CA2259557A1 - Non-aqueous polar aprotic peptide formulations - Google Patents

Abstract

This invention relates to stable non-aqueous polar aprotic formulations of peptide compounds. These stable formulations comprise peptide in non-aqueous polar aprotic solvent. They may be stored at elevated temperatures for long periods of time and are especially useful in implantable delivery devices for long term delivery of drug.

Description

CA 022C,9C,C,7 l998-l2-3l This application claims priority under 35 U.S.C. 119(e) to U.S.
6 Application Serial No. 60/022,699 filed July 3,1996, the disclosure of which is 7 incorporated herein by reference.

g FIELD OF THE INVENTION
This invention relates to stable non-aqueous polar aprotic formulations of peptide compounds and more particularly to formulations of peptide 2 compounds at high concentrations.

5 References:
6 The following references are referred to by numbers in brackets ([ ]) at 7 the relevant portion of the specification.
8 1. Zoladex (goserelin acetate implant), Physician's Desk Reference, 50th 19 Edition, pages 2858-2861 (1996).
20 2. U.S. Patent No. 3,914,412, issued October 21, 1975.
21 3. U.S. Patent No. 4,547,370, issued October 15, 1985.
22 4. U.S. Patent No. 4,661,472, issued April 28, 1987.
23 5 U.S. Patent No. 4,689,396, issued August25, 1987.
24 6 U.S. Patent No. 4,851,385, issued July25, 1989.
25 7. U.S. Patent No. 5,198,533, issued March 30, 1993.
26 8. U.S. Patent No. 5,480,868, issued January2, 1996.
27 9. WO92/20711, published 26 November 1992.
28 10. WO95/00168, published 5 January 1995.
29 11. W095/04540, published 16 February 1995.
30 12. "Stability of Gonadorelin and Triptorelin in Aqueous Solution", V.J.
31 Helm, B.W. Muller, PharmaceuticalResearch, 7/12, pages 1253-1256 32 ( 1990).

CA 022~9~7 1998-12-31 WO 98/00158 2 PCl~/US97/114~0 13. "New Degradation Product of Des-Gly1~-NH2-LH-RH-Ethylamide 2 (Fertirelin) in Aqueous Solution", J. Okada, T. Seo, F. Kasahara, K.

3 Takeda, S. Kondo, J. of PharmacelJ~ical Sciences, 80/2, pages 167-4 170 (1991).

5 14. "Characterization of the Solution Degradation Product of Histrelin, a 6 Gonadotropin Releasing Hormone (LHRH) Agonist", A.R. Oyler, R.E.

7 Naldi, J.R. Lloyd, D.A. Graden, C.J. Shaw, M.L. Cotter, J. of 8 Pharmaceutical Sciences, 80/3, pages 271-275 (1991).

9 15. "Parenteral Peptide Formulations: Chemical and Physical Properties of ~0 Native Luteinizing Hormone-Releasing Hormone (LHRH) and Hydrophobic Analogues in Aqueous Solution", M.F. Powell, L.M.
2 Sanders, A. Rogerson, V. Si, PharmaceLltical Research, 8/10, pages 3 1258-1263 (1991).
4 16. "Degradation of the LHRH Analog Nafarelin Acetate in Aqueous Solution", D.M. Johnson, R.A. Pritchard, W.F. Taylor, D. Conley, G.
16 Zuniga, K.G. McGreevy, Intl. J. of Pharmaceutics, 31, pages 125-129 17 (1 986).
8 17. "Percutaneous Absorption Enhancement of Leuprolide", M.Y. Fu Lu, D.
19 Lee, G.S. Rao, PharmaceuticalResearch, 9/12, pages 1575-1576 (1992).
21 18. Lutrepulse (gonadorelin acetate for IV injection), Physician's Desk 22 Reference, 50th Edition, pages 980-982 (1996).
23 19. Factrel (gonadorelin HCI for subcutaneous or IV injection), Physician's 24 Desk Reference, 50th Edition, pages 2877-2878 (1996).
25 20. Lupron (leuprolide acetateforsubcutaneous injection), Physician's 26 Desk Reference, 50th Edition, pages 2555-2556 (1996).
27 21. Lupron depot (leuprolide acetate for depot suspension), Physician's 28 Desk Reference, 50th Edition, pages 2556-2562 (1996).
29 22. "Pharmaceutical Manipulation of Leuprorelin Acetate to Improve Clinical Performance", H. Toguchi, J. of InU. Medical Research, 18, 31 pages 35-41 (1990).

