Refined Detoxified Endotoxin Product

The present invention is directed to a refined detoxified endotoxin (RDE) product which, when combined with cell wall skeleton (CWS), results in a therapeutically effective composition for the treatment of cancerous tumors without the deleterious side effects normally associated with endotoxins. The RDE used in the present composition is characterized as having no detectable 2-keto-3-deoxyoctanoate, between about 350 and 475 nmoles/mg of phosphorus and between about 1700 and 2000 nmoles/mg of fatty acids. The present invention also includes methods of preparing RDE as well as the use of the RDE-CWS composition to obtain regression and remission of cancerous tumors.

Endotoxic extracts obtained from Enterobacteriaciae including parent organisms and mutants are known. These extracts have been used for immunotherapy of various immunogenic tumors [see Peptides as Requirement for Immunotherapy of the Guinea-Pig Line-10 Tumor with Endotoxins; Ribi, et al Cancer Immunol. Immunother., Vol. 7, pgs. 43-58 (1979) incorporated herein by reference]. However, the endotoxin extracts are known to be highly toxic and, therefore, of limited use in the treatment of cancerous tumors. Efforts have been made to "detoxify" the endotoxins while retaining their tumor regressive capacity. As shown, in Ribi, et al, chemical procedures known to "detoxify" endotoxins while retaining adjuvanticity, such as succinylation and phthalylation resulted in both loss of endotoxicity and tumor regressive potency. Therefore, prior art attempts to obtain an endotoxin product with high tumor regressive potency and little or no toxicity have thus far not been successful.

Cell wall skeleton is essentially cell wall which has had much of the protein and lipids normally found in the cell wall removed. It is a polymeric mycolic acid arabinogalactan mucopeptide containing remnants of trehalose mycolate ("P.sub.3 ") and undigested tuberculoproteins. Cell wall skeleton is obtained from any mycobacteria including, but not limited to, M.smegmatis, M.phlei, Nocardia rubra, Nocardia asteroides, Corynebacterium diphtheriae, Corynebacterium parvum, M.kansasii, M.tuberculosis (Strain H 37 RV and Ayoma B), and M.bovis, Strain BCG. Additionally, cell wall skeleton may be obtained from such non-mycobacteria as E.coli, B.abortus and Coxiella burnettii.

Cell wall skeleton is produced by first growing and harvesting a bacteria such as M.bovis, Strain BCG (bacillus Calmette-Guerin). The resulting whole cell residue is processed through a cell fractionator [Ribi Cell Fractionator (Sorvall, Model RF-1)] which disrupts the cells separating the outer envelope or cell wall from the protoplasmic impurities. The resulting cell walls are then subjected to a series of solvent extractions and enzymatic treatments (e.g. trypsin and/or chymotrypsin) to give purified cell wall skeleton.

It is, therefore, an object of the present invention to produce a superior refined detoxified endotoxin product which has a high tumor regressive potency without toxic side effects normally associated therewith. It is another object of the present invention to provide a refined detoxified endotoxin in combination with cell wall skeleton as a highly potent composition for the treatment of cancerous tumors.

The present invention is directed to a refined detoxified endotoxin (RDE) and methods for its preparation. The invention is also directed to the highly potent combination of RDE with cell wall skeleton (CWS) which can effectively be used to treat cancerous tumors. The RDE used in this invention has no detectable 2-keto-3-deoxyoctanoate, between about 350 and 475 nmoles/mg of phosphorus and between about 1700 and 2000 nmoles/mg of fatty acids.

Endotoxin extracts of the type used as a starting material to produce RDE may be obtained from any Enterobacteriaciae including parent organisms and mutants. By way of example, the following genera are illustrative of the type of microorganisms that may be used:

Salmonella, Shigella, Escherichia, Brucella, Bordetella, Citrobacter, Pseudomonas, Pasturella, Neisseria, Proteus, Klebsiella, and Serratia.

The following species are typically employed:

S.minnesota, S.typhimurium, B.pertussis, B.abortus, S.enteritidis, E.coli, S.typhi, S.marcescens, S.typhosa, Shigella flexni, and S.abortus equi.

