United States Patent 8,043,628: Scope, Claim Construction, Expiration, and Patent Landscape

U.S. Patent No. 8,043,628 covers an intravitreal, bioerodible drug-delivery system used to treat ocular edema. The independent claim requires four elements: an immunosuppressive agent, a bioerodible polymer, placement in the vitreous, and treatment of eye edema. Dependent claims narrow the polymer to PLGA and impose release periods of at least five days or three weeks.

The patent is associated with Allergan’s biodegradable intravitreal implant technology, including technology used in the Ozurdex dexamethasone intravitreal implant platform. The patent’s practical blocking value is limited because its term has expired or reached the end of its ordinary statutory term, while related patents and regulatory protections must be analyzed separately.

What does U.S. Patent 8,043,628 protect?

Patent 8,043,628 protects a treatment method rather than a drug compound, implant structure standing alone, manufacturing process, or dosage regimen.

The operative claim is:

A method for treating edema in an eye by placing a bioerodible drug-delivery system containing an immunosuppressive agent and a bioerodible polymer in the vitreous of an individual’s eye.

The claim requires the following limitations:

Claim element	Scope
Therapeutic objective	Treatment of edema in an eye
Drug-delivery format	Bioerodible drug-delivery system
Active ingredient	Immunosuppressive agent
Polymer	Bioerodible polymer
Administration site	Vitreous of the eye
Claimed result	Treatment of ocular edema

The claim does not expressly require dexamethasone, PLGA, a particular implant size, a particular dose, a specific release profile, or a named disease such as diabetic macular edema or retinal vein occlusion.

That breadth is narrowed by the requirement that the system be placed in the vitreous. A topical formulation, subconjunctival injection, anterior-chamber implant, suprachoroidal delivery system, or systemic treatment would not ordinarily satisfy the literal placement limitation.

How should claim 1 of Patent 8,043,628 be construed?

Claim 1 is a method-of-treatment claim with structural and functional limitations.

“Treating edema in an eye”

The claim is directed to edema affecting ocular tissues. The specification and related implant patents associate this technology with macular edema and retinal edema, including edema linked to inflammatory and vascular conditions.

The claim language is broader than “treating macular edema” because it recites “edema in an eye.” A potential infringement analysis would examine whether the accused product is administered for an ocular edema indication and whether the treatment produces the claimed therapeutic result.

“Immunosuppressive agent”

“Immunosuppressive agent” is a genus-level limitation. It can encompass corticosteroids and other agents that suppress or modulate immune or inflammatory responses, depending on the specification and the court’s construction.

Dexamethasone is the commercially important example because Ozurdex contains dexamethasone. Other potentially relevant agents could include triamcinolone, fluocinolone, rapamycin-class compounds, cyclosporine-class compounds, or other anti-inflammatory immunomodulators, provided the particular compound falls within the patent’s written description and claim construction.

The term does not automatically cover every anti-inflammatory drug. A non-immunosuppressive anti-VEGF agent, for example, would raise a separate claim-construction issue.

“Bioerodible drug-delivery system”

The drug-delivery system must degrade or erode in the ocular environment and release the active agent. A nondegradable implant, permanent reservoir, conventional solution, or purely mechanical delivery device may not satisfy this limitation.

The claim is not limited to a particular implant geometry. It may cover microspheres, microparticles, pellets, rods, discs, matrix implants, or other bioerodible systems if they meet the claim requirements.

“Bioerodible polymer”

The polymer must contribute to the erodible delivery system. The claim does not require that the polymer be the only excipient or that it constitute a specified percentage of the implant.

Claim 2 narrows this limitation by requiring a polylactic acid-polyglycolic acid copolymer, commonly referred to as PLGA.

“Placing ... in the vitreous”

This is the principal route-of-administration limitation. The system must be placed in the vitreous, generally through an intravitreal injection or surgical implantation.

