HK1020319B - Dispersible macromolecule compositions and methods for their preparation and use - Google Patents

Description

Dispersible macromolecular composition, preparation method and application thereof

Background of the invention

1. Field of the invention

The present invention relates generally to macromolecular compositions and methods for their preparation and use. In particular, the present invention relates to a process for preparing macromolecular compositions by spray drying under controlled conditions which maintains the purity of the protein and gives good powder dispersibility and other desirable characteristics.

For many years, certain drugs have been sold in compositions suitable for forming dispersions of the drug for oral inhalation (pulmonary delivery) to treat various conditions in humans. Such pulmonary delivery of pharmaceutical compositions is designed to be administered by inhalation of a drug dispersion by the patient so that the active agent in the dispersion can reach the lungs. It has been found that certain drugs delivered through the lungs are readily absorbed through the alveolar region directly into the blood circulation. Macromolecules (proteins, polypeptides, high molecular weight polysaccharides, and nucleic acids) that are difficult to administer by other routes of administration are particularly dependent on pulmonary administration. Such transpulmonary delivery is effective for both systemic and local delivery for the treatment of pulmonary diseases.

Pulmonary drug delivery itself can be achieved in different ways, including the use of liquid nebulizers, aerosol-based metered dose inhalers (MDI's), and dry powder dispensing devices. Aerosol-based MDI's are increasingly losing their enjoyment due to the reliance on chlorofluorocarbons (CFC's), which are being banned because of their negative impact on the ozone layer. Dry powder dispensing devices that do not rely on CFC aerosol technology use drugs of administration that can be formulated as dry powders. Many other unstable macromolecules can be stably stored by lyophilization or spray drying to a powder, or in combination with other stable powder carriers.

However, the delivery efficacy of dry powder pharmaceutical compositions presents certain problems. The dosage of many pharmaceutical compositions is often critical, so it is desirable that dry powder delivery systems be capable of accurately, precisely and reliably delivering the desired amount of drug. In addition, many pharmaceutical compositions are very expensive. Thus, there is a stringent requirement for the ability to effectively formulate, process, package and administer dry powders with minimal drug loss. While it is well known that natural macromolecules have permeability in the lungs, the inefficient macromolecule production process coupled with inefficient macromolecule delivery limits the commercialization of dry macromolecule powders for pulmonary delivery.

One particularly promising form of pulmonary delivery of dry powder drugs is the use of hand-held devices having hand pumps for providing a source of pressurized gas. The pressurized gas is abruptly released through a powder dispersion device, such as a venturi nozzle, so that the dispersed powder can be inhaled by the patient for use. Despite the many advantages, there are a number of problems with such hand held devices. The particles to be administered are generally less than 5 μm in size, making handling and dispersion of the powder more difficult than with larger particles. The volume of pressurized gas available to hand-driven pumps is relatively small, further exacerbating the problem. In particular, venturi dispersion devices are not suitable for difficult to disperse powders, since the gas available to the hand pump is only of small volume. Another requirement for hand held and other powder delivery devices is efficiency. The high efficiency of the device with optimal particle size distribution for pulmonary delivery of the drug during administration of the drug to the patient is a major factor in the survival of the product on the market. Conventional techniques for administering pharmaceutical agents do not achieve the efficiency of administration required by the market. The ability to achieve both adequate dispersion and small dispersion volumes is a significant technical challenge, requiring that each unit dose of the powdered composition be easily and reliably dispersed.

Spray drying is a chemical processing unit operation conventionally used to produce dry solid particles from a variety of liquid and slurry starting materials. The use of spray drying for the formulation of dry powder drugs is known, but is generally limited to small molecules and other stable drugs that are less sensitive to thermal degradation and other harsh processing conditions. The use of spray drying to prepare biomacromolecule compositions, including proteins, polypeptides, macromolecular polysaccharides and nucleic acids, is problematic because these macromolecules are often unstable and degrade when subjected to high temperatures and other spray drying processing conditions. Excessive degradation of macromolecules may result in a pharmaceutical formulation lacking the necessary purity. The particle size and particle size distribution of the compositions produced by spray drying are also difficult to control. For pulmonary administration, it is critical that the mean particle size be maintained below 5 μm, preferably in the range of 0.4 to 5 μm, and that the amount of particles outside the target size range contained in the composition be minimized. Preferably, at least 90% by weight of the powder has a particle size in the range of 0.1-7 μm. More preferably, at least 95% by weight have a particle size in the range of 0.4 to 5 μm. Furthermore, the desired low moisture content required for physical and chemical stability of the final granular product can sometimes be difficult to achieve, especially in an economical manner. Finally, and perhaps most importantly, it is difficult to produce the small particles necessary for pulmonary delivery in an efficient manner. For high-priced macromolecular drugs, the collection rate (i.e., the amount of particulate drug recovered from the process in a usable form) should be above 80%, preferably above 90%, and most preferably above 95% wt. Although spray drying has been used to prepare powders of macromolecules in laboratory scale equipment as described below, there is no commercially available spray dryer designed for the production of particles in the pulmonary delivery size range. The process for aerosolization, drying the powder and collection must be improved in order to economically produce protein powders with the desired product characteristics for pulmonary delivery, in sufficient yield and with commercially acceptable production rates (over 30 g/hr).

Accordingly, it would be desirable to provide improved methods of spray drying macromolecules for use in pulmonary and other drug delivery applications. In particular, it would be desirable to provide improved processing methods and compositions that can compensate for at least some of the above-mentioned deficiencies.

