US Patent 5,690,960: Scope, Claim Construction, Expiration and Omeprazole Patent Landscape

US Patent 5,690,960 protects an enteric-coated oral formulation containing crystalline magnesium omeprazole, with a subcoating between the drug core and enteric layer. Its central limitations are the magnesium salt’s crystallinity, the multilayer dosage form, and resistance of drug release to changes in enteric-coating thickness. The patent is expired under the ordinary 20-year patent-term rule, so it does not provide current US exclusionary rights. Its historical importance is as a formulation patent supporting magnesium omeprazole products such as delayed-release omeprazole dosage forms.

What does US Patent 5,690,960 protect?

The patent covers a pharmaceutical dosage form with four principal technical elements:

A core containing magnesium omeprazole.
Magnesium omeprazole with more than 70% crystallinity by X-ray powder diffraction.
One or more subcoating layers.
An enteric coating that protects the formulation from gastric conditions and permits release in the small intestine.

The independent product claim is claim 1. The independent process claim is claim 10. Claims 17 and 18 are method-of-treatment claims, while claim 22 is a second formulation claim focused on the crystalline magnesium salt.

The patent does not broadly cover all omeprazole formulations. It targets a defined combination of salt form, physical-state characteristics, coating architecture and gastrointestinal release behavior.

Patent identification

Item	Data
US patent	5,690,960
Subject matter	Oral pharmaceutical preparation containing crystalline magnesium omeprazole
Patent type	Formulation, manufacturing process and method-of-treatment patent
Patent holder at issuance	Astra Aktiebolag
Filing and priority	The patent claims an earlier foreign priority date; the enforceable term is governed by the applicable US filing and patent-term rules
Issue date	November 25, 1997
Current status	Expired
Principal dosage forms	Tablets, pellets, granules and multiparticulate formulations
Active ingredient	Magnesium omeprazole
Therapeutic class	Proton-pump inhibitor

The issued claims supplied in the question contain apparent transcription errors. Claim 6 likely means that the enteric coating constitutes “at least 1.0% by weight” of the core material. Claim 10 refers to applying coatings “in the presence of water,” not “in the pittance of water.”

How should claim 1 be construed?

Claim 1 is a combination claim. A potentially infringing product would need to satisfy all material limitations, not merely contain omeprazole magnesium or an enteric coating.

Magnesium omeprazole limitation

The core must contain a magnesium salt of omeprazole. A formulation containing omeprazole alone, omeprazole sodium, or another pharmaceutically acceptable omeprazole salt would fall outside this limitation, subject to claim construction and equivalents analysis.

The claim does not specify a particular magnesium-to-omeprazole stoichiometry in the text provided. The relevant limitation is the identity of the salt and its physical form.

More-than-70% crystallinity limitation

The salt must have more than 70% crystallinity as measured by X-ray powder diffraction. This is a substantive product limitation, not a merely descriptive statement.

The principal issues are:

The analytical method used for X-ray powder diffraction.
The reference standard used to calculate crystallinity.
Whether the tested sample is representative of the commercial batch.
Whether processing, milling, granulation or coating changes the measured crystallinity.
Whether the accused product contains more than 70% crystalline magnesium omeprazole before or after formulation.

Claims 14 and 15 add narrower physical properties:

Mean mass particle-size diameter below 30 micrometers.
Hygroscopicity below 2% by weight.

Those limitations are not required by claim 1 unless incorporated through dependent-claim enforcement or used to define the accused composition under another claim.

Subcoating limitation

The core must have a subcoating layer between the drug-containing core and the enteric layer. The subcoating may contain film-forming polymers or tablet excipients that are water-soluble or water-insoluble but disintegrating in water. It may also contain alkaline or pH-buffering compounds.

This layer is technically important because omeprazole is acid-sensitive. The subcoat can reduce direct interaction between the drug core and the acidic enteric-polymer environment. It can also provide mechanical separation and improve coating-process stability.

A product with only a drug core and an enteric coating would not satisfy the literal subcoating limitation of claim 1.

