Stabilized hydrophobic protein formulations

Abstract: A stable pharmaceutically acceptable formulation containing a pharmaceutically acceptable amount of a protein is disclosed. Also disclosed are associated means and methods for preparing such formulations.

Description: Field of the Invention The present invention is directed to pharmaceutical formulations containing a protein and to methods for making and using such formulations. More particularly, this invention relates to such pharmaceutical formulations having increased stability. The formulations are also very stable during processing. Formulations are provided for immediate, safe, effective therapeutic administration to human subjects. Background of the Invention Granulocyte Colony Stimulating Factor Granulocyte Colony Stimulating Factor (G-CSF), in its natural form comprises two forms: a protein having 174 amino acids, and a form having three additional amino acids. Both forms have five cysteine residues; four forming two disulfide bonds, and one free. In its natural form G-CSF is a glycoprotein. G-CSF supports the growth of predominantly neutrophil colonies in a colony-forming (CFU-GM) assay, and in the presence of accessory cells, supports the growth of early erythroid (BFU-E) and pluripotential progenitors (CFU-GEMM) (granulocytes, erythrocytes, monocytes, and macrophages). G-CSF is also capable of promoting the differentiation of some myeloid leukemic cell lines (e.g., HL-60, WEHI-3B-D⁺), fresh myeloid leukemic cells, and has been reported to enhance the chemotactic peptide binding on peripheral blood neutrophils. In addition, G-CSF can significantly increase the ability of neutrophils to kill tumor targets in vitro through antibody-dependent cellular cytotoxicity (ADCC). In vivo experiments with recombinant human G-CSF in hamsters indicate a specific action on the neutrophil lineage with increases of three to sixfold in peripheral blood neutrophils. Because of its hydrophobic characteristics, G-CSF is difficult to formulate. Examples of attempts to formulate G-CSF are shown in UK Patent Application GB 2193631. Detergents, such as Tween®-80, have been used to maintain G-CSF in a monomeric form and to minimize particulate formation. G-CSF contains five cysteinyl residues, four of which are involved in intrachain disulfide linkage. The free cysteinyl residue is, in general, inaccessible to modification due to folding of the molecule. At elevated temperatures the molecule "breaths" more rapidly and, on occasion, the cysteinyl residues interacts with each other leading to dimer and multimer formation. This phenomenon is enhanced by the presence of a non-ionic surfactant, e.g., Tween®-80 (polyoxyethylene sorbitan monooleate). In order that G-CSF be provided to health care personnel and patients, it must be prepared as a pharmaceutical composition. Such compositions must maintain activity for appropriate periods of time, must be acceptable in their own right for easy and rapid administration to humans, and must be readily manufacturable. In many cases pharmaceutical formulations are provided in frozen or in lyophilized form. In these cases, the compositions must be thawed or reconstituted prior to use. The frozen or lyophilized forms are often used to maintain biochemical integrity and the bioactivity of the medicinal agent contained in the compositions under a wide variety of storage conditions. Such lyophilized preparations are reconstituted prior to use by the addition of suitable pharmaceutically acceptable diluent(s), such as sterile water for injection or sterile physiological saline solution. Alternatively, the composition can be provided in liquid form appropriate for immediate use. Desirable is a liquid formulation which maintains its activity in long term storage. Prior formulations of certain hydrophobic proteins lose activity due to formation of dimer and higher order aggregates (macro range) during long-term storage. Other chemical changes, such as deamidation and oxidation may also occur upon storage. It is an object of the present invention to prepare stable, aggregate-free formulations containing G-CSF. A further object of the invention is to provide hydrophobic protein formulations with higher G-CSF concentrations. A