United States Patent 5,795,864: Scope, Claims, Expiration, and Omega-Conopeptide Patent Landscape

United States Patent No. 5,795,864 protects two related subject areas: stabilized omega-conopeptide formulations and the specific omega-conopeptides SNX-273 and SNX-279. The patent issued on August 18, 1998, and its ordinary 20-year term ran from the applicable U.S. nonprovisional filing date. Based on the patent’s priority and filing history, the enforceable term ended in November 2016, absent any applicable patent-term adjustment or extension.

The patent is therefore no longer an active barrier to generic, branded, or alternative omega-conopeptide development. Its historical importance is greater than its current exclusionary value. Claims 1-5 are formulation claims centered on prevention of methionine oxidation. Claims 6 and 7 are sequence-specific peptide claims.

What does United States Patent 5,795,864 protect?

Patent 5,795,864 protects stable formulations containing an omega-conopeptide and an antioxidant system capable of preventing methionine oxidation. The patent also claims two named peptides, SNX-273 and SNX-279, by their amino-acid sequences.

Claim group	Subject matter	Scope
Claims 1-5	Stable omega-conopeptide formulations	Broad formulation claim narrowed by buffer and antioxidant limitations
Claim 6	SNX-273	Exact peptide sequence identified as SEQ ID NO: 35
Claim 7	SNX-279	Exact peptide sequence identified as SEQ ID NO: 36

The formulation claims do not require a particular disease indication, route of administration, concentration, container, pH, or dosage regimen on their face. Their central limitation is chemical stability, specifically protection against methionine oxidation.

The peptide claims do not require the antioxidant formulation limitations in claims 1-5. Claims 6 and 7 operate as independent composition-of-matter claims, subject to the exact sequences disclosed in the patent specification.

How should claims 1 through 5 be construed?

What is the scope of claim 1?

Claim 1 covers:

An omega-conopeptide;
An antioxidant composition; and
An antioxidant composition capable of preventing methionine oxidation.

The claim is functional rather than limited to a single named antioxidant. A formulation may fall within the claim if the antioxidant system performs the specified stabilization function, even if the patent does not identify that particular antioxidant by name.

The claim does not require methionine itself. It covers any antioxidant composition that prevents, suppresses, or materially reduces oxidation of methionine residues in the omega-conopeptide, assuming the accused formulation satisfies the remaining claim limitations.

The broadest reasonable interpretation may reach formulations containing:

An omega-conopeptide other than SNX-273 or SNX-279;
A single antioxidant;
Multiple antioxidants;
A buffer with antioxidant activity;
Methionine as a sacrificial antioxidant; or
A combination of buffer and methionine.

The phrase “capable of preventing methionine oxidation” creates a performance limitation. A formulation would not infringe merely because it contains a chemical commonly regarded as an antioxidant. The relevant question is whether the composition performs the claimed stabilization function under the applicable formulation conditions.

What does claim 2 add?

Claim 2 narrows claim 1 by requiring that the antioxidant composition include a carboxylic acid buffer.

The claim does not appear limited to lactate. It can cover other carboxylic acid buffer systems if they satisfy the claim 1 antioxidant-function requirement. Potential examples could include acetate, citrate, succinate, or other carboxylic acid systems, depending on the patent’s specification and the construction of “carboxylic acid buffer.”

A buffer used only for pH control, without the claimed antioxidant function, presents a stronger non-infringement position. Claim 2 requires both the buffer category and the functional relationship to methionine oxidation.

What does claim 3 add?

Claim 3 further narrows claim 2 to a lactate buffer. A formulation must therefore contain:

An omega-conopeptide;
An antioxidant composition;
A carboxylic acid buffer;
Specifically, a lactate buffer; and
The claimed ability to prevent methionine oxidation.

The claim does not expressly require methionine. A lactate-buffered formulation could meet the claim if lactate, alone or with other components, satisfies the antioxidant-function limitation.

What does claim 4 add?

Claim 4 narrows claim 1 by specifying methionine as the antioxidant. The claim reaches formulations in which methionine is included as the relevant antioxidant component and is capable of protecting the omega-conopeptide against methionine oxidation.

This type of formulation commonly relies on preferential oxidation of free methionine in the formulation rather than oxidation of methionine residues in the peptide. The commercial and technical question is whether the amount and formulation conditions cause methionine to perform the claimed stabilizing function.

What does claim 5 add?

Claim 5 requires both:

Lactate buffer; and
Methionine.

