Glatiramer Acetate: The Random Peptide Copolymer Used in Multiple Sclerosis

Immunomodulating peptides

Glatiramer acetate is a mixture of short synthetic polypeptides built from only four amino acids, and it is one of the few approved drugs specified by composition rather than by a single sequence. It grew out of a Weizmann Institute attempt to build a disease-causing myelin mimic that failed in an unexpected way, and it is approved in the United States for relapsing forms of multiple sclerosis (MS).

What is glatiramer acetate?

According to the current FDA label for the brand-name product, glatiramer acetate is a mixture of synthetic polypeptides made from L-glutamic acid, L-alanine, L-tyrosine and L-lysine. Their average molar fractions are 0.141, 0.427, 0.095 and 0.338, and the average molecular weight is 5,000 to 9,000 daltons. The label identifies the drug by this composition and weight range, and by specific antibodies, rather than by one defined sequence. Its CAS number is 147245-92-9.

That makes it unusual among peptide drugs. Most peptide therapeutics, such as the ones covered in peptides versus small molecules, are single molecules with a fixed order of residues. Glatiramer acetate is a population of chains of varying length and order, which also sets it apart from the antibody drugs discussed in peptides versus antibodies.

Where glatiramer acetate came from

According to the Weizmann Institute, Ruth Arnon, Michael Sela and Dvora Teitelbaum synthesised copolymers in 1968 to mimic a component of myelin, hoping to induce an MS-like disease in animals (experimental autoimmune encephalomyelitis, or EAE). The copolymers did not cause the disease. In 1971 the team found that they blocked it instead. A small first patient trial followed in 1977, results of a pilot trial were published in 1987, and the drug was licensed to Teva. The FDA application was filed in June 1995, and approval came on 23 December 1996.

How glatiramer acetate is studied to work

The label says only that the drug is thought to act by modifying immune processes, and DrugBank notes that the mechanism has not been fully elucidated. Several hypotheses have been proposed. One is that the copolymer binds MHC class II molecules and competes with myelin antigens for presentation, an idea explored in a 2002 Journal of Clinical Investigation paper on related random copolymers. Another is a shift of T cells away from a pro-inflammatory Th1 profile toward a Th2 profile that releases IL-4 and IL-10. A third, called bystander suppression, proposes that such Th2 cells cross the blood-brain barrier, which the drug itself is not thought to do, and dampen inflammation locally. Regulatory T cells have also been suggested.

What the clinical evidence shows

The 1995 US pivotal trial (Johnson and colleagues, Neurology) randomised 251 people with relapsing-remitting MS and reported an annualised relapse rate of 0.59 on glatiramer versus 0.84 on placebo, a 29 percent relative reduction. The later GALA trial (Khan and colleagues, Annals of Neurology, 2013) tested a three-times-weekly regimen in 1,404 participants and reported 0.331 versus 0.505, a 34 percent relative reduction.

Head-to-head studies against interferon beta looked different. REGARD (764 participants, interferon beta-1a) found no difference in time to first relapse, with a hazard ratio of 0.94. BEYOND (2,244 participants, interferon beta-1b) found no difference in relapse risk. The smaller BECOME study (75 participants) compared MRI lesions and also found no difference, but was not powered for clinical outcomes.

Safety information on the label

In January 2025 the FDA added a boxed warning about anaphylaxis to Copaxone, Glatopa and other generics. The agency says the reaction is rare but can occur at any time after starting, including months or years later, and has led to hospitalisation and death. The label also lists an immediate post-injection reaction (about 16 percent on the 20 mg strength versus 4 percent on placebo), injection-site redness (43 percent versus 10 percent), lipoatrophy and skin necrosis (about 2 percent), chest pain, and a warning about liver injury. This is a summary for education and does not replace the full prescribing information.

Generic versions and the complexity problem

Because the active ingredient is a mixture, showing that a copy is equivalent is harder than for a single-molecule drug. Sandoz and Momenta received FDA approval for Glatopa 20 mg/mL on 16 April 2015, which the manufacturer described as the first substitutable generic of the product and as a complex generic. The same concept of heterogeneity is why researchers who study peptides care about characterisation and purity, a theme also seen in recombinant versus synthetic peptide production.

Frequently asked questions

Is glatiramer acetate a peptide?

It is a mixture of short polypeptide chains made of four amino acids, so it is peptide-like in chemistry, but unlike most peptide drugs it has no single defined sequence.

Why is it called a random copolymer?

The label specifies the average amino acid proportions and the weight range, not an order of residues. Describing it as random is a common shorthand for that heterogeneity.

Is it the same kind of drug as interferon beta?

No. Interferon beta is a single protein. The two classes have been compared in head-to-head trials, and REGARD and BEYOND found no difference in relapse outcomes between them.

Does this article give dosing or reconstitution guidance?

No. It describes published facts only. For general laboratory concentration arithmetic on other materials, see the reconstitution calculator, which is lab math and not medical guidance.

References

1. FDA Copaxone prescribing information (2026 label)
2. FDA Drug Safety Communication: boxed warning about anaphylaxis (22 Jan 2025)
3. Johnson KP et al. Copolymer 1 reduces relapse rate and improves disability in relapsing-remitting MS. Neurology 1995 (PMID 7617181)
4. Khan O et al. Three times weekly glatiramer acetate in relapsing-remitting MS (GALA). Ann Neurol 2013 (PMID 23686821)
5. Mikol DD et al. Interferon beta-1a versus glatiramer acetate (REGARD). Lancet Neurol 2008 (PMID 18789766)
6. O’Connor P et al. Interferon beta-1b versus glatiramer acetate (BEYOND). Lancet Neurol 2009 (PMID 19729344)
7. Fridkis-Hareli M et al. Novel synthetic amino acid copolymers that inhibit autoantigen-specific T cell responses. J Clin Invest 2002 (PMID 12070311)
8. Weizmann Institute: history of the copolymer research
9. Novartis/Sandoz: FDA approval of Glatopa 20 mg/mL (2015)
10. Cadavid D et al. BECOME study, Neurology 2009;72:1976-83 (interferon beta-1b vs glatiramer acetate, MRI endpoint)

Informational only — not medical advice. This article is for educational purposes. It does not recommend, sell or instruct personal human use of any compound. Consult a qualified healthcare professional for any health decision. Content is intended for adults 21+. Verify scientific details against the primary sources cited.