WO1996008262A1 - Composition and method for immunotherapy - Google Patents

Abstract

An improved method for suppressing graft rejection in a host subject is disclosed. The method, as applied to allograft rejection, includes administering an immunosuppressant compound in an amount substantially below that required for effective suppression of allograft rejection, when the compound is administered alone. The suppressive effect of the compound is potentiated by administration of an ethanolic extract of Tripterygium wilfordii or a purified triptolide component thereof. The method as applied to xenograft rejection, includes administering an immunosuppressant drug, where the drug or the amount of drug administered is, by itself, ineffective to suppress xenograft rejection. Effective xenograft suppression is achieved by also administering an ethanolic extract of Tripterygium wilfordii or a purified triptolide component thereof.

Description

COMPOSITION AND METHOD FOR IMMUNOTHERAPY

1. Field of the Invention

The present invention relates to compositions and methods for treating or inhibiting transplantation rejection, particularly in the context of allograft rejection, xenograft rejection, and graft versus host disease.

2. References

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3. Background of the Invention The immune system functions as the body's major defense against diseases caused by invading organisms. This complex system fights disease by killing invaders such as bacteria, viruses, parasites or cancerous cells. The immune system's ability to distinguish the body's normal tissues, or self, from foreign or cancerous tissue, or non-self, is an essential feature of normal immune system function. A second essential feature is memory, the ability to remember a particular foreign invader and to mount an enhanced defensive response when the previously encountered invader returns. The loss of recognition of a particular tissue as self and d e subsequent immune response directed against that tissue produce serious illness. An autoimmune disease results from the immune system attacking the body's own organs or tissues, producing a clinical condition associated with the destruction of that tissue. An autoimmune attack directed against the joint lining tissue results in rheumatoid arthritis; an attack against the conducting fibers of the nervous system results in multiple sclerosis. The autoimmune diseases most likely share a common pathogenesis and the need for safe and effective therapy.

Rheumatoid arthritis is one of the most common of the autoimmune diseases. Current treatments include three general classes of drugs (Schumacher, 1988): anti- inflammatory agents (aspirin, non-steroidal antiinflammatory drugs and low dose corticosteroids); disease-modifying antirheumatic drugs, known as "DMARDs" (antimalari- als, gold salts, penicillamine, and sulfasalazine) and immunosuppressive agents (azathioprine, chlorambucil, high dose corticosteroids, cyclophosphamide, methotrexate, nitrogen mustard, 6-mercaptopurine, vincristine, hydroxyurea, and cyclosporin A). None of the available drugs are completely effective, and most are limited by severe toxicity. In addition to their use in treating autoimmune conditions, a variety of immunosuppressive agents have been used in treating or preventing transplantation rejection. Organ transplantation involving human organ donors and human recipients (allogeneic grafts or allografts), and non-human, e.g. primate or porcine, donors and human recipients (xenogeneic grafts or xenografts), has received considerable medical and scientific attention (Roberts, 1989; Platt, 1990; Keown, 1991; Wang, 1991; Hasan, 1992; Murase, 1993). To a great extent, this effort has been aimed at eliminating, or at least reducing, the problem of rejection of the transplanted organ. In the absence of adequate immunosup¬ pressive therapy, the transplanted organ is destroyed by the host immune system.

From follow-up studies on human transplant patients, as well as transplantation studies in animal model systems, the following features of transplant rejection have been established. The major targets in transplant rejection are non-self alielic forms of class I and class II major histocompatibility complex (MHC) antigens. Rejection is mediated by both antibodies and cytotoxic T lymphocytes (CTLs), with the participation of CD4+ "helper" T cells (Noelle, 1991). In general, foreign class I MHC antigens stimulate CD8+ CTLs, and foreign class II MHC antigens stimulate CD4+ T cells (Roitt, 1991).

Presently, the most commonly used agents for preventing transplant rejection in allografts include corticosteroids, cytotoxic drugs that specifically inhibit T cell activation such as azathioprine, immunosuppressive drugs such as cyclosporin A, and specific antibodies directed against T lymphocytes or surface receptors that mediate their activation (Briggs, 1991; Kennedy, 1983; Storb, 1985; Storb, 1986). All of these drug therapies are limited in effectiveness in treating allograft rejection, in part because the doses needed for effective treatment of transplant rejection may increase the patient's susceptibility to infection by a variety of opportunistic invaders, and in part because of direct toxicity and other side effects.

Cyclosporin A, currently the most effective and most commonly used agent, is significantly toxic to the kidney. This nephrotoxicity limits the quantity of drug that can be safely given. The physician is frequently forced to administer sub-optimal doses of the drug because of this toxicity. With respect to allograft rejection, there are several compounds which have been used for suppressions of allograft rejection in a humans, including corticosteroids, cytotoxic drugs that specifically inhibit T cell activation such as azamioprine, immunosuppressive drugs such as cyclosporin A, and specific antibodies. In general, these compounds are not effective, or are only poorly effective, in suppressing xenograft rejection. Antibodies and complement have been shown to be of primary importance in the rejection of xenografts (Hasan). This has led to proposed therapies designed to severely inhibit antibody production as a means of suppressing xenograft rejection (Hasan). However, such drastic treatment can lead to increased risk of death by infection.

Graft versus host disease (GVHD), a condition in which transplanted bone marrow cells attack the transplant recipient (Thomas, 1975; Storb, 1984), remains a significant problem. Current treatment regimens include die use of immunosuppressive agents such as cyclosporin A, azathioprine, and corticosteroids. To date, these agents have achieved only partial success in treating the condition, and more effective agents are clearly needed. More specifically, many immunosuppressive agents are not effective for the treatment of GVHD, and one cannot conclude that an agent having immunosuppressive activity will be effective to treat GVHD. In the standard model of GVHD, mice treated with lethal irradiation survive about 12 days. Mice treated with lethal irradiation and subsequent marrow and spleen cell transplantation generally survive 20-45 days, before succumbing to GVHD. Cyclosporin A, which is effective in suppressing allograft transplantation rejection in rodents at 1 mg/kg/day, is minimally effective in preventing death due to GVHD at 30 mg/kg/day. At high doses of cyclosporin A (e.g., 50 mg/kg/day), some mice survive up to 100 days. However, this level of cyclosporin A leads to serious side effects, including loss of disease resistance, and thus cannot be sustained over an extended period. Accordingly, 6 it would be desirable to treat immunological conditions such as those above with an immunosuppressant compound that is effective in such treatment (e.g., cyclosporin A), but at dosage level which substantially reduces side effects and permits effective treatment over a longer period.

4. Summary of the Invention

In one aspect, the invention includes a method of for suppressing allograft rejection in a host subject. The method includes administering to the subject, an immunosuppressant drug such as cyclosporin A, FK506, azathioprine, rapamycin, mycophenolic acid, or a glucocorticoid, in an amount that is substantially less than the dose needed to achieve effective suppression of allograft rejection, when the compound is administered alone. A potentiator which is either (i) an ethanolic extract of Tripterygium wilfordii or a (ii) purified triptolide component of the extract, is administered in an amount effective to suppress allograft rejection in the host, when administered in combination with the immunosuppressive compound.

Exemplary triptolide components include 16-hydroxytriptolide, triptolide, or trip- chlorolide.

The immunosuppressive compound is preferably cyclosporin A, administered in an amount less than 1/3 the usual suppressive dose. The immunosuppressive drug and potentiator may be administered at regular intervals over a time period of at least 2 weeks.

