The following specification particularly describes the nature of the invention and the manner in which it is to be performed:

PREPARATION OF POLYPEPTIDES AND SALTS THEREOF
INTRODUCTION
Aspects of the present application relate to processes for preparing polypeptides. Particular aspects of the present application relate processes for preparing glatiramer acetate.
The drug having the adopted name “glatiramer acetate” (formerly known as copolymer-1) is chemically an acetate salt of a randomized mixture of polymers of L-glutamic acid  L-alanine  L-lysine  and L-tyrosine. It has the structural and chemical formulas of Formula (I).
(Glu  Ala  Lys  Tyr)x•xCH3COOH
(C5H9NO4•C3H7NO2•C6H14N2O2•C9H11NO3)x•xC2H4O2
Formula (I)
Glatiramer acetate is the acetate salt of synthetic polypeptides  containing four naturally occurring amino acids: L-glutamic acid  L-alanine  L-tyrosine  and L-lysine with an average molar fraction of 0.141  0.427  0.095  and 0.338  respectively. The average molecular weight of glatiramer acetate is 5 000-9 000 Daltons. Glatiramer acetate is the active ingredient in an injectable pharmaceutical product sold by Teva as COPAXONE®  prescribed for reduction of the frequency of relapses in patients with relapsing-remitting multiple sclerosis (RRMS).
U.S. Patent No. 5 800 808 discloses a process for preparing copolymer-1  by reacting protected copolymer-1 with hydrobromic acid to form trifluoroacetyl copolymer-1  followed by treating the trifluoroacetyl copolymer-1 with aqueous piperidine solution to form copolymer-1 and purifying the resulting copolymer-1.
U.S. Patent No. 7 495 072 discloses a process for preparing glatiramer acetate  by polymerizing N-carboxyanhydrides of tyrosine  alanine  gamma-benzyl glutamate and N-trifluoroacetyllysine to form protected polypeptides  deprotecting the protected polypeptides with pretreated hydrobromic acid in acetic acid solution to form trifluoroacetyl glatiramer acetate  followed by reacting trifluoroacetyl glatiramer acetate with aqueous piperidine to form a solution of glatiramer acetate and purifying the glatiramer acetate.
The preparation of amino acid N-carboxyanhydrides is discussed in U.S. Patent No. 7 294 719 B2  involving reacting amino acids  derivatives thereof such as esters  and their salts with carbonylation reagents such as phosgene.
U.S. Patent No. 7 049 399 discloses a process for the preparation of polypeptide 1  or a pharmaceutically acceptable salt thereof  comprising L-alanine  L-glutamic acid  L-lysine and L-tyrosine randomly arranged in the polypeptide 1 by deprotecting protected copolymer 6 or a salt thereof  to afford polypeptide 1 or a pharmaceutically acceptable salt thereof  in a single step.
U.S. Patent Application Publication No. 2006/0172942 A1 discloses a process for making a mixture of acetate salts of polypeptides  each of which consists of glutamic acid  alanine  tyrosine  and lysine.
U.S. Patent Application Publication No. 2008/0021200 A1 discloses a process for preparing glatiramer acetate by polymerizing a mixture of a N-carboxyanhydride of L-tyrosine  a N-carboxyanhydride of L-alanine  a N-carboxyanhydride of protected L-glutamate  and a N-carboxyanhydride of N-t-butoxycarbonyl-L-lysine  to form a protected glatiramer  followed by treating the protected glatiramer with an acid to form glatiramer.
International Application Publication No. WO 2009/016643 A1 discloses a method of preparation of copolymer-1 fraction (glatiramer acetate  a mixture of polypeptides composed of glutamic acid  alanine  tyrosine  and lysine in a molar ratio of approximately 0.141  0.427  0.095  and 0.338) used in pharmaceuticals.
There remains a need for improved processes for the preparation of polypeptides including glatiramer acetate  having high purity  in a cost-effective and environmentally friendly manner.

SUMMARY
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate  and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid and hypophosphorous acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid and hypophosphorous acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which includes one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid and hypophosphorous acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptide or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides a process for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydrochloric acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydrochloric acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydrochloric acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with a solution of hydrobromic acid in acetic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with a solution of hydrobromic acid in acetic acid;
(c) treating the protected polypeptide obtained in step (b) with a reagent; and
(d) reacting the protected polypeptide obtained in step (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with a solution of hydrobromic acid in acetic acid;
(c) treating the protected glatiramer obtained in step (b) with a reagent; and
(d) reacting the protected glatiramer obtained in step (c) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which includes one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid; and
(c) reacting the protected glatiramer obtained in step (b) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid and hypophosphorous acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid and hypophosphorous acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides process for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid and hypophosphorous acid; and
(c) reacting the protected glatiramer obtained in step (b) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid; and
(c) reacting the protected polypeptide obtained in step (b) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid; and
(c) reacting the protected glatiramer obtained in step (b) with a base to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydrochloric acid; and
(c) reacting the protected polypeptide obtained in step (b) with piperidine to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydrochloric acid; and
(c) reacting the protected polypeptide obtained in step (b) with piperidine to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising hydrochloric acid;
(c) reacting the protected glatiramer obtained in step (b) with piperidine to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising sulphuric acid; and
(c) reacting the protected polypeptide obtained in step (b) with piperidine to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising sulphuric acid; and
(c) reacting the protected polypeptide obtained in step (b) with piperidine to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer;
(b) reacting the protected glatiramer with an acid comprising sulphuric acid; and
(c) reacting the protected glatiramer obtained in step (b) with piperidine to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide; and
(b) reacting the protected polypeptide with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide; and
(b) reacting the protected polypeptide with a solution of hydrooiodic acid and hypophosphorous acid in acetic acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer; and
(b) reacting the protected glatiramer with a mixture of hydroiodic acid and hypophosphorous acid in acetic acid to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid and hypophosphorous acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids selected form L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide; and
(b) reacting the protected polypeptide with an acid comprising hydrooiodic acid and hypophosphorous acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides process for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer; and
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid and hypophosphorous acid to form glatiramer or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide; and
(b) reacting the protected polypeptide with an acid comprising hydroiodic acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing polypeptides or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected selected from L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected polypeptide; and
(b) reacting the protected polypeptide with an acid comprising hydrooiodic acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
In an aspect  the present application provides processes for preparing glatiramer or pharmaceutically acceptable salts thereof  which include one or more of the following steps  individually or in the sequence recited:
(a) polymerizing a mixture of protected amino acids consisting of L-tyrosine  L-alanine  L-glutamate and L-lysine to form a protected glatiramer; and
(b) reacting the protected glatiramer with an acid comprising hydroiodic acid to form glatiramer or a pharmaceutically acceptable salt thereof.