2. Description of the background Art

US5,260,306, 4,590,206, GB 2105189 and EP 072046 describe methods of spray drying nedocromil sodium to form small particles, preferably 2-15 μm, for pulmonary delivery. US patent 5,376,386 describes a process for the preparation of a particulate polysaccharide carrier for pulmonary drug delivery, wherein the carrier comprises particles having a particle size of 5 to 1000 μm and a roughness of less than 1.75. Mumenthaler et al (1994) describe recombinant human growth hormone and recombinant tissue-type plasminogen kinase in pharm. Res.11: 12. This study showed that the protein was degraded during the spray-drying process and therefore it was not possible to maintain sufficient activity for treatment. WO 95/23613 describes the preparation of inhalation powders of DNase by spray drying using laboratory equipment. WO 91/16882 describes a method of spray drying proteins and other drugs in a liposome carrier.

The following applications, assigned to the applicant of the present application, respectively describe the possibility of preparing dry powders of biological macromolecules using spray drying: application 08/423,515 filed on 14.4.1995; application 08/383,475, which is a partially-filed continuation-in-part application 08/207,472 filed on 3, 7, 1994; application 08/472,563 filed on 14.4.1995, which is a continuation-in-part of the now-abandoned 08/417,507 filed on 4.4.1995, which is a continuation-in-part of the now-abandoned 08/044,358 filed on 7.4.1993; application 08/232,849 filed on 25/4/1994 which is a continuation of 07/953,397 which has now been abandoned. WO94/07514 claiming priority from 07/953,397. WO95/24183 claiming priority from 08/207,472 and 08/383,475.

Summary of the invention

In accordance with the present invention, there are provided pharmaceutical compositions having improved characteristics by a method of spray drying biological macromolecules that addresses at least some of the above-mentioned and related deficiencies in previous spray drying processes. The method of the invention comprises providing a solution, slurry, suspension or the like, typically an aqueous solution in water, of the macromolecule and optionally other excipients at a predetermined concentration in a liquid medium. The macromolecules and optional compatible adjuvants such as sugars, buffers, salts and other proteins are formulated in solution to provide a therapeutically effective dosage, prevent degradation during drying, increase dispersibility of the powder, and achieve acceptable physical and chemical stability of the powder at room temperature. The liquid medium is atomised under selected conditions which are capable of forming droplets having an average particle size at or below a predetermined value, and then dried under selected conditions which are capable of forming particles of the formulation having a moisture content below a predetermined threshold level. The dried granules are collected and packaged in a form suitable for use, typically in a unit dose receptacle. The conditions of atomization and drying are preferably selected so that the particles can be dried to below the target moisture content by a single step of drying and to produce particles in the desired size range without further separation (i.e. size classification) of the particles prior to packaging.

In a first preferred aspect of the process of the invention, the total solids content of the liquid medium (including macromolecules and adjuvants) is less than 10%, typically between 0.5% and 10% wt. Preferred concentrations range from about 1% wt to 5% wt, and the liquid medium comprises an aqueous solution. It has been found that controlling the total solids concentration to below 5% significantly enhances the ability to obtain dry particles in the desired size range, i.e. below 5 μm, preferably in the range of 0.4 μm to 5 μm.

In a second preferred aspect of the process of the invention, the solution is atomised to produce droplets having an average droplet size of 11 μm or less than 11 μm. The design and operating conditions of the atomizer are optimized to increase the solids content to the levels described above, making high intensity production practical and economical. Preferably, the atomizing step is carried out by flowing the solution and the atomizing gas stream through a two-stream nozzle at a predetermined gas-to-liquid-to-mass flow ratio, preferably greater than 5. The air pressure upstream of the air holes is maintained above 25 psig. This air pressure is higher than the pressure that causes the speed of sound, i.e. cannot be increased further beyond the speed of sound. It has been found that an increase in the density of the higher pressure atomizing gas reduces the particle size of the resulting droplets.

In another aspect of the process of the invention, the atomized droplets are dried to form particles having a final moisture content of less than 5% wt. Preferably, the particles are dried to this extent by a single step drying operation, typically in a single step spray drying operation in which the droplets flow in parallel with a heating vapour, the vapour having sufficient heat to evaporate the water in the particles to the resulting extent. Typically, the heated gas stream, typically a heated air stream, has an inlet temperature of at least 90 ℃, preferably at least 120 ℃, more preferably at least 135 ℃, further preferably at least 145 ℃, typically 175 ℃, or may be as high as 200 ℃ depending on the macromolecule being dried. At least in part, the inlet temperature of the heated drying vapor is determined based on the instability of the biological macromolecules being treated. In the experimental examples of insulin, the preferred inlet temperature is 140 ℃ to 150 ℃.

To control the final moisture content of the particles produced in spray drying, it is also necessary to control the outlet temperature of the gas. The gas outlet temperature is a function of the inlet temperature, the heat load applied during the product drying step (depending on the inlet temperature of the liquid medium, the amount of water evaporated, etc.), and other factors. Preferably, the gas outlet temperature is maintained above at least 50 ℃, preferably at least 70 ℃, typically from 60 ℃ to 80 ℃.

In another particular aspect of the process of the invention, to enhance powder dispersibility, drying conditions should be selected to control particle morphology. In particular, the drying conditions are selected to obtain a particle roughness of at least 2. Roughness is a measure of surface curl, with higher values indicating greater surface irregularities. Without limiting the scope of the invention in any way, it is presently believed that an increase in surface irregularities, expressed as roughness, can reduce cohesiveness between adjacent particles. This reduction in interplanar interaction in turn improves the dispersibility of the resulting powder. Particle roughness is affected both by the rate of drying of individual droplets and the composition of the dissolved solids.

The droplets begin to dry at a relatively rapid rate, forming a viscous layer of material on the outside of the droplets. As drying continues, the flow of the sticky layer is not as fast as the particles shrink as the solvent evaporates, causing the surface of the particles to wrinkle (wrinkle). The viscosity of the adhesive layer and the glass transition temperature of the material are related by the WLF equation (Williams, Landel, Ferry equation) with reference to K.Alexander & C.J.King, drying technology, Vol.3, No.3, 1985. The temperature gradient in the drying zone should be controlled so that drying of the particles proceeds sufficiently fast to form surface slumping and wrinkles, but not so fast as to break the particles.