In another aspect, the invention includes a method of suppressing xenograft rejection in a host subject. The method includes administering to the subject, an immuno¬ suppressant drug, including cyclosporin A, FK506, azathioprine, rapamycin, mycophenolic acid, a glucocorticoid, or a cyclophosphamide, where the drug or amount of drug administered is, by itself, ineffective to suppress xenograft rejection in the subject. A potentiator, which is either (i) an ethanolic extract of Tripterygium wilfordii or (ii) a purified triptolide component of the extract, is administered in an amount effective to suppress allograft rejection in the host in combination with the immunosuppressant drug. An exemplary immunosuppressant drug is cyclosporin A, for use in combination with the T. wilfordii extract or a triptolide component thereof, as represented by 16- hydroxytriptolide, triptolide, and tripchlorolide.

The immunosuppressive drug and potentiator may both administered at regular intervals over a time period of at least 2 weeks, and may be administered either orally or parenterally. The amount of immunosuppressant drug administered is typically between about 20% and 100% of the amount of drug needed to suppress allograft rejection in the host.

In still another aspect, the invention includes a method of suppressing graft versus host disease (GVHD) rejection in a host subject. The method includes administering to the subject, an immunosuppressant drug, such as cyclosporin A, FK506, azatiiioprine, rapamycin, mycophenolic acid, a glucocorticoid, or a cyclophosphamide, where the drug or amount of drug administered is, by itself, ineffective to suppress GVHD rejection in the subject. A potentiator, which is either (i) an ethanolic extract of Tripterygium wilfordii or (ii) a purified triptolide component of the extract, is administered in an amount effective to suppress GVHD rejection in the host in combination with the immunosuppressant drug.

These and other objects and features of the invention will become more fully apparent when the following detailed description of the invention is read in conjunction with the accompanying drawings.

Brief Description of the Drawings Fig. 1 is a flow diagram of a method for preparing a Tripterygium wilfordii (TW) ethanol extract, in accordance wiύi the invention, also showing additional purification methods that may be used to achieve more purified forms of the extract for use in the composition of me invention;

Fig. 2A is a thin layer chromatogram of 1:1,000 TW extract (Lane A), 1:5,000 extract (Lane B) and purified 1:10,000 TW extract (Lane C);

Fig. 2B is a proton NMR spectrum of a purified (1:10000) TW extract; Figs. 3A-3H show chemical structures of several purified TW components for use in the invention;

Fig. 4 shows the suppressive effect of a purified TW extract on production of JJL-lβ, TNF-α, IL-2, and IL-6 by human peripheral blood lymphocytes in culture;

Fig. 5A is a plot of heart allograft transplant survival time for untreated animals (squares), and animals treated with purified TW extract by oral administration (circles) or intraperitoneal administration (triangles);

Fig. 5B is a plot of allograft transplant survival time for untreated animals (open triangles), and animals treated with TW extract alone (solid diamonds), cyclosporin A alone (CsA) (open circles), and CsA in a TW extract (* symbols); Fig. 6 is a plot of percent survival of allograft transplant recipients treated with CsA alone (open circles), CsA plus a TW extract (2.5 mg/kg/day, solid squares), CsA plus TW extract (5 mg/kg/day, solid triangles), and CsA plus TW extract (10 mg/kg/day, * symbols); Fig. 7A is a plot of heart xenograft transplant survival time for untreated animals

(solid squares), and animals treated with TW extract alone by oral administration (open diamonds), CsA alone by intraperitoneal administration (solid circles), and CsA (ip) plus a TW extract (oral) (open diamonds);

Fig. 7B is a plot of xenograft transplant survival time for animals treated as indicated in Fig. 7A, but with different CsA and TW extract amounts;

Fig. 8 is a plot of xenograft transplant survival time for recipients treated with no drug (control, open diamonds), TW extract (solid circles), CsA alone (* symbols), azathioprine plus CsA (open squares), tripchlorolide plus CsA (open circles), and triptolide plus CsA (solid triangles); Figs. 9A and 9B show plots of anti-xenograft IgG (9 A) and IgM (9B) levels measured as a function of time in xenograft recipients treated with no drug (control, open squares), TW extract (* symbols), CsA alone (open circles), and TW extract plus CsA (solid diamonds);

Figs. 10A and 10B show plots of anti-xenograft IgG (10A) and IgM (10B) levels measured as a function of time in xenograft recipients treated with no drug (control, open squares), tripchlorolide plus CsA (open circles), and triptolide plus CsA (solid triangles);

Fig. 11 shows the concanavalin A proliferation response of spleen cells taken from mice after allogenic spleen cell transplantation (injected iv), and treatment with various compositions; and Fig. 12 graphs the survival time of mice treated for GVHD following lethal-level irradiation and allogenic bone marrow and spleen cell transplantation, and treatment with various compositions. Detailed Description of the Invention

L Definitions

The terms below have the following meanings, unless specified otherwise: "Immunosuppression therapy" refers to treatment of a mammalian subject, including a human subject, to suppress an immune response against a transplanted allogeneic or xenogeneic cell, tissue or organ, or to suppress graft-versus-host disease.

An "ethanol extract of the root xylem from T. wilfordii" refers to a composition containing ethanol-soluble components extracted from the root xylem of T. wilfordii; such a composition may include water-soluble components that are also soluble in ethanol. The extract may be relatively unpurified, or may exist in progressively more purified forms, as described below. For example, water-soluble components and components which bind to silica gel in the presence of chloroform-containing solvents may be removed from the extract. "Potentiated immunosuppression activity" refers to enhanced efficacy in immunosuppression therapy, as demonstrated by an enhanced therapeutic effect at a given immunosuppressant drug dose, or by equivalent therapeutic effect at a reduced immunosuppressant drug dose.

Allograft rejection is "effectively suppressed" or "suppressed" in a host if the survival time of the allograft in the host is extended by a statistically meaningful period over the survival time in me host in the absence of graft-suppression tfierapy. Typically, an effective suppression of allograft rejection is a period of at least or more weeks, and may be up to several months or more.

By "an amount that is substantially less than the dose needed to achieve effective suppression of allograft rejection, when the compound is administered alone" is meant an amount of immunosuppressant drug which is below 50% (preferably below 33%) of the amount that would otherwise be administered if used without an ethanolic TW extract or purified TW component.

By "purified triptolide component" is meant a compound having the parent structure of compound 3B (triptolide), and analogs having one or more substituent modifications to the parent structure, such as the 16-hydroxyl group modification in Fig. 3A, die halo addition in Fig. 3C, the ring keto group modification in Fig. 3F, and the epoxide group modifications in Fig. 3G, wherein the compound has been purified to at least 80% purity (preferably at least 90%) from its biological or synthetic source. II. TW Extract and Purified TW Components A. Preparation Methods

The TW extract of the invention is obtained from the root xylem of Tripterygium wilfordii (TW), a medicinal plant which is grown in the Fujiang Province and other southern provinces of China. Plant material can be obtained in China or through commercial sources in the United States. One method of preparation of a TW ethanol extract is illustrated in Fig. 1, and detailed in Example 1. Briefly, dried plant material is ground into a crude powder and then extracted by boiling in 95% ethanol with refluxing. The ethanol is removed and the extraction typically repeated twice. The resulting extracts are then combined and the ethanol removed (for example, by evaporation or heat-assisted evaporation). About 10 g dry ethanol extract is usually recovered per kg dry weight of plant material. This simple ethanol extract represents one preparation useful in the practice of the treatment method of the present invention. The extract is composed of plant components which are extractable from T. wilfordii root xylem by edianol. The ethanol extract from above may be further purified, to remove components, for example, which do not contribute to the potentiation of other immunosuppressant drugs. An exemplary purification method is shown in Fig. 1, and detailed in Example 2. Briefly, the ethanol extract from above is filtered and the volume is reduced under vacuum. The resulting syrup is diluted with water. Chloroform-soluble components are extracted by adding chloroform, separating the non-aqueous-phase material, and discarding the aqueous-phase components. The chloroform extract can be concentrated, e.g., by evaporation, and applied to a silica gel column. The extract material is then eluted successively with chloroform and chloroform: methanol (95:5) at a yield of about 1 g extract material per 20 g of original ethanol extract, corresponding to about 100 g dry weight starting plant material.