The endotoxic extracts used as a starting material may be prepared by one of several known methods [see, for example, Webster, M. E., Sagin, J. F., Landy, M., and Johnson, A. G., J. Immunol. 1955, 744, 55; Westphal, O., Luderitz, O., and Bister, F., Z. Naturforsch, 76 148 (1952); Westphal, O., Pyrogens, Polysaccharides in Biology, Tr. Second Macy Conference (George F. Springer, ed.), Madison, N.J. Madison Printing Co., 1957, 115; Galanos, C., Luderitz, O., Westphal, O., Eur. J. Biochem. 9, 245 (1969); Chen, C. H., Johnson, A. G., Kasai, N., Key, B. A., Levin, J., Nowotny, A., J. Infect. Dis. 128 543 (1973); Ribi, E., Haskins, W. T., Landy, M., Milner, K. C., The Journal of Experimental Medicine 114 647 (1961); Leive, L., Biochem. Biophys. Res. Comm. 21 290 (1965); and Ribi, E., Milner, K. C., and Perrine, T., J. Immunol. 82 75 (1959)].

The preferred method of obtaining the endotoxic extract is that disclosed by Chen, et al; namely, methanol-chloroform precipitation.

The methanol-chloroform precipitate (MCP) is then reacted with an organic or inorganic acid and then lyophilized to produce a hydrolyzed crude lipid A with reduced toxicity and pyrogenicity as compared with the starting endotoxin material. The resulting product is then treated with a solvent which is capable of specifically dissolving fatty acids and other impurities without dissolving the crude lipid A. The preferred solvent for this purpose is acetone. The phosphate content of the detoxified, refined lipid A is about one-half that observed for the toxic counterpart suggesting that the phosphate content is related to the toxic effects of endotoxins.

The preferred inorganic acids used to react with MCP are hydrochloric acid, sulfuric acid or phosphoric acid and the preferred organic acids are toluene sulfonic acid or trichloroacetic acid. The reaction may be suitably conducted at a temperature between about 90.degree. and 130.degree. C. for a time sufficient to complete hydrolysis usually between about 15 and 60 minutes.

The preparation of crude detoxified endotoxin may also be accomplished by reacting the starting material with the acid in the presence of an organic solvent such as chloroform, methanol, and ethanol or combinations thereof.

The resulting crude lipid A is dissolved in acetone which is particularly suited to remove the fatty acid components. The solvent is then removed to produce crude detoxified endotoxin.

The crude detoxified endotoxin is then dissolved in a solvent and passed through a suitable chromatographic column such as, for example, a molecular exclusion chromatographic column, to separate the RDE fractions which are then combined after removal of the solvent. In one embodiment, the crude detoxified endotoxin solution is passed through a Sephadex column in the presence of a solvent such as chloroform, methanol, acetone, pyridine, ether or acetic acid or combinations thereof. The pressure of the column may vary but is typically in the range of between about atmospheric and 100 lbs/in.sup.2 and the flow rate is between about 0.1 and 10 ml/min.

In another embodiment, the crude detoxified endotoxin solution is passed through a DEAE-cellulose column under the same pressure conditions as mentioned above for the Sephadex column. The flow rate may be maintained between about 2 and 15 ml/min. The solvents used are also the same as used for the Sephadex column although water and/or diethylamine can be added to all mixtures at a concentration of up to about 1%.

Other methods of producing RDE from crude detoxified endotoxin include passing the solution through a low pressure silica-gel 60 column having a particle size of between about 15 and 63 microns and using a solvent selected from chloroform, methanol, water and ammonium hydroxide. The preferred volume ratio of the aforementioned solvent mixture is about 50:25:4:2.

RDE as produced in accordance with the present invention and CWS are combined to produce a composition having potent anti-tumor activity. The cancers which may be treated by the RDE-CWS composition include animal tumors, such as bovine squamous cell carcinoma, bovine fibrosarcoma, equine sarcoid, equine melanoma, equine squamous cell carcinoma, canine mammary tumors, canine adenoma and canine melanoma.

The composition is preferably administered by injection in a pharmaceutically acceptable medium such as an oil-droplet emulsion directly into the tumor under conditions more particularly described below. The aforesaid composition may be stabilized as, for example, by a lyophilization procedure and then reconstituted without loss in potency.

