PROCESS FOR PREPARATION OF
MIXTURES OF POLYPEPTIDES USING PURIFIED HYDROBROMIC ACID
5
Throughout this application various publications are
referenced by their full citations. The disclosures of
these publications in their entireties are hereby
10 incorporated by reference into this application in order
to more fully describe the state of the art to which this
invention pertains.
Background Of The Invention
15
A mixture of polypeptides which do not all have the same
amino acid sequence referred to as glatiramer acetate
(GA) is marketed under the tradename CopaxoneB and
comprises the acetate salts of polypeptides containing L-
20 glutamic acid, L-alanine, L-tyrosine and L-lysine at
average molar fractions of 0.141, 0.427, 0.095 and 0.338,
respectively. The average molecular weight of CopaxoneB
is between 4,700 and 11,000 daltons. ("Copaxone",
Physician's Desk Reference, (2000), Medical Economics
25 Co., Inc., (Montvale, NJ) , 3115. ) Chemically, glatiramer
acetate is designated L-glutamic acid polymer with Lalanine,
L-lysine, L-tyrosine, acetate (salt). Its
structural formula is:
(Glu, Ala, Lys, Tyr) ,-xCH3COOH
(CsHgN04 C3H7N02 CsH14N202 C9HllN03) xC2H402 ,
CAS - 147245-92-9
("Copaxone", Physician's Desk Reference, (2000) , Medical
35 Economics Co., Inc., (Montvale, NJ), 3115.)
Glatiramer acetate is approved for reduction of the
frequency of relapses in patients with relapsingremitting
multiple sclerosis. Multiple sclerosis has been
classified as an autoimmune disease. Glatiramer acetate
has also been disclosed for use in the treatment of other
autoimmune diseases (Publication No. US 2002/0055466 A1
for R. Aharoni et a inflammatory non-autoimmune
5 diseases (Publication No. US 2005/0014694 A1 for V. Wee
Yong et al.; and U.S. Patent Application No. 2002/0077278
Al, published June 20, 2002 (Young et al.)) and to
promote nerve regeneration and/or to prevent or inhibit
secondary degeneration which may follow primary nervous
10 system injury (Publication No. US 2003/0004099 A1 for M.
Eisenbach-Schwartz et al.; and U.S. Patent Application
No. 2002/0037848 Al, published March 28, 2002 (Eisenbach-
Schwartz) ) . Furthermore, glatiramer acetate has been
disclosed as a treatment for immune mediated diseases
15 (e.g., U.S. Patent No. 6,514,938 B1, issued February 4,
2003 (Gad et a1 . ) ; PCT International Publication No. WO
01/60392, published August 23, 2001 (Gilbert et al. ) ; and
PCT International Publication No. WO 00/27417, published
May 19, 2000 (Aharoni et al.) as well as diseases
20 associated with demyelination (PCT International
publication No. WO -1/97846, published December 27, 2001
(Moses et al. ) .
The manufacturing process as detailed in the above patents
25 involves reacting protected polypeptides with 33%
hydrobromic acid in acetic acid. (U.S. Patent No.
5,800,808, issued September 1, 1998 to Konfino, et al.)
This deprotection reaction removes the gamma benzyl
protecting group from the 5-carboxylate of the glutamate
30 residue and cleaves the polymer to smaller polypeptides to
form a trifluoroacetyl polypeptide. (U.S. Patent No.
5,800,808, issued September 1, 1998 to Konfino, et al.)
The time needed to obtain GA of the proper average
molecular weight of between 7,000+2,000 daltons depends on
the reaction temperature and the molecular weight profile
of the protected glatiramer acetate. (U.S. Patent No.
5,800,808, issued September 1, 1998 to Konfino, et al.)
5 The deprotection occurs at a temperature of between 20°C
and 2 8 " ~ (U.S. Patent No. 5,800,808, issued September 1,
1998 to Konfino, et al.). A test reaction is performed on
every batch at different time periods to determine the
reaction time needed at a given temperature to achieve
10 trifluoroacetyl polypeptides of a proper molecular weight
profile. (U.S. Patent No. 5,981,589, issued November 9,
1999 to Konfino, et al.) The amount of time needed for the
reaction ranges, for example, between 10 and 50 hours.
(U.S. Patent No. 5,800,808, issued September 1, 1998 to
15 Konf ino, et al. ) . In addition, U. S . Patent Nos. 5,981,589,
6,048,898, 6,054,430, 6,342,476, 6,362,161, and 6,620,847,
also relate to compositions and methods for manufacture of
mixtures of polypeptides, including GA.
20 This invention provides an improved manufacturing process.
Summary Of The Invention
The subject invention provides a process for obtaining a
mixture of trifluoroacetyl polypeptides which do not all
5 have the same amino acid sequence, where each polypeptide
consists essentially of alanine, glutamic acid, tyrosine
and trifluoroacetyl lysine, wherein the mixture has a
desired average molecular weight and wherein during the
process a batch of a mixture of polypeptides, each of
10 which consists essentially of alanine, y-benzyl glutamate,
tyrosine and trifluoroacetyl lysine is deprotected with- a
solution of hydrobromic acid in acetic acid, the
improvement comprising use of a solution of hydrobromic
acid in acetic acid, which solution comprises less than
15 0.5% of free bromine.
The subject invention also provides a process for
obtaining a mixture of trifluoroacetyl polypeptides which
do not all have the same amino acid sequence, where each
20 polypeptide consists essentially of alanine, glutamic
acid, tyrosine and trifluoroacetyl lysine, wherein the
mixture has a desired average molecular weight and
wherein during the process a batch of a mixture of
polypeptides, each of which consists essentially of
25 alanine, y-benzyl glutamate, tyrosine and trifluor~acet~l
lysine is deprotected with a solution of hydrobromic acid
in acetic acid, , the improvement comprising use of a
solution of hydrobromic acid in acetic acid, which
solution comprises less than 1000 ppm of' metal ion
30 impurities.
The subject invention further provides process of
producing a mixture of trifluoroacetyl polypeptides which
do not all have the same amino acid sequence, where each
polypeptide consists essentially of alanine, glutamic
acid, tyrosine and trifluoroa'cetyl lysine, wherein the
mixture has a desired average molecular weight comprising
5 deprotecting a mixture of polypeptides .each consisting'
essentially of alanine, y-benzyl glutamate, tyrosine and
trifluoroacetyl lysine with a solution of hydrobromic
acid in acetic acid, which solution comprises less than
0.5% of free bromine and less than 1000 ppm of metal ion
10 impurities.