DETAILED DESCRIPTION
In aspects of the present application  processes for preparing polypeptides or pharmaceutically acceptable salts thereof include a step of polymerizing a mixture of protected amino acids to form a protected polypeptide.
Polymerizing a mixture of protected amino acids to form a protected polypeptide may be carried out in the presence of one or more suitable initiators. Suitable initiators that may be used in polymerization reactions include  but are not limited to  alkyl amines  such as  for example  dimethylamine  diethylamine  di-n-propylamine  diisopropylamine  triethylamine  N-ethylmethylamine  di-n-butylamine  diisobutylamine  di-sec-butylamine  di-tert-butylamine  diamylamine  di-n-octylamine  di-(2-ethylhexyl)amine  di-iso-nonylamine  diallylamine  N-methylaniline  diphenylamine  hexylamine  phenethylamine  and the like. Other useful initiators include aziridine  pyrrole  pyrrolidine  imidazole  indole  piperidine  purine  sodium methoxide  potassium t-butoxide  sodium hydride  potassium hydride  2 2 6 6-tetramethylpiperidine  dicyclohexylamine  dicyclohexylundecane (DCU)  lithium diisopropylamide  t-butyllithium  and the like; ion exchange resins including resins bound to ions  such as  for example  sodium  potassium  lithium  calcium  magnesium  substituted or unsubstituted ammonium  and the like. Combinations of any two or more initiators also are useful.
The quantities of initiator that may be used in polymerization reactions may be less than about 5%  less than about 4%  less than about 3%  less than about 2%  less than about 1%  less than about 0.5%  less than about 0.25%  less than about 0.1%  less than about 0.05%  less than about 0.01%  and any other suitable quantities  based on the weight of the mixture of protected amino acids.
Polymerization of protected amino acids to form protected polypeptides may be conducted in a solvent. Suitable solvents that may be used include  but are not limited to: ethers  such as  for example  diethyl ether  diisopropyl ether  tert-butyl methyl ether  dibutyl ether  tetrahydrofuran  dimethylfuran  1 2-dimethoxyethane  2-methoxyethanol  2-ethoxyethanol  anisole  1 4-dioxane  and the like; esters  such as  for example  ethyl formate  methyl acetate  ethyl acetate  propyl acetate  butyl acetate  methyl propanoate  ethyl propanoate  methyl butanoate  ethyl butanoate  and the like; aliphatic or alicyclic hydrocarbons  such as  for example  hexane  heptane  pentane  cyclohexane  methylcyclohexane  and the like; nitromethane; halogenated hydrocarbons  such as  for example  dichloromethane  chloroform  1 1 2-trichloroethane  1 2-dichloroethene  and the like; aromatic hydrocarbons  such as  for example  toluene  xylene  chlorobenzene  tetraline  and the like; nitriles  such as  for example  acetonitrile  propionitrile  and the like; polar aprotic solvents  such as  for example  N N-dimethylformamide  N N-dimethylacetamide  N-methylpyrrolidone  pyridine  dimethylsulfoxide  sulfolane  formamide  acetamide  propanamide  and the like; including any mixtures of two or more thereof.
Suitable temperatures for the polymerization reactions may be less than about 55°C  less than about 45°C  less than about 35°C  less than about 25°C  less than about 15°C  less than about 10°C  or any other suitable temperatures.
Separation of protected polypeptide may be accomplished by combining the reaction mixture with water  which results in precipitation of the protected polypeptide. Suitable temperatures for separation of protected polypeptide may be less than about 50°C  less than about 40°C  less than about 30°C  less than about 20°C  less than about 10°C  or any other suitable temperatures. Suitable times for separation may be less than about 5 hours  less than about 3 hours  less than about 2 hours  less than about 1 hour  less than about 45 minutes  or any longer times. The exact temperatures and times required for complete separation may be readily determined by a person skilled in the art and will also depend on parameters  such as  for example  concentration and temperature of the solution or slurry. Stirring or other alternate methods  such as  for example  shaking  agitation  or the like  that mix the contents may also be employed for separation.
The separated protected polypeptide may be recovered by methods including decantation  centrifugation  gravity filtration  suction filtration  or any other techniques for the recovery of solids.
The recovered protected polypeptide may be optionally dried. Drying may be carried out in a tray dryer  vacuum oven  air oven  fluidized bed dryer  spin flash dryer  flash dryer  and the like. The drying may be carried out at atmospheric pressure or under a reduced pressure  at temperatures less than about 55°C  less than about 45°C  less than about 35°C  less than about 25°C  or any other suitable temperatures. For example  drying times may vary from about 1 to about 10 hours  or longer.
Aspects of the present application include a step of reacting a protected polypeptide with an acid.
Suitable acids that may be used in the reaction of the protected polypeptide with one or more suitable acids  include  but are not limited to  acetic acid  propionic acid  butyric acid  hydrochloric acid  hydrogen bromide  hydrogen fluoride  hydrogen iodide (hydroiodic acid)  methanesulfonic acid  trifluoromethanesulfonic acid  phosphorous acid  trifluoroacetic acid  sulfuric acid  phosphoric acid and hypo phosphoric acid; or the like; or mixtures thereof. The quantities of acid that may be used in the reaction of the protected polypeptide with one or more suitable acids may be less than about 50 times  less than about 40 times  less about 30 times  less than about 20 times  less than about 10 times  less than about 5 times  by volume  the weight of protected polypeptide. Suitably the said acid may have a concentration of not less than about 30% by weight. For varying concentrations of the acid  the quantity of acid to be used in the reaction of the protected polypeptide with one or more suitable acids may be readily calculated by one skilled in the art.
In embodiments  the acid that is employed may cleave protecting groups from the protected polypeptide to form a polypeptide  or form a pharmaceutically acceptable salt thereof.
Suitable temperatures that may be used in the reaction of the protected polypeptide with one or more suitable acids may be less than about 60°C  less than about 50°C  less than about 40°C  less than about 30°C  less than about 25°C  less than about 15°C  less than about 10°C  less than about 5°C  less than about 0°C  or any other suitable temperatures.
Suitable solvents that may be used in the reaction of the protected polypeptide with one or more suitable acids include  but are not limited to: ethers  such as  for example  diethyl ether  diisopropyl ether  tert-butyl methyl ether  dibutyl ether  tetrahydrofuran  1 2-dimethoxyethane  2-methoxyethanol  2-ethoxyethanol  anisole  1 4-dioxane  and the like; esters  such as  for example  ethyl formate  methyl acetate  ethyl acetate  propyl acetate  butyl acetate  methyl propanoate  ethyl propanoate  methyl butanoate  ethyl butanoate  and the like; aliphatic or alicyclic hydrocarbons  such as  for example  hexane  heptane  pentane  cyclohexane  methylcyclohexane  and the like; nitromethane; halogenated hydrocarbons  such as  for example  dichloromethane  chloroform  1 1 2-trichloroethane  1 2-dichloroethene  and the like; aromatic hydrocarbons  such as  for example  toluene  xylene  chlorobenzene  tetralin  and the like; nitriles  such as  for example  acetonitrile  propionitrile  and the like; polar aprotic solvents  such as  for example  N N-dimethylformamide  N N-dimethylacetamide  N-methylpyrrolidone  pyridine  dimethylsulfoxide  sulfolane  formamide  acetamide  propanamide  and the like; acetic acid  and the like; and any mixtures of two or more thereof.
The separation of protected polypeptide or protected glatiramer may be accomplished by methods including removal of solvent  cooling  concentrating the reaction mass  combining with an anti-solvent  and the like. In embodiments  the separation of protected polypeptide may be effected by addition of the reaction mixture to water  which results in precipitation of the protected polypeptide or protected glatiramer. Suitable temperatures for separation may be less than about 50°C  less than about 40°C  less than about 30°C  less than about 20°C  less than about 10°C  or any other suitable temperatures. Suitable times for separation may be less than about 5 hours  less than about 3 hours  less than about 2 hours  less than about 1 hour  less than about 45 minutes. The exact temperatures and times required for complete separation may be readily determined by a person skilled in the art and will also depend on parameters  such as  for example  concentration and temperature of the solution or slurry. Stirring or other alternate methods  such as  for example  shaking  agitation  or the like  that mix the contents may also be employed for separation.
The separated protected polypeptide or protected glatiramer may be recovered by methods including decantation  centrifugation  gravity filtration  suction filtration  or any other techniques for the recovery of solids.
The recovered solid may optionally be dried. Drying may be carried out in a tray dryer  vacuum oven  air oven  fluidized bed dryer  spin flash dryer  flash dryer  or the like. The drying may be carried out at atmospheric pressure or under a reduced pressure  at temperatures less than about 55°C  or less than about 45°C  or less than about 35°C  or less than about 25°C  or any other suitable temperatures. In embodiments  drying times may vary from about 1 to about 10 hours  or longer.
Aspects of the present application include a step of treating the protected polypeptide or protected glatiramer  obtained by reacting the protected polypeptide with an acid  with a reagent  prior to use in the reaction of protected polypeptide or protected glatiramer with a base to form a polypeptide or glatiramer.
Treating the protected polypeptide or protected glatiramer with a reagent may be effected by methods including washing  slurrying  quenching  and the like.
The content of molecular species in acid or acid combinations that may be used in the reaction of the protected polypeptide with an acid  may have an important role in the formation of functionalized polypeptides in polypeptides or glatiramer.
For example  the content of molecular halogen or free halogen species in acids or acid combinations that may be used in the reaction of the protected polypeptide with an acid  may play an important role in the formation of halogenated polypeptides in polypeptides or glatiramer.
It has been discovered that protected polypeptide or protected glatiramer  containing molecular species originating from acids or acid combinations that are used for preparing it  may involve functional transformation with one or more functional groups of polypeptides while reacting the protected polypeptide or protected glatiramer with a base to form a polypeptide or glatiramer  and result in the functionalized polypeptide or functionalized glatiramer being present as a contaminant in the obtained polypeptide or glatiramer.
For example  protected polypeptide or protected glatiramer  containing molecular halogen or free halogen species bound to the surface  may interact with one or more functional groups of polypeptides while reacting the protected polypeptide or protected glatiramer with a base to form a polypeptide or glatiramer  and result in the halogenated polypeptide or halogenated glatiramer being present as a contaminant in the obtained polypeptide or glatiramer.
This can be prevented by treating the protected polypeptide or protected glatiramer  obtained by the reaction of protected polypeptide with an acid  with a reagent prior to use in the reaction of protected polypeptide or protected glatiramer with a base  resulting in the formation of protected polypeptide or protected glatiramer that is substantially free of molecular species.
For instance  treatment of the protected polypeptide or protected glatiramer  obtained by the reaction of protected polypeptide with an acid  with a reagent prior to use in the reaction of protected polypeptide or protected glatiramer with a base  may lead to the formation of protected polypeptide or protected glatiramer substantially free of molecular halogen or free halogen species.
Suitable reagents that may be used for this treatment to reduce the content of molecular impurities include  but are not limited to: alkali or alkaline earth metal thiosulfates  such as  for example  sodium thiosulfate and the like; alkali metal bisulfates  such as  for example  sodium bisulfate and the like; alkali metal metabisulfites  such as  for example  sodium metabisulfite and the like; ascorbic acid; activated carbon fibers; solutions of an organic-soluble ion exchange resin  for example  Amberlite® LA-2 and the like; silver salts; sodium bicarbonate; and the like.
Amberlite LA-2 is liquid highly-branched secondary amines  having molecular weights averaging about 350-400  binding capacity about 2.2-2.3 meq/mL  and the CAS No. 11128-96-4. It is soluble in organic solvents and insoluble in aqueous media.
The protected polypeptide or protected glatiramer  obtained by treating the protected polypeptide or protected glatiramer with a reagent  may be further washed with a solvent. Suitable solvents that may be used include  but are not limited to: water  aliphatic or alicyclic hydrocarbons  such as  for example  hexane  heptane  pentane  cyclohexane  methylcyclohexane  and the like; ethers  such as  for example  diethyl ether  diisopropyl ether  tert-butyl methyl ether  dibutyl ether  tetrahydrofuran  1 2-dimethoxyethane  2-methoxyethanol  2-ethoxyethanol  anisole  1 4-dioxane  and the like; esters  such as  for example  ethyl formate  methyl acetate  ethyl acetate  propyl acetate  butyl acetate  methyl propanoate  ethyl propanoate  methyl butanoate  ethyl butanoate  and the like; and any mixtures of two or more thereof.
In embodiments  protected polypeptides or protected glatiramer  prepared according to a process described in the present application  have peak average molecular weights ranging from about 2000 Daltons to about 40 000 Daltons  or from about 4000 Daltons to about 18 000 Daltons  or about 4000 Daltons to about 13 000 Daltons  or from about 5000 Daltons to about 9000 Daltons  as determined using techniques such as gel permeation chromatography (GPC).
Aspects of the present application include a step of reacting the protected polypeptide or protected glatiramer with a base.
Bases that may be used in the reaction of protected polypeptide or protected glatiramer with a base to form a polypeptide or protected glatiramer  or a pharmaceutically acceptable salt thereof  include  but are not limited to: organic bases  such as  for example  triethylamine  tributylamine  N-methylmorpholine  N N-diisopropylethylamine  N-methylpyrrolidine  piperidine  aqueous piperidine  pyrrolidine pyridine  4-(N N-dimethylamino)pyridine  morpholine  imidazole  2-methylimidazole  4-methylimidazole  methanolic ammonia  and the like; inorganic bases  including: alkali metal hydroxides  such as  for example  lithium hydroxide  sodium hydroxide  potassium hydroxide  and cesium hydroxide; alkaline earth metal hydroxides  such as  for example  barium hydroxide  magnesium hydroxide  calcium hydroxide  and the like; alkali metal carbonates  such as  for example  sodium carbonate  potassium carbonate  lithium carbonate  cesium carbonate  and the like  alkaline earth metal carbonates  such as  for example  magnesium carbonate  calcium carbonate  barium carbonate  and the like; alkali metal bicarbonates  such as  for example  lithium bicarbonate  sodium bicarbonate  potassium bicarbonate  and the like; and mixtures of any two or more thereof.
The reaction of protected polypeptide or protected glatiramer with a base to form a polypeptide or glatiramer or a pharmaceutically acceptable salt thereof may be carried out in a solvent. Suitable solvents that may be used in the reaction of protected polypeptide with a base to form a polypeptide or glatiramer include  but are not limited to: water  ethers  such as  for example  diethyl ether  diisopropyl ether  tert-butyl methyl ether  dibutyl ether  tetrahydrofuran  1 2-dimethoxyethane  2-methoxyethanol  2-ethoxyethanol  anisole  1 4-dioxane  and the like; esters  such as  for example  ethyl formate  methyl acetate  ethyl acetate  propyl acetate  butyl acetate  methyl propanoate  ethyl propanoate  methyl butanoate  ethyl butanoate  and the like; aliphatic or alicyclic hydrocarbons  such as  for example  hexane  heptane  pentane  cyclohexane  methylcyclohexane  and the like; nitromethane; halogenated hydrocarbons  such as  for example  dichloromethane  chloroform  1 1 2-trichloroethane  1 2-dichloroethene  and the like; aromatic hydrocarbons  such as  for example  toluene  xylene  chlorobenzene  tetralin  and the like; nitriles  such as  for example  acetonitrile  propionitrile  and the like; polar aprotic solvents  such as  for example  N N-dimethylformamide  N N-dimethylacetamide  N-methylpyrrolidone  pyridine  dimethylsulfoxide  sulfolane  formamide  acetamide  propanamide  and the like; acetic acid and the like; and any mixtures of two or more thereof.
Suitable temperatures that may be used in the reaction of protected polypeptide with a base to form a polypeptide or glatiramer are less than about 60°C  less than about 55°C  less than about 50°C  less than about 45°C  less than about 40°C  less than about 35°C  less than about 30°C  less than about 25°C  less than about 15°C  less than about 10°C  less than about 5°C  less than about 0°C  or any other suitable temperatures.
In an aspect  the polypeptide or glatiramer prepared according to the processes of the present application may be purified. Purification may be performed using any techniques  including methods that are known in the art. In embodiments  purification of polypeptide or glatiramer may use methods such as dialysis or ultrafiltration.
In embodiments  the polypeptide or glatiramer is subjected to diafiltration against water or buffering agents  such as acetate buffers  phosphate buffers  or citrate buffers  using a molecular weight cutoff membrane (e.g.  1 KDa  2 KDa  3 KDa  and 30 KDa) in step or constant modes of operation. In embodiments  diafiltration solutions can be acidified with a weak acid  such as aqueous acetic acid  and dialyzed against water. For example  concentrations of acetic acid may be less than about 1%  or less than about 0.5%  by volume.
The final dialyzed solution obtained by concentration through an ultrafiltration membrane can be lyophilized to form substantially pure polypeptide or substantially pure glatiramer  or pharmaceutically acceptable salts thereof.
The phrase  “substantially pure ” as used herein above  unless otherwise defined  refers to polypeptide  glatiramer  or pharmaceutically acceptable salts thereof that is substantially free of one or more polypeptide fragments having molecular weights higher than about 40 KDa  or substantially free of polypeptide fragments having molecular weights less than about 2 KDa.
The phrase  “substantially free ” as used herein above  unless otherwise defined  refers to polypeptide  glatiramer  or pharmaceutically acceptable salts thereof containing less than about 5%  less than about 3%  less than about 2%  less than about 1%  or less than about 0.5%  by weight  of one or more of the corresponding species of polypeptides having a molecular weight of about 40 KDa or higher  or polypeptide fragments having a molecular weight of about 2 KDa or less.
In embodiments  polypeptides  or pharmaceutically acceptable salts thereof  prepared according to a process described in the present application may have peak average molecular weights ranging from about 2 000 Daltons to about 40 000 Daltons  or from about 4 000 Daltons to about 18 000 Daltons  or from about 4 000 Daltons to about 13 000 Daltons  or from about 5 000 Daltons to about 9 000 Daltons  as determined using techniques such as gel permeation chromatography (GPC).
In embodiments  glatiramer  or pharmaceutically acceptable salts thereof  prepared according to a process described in the present application may have peak average molecular weights ranging from about 5 000 Daltons to about 9 000 Daltons  as determined using techniques such as gel permeation chromatography (GPC).
In embodiments  polypeptides  or pharmaceutically acceptable salts thereof  prepared according to a process described in the present application have at least 75% of their molar fraction within the molecular weight range of about 2 000 Daltons to about 20 000 Daltons.
In embodiments  glatiramer acetate prepared according to a process described in the present application has at least 75% of its molar fraction within the molecular weight range of about 2 000 Daltons to about 20 000 Daltons.
A gel permeation chromatography method that is useful for determining the molecular weights of polypeptides or pharmaceutically acceptable salts thereof utilizes a Superose™ 12  10×300–310 mm  11 µm  or equivalent column. Additional parameters are as shown in Table 1.
Table 1
Flow rate 0.5 mL/minute (isocratic).
Detector 210 nm.
Column temperature Less than 30°C.
Concentration 4 mg/mL.
Mobile phase Buffer: Na2HPO4 and NaCl solution
Injection volume 50 µL.
Run time 60 minutes for standard and 90 minutes for sample.
The molar fractions of the amino acids in the polypeptide may be determined using methods known in the art. For example  a sample solution is prepared using 2 mg of the polypeptide and hydrolyzed using 6N HCl  under a N2 atmosphere at about 110-130°C. Amino acid standard solutions containing each of glutamic acid  alanine  tyrosine  and lysine hydrochloride are prepared. The standard and sample solutions are derivatized with fluorenylmethyloxycarbonyl (Fmoc) reagent. The standard and sample solutions can be analyzed using a C18 or equivalent column  in an instrument equipped with a UV detector. Additional parameters are as shown in Table 2.
Table 2
Flow rate 1.0 mL/minute.
Detector 265 nm.
Column temperature 30°C.
Mobile phases Mobile phase A: Mix a pH 3.5 buffer (sodium acetate trihydrate and acetic acid) and acetonitrile in the volume ratio 90:10.
Mobile phase B: Mix a pH 3.5 buffer (sodium acetate trihydrate and acetic acid) and acetonitrile in the volume ratio 10:90.
Injection volume 50 µL.
Elution Gradient.
The molar fractions of the amino acids in the polypeptide sample are determined based on peak areas.
Protected polypeptides obtained according to a process of the present application may be substantially free of benzyl chloride.
Protected glatiramer obtained according to a process of the present application may be substantially free of benzyl chloride.
Trifluoroacetyl glatiramer obtained according to a process of the present application may be substantially free of benzyl chloride.
Polypeptides obtained according to a process of the present application may be substantially free of benzyl chloride.
Glatiramer acetate obtained according to a process of the present application may be substantially free of benzyl chloride.
The phrase  “substantially free ” in this context  means that the compound contains less than about 3%  less than about 2%  less than about 1%  less than about 0.5%  less than about 0.3%  less than about 0.1%  less than about 0.05%  or less than about 0.01%  by weight of benzyl chloride  as determined using high performance liquid chromatography (HPLC).
A HPLC method for the analysis of the benzyl chloride content utilizes a C18 or equivalent column. Additional parameters are as shown in Table 3.
Table 3
Flow rate 1.0 mL/minute.
Column temperature Ambient.
Mobile phases Mobile phase A: 0.1% OPA in water and acetonitrile (90:10 by volume).
Mobile phase B: 0.1% OPA in water and acetonitrile (10:90 by volume).
OPA: Orthophosphoric acid.
Injection volume 10 µL.
Elution Gradient.
Polypeptides or pharmaceutically acceptable salts thereof prepared according to a process of the present application may be substantially free of one or more of its corresponding functionalized polypeptides  e.g.  the polypeptides  wherein the one or more functional groups are mono-  di- or poly-functionalized  as determined by HPLC.
For example  polypeptides or pharmaceutically acceptable salts thereof prepared according to a process of the present application may be substantially free of one or more of its corresponding halogenated polypeptides  e.g.  polypeptides wherein the tyrosine moiety is mono-  di-  or poly-halogenated. Examples of halogens are chlorine  bromine  and iodine.
Glatiramer acetate obtained according to a process of the present application may be substantially free of one or more of its corresponding halogenated polypeptides  e.g.  polypeptides wherein the tyrosine moiety is mono-  di-  or poly-halogenated. Examples of halogens are chlorine  bromine  and iodine.
The phrase  “substantially free” of functionalized polypeptides  as used herein  means less than about 2%  less than about 1%  less than about 0.5%  less than about 0.3%  less than about 0.1%  less than about 0.05%  less than about 0.01%  less than about 0.005%  or less than about 0.001%  by weight  as determined using techniques such as HPLC. Functionalized polypeptides  as used herein  unless otherwise defined refer to the polypeptides  wherein the one or more functional groups are mono-  di-  or poly-functionalized.
The phrase  “substantially free” of halogenated polypeptides  as used herein  means less than about 2%  less than about 1%  less than about 0.5%  less than about 0.3%  less than about 0.1%  less than about 0.05%  less than about 0.01%  less than about 0.005%  or less than about 0.001%  by weight  as determined using HPLC. Halogenated polypeptides  as used herein  unless otherwise defined refer to the polypeptides  wherein the tyrosine moiety is mono-  di-  or poly-halogenated. Examples of halogens are chlorine  bromine  and iodine.
All percentages and ratios used herein are by weight of the total composition and all measurements made are at 25°C and atmospheric pressure  unless otherwise designated. All temperatures are in degrees Celsius unless specified otherwise. As used herein  "comprising" means the elements recited  or their equivalent in structure or function  plus any other element or elements that are not recited. The terms “containing ” "having " and "including" are also to be construed as open ended unless the context suggests otherwise. As used herein  "consisting essentially of" means that the application may include ingredients in addition to those recited in the claim  but only if the additional ingredients do not materially alter the basic and novel characteristics of the claimed application. All ranges recited herein include the endpoints  including those that recite a range "between" two values. The terms "about " "generally " "substantially " and the like are to be construed as modifying a term or value such that it is not an absolute. Such terms will be defined by the circumstances and the terms that they modify as those terms are understood by those of skill in the art. This includes  at very least  the degree of expected experimental error  technique error and instrument error for a given technique used to measure a value.
The content of mono-  di-  and poly-halogenated tyrosine in polypeptides may be determined using methods known in the art. For example  a sample solution is hydrolyzed using acid and/or base. Mono-  di- or poly-halogenated tyrosine standard solutions are prepared by using diluent 1 in Table 4. The standard and sample solutions are analyzed using a LiChroCART® RP18e  or equivalent  column  in an instrument equipped with a UV detector. Additional parameters are as shown in Table 4.
Table 4
Flow rate 1.0 mL/minute.
Column temperature 30°C.
Wavelength 220 nm.
Diluent Diluent 1: water.
Diluent 2: 0.1M HCl in water.
Buffer 1.0 mL of orthophosphoric acid in 1L of Milli Q water or equivalent.
Mobile phase Mobile phase A: 100% Buffer.
Mobile phase B: Mix buffer and acetonitrile in the volume ratio 10:90.
Injection volume 10 µL.
Run time 60 minutes.
The content of mono-  di-  and poly-halogenated tyrosine in a polypeptide sample is determined based on peak areas.
Pharmaceutical compositions comprising a polypeptide  such as glatiramer  of the present application may be formulated using methods known in the art. In embodiments  a liquid composition is lyophilized and subsequently can be dissolved to form an aqueous solution that is suitable for injection. Alternatively  glatiramer acetate may be formulated in any of the forms known in the art for preparing oral  nasal  buccal  and rectal formulations of peptide drugs.
Typically  glatiramer acetate is administered daily to patients suffering from multiple sclerosis  at a dosage of 20 mg.