Enteric coating limitation

The dosage form must include an enteric layer. The claim permits a coating whose release performance does not materially change with coating thickness at the pH predominantly present in the small intestine.

The dependent claims identify possible coating materials, including:

Acrylate polymers.
Hydroxypropyl methylcellulose acetate succinate.
Hydroxypropyl methylcellulose phthalate.
Polyvinyl acetate phthalate.
Cellulose acetate trimellitate.
Cellulose acetate phthalate.

The claim does not require one specific polymer. It covers a class of enteric materials, with optional plasticizers, dispersants, colorants and pigments.

What formulations are protected by US 5,690,960?

The patent reaches several dosage-form configurations.

Formulation type	Claim coverage
Enteric-coated tablet	Claim 2 and broader claim 1
Enteric-coated pellets	Claim 3
Granules	Claim 16
Multiparticulate dosage form	Claims 3 and 16
Multiple subcoats	Claim 12
Multiple enteric layers	Claim 13
Overcoated product	Claim 9
Alkaline core	Claims 19 and 20
Fine-particle crystalline salt	Claim 14
Low-hygroscopicity salt	Claim 15

Tablets

Claim 2 narrows the formulation to a tablet. The tablet may contain a coated tablet core or compressed material containing coated pellets. The claim language supplied does not resolve whether every tablet component must be directly coated or whether the tablet can incorporate pre-coated multiparticulates.

Pellets and granules

Claims 3 and 16 cover pellet and granule cores. This is commercially relevant because proton-pump inhibitors are often delivered as multiparticulate delayed-release systems. Pellets can be filled into capsules or compressed into orally disintegrating tablets while retaining individual enteric coatings.

Alkaline reacting compounds

Claims 19 and 20 cover a core containing an alkaline reacting compound. Examples commonly used in acid-sensitive formulations include alkaline salts, buffering agents and other excipients that maintain a favorable microenvironment around omeprazole.

The alkaline-core limitation narrows the claim but can increase practical relevance where a commercial product uses a buffered or alkaline formulation.

What manufacturing processes are protected?

Claim 10 covers a process involving:

Forming a core containing magnesium omeprazole with at least 70% crystallinity.
Applying at least one subcoating layer in the presence of water.
Applying at least one enteric coating layer in the presence of water.
Drying the finished formulation.

Claim 11 narrows the process where the subcoat is applied by a dry-coating process.

Process claim scope

The process claims focus on aqueous coating operations and the sequence of coating steps. A process using an organic solvent system, a different coating sequence, or a formulation that does not begin with the specified crystalline magnesium salt may avoid literal infringement.

The process claim also requires the defined crystalline starting material. A manufacturer using amorphous magnesium omeprazole, or a salt that falls below the specified crystallinity threshold, would have a potential noninfringement position for claim 10, subject to evidence concerning the actual material used.

Manufacturing barriers historically included:

Preparation of reproducible crystalline magnesium omeprazole.
Control of crystallinity during milling and granulation.
Control of moisture exposure.
Uniform application of the subcoat.
Enteric-release consistency across different coating weights.
Scale-up of aqueous coating and drying operations.

These barriers are technical and commercial rather than current patent barriers because the patent has expired.

How strong is the patent estate for magnesium omeprazole?

The patent’s strongest historical feature was the combination of a defined crystalline salt with a layered enteric dosage form. Each element addressed a recognized formulation problem:

Magnesium omeprazole supplied a particular salt form.
Crystallinity supported physical stability and reproducibility.
The subcoat protected the acid-sensitive active ingredient.
The enteric layer delayed release until intestinal conditions.
The coating-thickness limitation addressed manufacturing variability.

The main weaknesses were claim narrowness and dependence on measurable formulation characteristics.