In accordance with another particular aspect of the method of the present invention, the dried particles are collected and substantially all of the particles produced in the drying step are separated from the steam. It has been found that proper control of the atomisation and drying conditions produces a particle size range of 0.1 μm to 7 μm for at least 90% of the particulate material, more preferably 0.4 μm to 5 μm for at least 95% of the particles, so that the product of the drying step can be collected and the powder used without the need for size classification prior to packaging. The collected powder may then be used in any conventional manner in a powdered medicament. Typically, a portion of the particulate product is packaged in a suitable receptacle, such as a unit dose receptacle suitable for dry powder inhalers.

In another aspect of the process of the present invention, the powder separation step comprises passing the entire gas stream through a separator, wherein the separator removes from the gas stream all particles having a particle size of less than 1 μm by at least about 90% wt. The separator comprises a high efficiency cyclone which is specifically designed and operated under conditions which make it necessary to efficiently separate the ultrafine particles produced by the process of the invention. Alternatively, the separator may include a filter element, such as a cermet fiber filter, a filter membrane (e.g., a bag filter), or the like.

The method of the invention is useful for the production of dry powders of biological macromolecules which are generally suitable for pharmaceutical use, i.e. for human and veterinary medicine. Biological macromolecules include proteins, polypeptides, oligopeptides, high molecular weight polysaccharides (typically having a molecular weight of about 2 kD), nucleic acids, and the like. Specific biological macromolecules are listed in table 1 below. The method of the present invention is particularly useful for producing dry powders of insulin, a polypeptide hormone having a molecular weight of about 7.5kD or greater. The insulin powder prepared according to the present invention may be derived from animal sources, such as bovine insulin, or may be prepared by recombinant means. Recombinant insulin may have the same amino acid sequence as natural human insulin, or may be modified to some extent while maintaining the desired insulin activity.

The compositions of the present invention comprise a dispersible macromolecular powder intended for pulmonary administration, i.e. inhaled by the patient into the alveolar region of the patient's lungs. The composition comprises particles having an average particle size of less than 10 μm and a roughness of greater than 2, the roughness of the particles preferably being greater than 3, sometimes greater than 5, and generally ranging from 2 to 6, preferably from 3 to 6, sometimes from 4 to 6. Preferably, the particles of the composition have a moisture content of less than 5% wt, more preferably less than 3%, typically less than 2%. Roughness can be measured by BET or other conventional particle surface analysis techniques. Preferably, the composition comprises 90% by weight of particles having a particle size of 0.1 μm to 7 μm, more preferably 95% of particles having a particle size of 0.4 μm to 5 μm. The compositions are often packaged in unit doses, wherein a therapeutically effective amount of the composition is present in a unit dose receptacle, such as a blister pack, gelatin capsule, or the like.

Brief Description of Drawings

FIG. 1 is a block schematic diagram of the basic unit operations of the process of the present invention.

FIG. 2 is a more detailed flow chart illustrating a system suitable for use with the method of the present invention.

FIG. 3 is a schematic view of a preferred atomizing nozzle for a suitable atomizing step in the process of the present invention.

FIG. 4 is another apparatus of the system of FIG. 2 for performing the separation step of the method of the present invention.

Description of the preferred embodiments

The present invention relates to a process for the preparation of a composition comprising an ultrafine dry powder of a biomacromolecule, primarily for use in various therapeutic and clinical pulmonary administrations to a patient, wherein a first main aspect of the invention relates to the control of powder characteristics to enhance the use of the powder for a desired purpose. A second main aspect of the present invention relates to the composition itself as well as to packaged compositions, in particular comprising unit dosage forms of the composition. A third main aspect of the invention relates to the ability of the exemplary method to produce powders at a scale that can warrant the market needs of the drug to be administered.

The term "biomacromolecule" is meant to include biological compounds that are known and have therapeutic and other useful activities. Biomacromolecules generally refer to proteins, polypeptides, oligopeptides, nucleic acids, and relatively high molecular weight polysaccharides, and the methods of the present invention can modify such compounds into ultrafine dry powders having desirable properties, particularly useful powders for pulmonary administration. Some examples of biomacromolecules suitable for preparation as ultrafine dry powders by the process of the present invention are listed in table 1 below. According to the method of the present invention, these biological macromolecules are first dissolved, suspended or dispersed in a volatile liquid medium, then atomized, dried and collected. Preferred biological macromolecules include insulin, interleukin-1 receptor, parathyroid hormone (PTH-34), alpha-1 antitrypsin, calcitonin, low molecular weight heparin, interferon, and nucleic acids. Detailed examples of the preparation of insulin using the process of the present invention are given in the experimental section below.

TABLE 1

Exemplary biomacromolecule drugs

Medicine	Indications of
		Calcitonin hemoglobin (EPO) factor IX granulocyte colony stimulating factor (G-CSF) granulocyte macrophage colony stimulating factor (GM-CSF) growth hormone heparin (low molecular weight) insulin interferon alpha interferon beta interferon gamma interferon interleukin-2 Luteinizing Hormone Releasing Hormone (LHRH) growth hormone releasing inhibitory factor analog vasopressin analog Follicle Stimulating Hormone (FSH) starch insoluble insulin growth factor insulinotropic hormone releasing factor (GRF)	Osteoporosis prevention of Paget's disease hypercalcemia hemophilia B neutropenia bone marrow graft/graft failure in transplantation of blood clots of dwarf renal failure, asthma blood clots type I and type II diabetes type B and hepatitis C hairy cell leukemia before renal carcinoma of Kaposi's sarcoma multiple sclerosis chronic granulomatosisProstatic cancer endometriosis gastrointestinal cancer diabetes insipidus bedwetting fertility I type diabetes Lou Gehrig disease short stature osteoporosis malnutrition II type diabetes B and hepatitis C