DEFINITIONS
The following definitions are used in connection with the present application unless the context indicates otherwise.
The term "polypeptide" as used herein refers to compounds formed from at least two amino acids.
The term "amino acid" as used herein refers to an organic compound comprising at least one amino group and at least one acidic group. The amino acid may be a naturally occurring amino acid or be of synthetic origin  or an amino acid derivative or amino acid analog.
The term “protected amino acids” as used herein  refers to amino acids where functional groups in amino acids are derivatized with any suitable protecting group that can prevent the functional groups from entering into undesired reactions  and can subsequently be readily removed.
The term “protecting group” as used herein  refers to a group attached to functional group of amino acids or peptide or polypeptide that can be cleaved from a peptide or polypeptide under a particular set of conditions. Suitable protecting groups known in the art such as those described in J.F.W. McOmie  “Protective Groups in Organic Chemistry”  Plenum Press  London and New York 1973  in Th. W. Greene  “Protective Groups in Organic Synthesis”  Wiley  New York 1981  in “The peptides”  volume 3 (E. Gross and J. Meienhofer  eds.)  Academic Press  London and New York 1981  in “Methoden der organischen Chemie”  Houben-Weyl  4th edition  Volume 15/I  Georg Thieme Verlag  Stuttgart 1974  in H.-D.Jakubke and H.Jescheit  “Aminosauren  Peptide  Proteine’ (“Amino acids  peptides  proteins”)  E. Gross & J. Meienhofer  The Peptides: Analysis  Structure  Biology  Vol. 3: Protection of Functional Groups in Peptide Synthesis (Academic Press  N.Y.  1981); Kricheldorf  H. R. a-Amino Acid N-Carboxy-Anhydride and Related Heterocycles  Springer-Verlag: Berlin  1987; Blacklock  T. J.; Hirschmann  R.; Veber  D. F. The Peptides; Academic Press: New York  1987; Vol. 9  p 39.
Certain specific aspects and embodiments will be further explained by the following examples  being provided only for purposes of illustration and not to be construed as limiting the scope of the application in any manner.