Strength assessment

Issue	Assessment
Core salt limitation	Strongly limiting
Crystallinity threshold	Objective but technically contestable
Subcoat requirement	Strong literal limitation
Enteric coating	Broad across several polymer classes
Tablet and pellet coverage	Commercially relevant
Process coverage	Narrower than product claims
Method-of-use claims	Broad therapeutic scope but subject to enforceability and patent-term limits
Current blocking value	None because the patent is expired
Historical design-around potential	Material

A generic manufacturer could have pursued several design-around strategies, including a different omeprazole salt, a different physical form, an uncoated matrix with another release mechanism, or a dosage form lacking the claimed subcoating architecture.

When did US Patent 5,690,960 lose exclusivity?

US Patent 5,690,960 lost patent exclusivity after expiration of its applicable US patent term. Under the modern rule, utility patents generally expire 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension and transitional rules under the Uruguay Round Agreements Act.[2]

Because the patent issued in 1997 and claims an early-1990s development, its ordinary term ended approximately two decades after the applicable filing date, generally in the early-to-mid 2010s. The patent is no longer enforceable as an active US patent.

The patent should not be treated as a current barrier to generic or follow-on omeprazole magnesium development.

Exclusivity versus patent term

Patent expiration is separate from FDA regulatory exclusivity. FDA exclusivity may arise from new chemical entity, clinical investigation, orphan-drug or pediatric provisions. Those periods are shorter than the relevant patent term and do not revive an expired patent.[3]

For omeprazole magnesium products, the commercial question is now primarily regulatory and formulation-specific:

Whether the proposed product satisfies FDA requirements for a generic delayed-release product.
Whether the reference product is listed in the FDA Approved Drug Products with Therapeutic Equivalence Evaluations.
Whether any unexpired Orange Book patents remain listed against the relevant reference product.
Whether the applicant can demonstrate bioequivalence and appropriate acid-resistance and intestinal-release performance.

What is the Orange Book status of the patent?

US Patent 5,690,960 should not be treated as an active Orange Book patent right. The relevant FDA Orange Book analysis must be conducted by reference product, dosage form, strength and current listed patent records.[4]

An expired formulation patent can remain historically associated with a product without creating a current Paragraph IV barrier. Current generic applicants must review the live Orange Book listings for the specific omeprazole delayed-release reference product.

The patent’s claims also illustrate why Orange Book relevance can be product-specific. A claim directed to a formulation may be listable if it reads on an approved drug product, while a manufacturing or treatment claim may have different listing implications under FDA rules.

Which companies challenged or competed against this estate?

The patent was associated with Astra’s omeprazole franchise, including Losec and Prilosec-related commercial development. The competitive field included:

Generic omeprazole manufacturers.
Suppliers of omeprazole magnesium active pharmaceutical ingredient.
Manufacturers of enteric-coated pellets and capsules.
Developers of alternative proton-pump inhibitors.
Later suppliers of esomeprazole, lansoprazole, pantoprazole and rabeprazole.

A complete company-by-company Paragraph IV history cannot be established from the claims alone. The patent document does not identify every ANDA filer, settlement agreement, district-court action or later licensing arrangement. The operative commercial conclusion remains that the patent’s expiration removed it as a current litigation barrier.

What patent litigation and settlements affect the patent?

The claims supplied do not establish a present US litigation matter, active Paragraph IV case or enforceable settlement restriction. Any historical litigation analysis must distinguish:

Litigation involving US 5,690,960 itself.
Litigation involving related Astra patents.
Litigation involving Prilosec, Losec or omeprazole magnesium products.
Litigation involving esomeprazole or other proton-pump inhibitors.
FDA ANDA litigation based on separate Orange Book patents.

A settlement involving another Astra patent would not automatically restrict conduct under US 5,690,960. Conversely, expiration of this patent would not eliminate obligations under a separate, still-valid patent or contractual settlement.

What generic entry risks exist?

Current generic entry risk from US 5,690,960 is zero as a patent-term matter. The relevant residual risks are technical and regulatory.

Generic formulation risks

A generic applicant must control:

Acid resistance in the stomach.
Release at intestinal pH.
Stability under humidity and temperature stress.
Particle-size distribution.
Salt-form identity.
Crystallinity and polymorphic composition.
Coating uniformity.
Dissolution profile.
Bioequivalence.

