KR20000075562A - Production process for intravenous immune serum globulin and resultant product - Google Patents

Abstract

The present invention provides substantial protection from virus contamination by heat treatment to inactivate viruses, fractionating impure gamma globulin solutions, and then treating solvent-surfactants with purified gamma globulins to inactivate the virus in addition thereto. The present invention relates to a method for preparing an intravenously administrable gamma globulin solution.

Description

Production process for intravenous immune serum globulin and resultant product

Various methods are known for obtaining intravenously injectable γ-globulin solutions from starting materials derived from Cohn fractionation of human plasma. Some cone fractions contain higher titers of γ-globulin than others. Corn fraction II or corn fraction II + III is useful as a starting material for γ-globulin solutions.

While prior art methods include a variety of screening and sterilization techniques, methods are constantly being sought to improve the purity and safety of the final product, and the overall yield.

Many industrial methods include solvent / surfactant steps, or heat treatment steps to inactivate viruses. To date, as part of an effective method for producing high yield γ-globunrin, no multistep method has been provided starting with a corn fraction II paste or a corn fraction II + III paste, comprising two different virus inactivation processes.

U.S. Patent No. 5,151,499 to Kameyama et al. Relates to a method for preparing a protein composition in which a virus is inactivated, wherein the envelope virus is inactivated by treating the protein composition with a solvent / surfactant and the non-envelope virus is The protein composition was inactivated by heat treatment. The patent states that it is preferable to perform the solvent / surfactant step first, followed by heat treatment in the presence of a proteinase inhibitor. To perform the heat treatment in the liquid state, prior to the heat treatment, the protein is first adsorbed to an ion exchange column to recover from the solvent / surfactant. Liquid phase heat treatment can be carried out in the presence of a sugar, a sugar alcohol or an amino acid stabilizer. Although US Pat. No. 5,151,644 lists a number of starting protein compositions comprising immunoglobulins, preparations thereof include Factor 9, thrombin, fibrinogen and fibronectin. The removal of denatured protein produced through fractionation in the heat treatment step is not considered.

Some prior art methods for the preparation of γ-globulin solutions for intravenous injection describe performing a liquid heat treatment step in the presence of a sorbitol heat stabilizer in a multistage purification process starting with a cone fraction II + III paste. In US Patent No. 4,845,199 to Hirao et al., Cone fraction II + III was fractionated into polyethylene glycol (hereinafter 'PEG') prior to liquid phase heat treatment in the presence of sorbitol as a protein stabilizer (8% by weight PEG after 12% by weight PEG). ) And then removal of ion exchange chromatography (DEAE-Sepadex) and human blood group antibodies. On the other hand, Example 1 of U.S. Patent No. 4,876,088 to Hirao et al. Suspended the paste in water, centrifuged by titrating its pH to 5.5, and the supernatant was heat-treated to inactivate the virus under 33 wt% sorbitol, PEG fractionation (6% / 12%) to remove heat denatured protein and another purification step involving DEAE-Sepadex ion exchange chromatography to allow intravenously injectable γ from the cone fraction II + III paste. Preparing a globulin solution is described.

The present invention relates to a holistic, multistage, industrial method for producing immune serum globulins that are intravenously injectable, comprising IgG (γ-globulin) as a main component.

It is an object of the present invention to provide a complete, industrially useful method for producing high purity γ-globulin from the cone fractionation process.

Another object of the present invention is to provide a highly pure intravenously administrable γ-globulin solution free from envelopes and non-envelope viruses comprising all heat sensitive viruses.

It is a further object of the present invention to provide an industrial production method of γ-globulin that precedes the second virus inactivation step and allows the removal of any denatured protein produced during the heat sterilization process.

Another object of the present invention, which will be apparent to the above and skilled artisan, is that the alcohol cone fraction, which is partially purified to inactivate the virus but is rich in γ-globulin, is heat treated in an aqueous medium under a heat stabilizer and then firstly Provided by the present invention is to perform PEG fractionation, to perform a second virus inactivation under a solvent, preferably a solvent-surfactant mixture, in order to destroy the envelope virus, and to separate from the solvent or solvent-surfactant mixture.

