Spray dried erythropoietin

Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Peptide containing doai

Reexamination Certificate

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Details

C530S350000, C530S380000, C530S340000

Reexamination Certificate

active

06235710

ABSTRACT:

BACKGROUND OF THE INVENTION
Erythropoietin (EPO) is a glycoprotein hormone primarily synthesized in the kidney and is the chief regulator of red blood cell production in the body. Commercially available human EPO is produced via recombinant DNA techniques and is known as recombinant human EPO (rhEPO). rhEPO has a molecular mass of approximately 36,000 Daltons, as determined by SDS-PAGE. The molecular mass of the protein backbone is 18,398 Daltons, which indicates that the entire molecule is heavily glycolsylated. The carbohydrate residues are important for in vivo biologic activity.
Maintaining proteins, such as rhEPO, in their native state in aqueous solution or in solid phase is a major challenge to those working in the field of pharmaceutical formulations. The existence of a protein in its native state depends on protein concentration, temperature and nature of solvent, ionic strength of the buffer, etc. Changes in any of these parameters can affect the stability of a protein in solution or solid phase.
Commercial preparations of rhEPO are presently sold as either dilute aqueous solutions or in a lyophilized form which is used to form a dilute aqueous solution, both of which are administered to the body by injection. The concentration of rhEPO in these preparations is very low and the rhEPO is cleared from the body fairly quickly after administration. In view of this limitation of present preparations, there is a need for concentrated preparations of rhEPO, e.g., those containing higher amounts of rhEPO, which can be used in alternate drug delivery systems. We used spray drying techniques to prepare such preparations.
The spray drying of pharmaceuticals is known in the art. For example, see Broadhead, J. et al., “The Spray Drying of Pharmaceuticals,” in Drug Dev. Ind. Pharm, 18 (11 & 12), 1169-1206 (1992). In addition to small molecule pharmaceuticals, a variety of biological materials have been spray dried and these include: enzymes, sera, plasma, micro-organisms and yeasts. Spray drying is a useful technique because it can convert a liquid pharmaceutical preparation into a fine, dustless or agglomerated powder in a one-step process. The basic technique comprises the following four steps:
a) atomization of the feed solution into a spray;
b) spray-air contact;
c) drying of the spray; and
d) separation of the dried product from the drying air.
Although known in the field of pharmaceuticals, there has not been much use of spray drying for therapeutic proteins, such as rhEPO. One apparent reason for this is the concern that such proteins may be thermally degraded by the high temperatures utilized in the spray drying process. This is especially true of complex glycoproteins, such as rhEPO, which, in addition to their polypeptide backbones, also have complex branched carbohydrate portions that are required for biological activity. The availability of lyophilization as a ready alternative further steered workers in the field away from using spray drying for therapeutic proteins. However, spray drying provides certain advantages over lyophilization in that it is more economical, fast and easy to scale up. Also, spray dried powders are often more amenable to further processing than lyophilized powders.
It is usually impractical to design formulations based merely on the lyophilization of the bulk drug. This is so because many polypeptides are relatively unstable when lyophilized in low concentrations and they can adsorb to product packaging and lose activity. In order to overcome these problems, many lyophilized pharmaceutical compositions rely on the use of solid diluents, cryoprotectants or bulking agents to increase the amount of solid material present during the lyophilization process. As a result the final lyophilized material contains a small percentage (w/w) of active drug mixed with a large percentage of other solid material.
In contrast, the present invention provides a method for producing an rhEPO powder from bulk rhEPO wherein the powder produced is pure or essentially pure rhEPO or has a higher percentage (w/w) of rhEPO than can be prepared using traditional lyophilization techniques.
SUMMARY OF THE INVENTION
The present invention provides a method for preparing stable, spray dried rhEPO and the rhEPO powder produced thereby.
The method of the present invention comprises first providing an aqueous solution of rhEPO having a concentration within the range of about 20 mg/ml to about 100 mg/ml. That solution is then atomized into a spray and the spray is dried with hot air in order to evaporate the water from the spray. The dried rhEPO produced thereby is then separated from the drying air.
The initial aqueous solution may contain, in addition to rhEPO, excipients such as mannitol, glycine and/or a surfactant. The dry rhEPO composition produced by the method of the present invention comprises rhEPO in a concentration within the range of 4.0% to 100% (w/w) and has a residual moisture content within the range of about 3.0% to about 5.0% (w/w). The size of the particles of the composition are within the range of about 2.0 microns to about 6.0 microns.
DETAILED DESCRIPTION OF THE INVENTION
A concentrated rhEPO solution of at least 20 mg/ml was used for spray drying. The concentrated aqueous solution was atomized into fine droplets by pumping it through a nozzle with pressurized air. The droplets then entered a drying chamber and the water was evaporated by the hot drying air flowing co-current with the feed solution. As the water evaporated, solid rhEPO and excipients, if present, separated from the aqueous droplets. The dried rhEPO was carried by the drying air current to a cyclone separator for clarification, i.e., the dried rhEPO was separated from the drying air, and the dried product was collected in the collection vessel attached at the bottom of the cyclone separator. The drying air was then expelled through a fines scrubber into the atmosphere.
As used herein, the phrase “rhEPO” means any protein having all or part of the polypeptide backbone described for rhEPO in U.S. Pat. No. 4,703,008 and which possesses the biological property of causing bone marrow cells to increase production of reticulocytes and red blood cells and to increase hemoglobin synthesis or iron uptake. It is contemplated that biologically active fragments, analogs or chemically synthesized derivatives of EPO may be used in the present invention, rather than rhEPO, provided that such fragments or derivatives retain the biological activity of rhEPO. Certain EPO analogs are described in U.S. Pat. No. 4,703,008. Therefore, use of such biologically active EPO analogs, fragments, or derivatives is considered to be within the scope of the present invention.
The concentrated rhEPO powders produced by the present invention may be used in alternate drug delivery systems to deliver the rhEPO. One such system is a controlled release delivery system that delivers the rhEPO at a predetermined rate for a definite time period in the body. Alternatively, the concentrated rhEPO powders may be reconstituted with water for injection or normal saline to form aqueous solutions suitable for human therapeutic use. The controlled release systems mentioned above are envisioned to include rhEPO placed within a polymeric material, vesicles or a miniature pump, as well as macromolecular conjugates of rhEPO and other polymeric materials. These systems may then be used as subdermal reservoir implants of concentrated rhEPO. Non-limiting examples of these systems include matrices of solid hydrophobic polymers surrounding the rhEPO, such as non-degradable ethylene-vinylacetate copolymers or degradable lactic acid-glycolic acid copolymers. Such hydrophobic polymers may additionally take the form of micro spheres.
The present invention provides stable rhEPO powder. As used herein, “stable” means that the rhEPO maintains its biological activity over time and its structure is maintained in its native state, i.e. it is not oxidized or otherwise degraded into another chemical species. Stability can be substantiated by RIA, Western Blot a

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