A product can avoid the patent while still failing FDA requirements if its release profile or stability differs materially from the reference product.

Paragraph IV relevance

A Paragraph IV certification is relevant only to an unexpired patent listed for the applicable reference product. Because US 5,690,960 is expired, it should not independently support a current Paragraph IV challenge or 30-month stay.

A current ANDA strategy would focus on any live patents listed for the target omeprazole delayed-release product, together with regulatory exclusivity and product-specific certification requirements.[5]

How does this patent compare with competing proton-pump inhibitor patent estates?

Product or class	Core patent focus	Current relevance of US 5,690,960
Magnesium omeprazole	Crystalline salt and enteric multilayer formulation	Historical only
Omeprazole products	Drug substance, formulation, process and use patents	Separate estate
Esomeprazole	Enantiomer, formulations and uses	Separate estate
Lansoprazole	Drug substance and delayed-release formulations	Separate estate
Pantoprazole	Drug substance and formulation systems	Separate estate
Rabeprazole	Drug substance, formulations and uses	Separate estate

The patent is narrower than a basic compound patent but more technically specific than a conventional method-of-use patent. Its commercial value depended on formulation implementation and product linkage, not on ownership of the omeprazole molecule itself.

Key Takeaways

US Patent 5,690,960 covers crystalline magnesium omeprazole in a subcoated, enteric-coated oral dosage form.
Claim 1 requires more than 70% crystallinity measured by X-ray powder diffraction.
The patent covers tablets, pellets, granules, multiple subcoats, multiple enteric layers and optional overcoats.
Claims 10 and 11 cover aqueous coating processes and a dry-coating substep.
Claims 17 and 18 cover treatment of gastric-acid-related conditions.
The patent is expired and does not create current US patent exclusivity.
Current generic risk depends on live Orange Book patents, FDA requirements, bioequivalence and formulation performance.
The principal historical design-around options were changing the salt, physical form, coating architecture or manufacturing process.
Biosimilar risk is not applicable because omeprazole magnesium is a chemically synthesized small molecule, not a biologic.

FAQs

Does US Patent 5,690,960 cover omeprazole itself?

No. It covers a formulation containing magnesium omeprazole with specified crystallinity and coating layers. It is not a basic compound patent for all omeprazole.

Does the patent cover an amorphous magnesium omeprazole formulation?

Not literally under claims requiring more than 70% crystallinity. An amorphous product would require separate analysis under any doctrine-of-equivalents theory, but the patent’s express crystallinity limitation creates a substantial distinction.

Does an enteric-coated omeprazole capsule infringe automatically?

No. The capsule must satisfy all relevant claim limitations, including the magnesium salt, crystallinity threshold and subcoating requirement. A capsule using coated pellets could fall within the claims, but the factual formulation must be analyzed.

Is a biosimilar application required for magnesium omeprazole?

No. Magnesium omeprazole is a small-molecule active ingredient. Generic products generally proceed through the ANDA pathway rather than the biosimilar pathway.

Can the expired patent still affect a generic launch?

It can remain relevant as historical technical prior art and as a source of formulation information, but it cannot independently block launch through an enforceable US patent right.

References

United States Patent and Trademark Office. (1997). US Patent No. 5,690,960, oral pharmaceutical preparation containing magnesium omeprazole.
United States Code, 35 U.S.C. § 154. Patent term.
U.S. Food and Drug Administration. (2024). Drug exclusivity and generic drug development provisions.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
United States Code, 21 U.S.C. § 355(j). Abbreviated new drug applications and patent certifications.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Sweden	9302395	Jul 09, 1993

PCT Information
PCT Filed	July 08, 1994	PCT Application Number:	PCT/SE94/00681
PCT Publication Date:	January 19, 1995	PCT Publication Number:	WO95/01783

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	231719	⤷ Start Trial
Australia	681686	⤷ Start Trial
Australia	7198294	⤷ Start Trial
Brazil	9406941	⤷ Start Trial
Canada	2166483	⤷ Start Trial
China	1126946	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,690,960

Summary for Patent: 5,690,960