US Patent 6,015,577: Claim Scope, Expiration, Orange Book Status, and Dipyridamole-Aspirin Patent Landscape

US Patent 6,015,577 protected an oral fixed-dose combination of dipyridamole and acetylsalicylic acid, commonly known as aspirin, with a dipyridamole-to-aspirin weight ratio of 8:1 to 100:1. Its narrower claims targeted the delayed-release multiparticulate design used for Aggrenox, including acid-containing dipyridamole pellets, enteric coatings, a separately coated aspirin tablet, and co-packaging in a capsule.

The patent was assigned to the Boehringer Ingelheim group and issued on January 18, 2000. Its US patent term expired in January 2017, subject to any applicable patent-term adjustment or extension recorded in the USPTO and FDA databases. It is no longer an enforceable exclusion right. The patent is historically important because it covered both the commercial composition and broad method-of-use concepts for secondary prevention of thrombotic stroke and related vascular events. [1][2]

What pharmaceutical technology does US Patent 6,015,577 protect?

The patent claims a coordinated dosage form in which dipyridamole and aspirin are physically combined but released differently.

Element	Claimed requirement
First active ingredient	Dipyridamole or a pharmaceutically acceptable salt
Second active ingredient	Acetylsalicylic acid or a pharmaceutically acceptable salt
Weight ratio	Dipyridamole:aspirin from 8:1 to 100:1
Dipyridamole presentation	Granules or pellets in claims 1-12; specified pellets in claim 15
Acid excipient	At least one equivalent relative to one mole of dipyridamole
Dipyridamole coating	Acid-resistant and intestinally soluble lacquer, optionally combined with an intestinally and gastric-insoluble lacquer
Aspirin presentation	Tablet, generally with a sucrose coating
Final container	Capsule containing the dipyridamole multiparticulates and aspirin tablet
Exemplary dose	Approximately 200 mg dipyridamole and 25 mg aspirin

The central technical objective is separation of the two active ingredients within one oral dosage form. Dipyridamole is formulated for delayed intestinal release, while aspirin is supplied as a separate tablet inside the same capsule. The acid excipient and enteric coating are intended to control dipyridamole dissolution and protect the active ingredient from the acidic gastric environment.

How do the individual claims differ?

Claims 1 and 2: granules versus pellets

Claims 1 and 2 are the principal formulation claims.

Claim 1 requires dipyridamole formulated as coated granules. Claim 2 substitutes pellets for granules. Both claims require:

dipyridamole and aspirin;
an 8:1 to 100:1 weight ratio;
an acid excipient with at least one equivalent per mole of dipyridamole;
a coating composed of 50% to 100% enteric, intestinally soluble lacquer;
0% to 50% lacquer insoluble in both gastric and intestinal fluids;
a separate aspirin tablet;
all components contained in a capsule.

The granule-pellet distinction may matter in an infringement analysis. The patent does not make every co-formulated dipyridamole-aspirin product fall within claims 1 and 2. A product must satisfy the specified multiparticulate structure and coating limitations.

Claims 3-6: acid excipient limitations

Claims 3-6 limit the acid excipient to:

fumaric acid;
tartaric acid;
citric acid;
succinic acid; or
malic acid.

Claims 5 and 6 narrow the list further to fumaric acid and tartaric acid. These dependent claims provide more specific targets for validity and infringement analysis because the excipient identity is expressly defined.

Claims 7-10: coating chemistry

Claims 7 and 8 identify permitted coating materials. The intestinally soluble coating may include:

methacrylic acid/methacrylic acid ester copolymers;
hydroxypropyl methylcellulose phthalate;
cellulose acetate phthalate;
ethylcellulose phthalate;
hydroxypropyl methylcellulose succinate;
cellulose acetate succinate;
hydroxypropyl methylcellulose hexahydrophthalate;
cellulose acetate hexahydrophthalate; or
hydroxypropyl methylcellulose trimellitate.

The gastric- and intestinal-insoluble component is based on acrylate, methacrylate, or mixtures of those materials, with up to 14% ethylcellulose.