CA 022~9~7 l998-l2-3l WO 98/00158 3 PCT~S97/11450 23. "Long-Term Stability of Aqueous Solutions of Luteinizing Hormone-2 Releasing Hormone Assessed by an In-Vitro Bioassay and Liquid 3 Chromatography", Y.F. Shi, R. J. Sherins, D. Brightwell, J.F. Gallelli, D.
4 C. Chatterji, J. of Pharmaceutical Sciences, 73/6, pages 819-821 ( 1984) .
6 24. "Peptide Liquid Crystals: Inverse Correlation of Kinetic Formation and 7 Thermodynamic Stability in Aqueous Solution", M.F. Powell, J.
8 Fleitman, L.M. Sanders, V.C. Si, Pharmaceutical Research, 11/9, g pages 1352-1354 (1994~.
0 25. "Solution Behavior of Leuprolide Acetate, an LHRH Agonist, as Determined by Circular Dichroism Spectroscopy", M.E. Powers, A.
12 Adejei, M.Y. Fu Lu, M.C. Manning, Intl. J. of Pharmaceutics, 108, 13 pages 49-55 (1994).
4 26. "Preparation of Three-Month Depot Injectable Microspheres of Leuprorelin Acetate lJsing Biodegradable Polymers", PharmacelJtical Research, 11/8, pages 1 143-1147 (1994).
7 The disclosure of each of the above publications, patents or patent applications is hereby incorporated by reference in its entirety to the same 19 extent as if the language of each individual publication, patent and patentapplication were specifically and individually incorporated by reference.
21 Luteinizing hormone-releasing hormone (LHRH), also known as 22 gonadotropin releasing hormone (GnRH), is a decapeptide with the structure:23 pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2.
24 It is secreted by the hypothalamus and binds to receptors on the pituitary gland, releasing luteinizing hormone (LH) and follicle stimulating hormone 26 (FSH). LH and FSH stimulate the gonads to synthesize steroid hormones.
27 Numerous analogs of LHRH are known, including peptides related to LHRH
28 which act as agonists and those which act as antagonists. [1-15] LHRH
29 analogs are known to be useful for treating hormone-dependent diseases such as prostate cancer, benign prostatomegaly, endometriosis, 31 hysteromyoma, metrofibroma, precocious puberty, or mammary cancer and 32 as contraceptives. [8l Sustained release administration is preferred for both CA 022~9~7 l998-l2-3l WO 98/OOlS8 4 PCT/US97/11450 agonist LHRH-related compounds, which reduce the number of available 2 receptors after repeated administration so that the production of steroid 3 hormones is suppressed, and antagonist LHRH-related compounds, which 4 must be continually administered for persistent inhibition of endogenous LHRH. [8]
6 The sustained parenteral delivery of drugs, especially peptide drugs, 7 provides many advantages. The use of implantable devices for sustained 8 delivery of a wide variety of drugs or other beneficial agents is well known in g the art. Typical devices are described, for example, in U.S. Patents Nos.
0 5,034,229; 5,057,318; and 5,110,596. The disclosure of each of these 11 patents is incorporated herein by reference.
12 In general, oral bioavailability of peptides, including LHRH-related 13 compounds, is low. [16-17]
14 Currently marketed formulations of LHRH, its analogs and related compounds which are used for parenteral injection are aqueous solutions 16 which contain relatively low concentrations of LHRH-related compounds (0.0517 to 5 mg/ml) and may also contain excipients such as mannitol or lactose. [18-18 20] Such formulations of LHRH-related compounds must either be stored 19 refrigerated or may be stored at room temperature for short periods of time.
Available depot formulations of LHRH-related compounds 21 administered for sustained release over a period of 1-3 months include a 22 formulation comprised of 15% LHRH-related compound dispersed in a matrix 23 of D,L-lactic and glycolic acids copolymer presented as a cylinder to be 24 injected subcutaneously [1] and a formulation comprised of microparticles comprising a core of LHRH-related compound and gelatin surrounded by a 26 shell of D,L-lactic and glycolic acids copolymer. These microparticles are 27 suspended in a diluent for injection either subcutaneously or intramuscularly.
28 [21, 26] These products must be stored at room temperature or lower.
29 Aqueous formulations of LHRH-related compounds are known to exhibit both chemical and physical instability, as well as degradation after irradiation. [12-31 1 6, 22-25]

.. . ...

CA 022~9~7 l998-l2-3l Formulations which have been shown to be stable (tgo about five years) 2 have been very low concentration (25 ~g/ml) aqueous, buffered (10 mM, ionic3 strength of 0.15) solutions stored at temperatures no higher than room 4 temperature (2~~C). [15]
There is a need for stable formulations of peptides.

8 The present invention provides stable non-aqueous formulations which g are solutions of peptide compounds in polar aprotic solvents. In particular, the peptide compounds are formulated at concentrations of at least about 11 10%. These stable formulations may be stored at elevated temperatures 12 (e.g., 37~C) for long periods of time and are especially useful in implantable 13 delivery devices for long term delivery (e.g., 1-12 months or longer) of drug.
14 In one aspect, the invention provides stable non-aqueous formulations of peptide compounds, said formulations comprising at least one peptide 16 compound in at least one polar aprotic solvent. In a preferred embodiment, 17 the formulation comprises at least about 10% (w/w) peptide compound.
18 In another aspect, the invention provides methods for preparing a 19 stable non-aqueous formulation of a peptide compound, said methods comprising dissolving at least one peptide compound in at least one polar 21 aprotic solvent. Preferred formulations comprise at least about 10% (w/w) 22 peptide compound.
23 In yet a further aspect, the invention provides methods for treating a24 subject suffering from a condition which may be alleviated by administration of a peptide compound, said methods comprising administering to said 26 subject an effective amount of a stable non-aqueous formulation comprising 27 at least one peptide compound in at least one polar aprotic solvent.

.... ... . . .. . . .