In a preferred embodiment of the present invention, sorbitol is a heat stabilizer and trialkyl phosphate is a solvent.

In another preferred embodiment of the invention, the product denatured in the heat treated virus inactivation step is removed by PEG fractionation before the second virus inactivation step to provide significantly pure heat treated γ-globulin.

In another preferred embodiment of the invention, any particles present prior to the solvent-surfactant treatment are removed.

In another preferred embodiment of the invention, heat-sterile and solvent-surfactant sterile γ-globulin is provided for intravenous administration.

Hereinafter, the present invention will be described in detail.

Fractions comprising immunoglobulins are used as starting material. The fraction is not particularly limited as long as it is derived from human plasma and contains an immunoglobulin fraction. Specific examples of such immunoglobulin-containing fractions are pastes of fractions II + III and fraction II obtainable from ethanol fractionation of cones, and the equivalent immunoglobulin-containing fractions. Other starting materials are fractions I + II + III and fractions II + IIIw. Starting materials may include impurities such as antibodies of human blood-groups, plasminogen, IgM, IgA, IgG polymers (hereinafter "aggregates"), and the like.

Preferred starting materials are corn fraction II or corn fraction II + III. In the case of using the Corn Fraction II + III paste, it is recommended to go through an initial washing step to produce the Corn Fraction II + IIIw and then to use it in the process of the invention. "Fragment II + IIIw" is the cone fraction II + III precipitate washed with disodium phosphate solution.

Fraction II + IIIw can be obtained by injecting fraction II + III precipitate in cold water at a ratio of about 1 Kg of II + III paste per 20 volumes of water. Sodium phosphate solution is added so that the final concentration is about 0.003 M for water soluble lipids, lipoproteins and albumin. Cold ethanol is added to bring the final alcohol concentration to about 20%. During the addition of the alcohol the temperature is gradually lowered to −5 ± 1 ° C. and the pH is maintained or titrated to 7.2 ± 0.1 using, for example, acetate buffer or diluted sodium hydroxide. The resulting fraction II + IIIw precipitate is recovered by centrifugation and / or filtration while maintaining the temperature at −5 ± 1 ° C.

Prior to the first virus inactivation step of the present invention, various preliminary purification and / or aggregate-removal steps can be performed. For example, when using a fraction II + IIIw paste that generally contains about 20% alcohol and at least about 70% IgG, 3-10 volumes, preferably 3-5 volumes, of cold water at about 0-5 ° C. It can be suspended and titrated to a pH between 4.5-6.0, preferably 5.0-5.5 using acetate buffer pH 4.0 or hydrochloric acid. The mixture is shaken for about 2-15 hours to allow all γ-globulins to mix into the solution. Then, undissolved proteins such as albumin and α-globulin can be removed by centrifugation and / or filtration.

When using other starting cone fractions, where it is desired to perform preliminary purification to obtain fractions containing large amounts of IgG, the initiation step (s) to proceed to the next step may be appropriately selected. For example, where corn fraction II (containing 95% or more IgG) is separated from corn fraction III, the aggregates are known to have anti-complementary activity when proceeding to the next stage with corn fraction II. As described by Uemura et al. In Patent No. 4,371,520, in order to cleave the immunoglobulin aggregates into immunoglobulin monomers and dimers, the initiation process can be performed at an acidic pH of 3.2-5.0, preferably 3.8-4.2. have. Alternatively, when the cone fraction II + III is used as a starting material, the low pH treatment described in the patent of Uemura et al. Is carried out as an additional step before the initial purification step described above and the virus inactivation heat treatment step. can do.

