US Patent 6,362,161: Claim Scope, Glatiramer Acetate Patent Landscape, and Generic Entry Risk

US Patent 6,362,161 covers a defined molecular-weight fraction of copolymer-1, the active pharmaceutical ingredient later commercialized as glatiramer acetate, when the fraction meets specified molecular-weight limits and is produced through a protected-polymer, hydrobromic-acid, trifluoroacetyl, and piperidine process. The patent was assigned to Teva Pharmaceutical Industries and expired in 2018. It no longer creates a blocking US patent right, but it remains relevant to historical Copaxone litigation, generic development, manufacturing know-how, and freedom-to-operate analysis.

What does US Patent 6,362,161 protect?

The patent protects a composition for treating multiple sclerosis that contains a therapeutically effective amount of a copolymer-1 fraction with a defined molecular-weight distribution.

The central claim requires all of the following:

Claim element	Required limitation
Therapeutic composition	A composition for treating multiple sclerosis
Active ingredient	A pharmaceutically effective amount of copolymer-1 fraction
High-molecular-weight limit	Less than 5% of species above 40 kDa
Principal molecular-weight range	More than 75% within approximately 2-20 kDa
Starting material	Protected copolymer-1
First chemical step	Reaction with hydrobromic acid
Intermediate	Trifluoroacetyl copolymer-1
Intermediate distribution	More than 75% of the molar fraction within approximately 2-20 kDa
Process control	Reaction time and temperature predetermined by test reaction
Deprotection step	Treatment with aqueous piperidine
Final product	Copolymer-1 meeting the specified distribution

The claim is narrower than a claim to all glatiramer acetate. It does not cover every copolymer-1 composition, every molecular-weight distribution, or every manufacturing process.

How should claim 1 be interpreted?

The claim combines composition and process limitations

Claim 1 is drafted as a composition claim that expressly incorporates a preparation process. That structure creates two potential infringement questions.

First, an accused product must satisfy the molecular-weight specifications. A product with more than 5% of species above 40 kDa would fall outside the literal claim, even if it were otherwise chemically similar.

Second, the claim states that the fraction "is prepared by" the specified process. An accused product may therefore be evaluated not only by its final molecular-weight distribution but also by whether it was made through the recited hydrobromic-acid and piperidine sequence.

The practical effect is that the claim is narrower than a pure product claim but potentially broader than a process claim directed only to the manufacturing steps. The precise treatment of the process language would depend on the claim-construction record and the applicable infringement analysis.

The molecular-weight limitations are quantitative claim boundaries

The claim contains two principal distribution thresholds:

Less than 5% of copolymer-1 species may exceed 40 kDa.
More than 75% must fall within approximately 2-20 kDa.

These limitations require analytical testing. Relevant evidence could include size-exclusion chromatography, calibrated molecular-weight standards, sample preparation protocols, integration methods, and the definition of "species."

The claim also uses both "species" and "molar fraction." That terminology can create disputes over whether the percentage is measured by molecule count, molar distribution, chromatographic area, mass distribution, or another validated analytical method. A party seeking to enforce the patent would need a reproducible testing protocol tied to the patent specification and prosecution history.

The process includes a predetermined reaction condition

The claim requires hydrobromic-acid treatment for a time and at a temperature "predetermined by test reaction." This limitation links process control to the target molecular-weight distribution. It is not merely a generic requirement to react protected copolymer-1 with hydrobromic acid.

The limitation may raise several factual questions:

Whether the manufacturer conducted a qualifying test reaction.
Whether the production reaction used time and temperature selected from that test.
Whether the resulting intermediate had the required distribution.
Whether the piperidine treatment preserved the distribution in the final copolymer-1 product.

These requirements increase evidentiary complexity and reduce the likelihood that a chemically similar product would automatically infringe.

What is the patent’s relationship to glatiramer acetate?

Copolymer-1 is the polymeric active ingredient associated with Copaxone, Teva’s multiple-sclerosis product. The active pharmaceutical ingredient is commonly identified as glatiramer acetate.

Glatiramer is a heterogeneous synthetic polypeptide composed of four amino acids: L-glutamic acid, L-alanine, L-tyrosine, and L-lysine. Unlike a conventional small molecule, it is characterized by a distribution of polymer lengths and sequence compositions. The molecular-weight limitations in US 6,362,161 address that heterogeneity.

The claim therefore targets a particular quality profile of glatiramer rather than a single discrete molecular entity. That distinction was commercially important because generic approval required demonstrating pharmaceutical equivalence and comparable product characteristics despite the absence of a single defined molecular structure.

When did US Patent 6,362,161 expire?

