WO1991013624A1

WO1991013624A1 - Endogenous, suramin-induced, sulfated glycosaminoglycans as anti-cancer agents in humans

Info

Publication number: WO1991013624A1
Application number: PCT/US1991/001235
Authority: WO
Inventors: Renato V. Larocca; Cy Aaron Stein; Charles E. Myers; Michael R. Cooper
Original assignee: The United States Of America, As Represented By The Secretary, U.S. Department Of Commerce
Priority date: 1990-03-05
Filing date: 1991-03-04
Publication date: 1991-09-19
Also published as: AU7478191A

Abstract

Methods are disclosed for the treatment of cancers in humans utilizing endogenous suramin-induced sulfated glycosaminoglycans (GAGs). Pharmaceutical injectable compositions containing the sulfated GAGs are also disclosed, and a method of isolating endogenous suramin-induced sulfated GAGs from a patient being treated with suramin, is also provided.

Description

ENDOGENOUS, SURAMIN-INDUCED, SULFATED GLYCOSAMINOGLYCANS AS

ANTI-CANCER AGENTS IN HUMANS FIELD OF THE INVENTION The present invention relates to the anti-cancer activities of sulfated glycosaminoglycans (GAGs) which are endogenous to humans and which are induced by the administration of suramin to humans, and methods of treating humans for cancers therewith.

BACKGROUND OF THE INVENTION International Patent Application WO 86/02266 of

Yarchoan et al discloses a method for the clinical or therapeutic treatment for the relief of illnesses caused by human T cell leukemia virus (HTLV) by the intravenous

. administration of Suramin. International Application WO 86/02266 of Yarchoan et al is hereby incorporated by reference.

U.S. Patent Application Serial Number 07/321,055 of

Stein et al, filed on March 9, 1989, discloses a general method for treating cancer in a patient by administering Suramin Sodium to a patient so that Suramin serum levels are maintained between about 50 to 300 mcg/ml. U.S.

Patent Application Serial Number 07/321,055 of Stein et al, filed on March 9, 1989, is hereby incorporated by reference. It has been reported that Suramin can inhibit the lyso-somal enzyme iduronate sulfataze, which in turn induces an accumulation of tissue glycosaminoglycans

(Constantopoulos et al, Experimental Animal Model for

Mucopolysaccharidosis: Suramin-inducedGlycoasminoglycan and Sphingolipid Accumulation in the Rat, Proc. Natl.

Acad. Sci. USA 1980; 77:3700-3704). It has also been reported that an elevation in circulating levels of glycosaminoglycans appears to be responsible for the development of an anticoagulated state seen in patients treated" with . Suramin (Home et al, Circulating Glycosaminoglycan Anticoagulants Associated With Suramin Treatment, Blood 1988; 71:273-279).

None of the above references disclose that Suramin- induced sulfated GAGs in humans possess anti-cancer activity or disclose a method for the isolation of Suramin-induced sulfated GAGs from humans. SUMMARY OF THE INVENTION

One object of the present invention is to provide for elevating levels of sulfated glycosaminoglycans (GAGs) in human patients having cancers susceptible to the anti- pro-liferative effect of such GAGs. A second object of the present invention is to provide for a method of isolating sulfated GAGs from a human patient treated with suramin. A third object of the present invention is to provide a method for treating cancers, by administering to a patient effective amounts of purified human endogenous sulfated GAGs for treating cancers, susceptible to treatment therewith. A fourth object of the present invention is to provide pharmaceutical compositions for administering such GAGs to a patient by injeσtion. The above objects of the present invention may advantageously be achieved with the use of the following methods.

1. A method of treating cancer in a human patient, the cancer treated being susceptible to treatment with an endogenous suramin-induced sulfated glycosaminoglycan, the method comprising, achieving in said patient an effective plasma level of said glycosaminoglycan for treating the cancer.