CA 022~9S~7 l998-l2-3l BRIEF DESCRIPTION OF THE DRAWINGS
2 Figure 1 illustrates the stability of 40% leuprolide acetate solution (w/w) 3 in dimethylsulfoxide (methylsulfoxide or DMSO) after two months at 80~C as 4 measured by reverse phase HPLC (RP-HPLC).
Figure 2 shows the same sample as Figure 1 injected by size exclusion 6 chromatography (SEC). This figure shows that there is very little aggregation, 7 and what aggregation there is is comprised of dimer and trimer products, with 8 no higher order aggregation.
g Figure 3 presents the Arrhenius plot showing the loss of leuprolide from 40% solutions of leuprolide acetate in dimethylsulfoxide (DMSO).
11 Figure 4 illustrates the chemical and physical stability of a 40%
12 leuprolide solution in DMSO after six months at 80~C.
13 Figure 5 illustrates the loss of leuprolide from a 40% leuprolide acetate 14 solution in DMSO over a period of six months at 37~C, 50~C, 65~C or 80~C.
Figure 6 illustrates the chemical stability of a 40% leuprolide acetate 16 solution in DMSO over a period of nine months at 37~C.
17 Figure 7 illustrates that increasing the concentration of the peptide 18 leuprolide in DMSO solution increased stability at 80~C.
19 Figure 8 illustrates that increasing the moisture content of 40%
leuprolide-DMSO formulations resulted in decreased stability at 80~C.
21 Figure 9 illustrates that, in the formulations shown in Figure 8, 22 chemical degradation products increased with increasing moisture.

The present invention is drawn to the unexpected discovery that 26 dissolving peptide compounds in non-aqueous polar aprotic solvents results 27 in stable formulations. Previously known formulations of peptide compounds, 28 which are dilute buffered aqueous solutions containing excipients such as 29 EDTA or ascorbic acid which must be stored at low temperatures (4-25~C), form degradation products using degradation pathways such as acid/base 31 catalyzed hydrolysis, deamidation, racemization and oxidation. In contrast,32 the presently claimed formulations stabilize peptide compounds at elevated CA 022~9~7 l998-l2-3l temperatures (e.g., 37~C to 80~C) and at high concentrations (i.e., at least 2 about 10%).
3 Standard peptide and protein formulations consist of dilute aqueous 4 solutions. Drug stability is usually achieved by varying one or more of thefollowing: pH, buffer type, ionic strength, excipients (EDTA, ascorbic acid, 6 etc). For these formulations, degradation pathways requiring water 7 (hydrolysis, deamidation, racemization) cannot be fully stabilized. In contrast, 8 in the present invention, peptides formulated in non-aqueous solutions, such g as dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF), were shown to be chemically and physically more stable than those formulated in water.
DMSO and DMF are considered polar aprotic solvents. Aprotic solvents 2 would be expected to decrease the rate of degradation since they lack the 3 ability to contribute protons to degradation reactions. Conversely, solvents 4 that are more polar than water (for example, the dipole moment of water is 1.85, for DMF is 3.82, and for DMSO is 3.96) would be expected to increase 6 the rate of degradation since they can assist in stabilizing the rate determining 7 step and increasing the rate of degradation. However, we discovered that the 8 overall effect of polar aprotic solvents was generally to stabilize solutions of 19 peptides.
The invention consists of using non-aqueous, aprotic solvents such as 21 DMSO or DMF to stabilize peptide formulations against both chemical and 22 physical degradation. The discovery consists of the realization that use of23 DMSO or DMF improves the overall stability of peptides in a wide range of 24 formulation conditions, including high concentrations and elevated temperatures, thus making possible the delivery of peptides in long term 26 implantable devices that would not otherwise be feasible.

28 A. Definitions:
29 As used herein, the following terms have the following meanings:
The term "chemical stability" means that an acceptable perce,llage of 31 degradation products produced by chemical pathways such as oxidation or 32 hydrolysis is formed. In particular, a formulation is considered chemically CA 022~9~7 l998-l2-3l stable if no more than about 20% breakdown products are formed after two 2 months at 37~C.
3 The term "physical stability" means that an acceptable percentage of 4 aggregates (e.g., dimers, trimers and larger forms) is formed. In particular, a formulation is considered physically stable if no more that about 15%
6 aggregates are formed after two months at 37~C.
7 The term "stable formulation" means that at least about 65%
8 chemically and physically stable peptide compound remains after two months g at 37~C (or equivalent conditions at an elevated temperature). Particularly preferred formulations are those which retain at least about 80% chemically and physically stable peptide under these conditions. Especially preferred ~2 stable formulations are those which do not exhibit degradation after sterilizing 3 irradiation (e.g., gamma, beta or electron beam).
4 The terms "peptide" and/or "peptide compound" mean polymers of up to about 50 amino acid residues bound together by amide (CONH) linkages.
6 Analogs, derivatives, agonists, antagonists and pharmaceutically acceptable 7 salts of any of these are included in these terms. The terms also include 8 peptides and/or peptide compounds which have D-amino acids, modified, 19 derivatized or non-naturally occurring amino acids in the D- or L- configuration and/or peptomimetic units as part of their structure.
21 The term "LHRH-related compound" means luteinizing hormone 22 releasing hormone (LHRH) and its analogs and pharmaceutically acceptable 23 salts. Octa-, nona- and decapeptide LHRH agonists and antagonists are 24 included in the term LHRH-related compounds, as is native LHRH.
Particularly preferred LHRH-related compounds include LHRH, leuprolide, 26 goserelin, nafarelin, and other known active agonists and antagonists. [1-21]
27 The term "high concentration" means at least about 10% (w/w) and up 28 to the maximum solubility of the particular peptide.
29 The term "excipient" means a more or less inert substance in a formulation which is added as a diluent or vehicle or to give form or 31 consistency. Excipients are distinguished from solvents such as EtOH, which32 are used to dissolve drugs in formulations, and from non-ionic surfactants CA 022~9~7 1998-12-31 such as Tween 20, which are used to solubilize drugs in formulations, and 2 from preservatives such as benzyl alcohols or methyl or propyl parabens, 3 which are used to prevent or inhibit microbial growth.
4 The term "polar aprotic solvent" means a polar solvent which does not contain acidic hydrogen and does not act as a hydrogen bond donor.
6 Examples of polar aprotic solvents are dimethylsulfoxide (DMSO), 7 dimethylformamide (DMF), hexamethylphosphorotriamide (HMPT), and n-8 methyl pyrrolidone.
9 The term "non-aqueous protic solvent" means a non-polar solvent which contains hydrogen attached to oxygen or nitrogen so that it is able to 11 form hydrogen bonds or donate a proton. Examples of apolar protic solvents 12 are polyethylene glycols (PEGs), propylene glycol (PG), polyvinylpyrrolidone 13 (PVP), methoxypropylene glycol (MPEG), glycerol and glycofurol.

