Abstract:
A process for the manufacture of vancomycin.HCl which does not require preparation of a phosphate intermediate. The process consists of loading a vancomycin onto a suitable adsorbent and eluting the vancomycin solution therefrom with an ammonium solvent followed by loading the vancomycin solution onto a suitable adsorbent and eluting the purified, vancomycin solution therefrom with a solvent of alcohol and acid. The purified vancomycin is then crystallized from the solution by combining the solution with a sufficient amount of NH 4  Cl to provide a pH of about 2.0 to about 3.5. The crystals are then dissolved in solution. The dissolved solution is combined with acid and the vancomycin recrystallizes from the solution.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 07/550,427, filed Jul. 10, 1990, now abandoned. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a process for the manufacture of vancomycin.HCl. 
     BACKGROUND OF THE INVENTION 
     Vancomycin is used to treat serious infections of methicillin-resistant staphylococci. Vancomycin is produced by cultivating the bacteria S. orientalis in a nutrient culture media. 
     The vancomycin broth is filtered and added to a column that contains an adsorption resin that decolorizes and desalts the vancomycin. The resin is washed, and the vancomycin eluted with a solvent of low pH, followed by decolorization with carbon. 
     The vancomycin eluant is then further purified using a single recrystallization step at low pH. The crystallized vancomycin is combined with a strong acid such as hydrochloric acid (HCl) and precipitated in an organic solvent such as acetone to form vancomycin HCl. This process for the manufacture and purification of vancomycin.HCl is disclosed in U.S. Pat. No. 3,067,099 to McCormick et al. 
     In another example of a prior art process for the manufacture of vancomycin.HCl, a solvent of 0.1% phosphoric acid (H 3  PO 4 ) in a solution of 10% isopropyl alcohol (IPA) is used to elute purified vancomycin from the adsorption column. The vancomycin eluant is then concentrated using reverse osmosis or vacuum evaporation. An aqueous solution that is approximately 60 g/l of potassium phosphate (KH 2  PO 4 ) is added to the concentrated vancomycin solution. The KH 2  PO 4  causes the vancomycin to crystallize from the solution. The resulting slurry is centrifuged to remove the excess liquid. The vancomycin crystals obtained from centrifugation of the slurry are reslurried in sodium hydroxide (NaOH) to a pH of approximately 4.5 followed by treatment with KH 2  PO 4  to a pH of approximately 2.0. Vancomycin again crystallizes from the solution. The resulting slurry is centrifuged to separate the crystals from the liquid. The resultant solid is dissolved in water and the mixture is eluted in an ion exchange column to prepare vancomycin hydrochloride. 
     European Patent Application, Publication No. 0323150 to Catt et al. discloses an alternate method to precipitate vancomycin in a base solution with a pH of 7.8 to 9.0. At pH&#39;s above about 9.0, the base crystallization disclosed in Catt et al. is unsatisfactory because reduced yields and discolored products result; pH&#39;s of 8.0 to 8.5 are preferred for the crystallization disclosed by this reference. 
     SUMMARY OF THE INVENTION 
     The invention herein is a process for the manufacture of vancomycin.HCl using ammonium chloride (NH 4  Cl) crystallization at a pH of about 2.0 to about 3.5. Vancomycin is concentrated and purified by elution with a base solvent through a column with a suitable adsorbent therein followed by elution through a second column with another suitable adsorbent therein which decolorizes and desalts the vancomycin. The solvent used in the second column is an acid/alcohol solution, the alcohol being an approximately 10% solution of ethanol or isopropyl alcohol. Ammonium chloride is added to the vancomycin eluant in an amount sufficient to impart to the resulting solution a pH of approximately 2.0 to 3.5. The vancomycin crystallizes and precipitates from the solution. The crystals are then separated from the solution. 
     The crystals are redissolved at a pH above 9.0 and a sufficient amount of ammonium chloride or hydrochloric acid is added to the dissolved solution to impart a pH of about 2.0 to about 3.5 to the solution. Recrystallized vancomycin results. The resulting crystals are then separated from the solution and dried. 
     The present process has distinct advantages over the prior art. First, the vancomycin purity from this process (90±1%) is at least 2-3% higher than those obtained by other processes. The purity is increased without additional chromatographic, extraction, or complex formation steps for further purification. Secondly, some time-consuming and expensive conversion steps using ion-exchange resins to obtain the desired hydrochloride salt are totally eliminated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a flow diagram of an embodiment of the process disclosed herein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Vancomycin typically is prepared in a fermentor. Vancomycin is then separated for activity and purified. Typically, the desired vancomycin is separated from other strains of vancomycin and other impurities by elution of &#34;raw&#34; vancomycin through a column with an adsorbent therein. The preferred active strain of vancomycin is vancomycin B. For purposes of this disclosure, adsorbents that are selective for vancomycin B such as DOWEX 50 WX2, a cation-exchange resin available from Dow Chemical, and AMBERLITE XAD-16, a non-functional resin available from Rohm &amp; Haas, were utilized to separate other strains of vancomycin and impurities from the vancomycin B. 
     Elutions are performed in fractions. Each fraction is analyzed to determine the concentration and quantity of vancomycin B therein. In this way the fractions with the greatest concentration of the desired strain of vancomycin can be combined to optimize the yield from the process. The fractions, for convenience, are expressed in the number of bed or column volumes they represent. The purity of the vancomycin varies from fraction to fraction and depends on a number of factors such as the solvent used to elute the vancomycin from the column and the fermentation medium. 
     Referring now to the scheme shown in FIG. 1, vancomycin enriched Dowex 50 resin is obtained and rinsed with water in a screened sanitary tank 10. The resin is loaded onto a six-inch column 12 and eluted with one bed volume of 0.5N NH 4  OH and five to seven bed volumes of 0.25N NH 4  OH. The resin is eluted and the fractions are collected, analyzed for the presence of the desired strain of vancomycin and combined in sanitary tank 14. The pH of the fractions is adjusted by adding hydrochloric acid to tank 14 in an amount sufficient to lower the pH to 3.5. The fractions are pooled by using thin layer chromatography to determine which fractions have acceptable amounts of the desired vancomycin B strain therein. 
     The pH of the combined eluates is increased to about 7 to about 7.5 by adding a sufficient amount of NH 4  OH. The solution is mixed with filter aid and then filtered through a 0.1μ PALL depth filter 18 to remove hazy precipitates. The filtered solution is then loaded onto a six-inch XAD-16 resin column 20 at a loading capacity of approximately 30 g/l. The column 20 is washed with water. The enriched XAD-16 resin is then eluted with six to seven bed volumes of a solution of 0.1% HCl in an aqueous solution that is 10% isopropyl alcohol. Fractions are collected and pooled in sanitary vessel 22 based on the activity detected by thin layer chromatography. 
     The mixture is then concentrated in a thin film evaporator 24 to remove the alcohol. The solution is concentrated to 250 grams of vancomycin per liter of solution. The concentrated solution is placed in sanitary tank 25. 
     The concentrated vancomycin solution is combined with 30 to 60 g/l of ammonium chloride (NH 4  Cl), and a solution pH of about 2.0 to 3.5 results. A thick gel forms immediately when a vancomycin concentration of about 200 to about 250 g/l is used, while a very heavy slurry forms when about a 100 to about 150 g/l concentration of vancomycin is used. Also, when a higher solution pH is maintained the gel appears thicker. The mixture is stirred continuously using mixer 26 to keep the gel dispersed in solution. 
     Crystals form over a 24-48 hour period. The slurry is vacuum filtered in filter 28. The solids are placed in sanitary tank 30. The crystals are reslurried by adding water to the tank 30. 
     The vancomycin is recrystallized by first dissolving vancomycin crystals in urea that is added to tank 30. A high concentration of urea (2-6M) is used to dissolve the vancomycin crystals and to release color bodies which are physically entrapped in the vancomycin molecules. After the crystals are dissolved in tank 30, the solution is diafiltered using reverse osmosis (MILLIPORE NF40) with 400 molecular weight cut off (MWCO) or ultrafiltration (1000 MWCO) membranes in module 32. The module 32 diafilters urea and residual salts from the dissolved solution. The filtrate is a clear concentrate which is placed in sanitary vessel 36. NH 4  Cl is then added to the concentrated, filtered solution in sanitary tank 36. 
     In an alternate method for recrystallizing vancomycin using this process, ammonium hydroxide (NH 4  OH) is used to dissolve the crystals obtained from the first crystallization step. The NH 4  OH is added to the solution in tank 30 in an amount sufficient to raise the pH to above about 10.0±0.5. The vancomycin activity is stable (less than 2% degradation) at a pH of 10.5 for about 2 hours at room temperature. The solution pH is then reduced to about 2.0 to 3.5 by adding a sufficient amount of hydrochloric acid (HCl). After adding the HCl, the solution becomes immediately cloudy. If the pH is reduced below 9.0, a gel forms when the pH reaches 7.5 which follows as more HCl is added. As still more HCl is added, the gel softens to a slurry. Crystals precipitate from the solution overnight at pH 2.0-3.5. 
     EXAMPLE I 
     Crystals made according to the previously described process were washed or reslurried by adding a solution that was 0 to 60 g/l NH 4  Cl in water. The higher NH 4  Cl concentrations reduced vancomycin loss in the mother liquor but did not remove color as effectively. The solids were then dried under vacuum under 50° C. (90° F.) and the dried solid was milled for analysis. 
     Five batches of vancomycin were made according to the above-described process. The products were analyzed for purity, yield, pH and a variety of other properties to determine their acceptability. Table I is a summary of these test results. 
     