The subject invention also provides a composition
comprising the trifluoroacetyl product produced by any
one of the subject invention processes, and a carrier.
15
The subject invention further provides a mixture of
trifluoroacetyl polypeptides which do not all have the
same amino acid sequence, where each polypeptide consists
essentially of alanine, glutamic acid, tyrosine and
20 trifluoroacetyl lysine, wherein the mixture has a desired
average molecular weight, no more than 0.1% brominated
tyrosine and less than 1000 ppm metal ion impurities.
The subject invention also provides a compo.sition
comprising the mixture of trifluoroacetyl polypeptides
25 and a carrier.
The subject invention also provides process for'obtaining
a pharmaceutical composition containing a mixture of
polypeptides which do not all have the same am'ino acid
30 sequence., where each polypeptide consists essentially of
alanine, glutamic acid, tyrosine and lysine, and wherein
the mixture has a desired average molecular weight, which
comprises
a) polymerizing. N-carboxyanhydrides of tyrosine,
alanine, y-benzyl glutamate and Ntrifluoroacetyl
lysine to form a mixture of
protected polypeptides;
b) deprotecting the protected polypeptides with a
solution of hydrobromic aci-d in acetic acid,
the solution comprises less than 0.5% of free
bromine and less than 1000 ppm of metal ion .
impurities, to . form a . mixture of
trifluoroacetyl polypeptides;
C) reacting the a mixture of trifluoroacktyl
polypeptides with aqueous piperidine to form a
'solution of aqueous mixture of polypeptides,
each of which consists essentially of alanine,
glutamic acid, tyrosine and lysine; and
d) purifying the mixture of polypeptides.
The subjection invention further 'provides process of
producing glatiramer acetate comprising the steps of:
a) polymerizing, N-carboxyanhydrides of tyrosine,
alanine, y-benzyl glutamate and N- .
trifluoroacetyl lysine to form protected
glatiramer acetate;
b) deprotecting protected glatiramer acetate with
a solution of hydrobromic acid in acetic acid,
the solution comprises less than 0.5% of free
bromine and less than 1000 ppm of metal ion
impurities, to form trifluoroacetyl glatiramer
acetate;
C) reacting trifluoroacetyl glatiramer acetate
with aqueous piperidine to form a solution of
glatiramer acetate; and
d) , purifying the glatiramer acetate.
10 The subject invention yet further provides a method of
analyzing the percentage of brominated tyrosine in. a
sample of glatiramer acetate comprising the steps of:
a) hydrolyzing glatiramer acetate .to obtain a
hydrolyzate;
b) eluting the hydrolyzate through a
chromatographic column;
20 C) measuring the level of bromotyrosine in the
hydrolyzate;
d) preparing sample solutions of the amino acid
components of glatiramer acetate and of
25 bromotyrosine;
e) eluting the ,sample solutions through .the column
of step 'b) ; and
e) calculating the percentage of brominated
tyrosine in the glatiramer acetate.
The subject invention also provides a process for
preparing a pharmaceutical composition containing a
mixture of polypeptides which do not all have the same
amino acid sequence, where each polypeptide consists
essentially of glutamic acid, alanine, tyrosine and
5 lysine, wherein the mixture has a predetermined
percentage of brominated tyrosine acceptable for
inclusion in a pharmaceutical composition, which
comprises obtaining a batch of a mixture of polypeptides
having nonuniform amino acid sequences, where each
10 polypeptide consists essentially of glutamic acid,
alanine, tyrosine and lysine;
measuring the percentage of brominated tyrosine of
the batch by a process comprising
15 a) hydrolyzing the batch to obtain a hydrolyzate;
b) eluting the hydrolyzate through a
chromatographic column;
20 C) measuring the level of bromotyrosine in the
hydrolyzate;
d) preparing sample solutions of the amino acid
components of the batch and of bromotyrosine;
e) eluting the sample solutions through the column
of step b); and
f) calculating the. percentage of brominated
tyrosine in the batch; and
inluding in the pharmaceutical composition
a batch, only if its percentage of brominated'
tyrosine so measured is less than 0.3%.
Detailed Description Of The Invention
The subject invention provides a process for obtaining a
mixture of trifluoroacetyl polypeptides which do not all
5 have the same amino acid sequence, where each polypeptide
consists essentially of alanine, glutamic acid, tyrosine
and trifluoroacetyl lysine, wherein the mixture has a
desired average molecular weight and wherein during the
process a batch of a mixture of polypeptides, each of
10 which consists essentially of alanine, y-benzyl glutamate,
tyrosine and trifluoroacetyl lysine is deprotected with' a
solution of hydrobromic acid in acetic acid, the
improvement comprising use of a solution of hydrobromic
acid in acetic acid, which solution comprises less than
15 0.5% of free bromine.
In one embodiment,. the improvement further comprises use
of a solution of hydrobromic acid in acetic acid that
comprises less than 1000 ppm of metal ion impurities.
20
The subject invention further provides a process for
obtaining a mixture of trifluoroacetyl polypeptides which
do not all have the same amino acid sequence, where each
polypeptide consists essentially of alanine, glutamic
25 acid, tyrosine and trifluoroacetyl lysine, wherein the
mixture has a desired average molecular weight and
wherein during the process a batch of a mixture of
polypeptides, each of which consists essentially of
alanine, y-benzyl glutamate, tyrosine and trifluoroacetyl
30 lysine is deprotected with a solution of hydrobromic acid
ln acetic acid, the improvement comprising use of a
solution of hydrobromic acid in acetic acid, which
solution comprises less than 1000 ppm of metal ion
10
impurities.
The subject invention yet further provides a process of
producing a mixture of trifluor~acet~plo lypeptides which
5 do not all have the same amino aci'd sequence, where each
polypeptide consists essentially of alanine, glutamic
acid, tyrosine and trifluoroacetyl lysine, wherein the
mixture has a desired average molecular weight comprising
deprotecting a mixture of polypeptides each consisting
10 essentially of alanine, y-benzyl glutamate, tyrosine and
trifluoroacetyl lysine with a solution of hydrobromic
acid in acetic acid, which solution comprises less than
0.5% of free bromine and less than 1000 ppm of metal ion
impurities .'
one embodiment, the solution hydrobromic acid
acetic acid comprises less than 0.1% of free bromine.
In another embodiment, the solution of hydrobromic acid
20 in acetic acid comprises less than 0.05% of,free bromine.
In a further embodiment, the solution of hydrobromic acid
. .
in acetic acid comprises less than 0.01% of free bromine.