It is narrower than claims 1, 2, 3, and 4. A formulation containing an omega-conopeptide, lactate buffer, and methionine would present the highest literal-overlap risk under the formulation claims, provided that the system prevents methionine oxidation as required by claim 1.

What are the scope and risks of claims 6 and 7?

What does claim 6 protect?

Claim 6 covers omega-conopeptide SNX-273 having the amino-acid sequence identified as SEQ ID NO: 35.

The claim is sequence-specific. It does not require:

A particular formulation;
An antioxidant;
A lactate buffer;
Methionine;
A therapeutic use;
Intrathecal administration; or
A specific manufacturing process.

A product with the exact SEQ ID NO: 35 sequence could fall within claim 6 regardless of whether it is supplied as a solution, lyophilized powder, salt, complex, or other pharmaceutical presentation, subject to the precise claim construction and chemical identity of the product.

The sequence itself must be taken from the patent specification. “SNX-273” is not a substitute for the sequence limitation in an infringement analysis.

What does claim 7 protect?

Claim 7 covers SNX-279 having the amino-acid sequence identified as SEQ ID NO: 36. Its structure and legal scope parallel claim 6.

Claim 7 is not limited to a formulation containing the antioxidant system described in claims 1-5. A manufacturer could therefore face claim 7 exposure even if it uses a different stabilizer, provided the product has the claimed sequence.

Are SNX-273 and SNX-279 the same as ziconotide?

They should not be treated as interchangeable names without sequence confirmation. Ziconotide is omega-conotoxin MVIIA, also known in development as SNX-111. Claims 6 and 7 identify SNX-273 and SNX-279, not SNX-111, based on the claim language supplied.

Claim 1 is broader because it covers an omega-conopeptide formulation without limiting the peptide to SNX-273 or SNX-279. That claim could historically have been relevant to formulations of other omega-conopeptides, including products related to ziconotide, if the formulation met the antioxidant and methionine-stability limitations.

How strong was the patent estate?

The patent had a mixed strength profile.

Claim category	Historical strength	Principal limitation
Claim 1	Moderate to strong	Broad functional language, but requires proof of methionine-oxidation prevention
Claim 2	Moderate	Requires a carboxylic acid buffer and the claim 1 function
Claim 3	Stronger literal specificity	Limited to lactate buffer
Claim 4	Stronger literal specificity	Limited to methionine as antioxidant
Claim 5	Strongest formulation overlap	Requires both lactate buffer and methionine
Claim 6	Potentially strong	Exact sequence must match SEQ ID NO: 35
Claim 7	Potentially strong	Exact sequence must match SEQ ID NO: 36

The formulation claims are narrower than a general patent on omega-conopeptide products. A competitor could attempt to avoid them by using:

A non-carboxylic-acid buffer;
A stabilizer that does not prevent methionine oxidation under the relevant test conditions;
A peptide lacking the claimed methionine residues;
A different antioxidant mechanism;
A different formulation that does not contain methionine; or
A different active sequence.

Those design-around strategies would not necessarily avoid claim 1, which is broader than claims 2-5.

When did United States Patent 5,795,864 lose exclusivity?

The patent’s ordinary term ended in 2016. The key dates are:

Event	Date
Earliest relevant priority period	1995
U.S. patent application period	1990s
Patent issued	August 18, 1998
Approximate ordinary expiration	November 2016
Current enforceability	Expired

Patent expiration eliminates infringement liability for conduct occurring after expiration. It does not eliminate historical liability for infringement occurring during the enforceable term. It also does not erase regulatory records, historical Orange Book listings, or prior settlement agreements.

A patent-term adjustment or patent-term extension would need to appear in the official patent record to change the ordinary expiration analysis. No such extension changes the commercial conclusion for present-day development: Patent 5,795,864 no longer provides a live exclusionary right.

What was the Orange Book status of Patent 5,795,864?

Patent 5,795,864 was historically relevant to the FDA-approved omega-conopeptide product Prialt, whose active ingredient is ziconotide. Its formulation subject matter was potentially relevant to an approved product even though claims 6 and 7 identify SNX-273 and SNX-279 rather than ziconotide.

The Orange Book analysis should distinguish three issues:

Whether the patent was listed against the relevant NDA;
Whether the listed claims covered the approved product or an approved use; and
Whether the patent remains unexpired.

The third issue is dispositive today. An expired patent cannot block an ANDA or an alternative commercial launch. Historical listing may still explain why a Paragraph IV certification or patent litigation arose during the patent term.