An implant positioned outside the vitreous, such as in the subconjunctival space or on the ocular surface, would fall outside the literal scope of claim 1 unless an equivalent theory were available. A drug that diffuses into the vitreous from another compartment also presents a material noninfringement argument because the claim requires placement of the delivery system itself in the vitreous.

What do claims 2 through 4 add?

Claims 2 through 4 narrow claim 1 in different ways.

Claim	Added limitation	Commercial significance
2	Polymer comprises PLGA	Targets the principal biodegradable polymer used in many ocular implants
3	Release for at least about five days	Excludes very short-duration delivery systems
4	Release for at least about three weeks	More closely targets sustained intravitreal implants

Claim 2: PLGA limitation

Claim 2 is narrower than claim 1 because it requires the bioerodible polymer to comprise PLGA. A delivery system using a different bioerodible polymer, such as polyanhydride, polycaprolactone, or a natural polymer, could potentially avoid claim 2 while remaining within claim 1.

The word “comprises” is open-ended. The claim does not require PLGA to be the only polymer. A system containing PLGA together with another polymer can still satisfy the claim.

Claim 3: Five-day release

Claim 3 requires delivery of the immunosuppressive agent for at least approximately five days. A product that releases drug over several weeks or months would generally satisfy this limitation if the release begins and continues for the required period.

The phrase “about five days” introduces a tolerance around the stated period. The exact boundary would depend on the specification, technical evidence, and claim-construction principles.

Claim 4: Three-week release

Claim 4 requires delivery for at least approximately three weeks. This claim is materially narrower than claim 3 and is more closely aligned with sustained-release ocular implants.

A product with a release duration of less than three weeks may avoid claim 4 while still potentially implicating claim 3 or claim 1.

What products and technologies are most closely associated with Patent 8,043,628?

The closest commercial technology is the dexamethasone intravitreal implant marketed as Ozurdex.

Product or platform	Active ingredient	Delivery technology	Relevance
Ozurdex	Dexamethasone	Biodegradable intravitreal implant	Closely aligned with the claimed immunosuppressive-agent, bioerodible-polymer, vitreous-placement concept
Retisert	Fluocinolone acetonide	Nonbioerodible intravitreal implant	Relevant ocular implant comparator, but not necessarily within the bioerodible limitation
Iluvien	Fluocinolone acetonide	Nonbioerodible injectable implant	Competing sustained-release technology with a different implant architecture
Yutiq	Fluocinolone acetonide	Nonbioerodible intravitreal implant	Comparator, but not a PLGA-based system
Dexamethasone suspension injections	Dexamethasone	Injectable suspension or solution	May avoid the bioerodible-system limitation

Ozurdex was approved by the FDA in 2009 for macular edema following branch retinal vein occlusion or central retinal vein occlusion and later received approval for diabetic macular edema and noninfectious posterior-segment uveitis. Its implant uses dexamethasone embedded in a biodegradable polymer matrix and is administered intravitreally.[1]

The product therefore presents a strong historical fit with the claim architecture, although infringement depends on the asserted claim, patent term, prosecution history, and the status of related patents.

When did Patent 8,043,628 expire?

Patent 8,043,628 was issued on October 25, 2011. It claims priority to an earlier application in the ocular implant patent family and has a statutory term measured from the applicable nonprovisional filing date, subject to any patent-term adjustment, terminal disclaimer, or other term calculation recorded by the USPTO.

The patent’s ordinary term reached its endpoint in the 2024 period. It is no longer a prospective long-term exclusion right for new products. Any current enforcement analysis must distinguish this patent from unexpired continuation, divisional, or related patents in the same family.

Event	Date or period
Earliest family priority	2003-2004 period
Patent issued	October 25, 2011
Ordinary 20-year term endpoint	2024 period
Current strategic status	Expired or at the end of its ordinary statutory term

The definitive status should be read from the USPTO Patent Center record, including any recorded term adjustment or disclaimer. The expiration of Patent 8,043,628 does not eliminate other patent barriers involving dexamethasone implants, PLGA formulations, applicators, manufacturing processes, or approved methods of use.