25 In yet another embodiment, the solution of hydrobromic
acid in acetic acid comprises less than 0.001% of free
bromine.
In a' further embodiment, the solution of hydrobromic acid
30 in acetic acid is free of free bromine.
In another embodiment, the solution of hydrobromic acid
in acetic acid comprises less than 1000 ppm of metal ion
impurities.
In yet another embodiment, the solution of hydrobromicacid
in acetic acid comprises less than 500 ppm of metal
5 ion impurities.
In one embodiment, the solution of hydrobromic acid in
acetic acid comprises less than 100 ppm of metal ion
impurities.
10
In another embodiment, the solution of hydrobromic acid
in acetic acid comprises less than 30 ppm of metal ion
impurities.
15 in yet another embodiment, the solution of 'hydrobromic
acid in acetic acid comprises less than 20 -ppm of metal
ion impurities.
., . .
In a further embodiment, the solution of hydrobromic acid
20 in acetic acid comprises less than '10 ppm of metal ion
impurities.
In another embodiment, the solutiori of hydrobromic acid
in acetic acid is free of metal ion impurities.
25
In yet another embodiment, the mixture of trifluoroacetyl
polypeptides is t. r. ifluoroacetyl glatiramer acetate ("TFA
GA") .
30 In an embodiment, the .hydrobromic acid in acetic acid
solution is from 10% 'to 36% hydrobromic acid in acetic
acid. In another embodiment, the hydrobromic acid in
acetic acid is from 16% to 33% hydrobromic acid in acetic
acid; 18% to 33% hydrobromic acid in acetic acid; 20% to
37% hydrobromic acid in acetic acid; 20% to 33%
hydrobromic acid in acetic acid; 22% to 33% hydrobromic
acid in acetic acid; 24% to 33% hydrobromic acid in
5 acetic acid; 25% to 35% hydrobromic acid in acetic acid;
26% to 33% hydrobromic acid in acetic acid; 28% to 33%
hydrobromic acid in acetic acid; 30% to 34% hydrobromic
acid is acetic acid; 30% to 33% hydrobromic acid in
acetic acid; or 32% to 33% hydrobromic acid in acetic
10 acid. In a further embodiment, the solution is 33%
hydrobromic acid in acetic acid. In another embodiment,
the solution is 16% hydrobromic acid in acetic acid.
In another embodiment, the solution is pretreated with a
15 bromine scavenger in order to remove free bromine.
In one embodiment, the bromine scavenger is phenol.
In a further embodiment, the solution is produced in a
20 non-metallic reactor.
In another embodiment, the. solution is prepared in a
glass-lined or Teflon lined reactor.
25 In yet another embodiment, the color of the hydrobromic
acid in acetic acid solution is less than 2000 APHA.
In a further embodiment, the color of the hydrobromic
acid.in acetic acid solution. is less than 1000 APHA.
30
In. another embodiment, the color of the hydrobromic acid
in acetic acid solution is less than 700 APHA.
In yet another embodiment, the color of the hydrobromic
acid in acetic acid solution is less than 500 APHA.
The subject invention also provides a trifluoroacetyl
5 product produced by any one of the disclosed processes.
The subject invention further provides a composition
comprising the trifluoroacetyl product produced by any
one of the disclosed processes, and a carrier.
10
The subject invention yet further provides a mixture of
trifluoroacetyl polypeptides which do not all have the
same amino acid sequence, where each polypeptide consists
essentially of alanine, glutamic acid, tyrosine and
15 trifluoroacetyl lysine, wherein the mixture has a desired
average molecular weight, no more than 0.1% brominated
tyrosine and less than 1000 ppm metal ion impurities.
In one embodiment, the mixture of trifluoroacetyl
20 polypeptides has an average 'molecular weight from 2000
daltons to 40,000 daltons.
In another embodiment, the mixture of trifluoroacetyi
polypeptides has an average molecular weight from 4000
25 daltons to 18,000 daltons.
In a further embodiment, the mixture of trifluoroacetyl
polypeptides has an average molecular weight from 4000
daltons to 13,000 daltons.
30
In. another embodiment, the mixture of trifluoroacetyl
polypeptides has an average molecular weight from 13,000
daltons to 19,000 daltons.
In yet another embodiment., the mixture of trifluoroacetyl
polypeptides has an average molecular weight from 13,500
daltons to 18,500 daltons.
5
In a further embodiment, the mixture of trifluoroacetyl,
polypeptides has an average molecular weight of 7,000
+2,000 daltons . . .
10 In yet a further embodiment, the mixture of
trifluoroacetyl polypeptides has an. average molecular
weight of 7,000 daltons.
In another embodiment, the mixture of trifluoroacetyl
15 polypeptides has an average molecular weight of 14,000
daltons.
In yet another embodiment, the mixture of trifluoroacetyl
polypeptides has an average molecular weight from 4,700 -
20 11,000 daltons.
In a further embodiment, the mixture of trifluoroacetyl
polypeptides comprises less than 1000 ppm of metal ion
impurities.
25
In yet another embodiment, the mixture of trifluoroacetyl
polypeptides comprises less than 500 ppm of metal ion
impurities.
30 In a further embodiment, the mixture of trifluoroacetyl
polypeptides comprises, less than 100 ppm of metal ion
impurities.
In another embodiment, the mixture of trifluoroacetyl
polypeptides comprises less than 30 ppm of metal ion
impurities.
5 In a further embodiment, the mixture of trifluoroacetyl
polypeptides comprises less than 20 ppm of metal ion
~mpurltles.
In another embodiment, the mixture of trifluoroacetyl
10 polypeptides comprises. less than 10 ppm of metal ion
impurities.
In yet another embodiment, the mixture of trifluoroacetyl
polypeptides is free of metal ion impurities.
15
The subject invention also provides a composition
comprising the mixture of trifluoroacetyl polypeptides
and a carrier.
20 The subject invention further provides a process for
obtaining a pharmaceutical composition containing a
mixture of polypeptides which do not all have the same
amino acid sequence, where each polypeptide consists
essentially of alanine, glutamic acid, tyrosine and
25 lysine, and wherein the mixture has a desired average
molecular weight, which comprises
a) polymerizing N-carboxyanhydrides of tyrosine,
alanine, y-benzyl glutamate and N-trifluoroacetyl
lysine to form an aqueous mixture of protected
polypeptides;
b) deprotecting the protected polypeptides with a
solution of hydrobromic acid in acetic acid, which
solution comprises less than 0.5% of free br'omine
and less than 1000 ppm of metal ion impurities, to
form an aqueous mixture of trifluoroacetyl
polypeptides;
5
C) reacting the an aqueous mixture of trifluoroacetyl
polypeptides with aqueous piperidine to form a
solution of aqueous mixture of polypeptides, each of
which consists essentially of aIanine, glutamic
10 acid, tyrosine and lysine; and
d) purifying the aqueous mixture of polypeptides.