still further object of the invention is to provide formulations containing G-CSF wherein no component is derived from animals, e.g., natural albumin, thus avoiding possible contamination of the formulation with impurities. Other objects, features and characteristics of the present invention will become more apparent upon consideration of the following description and the appended claims. Summary of the Invention Objects of this invention are accomplished by a pharmaceutically acceptable formulation comprising a pharmaceutically effective amount of a G-CSF and acid, wherein said formulation has pH of from 2.75 to 4.0, and advantageously a low conductivity, i.e. less than about 1000 µmhos/cm. The pH of the formulation is 2.75-4.0, and in a preferred embodiment no buffer is present. The formulation has a purity level which is pharmaceutically acceptable. The formulation is capable of undergoing processing and storage with substantially no dimer or higher order aggregate formation. The invention also comprises a method of stabilizing a formulation comprising the step of combining the G-CSF. with acid, advantageously without the addition of any salt, to make a pharmaceutically acceptable formulation having an acidic pH and advantageously an ionic strength of less than 1000 µmhos/cm. Optionally, a tonicity modifier is added. Description of the Figures Figure 1 shows G-CSF prepared at various pH values and run on a 15% gel after reduction of thiol groups. Figure 2 shows G-CSF prepared at various pH values and run on a 15% non-reducing gel. Detailed Description of the Invention The present invention is based upon the discovery that at acidic pH values a specific pharmaceutically acceptable formulation of G-CSF maintains the activity of the protein, and inhibits undesirable reactions that the protein undergoes during processing, reconstitution, and storage. As used herein, the term "processing" includes filtration and filling into vials. The invention is thus directed to such formulations, and to all associated formulations and to methods for effectively stabilizing such proteins. The term G-CSF as used in this application is intended to cover substitution, deletion and insertion of amino acid variants, or post translational modifications. Various forms of G-CSF and methods of production are disclosed in WO 8701132 and US-A-5104651. The formulation of one embodiment of the subject invention comprises: a) a pharmaceutically acceptable amount of a G-CSF stable at acidic pH; and b) acid, wherein said formulation has pH of from 2.75 to 4.0, advantageously no buffer, and advantageously a conductivity of less than 1000 µmhos/cm. In a preferred embodiment, the G-CSF formulation of the subject invention comprises: a) G-CSF at up to 2 mg/ml; and b) hydrochloric acid; and c) mannitol as a tonicity modifier, wherein the pH is 3.2-3.3 and the conductivity of the formulation is less than 500 µmhos/cm. In the composition of the subject invention, high concentrations of G-CSF (e.g. 1-5 mg/ml) are achievable. The subject formulation eliminates the need for Tween®-80. A low conductivity is very advantageous in the subject invention. The pH of the subject formulation is advantageously low. In general, the formulations of the subject invention may contain other components in amounts preferably not detracting from the preparation of stable forms and in amounts suitable for effective, safe pharmaceutical administration. pH ranges for the preparation of the formulations hereof are from 2.75 to 4, advantageously 3.0 to 3.7, most advantageously 3.2 to 3.3. The formulation pH should be less than 4 to reduce aggregate formation. pH values are above 2.75 since values below 2.75 result in substantial peptide bond cleavage. If necessary, the pH is adjusted with acid such as dilute hydrochloric, nitric, phosphoric, or sulfuric acid solutions. In one embodiment, the total acid content is low, i.e. less than about 5 mM to keep the conductivity of the formulation low. In a preferred embodiment no salt (compound derived from an acid by replacing hydrogen with a metal) other than that which is a trace residual by-product of the purification process, is present in the formulation (this embodiment is referred to herein as