The amount of RDE in a single injection for treatment of animals is between about 6.25 and 250 micrograms/milliliter. The amount of CWS is between about 125 and 750 micrograms/milliliter. The number of milliliters of the biologic injected into the tumor is determined by the size of the tumor in accordance with the following table:

The maximum dose per injection is about 1500 micrograms for RDE and about 4500 micrograms for CWS. The course of treatment comprises up to 5 injections administered at one week intervals.

The RDE-CWS composition in a suitable injectable medium such as an oil droplet emulsion is administered directly into human tumors. The amount of RDE and CWS, respectively, in a single injection is between about 50 and 1000 micrograms with a preferred single dosage level of between about 275 and 325 micrograms for each component for a typical 70 kilogram adult patient. The injections are administered about once a week for up to a total of 15 injections. Generally, it is desirable to administer the composition containing between about 50 and 500 micrograms/ml of RDE and between about 50 and 500 micrograms/ml of CWS per injection.

As described above the composition for treatment of warm blooded animals may be used in the form of an oil droplet emulsion. The amount of oil used is in the range of between about 0.5 and 3.0 percent by volume based on the total volume of the composition. It is preferred to use between about 0.75 and 1.5 percent by volume of the oil. Examples of such oils include light mineral oil, squalane, 7-n-hexyloctadecane, Conoco superoil and Drakeol 6 VR mineral oil (produced by the Pennreco Company, Bulter, Pa.).

The homogenized oil containing mixture is then combined with a detergent which may optionally be dissolved in a saline solution prior to mixing. The amount of detergent is typically between about 0.02 and 0.20 percent by volume and preferably between about 0.10 and 0.20 percent by volume based on the total volume of the composition. Any common detergent material may be used including Tween-80, and Arlacel (produced by the Atlas Chemical Company).

The mixture resulting from the addition of detergent is then homogenized to form a suspension which has a high percentage of oil droplets coated with RDE and CWS as determined by observation under a microscope.

The following examples are for illustrative purposes only and are not intended to limit or in any way redefine the invention as claimed in the claims appended hereto.

A 650 mg sample of a methanol-chloroform precipitate produced in accordance with the procedure of Chen, et al J. Infect. Dis. 128 543 (1973) was suspended in 150 ml of 0.1 N HCl, in a three necked round bottom flask fitted with a condenser, and immersed in a sonicator. After sonication, the glass apparatus was then lowered into an oil bath maintained at 120.degree. C. which allowed the interior temperature of the flask to approach or exceed the boiling point of the solution. Superheating of the solution was minimized by fitting the flask with a capillary tube attached to a nitrogen gas source through one of the necks. A continuous flow of nitrogen was maintained throughout the hydrolysis procedure.

Hydrolysis was continued for 30 minutes, after which the solution was cooled in an ice bath, sonicated to disperse the solid material and distributed in corex tubes. The flask was washed with distilled water to remove all solid material adhering to the sides of the flask, and the wash was added to the suspension in the corex tubes. Centrifugation was carried out at 12,000 rpm for 80 minutes. The supernatant was decanted and discarded. The solid residue was resuspended in distilled water, sonicated until the suspension was well dispersed and recentrifuged. The centrifugation process was then repeated. The residue was taken up in distilled water, shell frozen and lyophilized yielding 382 mg of crude lipid A. 150 mg of this material were treated with cold (0.degree. C.) acetone to remove fatty acids, sonicated, and filtered through a Whatman No. 1 gravity filtration apparatus at 5.degree. C. 100 mg of crude detoxified endotoxin remained after drying.