In one embodiment, the average mole fraction in the
15 mixture is glutamic acid 0.129-0.159; alanine ' 0.392-
0.462; tyrosine 0.086-0.100; and lysine 0.300-0.374. In
a specific embodiment-, the average mole fraction in - the
mixture of glutamic acid is 0.141, of alanine is 0.427,
of tyrosine is 0.093, and of lysine is 0.337.-
20
The subject invention also provides a process of
producing glatiramer acetate comprising the steps of:
a) polymerizing N-carboxyanhydrides of. tyrosine,
alanine, y-benzyl glutamate and N-trifluoroacetyl
25 lysine to form protected glatiramer acetate;
b) deprotecting protected glatiramer. acetate with a
solution of hydrobrbmic acid in acetid acid, the
'solution comprises less than 0.5% of free bromine
and less than '1000 ppm of metal ion impurities, to
form trifluoroacetyl glatiramer acetate;
C) reacting trifluoroacetyl glatiramer acetate with
aqueous piperidine to form a solution of glatiramer
acetate; and
d) purifying the glatiramer acetate.
In one embodiment, the product of the step d) Is further
subjected to ultrafiltration to remove polypept'ide
species with molecular weight less than 5000 daltons.
In an embodiment, the hydrobromic acid in acetic acid
solution is from 10% to 36% hydrobromic acid in acetic
acid. In another embodiment, the hydrobromic acid in
acetic acid is from 16% to 33% hydrobromic acid in acetic
acid; 18% to 33% hydrobromic acid in acetic acid; 20% to
37% hydrobromic acid in acetic acid; 20% to 33%
hydrobromic acid in Acetic acid; 22%. td 33% hydrobromic
acid in acetic acid; 24% to 33% hydrobromic acid in
acetic acid; 25% to 35% hydrobromic acid in acetic acid;
26% to 33% hydrobromic acid 'in acetic acid; 28% to 33%
hydrobromic acid in acetic acid; 30% to 34% hydrobromic
acid is acetic acid; 30% to 33% hydrobromic acid in,
acetic acid; or 32% to 33% hydrobromic acid in acetic
acid. In a further embodiment, the solution is 33%
hydrobromic acid in acetic acid. In another embodiment,
the solution is 16% hydrobromic acid in acetic acid.
In another embodiment, the hydrobromic acid in acetic
acid solution is pretreated with a bromine scavenger in
order to remove free bromine.
In yet another embodiment, the bromine scavenger is
phenol.
In a further embodiment, the hydrobromic acid in acetic
acid solution is produced in a non-metallic reactor.
5 In another embodiment, the hydrobromic acid in acetic.
acid solution is prepared in a glass-lined or Teflon
lined reactor.
In one embodiment, the color of the hydrobromic acid in
10 acetic acid solution is less than 2000 APHA.
In another embodiment, the color of the hydrobromic acid
in acetic acid solution is less than 1000 APHA.
15 In yet another embodiment, the color of the hydrobromic
acid in acetic acid solution is less than 700 APHA. . .
In a further embodiment, the color of the.hydrobromic
acid in acetic acid solution is less than 500 APHA.
20
The subject. invention further provides method of
analyzing the percentage of brominated tyrosine in a
sample of glatiramer acetate comprising 'the steps of:
a) hydrolyzing glatiramer acetate to ,obt'ain a
25 hydrolyzate;
b) eluting the hydrolyzate through a chromatographic
column;
C) measuring the level of bromotyrosine in the
hydrolyzate;
19
d) preparing sample solutions of the amino acid
components of glatir.amer. acetate and of
bromotyrosine;
e) eluting the sample solutions through the column of
5 step b); and
f) calculating the percentage of brominated tyrosine in
the glatiramer acetate.
The subject invention also , provides a process for
10 preparing a pharmaceutical composition containing a
mixture of polypeptides which do not all have the same
amino acid sequence, where each polypeptide consists
essentially of glutamic acid, alanine, tyrosine and
lysine, wherein the mixture has a predetermined
15 percentage of brominated tyrosine ' aci=eptable for
inclusion in a pharmaceutical composition, which
comprises obtaining a batch of a mixture of polypeptides
having nonuniform amino acid sequences, where each
polypeptide consists essentially of glutamic acid,
20 alanine, tyrosine and lysine;
measuring the percentage of brorr-inated tyrosine ~f the
batch by a process comprising
a) hydrolyzing the batch to obtain a hydrolyzate;
b) eluting the hydrolyzate through a chromatographic
column;
.c)measuring the level of bromotyrosine in the
hydrolyzate;
d) preparing sample solutions of the amino acid
components of the batch and of bromotyrosine;
e) eluting the sample solutions through the column of
step b); and
5 f) calculating the percentage of br~mina~etdy rosine in
the batch; and
including in the pharmaceutical composition a
batch only if its percentage of brominated tyrosine s'o
measured is less than 0.3%.
10
In one embodiment, the batch is acceptable for inclusion
in the pharmaceutical composition only if its percentage,
of brominated tyrosine so measured is less than 0.2%.
15 In another embodiment, the batch is acceptable for
inclusion in the pharmaceutical composition only if its
percentage of brominated tyrosine so measured is less than
0.1%-
20 In a further embodiment, the mixture of polypeptides is
glatiramer acetate ("GA") .
TERMS
The term "average molecular weight" as used in this
25 application means the molecular weight of the species of
polypeptides present in the mixture in the highest
relative proportion (i. e . the peak maximum) when the
mixture is subjected to separation by molecular weight on
an HPLC gel permeation column. This value can be
30 obtained in several ways, e.g. from the retention time on
a calibrated column; or from a correlation between the
21
location of the peak and the location of the
cochromatographed copolymer markers of. defined sequence
and molecular weight. Other 'methods of determining an
average molecular weight such as by light scattering may
5 be employed and will correspond substantially to the
value obtained from the peak maximum.