B. Preparation of Formulations:
16 The present invention is drawn to non-aqueous formulations of 17 peptide compounds in polar aprotic solvent which are stable for prolonged 18 periods of time at elevated temperatures. Standard dilute aqueous peptide 19 and protein formulations require manipulation of buffer type, ionic strength, pH and excipients (e.g., EDTA and ascorbic acid) to achieve stability. In 21 contrast, the claimed formulations achieve stabilization of peptide compounds 22 by the use of non-aqueous polar aprotic solvents. In particular, stability of 23 high concentrations (at least about 10%, w/w) of compound has been 24 provided by the formulations of the present invention.
Examples of peptides and peptide compounds which may be 26 formulated using the present invention include those peptides which have 27 biological activity or which may be used to treat a disease or other 28 pathological condition. They include, but are not limited to 29 adrenocorticotropic hormone, angiotensin I and ll, atrial natriuretic peptide, bombesin, bradykinin, calcitonin, cerebellin, dynorphin A, alpha and beta 31 endorphin, endothelin, enkephalin, epidermal growth factor, fertirelin, follicular 32 gonadotropin releasing peptide, galanin, glucagon, gonadorelin, CA 022~9~7 l998-l2-3l WO 98/00158 1 0 I'CT/US97/11450 gonadotropin, goserelin, growth hormone releasing peptide, histrelin, insulin, 2 leuprolide, LI~RH, motilin, nafarelin, neurotensin, oxytocin, somdtostalin, 3 substance P, tumor necrosis factor, triptorelin, and vasopressin. Analogs, 4 derivatives, antagonists, agonists and pharmaceutically acceptable salts of the above may also be used.
6 The peptide compounds useful in the formulations and methods of the 7 present invention can be used in the form of a salt, preferably a 8 pharmaceutically acceptable salt. Useful salts are known to those of skill in g the art and include salts with inorganic acids, organic acids, inorganic bases 0 or organic bases. Preferred salts are acetate salts.
Peptides and peptide compounds which are readily soluble in non-2 aqueous polar aprotic solvents are preferred for use in the present invention.
3 One of skill in the art can easily determine which compounds will be useful on 4 the basis of their solubility, i.e., the compound must be soluble in the particular non-aqueous polar aprotic solvent to at least an acceptable 6 amount. Preferred solubilities are at least about 10% (w/w). Particularly 7 preferred peptide compounds are LHRH-related compounds, including 8 leuprolide and leuprolide acetate.
19 The proportion of peptide may vary depending on the compound, the condition to be treated, the solubility of the compound, the expected dose and 21 the duration of administration. (See, for example, The Pharmacolo~ical Basis22 of Therapeutics, Gilman et al., 7th ed. (1985) and Pharmaceutical Sciences, 23 Remington, 18th ed. (1990), the disclosures of which are incorporated herein24 by reference.) The concentration of peptide in high concentration formulations may range from at least about 10% (w/w) to the maximum 26 solubility of the compound. A preferred range is from about 20 to about 60%
27 (W/w). The currently more preferred range is from about 30 to about 50%
28 (W/W) and a most preferred range is about 35 to about 45% (w/w).
29 It has unexpectedly been found that increasing the concentration of peptide that is dissolved in the non-aqueous polar aprotic solvent may 31 increase the stability of the peptide formulation. For example, as seen in 32 Figure 7, when solutions of 5, 10, 20 and 40% leuprolide in DMSO were -CA 022~9~7 l998-l2-3l stored for 8 weeks at 80~C with samples taken periodically and analyzed to 2 determine the percentage of leuprolide remaining, formulations containing 3 higher concentrations of leuprolide were more stable than formulations with 4 lower concentrations of leuprolide.
Generally, the stable formulations of the present invention may be 6 prepared by simply dissolving the desired amount, which may be a 7 therapeutically effective amount, of the desired peptide compound in the 8 selected non-aqueous polar aprotic solvent. Preferred polar aprotic solventsg include DMSO and DMF.
Increasing the water contained in the peptide formulations of the present invention increased peptide degradation as shown in Figure 8. It 12 appears that this increase may be due mainly to increasing chemical 13 degradation products, with aggregation remaining relatively constant 4 (Figure 9).
It has also been found that non-aqueous protic solvents such as PEG, 16 PG and PVP may optionally be added to the claimed formulations.