A 120 mg sample of MCP (methanol-chloroform precipitate) was suspended in 12 ml of absolute methanol, sonicated to disperse solid materials and distributed into 6 (1.times.10 cm) screw cap vials. 2 ml of 0.2 N HCl were added to each tube and the resulting suspension was incubated in a boiling water bath for 45 minutes. After hydrolysis, the tubes were cooled in an ice water bath and centrifuged for about 10 minutes at 2500 rpm. The supernatant was decanted and 5 ml of a 2:1 chloroform/methanol mixture were added to the residue to effect dissolution. 2 ml of water were added per tube and the solution was mixed. The biphasic solution was recentrifuged at 2500 rpm for 10 minutes. The upper water phase was discarded and 1 ml of a 4:1 chloroform/methanol mixture was added to each tube resulting in a clear solution. The solutions were pooled, and the solvent evaporated on a rotary evaporator. The residue was dried under high vacuum and lyophilized to yield 45 mg of crude lipid A. 20 mg of this material were treated with cold (0.degree. C.) acetone, sonicated, and filtered through a Whatman No. 1 gravity filtration apparatus at 5.degree. C. 13 mg of crude detoxified endotoxin remained after drying.

110 g LH-20-100 (25-100 micron particle size: Pharmacia) were combined with 600 ml of a 2:1 chloroform/methanol mixture which was permitted to stand for 30 minutes. The resulting slurry was added to a 25.times.1000 mm glass chromatography column (BRL Laboratories) fitted with pressure fittings. After packing was complete, the column was attached by means of Teflon pressure tubing to an ISCO Model 132 pump. 400 ml of a 4:1 chloroform/methanol mixture were pumped through the column at the rate of 3 ml/min. 100 mg of crude detoxified endotoxin prepared in accordance with Example 1 were applied to the column in 2.5 ml of a 4:1 chloroform/methanol mixture via a sample loop. The flow was reduced to 1 ml/min. and after 150 ml of eluant were collected, the effluent was connected to a fraction collector. 4 ml fractions were collected and refined detoxified endotoxin fractions were determined by thin layer chromatographic analysis of the fractions [E. Merck, 0.25 mm thick, chloroform/methanol/H.sub.2 O/NH.sub.4 OH (50:25:4:2) as eluant].

The refined detoxified endotoxin fractions were combined and the solvent evaporated leaving 30 mg of refined detoxified endotoxin as a white powder.

33 g of DEAE-cellulose (Whatman DE-32) were suspended in 150 ml of glacial acetic acid and agitated gently for 10 minutes to obtain a slurry powder. The mixture was set aside overnight.

The slurry was poured into a 25.times.400 mm column, allowed to settle with tapping, and excess acid was thereafter drained. The column was washed with 2000 ml of methanol followed by 200 ml of a 4:1 chloroform/methanol mixture. A 100 mg sample of crude detoxified endotoxin produced in accordance with Example 1 was added to the column in 3 ml of a 4:1 chloroform/methanol mixture or an 80:20:1 mixture of chloroform, methanol and water. The column was eluted with 350 ml of a 4:1 chloroform/methanol mixture followed by 300 ml of a 99:1 methanol/water mixture. Using a linear gradient apparatus, the column was eluted with 2000 ml of a linear gradient starting with 100% methanol and ending with 0.2 M acetic acid in methanol. The column was eluted at the rate of 6 ml/min. and 15 ml fractions were collected. Every other fraction was analyzed for total phosphorous content according to the procedure of Bartlett, G. R., J. Biol. Chem. 234, 466-471 (1959). The fractions were pooled and evaporated on a rotary evaporator to near dryness and taken up in 10 ml of a 2:1 chloroform/methanol mixture and 40 ml of 0.001 M acetic acid in a separatory funnel. The lower layer was separated, filtered through Whatman No. 2 filter paper and evaporated to dryness to yield 19.2 mg of refined detoxified endotoxin.

Thirteen Strain 2 guinea pigs having Line-10 tumor growths of about 9 mm. were injected once with 0.4 ml of a sterile oil droplet emulsion, i.e., Drakeol 6 VR mineral oil (Pennsylvania Refining Company, Butler, Pa.), containing 50 micrograms (RDE) and 50 micrograms (CWS) directly into the tumor tissue.

At the end of a three month period, the animals were examined and in 12 of the 13 animals, total regression of the tumor growth had occurred. In a control experiment, 6 Strain 2 guinea pigs having Line-10 tumor growths of about 9 mm. were injected once with 0.4 ml containing 50 micrograms of RDE alone. The injections were made directly into the tumor tissue. None of the 6 tumors showed any signs of regression after three months.