Claims 9 and 10 impose a more specific coating composition: methacrylic acid/methyl methacrylate copolymer and hydroxypropyl methylcellulose phthalate in a ratio of 85:15 to 50:50. They also require a sucrose coating on the aspirin tablet.

Claims 11 and 12: dosage ranges

Claims 11 and 12 require:

dipyridamole: 75 to 400 mg; and
aspirin: 5 to 80 mg.

The commercial 200 mg/25 mg dosage falls within these ranges and also satisfies the 8:1 ratio in claim 14.

Claims 13 and 14: broad composition claims

Claim 13 covers an oral composition containing dipyridamole and aspirin in an 8:1 to 100:1 weight ratio. Unlike claims 1-12, it does not expressly require:

pellets or granules;
an acid excipient;
an enteric coating;
a separate aspirin tablet; or
a capsule.

Claim 14 narrows the composition to 200 mg dipyridamole and 25 mg aspirin. These claims have the broadest literal scope in the patent. Their validity would depend heavily on the prior art, written-description support, enablement, prosecution history, and the precise construction of "pharmaceutical composition for oral administration."

Claims 15-20: product-by-process-style formulation and methods

Claim 15 recites the commercial architecture in considerable detail:

dipyridamole pellets with an acid-excipient core;
a dipyridamole/polyvinylpyrrolidone first coating;
a lacquer coating containing methacrylic acid/methyl methacrylate copolymer and hydroxypropyl methylcellulose phthalate;
an aspirin tablet with a sucrose coating; and
a capsule containing both components.

Claims 16-20 are method claims directed to administration of dipyridamole and aspirin in the claimed ratio to inhibit:

venous or arterial clot formation;
transient ischemic episodes;
thrombotic strokes;
myocardial infarctions; and
vascular events in patients with arteriosclerosis.

What is the patent expiration date for US 6,015,577?

US Patent 6,015,577 issued January 18, 2000. Its ordinary US patent term ran for 20 years from the relevant nonprovisional filing date, not from the issue date. Public patent records and FDA product information associate the patent with an expiration in January 2017. Any enforceability analysis should use the USPTO Patent Examination Data System and the official patent-term calculation rather than the grant date alone. [1][3]

Event	Date or status
US patent issued	January 18, 2000
Patent owner or assignee	Boehringer Ingelheim-related entity
Technology	Dipyridamole-aspirin oral combination
Regulatory product associated with the estate	Aggrenox
Nominal expiration	January 2017
Current enforceability	Expired
Current Paragraph IV significance	Historical, not an active exclusion right

The patent cannot presently block a generic launch solely because the product practices claims 1-20. A new patent could still matter if it covers a distinct later-developed formulation, manufacturing process, dosage form, or use.

What was the Orange Book status of US 6,015,577?

The patent was associated with Aggrenox, the extended-release dipyridamole and aspirin product marketed by Boehringer Ingelheim Pharmaceuticals. Aggrenox contains 200 mg of extended-release dipyridamole and 25 mg of aspirin per capsule, matching the core dosage described in claim 14 and the detailed formulation in claim 15. [2][4]

The Orange Book listing was relevant to abbreviated new drug applications for generic Aggrenox. An ANDA applicant seeking approval before expiration could have addressed the listed patent through:

a Paragraph III certification accepting approval after patent expiration;
a Paragraph IV certification alleging that the patent was invalid, unenforceable, or not infringed; or
a statement that the listed patent did not claim the proposed product or approved method.

The Orange Book does not determine ultimate infringement or validity. It identifies patents submitted by the NDA holder and establishes FDA approval timing consequences under the Hatch-Waxman framework. [5]

What other patents covered Aggrenox and the dipyridamole-aspirin combination?

US Patent 6,015,577 was part of a broader patent estate rather than the only relevant patent.