EXAMPLE 1
Preparation of glatiramer acetate.
A N-carboxyanyhydride of L-alanine (1.37 g)  a N-carboxyanhydride of L-tyrosine (0.49 g)  a N-carboxyanhydride of N-trifluoroacetyl L-lysine  (2.28 g) and a N-carboxyanhydride of ?-benzyl L-glutamate (1.01) are charged into a round bottom flask under a nitrogen atmosphere. 1 4-Dioxane (96 mL) is added at 25-30°C and the mixture is stirred for 15 minutes. Diethylamine (36 µL) is added at 25-30°C and the mixture is stirred at the same temperature for 24 hours. The mixture is poured slowly into water (260 mL) and the mass is stirred at 25-30°C for 30 minutes. The solid is collected by filtration  washed with water (20 mL) and dried under reduced pressure at 28-32°C  to afford 3.86 g of a protected glatiramer.
The protected glatiramer (3.86 g) is charged into a round bottom flask  33% HBr in acetic acid (38.6 mL) is added  and the mixture is stirred at 25-30°C for 17 hours. The mixture is slowly added to water (77.2 mL) at 25-30°C and the mass is stirred for 10 minutes. The solid is collected by filtration  washed with a mixture of water (200 mL) and hexane (50 mL)  and dried at 25-30°C under reduced pressure to afford 2.968 g of trifluoroacetyl glatiramer.
Trifluoroacetyl glatiramer (2.96 g)  piperidine (15.9 g)  and water (143.6 mL) are charged into a round bottom flask. The mixture is stirred at 25-30°C for 24 hours and then subjected to diafiltration using a 1KDa molecular weight cutoff membrane  against ammonium acetate buffer (pH 5.5±0.3)  in a stepwise mode of operation  until pH of the permeate reaches 6-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.3-4.5 and diafiltered against water to remove excess acetic acid until pH of the retentate reaches 5-5.5. The obtained solution is lyophilized to afford 900 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 8403 Daltons; average molar fraction of alanine  glutamic acid  tyrosine and lysine: 0.441  0.155  0.080  and 0.323  respectively.