8 C. Methodolo~y:
19 We have found that stable non-aqueous formulations of peptide compounds may be prepared by dissolving the peptide compound to be 21 formulated in non-aqueous polar aprotic solvents.
22 We have tested these peptide compound formulations, specifically 23 formulations of the LHRH-related compound leuprolide, for stability by 24 subjecting them to accelerated aging at elevated temperature and measuring the chemical and physical stability of the formulations. Results of these 26 studies (shown, for example, in Table 11 and Figures 1, 2, 4 and 6) 27 demonstrate that these formulations were stable at conditions that 28 approximate or exceed storage for one year at 37~C.
29 We have also tested peptide compound formulations prepared as described herein for stability after 2.5 megarad gamma irradiation. Results, 31 shown in Table 111, show that these formulations remained chemically and 32 physically stable after such irradiation.

CA 022~9~7 1998-12-31 As shown in Table 1, we have tested a wide variety of peptide 2 formulations, specifically leuprolide, goserelin, LHRH, angiotensin 1, 3 bradykinin, calcitonin, enkephalin, insulin, neurotensin, substance P, 4 trypsinogen and vasopressin, for stability by dissolving (or attempting to 5 dissolve) them in the non-aqueous polar aprotic solvent DMSO, then 6 subjecting them to accelerated aging at elevated temperatures. The stability 7 of the formulations was measured. Results are presented in Table I as half-8 life at 37~C assuming an Ea = 22.2 kcal/mole. A wide range of the peptides g tested were soluble in DMSO and remained stable under the test conditions.

10 The solubility of a particular peptide in a particular non-aqueous polar aprotic solvent and the stability of the resulting solution are easily determined using 12 routine procedures known to those of ordinary skill in the art.

CA 022~9~7 1998-12-31 I'CT/US9711 1450 Table l: Stability of Peptides Formulated in DMSO

FORMULATION HALF-LIFE*
(Temperature) 40% Leuprolide 29.8 years (37~C) 40% Goserelin 5.0 years (80~C) 20% LHRH 8.2 years (65~C) 20% Angiotensin 1 4.2 years (65~C) 5% Angiotensin 1 4.1 months (50~C) 20% Bradykinin 2.9 months (65~C) 40% Calcitonin insoluble (80~C) 20% Calcitonin 2.4 months (80~C) 5% Calcitonin 100% stability at 2 months (50~C) 10% Enkephalin 1.9 months (80~C) 5% Enkephalin 2.6 months (50~C) 20% Insulin insoluble gel (65~C) 5% Neurotensin 5.0 months (50~C) 5% Substance P 3.0 months (50~C) 40% Trypsinogen insoluble crystal/gel (65~C/80~C) 20% Trypsinogen insoluble gel (65~C) 5% Trypsinogen 5.9 months (50~C) 40% Vasopressin degraded (80~C) 20% Vasopressin 11.8 days (65~C) *Half-life at 37~C assuming Ea = 22.2 kcal/mole.

4 Formulations of 40% peptide in DMSO stored for six months at 37~C, 5 50~C, 65~C and 80~C showed non-linear Arrhenius kinetics as measured by 6 overall loss of peptide from the solution, showing stability of these 7 formulations at elevated temperatures. Analysis of data collected at 37~C
8 gave a tgo of 14.4 months, indicating that stability at 37~C is still very good.

CA 022~9~7 l998-l2-3l WO 98/OOlS8 1 4 PCT/US97/11450 Temperature appears to affect both the rate of degradation and the 2 ratio of the degradation products of the formulations of the present invention.
3 Studies of leuprolide-DMSO formulations have shown that at 65~C and 80~C
4 oxidation appears to be the major chemical degradation pathway.
Conversely, at 37~C and 50~C hydrolysis and isomerization appear to be the 6 predominant degradation routes for these formulations.
7 We have also unexpectedly found that certain peptide formulations of 8 the present invention are bacteriostatic (i.e., inhibit bacterial growth), g bactericidal (i.e., cause the death of bacteria), and sporicidal (i.e., kill spores).
In particular, leuprolide formulations of 50-400 mg/ml exhibited bacteriostatic,bactericidal and sporicidal activity. The stability of the samples was 2 unaffected by spiking with bacteria, indicating that the enzymes released from 3 the killed and Iysed bacteria did not adversely affect the stability of the 4 product. This demonstrates that these formulations were not conducive to enzymatic activity.
6 Some peptides, for example calcitonin and leuprolide, are known to be 7 physically unstable, exhibiting aggregation, gelation and fibrillation when 8 formulated in aqueous solution. Improving physical stability can increase 19 bioavailability, alleviate sensitization and immune response, and allow for easier parenteral ad"lini~ lion, including administration using implantable 21 drug delivery systems.
22 It has unexpectedly been found that certain peptides, such as 23 leuprolide, goserelin and calcitonin, formulated in the non-aqueous polar 24 aprotic solvents of the present invention do not gel. No gelation was found 2s even after 12 months at 37~C. This is apparently because non-aqueous polar 26 aprotic solvents cause peptides to form a random coil/alpha helix 27 conformation that does not refold into a beta sheet structure and, therefore, 28 does not gel. Thus, these solvents have an anti-gellant effect.
29 A major aspect of the invention is that non-aqueous solutions containing peptide compounds in polar aprotic solvents are chemically and 31 physically stable at high temperatures for long periods of time. Such 32 formulations are stable even when high concentrations are used. Thus, these CA 022~9~7 l998-l2-3l formulations are advantageous in that they may be shipped and stored at 2 temperatures at or above room temperature for long periods of time. They 3 are also suitable for use in implantable delivery devices.