Patent family or right	General subject matter	Commercial relevance
US 6,015,577	Dipyridamole-aspirin combination, multiparticulate formulation, ratios, and vascular-use methods	Directly associated with Aggrenox
US 5,616,599	Earlier dipyridamole-aspirin pharmaceutical composition technology	Earlier combination-product protection
Later formulation patents	Modified release, coating, pellet, capsule, and manufacturing features	Potentially relevant depending on product design and listing status
Method-of-use rights	Prevention of stroke and vascular thrombotic events	Relevant to labeled-use infringement and ANDA carve-outs

The earlier combination patent is important for prior-art analysis. Claims 13 and 14 of US 6,015,577 are substantially broader than the detailed pellet and coating claims. Earlier disclosure of dipyridamole plus aspirin in the relevant ratio could create anticipation or obviousness issues, while the multiparticulate architecture may supply the narrower claims with stronger technical differentiation.

A complete family analysis should separate:

priority applications;
US continuations and divisionals;
foreign counterparts;
terminal disclaimers;
patent-term adjustment;
Orange Book-listed patents; and
unlisted manufacturing or formulation patents.

How strong is the patent estate for US 6,015,577?

The estate had uneven claim strength.

Potentially stronger claim categories

Claims 1, 2, and 15 contain multiple structural limitations. A competing product would need to avoid at least one required element to escape literal infringement. Relevant design-around variables include:

using a tablet or conventional immediate-release blend instead of pellets;
using a different ratio outside 8:1 to 100:1;
removing the specified acid excipient;
using a nonclaimed coating system;
placing aspirin in a different dosage form;
using separate dosage units rather than one capsule; or
changing the dipyridamole release mechanism.

These limitations improve design-around potential for competitors, although they also make invalidity arguments easier if prior art discloses similar multiparticulate systems.

Potentially weaker claim categories

Claims 13 and 14 are commercially broad but technically sparse. They do not require the distinctive pellet, acid-excipient, coating, tablet, or capsule structure. A challenger could argue that the combination and dosage ratio were taught or suggested by earlier antiplatelet therapy literature, formulation patents, or known use of dipyridamole and aspirin together.

Claims 16-20 also raise method-claim issues. The claimed treatment results are broad, while the active ingredients and ratio are the principal limitations. Their scope may be affected by prior clinical use of the two drugs together and by whether the claimed vascular indications were already disclosed.

What Paragraph IV and generic-entry risks existed?

Before expiration, a generic applicant had several possible strategies:

Strategy	Effect
Paragraph III certification	Approval delayed until patent expiration
Paragraph IV certification	Immediate patent challenge and possible 30-month FDA stay
Section viii statement	Omit a patented method of use from the label
Formulation design-around	Avoid pellet, coating, acid-excipient, or capsule limitations
Different dosage ratio	Avoid the 8:1 to 100:1 range, where medically and regulatorily feasible

For a generic seeking the same 200 mg/25 mg product, claims 13, 14, and 15 were the principal risk points. A formulation identical to the detailed Aggrenox architecture could implicate claim 15 even if the generic applicant disputed the broader composition claims.

After the January 2017 expiration, the patent no longer created a standalone launch bar. Commercial risks shifted to FDA exclusivity, remaining unexpired patents, settlement restrictions, manufacturing capability, bioequivalence, and market access.

Does US 6,015,577 create biosimilar risk?

No. Dipyridamole and aspirin are small-molecule active ingredients. The relevant regulatory pathway is an ANDA under section 505(j), not a biosimilar application under section 351(k). Biosimilar concepts such as interchangeability, reference-product exclusivity, and biologic sponsor patent dance procedures do not apply.

The practical competitive issue is generic substitution for Aggrenox. FDA approval requires demonstration of pharmaceutical equivalence and bioequivalence, including the product's modified-release characteristics. [5]

What manufacturing and formulation barriers remain?

Patent expiration does not eliminate technical barriers. A competing manufacturer must reproduce or adequately substitute for the product's performance characteristics, including:

controlled intestinal release of dipyridamole;
aspirin stability;
separation of the two actives;
pellet size and coating uniformity;
dissolution across gastric and intestinal media;
capsule fill consistency;
stability under storage conditions; and
bioequivalence against the reference product.