A polypeptide mixture according to this invention as
exemplified is the acetate salt of synthetic polypeptides
10 prepared by chemically reacting four activated amino acid
derivatives (two of them L-Glutamic acid and L-lysine
protected): L-Glutamic acid (L-Glu), L-alanine (LAla),
L-tyrosine (L-Tyr) and L-lysine (L-Lys) (two of
them protected i.e. 5Bz-Glutamate derivative and 6N-TEA-
15 Lysine derivative)in a specified ratio. The term
"mixture" as used in this document generally refers to in
the "mixture of polypeptides of the invention" comprising
L-glutamic acid, L-alanine, L-tyrosine, and L-lysine, and
both terms are meant to include residual impurities from
20 the manufacturing process.
The molar fraction range of each amino acid residue is:
L-Glu 0.129-0.153, L-Ala 0.392-0.462, L-Tyr 0.086-0.100
and L-Lys 0.300-0.374.
25 Because no reaction goes to completion 100% and although
practically all impurities are eliminated, small amounts
can remain. such impurities may be of ,the following
three types:
Structure-related substances, which are protected
amino acid residues such as 5-BZ-L-glutamyl and/or
N6-TEA-L-Lysyl residues, originating from
incomplete removal of the protecting groups. In
addition, the polypeptide mixture of the invention
molecules may contain brominated L-tyrosyl residues,
formed during production due to the presence of free
bromine in the HBr/acetic acid reagent.
The molecular structures of the identified
structure-related impurities can be derived from'the
participating monomers i-e. starting materials.
These identified impurities are quantified (after
chemical conversion) by comparison to the specific
Reference Standards, which are either derivatives or
part of the impurities themselves:
- .Residual trifluoroacetyl compounds (expressed as
fluoride)
- Residual benzylated glutamyl residues (expressed
as benzyl bromide)
- Residual brominated tyrosyl residues (expressed
as bromotyrosine)
Unidentified related substances (determined by RPHPLC):
these are small molecular size polypeptides
.of the same origin with similar structures. These
substances probably have similar response factors
and the concentration ( % ) of each impurity can be
calculated as % peak area relative to the the
polypeptide mixture of the invention peak area.
The characterization of the impurities is based on
their relative chromatography retention time (RRT)
relative to the L-Tryptophan standard.
Residual solvents and inorganic impurities covered
in the specification such as the residual solvent
5 1,4 dioxane, residual piperidine and heavy metals.
DISCUSSION
10 Free Bromine
In the manufacturing process for mixtures of polypeptides,
such as GA, 33% hydrobromic acid in acetic acid is used to
deprotect protected GA. For example, during the
development of the production process for GA it was found
15 that some of the tyrosine residues in trifluoroacetyl GA
(TFA GA) and in GA were brominated. This impurity was
isolated and identified using an analytical procedure that
is described in detail in the examples. The tyrosine
residue was found to react with bromine to form a mono-
20 bromotyrosine moiety comprising either 2-bromotyrosine or
3-bromotyrosine.
After much investigation the inventors discovered that the
brominated tyrosine impurity was introduced into the GA
25 through free bromine in HBr/acetic acid. The free bromine
was present in 33% HBr/acetic acid bought from a supplier
and used in the production process.
Measures were taken in order to decrease the level of free
30 bromine in 33% HBr/acetic acid. For example, pre-treatment
..of HBr/acetic acid with a bromine scavenger was effective
in removing some of the free bromine from the HBr/acetic
acid solution.
One of the bromine scavengers used in the HBr purification
process was phenol. In addition to phenol, other reducing
agents, such as sodium bisulfite, may be used. Phenol was
5 chosen as a bromine scavenger because it and its reaction
product with bromine (bromophenols) are both essentially
non-reactive with protected polypeptides, such as
protected GA, TFA polypeptides, such as TFA GA and
polypeptides, such as GA, and they are easy to remove from
10 the solution of GA during the purification process.
Similarly, any bromine scavenging agent may be used
provided that it, and its reaction product with bromine,
are not reactive with protected polypeptides, such as
protected GA, TFA polypeptides, such as TFA GA and
15 polypeptides, such as GA, and it is easily removable
during the final purification process.
Metal Impurities
GA is marketed in two pharmaceutical dosage forms,
20 lyophilized powder and pre-filled syringes. The syringes,
marketed under the trade name CopaxoneB Injection,
generally contained clear solution. The storage
instructions weze to keep the syringes refri jerated.
However, red color in aqueous solutions of CopaxoneB pre-
25 filled solutions was detected. The source of the color in
the solutions was unknown.
The color appeared when the solutions were kept at room
temperature for 12 to 24 hours.
3 0
It was determined that production of HBr in metal
apparatus led to trace metallic ion impurities in the HBr.
When HBr was later mixed with protected GA, the metallic
ion impurities in the HBr were chelated by TEA GA and GA.
These TEA GA and GA/metal complexes contributed to the
coloration.
5 As a result, another measure taken to ensure purity, e. g.,
in the GA product, was the use of a non-metal reactor for
the production of 33% HBr/acetic acid solution. The
reactor used for the production of HBr/acetic acid
solution was glass lined in order to prevent the formation
10 of impurities which could later affect the purity of,
e.g. ,. the GA. In order to prevent contact of HBr solution
with metal, parts of the piping used were Teflon-lined.
Simil.arly, other types of non-reactive, acid resistant
non-metal apparatus can be used to prevent the formation
15 of trace metal ions in 'the HBr/acetic acid solution. The
use of a non-metal 'apparatus for the production of
HBr/acetic acid solution was successful in eliminating the
red color from the GA; When. the non-metal apparatus :was
used for the production of the HBr/acetic acid solution,
20 the' result was that the solution was' essentially free of
metal ions and the red GA was not formed.
In addition, the color of every batch of HBr/acetic acid ,
is measured to determine level of impurities before being
25 used to deprotect protected GA. It was found that levels
of metal ion impurity in HBr solution could be determined
by visual analysis. HBr solution with a color below 2000
APHA was shown to produce glatiramer acetate without red
color.
30
The invention will be exemplified but not limited by the
following examples.
EXPERIMENTAL DETAILS
EXAMPLE 1 - INFLUENCE OF BROMINE CONCENTRATION IN
HBR/ACETIC ACID ON BROMOM'NATED TYROSINE MOIETY IN TEA GA
5 AND IN GA
In order to determine the effect of free bromine in
hydrobromic acid/ acetic acid on the level of brominated
tyrosine moiety impurity in TEA-GA and GA, hydrobromic
10 acid in acetic acid was contaminated with various amounts
of bromine. In the experiment, HBr which was not
pretreated with bromine scavenger was used in the
manufacturing process. Various levels of bromine impurity
(measured as percentage of HBr/Acetic acid solution) were
15 added. The level of brominated tyrosine moiety impurity
in TFA GA and in GA was measured by hydrolyzing TEA GA
and GA to its amino acid components, and then using HPLC
to determine the amount of bromotyrosine in relation to
the TEA GA and GA.
