat allows a stream of gas (e.g., air) to be directed into the container to disperse the dry powder composition. Such containers are exemplified by those shown in U.S. Pat. Nos. 4,227,522 issued Oct. 14, 1980; 4,192,309 issued Mar. 11, 1980; and 4,105,027 issued Aug. 8, 1978. Suitable containers also include those used in conjunction with Glaxo's Ventolin.RTM. Rotohaler brand powder inhaler or Fison's Spinhaler.RTM. brand powder inhaler. Another suitable unit-dose container which provides a superior moisture barrier is formed from an aluminum foil plastic laminate. The pharmaceutical-based powder is filled by weight or by volume into the depression in the formable foil and hermetically sealed with a covering foil-plastic laminate. Such a container for use with a powder inhalation device is described in U.S. Pat. Nos. 4,778,054 and is used with Glaxo's Diskhaler.RTM. (U.S. Pat. Nos. 4,627,432; 4,811,731; and 5,035,237). All of these references are incorporated herein by reference.

Method of Treating a Disease State

Another aspect of this invention is a method of treating a condition responsive to treatment by a pharmaceutical of interest, which method comprises pulmonarily administering to a subject in need thereof a physiologically effective amount of a dispersible pharmaceutical-based dry powder composition that comprises a therapeutically effective amount of drug in combination with a pharmaceutically acceptable carrier.

Conditions that may be treated by the compositions of the invention are described in Table 1.

The physiologically effective amount needed to treat a particular condition or disease state will depend on the individual, the condition, length of treatment, the regularity of treatment, the type of drug, and other factors, but can be determined by one of ordinary skill in the medicinal arts.

It is presently believed that the effective absorption by a host of dry powder composition according to the present invention results from a rapid dissolution in the ultra-thin (<0.1 .mu.m) fluid layer of the alveolar lining of the lung. The particles of the present invention thus have a mean size which is from 10 to 50 times larger than the lung fluid layer, making it unexpected that the particles are dissolved and systemically absorbed in a rapid manner for either local lung or systemic treatment. An understanding of the precise mechanism, however, it not necessary for practicing the present invention as described herein.

The aerosolized pharmaceutical-based dry powders of this invention are particularly useful in place of parenteral delivery. Thus, the methods and compositions of the present invention will be particularly valuable in chronic treatment protocols where a patient can self-medicate. The patient can achieve a desired dosage by inhaling an appropriate amount of drug, as just described. The efficiency of systemic delivery via the method as just described will typically be in the range from about 15% to 50%.

Method for Aerosolizing the Powder

Still another aspect of this invention is a device and method for aerosolizing a pharmaceutical-based dry powder composition that comprises a therapeutically effective amount of drug in combination with a pharmaceutically acceptable carrier, which method comprises dispersing an amount of the dry powder composition in a gas stream to form an aerosol and capturing the aerosol in a chamber having a mouthpiece for subsequent inhalation by a patient.

A further detailed description of this method is found in pending U.S. Pat. application Ser. Nos.: 07/910,048 and 08/207,472, both of which are incorporated herein by reference.

Preparing the Compositions

Still another aspect of this invention is a method for preparing a dispersible pharmaceutical-based dry powder composition of this invention that comprises spray drying an aqueous mixture of the drug and a pharmaceutically acceptable carrier under conditions to provide a respirable dry powder composition.

Spray drying is a process in which a homogeneous aqueous mixture of drug and the carrier is introduced via a nozzle (e.g., a two fluid nozzle), spinning disc or an equivalent device into a hot gas stream to atomize the solution to form fine droplets. The aqueous mixture may be a solution, suspension, slurry, or the like, but needs to be homogeneous to ensure uniform distribution of the components in the mixture and ultimately the powdered composition. Preferably the aqueous mixture is a solution. The solvent, generally water, rapidly evaporates from the droplets producing a fine dry powder having particles 1 to 5 .mu.m in diameter. Surprisingly, the drug is not degraded when it is exposed to the hot drying gas, and the powders can be prepared having sufficient purity for pharmaceutical use. An acceptable purity is defined as less than 5% degradation products and contaminates, preferably less than 3% and most preferably less than 1%.

The spray drying is done under conditions that result in substantially amorphous powder of homogeneous constitution having a particle size that is respirable, a low moisture content and flow characteristics that allow for ready aerosolization. Preferably the particle size of the resulting powder is such that more than about 98% of the mass is in particles having a diameter of about 10 .mu.m or less with about 90% of the mass being in particles having a diameter less than 5 .mu.m. Alternatively, about 95% of the mass will have particles with a diameter of less than 10 .mu.m with about 80% of the mass of the particles having a diameter of less than 5 .mu.m.