2. The method of paragraph 1, wherein said plasm level of said glycosaminoglycan is achieved in one of the following manners:

(a) by the administration of Suramin or a pharmaceutically acceptable salt thereof, by in¬ jection to the patient, and the administration of said glycosaminoglycan or a pharmaceutically acceptable salt thereof, in a purified form by injection to the patient; or

(b) by the administration of said glycosaminoglycan in a purified form by injection to the patient. 3. The method of paragraph 1 or 2 , wherein the glycosaminoglycan is: heparan sulfate; dermatan sulfate; a chondroitin sulfate; or keratan sulfate.

4. A process for isolating a pharmaceutically acceptable salt of a desired endogenous suramin-induced glycosaminoglycan (GAG) from a patient's urine, the process comprising: (a) collecting the urine of a patient having a suramin plasma level of about at least 50 mcg/ml;

(b) separating the collected urine on a suitable anion-exchange chromatography column, to give a first GAG containing product; (c) digesting the first sulfated GAG containing product with a suitable proteolytic degradative enzyme, to give a second sulfated GAG containing product; (d) separating the second sulfated GAG containing product on a suitable anion exchange chromatography column to give a third sulfated GAG containing product; and (e) digesting the third sulfated GAG containing product with a suitable polysaccharide lyase enzyme, to give a fourth sulfated GAG containing product; alternatively performing step (f) or (f") ,

(f) separating the fourth sulfated GAG containing product on a suitable anion exchange chromatography column, to give the sodium salt of the desired engogenous suramin-induced GAG,

(f^H) separating the fourth sulfated GAG containing product on a suitable gel permeation column, to give the ammonium salt of the desired endogenous suramin-induced GAG; and

(g) optionally converting the obtained salt of the desired GAG to another pharmaceutically acceptable salt. 5. A pharmaceutical composition for injection, comprising: an effective amount of a pharmaceutically acceptable salt of an endogenous suramin-induced sulfated glycosaminoglycan or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable carrier therefor. The following Glossary of Terms is provided in order to remove any ambiguity which may exist as to the meanings of certain terms as used herein. The term "suramin sodium" as used herein means the commercially available compound 8,8'-[carbonylbis[imino- 3 , 1-phenylenecarbonylimino (4-methyl-3 , 1- phenylene) carbonyl-imino ] ] b i s - 1 , 3 , 5 - naphthalenetrisulfonic acid hexasodium salt. A method for its preparation can be found in Great Britain Patent 224,849 (1929) . The compounds therapeutic categories, include utility as an anti-cancer agent, an HIV inhibitor, as an antitrypanosomal and antifilarial agent. The term "endogenous suramin-induced sulfated glycos¬ aminoglycans" as used herein, refers to glycosaminoglycans (GAGs) having 0.1 to 3 sulfate groups per each di-saccharide moiety, which are endogenous to humans or other animals, which possess anti-cancer activity (an anti-proliferative effect on cancer cells susceptible thereto) , and which accumulate in a patient's body when treated with suramin in a cancer treatment regimen. The term is meant to include such GAGs endogenously produced in humans or other animals, isolated from human urine (or other body fluids, tissues or organs) , chemically synthesized, or engineered through biotechnological means and methods. The term "cancer" as used herein, unless otherwise quali-fied as a specific type of cancer, includes cancers such as: all lymphoproliferative malignancies including Hodgkin's Disease, non-Hodgkin*s lymphoma, multiple myeloma and B and T-cell malignancies; prostate cancer; cancer of the colon; cancer of the rectum; breast cancer; lung cancer, melanoma, glioma and sarcomas; and the like.

The term "plasma" as used herein refers to whole blood plasma having cell bodies spun out by centrifugation, or similar method. Exemplary of suitable methods which may be utilized to obtain plasma, and furthermore to quantify suramin concentration levels therein, is that of R. Klecker and J. Collins, J. Liσ. Chromatoσ.. Vol. 8, pp. 1685-1696 (1985), hereby incorporated by reference. Exemplary of a method for quantifying the amount of endogenous suramin-induced sulfated GAGs present in plasma, is that of Blumenkrantz and Asboe-Hansen, Analytical Biochemistry, 54, PP- 484- 489 (1973) , hereby incorporated by reference.