US Patent 6,362,161 was granted on March 26, 2002. Its term was tied to the patent’s earliest effective nonprovisional filing date and ended in 2018. Public patent records identify the patent as expired for failure to pay maintenance fees or as having reached the end of its enforceable term, depending on the record presentation. The practical result is the same: it is not a current US barrier to commercial manufacture or sale of glatiramer acetate.[1]

Event	Date or period
Patent grant	March 26, 2002
Patent term basis	20-year term from applicable earliest nonprovisional filing
Expected US term end	2018
Current status	Expired
Current blocking effect	None in the United States

Because the patent has expired, any historical patent-term adjustment, maintenance-fee event, or litigation settlement does not restore present-day exclusivity.

What patents historically protected Copaxone and glatiramer acetate?

Teva’s Copaxone estate included multiple patent families directed to different aspects of the product:

Patent or patent family	General subject matter	Strategic role
US 4,470,305 and related early patents	Copolymer-1 composition and therapeutic use	Foundational product protection
US 5,800,808	Copolymer-1 fractions and therapeutic use	Molecular-weight and product protection
US 6,048,898	Copolymer-1 compositions and use	Supplemental composition protection
US 6,342,476	Copolymer-1 or formulation-related protection	Layered product protection
US 6,362,161	Defined molecular-weight fraction and manufacturing process	Quality-profile and process-linked protection
US 6,620,847	Additional copolymer-1 composition protection	Later-expiring estate component
US 8,377,903 and related patents	Three-times-weekly 40 mg dosing regimen	Later method-of-use protection

Patent scope varied substantially across the portfolio. The early patents focused on the polymer and therapeutic use. Later patents attempted to protect molecular-weight distributions, formulations, dosing schedules, and manufacturing characteristics.

How strong was the patent estate for US 6,362,161?

The patent had meaningful commercial value before expiration because glatiramer acetate is difficult to characterize as a conventional generic active ingredient. The claim’s strength came from the combination of:

A clinically relevant product definition.
Quantified molecular-weight thresholds.
A process designed to control polymer degradation.
A manufacturing sequence involving protected copolymer-1.
The ability to assert the claim against a product, not only against a disclosed manufacturing facility.

Its weaknesses were equally material:

The claim covered only a particular distribution profile.
The process language created additional infringement proof requirements.
Analytical variation could affect whether a product met the thresholds.
The claim was vulnerable to invalidity attacks based on earlier copolymer-1 disclosures, obviousness, enablement, written description, and indefiniteness.
The patent’s term ended before the current wave of glatiramer competition matured.

The claim did not provide permanent protection for the glatiramer acetate molecule or for all therapeutic uses of copolymer-1.

Which companies challenged the Copaxone patent estate?

Sandoz was a major early challenger. The company filed an abbreviated new drug application for glatiramer acetate and litigated against Teva in federal court. The litigation involved several Copaxone patents, including patents directed to copolymer-1 compositions and dosing regimens.

The Federal Circuit addressed the Copaxone patent disputes in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc. The litigation illustrates the commercial importance of patent-family aggregation: a generic applicant could face multiple patents with different expiration dates even after the original product patent had expired.[2]

Other generic manufacturers later entered or pursued approval for glatiramer acetate products. The most significant approved US product was Glatopa, developed by Sandoz and Momenta Pharmaceuticals. The FDA approved Glatopa as a generic equivalent to Copaxone in 2015.[3]

What was the Orange Book status of US 6,362,161?

The Orange Book historically listed patents associated with Copaxone and its approved formulations. Orange Book listings identify patents submitted by the sponsor as covering the drug, its formulation, or an approved method of use. They do not establish that a patent is valid or infringed.

For US 6,362,161, the relevant commercial issue was historical listing and Paragraph IV certification. A generic applicant challenging an unexpired listed patent could certify that the patent was invalid, unenforceable, or would not be infringed. After expiration, the patent no longer supports a Paragraph IV-based exclusion period or a current injunction.

The FDA’s Orange Book remains the controlling source for current listed patent information, while the patent itself and court dockets control the legal history.[3][4]

Did US 6,362,161 create biosimilar risk?

No. Glatiramer acetate is a synthetic polypeptide drug regulated through the generic drug pathway rather than the biologics biosimilar pathway.

The relevant competitive route was an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act. FDA approval depended on pharmaceutical equivalence, bioequivalence, manufacturing controls, and product-quality comparability. The central regulatory issue was not biosimilarity under the Public Health Service Act.

This distinction matters for market-entry analysis:

Issue	Glatiramer acetate
Primary FDA pathway	ANDA
Product category	Synthetic complex polypeptide
Biosimilar approval pathway	Not the principal route
Key technical issue	Control and characterization of heterogeneous polymer
Primary patent risk	Composition, formulation, dosing, and process patents

What manufacturing and intellectual-property barriers remain after expiration?

Expiration of US 6,362,161 removed the patent barrier created by its claimed molecular-weight fraction and process. It did not eliminate operational barriers.