Interleukin-1 receptor antagonist Interleukin-3 Interleukin-4 Interleukin-6 macrophage colony stimulating factor (M-CSF) nerve growth factor Parathyroid hormone growth hormone Release inhibitory factor analog alpha-I thymosin IIb/IIIa inhibitor alpha-I antitrypsin anti-RSV antibody Cystic Fibrosis Transmembrane Regulator (CFTR) Gene deoxyribonuclease (DNase) Bactericide/Permeability increasing protein (BPI) anti-CMV antibody Interleukin-1 receptor antagonist

Rheumatoid arthritis chemotherapy adjuvant immunodeficiency thrombocytopenia mycosis cancer hypercholesterolemia peripheral neuropathy osteoporosis refractory diarrhea type B and hepatitis C unstable angina cystic fibrosis respiratory multivirus cystic fibrosis chronic bronchitis adult respiratory distress syndrome cytomegalovirus asthma

The term "ultrafine dry powder" refers to a powder composition comprising a plurality of discrete, dry particles having the characteristics described below. In particular, the dry particles have an average particle size of 5 μm or less, preferably 0.4 μm to 5 μm, more preferably 0.4 μm to 4 μm, most preferably 0.4 μm to 3 μm. The Mass Mean Diameter (MMD) determined by conventional techniques is taken as the average particle size of the powder. Particle powder particle size technique a centrifugal sedimentation particle size analyzer (horiba capa 700) was used. The powder can be readily dispersed in an inhalation device and subsequently inhaled by a patient so that the particles can penetrate into the alveolar region of the lung.

Of particular importance to the present invention, the ultrafine dry particulate compositions produced by the present method have a particle size distribution such that they can target the alveolar region of the lung for pulmonary administration of systemically active proteins. Such compositions are advantageously incorporated into unit doses and other forms without further size classification. In general, the ultrafine dry powders have a particle size distribution in which at least 90% by weight of the powder comprises particles having a mean particle size in the range of from 0.1 μm to 7 μm, preferably at least 95% by weight of the powder is in the range of from 0.4 μm to 5 μm. Furthermore, it is desirable to avoid an excess of particles having a particle size distribution with a very small average diameter, i.e. below 0.4 μm.

In contrast, powders of known therapeutic compounds for the treatment of asthma and chronic bronchitis by inhalation require administration more centrally in the airways (i.e. not to the alveolar region). These powders can produce aerosols having a significantly larger particle size distribution, the particles of which have an average diameter of from 3 to 10 μm. Powders of this size are easier to collect in a conventional spray dryer for high yields than the optimum particle size for pulmonary administration.

The term "dry" means that the powder particles have a moisture content that allows the powder to be stored at room temperature, physically and chemically stable, and readily dispersed in an inhalation device to form an aerosol. Generally, the moisture content of the granules is less than 10% wt water, typically less than 5% wt, preferably less than 3% wt, more preferably less than 2% wt, and optionally less than about 1% wt or less. The moisture content is typically controlled by the drying conditions, as described in more detail below.

The term "dry" means that the powder particles have a moisture content such that the powder is readily dispersed in the inhalation device to form an aerosol. Typically, the moisture content of the particles is less than 10% wt water, typically less than 5% wt, preferably less than 3% wt, more preferably less than 2% wt, and optionally less than about 1% wt or less. The moisture content is typically controlled by the drying conditions, as described in more detail below. In some cases, however, non-aqueous solutions may be used to disperse the biological macromolecules, in which case the moisture content may approach zero.

The term "therapeutically effective amount" refers to the amount present in the composition required to provide the desired concentration of drug to achieve the desired physiological response in the patient in need of treatment. The therapeutically effective amount of each drug is determined on a case-by-case basis. The term "physiologically effective amount" refers to an amount administered to a patient to achieve a desired palliative or curative effect. Physiologically effective amounts of each drug are specifically defined, and the limits are defined as dose concentrations.

The therapeutically effective amount of active agent in the composition will vary depending on the biological activity of the biological macromolecule used and the amount required in the unit dosage form. Since powders are dispersible, it is strongly preferred to manufacture the powder in unit dose form in a manner that allows easy handling by the formulator and consumer. This generally means that the unit dose of the dry powder composition is about 0.5mg to 15mg of total starting material, preferably about 2mg to 10 mg. Generally, the amount of macromolecule in the composition is from about 0.05% wt to 99.0% wt. Most preferably, from about 0.2% wt to about 97.0% wt of the composition is macromolecular.

Pharmaceutically acceptable carriers may optionally be incorporated into the particles (or as a filler carrier for the particles) to provide stability, dispersibility, consistency and/or swellability, enhancing uniform pulmonary delivery of the composition to a patient in need thereof. The term "pharmaceutically acceptable carrier" refers to a carrier that can be inhaled into the lungs without significant toxicological effects on the lungs. The amount of carrier present is expressed as a numerical value of from about 0.05% w to about 99.95% w, preferably from about 5% w to about 95% w, depending on the activity of the drug employed.

Such a preferred acceptable carrier may be one or a combination of two or more excipients, but is generally substantially free of "penetration enhancers". Permeation enhancers are surface active compounds that promote the penetration of a drug through a mucosal or lining, and are proposed for use in intranasal, intrarectal, and intravaginal pharmaceutical formulations. Examples of penetration enhancers include cholates, such as taurocholate, glycocholate, and deoxycholate; fusidate salts, such as taurolidine dehydrofusidate salts; and biocompatible detergents such as tween, lauryl ether-9, and the like. However, the use of permeation enhancers in formulations for the lung is generally undesirable because epithelial blood carriers in the lung are adversely affected by such surface active compounds. The dry powder compositions of the present invention are readily absorbed in the lung without the use of penetration enhancers.