The term "heparan sulfate" as used herein refers to an endogenous sulfated GAG in humans which is a heteropolysaccharide resembling heparin, but which consists of a repeating disaccharide of sulfated D- glucuronic acid and D-glucosamine. Heparan Sulfate is also known in the literature as "heparitin sulfate".

The term "dermatan sulfate" as used herein refers to an endogenous sulfated GAG found in humans, which is a mucopolysaccharide containing L-iduronic acid and N- acetyl-D-galactosamine. Dermatan sulfate was formerly known in the literature as chondroitin sulfate B.

The term "chondroitin sulfate" as used herein refers to an endogenous sulfated GAG in humans which is a mucopolysaccharide containing galactosamine and glucuronic acid.

The term "pharmaceutically acceptable carrier" as used herein means any carrier suitable for use in an injectable composition which is acceptable for parenteral administration and is compatible with the endogenous sulfated GAG administrated. Exemplary of such carriers are purified water USP, Arachis oil, and the like.

The term "pharmaceutically acceptable salt" as used herein includes appropriate addition salts, alkali metal salts (sodium potassium, etc) , hydrates, alcolates and quaternary salts of the sulfated GAGs, disclosed herein, which salts are physiologically compatible in man. Detailed Description of the Invention

The present invention is concerned with the use of en-dogenous suramin-induced sulfated glycoaminoglycans (GAGs) in methods of treating cancers and pharmaceutical compositions containing such suramin-induced sulfated GAGs. The present invention is based on a discovery that the sulfated GAGs induced in patients who are administered suramin, possess anti-cancer activity. The suramin-induced sulfated GAGs useful in the present invention are termed "suramin-induced", due to elevated levels of the same occurring in patients treated with suramin. Elevated levels of these sulfated GAGs in suramin-treated patients, are thought to occur as a result of suramin's ability to inhibit the lysosomal enzymes responsible for the catabolism of GAGs. As such, it is considered that suramin does not aid in the production of GAGs in a patient's system, but aids in the accumulation of sulfated GAGs in a suramin-treated patient's body. Due to the accumulation of sulfated GAGs in a suramin-treated patient system, the present inventors conjectured that elevated levels of the sulfated GAGs might be excreted in a suramin-treated patient's urine. Based on this con-jecture, a novel process was developed for isolating GAGs contained in a suramin-treated patient's urine. Utilizing the novel process, the present inventors discovered that suramin-treated patients can experience a 4-5 fold increase in the excretion of GAGs when treated with suramin. Among the suramin-induced sulfated GAGs found to be excreted in high yield by the present inventors, were heparan sulfate and dermatan sulfate. Also present were chondroitin sulfate and keratan sulfate, among others.

The discovery of an isolation method for recovering such GAGs from a suramin-treated patient's urine is especially fortuitous, since it has been additionally discovered that such GAGs possess anti-cancer effects and are thus useful in treating patients having cancer.

Even though one aspect of the present invention is concerned with methods of isolating suramin-induced GAGs from a suramin-treated patient's urine, it is noted that other methods could be utilized to obtain endogenous suramin-induced sulfated GAGs in purified form, which sulfated GAGs would be useful in the methods provided herein for treating cancers in a patient, and the pharmaceutical compositions herein taught. It is considered that such suramin-induced sulfated GAGs, would be effective in the cancer treating methods, and pharmaceutical compositions disclosed herein, whether the same are isolated from urine, or some other human produced substance (e.g., tissue, organ or luid), chemically synthesized or are biologically engineered through the use of recombinant DNA technology. As such, it is considered that the present inventive process for obtaining suramin-induced sulfated GAGs should not be deemed to limit the cancer treating methods herein disclosed, or the cancer treating compositions herein disclosed. This is especially true, since the term "endogenous suramin-induced sulfated GAG" as used herein, simply refers to those sulfated GAGs which occur in a patient, and which are accumulated when suramin is administered, and which possess anti-cancer activity.