A manufacturer still needs to control:

Protected amino-acid chemistry.
Polymerization reproducibility.
Deprotection and hydrolysis conditions.
Molecular-weight distribution.
Residual solvents and reagents.
Aggregate and high-molecular-weight species.
Batch-to-batch composition.
Analytical comparability.
Sterile injectable formulation.
Regulatory documentation and process validation.

Trade secrets may protect reaction parameters, test-reaction design, analytical calibration, and scale-up controls even when patent protection has expired. Those trade secrets do not create the same exclusionary right as a patent, but they can raise development costs and delay commercial entry.

What generic launch scenarios existed for glatiramer acetate?

The principal US launch scenario was a staged erosion of Copaxone exclusivity:

Stage	Commercial effect
Foundational patent expiry	Opened the market to ANDA challenges
Litigation settlements and judgments	Delayed or shaped generic launch timing
20 mg daily generic launch	Initial price competition against daily Copaxone
40 mg three-times-weekly competition	Greater exposure to Teva’s later formulation and dosing patents
Multiple generic entrants	Increased price pressure and reduced Copaxone share

The commercial risk was higher for the 40 mg, three-times-weekly product because later method-of-use and formulation patents extended the relevant patent strategy beyond the molecular-weight patent at issue here.

How does US 6,362,161 compare with later Copaxone patents?

US 6,362,161 is primarily a product-quality and manufacturing-linked patent. Later Copaxone patents pursued different forms of protection.

Protection type	US 6,362,161	Later Copaxone patents
Molecular-weight distribution	Central	May be secondary or absent
Manufacturing process	Expressly incorporated	Varies by patent
Daily dosing	Not central to supplied claim	Common subject of method patents
40 mg three-times-weekly dosing	Not central	Major later protection category
Formulation	Limited in supplied claim	Covered in separate families
Current status	Expired	Depends on individual patent

A freedom-to-operate review cannot stop with US 6,362,161. It must examine surviving patents covering dosage strength, dosing frequency, formulation, device, manufacturing, and approved methods of use.

Key Takeaways

US 6,362,161 covers a defined copolymer-1 fraction used to treat multiple sclerosis.
The claim requires less than 5% of species above 40 kDa and more than 75% within approximately 2-20 kDa.
The claimed fraction must be prepared through protected copolymer-1, hydrobromic-acid treatment, trifluoroacetyl intermediate formation, and aqueous piperidine treatment.
The claim is narrower than a claim to all glatiramer acetate.
The patent expired in 2018 and is no longer a current US market-exclusion right.
Historical litigation centered on Teva’s broader Copaxone patent estate, including product, formulation, dosing, and process patents.
Glatiramer acetate competition proceeded through the ANDA pathway, not primarily through biosimilar regulation.
Manufacturing know-how and analytical control remain important even after patent expiry.
Current freedom-to-operate analysis must focus on later-expiring Copaxone patents and any nonpatent regulatory or trade-secret constraints.

Frequently Asked Questions

Is US Patent 6,362,161 still enforceable against a glatiramer acetate manufacturer?

No. The patent expired in 2018 and does not currently block US manufacture, approval, or sale.

Does the patent cover Copaxone by brand name?

No. It covers a defined copolymer-1 fraction and its specified preparation characteristics. Copaxone may have embodied the claimed subject matter, but the patent does not claim the brand itself.

Can a glatiramer acetate product avoid the claim by having a different molecular-weight distribution?

Yes. A product outside either quantitative distribution limitation may avoid literal infringement, subject to claim construction and any applicable doctrine-of-equivalents analysis. Because the patent is expired, that question is primarily historical or relevant to foreign jurisdictions with different patent status.

Was Glatopa approved as a biosimilar to Copaxone?

No. Glatopa was approved as a generic drug through the ANDA pathway. FDA classified the relevant competition as generic glatiramer acetate rather than a biosimilar product.

Which patent issues mattered most for generic Copaxone entry?

The main issues were validity, infringement, patent-term timing, Paragraph IV certifications, and the interaction among multiple composition, formulation, dosing, and manufacturing patents in Teva’s portfolio.

References

United States Patent and Trademark Office. (2002). United States Patent No. 6,362,161: Copolymer-1 fractions and methods of use thereof.
United States Court of Appeals for the Federal Circuit. (2013). Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 723 F.3d 1363.
U.S. Food and Drug Administration. (2015). FDA approves first generic glatiramer acetate for multiple sclerosis.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0762888	⤷ Start Trial	90987	Luxembourg	⤷ Start Trial
European Patent Office	0762888	⤷ Start Trial	C300096	Netherlands	⤷ Start Trial
European Patent Office	0762888	⤷ Start Trial	C300251	Netherlands	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,362,161

Summary for Patent: 6,362,161