Types of pharmaceutically acceptable excipients that may be used as carriers in the present invention include stabilizers, such as Human Serum Albumin (HSA), fillers, such as carbohydrates, amino acids, and polypeptides; a pH adjusting or buffering agent; salts such as sodium chloride; and so on. These carriers may be in crystalline or amorphous form, or a mixture of both.

HSA has been found to be a particularly valuable support in that it provides improved dispersibility.

Bulking agents that may be mixed with the powders of the present invention include compatible carbohydrates, polypeptides, amino acids, or mixtures 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, maltodextrin, dextran, and the like; sugar alcohols such as mannitol, xylitol, and the like. Preferred carbohydrates include lactose, trehalose, raffinose, maltodextrins, and mannitol. Suitable polypeptides include aspartame. Amino acids include alanine and glycine, preferably glycine.

Additives for conformational stabilization in spray drying and for improving powder dispersibility may be included as minor components in the compositions of the present invention. 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, preferably sodium citrate.

It has been found that the process of the present invention provides particles which are dispersible and resistant to agglomeration and undesirable compaction during handling and packaging operations. It has been found that a particle characteristic directly related to such improved dispersability and handling is the roughness of the product. It is assumed that for non-porous spherical particles, roughness is the ratio of the specific area (as determined by BET, molecular surface adsorption, or other conventional techniques) to the surface area calculated from the particle size distribution (as determined by centrifugal sedimentation particle size analyzer, Horiba Capa 700) and particle density (as determined by pycnometer). Roughness is a measure of the degree of surface wrinkling and folding if the particles are known to be generally nodular in shape during spray drying. This can be verified by SEM analysis for the powder produced by the present invention. A roughness of 1 indicates that the particle surface is spherical and non-porous. A roughness value greater than 1 indicates that the particle surface is not uniform and has at least some degree of rugosity, with higher roughness values indicating greater degrees of non-uniformity. It is preferred for the powder of the invention to have a roughness of at least 2, more preferably at least 3, typically 2 to 6, preferably 3 to 6, more preferably 4 to 6.

Unit dosage forms for pulmonary administration of dispersible dry powder biomacromolecules include, as described above, unit dosage receptacles comprising dry powder. A sufficient amount of the powder is placed within the appropriate dose receptacle to provide a dose of therapeutic drug to the patient. The dose receptacle is fitted within a suitable inhalation device in which the dry powder composition is aerosolized by dispersion in a gaseous vapour to form an aerosol, the aerosol thus generated then being captured in a chamber having a mouthpiece and subsequently inhaled by a patient in need of treatment connected to the mouthpiece. Such dose receptacles include any container known in the art for sealing compositions, such as gelatin capsules and plastic capsules, which have removable portions and allow vapor of a gas (e.g., air) to enter the container directly to disperse the dry powder composition. Examples of such containers are found in US patent 4,227,522 to 1980.10.14; 1980.3.11 authorized 4,192,309; and 1978.8.8 entitled 4,105,027. Suitable containers also include those used in connection with Glaxo's Venturi Rotohaler brand powder inhalers or Fison's Spinhaler brand powder inhalers. Another suitable unit dose container that provides an excellent moisture carrier is made from a plastic laminate of aluminum foil. The drug-based powder is filled by weight or volume into the depressions of the formable foil and sealed with a cover foil plastic laminate. Such containers for use in powder inhalation devices are all described in US patent 4,778,054 and are used by Glaxo's Diskhaler  (US patents 4,627,432; 4,811,731 and 5,035,237). Preferred dry powder inhalers are those described in US patent serial applications 08/309,691 and 08/487,184 filed by the applicant of the present invention. The latter application is disclosed in WO 96/09085.

Referring now to FIG. 1, the method of preparing a dry, biopolydisperse powder according to the invention includes an atomization operation 10 for producing droplets of a liquid medium which are dried by a drying operation 20. The droplets are dried to the form of discrete particles to form a dry powder composition, which is then collected by a separation operation 30. Each step of these unit operations will be described in detail below.

The atomization operation 10 may employ any conventional form of atomizer that increases the surface area of the starting material. This requires that the surface energy of the liquid, its measure, increases directly proportional to the increase in area, which in turn is inversely proportional to the square of the droplet diameter. The source of this energy increase depends on the type of atomizer used. Any atomizer (centrifuge, sonic, pressure, dual stream) capable of producing particles having a mass mean diameter of less than about 11 μm may be used. The present invention preferably employs a dual flow atomizer in which the liquid medium and the high pressure gas vapor are delivered in parallel through a nozzle. It is particularly preferred to use a two-stream atomizing nozzle capable of producing particles having an average diameter of less than 10 μm, as will be described in more detail below.

The atomizing gas is typically air that has been filtered or the like to remove ash particles and other contaminants. Or other gases such as nitrogen may be used. The atomizing gas delivered through the atomizing nozzle is pressurized, typically to about 25psig, preferably above 50 psig. Although the velocity of the atomizing gas is generally limited to sonic velocity, the higher the pressure delivered, the more dense the atomizing gas. It has been found that an increase in gas density reduces the size of the droplets formed in the atomization operation. Conversely, the smaller the droplet size, the smaller the resulting particle size. The atomization conditions, including atomization gas flow rate, atomization gas pressure, liquid flow rate, etc., are controlled to obtain droplets having an average diameter of less than 11 μm, as determined by a doppler phase velocity meter. In determining the preferred atomizer design and operating conditions, the particle size distribution of the droplets was determined using an Aerometric's doppler phase particle size analyzer. The droplet size distribution can also be calculated from the measured dry particle size distribution (Horiba Capa 700) and particle density. The results of the two methods were in good agreement with each other. Preferably, the atomized droplets have an average diameter of 5 μm to 11 μm, more preferably 6 μm to 8 μm. The ratio of gas to liquid to mass flows is preferably maintained at greater than 5, more preferably 8 to 10. Controlling the gas-liquid mass ratio within these ranges is particularly important for controlling the droplet size of the particles.