DISCLOSURE OF EXAMPLES OF THE INVENTION
- 6 The foliowing methods were used to perform the studies in the 7 Examples that follow.

9 1. Preparin~ leuprolide acetate solutions Leuprolide acetate (obtained, for example, from Mallinckrodt, St. Louis, Missouri) was weighed and dissolved with stirring or centrifugation in vehicle (DMSO, DMF, DMSO/PEG, DMSO/PG, or DMSO/PVP) at the appropriate 13 concentration. The term dry DMSO refers to DMSO formulations prepared in 14 a low moisture environment (i.e., dry N2 atmosphere).
Unless otherwise noted, leuprolide free base content was calculated 6 from certificate of analysis potency values to be 37~C free base. This was 17 40% leuprolide acetate, except as noted.

19 2. Preparation of reservoirs The reservoirs of implantable drug delivery devices (as disclosed in 21 U.S. Patent Application Serial No. 08/595,761, incorporated herein by 22 reference) were filled with the appropriate leuprolide acetate solution. The 23 formulation was filled into titanium or polymer reservoirs with a polymer plug 24 blocking each end. The filled reservoir was then sealed in a polyfoil bag and placed in a stability testing oven.
26 It should be noted that the formulations in the reservoirs of these 27 devices are completely isolated from the outside environment.

CA 022~9~7 1998-12-31 3. Reverse Phase-HPLC (RP-HPLC) 2 All stability samples were analyzed for leuprolide concentration and %
3 peak area using a gradient elution reversed-phase HPLC assay with a 4 refrigerated autosampler (4~C) to minimize sample degradation. The chromatographic conditions used are listed below.

7 RP-HPLC Chromatographic Conditions Description Parameter Column HaiSil C~8, 4.6 X 250mm, S/N 5103051 Flow Rate 0.8 mL min~' Injection Volume 20 IlL
Detection 210 nm Leuprolide Retention Time Between 25-30 minutes Mobile Phase A = 100 mM Sodium Phosphate, pH 3.0 B = 90% Acelon 'r:'-NVater Gradient Minutes 0 5 25 40 41 46 46.1 50 %B 15 26.5 26.5 65 85 85 15 15 g Leuprolide standards (in water) at 4 to 6 different concentration levels, typically between 0.1 - 1.2 mg/mL, were run along with the stability samples.
The stability samples were bracketed by the standard sets, with no more than 2 40 samples in between the standard sets. All peaks between the void volume 3 and 45 minutes of the run were integrated. The integrated peak areas for the 14 leuprolide standards were plotted as a function of the concentration. The leuprolide concentrations for the stability samples were then calculated using 6 linear regression. The % peak areas for the leuprolide peak, the sum of all7 the peaks eluting before leuprolide (labeled "others"), and the sum of all the 8 peaks eluting after leuprolide (labeled "aggregates") were also recorded and 19 plotted as a function of the sample timepoints.

CA 022~9~7 1998-12-31 4. Size Exclusion Chromato~raphy (SEC) 2 Selected stability samples were analyzed for % peak area and 3 molecular weights using an isocratic solution SEC assay with a refrigerated4 autosampler (4~C). The chromatographic conditions used are listed below.

6 SEC Chromatographic Conditions Description Pat ~" ,~l~r Column Pharmacia Peptide, HR 10130, 10 X 300 mm Flow Rate 0.5 mL min~7 Injection Volume 20 ,uL
Detection 210 nm Leuprolide Retention Time Approximately 25 minutes Mobile Phase 100 mM Ammonium Phosphate, pH 2.0, 200 mM
Sodium Chloride, 30% Acetonitrile g The void volume and total volume for the size exclusion column was 0 needed for the calculation of the molecular weights. The BioRad high molecular weight standard and 0.1% acetone were used to determine the 2 void volume and total volume respectively. The retention times for the first 3 peak in the BioRad standard and the acetone peak were recorded and 4 converted to volume units using the equations below. Since these values areconstant for a particular SEC column and HPLC system, the void and total 6 volumes were redetermined whenever changes to the SEC column or HPLC
7 system were made. A standard run was then made followed by the stability 8 samples. The standard mixture contained approximately 0.2 mg/mL of the 19 following peptides: Bursin (MW=449), WLFR peptide (MW=619), Angiotensin (MW=1181), GRF (MW=5108), and Cytochrome C (MW=12394). These 21 standards were chosen because they bracketed leuprolide molecular weight 22 and all had basic pl (9.8 - 11.0), similar to leuprolide.

CA 022~9~7 1998-12-31 The % peak areas were recorded for all the peaks. The molecular 2 weights for the species separated were calculated using the equations below.3 Vs = flow rate (mL/min) x sample peak retention time (min) 4 Vo = flow rate (mL/min) x void volume peak retention time (min) Vt = flow rate (mL/min) x total volume peak retention time (min) 7 Kd = ~ V0 8 Vt - Vo 0 Where:
Vs = standard or sample volume 2 Vo = void volume 3 Vt = total volume Vs was calculated to each peptide standard peak. Kd for each peptide 16 standard was then calculated using the values for Vt and VO determined 7 earlier. The linear regression line from the plot of logMW vs. Kd-' was used to determine the molecular weights for each peak in the stability sample. The 19 % peak areas for the stability samples were also recorded.