This partially purified extract is referred to as a 1:1000 TW extract. The extract includes ethanol extract components limited to those components which are further extractable from ethano water (2:1) by methylene chloride, and are further retained on silica gel in 100% methylene chloride. The 1:1000 extract can be further purified (Example 2) by application to a silica gel column and elution with mediylene chloride: methanol (97:3). Typically, six fractions are collected with the first and last of the six fractions being discarded. The four intermediate eluted fractions are combined, with a yield of about 20 g material per 100 gram 1:1000 extract. The resulting extract is referred to herein as a 1:5000 extract, and contains plant components further limited to those components which are elutable from silica gel by methylene chloride:methanol (95:5), and are further elutable from silica gel using methylene chloride:methanol (97:3).

The 1:5000 extract can be further purified by the same procedure, i.e., by elution from silica gel with methylene chloride :med anol (97:3) and collection of the intermediate fractions, with a final yield of about 1 g material per 2 gram 1:5000 extract. This purified extract is referred to herein as a 1:10,000 extract, and includes components which are contained in the intermediate fractions which are eluted from a silica gel column by elution with methylene chloride: methanol (97:3). It will be appreciated that the above purification steps are exemplary of the types of purification procedures that may be employed, if desired, to remove unneeded components from the ethanol-soluble TW extract. A variety of other chemical purification methods known to those skilled in the art may also be employed.

Fig. 2A shows a thin-layer chromatogram of the various TW extract preparations prepared as above. Thin-layer chromatography and the chemical assays were carried out as described in Example 3. These experiments showed that (1) purification between the 1:1,000, 1:5,000 and 1:10,000 extracts (lanes A, B, and C, respectively) has removed a number of major plant components; and (2) the 1:1000, 1:5000, and 1:10,000 extracts contain no alkaloids, as determined using the Dragendorff reagent. Chemical structures of purified TW components for use in die invention are illustrated in Figures 3A-3H. The structure of 16-hydroxytriptolide is shown in Fig. 3A. A purification procedure for this compound is described, for example, in PCT Publication No. WO 94/26265 published November 24, 1994, which is incorporated herein by reference. Fig. 3B shows the structure of triptolide, which can be obtained in pure form by methods described in Kupchan et al. (1972), Kupchan et al. (1977), and Pu et al. (1990). Tripchlorolide, shown in Fig. 3C, can be prepared from TW by methods described in Zhang et al. (1992), Lu et al. (1990; 1991), and Zhang et al. (1986a), or can be prepared synthetically from triptolide as described in Ma et al. (1992). Celastrol (Fig. 3D) can be purified as described in Johnson et al. (1963) and Zhang et al. (1986a,b). Salaspermic acid (Fig. 3E) can be purified as described in Viswanathan et al. (1979), Zhang et al. (1986a), and Kashiwada et al (1992). Triptonide (Fig. 3F) can be purified as described in Kupchan et al. (1972), Wu et al. (1992), and Zhang et al. (1986c). Triptophenolide (Fig. 3G) can be purified as described in Deng et al. (1982; 1992). Wilforlide B can be purified by the method of Quin et al. (1982). Tripdiolide (structure not shown) can be purified as described in Kupchan et al. (1972; 1977).

B. Biological Properties of TW Extract The 1:10,000 extract from above was examined for immunosuppressive activity in a variety of biological assays. The following properties were observed:

1. The extract inhibited peripheral blood lymphocyte (PBL) proliferation that was stimulated by anti-CD3 antibody (Example 4). Increasing amounts of purified TW extract produced dose-dependent inhibition of proliferation in both stimulated and unstimulated cells, in d e concentration range from about 0.3-1.25 μg extract components/ml culture medium. At a concentration of 1.25 μg/ml, die extract inhibited proliferation of unstimulated PBLs 36-fold, and inhibited proliferation of stimulated PBLs 860-fold.

2. The effect of the purified TW extract on the production of die cytokines IL-1, TNF-α, IL-2, and IL-6 was assessed by measuring die concentration of tiiese cytokines in the culture medium of anti-CD3 stimulated and unstimulated human PBLs. Cytokine levels were measured by standard ELISA methods using commercially available kits. Briefly, assay buffer was added to each of the wells of a microtiter plate containing pre-bound anti-cytokine antibody, followed by addition of standard or sample solution, diluted appropriately for the concentration range measured, followed by a second reporter-labeled antibody specific against die anti-cytokine antibody. Details are given in Example 5.

Fig. 4 shows the levels of IL-lβ, TNF-α, IL-2, and IL-6 in human PBLs at basal levels (open bars), in cells stimulated widi anti-CD3 antibody (shaded bars), and in anti- CD3 antibody-stimulated cells treated with purified TW extract (solid bars). Anti-CD3 stimulation resulted in a significant increase in all four cytokines measured. The purified TW extract significantly inhibited the production of TNF-α, IL-2, and IL-6, whereas the extract decreased production of IL-lβ only slightly. Extract was added to die culture at a concentration of 5 μg/ml culture medium.

3. The ability of the extract to suppress d e cell-proliferative effect of IL-1 in mouse thymocytes (O'Gara, 1990) was also examined. Almost complete inhibition of cell proliferation was observed in the range of 0.01 to 1 μg dried extract components/ml culture medium.

4. The extract also suppressed, but at higher concentration, the cell-proliferative activity of IL-2 on the IL-2 dependent cell line, HT-2, according to published med ods (Watson, 1979). 5. Potential cytotoxicity of the extract was assessed by measuring the effect of die purified extract on the ability of cultured cells to reduce MTT (3-[4,5-Dimethyldιi- azol-2-yl]-2,5-diphenyltetrazolium bromide), an index of cellular respiration. This is a sensitive assay for me detection of cytotoxicity (Green, 1984). Details of the procedure are given in Example 6. In addition, staining with the vital dye trypan blue, which stains dead cells, was also carried out routinely in all of die culture systems described. Toxicity was evaluated in vitro in two different cell culture systems, human PBLs and mouse thymocytes. No cytotoxicity was observed at an extract concentration of 10 mg/ml in PBLs and 3.1 mg/ml in mouse thymocytes, the highest concentrations tested in each system. 6. A measure of in vivo immunosuppression is inhibition of cell proliferation in die mixed lymphocyte reaction (MLR) (Bradley; Mishell, 1980). In these experiments, mice were treated with the TW extract for 14 days. Spleen cells, the "responder" cells, were prepared and co-cultured with irradiated spleen cells prepared from a different mouse strain, e "stimulator" cells. The responder cells proliferate in the presence of die allogenic stimulator cells. Irradiation of me stimulator cells renders mem unable to proliferate. After a 72-hour incubation, tritiated d ymidine was added to the mixed cell cultures, and incorporation of die labeled nucleotide into DNA was measured as an index of cell proliferation.

In one study, C3H mice were injected intraperitoneally widi either 1 or 10 mg purified TW extract/kg body weight. Animals were treated daily for 14 days prior to harvesting the spleen cells. Spleen cells from C3H mice were cultured wiϋi irradiated spleen cells from BalbC or C57 Black (C57B1) mice. Irradiated spleen cells from C3H mice served as controls.