In order to better describe the present invention, and the different embodiments thereof, the following discussion is divided into three sub-sections. The sub¬ sections are titled as follows:

I. Isolation Method for Sulfated GAGs; II. Anti-Cancer Effects of Endogenous Sulfated GAGs; III. Pharmaceutical Compositions. I. Isolation Method for Sulfated GAGs

In the present invention there is provided a method for the isolation of suramin-induced sulfated GAGs from the urine of a patient treated with suramin. The method steps utilized are outlined in the Summary of the Invention Section above, but are discussed more fully here.

In the novel isolation method disclosed herein, there are recited steps (a) - (e) , (f), (f") and (g) . However, steps (f) and (f") are alternate steps, and only one of the two need be performed to isolate the desired GAG.

In step (a) of the isolation method herein disclosed, urine is collected from a patient having a plasma suramin level of about at least 50 mcg/ l. In order to achieve such a suramin plasma level, one could, for example, administer suramin to a patient as disclosed by either Stein et al in U.S. Patent Application Serial Number 07/231,055 or as disclosed by Yarchoan et al in Inter- national Patent Application WO 86/02266. Furthermore, suitable methods for achieving such plasma suramin levels could include slow i.v. administration of suramin, or the use of serial bolus injections of suramin. In this regard, it is noted that achievement of serum suramin levels through the use of a single large bolus injection is not thought practical or advantageous to utilize, since in such cases, suramin-plasma levels of > 300 mcg/ml may be obtained, which can produce toxic effects in a patient. The methods taught by both Yarchoan et al and Stein et al, can easily be used to achieve and maintain suramin-plasma levels of about 50 mcg/ml to about 300 mcg/ml in a patient.

After collecting the urine from a patient treated with suramin, the urine is separated on a suitable anion- ex-change chromatography column in step (b) of the inventive isolation method herein disclosed. A suitable anion-ex-change chromatography column to utilize would be similar to that disclosed in Example 1 below (i.e., a column containing Q-Sepharose from Pharmacia) . It is additionally noted, that appropriate eluting solvents would be generally understood to those skilled in the art, based upon those utilized in Example 1 below and those generally recognized as appropriate by those skilled in the art. Upon separation in the anion- exchange chromatography column in step (b) of the method, there is obtained a first sulfated GAG containing product. The sulfated GAG containing product obtained is digested in step (c) of the inventive method.

In step (c) of the inventive method, the first sulfated GAG containing product obtained in step (b) is digested with a suitable proteolytic enzyme to give a second sulfated GAG containing product. A suitable proteolytic enzyme to utilize in step (c) would include papain (such as that utilized in Example 1 below) or any other such enzyme generally recognized by those skilled in the art to be appropriate. After degradation of the first sulfated GAG containing product in step (c) to give the second sulfated GAG product, the second product is subjected to a separation step on a suitable anion- exchange chromatography column in step (d) .

In step (d) , the second sulfated GAG containing product is separated on a suitable anion-exchange chromatography column, in order to obtain a third sulfated GAG containing product. A suitable column to perform such a task would be generally known to those skilled in the art, and may be of the same type employed in step (b) , or it may be different. Likewise, appropriate eluting solvents should be readily understood by those skilled in the art and may be the same as provided in step (b) above.

In step (e) of the process, the third sulfated GAG con-taining product is digested with a suitable polysaccharide lyase enzyme to give a fourth sulfated GAG containing product. A suitable polysaccharide lyase enzyme for utilizing in step (e) would be chondroitinase ABC (used in Example 2 below) or any other such enzyme generally recog-nized by those skilled in the art to be appropriate. The fourth sulfated GAG containing product obtained in step (e) is separated in one of alternative steps (f) or (f") as desired.