Previously, conventional atomization equipment for spray dryers was generally considered unsuitable for producing very fine droplets (> 11 μm) as used in the present invention. See, for example, Handbook of Spray Drying, 4the, Wiley & Sons 1985. However, it has been found that operating a dual flow nozzle under the above-mentioned condition parameters can convincingly obtain spray droplets having the desired size range.

The liquid medium may be a solution, suspension or dispersion of the biological macromolecule in a suitable liquid carrier. Preferably, the biomacromolecule is present in a liquid solvent and a pharmaceutically acceptable liquid carrier as a solution, and the liquid carrier is water. Other liquid solvents, such as organic liquids, ethanol, and the like, may also be used. A wide range of concentrations of dissolved solids (including macromolecules and other carriers, excipients, etc. that may be present in the final dried particle) can be included, typically from 0.1% wt to 10% wt. It is generally desirable to include a maximum concentration of solids that will produce particles in the inhalation size range and have the desired dispersion characteristics, typically a solids concentration of 0.5% to 10%, preferably 1.0% to 5%. A liquid medium containing a relatively low concentration of biological macromolecules will result in dried particles of relatively small particle size, as described in more detail below.

A drying operation 20 follows to evaporate liquid from the droplets obtained from the atomizing operation 10. Generally, drying requires the introduction of energy into the droplets, typically by mixing the droplets with a hot gas that causes evaporation of the moisture or gaseous liquid medium. Preferably, the mixing is carried out in a spray dryer or equivalent drying chamber into which hot gas vapor is introduced. Preferably, the hot gas vapor and atomized liquid flow in parallel, but countercurrent, cross-flow, or other flow patterns may also be used.

The drying operation is controlled so as to provide dried particles having the above-specified characteristics, such as a roughness of greater than 2. A roughness of more than 2 can be obtained by controlling the drying rate so that a sticky layer of material is formed quickly outside the droplets. Thereafter, the drying rate should be rapid enough that moisture is removed through the outer layer of material, causing the outer layer to collapse and wrinkle, resulting in an extremely irregular outer surface. But should not dry so quickly as to break the outer layer of material. The drying rate can be controlled according to a number of variables, including the droplet size distribution, the inlet temperature of the gas vapor, the outlet temperature of the gas vapor, the inlet temperature of the liquid droplets, and the manner in which the atomized spray and the hot gas are mixed. Preferably, the drying gas vapour has an inlet temperature of at least 90 ℃, more preferably within the aforementioned range. The outlet temperature is generally at least about 70 deg.C, preferably within the aforementioned ranges. The drying gas is typically air that has been filtered or otherwise treated to remove soot and other contaminants. Air is moved through the system using a conventional blower or compressor.

The separation operation 30 is chosen so as to collect the ultrafine particles obtained in the drying operation 20 very efficiently. Conventional separation operations may be used, and in some cases modifications should be made to ensure that submicron particles are collected. In exemplary embodiments, separation is achieved using a filter media, such as a membrane media (filter bag), a sintered fiber filter, and the like. Alternatively, it is often preferred to use a cyclone to achieve separation, but it is often desirable to achieve separation by high energy separation to ensure efficient collection of submicron particles. The separation operation should collect at least 80% of all particles having an average particle size greater than 1 μm, preferably a collection rate of 85% or more, more preferably 90% or more, more preferably 95% or more.

In some cases, very fine particles, such as 0.1 μm, can be separated from the final collected particles using a cyclone. The parameters of the cyclonic separation operation may be selected so as to achieve an approximate cut-off in which particles above 0.1 μm are collected whilst particles below 0.1 μm are carried out into the upper exhaust. The presence of particles below 0.1 μm in the pulmonary drug powder is undesirable because these particles are generally not deposited in the alveolar region of the lung, but rather are exhaled.

A particular advantage of the process of the present invention is that the particles produced in the drying operation and collected in the separation operation can be used for encapsulation in the desired pharmaceutical packaging without the need for further separation or classification of the particles into the desired particle size range. This effect is a combination of aerosolization and drying conditions that produce a dry powder composition comprising individual particles having a size within the desired range for pulmonary administration. Thus, the separation operation 30 only requires separation of particles from the drying gas vapour (with an optional cut-off of 0.40 μm), wherein the separation achieves as high an efficiency as possible since substantially all of the collected material is suitable for use in a pharmaceutical formulation.

Referring now to fig. 2, an exemplary process flow diagram of the method of the present invention is depicted. The process flow diagram includes a spray dryer 50 which may be a commercially available spray dryer (suitable for the process of the present invention) such as those available from suppliers such as Buchi, Niro, APV, Yamato Chemical Company, Okawara Kakoki Coink. A solution of the above-mentioned liquid medium is fed to the spray dryer (solution feed) through a feed pump 52, a filter 54 and a feed line 56. The feed line is connected to a two-stream atomizing nozzle 57, as described below in connection with fig. 3. Atomizing air is supplied to nozzle 57 from compressor 58, filter 60 and line 62. Drying air is also supplied to the spray dryer 50 through a heater 65 and a filter 66.