For the heat sterilization step, sugars, sugar alcohols and / or are themselves in the form of water-soluble mixtures, such as by dissolving the immunoglobulin protein in water, or the filtrate collected from the partial purification of fractions II + III described above. Add amino acid heat stabilizer. The heat stabilizer is preferably sucrose, maltose, sorbitol or mannitol, more preferably sorbitol. Sugar or sugar alcohol is added to the immunoglobulin solution as a powder or mixed in a small amount of water to provide a final concentration ranging from about 10-50% by weight to saturation. At this time, the aqueous solution of immunoglobulin contains sufficient water and as a result the solution contains a typical cone fraction II + III starting material containing about 1-6% of total protein, about 300 g of protein per Kg of paste.

After addition of the heat stabilizer, the mixture is heated to about 50-70 ° C. for about 10-100 hours, preferably at about 60 ° C. for about 10-20 hours to inactivate the heat sensitive virus. The heat treatment step not only inactivates the virus, but also through some of the effects of denaturing the protein of the virus, preferably for several purposes generally combined with cone fractions II + III such as prekallikrein, plasmin, plasminogen and IgA It can reduce the amount of protein that is not.

After heat treatment, cold water is added in the required amount to maintain the protein concentration at about 0.3-2.0%. Cool this solution to 0-2 ° C.

Next, PEG fractionation is performed with the heat treated solution. PEG fractionation is a well known method performed in the art of purifying immunoglobulins to separate desired IgG monomers and dimers from IgG aggregates and other impurities naturally present in the starting plasma protein fraction. In this method, PEG fractionation is performed to isolate desired IgG monomers and dimers and unwanted denatured protein products produced by heat treatment. Such denatured protein products are denatured prekallikrein, plasminogen, plasmin, IgA, IgM and aggregates.

Any PEG fractionation method disclosed in the prior art can be used. Generally, two stages of PEG fractionation are performed. The first step in PEG fractionation is to properly select the PEG concentration and pH so that the desired IgG monomer and dimer remain in solution while unwanted proteins, such as aggregates, are precipitated in solution. After centrifugation and / or filtration, the PEG concentration is increased with pH to allow precipitation of the desired IgG monomer and dimer.

For example, if the first step of PEG fractionation is within a pH range of about 5.0-7.5, and fraction II + IIIw paste is used as starting material, preferably within 6.5-7.5 pH, fraction II + III is used as starting material. If used, preferably at a concentration of PEG in the range of about 4-8%, at a pH of 5.5-6.0, and at a concentration within 4-6%, preferably when using fraction II + IIIw paste as starting material, fraction II + When using III as the starting material, it can be preferably carried out at a concentration within 6-8%. While maintaining a cold temperature of about 0-2 ° C., the first step of PEG fractionation can be performed for about 1-8 hours, after which the precipitate is removed as described above. The filtrate is then titrated to pH 8.0-9.0, preferably 8.5-8.9, so that additional PEG is added to a final concentration of about 10-15%, preferably about 12%. Once the precipitate which purified immunoglobulin is formed, it is separated by filtration and / or centrifugation.

Detailed PEG fractionation procedures that can be used to carry out the present invention can be found in US Pat. No. 4,876,088 to Hirano et al. And US Pat. No. 4,845,199 to Hirano et al. Described above.

The final and essential step of the present invention is to carry out a second virus inactivation process using a solvent or solvent-surfactant mixture. As described below, subsequent purification processes, particularly those involving the use of ion exchange resins, can be performed before and / or after solvent-surfactant treatment. A particularly preferred method is to carry out the anion exchange treatment prior to the solvent surfactant virus inactivation followed by the cation exchange treatment after the solvent surfactant virus inactivation. By this method, some unwanted protein substances (prekallikrein activator, IgA, IgM and albumin) found in human plasma can be removed from the IgG using an anion exchanger, followed by a cation exchange process. It is possible to further remove such substances (prikallique activator, IgA, IgM, albumin and PEG) together with the remaining reagents used in solvent-surfactant treatment.