Irradiated allogeneic spleen cells were found to stimulate C3H cell proliferation two- to four-fold, in comparison witii irradiated syngeneic cells. The extract effectively inhibi¬ ted die mixed lymphocyte response, and was dose dependent in the range 1-10 mg kg animal weight.

In a similar series of experiments, C3H mice were treated for 14 days widi 10 mg purified TW extract/kg body weight or wid diluent alone. Spleen cells were harvested and dieir response to the mitogens phytohemagglutinin (PHA) and concanavalin A (ConA) was assessed. A similar immunosuppressive effect by die extract was observed. ID. Formulations

In die immunosuppressant dierapy method of the invention, die TW extract or one or more purified TW compounds may be administered widi an immunosuppressant drug togedier in d e same formulation, or separately in separate formulations. Where separate formulations are used, die TW extract or compound and die immunosuppressant drug can be administered by different routes.

The immunosuppressant drug which is administered widi die TW compound is preferably one of die following:

(a) Cyclosporin A or cyclosporin C ("cyclosporin"), a non-polar cyclic oligopeptide; (b) FK506, a fungal macrolide immunosuppressant;

(c) aza iioprine, or 6-[(l-methyl-4-nitro-lH-immidazole-5yl)thio]lH-purine;

(d) me iotrexate,

(e) rapamycin, a fungal macrolide immunosuppressant;

(f) mycophenolic acid, or 6-(l,3-Dihydro-4-hydroxy-6-methoxy-7-medιyl-3-oxy-5- isobenzofuranyl)-4-methyl-4-hexanoic acid; and

(g) an immunosuppressant glucocorticoid, such as prednisone or dexamediasone. The proportions of die two components (TW extract/ compound and immunosuppressant drug) are preferably in die range of 1:50 to 50:1 by weight.

The TW extract/compound(s) and immunosuppressive drug may be administered to a subject orally, transdermally or parenterally, e.g., by intravenous, subcutaneous, intra- peritoneal, or intramuscular injection.

When die TW extract/compound and immunosuppressant drug are employed in die form of solid preparations for oral administration, die preparations may be tablets, granules, powders, capsules or die like. In a tablet formulation, the compound is typically formulated wid additives, for example, an excipient such as a saccharide or cellulose preparation, a binder such as starch paste or methyl cellulose, a filler, a disintegrator and so on, all being ones usually used in the manufacture of medical preparations.

For use in oral liquid preparation, die compounds/ drugs may be prepared as a liquid suspension, emulsion, or syrup, being supplied either in liquid form or a dried form suitable for hydration in water or normal saline.

The compounds/drugs may be injected in d e form of aqueous solutions, suspensions or oil or aqueous emulsions, such as liposome suspensions. Typically, for parenteral admi¬ nistration, die compounds/drugs are formulated as a lipid formulation, e.g., triglyceride, or phospholipid suspension. IV. Treatment Mediod

The TW compounds and immunosuppressant drugs of die invention are employed in immunosuppression d erapy, particularly in treating transplantation rejection.

According to an important feature of the invention, die effective dose of immunosuppressant drug is reduced significantly by coadministration (either concomitantly or separately) of the drug widi die purified TW compound, allowing higher drug doses to be administered and/or more prolonged treatment while reducing deleterious side effects.

In treatment mediod of die invention, die patient is given die TW extract or purified TW compound, and immunosuppressive drug in a pharmaceutically acceptable vehicle or vehicles on a periodic basis, e.g., 1-2 times per week at a dosage level sufficient to reduce symptoms and improve patient comfort. Where die TW extract or compound and immuno¬ suppressant drug are administered separately, they may be administered widi different dosing schedules as appropriate to maintain die potentiating effect of the TW compound on d e immunosuppressant compound. For oral administration, d e TW compound may be given in liquid, tablet or capsule form, at a preferred dose of 0.1 and 10 mg/kg patient body weight per day. The dose may be increased or decreased appropriately depending on die response of die patient, and patient tolerance.

A parenteral suspension can be administered by injection, e.g., intravenously, intramuscularly, or subcutaneously, inhalation, or uptake via a mucosal membrane. Where the TW compound is TW edianol extract, 16-hydroxytriptolide, triptolide, or tripchlorolide, a dose between about 0.05 and 1 mg/kg body weight per day is preferred, and this level may be increased or decreased appropriately, depending on die conditions of disease, die age of the patient, and the ability of the patient to resist infection. Where the TW compound is celastrol, salaspermic acid, triptonide, triptophenolide, wilforlide B, or tripdiolide, somewhat higher dosages may be necessary to achieve the immunopotentiating effect on die immunosuppressant drug.

Where die TW compound is 16-hydroxytriptolide, triptolide, or tripchlorolide, die dosage of TW compound is preferably effective to achieve a serum concentration of between about 10" and 10'⁷ M.

The dose of die immunosuppressant drug is typically 10%-75%, and preferably less dian 33%, of die dose diat would be administered when given in die absence of die TW compound, aldiough lower levels of immunosuppressant drug may be administered. For dierapy in transplantation rejection, die mediod is intended particularly for die treatment of rejection of heart, kidney, liver, and bone marrow transplants. The me iod is useful in the treatment inhibition of xenograft rejection as well as allograft rejection. The method is also useful in die treatment of graft-versus-host disease, in which transplanted immune cells attack die allogeneic host. The composition may be administered chronically to prevent graft rejection, or in treating acute episodes of late graft rejection.

Treatment is typically begun perioperatively and is typically continued on a daily dosing regimen, for a period of at least several weeks, for treatment of acute transplantation rejection. During the treatment period, the patient may be tested periodically for immuno- suppression level. Biopsy of die transplanted tissue may also be appropriate.

In accordance widi anodier embodiment of die invention, die immunosuppressant drug and TW extract compound(s) are administered separately. The immunosuppressant drug is administered in a ierapeutically effective dose, typically between about 20-75% of die normal dose for die drug alone. Drug administration is typically by oral or parenteral routes. The TW extract/compound is dien administered in an amount effective to potentiate die action of die immunosuppressant drug. Typically, die TW edianol extract is administered orally, at a dose in d e range 1-25 mg dried extract material/kg body weight.

A. Treatment/Inhibition of Allograft Transplant Rejection The treatment of transplantation rejection, in accordance widi die invention is illus¬ trated for rejection of an allograft by die heart transplantation model used in Example 7. The mediod involves a well-characterized rat model system (Ono and Lindsey, 1969) in which a transplanted heart is attached to die abdominal great vessels of an allogeneic recipient animal, and die viability of die transplanted heart is gauged by die heart's ability to beat in the recipient animal.

Fig. 5A illustrates die effect of treatment widi TW extract alone on allograft survival. As detailed in Example 7A, diree animal groups were treated with eidier (a) 5% alcohol solution (squares), (b) 10 mg/kg purified TW extract (1:10,000) administered daily by oral administration (circles), or (c) 10 mg/kg purified TW extract administered daily by intraperitoneal injection (triangles). There were diree animals in each group. Cardiac allograft survival was measured by the presence of detectable graft heart beat.