having no salt). In a preferred embodiment, no buffer is present other than the protein of interest itself and trace residual by-product of the purification process (this embodiment is referred to herein as having no buffer). The preferred buffer when a buffer is used, is a carboxylic acid buffer. Alternatively, citric, lactic or tartaric acid buffer is used at about 1 mM. A buffer concentration greater than or equal to 0 and less than 2 mM is preferred, most advantageously 1 mM. The buffer concentration is kept low to keep the conductivity of the formulation low. In this concentration range of buffer, minimal aggregation occurs. The conductivity of the formulations of the subject invention should be less than 1000 µmhos/cm., although at pH values between about 2.75 and 3 the formulation conductivity is optionally higher. Advantageously the conductivity is less than 700 µmhos/cm, and most advantageously less than 500 µmhos/cm. In a preferred embodiment the conductivity is less than 200 µmhos/cm. The conductivity is adjusted by methods such as diafiltration. Advantageously, formulations of the subject invention are isotonic with the blood of the recipient. A formulation containing about 4-6% (w/v), advantageously 5% (w/v), mannitol as a non-ionic tonicity modifier results in isotonic solution suitable for intravenous injection. The tonicity modifier also acts to stabilize the formulation. As an alternative to mannitol, other sugars or sugar alcohols are used, such as sucrose, maltose, fructose, lactose and the like. The formulation of the subject invention may optionally include one of several types of non-ionic surfactants, such as Tween® 80. In a preferred embodiment no surfactant is present in the formulation. Also comprehended by the invention are formulations comprising pharmaceutically effective amounts of G-CSF together with suitable diluents, adjuvants and/or carriers. Other pharmaceutically acceptable excipients well known to those skilled in the art may also form a part of the subject compositions. These include, for example, various bulking agents, additional buffering agents, chelating agents, antioxidants, preservatives, cosolvents, and the like; specific examples of these could include, trimethylamine salts ("Tris buffer"), and EDTA. In one embodiment, more than one type of protein, e.g. IL-3 and G-CSF, are included in the formulation. In another embodiment, no proteins other than the G-CSF are part of the formulation. A "pharmaceutically effective amount" refers to that amount which provides therapeutic effect in various administration regimens. Such amounts are readily determined by those skilled in the art. The amount of active ingredient will depend upon the severity of the condition being treated, the route of administration, etc. The compositions hereof may be prepared containing amounts of G-CSF of at least about 0.1 mg/ml, upwards of about 5 mg/ml, preferably from about 0.5 mg/ml to about 2 mg/ml. For use of these compositions in administration to human patients suffering from chronic neutropenia, for example, these compositions may contain from about 0.5 mg/ml to about 4 mg/ml, corresponding to the currently contemplated dosage rate for such treatment. The formulations are prepared in general by combining the components using generally available pharmaceutical combining techniques, known per se. A particular method for preparing a pharmaceutical formulation hereof comprises employing G-CSF purified according to any standard protein purification scheme. EXPERIMENTAL A. Formulation preparation The pH of G-CSF solution at about 5 mg/ml is adjusted to 3.25 ± 0.1 with 0.5 N hydrochloric acid and this solution is diafiltered against water for injection adjusted to pH 3.25 with hydrochloric acid (about 0.56 mM HCl). Diafiltration is continued until the conductivity of the permeate is less than 760 µmhos/cm. This solution is combined with 20% mannitol, and water for injection to obtain a final concentration of 1 mg G-CSF/ml and 5% (w/v) mannitol. If necessary, the pH is adjusted to 3.25 with hydrochloric acid or sodium hydroxide solutions. The solution is then passed through a 0.2 µm filter. B. Analytical Methods The analytical methods used are described in the following articles: SDS-PAGE: Lammli, U.K. Nature 227 , 680-685(1970) HP-SEC: Watson, E. & Kenney, W. J. Chromatog. 