Unless otherwise achieved during the whole process, the solution to which the solvent-surfactant is to be treated must be freed of all particles containing the denatured protein. Therefore, prior to the addition of the solvent-surfactant, it is desirable to filter the solution with a 1 micron or thinner filter. This will also reduce the likelihood of the virus being in large particles and avoiding exposure to solvent-surfactants.

Preferred solvent for inactivation of the envelope virus is trialkyl phosphate. There is no particular limitation on the trialkyl phosphate used in the present invention, but it is preferable to use tri (n-butyl) phosphate (hereinafter "TNBP"). Other usable trialkyl phosphates are tri (ter-butyl) phosphate, tri (n-hexyl) phosphate, tri (2-ethylhexyl) phosphate and the like. It is also possible to use mixtures of two or more of different trialkyl phosphates.

Trialkyl phosphate is used in amounts of 0.01-10 (weight)%, preferably 0.1-3 (weight)%.

Trialkyl phosphates may be used in the presence or absence of surfactants or additives. Preference is given to using trialkyl phosphates with surfactants. The surfactant acts to increase the contact of the trialkyl phosphate with the virus in the immunoglobulin composition.

Examples of surfactants include partial esters of anhydrous sorbitol of polyoxyethylene derivatives of fatty acids, polysorbate 80 (trade name: Tween 89, etc.) and polysorbate 20 (trade name: Tween 20, etc.); And nonionic oil bath rinses such as oxyethylated alkylphenols (trade name: Triton X 100, etc.). Still other examples include surfactants such as suspectants and Zwitter ion surfactants and the like.

When using a surfactant, it is not added in critical amount; For example, it may be used at a ratio between about 0.001% and about 10%, preferably between about 0.01% and 3%.

In the present invention, the trialkyl phosphate treatment of the immunoglobulin containing composition is carried out at about 20-35 ° C., preferably 25-30 ° C., for at least 1 hour, preferably about 5-8 hours, more preferably about 6- Run for 7 hours.

During trialkyl phosphate treatment, immunoglobulins are present in about 3-8% protein solution in aqueous medium.

If not performed prior to the solvent-surfactant treatment, anion exchange treatment may be performed on the immunoglobulins treated with the solvent surfactant. Preferably, at least cation exchange treatment is carried out on the product treated with the solvent-surfactant. Ion exchange treatment is performed by dissolving immunoglobulins in an aqueous solvent, typically having a pH of about 5-8, at the low ionic strength required for maximum adsorption of IgG. Generally, the protein concentration is in the range of about 1-15% by weight, preferably about 3-10% by weight. The ion exchangers were equilibrated with the same water soluble solvents used and subjected to a batch or continuous system. For example, an anion exchange batch treatment may comprise an immunoglobulin solution at about 10-ml per anion exchanger (e.g., 1 g DEAE Sephadex A-50 resin is called about 20 g dry weight in 0.4% sodium chloride solution) prior to treatment. By mixing with anion exchanger in an amount of 100 ml, stirring the mixture at about 0-5 ° C. for 0.5-5 hours, and then recovering the supernatant by filtration or centrifugation for 10-30 minutes at 6000-8000 rpm. have. Continuous treatment can be performed by passing the immunoglobulin solution through a column of anion exchangers at a rate of about 10-100 ml per ml of ion exchanger and recovering the non-adsorbed fraction.

Anion exchangers used include, for example, anion exchange groups that bind to water-insoluble carriers. Anion exchange groups include diethylamineethyl (DEAE), tetravalent aminoethyl (QAE) groups, and the like, and water-insoluble carriers include agarose, cellulose, dextrin, polyacrylamide, and the like.

Cation exchangers that can be used are carboxy methyl sephadex CM-cellulose, SP-sephadex, CM-sepharose and S-sepharose. 1 ml of pre-treatment cation exchanger (eg, 1 g CM- Sephadex C-50 resin is called dry weight of about 30-35 g in 0.4% sodium chloride solution) with 0.5-5 ml of immunoglobulin solution, and Stir at 0-5 ° C. for 1-6 hours. The suspension is filtered or centrifuged to recover the IgG adsorbent resin. It is also possible to carry out a continuous method.