EXAMPLE 2
Preparation of glatiramer acetate.
A N-carboxyanhydride of L-alanine (5.48 g)  a N-carboxyanhydride of L-tyrosine (1.96 g)  a N-carboxyanhydride of N-trifluoroacetyl L-lysine (9.12 g) and a N-carboxyanhydride of ?-benzyl L-glutamate (4.04 g) are charged into a round bottom flask under a nitrogen atmosphere. 1 4-Dioxane (384 mL) is added at 25-30°C and the mixture is stirred for 15 minutes. Diethylamine (144 µL) is added at 25-30°C and the mixture is stirred at the same temperature for 24 hours under a nitrogen atmosphere. The mixture is poured slowly into water (1000 mL) and the mass is stirred at 25-30°C for 30 minutes. The solid is collected by filtration  washed with water (80 mL) and dried under reduced pressure at 28-32°C to afford 15.10 g of a protected glatiramer.
The protected glatiramer (1.0 g) is charged into a round bottom flask. A mixture of concentrated HCl (12 mL) and glacial acetic acid (38 mL) is added and the mixture is stirred at 15-20°C for 18 hours. The mixture is slowly added to water (250 mL) at 25-30°C and the mass is stirred for 10 minutes The solid is collected by filtration  washed with a mixture of water (100 mL) and hexane (50 mL) and dried at 25-30°C under reduced pressure to afford 0.550 g of trifluoroacetyl glatiramer.
Trifluoroacetyl glatiramer (0.40 g)  piperidine (2.2 g)  and water (19.8 mL) are charged into a round bottom flask. The mixture is stirred at 25-30°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a stepwise mode of operation  until pH of the permeate reaches 6-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.3-4.5 and diafiltered against water to remove excess acetic acid  until pH of the retentate reaches 5-5.5. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 137 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 7662 Daltons.