436 , 289-298 (1988) Results Figure 1 shows a 15% SDS polyacrylamide gel after reduction of protein thiol groups. The formulations of samples A-H were stored for 2 weeks at 52°C. The G-CSF was formulated at 1 mg/ml with 5% (w/v) mannitol. Sample pH A pH 4.2 B pH 3.5 C pH 3.23 D pH 3.0 E pH 2.75 F pH 2.5 G pH 2.0 H pH 3.0 + 10mM NaCl I pH 3.23 stored at 4°C Figure 2 shows a 15% non-reducing SDS polyacrylamide gel. Samples were prepared as in the case of the reducing gel (i.e., 2 weeks at 52°C). Note: (1) the amount of aggregate decreasing with decreasing pH: A = pH 4.2 B = pH 3.5 C = pH 3.23; (2) the increasing lower mol. wt. bands due to hydrolysis in E, F, G: E = pH 2.75 F = pH 2.5 G = pH 2.0; (3) the higher ionic strength yielding more aggregate: D = 0 NaCl, pH 3.0 H = 10 mM NaCl, pH 3.0. Percent G-CSF Remaining as Monomer after Incubation for 2 Weeks at 42°C or 52°C Sample pH % monomer 42°C 52°C A 4.2 >99 39.6 B 3.5 >99 93.8 C 3.23 >99 97.6 D 3.0 >99 98.5 E 2.75 >99 98.5 F 2.5 >99 98.3 G 2.0 98.6 87.1 H 3.0 + 10 mM NaCl >99 88.6 The results in Table 1 as determined by HP-SEC (Watson, Kenny J. Chromatog. 436 , 289-298 (1988)), show that the least amount of aggregate formation was in samples C,D, E & F, which corresponds to a pH range of 3.2-2.50. Further, the presence of salt increased the amount of aggregate (compare D to H). Except for A, & G, little change occurred with incubation at 42°. Examining the results of Figures 1 and 2 and Table 1 together, the most advantageous formulation pH values were those of samples C, D and E, i.e. about pH 2.75-3.23.

Claims: A stabilized pharmaceutically acceptable formulation comprising: a pharmaceutically acceptable amount of a G-CSF stable at acidic pH; and acid wherein said formulation has a pH of 2.75 to 4.0. A formulation according to claim 1 wherein said formulation has a pH of 3.0-3.7 and a conductivity of less than 1000 µmhos/cm. A formulation as in Claim 2 having a pH of 3.2-3.3. A formulation as in Claim 1, 2 or 3 wherein the acid is hydrochloric acid. A formulation as in any one of Claims 1 to 4 further comprising a pharmaceutically acceptable tonicity modifier. A formulation as in Claim 5 wherein the tonicity modifier is mannitol. A formulation as in Claim 6 wherein the mannitol is about 5% (w/v) of the formulation. A formulation as in any one of the preceding Claims additionally comprising a pharmaceutically diluent, adjuvant or carrier. A formulation as in any one of the preceding Claims additionally comprising a nonionic surfactant. A formulation as in any one of the preceding Claims further comprising a buffer. A formulation as in Claim 1 wherein said G-CSF is present at a concentration of 0.5-2 mg/ml, and wherein said formulation has a pH of 3.2-3.3 and a conductivity of less than 200 µmhos/cm. A method of stabilizing a formulation of G-CSF stable at acidic pH comprising the step of combining a pharmaceutically acceptable amount of said G-CSF with acid; wherein said formulation has a pH of 3.0-3.7 , a conductivity of less than 1000 µmhos/cm, and is pharmaceutically acceptable. A method as in Claim 12 wherein said combining step also includes adding a pharmaceutically acceptable tonicity modifier. A method as in Claim 12 or 13 wherein said combining step includes adding hydrochloric acid. A method as in Claim 12, 13 or 14 wherein said formulation has a pH of 3.2-3.3. A method as in any one of Claims 12 to 15 wherein said combining step does not include adding salt. A method as in Claim 13 wherein said tonicity modifier is mannitol. A method as in Claim 17 wherein the mannitol is about 5% (w/v) of the formulation. A formulation according to claim 1, wherein said formulation has no buffer. A formulation as in Claim 19 further comprising a pharmaceutically acceptable tonicity modifer. A formulation as in Claim 19 or 20 having no surfactant present. A formulation as in Claims 19, 20 or 21 having a conductivity of less than 1000 µmhos/cm.

Inventors: BOONE THOMAS C, KENNEY WILLIAM C, BOONE, THOMAS C., KENNEY, WILLIAM C.
Applicants: AMGEN INC, AMGEN INC.
Application year: 1989
Main classification: A61K37
IPC codes: A61K47, A61K9, A61K38