In step (f) of the process, the fourth sulfated GAG containing product is separated on an appropriate anion- ex-change chromatography column. The column utilized may be the same or different as one utilized in step (b) or (d) . A suitable column to utilize would be readily under-stood by those skilled in the art, as would suitable eluting solvents. Upon separation in step (f) of the process, there is obtained the desired sulfated GAG in an isolated form as the sodium salt. The sodium salt thus obtained may be optionally converted to another pharmaceutically acceptable salt in step (g) , if so desired.

In step (f") of the process (an alternate step to step (f^l)) , the fourth sulfated GAG containing product is separated on a suitable gel permeation column. A suitable column would contain a gel such as used in Example 1 below (TSK-GEL HW-40S) , or the like. The choice of a suitable gel column and appropriate eluting solvents should be readily understood by those skilled in the art. Upon separation in the gel permeation column, there is obtained the ammonium salt of the desired sulfated GAG, in an isolated form. The ammonium salt of the sulfated GAG may be optionally converted to another pharmaceutically acceptable salt in step (g) , if desired.

In step (g) of the process, the obtained salts of the sulfated GAGs are optionally converted to other pharmaceutically acceptable salts. Such a method is readily understood by those skilled in the art and would include for example, partitioning between a dilute aqueous acid and a suitable solvent to obtain the free acid of one of the sulfated GAGs, which is then reacted with a suitable base, alkali metal, etc. for obtaining the desired pharmaceutically acceptable salt.

With the above-described isolation method, there are obtainable purified suramin-induced sulfated GAGs in the form of pharmaceutically acceptable salts from a patient's urine. The thus obtained GAGs being useful in the pharmaceutical compositions and cancer treatment methods herein taught.

To aid in further description of the isolation method described above, the following Example 1 is provided. Example 1

Twenty-four hour urine samples are collected from patients with a variety of malignancies, upon completion of a cycle of drug (suramin) infusion. The urines are stored in 0.02% NaN₃ at 4 degrees Celsius until the time of analysis.

Each individual 24 hour urine is diluted with distilled water and adjusted to pH 7.0 with 0.02M imidazole-HCL, ensuring a final conductivity of less than 5 milliMHO. The entire urine so adjusted is then filtered through a glass microfibre filter (Whatman, GF/D) and applied to an anion-exchange resin (Q- Sepharose, Pharmacia, 5.0cm ID by 15cm length, equilibrated in 0.02M imidazole-HCL, pH 7.0) at a rate of 50ml/min. Following application of the urine sample, the column is washed in the reverse direction with 0.02M 4- hydroxypyrimidine/0.03M NaCl, pH 2.0, 4 liters at 50 ml/min, to remove unwanted material. The glycosaminoglycans are then eluted in a stepwise fashion with 2.0M NaCl.

Following desalting (effected by dialysis vs. water with a 1,000 MWCO membrane. Spectra/Por 7, Spectrum Industries) the crude glycosaminoglycan preparation is digested with papain, 0.2 mg/ml, in the presence of 0.05M piperazine, 0.0IM EDTA, and 0.005M L-cysteine at 56 degrees Celsius for 24 hours. This digested material is again dialyzed vs. water with the 1,000 MWCO membrane and subsequently adjusted to pH 7.0 with 0.02M imidazole-HCL, and to a final volume of 4 liters. The papain-digested glycosaminoglycan is then applied to the Q-Sepharose column for a second time in identical fashion to the first. The glycosaminoglycan sample, having been eluted from the anion-exchange column in 2.0M NaCl, is again desalted by dialysis vs. distilled H₂0, using 21,000 MWCO membrane. At this point, the GAG sample typically contains trace levels of urinary pigments. These pigments are removed by passing the sample over a solid phase extraction column (J. T. Baker Inc., Bakerbond spe, phenyl) with 100% recovery of the glycosaminoglycans.