FDA approval of Prialt does not create current patent protection. Regulatory approval and patent rights are separate systems. The FDA Orange Book records patent and exclusivity information, but it does not extend an expired patent’s term. [1]

Were there Paragraph IV challenges or generic-entry disputes?

A Paragraph IV certification is relevant only while the listed patent remains capable of blocking approval or commercial launch. After expiration in 2016, a Paragraph IV challenge to Patent 5,795,864 has no practical role in current market entry.

The historical litigation risk would have centered on:

Whether an injectable omega-conopeptide formulation used the claimed antioxidant system;
Whether a formulation contained lactate buffer;
Whether methionine was present as the antioxidant;
Whether the formulation demonstrably prevented methionine oxidation; and
Whether an accused peptide had the exact SNX-273 or SNX-279 sequence.

A generic applicant could have pursued a Paragraph IV certification during the patent term if it believed the patent was invalid, not infringed, or unenforceable. The principal validity issues for the formulation claims would have included written description, enablement, indefiniteness of the functional language, anticipation, and obviousness. The sequence claims would have faced prior-art and written-description scrutiny focused on the disclosed sequences.

No current Paragraph IV barrier remains under this patent.

What patent litigation and settlements affect commercial risk?

The patent’s expiration makes new litigation under Patent 5,795,864 commercially immaterial except for historical damages, contract disputes, or disputes over conduct before expiration.

A settlement involving an ANDA filer could have delayed entry during the patent term, but a settlement cannot revive an expired patent. Any “licensed entry date” or launch restriction tied solely to Patent 5,795,864 would have lost practical effect when the patent expired unless it created an independent contractual obligation.

The relevant diligence distinction is between:

Patent-based restrictions, which ended with expiration; and
Contract-based restrictions, which may survive under their own terms.

Publicly reported Prialt revenue has not generally been separated in a way that permits a reliable standalone estimate of revenue attributable to Patent 5,795,864. The product has been commercially managed by different companies, including Eisai and later TerSera-related entities, but public disclosures do not establish that this patent independently generated a quantifiable royalty stream.

Is there biosimilar risk for this patent?

There is no conventional biosimilar pathway for Patent 5,795,864.

Ziconotide is a synthetic peptide drug, not a monoclonal antibody or other large biologic regulated through the standard biosimilar framework under section 351(k) of the Public Health Service Act. A competing product would more likely proceed through an abbreviated or full drug application pathway depending on the product’s formulation, active ingredient characterization, route, and reference-product status.

The relevant competitive risks are therefore:

Generic or follow-on injectable peptide products;
Formulation alternatives;
Compounded or hospital-use alternatives where legally permitted;
Intrathecal-pump products with different delivery characteristics; and
New analgesics that reduce demand for intrathecal ziconotide.

How does this patent compare with other omega-conopeptide patents?

Patent 5,795,864 is best classified as a stabilization and selected-peptide patent, not as the foundational patent for all omega-conopeptides.

Patent category	Primary protection	Relevance to 5,795,864
Foundational omega-conopeptide patents	Peptide structures, sequences, or therapeutic activity	Earlier and broader scientific platform rights
Ziconotide composition/use patents	SNX-111 or omega-conotoxin MVIIA and analgesic use	More directly relevant to Prialt
Patent 5,795,864	Antioxidant stabilization and SNX-273/SNX-279	Formulation and selected sequence layer
Manufacturing patents	Peptide synthesis, purification, folding, or isolation	Potential process barriers independent of 5,795,864
Device and delivery patents	Intrathecal pumps and delivery systems	Separate commercial and regulatory layer

The patent did not control every omega-conopeptide product. Its commercial importance depended on whether a product used the claimed stability strategy or contained one of the claimed sequences.

What generic launch scenarios exist after expiration?

After expiration, the main launch scenarios are:

Direct formulation competition

A competitor can develop a formulation containing an omega-conopeptide and methionine, lactate, or another antioxidant system without facing current infringement liability under Patent 5,795,864.

Alternative stabilization

A manufacturer may select a different buffer or antioxidant mechanism. This can reduce historical claim overlap and may provide formulation-development advantages.

Follow-on ziconotide products

A ziconotide product is not automatically covered by claims 6 or 7 because those claims are directed to SNX-273 and SNX-279. The principal question is whether the product’s formulation falls within the expired formulation claims or other unexpired patents.

New omega-conopeptide products

New sequences, including analogues with altered residues, may avoid claims 6 and 7 but could face separate patent rights covering the analogue, its use, or manufacturing method.