21 5. Instrumentation and Materials 22 The instrumentation and materials used for RP-HPLC and SEC were 23 as follows:
24 Waters Millennium HPLC system consisting of 717 autosampler, 626 pump, 6000S controller, 900 photodiode array detector, and 414 refractive 26 index detector (Waters Chromatography, Milford, MA) 27 HPLC vials, for 48-position and 96-position (Waters Chromatography, Milford, 28 MA) 29 HaiSil C18, 120 A, 5 !1m4.6 x 250 mm HPLC column (Higgins Analytical, Mountain View, CA) 31 Pharmacia Peptide, HR 10/30 SEC column (Pharmacia Biotech, Piscataway, 32 NJ) CA 022~9~7 l998-l2-3l The following examples are offered to illustrate this invention and are 2 not meant to be construed in any way as limiting the scope of this invention.

Accelerated Stability Studies of Leuprolide Acetate Formulations 6 Formulations of 40% (w/w) leuprolide acetate (equivalent to about 37%
7 leuprolide free base) in vehicle were prepared as described above and used 8 to fill the reservoirs of implantable drug delivery devices~ also as described g above. All reservoirs were made of titanium.
The filled devices were subjected to accelerated aging by storing them 11 at elevated temperatures (80~C) for seven days in an oven (Precision 12 Scientific or Thelco). This is equivalent to about 1.5 years at 37~C or about13 four years at room temperature (25~C).
14 The samples were analyzed using RP-HPLC and SEC as described 15 above to determine the chemical and physical stability of the aged 16 formulations.
17 Results, presented in Table ll, demonstrate that these formulations 18 were able to maintain the stability of the LHRH-related compound leuprolide.
19 In each case, at least 65% Ibuprolide was retained.

CA 022~9~7 1998-12-31 Table ll 3Stability of Leuprolide Acetate Polar Aprotic Formulations After 7 Days 4at 80~C in Titanium Reservoirs Formulation % Leuprolide at Day 7 40% in DMSO 92 40% in DMSO/PEG (50/50) 90 40% in DMSO/PG (50/50) 86 40% in DMSO/PVP (50/50) 93 40% in DMF 91 40% in dry DMSO 89 8 Stability Studies of Irradiated Leuprolide Acetate Formulations g Formulations of 40% (w/w) leuprolide acetate in DMSO were prepared 10 as described above and used to fill the reservoirs of drug delivery devices, 11 also as described above. All reservoirs were made of titanium.
12 The filled devices were sent to Sterigenics (Tustin, California) where 13 they were subjected to 2.5 megarad gamma irradiation using Cobalt 60, 3-14 level "tote box" irradiation in Sterigenics' Tustin Main Cell. In Table lll, the 15 samples labeled "cold" were shipped and irradiated on dry ice. Samples were 16 then subjected to accelerated aging as in Example 1. Samples were taken at 17 day 0 and day 7, and analyzed using RP-HPLC and SEC as described above 18 to determine the chemical and physical stability of the irradiated formulations.
~9 Results, presented in Table lll, demonst,ate that these leuprolide 20 acetate formulations were stable after irradiation. In every case, at least 65%
21 leuprolide was retained, with low levels of aggregate formation.

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SU~ 111 UTE SHEET (RULE 26) CA 022~9~7 1998-12-31 Accelerated Lonq-Term StabilitY Studies of Leuprolide Acetate Formulations Solutions of 40 % leuprolide acetate (w/w) in DMSO were prepared, loaded into reservoirs, stored for two months at 80~C and analyzed as described above. Results, shown in Figures 1 (RP-HPLC) and 2 (SEC) show 10 that 81.1% leuprolide was recovered, with only 14.6% chemical degradation and 5.1% physical aggregation.
Leuproiide acetate solutions were prepared, loaded, stored at 80~C for six months and analyzed as described above. Figure 4 is a plot of leuprolide, and its chemical and physical degradation products recovered over the six month time period, showing that we accounted for all the peptide material we started with and that these formulations showed good stability at 80~C. The sum of these three elements is also presented as mass balance. Figure 5 is a plot of the natural log of these data, showing that these formulations exhibited linear kinetics over the entire temperature range tested.
The chemical stability of 40% leuprolide acetate solutions prepared and analyzed as described above is presented in Figure 6. After nine months at 37~C more than 90% (93.5%) leuprolide was present, with less than 5%
(2.9%) chemical degradation products (shown as "early" in the figure) and less that 5% (2.3%) physical degradation products (shown as "late" and 25 based on the RP-HPLC profile, but in good agreement with SEC) being formed.
Solutions of 40% leuprolide acetate (w/w) in DMSO were prepared, loaded into reservoirs, stored at 37~C, 50~C, 65~C or 80~C and analyzed using RP-HPLC as described above. Results were calculated as described in 30 Physical Pharmacy: Physical Chemical Principles in the Pharmaceutical Sciences, 3rd ed., Martin et al., Chapter 14 (1983) and showed that loss of leuprolide from DMSO formulations was non-linear. The data are shown below and an Arrhenius plot is presented in Figure 3.

.

CA 02259557 l998-l2-3l WO 98/00158 PCT~S97/11450 Because Arrhenius plots of DMS0 formulations stored at 80~C showed that loss of leuprolide was non-linear, stability data collected at 37~C was used to calculate a t90 for these formulations of 14.4 months at 37~C.