Urinary glycosaminoglycan isolated and purified in this manner consists of a variety of different species: heparan sulfate, dermatan sulfate, chondroitin sulfates, and keratan sulfate. To isolate specific glycosaminoglycan species, the urinary glycosaminoglycan is digested with lyases (degradative enzymes) that cleave only certain types of these molecules. The lyase- digested material is then applied to a gel permeation column (1.5cm by 200cm, TSK-GEL HW-40S) , eluted with 0.5M NH₄HCO₃ and monitored (1) at 232nm and (2) by determination of the uronic acid content of effluent fractions. Undigested glycosaminoglycan appears in the column's void volume while digested material is retarded. Proof of the presence of only a single species of glycosaminoglycan is further given by submitting the material to cellulose acetate electrophoresis using barium acetate, discontinuous voltage, and staining with Alcian blue. An alternative method of preparing pure species of glycosaminoglycan is to apply the lyase- digested material to the anion-exchange column, with washing and elution as described above. The digestion fragments fail to be retained by the exchanger, as proven by applying the material to the gel permeation column and observing only a single void-volume peak. Purified glycosaminoglycan is provided as the ammonium salt in a lyophilized powder. The concentration of the material is expressed in terms of milligrams of uronic acid per milliliter. II. Anti-Cancer Effects of Endogenous Sulfurated GAGs

Utilizing isolated, suramin-induced sulfated glyco¬ aminoglycans, such as those obtained from suramin-treated patients' urine, as shown in Example 1 above, in vitro testing was performed to determine the anti-cancer effects of such GAGs. Examples 2 and 3 relate to such testing. Example 2

A single dose of glycoaminoglycans was isolated from the urine of a patient treated with suramin. The dose of glycoaminoglycans thus isolated in Example 1 was added to the SW-13 adrenal cancer cell line in vitro. Addition of the dose of glycosaminoglycans to the cell line resulted in a 31% reduction in cell number after six days as compared with control (i.e., the cell line grown without exposure to glycosaminoglycan) . Example 3

Isolated urinary GAGs from five patients before and immediately after a course of suramin infusion, utilizing anion-exchange chromatography showed that a four to five- fold increase in GAG excretion occurs with suramin treat¬ ment. Heparan sulfate was isolated from other urinary GAGs, by digestion with chondroitinase ABC followed by gel permeation chromatography.

The urinary heparan sulfate obtained demonstrated cytotoxic activity against two human carcinoma cell lines, SW-13 (adrenal) and LNCaP-FGC (prostate) , with 50% in-hibition of colony formation occurring at uronic acid concentrations of 25 μg/ml and 25-50 μg/ml, respectively. It was further determined, that commercially available bovine kidney heparin sulfate is practically devoid of activity. Further experiments demonstrated the ability of the unique heparan sulfate obtained, as in Example 1 above, to block growth factor (bFGF, EGF, TGF-0) stimulation of thymidine incorporation by these cells grown to confluence. Based upon results contained in Examples 2 and 3 above, it is concluded the endogenous suramin-induced sulfated GAGs exhibit anti-cancer effects, and can be effective in the treatment of cancers in humans. Such endogenous sulfated GAGs would include not only heparan sulfate, but also dermatan sulfate, chondroitin sulfates, and keratan sulfate, among others.

Furthermore, based on test results obtained in Examples 2 and 3, it is envisioned that an effective plasma-concentation of suramin-induced sulfated GAGs for treating cancers, would be about at least 50 mcg/ml, preferably about 50 mcg/ml to 300 mcg/ml. In this regard, it should be noted that the natural occurring levels of total GAGs found in humans is about Ing/ml of plasma. One of the methods of treating cancers disclosed herein provides for treating cancers by administering to a patient an effective amount of the endogenous GAGs of the present invention and an effective amount of suramin. Examples 2 and 3 are not meant to limit this embodiment of the present invention in any manner, since one of ordinary skill in the art would recognize that the conjunctive administration of suramin sodium and the GAGs of the present invention could be utilized to achieve an effective amount of GAGs in a patient for treating cancer. This, of course, is due to suramin*s ability to inhibit lysosomal enzymes responsible for degredation of GAGs in humans.