From the spray dryer the dried particles are carried by the air stream through a duct 70 to a filter 72. The filter 72 includes a plurality of internal filter elements 74 which may be filter bags or cermet fiber filters such as stainless steel ceramic fiber filters of the type described in Smale, Manufacturing Chemist, P.29, 1992.4. Another type of filter media includes filter bags, filter cloths, and filter cartridges. In all cases, the dry particle laden gas vapor flows into the housing of the separator 72 and the carrier gas passes through the filter element 74. However, the passage of the dry particles will be intercepted by the filter elements and the dry particles will fall by gravity to the bottom of the vessel 72 where they will be collected in the particle collector 76. The collector 76 may be periodically removed and replaced and the dry powder in the collector packaged in unit doses or otherwise. Carrier gas is removed from the top of separator 72 through line 80 and exhaust fan 84. The filter 82 will collect any particles that do not pass through the filter media 74. A source of high pressure air 90 is provided for intermittently generating a pulse of air against the filter media 74. This pulsed air flow in the opposite direction will remove particles sticking to the inlet side of the filter medium to prevent caking. An exemplary system for producing insulin according to the method of the present invention and using the process flow of FIG. 2 is presented in the experimental section below.

Referring now to fig. 3, a two-flow nozzle is illustrated, for example. The flow line 56 includes an inner conduit 100 and an outer conduit 102. The inner conduit 100 carries the solution feed and terminates in a spout 104 having a diameter of 0.015 to 0.075 inches, preferably 0.025 to 0.05 inches, depending on the liquid flow rate. The outer conduit 102 and the inner conduit are coaxially arranged and carry the atomizing gas from the line 62. Duct 62 terminates at a spout 110, spout 110 being substantially coaxial with spout 104 of duct 100. The orifice 110 is generally larger in diameter than the orifice 104 and typically has a cross-sectional area sufficient to produce a desired mass flow rate of air having a desired upstream pressure.

Optionally, a cooling jacket 120 is installed around the spray nozzle (or between the atomizing gas and the solution feed) to maintain the relatively low temperature of the solution feed as it enters the spray dryer 50. The cooling jacket 120 typically carries a temperature and a sufficient amount of cooling water to maintain the solution feed temperature below a temperature at which the biomacromolecules may degrade, typically 4-45 ℃. Cooling is generally only necessary for heat sensitive macromolecules. The higher the solution feed temperature, the lower the viscosity, wherein the lower viscosity may reduce the particle size of the droplets formed by the atomization operation.

Referring now to fig. 4, a collection operation is performed using a cyclone 150 instead of using the filtering separator 72 described in fig. 2. Cyclone 150 receives the dried particles through conduit 70 and carrier gas passes upwardly through line 80 in a similar manner as described in fig. 2. The cyclone 150 needs to be designed and operated in a manner that ensures that the ultra-fine particles produced by the present invention are collected at a very high collection rate. The use of a cyclone will result in some very fine particles being carried out through the upper outlet 80. But in some cases this may not be desirable and further separation may be relied upon to remove particles that are too small to reach the alveolar region of the lung, e.g., particles below 7 μm.

The following examples are given by way of illustration and not by way of limitation. Test examples

Example 1

The structure of the spray drying apparatus is shown in figures 2 and 4. A total of 20 liters of solution was processed on the fly. The solution contained 250g (1.25% wt) of total solids, of which 20% was insulin. The remainder of the solids were mannitol, sodium citrate and glycerol. The solution was fed into the atomizer at 4 ℃ using a Watson Marlow peristaltic pump and silicone tubing at a rate of about 44 ml/min. The actual feed rate was controlled by a PID loop using the spray dryer outlet temperature as a control variable. The atomizer temperature was controlled and a circulating jacket containing 4 ℃ water was circulated around it. The atomizer was air flowed and controlled and measured at 12scfm and 38psig using a needle valve and glass rotameter. Both air and liquid pass through the polishing filter before entering the atomizer (Millipak 60 and Millipore Wafergard II F-40 in line gas filters). The powder was collected in a high efficiency cyclone at 55 inch H₂O is operated at a pressure drop. The flow rate of the drying air was controlled at 100scfm by an AC speed control system on the blower drive motor and measured under the blow of the blower using an orifice plate and a differential pressure transducer. Ratio of time of useExample PID loop and 7.5KW heater control the drying air temperature at 130 deg.C. A total of 225g of powder was recovered in the four-stage separator, with an overall yield of 90%. The powder in each collector was analyzed and is shown in table 2.

TABLE 2

Attribute/method	Unit of	Collector 1	Collector 2	Collector 3	Collector 4
						Water content Karl Fisher	H2Owt％	3.4％	2.8％	2.8％	3.0％
Particle size Horiba Capa700	MMD% < 5 μm	1.80m100	1.4μm100	1.6μm100	1.40μm100
						Cascade Impactor for Aerosol particle size	MMAD	3.3μm68％	ND	ND	ND
Administration dose efficiency inhalation device, gravity	％±SD	83±3	84±5	84±4	81±6
						Surface area	m2/g	11.3	11.7	ND	ND
Roughness of		3.8	3.9	ND	ND

Example 2

A total of 2.4 liters of solution were processed. The solution contained 100g (4.0% wt) total solids of which 20% was insulin. The remainder of the solids were mannitol, sodium citrate and glycerol. The spray dryer used in experimental example 1 was used for this experiment. The solution was fed into the atomizer at a rate that varied with the outlet temperature at 4 ℃ using a Watson Marlow peristaltic pump and silicone tubing. The actual feed rate was controlled by a PID loop using the spray dryer outlet temperature as a control variable. The atomizer temperature control was circulated around a circulating jacket containing 45 ℃ water. The atomizer was air flowed and controlled and measured at 13.8scfm and 70psig using a needle valve and glass rotameter. Both air and liquid pass through the polishing filter before entering the atomizer (Millipak 60 and Millipore Wafergard II F-40 in line gas filters). The flow rate of the drying air was controlled at 95scfm by an AC speed control system on the blower drive motor and measured under the blow of the blower using an orifice plate and differential pressure transducer. The drying air temperature was controlled at 150 ℃ using a time proportional PID loop and a 7.5KW heater. The dry outlet air varied from 70, 75 and 80 ℃. The powder collectors exchange respective temperature set points. The powder in each collector was analyzed and is shown in table 3.

