Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Reexamination Certificate
1997-09-08
2001-10-23
Kishore, Gollamudi S. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
C264S004100, C264S004300, C514S003100, C514S021800
Reexamination Certificate
active
06306432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to slow release vehicles for delivering a biologically active agent. More particularly, the present invention relates to multivesicular liposomes containing IGF-I.
2. Description of Related Art
Proteins which are cleared rapidly from the circulation after intravenous or subcutaneous injections need to be administered repeatedly in order to maintain therapeutic blood levels. One of the proteins that needs frequent administration for therapeutic benefit is Insulin-like Growth Factor I (IGF-I). Mature, circulating IGF-I, a 7.65 kD protein, consists of B and A domains (homologous to the B and A chains of insulin). Unlike insulin, the B and A domains of the IGFs are connected by a C peptide, and contain an eight-amino-acid extension at the C-terminus, termed the D domain.
Native IGF-I contains three disulfide bonds involving the following residues: CysB6-CysB7, CysA6-CysA11, and CysB18-CysA20. Under reducing conditions, these disulfide bonds are broken and can become “scrambled” during oxidative refolding in denaturant solutions to yield two alternative disulfide isomers with distinct tertiary structures (L. O. Narhi et al.,
Biochemistry
32/5214-5221, 1993).
IGF-I is known to have multiple biological activities. Those with therapeutic potential are its activity in reversing catabolism in states of starvation, severe illness, or injury, in enhancing wound healing and nerve regeneration, and in reducing insulin resistance in diabetics. IGF-I is also known to generally stimulate the growth and maintenance of nervous tissue, increase glucose uptake of cells, and stimulate renal function. Chronic malnutrition and poorly controlled diabetes in the young are associated with lower circulating IGF-I levels and growth retardation.
Optimal treatment with IGF-I may require that the drug level be maintained at a specified level for a prolonged period of time. For example, optimal treatment of insulin dependency in diabetics may require maintenance of a relatively high level of IGF-I for a period of several days.
For certain other therapeutic usages, for example treatment of malnutrition or osteoporosis, a low level of IGF-I released over a period of several days would be beneficial.
One approach which has been used to provide controlled release compositions for drug delivery is liposome encapsulation. Among the main types of liposomes, multivesicular liposomes (Kim, et al.,
Biochim. Biophys. Acta;
728:339-348, 1983), are uniquely different from unilamellar liposomes (Huang,
Biochemistry;
8:334-352, 1969; Kim, et al.,
Biochim. Biophys. Acta;
646:1-10, 1981), multilamellar liposomes (Bangham, et al,
J. Mol. Bio.,
13:238-252, 1965), and stable plurilamellar liposomes (U.S. Pat. No. 4,522,803). In contrast to unilamellar liposomes, multivesicular liposomes contain multiple aqueous chambers. In contrast to multilamellar liposomes, the multiple aqueous chambers of multivesicular liposomes are non-concentric with membrane distributed as a network throughout.
In multivesicular liposomes the encapsulation efficiency of some small molecules, such as cytosine arabinoside, is relatively low, and the release rate of encapsulated molecules in biological fluids is faster than is therapeutically desirable unless the osmolarity of the first aqueous component is adjusted to control the rate of release. EP 0 280 503 B1 discloses coencapsulation of a hydrochlo ride such as hydrochloric acid, with an active agent to control the rate of release of the active agent. Further research, disclosed in WO 95/13796, has shown that the release rate of agents from multivesicular liposomes in human plasma can also be controlled by introduction of a non-hydrochloride acid into the aqueous solution in which the agent is dissolved prior to forming the multivesicular liposome. It is also known (WO 96/08253) to control the rate of release of active agents by introducing other types of solutes called “osmotic spacers” into the aqueous solution in which the active agent is dissolved prior to formation of the multivesicular liposomes.
In addition to the biologically active agent and acids or osmotic spacers intended to control the rate of release of the biologically active agent from the liposomes, it is common practice to coencapsulate with the active agent compounds that are intended to serve any of a number of helper functions. For instance, certain biologically active compounds retain activity only when kept at a particular pH. Thus acids or buffers are often necessarily encapsulated in addition to the active agent to control the pH of the drug environment. In other cases, a counterion is incorporated to enhance solubility of a biologically active agent that has low solubility.
Thus the need exists for new high load and low load slow release formulations of IGF-I having the bioactivity of free drug in a vehicle suitable as a slow release drug depot. Since IGF-I is an expensive drug, whether purified from biological samples or produced recombinantly, a need also exists to achieve these goals while keeping the encapsulation efficiency as high as possible to avoid waste of the expensive active agents.
SUMMARY OF THE INVENTION
The present invention provides a method for obtaining high loading and low loading formulations of IGF-I in multivesicular liposomes (MVLs) in an aqueous suspending medium and MVL formulations containing them. The low loading formulations are obtained by utilizing during manufacture a first aqueous component comprising a concentration of dissolved IGF-I from about 1 mg/mL to about 33 mg/mL, for example, about 5 mg/mL to about 20 mg/mL. The first aqueous component used in making the low loading formulations further can contain one or more osmotic excipients, such as sucrose, and sufficient of one or more pH adjusting agent, such as ammonium citrate dibasic, to maintain the pH in the range from about 1 to about 5.
The high loading formulations generally are obtained by utilizing during manufacture a first aqueous component containing a concentration of dissolved IGF-I from about 40 mg/mL to about 300 mg/mL, for example from about 100 mg/mL to about 160 mg/mL. The first aqueous component in the high load formulation further contain an acid, such as citric acid, sufficient to maintain the pH in the range from about 2 to about 4.8, and an osmotic excipient, such as sucrose.
Both the high load and low load formulations can be further diluted by addition of suspending medium or other biologically acceptable carrier to obtain injectable or implantable slow release depot formulations of any therapeutically effective total dosage.
Methods for making MVLs are well known in the art and are described in U.S. Pat. Nos. 5,455,044, 5,576,018, and in copending U.S. patent application Ser. Nos. 08/305,158, filed Apr. 13, 1994; 08/473,019, filed Jun. 6, 1995; 08/473,013, filed Jun. 6, 1995 and 08/502,569, filed Jul. 14, 1995. all of which are incorporated herein by reference in their entireties. The general procedure for making multivesicular liposomes imparts to them their characteristic properties, including the properties of modulated release of encapsulated biologically active substances. In this method, a “water-in-oil” emulsion containing the biologically active substance to be encapsulated is first made by dissolving at least one amphipathic lipid and at least one neutral lipid in a volatile organic solvent for the lipid component, adding to the lipid component an immiscible first aqueous component and emulsifying the mixture. A hydrochloride or non-hydrochloride acid can be added to either or both of the first aqueous component and the lipid component to control release of the active agent from the MVLs. In this general method, the biologically active substance to be encapsulated can be contained in the first aqueous component or in the lipid component, or both.
The entire water-in-oil emulsion is then mixed with the second aqueous component, and agitated mechanically, as above, to form solvent spherules suspended in the second a
Asherman John
Hora Maninder
Katre Nandini
Shirley Bret
Ye Qiang
Chiron Corporation
Fish & Richardson P.C.
Kishore Gollamudi S.
LandOfFree
High and low load formulations of IGF-I in multivesicular... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High and low load formulations of IGF-I in multivesicular..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High and low load formulations of IGF-I in multivesicular... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2614148