What geographic coverage did the patent provide?

United States Patent 5,795,864 provided rights only in the United States. Equivalent foreign applications, if granted, would have been governed by separate national rights and separate expiration dates.

For international development, the relevant review must include:

European Patent Office counterparts;
Canadian and Australian family members;
Japanese and other Asian counterparts;
National-phase status;
Patent-term adjustments or supplementary protection certificates; and
Local lapse, abandonment, or annuity records.

U.S. expiration did not automatically terminate foreign counterparts. The patent’s current U.S. freedom-to-operate value is therefore distinct from foreign-market analysis.

What manufacturing and intellectual-property barriers remain?

Patent 5,795,864 no longer creates a live U.S. manufacturing barrier. Other barriers may remain:

Reliable synthesis of disulfide-rich conopeptides;
Control of peptide folding and disulfide isomers;
Removal of truncated and misfolded impurities;
Sterile manufacturing;
Adsorption to containers and delivery devices;
Stability in intrathecal-pump systems;
Extractables and leachables;
Endotoxin control;
Device compatibility; and
Clinical and regulatory requirements for an intrathecal product.

These technical barriers may be substantial even after patent expiration. They are development and regulatory barriers, not enforceable rights under Patent 5,795,864.

Key Takeaways

Patent 5,795,864 covers stable omega-conopeptide formulations using antioxidant systems that prevent methionine oxidation.
Claims 2-5 narrow the formulation scope through carboxylic acid buffer, lactate buffer, methionine, and lactate-plus-methionine limitations.
Claims 6 and 7 separately claim SNX-273 and SNX-279 by exact sequence.
The patent’s ordinary U.S. term ended in November 2016.
The patent no longer blocks U.S. generic or follow-on entry.
A current ziconotide product is not automatically within claims 6 or 7 because those claims identify SNX-273 and SNX-279, not SNX-111.
Historical Orange Book listing and Paragraph IV relevance do not create current exclusivity.
No biosimilar pathway is required for this patent; competitive products would generally be assessed as generic or follow-on synthetic peptide products.
Remaining commercial barriers are more likely to involve formulation engineering, sterile intrathecal delivery, manufacturing quality, and other patent families.

FAQs

Does Patent 5,795,864 cover all omega-conopeptide formulations?

No. The formulation claims require an antioxidant composition capable of preventing methionine oxidation. A formulation lacking that functional characteristic would not satisfy claim 1.

Does a lactate buffer alone infringe claim 5?

No. Claim 5 requires both lactate buffer and methionine, in addition to the claim 1 limitations. Lactate alone may implicate claim 3, but not claim 5.

Does methionine in a formulation automatically satisfy claim 4?

No. The formulation must contain methionine as the antioxidant and must satisfy the claim 1 requirement that the antioxidant composition be capable of preventing methionine oxidation.

Can a competitor sell SNX-273 after the patent expired?

Yes, expiration removes the patent-based U.S. restriction. Separate patents, regulatory exclusivity, trade secrets, or contractual restrictions would require independent analysis.

Is an alternative peptide sequence automatically outside the patent?

It is outside the literal scope of claims 6 and 7 if it does not have SEQ ID NO: 35 or SEQ ID NO: 36. It could still face other patents or, in limited circumstances, an equivalence theory under other claims.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
U.S. Patent and Trademark Office. (1998). United States Patent No. 5,795,864: Stable formulations of omega-conopeptides. U.S. Department of Commerce. https://patents.google.com/patent/US5795864A
U.S. Food and Drug Administration. (2004). Prialt (ziconotide) prescribing information. FDA. https://www.accessdata.fda.gov
U.S. Food and Drug Administration. (2024). Approved drug products and patent and exclusivity information. FDA. https://www.fda.gov/drugs/drug-approvals-and-databases/drugsfda-data-files
United States Code, 35 U.S.C. §§ 154, 156, 271, 355. (2024). Patent term, patent-term extension, infringement, and abbreviated new drug applications. Congressional Legal Information Institute. https://www.law.cornell.edu/uscode/text/35

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0835126	⤷ Start Trial	CA 2005 00033	Denmark	⤷ Start Trial
European Patent Office	0835126	⤷ Start Trial	91181	Luxembourg	⤷ Start Trial
European Patent Office	0835126	⤷ Start Trial	SPC/GB05/033	United Kingdom	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,795,864

Summary for Patent: 5,795,864