                                           TABLE I__________________________________________________________________________Product Quality.sup.1 and Yield from NH.sub.4 Cl Crystallization at pH3.0 ± 0.5Sample      1     2    3     4    5__________________________________________________________________________Purity (HPLC.sup.2)       90.0% 86.3 89.4  91.4 90.8Major Impurity       2.4%  3.1  2.9   2.2  2.3APHA.sup.3 Color       300   300  300   300  300pH (2.8-4.2)       3.6   3.6  3.3   3.2  3.5% Moisture  1.9%  2.8  0.8   2.8  4.3% ROI (ash).sup.5       0.0%  0.0  0.0   --   --Heavy metal (Pb)       &lt;0.002%             &lt;30 ppm                  &lt;30 ppm                        &lt;30 ppm                             &lt;30 ppmBiopotency (μg/mg)       996   1046 1072  973  1006Step yield:Dowex resin - &gt;concn.       95%   ˜99%                  97%   98%  96%Crystallization       90%   90%  92%   72%  89%Recrystallization       95%   90%  83%   96%  82%Overall Yield.sup.4by activity 73%   70%  67%   61%  63%by weight   81%   81%  75%   67%  69%__________________________________________________________________________ .sup.1 All products are in powder form and meet infrared identification requirements. .sup.2 High Pressure Liquid Chromatography .sup.3 APHA: American Public Health Association .sup.4 Assume 90% beer adsorption .sup.5 Residue of ignition 
    