In the case of using a cation exchanger under the conditions described above, IgG will be adsorbed, and then washing the protein-adsorbed anion exchange resin, for example, eluting the IgG with a solution of about 1.4 N sodium chloride.

The next step in the process is to purify the IgG, ultrafilter and concentrate to the required amount. If desired, stabilizers such as D-sorbitol can be added, and the final titration gives a solution of the composition containing about 100 mg / ml IgG and about 50 mg / ml D-sorbitol to pH 5.4. This solution is then sterile filtered through a sterile bacterial adsorption filter and filled into vials.

The following examples are only intended to illustrate the invention, but are not limited thereto.

Where desired, other immunoglobulin purification procedures can be combined as appropriate with the methods described herein. For example, a bentonite purification step may be performed that is useful for lowering the level of kallikrein or pre-kallikrane activator. An example of this invention is shown in Example 1 below.

Example 1 Heat Treatment and Solvent-Surfactant Treatment γ-globulin

685 g of Fraction II + IIIw paste was suspended in about 11.9 g of cold water. To selectively solubilize IgG, sodium acetate trihydrate solution was added to the suspension to a final concentration of about 0.04M. After mixing for about 15 minutes, the pH of the suspension was titrated to 4.8 with acetate buffer pH 4.0. During the addition of the alcohol, the temperature of the suspension was gradually lowered to about -6 ° C. 303 g of Celite 535 washed with acid purchased from Celite cor. Was added to the suspension as a filter aid to a final concentration of about 2.0%. After mixing for 1 hour, the fraction III paste containing celite and unwanted proteins such as plasmin, plisminogen, IgA, IgM was removed by filtration using filtration pressure. The filtrate was further purified by 0.45 μm and 0.2 μm filters.

The pH of the fraction II + IIIw clarification solution was adjusted to 4.0 with 1.0 N hydrochloric acid and then concentrated by ultrafiltration to about 3.4 L (1/5 of the initial volume). The amount and the same amount of cold water removed in the first ultrafiltration were added to the concentrated solution and concentrated by ultrafiltration to about one fifth of the initial volume. At this stage, the protein concentration of the solution was about 2%. The solution was further concentrated to about 4% and ultrafiltered in cold water until the conductivity of the solution was below 300 μS / cm, helping to prevent protein aggregation or denaturation during heat treatment. The solution was further concentrated to 8.8% protein. D-sorbitol was added to the solution to a final concentration of about 33%. After mixing for 30 minutes, the pH of the sorbitan containing the solution was titrated to 5.5 with 0.5 N sodium hydroxide. The solution was then heated at 60 ° C. for 10 minutes. After heat treatment, cold water three times the volume of the heat treated solution was added and the diluted solution was cooled to 0-2 ° C.

The pH of the solution was titrated to 6.9 with 0.25N sodium hydroxide and 50% PEG 3350 was added to the solution to bring the final PEG concentration to 4%. To help precipitate impurities and aggregate at pH 6.9, the sodium chloride concentration of the solution was adjusted to about 8 mM. The pH of the filtrate was adjusted to 4.8 with 1.0 N hydrochloric acid and bentonite was added to a final concentration of about 0.25%. The pH of the bentonite suspension was titrated back to about 5.2 and the suspension was filtered to remove bentonite. The filtrate pH was titrated to 8.5 with 0.25N sodium hydroxide and 50% PEG 3350 solution was added to a final PEG concentration of 12%. The precipitate thus formed (purified immunoglobulin) was recovered by centrifugation.