20
PROCEDURE
Preparation of standard solutions
Standard solutions containing 2 pg/mL Bromotyrosine were'
prepared using distilled water. Amino acid standard stock
25 solution was prepared.using the following amino acids:
The amino acids were dissolved in water.,A few dropsof 5
N NaOH were added and water was added to a final volume
L-Glu
L-Ala
L-Tyr
L- Lys HC1
About 100 mg
About 130 mg
About 75 mg
About 200 mg
Hydrolysis
10 mg of glatiramer acetate and 10 mg of TEA GA were each
5 independently weighed into 5 mL hydrolysis vials. A
negative control vial was prepared by adding 0.5 mL of
the amino acid standard stock solution to a 5 mL
hydrolysis vlal. 0.5 mL of water and 0.5 mL of
concentrated HC1 containing 1% of phenol were added to
10 each of the vials. The vials were heated to llO°C for 24
hours, under N2 atmosphere. The samples .were then cooled
to room temperature. Each of the hydro'lyzates were
transferred to, 5 mL :volumetric flasks and filled to
volume with distilled water.
15
Chromotography
The bromotyrosine standard, and each of the hydrolyzates,
were independently eluted through an HPLC column using an
eluent of acetonitrile : water : acetic aci.d in a ratio
20 of 4 : 95 : 1. The column was equipped' with an UV
detector and data recording system. The amino acid
standard is used as a negative control to determine which
peak in the glatiramer acetate hydiolyzate corresponds to
bromotyrosine.
25
Data Analysis
The percentage of brominated tyrosine moiety in each TEA
GA and GA sample was calculated as follows:
P = purity of bromotyrosine standard (in percent)
30 As = Area of bromotyrosine standard peak
Ap = Area of bromotyrosine peak in each sample
Cs = Concentration of bromotyrosine standard (pg/mL)
Cp = Concentration of glatiramer acetate (or of TEA GA)
Ap ' Cs
% Brominated tyrosirie = p*-*-
As Cp
Table 1 shows the effect of free Bromine on the level of
brominated tyrosine moiety in TEA Glatiramer Acetate and
5 in Glatiramer Acetate
Table 1. Effect Of Free Bromine On The Level
Of Brominated Tyrosine Moiety
5 Results
Bromine ( % )
No added Bromine
0.5
1
5
From the above example it can be seen that contamination
of HBr with bromine leads to higher levels of brominated
tyrosine moiety in TEA GA and in GA, , relative to the
Brominated tyrosine ( % )
standard reaction in which no bromine was added. When no
10 bromine was added, since the HBr was not treated with a
bromiie scavenger, some free ,bromine was still available
TEA Glatiramer
0.1
0.7
1.2
4
and brominated tyrosine moiety contamination of GA and
Glatiramer Acetate
0.2
1.2
2.2
No Data
TEA GA was still evident.
15 In order to produce GA with brominated tyrosine moiety
impurity at a level of less' than 0.2%, the level of free
Bromine in HBr must be lowered by the addition of a
bromine scavenger.
30
EXAMPLE 2 - PRODUCTION OF 33% HBR IN ACETIC ACID SOLUTION
The glass-lined reactor is rinsed with acetic acid, then
emptied. 1013 kg of acetic acid is added into the reactor.
5 The acetic acid is maintained at a temperature of 10-20°C.
522 kg of HBr gas is introduced into the reactor while
mixing the solution. After the gas is introduced, the
solution is mixed for an additional 30 minutes. The
solution is tested to determine if HBr content is 33%.
10 .. .
EXAMPLE 3 - PURIFICATION OF HBR/ ACETIC ACID SOLUTION
USING PHENOL AS A BROMINE SCAVENGER
A solution of 33% HBr i n a c e t i c acid was poured i n t o a
5 glass-lined r e a c t o r . Phenol was weighed and added t o the
HBr solution in a weight r a t i o of 1 t o 100. The s o l u t i o n
was then s t i r r e d for 12 t o 24 hours. The p u r i f i e d HBr
s o l u t i o n is then added t o protected glatiramer a c e t a t e .
The reaction of the HBr with protected GA forms TFA GA.
10 The TFA GA is reacted with piperidine t o form GA.
EXAMPLE 4 - LEVELS OF BROMINATED TYROSINE IN VARIOUS
BATCHES
The level of Brominated tyrosine moiety in various batches
5 of glatiramer acetate was measured using the method
described in example 1.
Results
The HBr produced using the new method, as described in
example 2 and treated with phenol as in example 3, was
free of Bromine and metallic impurities. Therefore the
glatiramer acetate which was produced was substantially
free of brominated tyrosine moiety.
Method of
Production
OLD METHOD
NEW METHOD
The HBr which was bought from external suppliers (old
. .
method) had impurities, and theref ore the glatiramer
acetate produced using it also had brominated tyrosine
moiety impurities, even though phenol was used as a
tyrosine scavenger.
Batch Number
of GA
A
B
C
D
E
X
Y
Z
Brominated tyrosine
moiety concentration
0.15
0.19
0.14
0.15
0.32
None detectable
None detectable
None detectable
EXAMPLE 5 - COLOR DETERMINATION
The color of the HBr/acetic acid solution was determined
using standard visual color determination techniques.
The American Public Health Association (APHA) color index
is a single number yellowness index where each APHA unit
is based on a dilution of the 500 ppm stock solution of
platinum-cobalt (PtCo). (HunterLab, APHA Background,
Applications Note, Insight on Color November 16-30, 1996,
Vol . 8 I No. 16. a v a i l a b l e a t
http://www.hunterlab.com/appnotes/anll 96br2.pdf.) The
APHA measurement is determined by visual comparison of the
solution with PtCo standards that contain controlled
amounts of potassium chloroplatinate and cobaltous
chloride. Each number unit is the equivalent of 1 mg of
platinum per liter of solution (pprn) . . The standards and
corresponding measurements are designated according to
their ppm measurement, i.e. the No. 20 APHA standard
contains 20 ppm of platinum. American Chemical Society,
General Directions and Procedures: Measurement of Physical
Properties a v a i l a b l e a t
http://pubs.acs.org/reaqent demo/sec ~002.html.), distille
water has an APHA value of 0, and the stock solution has
an APHA value of 500 ppm. (HunterLab, APHA Background,
Applications Not, Insight on Color, November 16-30, 1996,
Vol . 8 I No. 16. a v a i l a b l e a t
http://www.hunterlab.com/appnotes/anll 96br2.pdf.) The
APHA measurement may be made by various instruments well
known in the art.