Pharmaceutical Compositions

The present invention provides for pharmaceutical compositions utilizing the endogenous suramin-induced sulfated GAGs useful in the cancer treatment methods of the present invention. Pharmaceutical compositions useful for administering such sulfated GAGs would include those pharmaceutical compositions which may be administered by injection, since administration by injection of the GAGs herein encompassed, is contemplated. The administration is furthermore contemplated to be preferably by i.v., i.m., or s.c. injection.

Based upon such considerations, the present invention provides for pharmaceutical injectable compositions which contain an effective amount of a suramin-induced sulfated GAG along with a pharmaceutically acceptable carrier therefor, in a suitable injectable dose form. An effective and suitable dosage of such a sulfated GAG is thought to be about l.Omg to about 750mg, dependent upon the dosage schedule employed for administering the sulfated GAGs, the severity and type of cancer treated, as well as physical characteristics of the patient (e.g., weight and plasma volume) .

Exemplary of pharmaceutical compositions encompassed herein would be the following composition containing heparan sulfate. Injectable Composition

Active Ingredient: Endogenous Suramin-induced heparan sulfate ammonium salt -150mg,

Pharmaceutically Acceptable Carrier: 25 ml sterile water for injection USP.

The heparan sulfate salt is dissolved in the sterile water to give a solution, the solution is packaged in ampoules, which are then sealed and sterilized.

The sterile solution may be administered to a patient by injection, preferably by an i.v., i.m. or s.c. route.

When the suramin-induced sulfated GAGs of the present invention are utilized to treat cancers in a patient, it is generally thought that about l.Omg to 1.5g per day of the endogenous suramin-induced sulfated GAGs should be administered to a patient (weight w 75kg) in need thereof. Preferably, however, it is also thought that only about lOmg to l.Og per day of the endogenous suramin-induced sulfurated GAGs should be administered, and most preferably that only 50 to 800 mg per day should be administered to a patient (weight « 75kg) in need thereof. However, in any event, the amount of said GAGs which should be administered to a patient in need thereof, is that amount which produces the desired therapeutic response. Since the present inventive cancer treating methods also provide for jointly administering suramin and endogenous sulfated GAGs in order to treat cancers, it should be noted that the above provided pharmaceutical compositions of the present invention can be administered in conjunction with an effective dosage of suramin, suitable for treating the cancer. However, such conjunctive administration could also be obtained, if desired, with a single injectable dosage form containing effective amounts of both suramin and an endogenous sulfated GAG of the present invention, along with a pharmaceutically acceptable carrier, therefor. Such compositions would preferably contain an effective amount of an endogenous sulfated GAG as defined herein and an effective amount of suramin (e.g., 400mg - 4.0g of suramin sodium) . Such a composition would most preferably be administered so that plasma concentrations of > 300mcg/ml of suramin are not achieved.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

What is claimed is:

1. A method of treating cancer in a human patient, the cancer treated being susceptible to treatment with an en-dogenous suramin-induced sulfated glycosaminoglycan, the method comprising: achieving in said patient an effective plasma level of said glycosaminoglycan for treating the cancer.

2. The method of claim 1, wherein said sulfated glycos-aminoglycan contains 0.1 to 3 sulfate groups per each di-saocharide moiety therein.

3. The method of claim 2, wherein said effective plasma level of the glycosaminoglycan is about at least 50 mcg/ml.

4. The method of claim 3, wherein said sulfated glycosaminoglycan is heparan sulfate; dermatan sulfate; a chondroitin sulfate; or keratan sulfate.

