What it is
Glatiramer acetate is a peptide mixture, not a peptide. The Copaxone label describes it as "the acetate salts of synthetic polypeptides" made from four amino acids — glutamic acid, alanine, tyrosine and lysine — joined at random in fixed average proportions: alanine 42.7%, lysine 33.8%, glutamic acid 14.1% and tyrosine 9.5% (molar fractions, label). There is no sequence to print. Chains vary in length and order; the average molecular weight is 5,000–9,000 daltons. At this mix's average residue mass of about 107 daltons, that is roughly 47 to 84 residues per chain (our arithmetic, ignoring the acetate) — straddling the 40-residue line that US regulation uses to separate a peptide from a protein.
Because the mixture has no single structure, the label defines its activity by a test: glatiramer's potency is "determined by its ability to block the induction of experimental autoimmune encephalomyelitis (EAE) in mice", the standard animal model of MS.
How it is thought to work
The label is plain about the gap: the mechanism "is not fully understood." The leading hypothesis comes from animal and laboratory studies, in which glatiramer induces glatiramer-specific regulatory T cells outside the brain; these are thought to travel to the central nervous system and quieten the inflammation that strips myelin. That is a model built in mice, not a mechanism measured in people. The label adds that because glatiramer can modify immune responses, "concerns exist about its potential to alter naturally-occurring immune responses" — and that there is no evidence it does, though this "has not been systematically evaluated."
What the label's trials show
| Trial (label) | Who, how many | Result vs placebo |
|---|---|---|
| Study 1 (single centre) | 50 with relapsing-remitting MS, 20 mg daily, 2 years | Relapses 0.6 vs 2.4 per 2 years (p = 0.005); relapse-free 56% vs 28% |
| Study 2 (11 US centres) | 251, 20 mg daily, 2 years | Relapses 1.19 vs 1.68 per 2 years (p = 0.055); relapse-free 34% vs 27% (p = 0.25) |
| Study 3 | 481 after a first demyelinating event, 20 mg daily, up to 3 years | Second attack HR 0.55; relapse within 36 months 24.7% vs 42.9% |
| Study 4 (MRI) | 239 with active lesions, 20 mg daily, 9 months | Median cumulative enhancing lesions 11 vs 17 |
| Study 5 | 1,404, 40 mg three times weekly, 12 months | Confirmed relapses 0.331 vs 0.505 (−34%); new/enlarging T2 lesions −35%; enhancing lesions −45% |
Two details the summary sentences tend to drop: Study 2, the larger of the two original relapse trials, missed conventional significance on its primary outcome (p = 0.055), and the label bases effectiveness on the two trials together. And none of the five measured long-term disability as a primary outcome — Study 2's disability score difference was −0.05 vs +0.21 points. The label reports results against placebo only; this entry does not compare glatiramer with any other MS treatment.
Safety
The label's boxed warning is anaphylaxis: life-threatening and fatal reactions have been reported, at any point from the first dose to years later, mostly within an hour of an injection. Separately, an immediate post-injection reaction — flushing, chest pain, palpitations, breathlessness, throat tightness — affected about 16% on 20 mg daily vs 4% on placebo, and about 2% on 40 mg three times weekly vs none. Transient chest pain occurred in about 13% vs 6%. Other listed warnings: lipoatrophy and skin necrosis at injection sites, liver injury, and dosing errors with autoinjectors not designed for the product. In the 20 mg trials, vasodilatation was reported in 20% vs 5% and rash in 19% vs 11% (label).
Where it stands
- Approved in the US since 1996-12-20 (Copaxone, NDA 020622, Teva), as 20 mg/mL and 40 mg/mL prefilled syringes.
- Generics: nine approved generic applications in Drugs@FDA from six companies — Sandoz (Glatopa, first approved 2015-04-16), Mylan, Synthon, Chemi, ScinoPharm and Hybio — all listed as prescription (openFDA, 2026-10-15; our count).
- Research record: PubMed indexes 2,891 records, 126 tagged as randomised trials; ClinicalTrials.gov lists 127 studies (2026-10-15).
Related reading
For the bond that links every unit in glatiramer's chains, see the peptide bond; for where a chain stops being a peptide and becomes a protein, peptide vs protein. The four building blocks sit in the amino acid chart. Another approved drug that is defined by a mixture rather than one molecule is polymyxin B.