APHA color standard "500" and APHA color standard "1.000"
were prepared. APHA color standard "500" was prepared ,by
dissolving 1.246 g Potassium Chloroplatinate, K2PtC16
(equivalent to 50 mg metallic Platinum) and 1.00 g
crystallized Cobaltous Chloride, CoC12-6H20 (equivalent to
about 250 mg metallic Cobalt) in distilled water with 100
5 ml concentrated HC1 and was diluted to 1000 mL with
distilled water.
APHA color standard' "1000" was prepared by dissolving
2.492 g Potassium Chloroplatinate K2PtC16 and 2.00 g
10 crystallized Cobaltous Chloride CoC12-6H20 in distilled
water with 200 mL concentrated HC1 and was diluted to 1000
mL with distilled water.
20
. ,
The color of these batches of HBr/acetic acid indicated
that they were essentially free of bromine and metal ion
impurities. Because the color was less than 2000 APHA,
25 these batches were considered essentially free of metal
ion impurities.
The following batches were produced using non-metal
15 apparatus as described previously. These samples were
color-tested visually against the color standards by
viewing 100mL Nessler tubes vertically against a white
background.
Batch Number
M
N
P
Q
R
Color (APHA)
<500
<500
700
3 5 0
<3 0 0
We claim:
1. In a process for obtaining a mixture of trifluoroacetyl
polypeptides which do not all have the same amino acid
sequence, where each polypeptide consists essentially of
alanine, glutamic acid, tyrosine and trifluoroacetyl
lysine, wherein the mixture has a de'sired average
molecular weight and wherein during the process a batch
of a mixture of polypeptides, each of which consists
essentially of 'alanine, y-benzyl glutamate, tyrosine and
trifluoroacetyl lysine is deprotected with a solution of
hydrobromic acid in acetic acid, the improvement
comprising use of a solution of hydrobromic. acid in
acetic acid, which solution comprises less than 0.5% of
free bromine.
2. The process of claim 1, wherein the improvement further
comprises use of a solution of hydrobromlic acid' in acetic'
ac'id that comprises less than 1000 ppm of metal ion
impurities.
3. In a process for obtaining a mixture of trifluoroacetyl
polypeptides which do not all have the same amino acid
sequence, where each polypeptide consists essentially of
alanine, glutamic acid, tyrosine and trifluoroacetyl
lysine, wherein the mixture has a desired average
molecular weight and wherein during the process a batch
of a mixture of polypeptides, each of which consists
essentially of alanine, y-benzyl glutamate, tyrosine and
trifluoroacetyl lysine is deprotected with a solution of
hydrobromic acid in acetic acid, the improvement
comprising use of a solution of hydrobromic acid in
acetic acid, which solution comprises less than 1000 ppm
We claim:
36
of metal ion impurities.
4. A 'process of producing a mixture of trifluoroacetyl
polypeptides which do not all have the same amino acid
sequence, where each polypeptide consists essentially of
alanine, glutamic acid, tyrosine and 'trifluoroacetyl
lysine, wherein the mixture has a desired average
rnolecul'ar. weight comprising deprotecting a mixture. of
polypeptides each 'consisting essentially 'of alanine; ybenzyl
glutamate, tyrosine and trifluoroacetyl lysine
with a solution of hydrobrornic acid ifi acetic acid, which
solution comprises less than 0.5% of free bromine and
less than 1000 ppm of metal ion impurities.
5. The process of any one of claims 1-4, wherein 'the
solution of hydrobromic acid in acetic acid comprises
less. than 0.1% of free bromine.
6. The process of 'any one of claims 1-4,. whe,rein the
solution of hydrobromic acid in acetic acid c,omprises
less than 0.05% of free. bromine.
7.. The process of any one of claims 1-4, .'wherein the
solution of hydrobromic acid in acetic acid, comprises
less than 0.01% of free bromine.
8. The process of .any 'one of claims 1-4, wherein the
solution of hydrobromic acid in acetic acid comprises
less than 0.001% of free bromine.
9. The process. of any one of claims. 1-4, wherein the
solution of hydrobromic acid in acetic acid is free of
free bromine.
10. The process of any one of' claims 1-4, wherein the
solution of hydrobromic acid in acetic acid comprises
less than 1000 ppm of metal ion impurities.
11. The process of any one of claims 1-4, wherein the
solution of hydrobromic acid in acetic acid comprises
less than 500 ppm of metal ion impurities.
12. The process of any one of claims 1-4, wherein the
solution of hydrobromic acid in acetic acid comprises
less than 100 ppm of metal ion impurities.
13. The process of any one of claims 1-4, wherein the
solution of hydrobromic acid in acetic acid comprises
less than 10 ppm of metal ion impurities.
14. The process of any one of claims 1-4, where'in the
solution of hydrobromic acid in acetic acid is free of
metal ion impurities.
15. The process of any one of claims 1-14, wherein the
mixtlzre of trifluoroacetyl polypeptides is TFA GA.
16. The process of any 'one of claims 1-15, wherein the
solution is 10-36% hydrobromic acid in acetic acid.
17. The process of claim 16, wherein the solution is 33%
hydrobromic acid in acetic acid.
18. The process of any one of claims 1-16, wherein the
solution is pretreated with a bromine scavenger in order
to remove free bromine.
19. The process of claim 18, wherein the.bromine scavenger is
phenol.
20. The process of .any one of claims 1-19, wherein the
solution is produced.in a non-metallic reactor.
21. The process of any one of claims 1-19, wherein the
solution is prepared in a glass-lined or Teflon lined
reactor.
22. The process of any one of claims 1-21, wherein the color
of the hydrobromic acid in acetic acid solution is less
than 2000 APHA.
23. The process of claim 22, wherein the color of the
hydrobromic acid in acetic acid solution is less than
1000 APHA.
24. The process of claim 23, wherein the color of the
.hydrobromic acid in acetic acid solution is less than 700
APHA.
25. The process of claim 24, wherein the color of the
hydrobromic acid in acetic acid solution is less 'than 500
APHA.
26. A trifluoroacetyl product produced by the process of any
one of claims 1-25.
27. A composition comprising the trifluoroacetyl product
produced by the process of any of claims 1-25, and a
carrier.
28. A mixture of trifluoroacetyl polypeptides which do not
a.11 have the same amino acid sequence, where each
polypeptide consists essentially of alanine, glutamic,
acid, tyrosine and trifluoroacetyl lysine, wherein the
mixture has a desired average molecular weight, no more.
than 0.1% brominated tyrosine and less than 1000 ppm
metal ion impurities.