As seen from Fig. 5A, the heart grafts were rejected by the untreated recipient ani¬ mals following an average of 6.7 days. In die animals treated widi purified TW extract by oral administration, die allografts remained viable for 17 days, 3 days following discontinuation of treatment. In the animals treated widi purified TW extract by intraperitoneal injection, the allografts remained viable for an average of 21.3 days, one week after discontinuation of treatment. There was no evidence of toxicity in die treated animals. In a second study, transplant recipients were treated from one day preceding to 52 days following heart transplantation with (i) control solution (5% edianol, 10 ml kg), (ii) purified TW extract (1:10,000) (oral administration, 10 mg/kg), (iii) cyclosporin A (intraperitoneal (IP) administration, 0.75 mg/kg), or (iv) cyclosporin A (0.75 mg/kg) in purified extract (10 mg/kg), administered IP and PO, respectively. As seen in Fig. 5B, die control group (no drug or extract) had a mean graft survival time of 6.7 days. In die group treated widi die 10 mg/kg TW extract, mean graft survival increased to 11.8 days. Widi IP administration of cyclosporin A, mean graft survival time increased to 46.3 days, and diere was a small percentage of grafts surviving at 100 days. The most effective results were observed in treatment with die composition in accordance widi die invention, where mean graft survival time was 93.5 days, and half of die grafts survived to 100 days.

During the treatment period, only one graft was rejected in die group of recipient animals receiving both cyclosporin A and TW extract. In contrast, more dian one-half of die grafts failed in die group treated receiving cyclosporin A alone. According to an important feature, die invention provides a mediod for reducing die amount of immunosuppressive drug required to effectively extend allograft compatibility, by coadministering to die subject a TW edianol extract or purified TW compound. This is illustrated by die results shown in Fig. 6.

As detailed in Example 8, heart transplant recipient animals prepared were administered intraperitoneally (ip) various concentrations of cyclosporin A (CsA) alone or in combination widi a range of TW extract concentrations (2.5, 5, and 10 mg/kg/day) for a 16 day period beginning one day prior to transplant. Survival percentages were recorded 21 days after transplant.

With reference to Fig. 6, treatment wi i CsA at a dosage of 1.0 mg/kg/day is 100% effective in preventing allograft rejection after 21 days, whereas dosages of 0.5 and 0.25 of cardiac allografts yield survival rates of about 20 and 0%, respectively. However, including TW extract at 2.5, 5, and 10 mg/kg/day substantially reduces die amount of CsA needed for 100% survival, from 1 mg/kg/day CsA in die absence of TW extract to about 0.25 mg/kg/day CsA in die presence of 10 mg/kg/day TW extract. It will be appreciated tfiat by reducing die amount of CsA used, die mediod helps reduce or avoid die deleterious side-effects associated widi CsA dierapy.

Alternatively, die mediod of suppressing allografts may be practiced, in accordance widi die invention, by combining sub-direshold doses of an immunosuppression drug, such as cyclosporin A, widi a purified triptolide compound, e.g., obtained syndietically or isolated from T. wilfordii. Preferred triptolide for use in die mediod are d e ones illustrated in Figs. 3A, 3B, 3C, 3F, and 3G, and particularly 3B and 3C. The dose of immuno¬ suppressant drug used in die method is similar to that for treatment using TW extract, typically less than about 1/3 the dose normally required for immunosuppression when die drug is used alone.

B. Treatment/Inhibition of Xenograft Transplant Rejection

Inhibition of xenograft rejection was evaluated in a heart xenograft transplantation model (Example 9). These studies were carried out in die same manner as die allograft transplantation studies above, widi d e exception that die donor animals were hamsters

(Wang, 1991; Murase, 1993). As seen in Fig. 7A, treatment widi olive oil control solution resulted in a mean graft survival time of 3 days. Treatment widi cyclosporin alone (10 mg/kg IP) or TW extract alone (1:10,000, 30 mg/kg PO) each resulted in a mean graft survival time of about 4 days. In contrast, treatment widi cyclosporin A at 10 mg/kg, in combination widi die TW extract at 30 mg/kg resulted in 2 of die grafts surviving longer than 30 days.

Using anodier regimen, in which d e dose of cyclosporin A was reduced by half to 5 mg/kg, and die dose of TW extract doubled to 60 mg/kg, treatment widi olive oil alone (control) resulted in a mean graft survival time of 3 days (Fig. 6). Treatment widi cyclosporin alone (5 mg/kg IP) resulted in a mean graft survival time of 4.3 days.

Treatment with die TW extract alone (60 mg/kg PO) resulted in a mean graft survival time of 4.7 days. In contrast, treatment widi cyclosporin A (5 mg/kg) in combination widi TW extract (60 mg/kg) again resulted in 2 out of 3 grafts surviving longer than 30 days.

Similarly improved results are obtained using CsA in combination with the purified TW compounds tripchlorolide and triptolide, as illustrated by die plot in Fig. 8 (Example 10). As can be seen, treatment widi no drug, TW extract alone (30 mg/kg/day), or CsA alone (10 mg/kg/day) result in a survival time of about 4 days. Coadministration of CsA and azadiioprine leads to a slight improvement, widi 1 recipient surviving for 10 days. However, coadministration of CsA widi eid er tripchlorolide or triptolide provided a significant improvement in survival time relative to administration of eidier alone, widi all recipients surviving at least 31 and 34 days, respectively.

Example 11 describes a study showing mat coadministration of d e immunosuppressive drug, cyclosporin A, concurrently widi TW extract or a purified TW compound leads to suppression of anti-xenograft antibodies. In one study, xenograft recipients were treated widi no drug (control) TW extract (30 mg/kg/day), CsA alone (10 mg/kg/day), and TW extract (30 mg/kg/day) plus CsA at a lower dosage (5 mg/kg/day). Serum anti-xenograft antibodies (IgG and IgM) were measured until rejection, or until day 125 in the case of joint TW extract/CsA treatment. As can be seen from Figs. 9A and 9B (IgG and IgM, respectively), untreated recipients quickly develop high anti-xenograft antibodies widiin d e first 5 days following transplant, and d ese levels remained high for anodier 45 days. A similar increase is observed for treatment widi TW extract alone, except that rejection was complete by about day 6. Antibody measurements widi CsA alone are limited by rapid transplant rejection, which was complete by day 6. However, concurrent treatment widi TW extract and CsA is effective to almost completely suppress anti-xenograft antibodies during administration for 100 days. When administration of the TW/CsA combination is stopped, anti-xenograft antibodies develop within a few days.

Similar trends are observed when CsA is administered in combination wi i tripchlorolide or triptolide, as illustrated in Figs. 10A and 10B. The joint administration is accompanied by substantial suppression of anti-xenograft antibodies for die duration of administration.

C. Treatment/Inhibition of Graft Versus Host Disease

The invention includes a mediod of suppressing graft versus host disease (GVHD) rejection in a host subject. The mediod includes administering to the subject, an immuno¬ suppressant drug, such as cyclosporin A, FK506, azadiioprine, rapamycin, mycophenolic acid, a glucocorticoid, or a cyclophosphamide, where die drug or amount of drug administered is, by itself, ineffective to suppress GVHD rejection in die subject. A potentiator, which is eidier (i) an ethanolic extract of Tripterygium wilfordii or (ii) a purified triptolide component of die extract is administered in an amount effective to suppress GVHD rejection in die host in combination widi die immunosuppressant drug.

The invention also includes a mediod for treating GVHD, i.e., extending survival time in a host having a bone-marrow or spleen cell transplantation, by administering tripchlorolide to an animal in need of such treatment. The dose is preferably in die range 0.25-2 mg/kg body weight/day, preferably 0.5-1 mg/kg/day, given orally or parenterally.