The solutions may then be sprayed dried in conventional spray drying equipment from commercial suppliers, such as Buchi, Niro, Yamato Chemical Co., Okawara Kakoki Co., and the like, resulting in a substantially amorphous particulate product.

For the spraying process, such spraying methods as rotary atomization, pressure atomization and two-fluid atomization can be used. Examples of the devices used in these processes include "Parubisu [phonetic rendering] Mini-Spray GA-32" and "Parubisu Spray Drier DL-41", manufactured by Yamato Chemical Co., or "Spray Drier CL-8," "Spray Drier L-8," "Spray Drier FL-12," "Spray Drier FL-16" or "Spray Drier FL-20," manufactured by Okawara Kakoki Co., can be used for the method of spraying using rotary-disk atomizer.

While no special restrictions are placed on the nozzle of the atomizer used in the process of spraying, it is recommended to use a nozzle which can produce a spray-dry composition with a grain diameter suitable for nasal, pharyngeal or pulmonary administration. For example, nozzle types "1A," "1," "2A," "2," "3" and the like, manufactured by Yamato Chemical Co., can be used for the above-mentioned spray-drier, manufactured by the same company. In addition, disks type "MC-50," "MC-65" or "MC-85," manufactured by Okawara Kakoki Co., can be used as rotary disks of the spray-drier atomizer, manufactured by the same company.

While no particular restrictions are placed on the gas used to dry the sprayed material, it is recommended to use air, nitrogen gas or an inert gas. The temperature of the inlet of the gas used to dry the sprayed materials such that it does not cause heat deactivation of the sprayed material. The range of temperatures may vary between about 50^oC. to about 200^oC., preferably between about 50^oC. and 100^oC. The temperature of the outlet gas used to dry the sprayed material, may vary between about 0^oC. and about 150^o, preferably between 0^oC. and 90^oC., and even more preferably between 0^oC. and 60^oC. The fact that inlet and outlet temperatures above about 55^oC. can be used is surprising in view of the fact that most macromolecule-based drugs deactivate at that temperature, with nearly complete deactivation occurring at about 70^oC.

The dispersible pharmaceutical-based dry powders of the present invention may optionally be combined with pharmaceutical carriers or excipients which are suitable for respiratory and pulmonary administration. Such carriers may serve simply as bulking agents when it is desired to reduce the pharmaceutical concentration in the powder which is being delivered to a patient, but may also serve to enhance the stability of the compositions and to improve the dispersibility of the powder within a powder dispersion device in order to provide more efficient and reproducible delivery of the pharmaceutical and to improve handling characteristics such as flowability and consistency to facilitate manufacturing and powder filling.

Such carrier materials may be combined with the drug prior to spray drying, i.e., by adding the carrier material to the purified bulk solution. In that way, the carrier particles will be formed simultaneously with the drug particles to produce a homogeneous powder. Alternatively, the carriers may be separately prepared in a dry powder form and combined with the dry powder drug by blending. The powder carriers will usually be crystalline (to avoid water absorption), but might in some cases be amorphous or mixtures of crystalline and amorphous. The size of the carrier particles may be selected to improve the flowability of the drug powder, typically being in the range from 25 .mu.m to 100 .mu.m. A preferred carrier material is crystalline lactose having a size in the above-stated range.

Alternatively, dry powder compositions may be prepared by other processes such as lyophilization and jet milling as disclosed in WO 91/16038, the disclosures of which are hereby incorporated by reference.

Claim 1 of 27 Claims

The subject matter claimed is:

1. A method for preparing a dry powder composition for pulmonary administration, said method comprising the following steps performed sequentially:

(a) providing an aqueous solution comprising a pharmaceutically active macromolecule and a pharmaceutically acceptable carrier selected from the group consisting of human serum albumin, carbohydrates, amino acids, polypeptides, buffers, and salts; and

(b) spray drying said aqueous solution from step (a) at a temperature in the range from 50^oC. to 200^oC. to produce a non-liposomal dry powder composition suitable for pulmonary administration comprising a therapeutically effective amount of said pharmaceutically active macromolecule and said pharmaceutically acceptable carrier and having a moisture content below 10% by weight,

wherein said pharmaceutically active macromolecule retains its activity upon spray drying.

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