About 175 g of purified immunoglobulin paste obtained above was suspended in about 790 g of 0.3% sodium chloride solution. The pH of the suspension was titrated to 5.5, then the suspension was mixed for 2 hours 30 minutes. 62 g of DEAE Sephadex A-50 resin, previously equilibrated (with 0.3% sodium chloride at pH 5.5), was added to the solution and the suspension was mixed for 2 hours. The suspension was then filtered to remove the resin. The concentration of sodium chloride was adjusted to 0.4% and then a mixture of tri-n-butyl phosphate (TNBP) and polysorbate 80 was added to the filtrate to make a solution with a final concentration of 0.3% TNBP and 1.0% polysorbate 80. After incubation overnight, the pH of the solution was titrated to 5.8 and about 860 g of CM-Sepadex C-50, which had been previously equilibrated (with 0.4% sodium chloride at pH 5.8), was added. After mixing for 2 hours, the solution was filtered. The CM- Sephadex resin was washed three times with 0.3% sodium chloride, and then the adsorbed IgG was eluted with 1.4N sodium chloride. The eluate was clarified, ultrafiltered and concentrated. Final titration at pH 5.4 with the addition of D-sorbitol resulted in a composition solution containing about 100 mg / ml IgG and about 50 mg / ml D-sorbitol. This solution was then sterile filtered through a sterile bacterial adsorption filter and filled into vials.

The intermediate bentonide step in this example is useful for further reducing the presence of low blood-enzyme enzymes such as kallikrein and pre-kallikrein activator.

Test results of the product of Example 1 Test parameters Anti-complement activity (CH ₅₀ u / mg IgG) 0.34 IgG purity (%) 100 IgG concentration (mg / ml) 112.7 Precali Crane (% CBER Ref. No. 3) 21 Measles Antibody (% CBER Reference Classification Number 176) 0.67 IgG molecular size distribution (%) monomer (%) dimer (%) fragments (%) aggregates by HPLC 82.217.40.100.3 Hepatitis A Antibody (Titer) 1: 200 Hepatitis B Antibody (Titer) 1: 1204 IgA (μg / ml) 22 IgM (μg / ml) 16 Plasminogen (ng / ml) Not detected Plasmin (ng / ml) 16 pH 5.4

Example 2: Heat Treatment and Solvent-Surfactant Treatment γ-globulin

1 Kg of Fraction II + III paste was suspended in about 4.5 Kg of 0-2 ° C. cold water. After mixing for 1 hour, the pH of the suspension was titrated to 5.0 with 1N hydrochloric acid. After mixing for 3 hours at pH5.0, the precipitate was removed by centrifugation. D-sorbitol was added to the centrifuge to a final concentration of 33% and mixed for 1 hour. The pH of the suspension was then adjusted to 5.5 and heated at 60 ° C. for 10 hours. After heat treatment, cold water three times the volume of the heat treated solution was added and the diluted solution was cooled to 0-2 ° C. 50% PEG 3350 solution was added to a final concentration of 6%. The pH of the 6% PEG suspension was titrated to 5.7 with 0.5 N sodium hydroxide and the suspension was mixed for 2 hours. Acid washed Celite 535 was added to a final concentration of 1.5% and the suspension was mixed for 1 hour. The precipitate along the celite was filtered off. The pH of the filtrate was adjusted to 8.8 with 0.5 N sodium hydroxide and the PEG concentration was adjusted to 12% by addition of 50% PEG. The pH of the 12% PEG suspension was titrated back to 8.8 and the suspension was mixed for 1 hour and filtered to recover the purified immunoglobulin paste. About 251 g of purified immunoglobulin paste was recovered.