Fig. 11 illustrates die ability of a combination of an edianolic TW extract and tripchlorolide (Fig. IC) to restore the concanavalin A proliferative response in GVHD mice. In this study, spleen cells were taken from mice after allogenic spleen cell transplantation (injected iv), and treatment widi various compositions over an 8 day period starting one day prior to grafting. The cells were stimulated to proliferate in culture in die presence of concanavalin A, and dien counted for proliferative activity. The mice treatments included oral administration of olive oil, tripchlorolide (T4, lmg/kg/day), or TW extract (B27, 75 mg/kg/day); and intraperitoneal (ip) administration of cyclosporin A in diluent (CSA, 75 mg/kg/day in ethanol/cremophore/saline, "ECS"), or diluent alone (ECS).

As seen from Fig. 11, tripchlorolide is as effective as the TW extract in preventing GVHD (as evidence by this conA restoration response), but at l/75dι die dose of die extract. The ability of tripchlorolide to extend survival in GVHD in mice after allogenic bone marrow transplant is shown in Fig. 12. In mis study, mice were given a ledial-dose radiation, men an allogenic bone marrow and spleen cell transplantation. Treatment was widi die various compositions and in die daily doses indicated in Fig. 12. As seen, long- term survival (greater man 240 days) was obtained widi tripchlorolide, at a level greater tiian 70% in animals treated widi 1 mg/kg/day of die compound, and at a level greater than 30% in animals treated widi 0.5 mg/kg/day of the compound. Long-term survival widi TW extract was seen at a level of greater dian 80%, but only at doses of 30 or 50 mg/kg/day.

The administration of tripchlorolide for GVHD, as widi any of e odier TW components noted above, can be combined widi administration of an immunosuppressant compound, including cyclosporin A, FK506, azathioprine, mediotrexate, rapamycin, mycophenolic acid, and a glucocorticoid. The immunosuppressant compound is preferably administered at a sub-direshold dose, i.e., a dosage level below diat effective to treat GVHD widi die drug alone.

The following examples are intended to illustrate, but in no way limit die scope of die invention. Example 1 Preparing Tripterygium wilfordii Edianol Extract Tripterygium wilfordii plants were obtained in Fujiang Province, China. Plants were air dried in sunlight. The root xylem of the plants (300 g) was ground into a crude powder and extracted widi 5 volumes (1.5 1) of 95% ethanol, under reflux at 85 °C for 4 hours. The filtered xylem powder was dien extracted two more times with 95% edianol (900 ml each time). The diree extracts (total of about 3.3 1) were combined and die resulting mixture was concentrated at 50°C under vacuum, to about 2% of the original volume, i.e., about 66 ml.

Example 2 Further Purifications of the TW Extract

A. The CH.C TW Extract

The edianol extract syrup obtained in Example 1 was men diluted widi 33 ml water, filtered ώrough Whatman #1 filter paper. The filtrate was extracted 4 times (50 ml/ex¬ traction) with methylene chloride (CH-CIJ.

B. The 1:1000 TW Extract

The combined, CH₂Cl₂-extract filtrate (about 200 ml) was concentrated, and applied to a 1 cm (diameter) x 5 cm column containing silica gel (1.5 kg; 60-200 mesh). The column was washed successively widi 100 ml me iylene chloride, and 100 ml mediylene chloride:methanol (95:5). The fraction which eluted in 95:5 solvent contained about 0.3 g material, and is referred to herein as a 1:1000 extract.

C. The 1:5000 TW Extract

Forty grams of 1:1,000 extract prepared as described above (in scale-up) was concentrated to a small volume in 20 ml acetone. The solution was applied to a 13 cm x 14 cm column containing silica gel (800 gm; 60-200 mesh) and eluted wid mediylene chloride:medιanol (97:3) to produce six 1 liter fractions. The yield of dried residue from each fraction was about 5% or 2 grams. Fractions 2-5 were combined and die resulting 8 grams of material are referred to herein as the 1:5000 TW extract. D. The 1:10.000 TW Extract

The 1:5000 TW extract was dien applied to an 8 cm x 40 cm column containing silica gel (320 gm; 260-400 mesh) and eluted with methylene chloride:methanol (97:3) to produce five 300 ml fractions. Fractions 2-4, which were yellowish in color, were com- bined. The solvent was removed by evaporation under vacuum to yield 4 grams of light brown powder, referred to herein as die purified (1: 10,000) TW extract.

Example 3 Thin-Laver Chromatography of Purified TW Extract One microgram samples of extracts were applied to a silica gel coated aluminum diin layer chromatography plate (Whatman, catalog #4420 222). The development solvent was hexane:methylene chloride: methanol in volume ratios of 1:1:0.15. Following separation, samples were visualized using an ultraviolet lamp and by application of an aerosol of 0.5% vanillin in H₂S0₄-emanol (4:1). TLC profiles of the various TW extracts are shown in Figure 2. Lane A shows the

1:1000 extract, lane B shows the 1:5000 extract and lane C die 1:10,000 extract, herein called die purified TW extract. It can be seen diat purification between die 1:1000, 1:5000 and 1:10000 extracts has removed a number of major plant components. For diese TW extracts, the diin layer chromatographic profile showed no alkaloid in die extract, as determined by application of die Dragendorff reagent.

Example 4 Suppression of Stimulated PBL Proliferation in Vitro Human peripheral blood lymphocytes were prepared using an established mediod (Boyum, 1968). Human blood buffy coat samples, approximately 40 ml/donor, were obtained from the Stanford University Medical Center Blood Bank. Using sterile technique, die buffy coat samples were gently resuspended in a total volume of 100 ml widi die addition of calcium and magnesium free Hank's balanced salt solution (HBSS, obtained from Gibco) at 24°C. A volume of 25 ml of the cell suspension was tiien layered onto 15 ml of Ficoll-Paque (Pharmacia LKB Biotechnology, Inc.) in a 50 ml conical centrifuge tube. Tubes were centrifuged in a Beckman GPR tabletop centrifuge (GH-3.7 Rotor) at 400 x g for 30 minutes at 15°C with die brake "off" to prevent disruption of die PBL interfaces. Following centrifugation, die PBL interfaces were transferred to new 50 ml tubes using a transfer pipette, and die PBL samples were resuspended in a total volume of 45 ml HBSS and centrifuged at 354 x g for 10 minutes at 15 °C with die brake on "low" setting. Supernatants were discarded. PBL's were resuspended in 10 ml HBSS, combined to make a total of 45 ml HBSS, and centrifuged at 265 x g for 10 minutes at 15 °C widi the brake on "low" setting. The cell pellets were suspended in 10 ml of X-Vivo tissue culture medium (Bio Whittaker) and counted using a hemocytometer. Tissue culture medium was dien added to achieve a final cell concentration of lxlO⁶ cells/ml. Additional dilutions were carried out as required for each assay.

Assays were carried out in 96 well sterile tissue culture plates (Costar 3790, U-bottom and Costar 3595, flat bottom). A volume of 150 μl of X-Vivo medium or sterile distilled water was added to die outer wells of the plate to prevent evaporation of medium wi iin die experimental wells. PBL's from 2 different donors were used in parallel in all experiments. A volume of 100 μl PBL suspension was added to each well using a multichannel pipette. Plates were incubated in an atmosphere of 93% air/7% CO2 in a tissue culture incubator at 37°C. X-35 (AMAC #0178), an anti CD-3 surface antigen antibody was used at 5 ng/ml to stimulate PBL proliferation.

The purified TW extract was diluted in edianol (10 mg/ml) and then in sterile X-Vivo tissue culture medium to obtain die final concentrations required for each experiment.