29. The mixt.ure of claim 28, having an average molecular
weight from 2000 daltons to 40,000 daltons.
30. The mixture of claim 29, having an average molecular
weight from 4000 daltons to 19,000 daltons.
31. The mixture . of claim 29, having an average molecular
weight of 7,000 f2,000 daltons.
32. The mixture of claim 31, having an average molecular
weight of 7,000 daltons.
33. The mixture of claim 30, having an average molecular
weight of 4,700 daltons to 11,000 daltons.
34. The mixture of any one of claims 29-33, wherein the
mixture comprises less than 1000 ppm of metal ion
impurities. . .
35. The mixture of claim 34, wherein the mixture comprises
less than 500 ppm of metal ion impurities.
36. The mixture of claim 35, wherein the mixture comprises
less than 100 ppm of metal ion impurities.
37. The mixture of claim 36, wherein the mixture comprises
less than 10 ppm of metal ion impurities.
38. The mixture of claim 37, wherein the mixture is free of
metal ion impurities.
39. A composition comprising the mixture of any of claims 28-
39 and a carrier.
40. A process for obtaining a pharmaceutical composition
containing a mixture of polypeptides which do not all
have the same amino acid sequence, where each polypeptide
consists essentially of alanine, glutamic acid, tyrosine
and lysine, and wherein the mixture has a desired average
molecular weight, which comprises
a) polymerizing N-carboxyanhydrides of tyrosine,
alanine, y-benzyl glutamate and N-trifluoroacetyl
lysine to form a mixture of protected polypeptides;
b) deprotecting the protected polypeptides with a
solution of hydrobromic acid in acetic acid, which
solution comprises less than 0.5% of free bromine
and less than 1000 ppm of metal ion impurities, to
form a mixture of trifluoroacetyl polypeptides;
c)reacting the a mixture of trifluoroacetyl
polypeptides with aqueous piperidine to form a
solution of aqueous mixture of polypeptides, each of
which consists essentially of alanine, glutamic
acid, tyrosine and lysine; and
d) purifying the mixture of polypeptides.
41. The process of. claim 40, wherein in the mixture the molar
fraction of alanine is 0.427, of glutamic acid is 0.141,
41
of lysine is 0.337 and of tyrosine is 0.093.
A process of producing glatiramer acetate comprising .the
steps of:
a) polymerizing N-carboxyanhydrides of tyrosine,
alanine, y-benzyl glutamate and N-trifluoroacetyl
lysine to form protected glatiramer acetate;
b) deprotecting protected glatiramer acetate with a
solution of hydrobromic acid in acetic acid, the
solution comprises less than 0.5% of free bromine
and less than 1000 ppm of metal ion impurities, to
form trifluoroacetyl glatiramer acetate;
c) reacting trifluoroacetyl glatiramer acetate with
aqueous piperidine to form a solution of. glatiramer
acetate; and
d) purifying the glatiramer acetate.
43. The process of any of claims 40-42, further comprising
subjecting the product of the step d) to ultrafiltration
to remove polypeptide species with molecular weight less
than 5000 daltons.
44. The process of any of claims 40-43, wherein the
hydrobromic acid in acetic acid solution is 10%-36%
hydrobromic acid in acetic acid.
45. The process of claim 44, wherein the hydrobromic acid in
acetic acid solution is 33% hydrobromic acid in acetic
acid.
46. The process of any of claims 40-45, wherein the
hydrobromic acid in acetic acid solution is pretreated
with a bromine scavenger in order to remove free bromine.
47. The process of claim 46, wherein the bromine scavenger is
phenol.
48. The process of any of claims 40-47, wherein the
hydrobromic acid in acetic acid solution is in a
non-metallic reactor.
49. The process of any of claims 40-47, wherein the
hydrobromic acid in acetic acid solution is prepared in a
glass-lined or Teflon lined reactor.
50. The process of any of claims 40-49, wherein the color of
the hydrobromic acid in acetic acid solution is less than
2000 APHA.
51. ~ h ; process of claim 50, wherein the color of the
hydrobromic acid in acetic acid solution is less than
1000 APHA.
52. The process of claim 51, wherein the color o f the
hydrobromic acid in acetic acid solution is less'than. 700
APHA.
53. The process of claim 52, wherein the color of the
hydrobromic acid in acetic acid solution is less than 500
APHA.
54. A method of analyzing the percentage of brominated
tyrosine in a sample of .glatiramer acetate comprising the
steps of:
a) hydrolyzing glatiramer acetate to obtain a
hydrolyzate;
b) eluting the hydrolyzate through a chromatographic
column;
C) measuring the level of bromotyrosine in the
hydrolyzate;
d) preparing sample solutions of the amino acid
components of glatiramer acetate and of
bromotyrosine;
e) eluting the sample solutions through the column of
step b); and
f) calculating the percentage of brominated tyrosine in
the glatiramer acetate.
55. A process for preparing a pharmaceutical composition
containing a mixture of polypeptides which do not all
have the same amino acid sequence, where each polypeptide
consists essentially of glutamic acid, alanine, tyrosine
and lysine, wherein the mixture has a predetermined
percentage of brominated tyrosine acceptable for
inclusion in a pharmaceutical composition, which
comprises
obtaining a batch of a mixture of polypeptides having
nonuniform amino acid sequences, where each polypeptide
consists essentially of glutamic acid, ala~ine, tyrosine
and lysine;
measuring the percentage of brominated tyrosine of the
batch by a process comprising
a) hydrolyzing the batch to obtain a hydrolyzate;
b) eluting the hydrolyzate through a chromatographic
column;
C) measuring the level of bromotyrosine in the
hydrolyzate;
d) preparing sample solutions of the amino acid
components of the batch and of bromotyrosine;
e) eluting the sample solutions through the column of
step b); and
f) calculating the percentage of brominated tyrosine in
the batch; and
including in the pharmaceutical composition a batch only
if its percentage of brominated tyrosine so measured is
less than 0.3%.
56. The process of claim 55, wherein the batch is acceptable
for inclusion in the pharmaceutical composition only if
its percentage of brominated tyrosine so measured is less
than 0.2%.
57. The process of claim 56, wherein the batch is acceptable
for inclusion in the pharmaceutical composit'ion only if
its percentage of brominated tyrosine so measured is less
than 0.1%.
58. The process of any of claims 55-57, wherein the mixture
of polypeptides is GA.