The patent's detailed formulation claims identify commercially relevant process variables, but they do not create permanent protection for every manufacturing method. A generic can use a different excipient system or coating process if the resulting product remains bioequivalent and does not practice an unexpired patent.

How does US 6,015,577 compare with the earlier combination patent?

US 6,015,577 is best viewed as a later, more formulation-specific layer around a dipyridamole-aspirin combination.

Issue	US 6,015,577	Earlier combination protection
Core combination	Dipyridamole plus aspirin	Dipyridamole plus aspirin
Ratio	8:1 to 100:1	Depends on the earlier claims
Multiparticulate structure	Central to claims 1-12 and 15	May be less specific
Acid excipient	Expressly required in detailed claims	Depends on the earlier disclosure
Separate aspirin tablet	Required in detailed claims	Depends on the earlier claims
200 mg/25 mg dosage	Expressly claimed	May or may not be claimed
Current enforceability	Expired	Must be assessed separately by patent

The distinction matters because expiration of US 6,015,577 does not automatically establish freedom to operate against every related patent. Each patent must be evaluated independently for term, claim scope, prosecution history, and listing status.

Key Takeaways

US 6,015,577 covered dipyridamole-aspirin oral compositions, especially the Aggrenox-type 200 mg/25 mg capsule.
The core ratio is 8:1 to 100:1 dipyridamole to aspirin.
Detailed formulation claims require acid-containing dipyridamole granules or pellets, enteric coatings, a separate aspirin tablet, and a common capsule.
Claims 13 and 14 are materially broader because they omit most physical dosage-form limitations.
Claim 15 most closely tracks the commercial multiparticulate architecture.
The patent issued January 18, 2000 and expired in January 2017 based on the ordinary US patent term.
The patent is no longer an enforceable barrier to generic entry.
Aggrenox is a small-molecule product subject to ANDA review, not biosimilar review.
Later or related patents, manufacturing rights, regulatory exclusivity, and formulation differences must be reviewed separately.
The strongest historical infringement risk concerned products reproducing the 200 mg/25 mg pellet-in-capsule design.

FAQs About US Patent 6,015,577 and Aggrenox

Is US Patent 6,015,577 still active?

No. Its US patent term expired in January 2017 under the ordinary term calculation.

Does the patent cover dipyridamole and aspirin taken as separate products?

Claims 16-20 address administration of the two drugs in the claimed ratio, but the composition claims require specified pharmaceutical dosage-form features in the narrower claims. Separate-product use requires a separate analysis of the method claims and prosecution history.

What dose of Aggrenox is covered by the patent?

The principal commercial dose is approximately 200 mg dipyridamole and 25 mg aspirin per capsule, an 8:1 weight ratio.

Can a generic use a different enteric coating?

Potentially. A different coating may avoid literal infringement of claims requiring specific coating materials or ratios, but the complete patent estate and bioequivalence requirements must be assessed.

Why is a patent expiration date different from the issue date?

US patent term generally runs from the relevant application filing date, not from the patent's grant date. Patent-term adjustment, terminal disclaimers, and regulatory extensions can modify the final expiration date.

References

United States Patent and Trademark Office. (2000). U.S. Patent No. 6,015,577, Pharmaceutical composition comprising dipyridamole and acetylsalicylic acid.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book.
United States Patent and Trademark Office. (n.d.). Patent Examination Data System and Patent Center records for U.S. Patent No. 6,015,577.
Boehringer Ingelheim Pharmaceuticals, Inc. (n.d.). Aggrenox prescribing information.
U.S. Food and Drug Administration. (2015). Abbreviated new drug application regulations and patent certification requirements under the Hatch-Waxman Amendments.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	36 27 423	Aug 13, 1986

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0257344	⤷ Start Trial	SPC/GB98/043	United Kingdom	⤷ Start Trial
European Patent Office	0257344	⤷ Start Trial	C990001	Netherlands	⤷ Start Trial
European Patent Office	0257344	⤷ Start Trial	20/1999	Austria	⤷ Start Trial
Austria	59961	⤷ Start Trial
Australia	603146	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,015,577

Summary for Patent: 6,015,577