EXAMPLE 3
Preparation of glatiramer acetate.
The protected glatiramer from Example 2 (1.0 g) and tetrahydrofuran (200 mL) are charged into a round bottom flask and stirred for 5 minutes at 25-30°C. The mixture is cooled to 0-5°C and concentrated H2SO4 (10 mL) is added at the same temperature. The mixture is stirred at 0-5°C for 2 hours  then stirred at 25-30°C for 20 hours. Solvent is distilled from the mixture at 30°C. Water (100 mL) is added to the resulting mass at 25-30°C and stirred for 10 minutes. The solid is collected by filtration  washed with water (100 mL) and dried at 25-30°C under reduced pressure to afford 0.510 g of trifluoroacetyl glatiramer.
Trifluoroacetyl glatiramer (0.40 g)  piperidine (2.2 g)  and water (18 mL) are charged into a round bottom flask. The mixture is stirred at 25-30°C for 24 hours. The mixture is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a stepwise mode of operation  until pH of the permeate reaches 6-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.3-4.5 and diafiltered against water to remove excess acetic acid until pH of the retentate reaches 5-5.5. The obtained solution is lyophilized to afford 100 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 5371 Daltons.

EXAMPLE 4
Preparation of glatiramer acetate.
A N-carboxyanhydride of L-alanine (5.48 g)  a N-carboxyanhydride of L-tyrosine (1.96 g)  a N-carboxyanhydride of N-trifluoroacetyl-L-lysine (9.12 g) and a N-carboxyanhydride of ?-benzyl-L-glutamate (4.04 g) are charged into a round bottom flask under a nitrogen atmosphere. 1 4-Dioxane (384 mL) is added at 30°C and the mixture is stirred for 15 minutes. Diethylamine (144 µL) is added at 25-30°C and the mixture is stirred at the same temperature for 24 hours under a nitrogen atmosphere. The mixture is poured slowly into water (1000 mL) and the mass is stirred at 25-30°C for 10 minutes. The solid is collected by filtration  washed with water (20 mL) and dried under reduced pressure at 25-35°C to afford 15.0 g of a protected glatiramer.
The protected glatiramer (0.5 g) is charged into a round bottom flask. A mixture of 57% of HI and H3PO2 (5 mL) is added and the mixture is stirred at 30°C for 17 hours. The mixture is slowly added to water (20 mL) at 30°C and the mass is stirred for 15 minutes. The solid is collected by filtration  washed with a mixture of water (50 mL) and hexane (20 mL) and dried at 25-30°C under reduced pressure to afford 0.165 g of trifluoroacetyl glatiramer.
Benzyl chloride content by HPLC: 0.3%.
Trifluoroacetyl glatiramer (110 mg)  piperidine (0.6 mL) and water (5.5 mL) are charged into a round bottom flask. The mixture is stirred at 30°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a stepwise mode of operation  until pH of the permeate reaches 6-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.3-4.5 and is diafiltered against water to remove excess acetic acid  until pH of the retentate reaches 5-5.5. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 68 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 4545 Daltons; benzyl chloride content by HPLC: 0.06%.