251 g of purified immunoglobulin paste obtained in the above procedure was suspended in about 1.4 Kg of 0.3% sodium chloride solution. After mixing for 1 hour, the pH of the suspension was adjusted to 6.0 with 5% acetic acid. After the paste was completely dissolved, 104 g of DEAE-Sepadex A-50 resin, equilibrated with 0.3% sodium chloride at pH 6.0, was added to the solution and mixed for 2 hours. The resin was filtered off. The filtrate was further purified through a 0.2 μm filter. The concentration of sodium chloride in the clarified solution was increased to 0.4% by addition of sodium chloride. A mixture of tri-n-butyl phosphate (TNBP) and polysorbate 80 was added to the solution to a final concentration of 0.3% TNBP and 1.0% polysorbate 80. The solution was then incubated at 27 ° C. for 1 hour and placed in a refrigerator at 4 ° C. overnight. The next day the pH of the solution was titrated to 5.8 and 1.8 Kg of CM- Sephadex C-50 resin, previously equilibrated with 0.4% sodium chloride at pH 5.8, was added. After mixing for 2 hours, the resin was filtered off. The CM- Sephadex resin was washed three times with 0.3% sodium chloride, and then the adsorbed IgG was eluted with 1.4N sodium chloride. The eluate was clarified, ultrafiltered and concentrated. D-sorbitol was added and final titrated to obtain a composition solution containing about 100 mg / ml IgG and about 50 mg / ml D-sorbitol. The solution was divided into 2 parts, A part and B part. The pH of part A was titrated to 5.4 and the pH of part B to 4.3. The Part A and Part B solutions were then sterile filtered through individually sterilized bacterial adsorption filters and filled into vials.

Test results of the product of Example 2 Test parameters Anti-complement activity (CH ₅₀ u / mg IgG) <0.05 IgG purity (%) 100 IgG concentration (mg / ml) 104.2 Precali Crane (% CBER Ref. No. 3) Not detected Diphtheria Antibody (Antitoxin U / ml) 8.2 IgG molecular size distribution (%) monomer (%) dimer (%) fragments (%) aggregates by HPLC pH 5.488.810.90.3 <0.3 pH 4.397.52.3 Not detected <0.3 Hepatitis A Antibody (Titer) 1: 100 IgA (μg / ml) 78 IgM (μg / ml) 28 Kallikrein (A ₄₀₅ ) 0.09 Plasminogen (ng / ml) <8.4 Plasmin (ng / ml) <8.4

Modifications of the invention will be apparent to those skilled in the art.

Claims (16)

(a) heat treating the impure gamma globulin solution under time and temperature conditions sufficient to inactivate the heat sensitive virus; (b) fractionating the heat treated gamma globulin solution with polystyrene glycol to obtain a purified gamma globulin solution; (c) treating the purified gamma globulin solution with an organic solvent to inactivate the envelope virus, thereby preparing an intravenously administrable gamma globulin solution. The method according to claim 1, wherein the impure gamma globulin solution is corn fraction I + II + III, corn fraction II + III, corn fraction II + IIIw or corn fraction II. The method of claim 1 wherein the impure gamma globulin solution is subjected to at least one purification step prior to the heat treatment step of (a). The process according to claim 1, wherein the heat treatment step (a) is carried out at about 50-70 ° C. for about 10-100 hours. 5. A process according to claim 4 wherein the heat treatment step of (a) is carried out at about 60 [deg.] C. for about 10 hours. The method according to claim 1, wherein the polyethylene glycol fractionation removes impurities in the form of a precipitate in the first step and recovers gamma globulin in the form of a precipitate in the second step. The method according to claim 1, wherein the organic solvent used in step (c) is alkyl phosphate. The method according to claim 6, wherein the organic solvent used in step (c) is alkyl phosphate. 9. A process according to claim 8 wherein the alkyl phosphate is tri-n-butyl phosphate. The method of claim 1 wherein the organic solvent comprises a surfactant. 10. The process of claim 9 wherein the organic solvent comprises a surfactant. The method according to claim 1, wherein after the step (a), the gamma globulin solution is treated with an anion exchange resin and a cation exchange resin. 13. The process according to claim 12, wherein the anion exchange resin treatment is before step (c) and the cation exchange resin treatment is after step (c). 7. A process according to claim 6, wherein the bentonite purification step is carried out after the first step of the polyethylene glycol fractionation. An intravenously administrable gamma globulin solution prepared by the method of claim 1. Intravenous administrable gamma globulin solution prepared by the method of claim 13.