After 68 hours total incubation time, 50 μl of X Vivo tissue culture medium containing 8 μCi/ml [³H]-dιymidine (Amersham, 49 Ci/mmol) was added to each tissue culture well. Following four hours additional incubation at 37°C, die cells were removed from me tissue culture wells and applied to filter paper using a cell harvester (Brandel). The filter paper was dried for one hour under a heat lamp and dien cut into 1 cm discs. Each sample was placed in a scintillation vial containing 2 ml of scintillation fluid (Biosafe, Research Products International Corp.). Samples were counted in a Beckman LS 6000SC scintillation counter. Increasing amounts of purified TW extract produced dose-dependent inhibition of proliferation in bodi stimulated and unstimulated cells, in a concentration range of 0.3-1.25 μg extract components/ml culture medium. At a concentration of 1.25 μg/ml, die extract reduced unstimulated PBL proliferation 36-fold, and reduced stimulated PBL proliferation 860-fold. Example 5 Effect of Purified TW Extract on Cytokine Production The ability of the purified T. wilfordii extract to affect die production of IL-1, TNF- α, IL-2, and IL-6, cytokines secreted by anti-CD3 antibody-stimulated (X-35 antibody, 5 ng/ml) and unstimulated human PBLs, was measured.

PBLs were prepared, incubated and treated as described in die preceding example. The purified (1: 10,000) TW extract was used at 5 μg/ml. Samples of tissue culture medium were collected at die end of 24 hours incubation and stored at -70°C prior to assay.

Cytokine measurements were carried out using commercially available ELISA assay kits (R&D Systems), in accordance widi die supplier's protocols. In brief, 100 μl of die assay buffer supplied was added to each of die wells of a microtiter plate containing pre-bound anti-cytokine antibody, followed by 100 μl of standard or sample solution, diluted appropriately for the concentration range measured. All incubations were carried out at 37^CC or 24°C. Following two hours incubation, the plates were washed four times widi assay buffer, and die second antibody, anti-cytokine labeled widi horseradish peroxidase (HRP), was added to each well in a volume of 200 μl. Following a second 2 hour incubation, the wells were washed four times with buffer, and 200 μl of HRP substrate was added to the wells. After 20 minutes incubation, the reaction was terminated by addition of 50 μl H₂SO₄ to each well. Optical density was determined using a Molecular Devices microtiter plate reader.

As shown in Figure 3, basal levels of IL-1, TNFa, IL-2 and IL-6 increased markedly (3.8 to 167 pg/ml, 30.9 to 655 pg/ml, 7.6 to 149 pg/ml, and 109 to 2650 pg/ml, respectively) with X-35 stimulation. At a concentration of 5 μg/ml, die purified TW extract inhibited tiiis X-35 stimulated increase by 16, 89, 93 and 100%, respectively. The extract most likely inhibits cytokine production, though the decrease in medium cytokine concentration could dieoretically result from increased catabolism. Decreased cytokine production may be responsible, at least in part, for die decrease in PBL proliferation in vitro and for die immunosuppressive effect of die extract in vivo.

Example 6

Cytotoxicity of Extract Potential cytotoxicity of the purified TW extract (1:10,000) was assessed by measurement of the extract's effect on the ability of cultured cells to reduce MTT (3-[4,5-Di- methyldιiazol-2yl]-2,5-diphenyltetrazolium bromide). MTT, a yellow-colored compound, is reduced by mitochondrial enzymes to form a purple crystalline reduction product (formazan), providing an index of cellular respiration as well as a sensitive assay for cytotoxicity (Green, 1984).

Cytotoxicity was assessed in bodi cultured PBLs and diymocytes. A stock solution of MTT (Sigma Chemical Co. , St. Louis, MO), 5 mg MTT/ml phosphate buffered saline, Ph 7.4, was prepared and stored in d e dark at 4°C. Following 21 hours incubation under conditions identical to those used in die assays, 25 μl of MTT solution was added to each culture well. After an additional 3-hour incubation, die experiment was terminated by addition of a solution of 10% sodium dodecyl sulfate in 0.01 N HC1. Following overnight incubation at 37°C (to solubilize the purple crystals, die MTT reduction product), optical density was determined at 570-650 nm in a Molecular Devices microtiter plate reader. Data are expressed as die ratio of d e optical density of die extract treated sample to that of untreated controls.

Example 7 Treatment of Heart Transplant Rejection

Heterotopic whole heart transplantation was performed according to die standard method (Ono, 1969). The donor (Brown Norway rats, 200-255g, Charles River, Wilmington, MA) and die recipient (Adult male Lewis rats, 225-275g, Charles River) were anesdietized widi sodium pentobarbital (40 mg/kg). Following adequate donor anticoagulation using heparin, die heart graft was removed and stored at 4°C in PhysioSol Irrigation Solution (Abbott Laborato¬ ries, N. Chicago, IL). The ascending aorta and pulmonary artery were transected, and die vena cava and pulmonary veins were ligated. The recipient abdominal aorta and inferior vena cava were exposed d rough a median abdominal incision. The donor heart aorta and pulmonary artery were anastomosed end-to-side to recipient's infrarenal abdominal aorta and inferior vena cava, respectively, widi running 8-0 monofilament nylon suture (Ediilon, Inc. , Somerville, NJ). Because of die functional properties of die aortic valve, blood did not enter die left ventricle but radier flowed dirough die coronary arteries to die right atrium, pulmonary artery and the recipient vena cava. The cold ischemic time of all me cardiac grafts was less dian 45 minutes. Graft heartbeat was monitored by abdominal palpation. The period of functional graft survival was measured as die number of days during which cardiac graft contractions could be detected by abdominal palpation. Results were confirmed by direct visualization at laparotomy. A. Treatment widi TW Extract

Heart transplant recipient animals prepared as just described (3 animals/group) were treated for 14 days widi TW extract (1:10,000, 10 mg/kg) or widi edianol solution (5% edianol, 10 ml/kg), starting on die day prior to surgery and dien daily. The TW extract was administered both orally and by intraperitoneal injection. Each heart graft recipient was followed until die graft ceased beating. The results are shown in Fig. 5A, discussed above.

B. Treatment of Allograft Recipient widi Cyclosporin/TW Extract Composition

Heart transplant recipient animals prepared as described above (3-10 animals/group) were treated with (i) control solution (5% edianol, lOml/kg), (ii) purified (1:10,000) extract

(oral administration, 10 mg/kg), (iii) cyclosporin A (intraperitoneal (IP) administration, 0.75 mg/kg), or (iv) cyclosporin A (0.75 mg/kg) in purified extract (1: 10,000, 10 mg/kg), administered IP.

The treatment methods started on die day prior to surgery and continuing daily until postoperative day 52, or until die end of allograft survival. Each graft recipient was followed until die graft ceased beating. The results are seen in Fig. 5B, discussed above.

Example 8 Treatment of Allograft Rejection widi CsA and TW Extract

Heart transplant recipient animals prepared as described in Example 7 were administered intraperitoneally (IP) for 16 days starting one day before transplant widi (a) cyclo¬ sporin A (CsA) alone at 0.25, 0.5, and 1 mg/kg/day; (b) CsA at 0.12, 0.25, and 0.5 mg/kg/day with TW (1:10,000) edianol extract at 2.5 mg/kg/day; (c) CsA at 0, 0.25, and 0.5 mg/kg/day with TW (1:10,000) ethanol extract at 5 mg/kg/day; and (d) CsA at 0 and 0.25 mg/kg/day widi TW (1:10,000) edianol extract at 10 mg/kg/day. Survival percentages were recorded 21 days after transplant. The results are shown in Fig. 6.

Example 9 Treatment of Heart Xenograft Rejection

Heterotopic whole heart transplantation was performed according to die standard method (Ono, 1969). Donor hearts were obtained from Golden Syrian hamsters, (100-150 g, Charles River Laboratories, Wilmington, MA). This is a standard model for xenograft transplantation rejection (Wang, 1991; Murase, 1993). The remainder of die procedure was identical to diat used in Example 7 A, above.