EXAMPLE 5
Preparation of glatiramer acetate.
The protected glatiramer from Example 4(A) (1.0 g) is charged into a round bottom flask. A mixture of 57% of HI and H3PO2 (5 mL) in acetic acid (15 mL) is added and the mixture is stirred at 30°C for 16 hours. The mixture is slowly added to water (60 mL) at 30°C and the mass is stirred for 15 minutes. The solid is collected by filtration  washed with a mixture of water (100 mL) and hexane (40 mL)  and dried at 25-30°C under reduced pressure to afford 740 mg of trifluoroacetyl glatiramer.
Benzyl chloride content by HPLC: 0.25%.
Trifluoroacetyl glatiramer (500 mg)  piperidine (2.75 mL) and water (25 mL) are charged into a round bottom flask. The mixture is stirred at 30°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a stepwise mode of operation  until pH of the permeate reaches 6-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.3-4.5 and diafiltered against water to remove excess acetic acid  until pH of the retentate reaches 5-5.5. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 300 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 6938 Daltons; benzyl chloride content by HPLC: 0.05%.

EXAMPLE 6
Preparation of protected glatiramer.
A N-carboxyanhydride of L-alanine (13.56 g)  a N-carboxyanhydride of L-tyrosine (4.99 g)  a N-carboxyanhydride of N-trifluoroacetyl-L-lysine (22.8 g) and a N-carboxyanhydride of ?-benzyl-L-glutamate (9.89 g) are charged into a round bottom flask under a nitrogen atmosphere. 1 4-Dioxane (996 mL) is added at 25-30°C and the mixture is stirred for 15 minutes. Diethylamine (360 µL) is added at 25-30°C and the mixture is stirred at the same temperature for 24 hours. The mixture is poured slowly into water (2.6 L) and the mass is stirred at 25-30°C for 30 minutes. The solid is collected by filtration  washed with water (1.5 L) and dried under reduced pressure at 25-35°C to afford 34.5 g of a protected glatiramer.

EXAMPLE 7
Preparation of glatiramer acetate.
The protected glatiramer from Example-6 (5.0 g) is charged into a round bottom flask at 33°C with protection from light. A pre-mixed solution of 57% of HI and H3PO2 (25 mL) in acetic acid (75 mL) is added and the mixture is stirred at 30-35°C for 17 hours with protection from light. The mixture is slowly added to water (500 mL) at 30-35°C and the mass is stirred for 15 minutes. The solid is filtered and washed with water (50 mL) to give brown-color compound. The wet compound is washed with 10% sodium thiosulfate solution (Na2S2O3•5H2O) (5×100 mL) to give white compound  washed with water (2 L) and finally washed with hexane (250 mL) and dried at 25-30°C under reduced pressure to afford 3.5 g of trifluoroacetyl glatiramer.
Monoiodotyrosine content by HPLC: not detected; diiodotyrosine content by HPLC: not detected.
Trifluoroacetyl glatiramer (3.0 g)  piperidine (16.5 mL)  and water (150 mL) are charged into a round bottom flask. The mixture is stirred at 25-35°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a stepwise mode of operation  until the pH of the permeate reaches 5.5-6.5. The retentate solution is circulated with 0.3% acetic acid until pH reaches 4.5-4.6 and is diafiltered against water to remove excess acetic acid  until the pH of the retentate reaches 4.8-4.9. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 1750 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 7988 Daltons; monoiodotyrosine content by HPLC: not detected; diiodotyrosine content by HPLC: not detected.

EXAMPLE 8
Preparation of glatiramer acetate.
The protected glatiramer from Example 6 (10.0 g) is charged into a round bottom flask at 33°C with protection from light. A pre-mixed solution of 57% of HI and H3PO2 (50 mL) in acetic acid (150 mL) is added and the mixture is stirred at 30-35°C for 17 hours with protection from light. This reaction mixture is divided in to three equal parts  each of which is further treated separately.
Part 1 of the reaction mixture (180 mL) is charged into water (900 mL) and stirred for 5 minutes. The solid is filtered and washed with water (100 mL) to give a brown-color solid. The wet solid is washed with 10% sodium thiosulfate solution (Na2S2O3•5H20) (5×200 mL) to give a white solid  then washed with water (4 L)  washed with hexane (500 mL)  and dried at 25-30°C under reduced pressure to afford 6.9 g of trifluoroacetyl glatiramer.
Monoiodotyrosine content by HPLC: not detected; diiodotyrosine content by HPLC: not detected.
Part 2 of the reaction mixture (10 mL) is quenched in 5% ascorbic acid in water (50 mL) and stirred for 5 minutes. The obtained solid is filtered  washed with water (30 mL)  washed with hexane (20 mL)  and dried at 25-30°C under reduced pressure to afford 0.15 g of trifluoroacetyl glatiramer.
Monoiodotyrosine content by HPLC: 0.016%; diiodotyrosine content by HPLC: not detected.
Part 3 of the reaction mixture (10 mL) is quenched in water (50 mL) and stirred for 5 minutes. The obtained solid is filtered and washed twice with 5% ascorbic acid in water (50 mL). The resultant solid is washed with water (20 mL)  hexane (20 mL) and dried at 25-30°C under reduced pressure to afford 0.15 g of trifluoroacetyl glatiramer.
Trifluoroacetyl glatiramer of Part 1 (5.0 g)  piperidine (27.5 mL) and water (250 mL) are charged into a round bottom flask. The mixture is stirred at 25-35°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5±0.3) in a step-wise mode of operation  until the pH of the permeate reaches 5.5-6.5. The retentate solution is circulated with 0.3% acetic acid until the pH reaches 4.5-4.6 and is diafiltered against water to remove excess acetic acid  until the pH of the retentate reaches 4.8-4.9. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 3400 mg of glatiramer acetate.
Peak average molecular weight of glatiramer acetate by GPC: 8737 Daltons; monoiodotyrosine content by HPLC: not detected; diiodotyrosine content by HPLC: not detected.

EXAMPLE 9
Preparation of trifluoroacetyl glatiramer.
Protected glatiramer from Example 6 (2.0 g) is charged into a round bottom flask  33% HBr in acetic acid (20 mL) is added  and the mixture is stirred at 25-30°C for 17 hours. The mixture is slowly added to water (40 mL) at 25-30°C and the mass is stirred for 10 minutes. The solid is filtered  washed with water (100 mL) to give brown-color solid. The wet solid is washed with 10% sodium thiosulfate solution (Na2S2O3•5H2O) (200 mL) to give white solid  washed with water (200 mL)  washed with hexane (100 mL)  and dried at 25-30°C under reduced pressure to afford 1.35 g of trifluoroacetyl glatiramer.
Monoiodotyrosine content by HPLC: 0.36%; Diiodotyrosine content by HPLC: not detected.

