Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Recombinant dna technique included in method of making a...
Reexamination Certificate
1999-02-24
2003-10-28
Low, Christopher S. F. (Department: 1653)
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Recombinant dna technique included in method of making a...
C530S362000, C530S363000, C530S364000, C530S412000, C530S413000, C530S414000, C530S416000, C530S417000, C530S420000, C514S004300, C514S012200, C514S021800
Reexamination Certificate
active
06638740
ABSTRACT:
The present invention relates to purifying the protein human serum albumin (HSA) extracted from serum or recombinant human albumin (rHA) produced by transforming a microorganism with a nucleotide coding sequence encoding the amino acid sequence of human serum albumin. In this specification, the term “albumin” refers generically to HSA and/or rHA.
DETAILED DESCRIPTION OF THE INVENTION
Albumin is used to treat patients with severe bums, shock or blood loss. It is also used to supplement media used for growing higher eukaryotic cells and as an excipient in the formulation of therapeutic proteins. At present, the demand for the product is satisfied by albumin extracted from human blood. Examples of extraction and separation techniques include those disclosed in: JP 03/258 728 on the use of a cation exchanger; EP 428 758 on the use of anion exchange followed by cation exchange; and EP 452 753 on the use of heating, adding salt and diafiltering.
BACKGROUND OF THE INVENTION
The production of rHA in microorganisms has been disclosed in EP 330 451 and EP 361 991. Purification techniques for rHA have been disclosed in: WO 92/04367, removal of matrix-derived dye; EP 464 590, removal of yeast-derived colorants: and EP 319 067, alkaline precipitation and subsequent application of the rHA to a lipophilic phase having specific affinity for albumin.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a process for purifying the protein human serum albumin extracted from serum or recombinant human albumin produced by transforming a microorganism with a nucleotide coding sequence encoding the amino acid sequence of human serum albumin. The present invention provides highly purified albumin.
The present invention provides highly purified albumin.
One aspect of the present invention provides a process for purifying albumin, the process comprising the steps of applying a relatively impure albumin solution to a chromatographic material for which the albumin has no specific affinity such that albumin binds to the material, and eluting the bound albumin from the material by applying a solution of a compound having a specific affinity for albumin. Preferably, the chromatographic material is a cation exchanger, such as SP-Sepharose FF, SP-Spherosil etc, as listed below in Example 2. The compound with specific affinity for albumin may be octanoate (eg sodium octanoate), other long chain (C
6
to C
22
) fatty acids, salicylate, octylsuccinate, N-acetyltryptophan or a mixture of two or more of these.
A second aspect of the invention provides a process for purifying albumin, the process comprising the steps of subjecting an albumin solution to cation exchange chromatography in which the albumin is bound to a cation exchange material and then anion exchange chromatography in which the albumin is bound to an anion exchange material.
The albumin which is eluted from the cation exchange material may be subsequently treated by one or more of affinity chromatography, ultrafiltration and gel permeation before being subjected to the said anion exchange chromatography. Hence, in a preferred embodiment, the process comprises the steps of:
(a) passing an albumin solution through a cation exchange matrix under conditions such that the albumin will bind to the matrix:
(b) eluting from said matrix an albumin-containing cation exchange eluate:
(c) passing said eluate through an affinity matrix comprising an albumin-binding compound:
(d) eluting from said matrix an albumin-containing affinity matrix eluate:
(e) passing said eluate, optionally after ultrafiltration, through a gel permeation matrix to obtain a fraction enriched in albumin;
(f) passing the said albumin-enriched fraction through an anion exchange matrix under conditions such that albumin will bind to the matrix: and
(g) eluting from said anion exchange matrix a purified albumin-containing product.
Alternatively, the albumin which is eluted from the cation exchange material may be applied to the said anion exchange material without any intervening treatment (other than dilution). Hence, a second preferred embodiment provides a process for purifying albumin, comprising the steps of:
(a) passing an albumin solution through a cation exchange matrix under conditions such that the albumin will bind to the matrix;
(b) eluting from the matrix an albumin-containing cation exchange eluate;
(c) passing the cation exchange eluate through an anion exchange matrix under conditions such that the albumin will bind to the matrix;
(d) eluting from the anion exchange matrix an albumin-containing anion exchange eluate;
(e) passing the anion exchange eluate through an affinity matrix comprising an albumin-binding compound;
(f) eluting from the affinity matrix an albumin-containing affinity matrix eluate;
(g) passing the affinity matrix eluate through a gel permeation matrix to obtain a fraction enriched in albumin.
Preferably, prior to the cation exchange step, the albumin solution is conditioned by adding octanoate and/or other albumin stabiliser (eg sodium acetyltryptophanate) thereto to a final concentration of from about 1-10 mM and adjusting the pH to about 4.0-5.0.
Advantageously, the albumin retained in the cation exchange step is washed with a high salt solution (eg 0.5-2.0 M NaCI buffered at pH 4.0 with 10-100 mM, preferably 20-40 mM for example 27 mM sodium acetate) before being eluted.
Preferably, in processes in which the cation exchange eluate is passed directly to the anion exchanger, the albumin is eluted in the cation exchange step using a buffer containing a compound having a specific affinity for albumin, especially an acid or salt thereof, for example octanoate or any other long chain (C
6
-C
22
) fatty acid. salicylate, octylsuccinate or N-acetyltryptophan.
Suitably, the albumin is eluted from the anion exchanger with a buffer containing a high level (eg at least 50 mM, preferably 50-200 mM, for example 80-150 mM) of a boric acid salt, for example sodium or potassium tetraborate.
The albumin purified in accordance with the invention may then, with or without intervening process steps, be subjected to chromatography on a resin containing an immobilised compound which will selectively bind glycoconjugates and saccharides, such as aminophenylboronic acid (PBA).
In any process of the invention which involves affinity chromatography, the affinity chromatography preferably uses a resin comprising an immobilised albumin-specific dye, such as a Cibacron Blue type of dye, preferably immobilised on the resin via a spacer such as 1,4-diaminobutane or another spacer of C
1-8
, preferably C
1-6
, eg C
1-5
and most preferably C
4
length, preferably having &agr;,&ohgr;-diamino substitution. Surprisingly, we have found that such dyes actually have a greater affinity for a 45 kD albumin fragment which can be produced in cultures of HA-secreting microorganisms, than they do for the full length albumin molecule. The 45 kD fragment typically consists of the 1-403 to 1-409 region and is disclosed in Sleep et al (1990) Bio/Technology 8, 42-46 and in WO 95/23857.
The purified albumin solution prepared by the process of the invention may be further processed according to its intended utility. For example, it may be ultrafiltered through an ultrafiltration membrane to obtain an ultrafiltration retentate having an albumin concentration of at least about 80 g albumin per litre, with the ultrafiltration retentate being diafiltered against at least 5 retentate equivalents of water. It can be advantageous to include ammonium ions in certain chromatographic steps, for example in the step involving immobilised aminophenylboronate. Surprisingly, we have found that such ammonium ions are relatively tightly bound to the albumin. It is preferable for such ammonium ions to be removed from the albumin and we have found that this can be achieved by use of a counter-ion. The desirability of exposing the albumin to a counter-ion would not have occurred to those in this art since prior processes have not involved ammonium ions and there was no reason to suppose that ammonium ions would
Berezenko Stephen
Burton Stephen James
Goodey Andrew Robert
Johnson Richard Alan
Quirk Alan Victor
Delta Biotechnology Ltd.
Low Christopher S. F.
Mohamed Abdel A.
Seifert Arthur G.
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