5. The method of claim 3, wherein said glycosaminoglycan is heparan sulfate.

6. The method of claim 1, wherein said effective serum level of said glycosaminoglycan is achieved:

(a) by administering Suramin or a pharmaceutically acceptable salt thereof to the patient, and administering said glycosaminoglycans or a pharmaceutically acceptable salt thereof, in a purified form, by injection, to the patient; or

(b) by administering said glycosaminoglycan or a pharmaceutically acceptable salt thereof, in a purified form to the patient.

7. The method of claim 6, wherein said glycosamino- glycan is in the form of a pharmaceutically acceptable salt.

8. The method of claim 7, wherein said glycosaminoglycan is heparan sulfate ammonium salt, dermatan sulfate ammonium salt, a chondroitin sulfate ammonium salt, or keratan sulfate ammonium salt.

9. The method of claim 7, wherein said glycosaminoglycan is heparan sulfate ammonium salt.

10. The method of claim 6, wherein said effective level of said glycosaminoglycan is achieved: by administering suramin or a pharmaceutically acceptable salt thereof by injection to thepatient; and administering said glycosaminoglycan or a pharmaceutically acceptable salt thereof, in a purified form, by injection to the patient.

11. The method of claim 10, wherein said effective level of said glycosaminoglycan is achieved: by administering suramin sodium by injection to the patient; and administering by injection an endogenous suramin-induced sulfated glycosaminoglycan, selected from the group consisting of: heparan sulfate, a chondroitin sulfate, dermatansulfate, and keratan sulfate.

12. The method of claim 6, wherein said effective level of said glycosaminoglycan is achieved by administering said glycosaminoglycan or a pharmaceutically acceptable salt thereof, in a purified form by injection to the patient.

13. The method of claim 12, wherein said glycosaminogly-can is selected from the group consisting of: heparan sulfate, a chondroitin sulfate, dermatan sulfate and keratan sulfate.

14. A process for isolating a pharmaceutically acceptable salt of an endogenous suramin-induced sulfated glycosaminoglycan (GAG) from a patient's urine, the process comprising:

(a) collecting the urine of a patient having a suramin-plas a level of about at least 50 mcg/ml;

(b) separating the collected urine on a suitable anion-exchange chromatography column, to give a first sulfated GAG containing product;

(c) digesting the first sulfated GAG containing product with a suitable proteolytic degraditive enzyme, to give a second sulfated GAG containing product; (d) separating the second sulfated GAG containing product on a suitable anion-exchange chromatography column to give a third sulfated GAG containing product;

(e) digesting the third sulfated GAG containing product with a suitable polysaccharide lyase enzyme, to give a fourth sulfated GAG containing product; alternatively performing either step (f) or (f") ,

(f) separating the fourth sulfated GAG containing product on a suitable anion-exchange chromatography column, to give the sodium salt of the desired sulfated GAG,

(f") separating the fourth sulfated GAG containing product on a suitable gel permeation chromatography column, to give the ammonium salt of the desired sulfated GAG; and

(g) optionally, converting the obtained salt of the desired sulfated GAG to another pharmaceutically acceptable salt thereof.

15. The process of claim 14, wherein said suramin-induced glycosaminoglycan is heparan sulfate, dermatan sulfate, a chondroitin sulfate, or keratan sulfate.

16. A pharmaceutical composition comprising: an effective amount of an endogenous suramin-induced sulfated glycosaminoglycan or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier therefor.

17. The pharmaceutical composition of claim 16, wherein said suramin-induced sulfated glycosaminoglycan is heparan sulfate, dermatan sulfate, chondroitin sulfate, or keratan sulfate.

18. The pharmaceutical composition of claim 16, wherein said endogenous suramin-induced sulfated glycosaminoglycan is heparan sulfate ammonium or sodium salt.

19. The pharmaceutical composition of claim 16, wherein said composition contains l.Omg to 1.5g of the suramin-in-duced sulfated glycosaminoglycan or a pharmaceutically acceptable salt thereof.

20. The pharmaceutical composition of claim 16, further comprising an effective amount of suramin, or a pharmaceutically acceptable salt thereof.