Transplant recipients (3 or 4 animals/group) were treated widi (i) control (olive oil, 1 ml/kg), (ii) purified (1:10,000) extract (oral administration, 30 or 60 mg/kg), (iii) cyclosporin A (intraperitoneal administration, 5 or 10 mg/kg), or (iv) cyclosporin A (50 or 10 mg/kg PO) and purified (1:10,000) extract (60 or 30 mg/kg).

The treatment methods started one day prior to transplantation and continued until die time of graft rejection. Each graft recipient was followed until die graft ceased beating. The results are shown in Figs. 7 A and 7B.

Example 10 Treatment of Heart Xenograft Rejection Widi CsA and TW Materials Heart xenograft recipients prepared as in Example 9 (3 to 6 animals/group) were treated widi the following treatment regimens: (a) no drug (control, n=3);

(b) TW extract, 30 mg/kg/day (n=6) until rejection;

(c) CsA, 10 mg/kg/day (n=3) until rejection;

(d) azathioprine, 30 mg/kg/day, plus CsA, 10 mg/kg/day (n=3), for days 1 to 7, 5 mg/kg/day of CsA alone for days 8 to 10*; (e) tripchlorolide, 0.25 mg/kg/day, plus CsA, 10 mg/kg/day (n=3), for days 1 to 7,

5 mg/kg/day of CsA alone for days 8 to 50; and

(f) triptolide, 0.25 mg/kg/day, plus CsA, 10 mg/kg/day (n=3), for days 1 to 7, 5 mg/kg/day of CsA alone for days 8 to 50. The results are shown in Fig. 8.

Example 11 Effect of Treatment on Anti-Xenograft Antibody Levels Heart xenograft recipients prepared as in Example 9 (3 to 7 animals/group) were treated as indicated below. Lytic antibody titers (IgG and IgM) were measured in die sera of die recipient rats, using hamster red blood cells as targets and baby rabbit serum as a source of complement. Cell lysis was assayed by hemoglobin release into complement fixation diluent as measured with a spectrophotometer (Hasan et al., 1992; Van den Bogaerde et al., 1991). The regimens tested were as follows: Group A (TW extract study): (a) no drug (control, n=3); (b) TW extract (1:10,000), 30 mg/kg/day (n=6) until rejection; (c) CsA, 10 mg/kg/day (n=3) until rejection; and (d) TW extract (1:10,000), 30 mg/kg/day, plus CsA, 5 mg/kg/day (n=7), for days -1 to 100. The results are shown in Figs. 9 A and 9B. Group B (tripchlorolide and triptolide study): (a) no drug (control, n=3, from Group

A); (b) tripchlorolide, 0.25 mg/kg/day, plus CsA, 10 mg/kg/day (n=3), for days -1 to 7, 5 mg/kg/day of CsA alone for days 8 to 50; and (c) triptolide, 0.25 mg/kg/day, plus CsA, 10 mg/kg/day (n=3), for days -1 to 7, 5 mg/kg/day of CsA alone from day 8 until rejection complete. The results are shown in Figs. 10A and 10B.

Although die invention has been described with respect to particular methods and applications, it will be appreciated mat various changes and modifications may be made widiout departing from the spirit of me invention.

Claims

IT IS CLAIMED:

1. In a method of suppressing allograft rejection in a host subject, by administering to die subject an immunosuppressant drug selected from die group consisting of cyclosporin A, FK506, azathioprine, rapamycin, mycophenolic acid, and a glucocorticoid, the improvement comprising administering to die subject, a potentiator selected from the group consisting of (i) an eύianolic extract of Tripterygium wilfordii and (ii) a purified triptolide component of said extract, in an amount effective to significantly reduce the amount of die immunosuppressive drug required to effectively suppress allograft rejection in die host subject, in combination widi die immunosuppressive compound.

2. The improvement of claim 1, wherein me immunosuppressive drug is cyclosporin A.

3. The improvement of claim 1, wherein the potentiator is an ethanolic extract of Trypterygium wilfordii, and the extract is administered in an amount effective to reduce die effective suppressing amount of cyclosporin A by a factor of at least 3.

4. The improvement of claim 3, wherein the immunosuppressive drug is cyclosporin

A.

5. The improvement of claim 1, wherein the potentiator is a purified triptolide component selected from the group consisting of 16-hydroxytriptolide, triptolide, and trip- chlorolide.

6. The improvement of claim 1, wherein said immunosuppressive drug and potentiator are bodi administered at regular intervals over a time period of at least 2 weeks.

7. The improvement of claim 1, wherein the immunosuppressive compound and potentiator are administered parenterally.

8. The improvement of claim 1, wherein the immunosuppressive compound and potentiator are administered orally.

9. A method of suppressing allograft rejection in a host subject, comprising administering to the subject, an amount of cyclosporin A that is less dian about 1/3 die dose needed to effectively suppress such rejection in die host, when cyclosporin A is administered alone, and administering a potentiator selected from the group consisting of (i) an ethanolic extract of Tripterygium wilfordii and (ii) a purified triptolide component, in an amount effective to suppress allograft rejection in die host, when administered in combination with die immunosuppressive compound.

10. A mediod of suppressing xenograft rejection in a host subject, comprising administering to the subject, an immunosuppressant drug selected from die group consisting of cyclosporin A, FK506, azadiioprine, rapamycin, mycophenolic acid, a gluco¬ corticoid, and cyclophosphamide, where the immunosuppressant drug or amount of drug administered is, by itself, ineffective to suppress xenograft rejection in the subject, and administering to the subject a potentiator selected from die group consisting of (i) an edianolic extract of Tripterygium wilfordii and (ii) a purified triptolide component, in an amount effective to suppress allograft rejection in die host in combination widi die immunosuppressant drug.

11. The mediod of claim 10, wherein die immunosuppressive drug is cyclosporin A.

12. The method of claim 10, wherein die potentiator is an edianolic extract of Trypterygium wilfordii.

13. The mediod of claim 10, wherein die potentiator is a purified triptolide component selected from the group consisting of 16-hydroxytriptolide, triptolide, and tripchlorolide.

14. The method of claim 10, wherein said immunosuppressive drug and potentiator are bo administered at regular intervals over a time period of at least 2 weeks.

15. The method of claim 10, wherein die amount of immunosuppressant drug administered is between about 20% and 100% of die amount of drug needed to suppress allograft rejection in die host, when administered alone.

16. The mediod of claim 10, wherein the immunosuppressant drug and die potentiator are administered parenterally.

17. The method of claim 10, wherein the immunosuppressant drug and die potentiator are administered orally.

18. A method of suppressing graft versus host disease in a host subject, comprising administering to the subject, an immunosuppressant drug selected from die group consisting of cyclosporin A, FK506, azadiioprine, rapamycin, mycophenolic acid, a gluco- corticoid, and cyclophosphamide, where die drug or amount of drug administered is, by itself, ineffective to suppress xenograft rejection in the subject, and administering to the subject a potentiator selected from the group consisting of (i) an edianolic extract of Tripterygium wilfordii and a (ii) purified triptolide component of said extract, in an amount effective to suppress graft-versus-host disease in die host in combination wi the immunosuppressant drug.

19. The method of claim 18, wherein the immunosuppressive drug is cyclosporin A.

20. The mediod of claim 18, wherein the potentiator is an edianolic extract of Trypterygium wilfordii.

21. The method of claim 18, wherein the potentiator is a purified triptolide component selected from the group consisting of 16-hydroxytriptolide, triptolide, and tripchlorolide.