     The high pressure liquid chromatography (HPLC) purities of the final products were between 86 and 92% and the APHA color readings were 300 which is acceptable. Residual phosphate and acetate levels were essentially nondetectable and the ashes (ROI) were less than 0.1% where tested. Anhydrous biopotencies were all approximately 1000 micro grams per milligram which is acceptable. 
     The examples herein illustrate yields of from 65% to 81% by weight assuming a 90% yield in the step from the harvest from production to the eluate from the DOWEX 50 resin (the first elution). 
     EXAMPLE II 
     Effect of pH During NH 4  Cl Crystallization on Product Purity and Color 
     A suitable process for the production of vancomycinHCl must adequately remove color impurities from the final product. Although color removal accomplished by eluting vancomycin with a solvent in AMBERLITE XAD-16, a macroreticular resin, residual color that remains in the vancomycin must be removed during the crystallization and recrystallization steps. Table II illustrates the effect of pH on color removal during crystallization. The table illustrates that improved color removal is achieved at a pH of 2.06 as opposed to 2.97, but at the expense of yield. 
     
                       TABLE II______________________________________Effect of Varying pH During NH.sub.4 ClCrystallization on Product Purity and ColorSample.sup.1       6          7______________________________________Initial Conc.      87.6 g/l   87.6 g/lpH                 2.06       2.97Product:APHA color         100        450pH                 2.29       3.30HPLC purity        92.48%     90.91%Largest Single     1.31%      2.19%Impurity (LSI)% Moisture         0.91%      3.54%% Acetone          1.7%       0.0%Crystallization Step Yield:by activity        66%        75%by weight          71%        83%Mass Balance       99%        98%______________________________________ .sup.1 Both samples meet the infrared identification standard. 
    
     EXAMPLE III 
     Effect of pH and Concentration on Product Quality and Yield 
     Table III illustrates that there is no appreciable difference in color removal if the NH 4  Cl crystallization occurs at a pH of 2.0 or 2.5, but that the initial concentration of vancomycin significantly effects the color of the product obtained from crystallizations at these pH&#39;s. Acceptable color removal is obtained when the initial vancomycin concentration is 112 g/l, regardless of whether the pH of the solution was 2.0 or 2.5. Unacceptable color removal is obtained at higher concentrations whether the pH was 2.0 or 2.5 although yield was somewhat improved at the higher concentrations. 
     
                       TABLE III______________________________________Effect of Varying pH and InitialConcentration on Vancomycin.HCl Quality and YieldSample       8        9        10     11______________________________________Initial conc.        112      112      225    225(g/l solid)pH           2.0      2.5      2.0    2.5NH.sub.4 Cl (g/l)        120      120      30     30Product:HPLC purity  91.74%   91.67%   91.54% 91.28%LSI          2.04%    2.04%    2.01%  2.07%APHA color   300      300      400    350Crystallization        64.5%    76.9%    75.7%  85.8%recovery(by weight)______________________________________ 
    
     The foregoing example are intended as illustrations only and are not intended to limit the invention in any way except in the spirit and scope of the appended claims.