EXAMPLE 10
Preparation of glatiramer acetate.
The protected glatiramer from Example 6 (1.0 g) is charged into a round bottom flask at 30-35°C with protection from light. A pre-mixed solution of 57% of HI and H3PO2 (5.0 mL) in acetic acid (15 mL) is added. The mixture is heated to 40°C and stirred for 4 hours with protection from light. The reaction is quenched with 5% sodium thiosulfate solution (100 mL) and stirred for 10-15 minutes. The solid is filtered  washed with a solution of sodium thiosulfate (50 mL)  washed with water (600 mL)  washed with hexane (50 mL)  and dried at 25-30°C under reduced pressure  to afford 0.6 g of trifluoroacetyl glatiramer.
Monoiodotyrosine content by HPLC: not detected; Diiodotyrosine content by HPLC: not detected.
Trifluoroacetyl glatiramer (500 mg)  piperidine (2.8 mL)  and water (25 mL) are charged into a round bottom flask. The mixture is stirred at 25-35°C for 24 hours  then is subjected to diafiltration using a 1KDa molecular weight cutoff membrane against ammonium acetate buffer (pH 5.5 ± 0.3) in a stepwise mode of operation  until the pH of the permeate reaches 5.5-6.5. The retentate solution is circulated with 0.3% acetic acid until the pH reaches 4.5-4.6 and is diafiltered against water to remove excess acetic acid  until pH of the retentate reaches 4.8-4.9. The diafiltered sample is then concentrated through a 3 KDa molecular weight cutoff membrane and the concentrated solution is lyophilized to afford 1750 mg of glatiramer acetate.
Monoiodotyrosine content by HPLC: not detected; diiodotyrosine content by HPLC: not detected.

WE CLAIM:
1. A process for preparing a polypeptide or a pharmaceutically acceptable salt thereof  comprising:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide;
(b) reacting the protected polypeptide with an acid;
(c) optionally  treating the protected polypeptide obtained in step (b) with a reagent to reduce the content of molecular impurities; and
(d) reacting the protected polypeptide obtained in steps (b) or (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
2. The process of claim 1  wherein the amino acids are L-tyrosine  L-alanine  L-glutamate  and L-lysine.
3. The process of claim 1  wherein the polypeptide is glatiramer.
4. The process of any of claims 1-3  wherein protected amino acids are amino acid N-carboxyanhydrides.
5. The process of any of claims 1-3  wherein an acid comprises one or more of acetic acid  propionic acid  butyric acid  hydrochloric acid  hydrogen bromide  hydrogen fluoride  hydrogen iodide  methanesulfonic acid  trifluoromethanesulfonic acid  phosphorous acid  trifluoroacetic acid  sulfuric acid  phosphoric acid  and hypophosphoric acid.
6. The process of any of claims 1-3  wherein an acid comprises two or more of acetic acid  propionic acid  butyric acid  hydrogen chloride  hydrogen bromide  hydrogen fluoride  hydrogen iodide  methanesulfonic acid  trifluoromethanesulfonic acid  phosphorous acid  trifluoroacetic acid  sulfuric acid  phosphoric acid  and hypophosphoric acid.
7. The process of any of claims 1-3  wherein an acid comprises two or more of acetic acid  hydrogen chloride  hydrogen bromide  hydrogen iodide  and hypophosphoric acid.
8. The process of any of claims 1-3  wherein an acid comprises at least one of hydrogen chloride  hydrogen bromide  hydrogen iodide  sulfuric acid  and hypophosphoric acid.
9. The process of any of claims 1-3  wherein a reagent comprises one or more of sodium thiosulfate  sodium bisulfate  sodium metabisulfite  ascorbic acid  activated carbon fiber  an ion exchange resin  a silver salt  and sodium bicarbonate.
10. The process of any of claims 1-3  wherein a base is an organic base.
11. The process of any of claims 1-3  wherein a base is an inorganic base.
12. The process of any of claims 1-3  wherein a base comprises piperidine.
13. A process for preparing glatiramer or a pharmaceutically acceptable salt thereof  comprising:
(a) polymerizing a mixture of the protected amino acids L-tyrosine  L-alanine  L-glutamate  and L-lysine to form protected glatiramer;
(b) reacting the protected glatiramer with an acid;
(c) optionally  treating the protected polypeptide obtained in step (b) with a reagent to reduce the content of molecular impurities; and
(d) reacting the protected polypeptide obtained in steps (b) or (c) with a base to form a polypeptide or a pharmaceutically acceptable salt thereof.
14. The process of claim 13  wherein the protected amino acids are amino acid N-carboxyanhydrides.
15. The process of claim 13  wherein an acid comprises one or more of acetic acid  propionic acid  butyric acid  hydrochloric acid  hydrogen bromide  hydrogen fluoride  hydrogen iodide  methanesulfonic acid  trifluoromethanesulfonic acid  phosphorous acid  trifluoroacetic acid  sulfuric acid  phosphoric acid  and hypophosphoric acid.
16. The process of claim 13  wherein an acid comprises two or more of acetic acid  propionic acid  butyric acid  hydrogen chloride  hydrogen bromide  hydrogen fluoride  hydrogen iodide  methanesulfonic acid  trifluoromethanesulfonic acid  phosphorous acid  trifluoroacetic acid  sulfuric acid  phosphoric acid  and hypophosphoric acid.
17. The process of claim 13  wherein an acid comprises two or more of acetic acid  hydrogen chloride  hydrogen bromide  hydrogen iodide  and hypophosphoric acid.
18. The process of claim 13  wherein an acid comprises at least one of hydrogen chloride  hydrogen bromide  hydrogen iodide  sulfuric acid  and hypophosphoric acid.
19. The process of claim 13  wherein a reagent comprises one or more of sodium thiosulfate  sodium bisulfate  sodium metabisulfite  ascorbic acid  activated carbon fiber  an ion exchange resin  a silver salt  and sodium bicarbonate.
20. The process of claim 13  wherein a base is an organic base.
21. The process of claim 13  wherein a base is an inorganic base.
22. The process of claim 13  wherein a base comprises piperidine.
23. A process for preparing a polypeptide or a pharmaceutically acceptable salt thereof  comprising:
(a) polymerizing a mixture of protected amino acids to form a protected polypeptide; and
(b) reacting the protected polypeptide with an acid to form a polypeptide or a pharmaceutically acceptable salt thereof.
24. The process of any of claim 23  wherein protected amino acids are amino acid N-carboxyanhydrides.
25. The process of claim 23  wherein the amino acids are L-tyrosine  L-alanine  L-glutamate  and L-lysine.
26. The process of claim 23  wherein the polypeptide is glatiramer.
27. The process of claim 23  wherein an acid comprises one or more of acetic acid  hydrogen iodide  phosphorous acid  phosphoric acid  and hypophosphoric acid.
28. The process of claim 23  wherein an acid comprises two or more of acetic acid  phosphorous acid  phosphoric acid  and hypophosphoric acid.
29. The process of claim 23  wherein an acid comprises two or more of acetic acid  hydrogen iodide  and hypophosphoric acid.
30. The process of claim 23  wherein an acid comprises at least one of hydrogen iodide.
31. The process of claims 13-30  further comprising purifying a polypeptide or a pharmaceutically acceptable salt thereof.
32. The process of claims 13-30  further comprising purifying glatiramer or a pharmaceutically acceptable salt thereof.