TABLE 3

Attribute/method	Unit of	Collector 1 population air 70 deg.C	Collector 2 population air 75 deg.C	Collector 3 population air 80 deg.C
					Water content Karl Fisher	H2Owt％	2.28	2.02	1.63
Particle size Horiba Capa700	MMD% < 5 μm	2.41μm100	2.69μm82.3	2.43μm100
					Efficiency of dosing	％±SD	71±3	73±3	71±2
Average surface area micrometer Gemini	m2/g±SD	6.76±.19	6±.02	8.07±.12
					Roughness of		3.6	3.9	3.8

Example 3

The spray dryer was reconfigured with a filter bag fitted with a stainless steel ceramic fiber filter element (Fairey Microfiltrex). The device structure is shown in fig. 2.

A total of 8 liters of solution was processed by running. The solution contained 100g (1.25% wt) total solids of which 20% was insulin. The remainder of the solids were mannitol, sodium citrate and glycerol. The solution was fed into the atomizer at a rate of 55ml/min at 4 ℃ using a Watson Marlow peristaltic pump and silicone tubing. The actual feed rate was controlled by a PID loop using the spray dryer outlet temperature as a control variable. The atomizer temperature was controlled and a circulating jacket containing 4 ℃ water was circulated around it. The atomizer was air flowed and controlled and measured at 12scfm and 42psig using a needle valve and glass rotameter. Both air and liquid pass through the polishing filter before entering the atomizer (Millipak 60 and Millipore Wafergard II F-40 in line gas filters). The flow rate of the drying air was controlled at 100scfm by an AC speed control system on the blower drive motor and measured under the blow of the blower using an orifice plate and a differential pressure transducer. The drying air temperature was controlled at 145 ℃ with a niro7.5kw heater. The collection of particles was performed in a modified Pacific Engineering (Anaheim, Calif.) clean room (filter bag or filter) itself. The filter bags are placed in the apparatus and modified to allow for many different filters. Two FaireyMicrofiltrex (Hampshire, UK) cermet fiber filters were used instead of the filter cage and fabric filters to create a system of reverse pulsing of the filter elements (reversing the filter bags with high pressure air) on top of the filter bags to aid recovery. The pulse is activated for less than 1 second every 20 seconds. The pulse pressure was 110 psig. The powder falls to the bottom of the filter bag by gravity and mechanical assistance (vibration). The powder in the collector was analyzed and is shown in table 4.

TABLE 4

Attribute/method	Unit of	Collector
			Water content Karl Fisher	H2Owt％	4.8％
Particle size Horiba Capa700	MMD% < 5 microns% < 1.4 microns% < 1.0 micron	1.34μm100％62％44％
			Dosing efficiency dry powder device, gravity	％±SD	73±2

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims.

Claims (15)

1. A method for preparing a dispersible dry biopolymer powder, said method comprising:

providing a volatile liquid medium comprising a predetermined concentration of a biomacromolecule having a molecular weight greater than 2 KD;

atomizing a liquid medium, wherein the atomization conditions are selected to form droplets having an average particle size below 11 μm;

drying the droplets in a heated gas stream to produce particles having a roughness of at least 2.0 measured as air permeability, a moisture content of less than 10 wt% and a particle size of less than 10 μm.

2. The method of claim 1, wherein the total solids content of the liquid medium is less than 10 wt%.

3. The process of claim 2 wherein the solids content is less than 5 weight percent.

4. The method of claim 1, further comprising collecting the particles.

5. The process of claim 1, wherein 90% by mass of the dispersible powder consists of particles having a diameter of 0.1 μm to 7 μm.

6. The process of claim 1, wherein 90% by mass of the dispersible powder consists of particles having a diameter of 0.4 μm to 5 μm.

7. The method of claim 1, wherein the droplets flow co-currently with the heated gas stream, and wherein the inlet temperature of the gas stream is greater than 90 ℃.

8. The method of claim 7, wherein the inlet temperature is 120-200 ℃.

9. The method of claim 7, wherein the gas stream has an inlet temperature greater than 120 ℃ and an outlet temperature greater than 50 ℃.

10. The method of claim 9, wherein the outlet temperature is 60-80 ℃.

11. The method of claim 4, further comprising encapsulating at least some of the particles in a container after the collecting step, wherein the particles are not size classified prior to encapsulation.

12. The method of claim 11, wherein the particles are packaged in a unit dose container.

13. The method of claim 1, wherein the macromolecule is selected from the group consisting of: calcitonin, hemoglobin, factor IX, granulocyte colony stimulating factor, granulocyte macrophage colony stimulating factor, growth hormone, insulin, alpha interferon, beta interferon, gamma interferon, interleukin-2, Luteinizing Hormone Releasing Hormone (LHRH), growth hormone release inhibiting factor, vasopressin analogs, Follicle Stimulating Hormone (FSH), amylin, ciliary neurotropic factor, growth hormone releasing factor, insulin-like growth factor, insulinotropic hormone, beta interferon, gamma interferon, interleukin-1 receptor antagonists, interleukin-3, interleukin-4, interleukin-6, macrophage colony stimulating factor, nerve growth factor, parathyroid hormone, alpha-I thymosin, IIb/IIIa inhibitors, alpha-I antitrypsin, alpha-I interferon, alpha-I, alpha-, anti-RSV antibodies, deoxyribonuclease (DNase), bactericidal agent/permeability increasing protein (BPI), anti-CMV antibodies, interleukin-1 receptor antagonists.

14. The method of claim 1, wherein the particles have a roughness of 3 to 6 as measured by air permeability.

15. A macromolecular composition produced by the process of any one of claims 1-3 and 5-14.