~C Kobs (months 1) t1,2 (months) 37 7.29 X 10-3 95.1 9.74 X 10-3 71.2 2.48 X 10-2 27.9 0.108 6.4 Ea = non-linear Stability Studies of Leuprolide Acetate Formulations in DMSO/Water Formulations of 40% leuprolide acetate (w/w) in DMS0, DMSO/water (95:5,90:10,70:30, 50:50, and 30:70) and water were prepared as described 5 above and incubated for seven days at 80~C. Fourier Transfer Infrared Spectroscopy (FTIR) analysis was performed at day 0 and at day 7.
Results showed that the structural conformation of leuprolide changed very little after this accelerated aging for all the formulations tested. In general, peptide structure was predominantly random coil or a-helix in DMSO
20 formulations, while peptide structure was predominantly,B-sheet in water formulations.
Modification of the above-described modes of carrying out various embodiments of this invention will be apparent to those of skill in the art following the teachings of this invention as set forth herein. The examples 25 described above are not limiting, but are merely exemplary of this invention, the scope of which is defined by the following claims.

Claims (38)

What is claimed is:

1. A stable non-aqueous formulation of a peptide compound comprising:
a) at least one peptide compound; and b) at least one polar aprotic solvent, wherein said formulation is stable at 37°C for at least 3 months.

2. The formulation of Claim 1 which comprises at least about 10% (w/w) peptide compound.

3. The formulation of Claim 1 which comprises at least about 30% (w/w) peptide compound.

4. The formulation of Claim 1 wherein said peptide compound is an LHRH-related compound.

5. The formulation of Claim 4 wherein said peptide compound is selected from the group consisting of leuprolide, LHRH, nafarelin and goserelin.

6. The formulation of Claim 1 of which is stable at 80°C for at least 2 months.

7. The formulation of Claim 1 which is stable at 37° C for at least one year.

8. The formulation of Claim 1 which is adapted for use in an implantable drug delivery device.

9. The formulation of Claim 1 which further comprises a non-aqueous protic solvent.

10. The formulation of Claim 1 wherein said polar aprotic solvent is selected from the group consisting of DMSO and DMF.

11. The formulation of Claim 1 wherein said polar aprotic solvent provides an anti-gellant effect.

12. The formulation of Claim 1 which consists essentially of about 30% to about 50% (w/w) of the LHRH-related compound leuprolide acetate in DMSO.

13. The formulation of Claim 1 which consists essentially of leuprolide and DMSO in the proportions of 370 mg leuprolide in 1 ml DMSO.

14. The formulation of Claim 1 which is stable after irradiation.

15. A method for preparing the stable non-aqueous formulation of Claim 1 comprising dissolving at least one peptide compound in at least one polar aprotic solvent.

16. The method of Claim 15, wherein at least about 10% (w/w) peptide compound is dissolved.

17. The method of Claim 15 wherein at least about 30% (w/w) peptide compound is dissolved.

18. The method of Claim 15 wherein said peptide compound is an LHRH-related compound.

19. The method of Claim 18 wherein said peptide compound is selected from the group consisting of leuprolide, LHRH, nafarelin and goserelin.

20. The method of Claim 15 further comprising the step of adding a non-aqueous protic solvent.

21. The method of Claim 15 wherein about 30% to about 50% (w/w) of the LHRH-related compound leuprolide acetate is dissolved in DMSO.

22. The method of Claim 15 wherein 370 mg leuprolide is dissolved in 1 ml DMSO.

23. A method for treating a subject suffering from a condition which may be alleviated by administration of a peptide compound comprising administering to said subject an effective amount of the formulation of Claim 1.

24. The method of Claim 23 wherein said administration is parenteral administration.

25. The method of Claim 23 wherein said administration is long-term continuous administration.

26. The method of Claim 25 wherein said administration is accomplished by use of an implantable drug delivery device.

27. The method of Claim 23 wherein said condition is prostatic cancer and said peptide compound is leuprolide.

28. The method of Claim 27 wherein at least about 80 micrograms of leuprolide is administered daily.

29. The method of Claim 28 wherein said daily administration continues for a period selected from the group consisting of 3 months, 6 months and 12 months.

30. The method of Claim 29 wherein said daily administration for said period is continuous administration accomplished using an implantable drug delivery system.

31. The method of Claim 23 wherein said condition is prostatic cancer and said peptide compound is an LHRH antagonist.

32. A stable non-aqueous formulation of a peptide compound comprising:
a) at least one peptide compound; and b) at least one polar aprotic solvent, which formulation is stable at 37°C for at least 3 months, with the proviso that said formulation does not contain components containing added water.

33. A method for preparing the stable non-aqueous formulation of Claim 1 comprising dissolving at least one peptide compound in at least one polar aprotic solvent, with the proviso that the formulation does not contain components containing added water.

34. The method of Claim 33 which is conducted in an atmosphere of inert gas.

35. The method of Claim 34 wherein said atmosphere is dry nitrogen.

36. A stable non-aqueous formulation of a peptide compound comprising:
a) at least one peptide compound; and b) at least one polar aprotic solvent, wherein said formulation exhibits bacteriostatic, bactericidal or sporicidal activity without the use of a conventional bacteriostatic, bactericidal or sporicidal agent.

37. A method for preparing the stable non-aqueous formulation of Claim 36 comprising dissolving at least one peptide compound in at least one polar aprotic solvent with the proviso that no conventional bacteriostatic, bactericidal or sporicidal agent is added to the formulation.

38. A method for treating a subject suffering from a condition which may be alleviated by administration of a peptide compound comprising administering to said subject an effective amount of the formulation of claim 36.