What is the Orange Book status of Patent 8,043,628?

Patent 8,043,628 has been associated with the Ozurdex regulatory patent estate. The FDA Orange Book identifies patents submitted by an NDA holder as claiming the drug substance, drug product, or approved method of use.[2]

The relevant Orange Book analysis has three parts:

Whether Patent 8,043,628 was listed against the applicable Ozurdex NDA.
Whether the listing remained active after the patent’s term ended.
Whether other listed patents continued to create a Paragraph IV certification or 30-month-stay risk.

An Orange Book listing does not independently extend patent term. Once a listed patent expires, it cannot support a new patent-based exclusion period. A generic applicant must still address every relevant listed patent and provide the appropriate certification under the Hatch-Waxman framework.

What Paragraph IV risks applied to this patent estate?

A generic applicant seeking approval for an equivalent intravitreal dexamethasone implant could face Paragraph IV issues relating to:

The dexamethasone-containing implant;
The PLGA or other biodegradable polymer matrix;
The implant’s release profile;
The intravitreal method of treatment;
The approved edema indications;
Manufacturing or applicator patents;
Related continuation patents.

A Paragraph IV certification asserts that a listed patent is invalid, unenforceable, or will not be infringed. If the NDA holder or patent owner brings suit within 45 days, FDA approval may be stayed for up to 30 months, subject to statutory exceptions and court developments.[3]

Patent 8,043,628 itself presents reduced current risk because its statutory term has ended. The practical risk would have come from a product that used a PLGA-based, sustained-release intravitreal immunosuppressive implant for ocular edema during the patent’s enforceable period.

What patent litigation affected Patent 8,043,628 and related Ozurdex patents?

The material litigation risk for Ozurdex has generally centered on the broader patent family and Orange Book-listed patents rather than on claim 1 in isolation.

Relevant disputes in this category typically involve:

Whether a proposed generic implant contains the claimed biodegradable polymer;
Whether the implant releases dexamethasone for the claimed duration;
Whether the proposed labeling induces infringement of ocular-edema methods;
Whether the asserted claims are anticipated or obvious over prior intravitreal implants;
Whether the claims have adequate written description and enablement;
Whether the listed patent properly claims the FDA-approved product or method.

A final litigation assessment requires the specific defendant, abbreviated new drug application, asserted patent list, and court docket. No single Patent 8,043,628 claim establishes the status of every related Ozurdex patent or settlement agreement.

How strong was the patent estate for this technology?

The patent estate was strongest when viewed as a layered portfolio rather than as Patent 8,043,628 alone.

Estate layer	Typical protection	Commercial effect
Implant composition	Dexamethasone or another immunosuppressive agent in a biodegradable matrix	Protects the core product
Polymer system	PLGA composition and degradation characteristics	Limits polymer substitutions
Release profile	Multi-day or multi-week delivery	Targets sustained-release products
Administration	Intravitreal placement	Covers the commercial route of administration
Method of use	Macular edema, retinal vein occlusion, diabetic macular edema, uveitis	Supports Orange Book method listings
Manufacturing	Mixing, molding, extrusion, sterilization, and implant formation	Can create process barriers
Applicator	Inserter or injection-device configuration	Can delay design-around implementation

Patent 8,043,628 was technically broad at the independent-claim level because it did not limit the active agent to dexamethasone or the polymer to PLGA. Its main weaknesses were the need to prove every method element, the functional treatment limitation, and the vulnerability of broad genus terminology to written-description, enablement, anticipation, and obviousness challenges.

The dependent PLGA and release-duration claims offered more product-specific coverage but also made design-around analysis easier. A competitor could target a different polymer, a different release duration, a nonimplant formulation, or an administration site outside the vitreous.

What generic launch scenarios exist for an intravitreal biodegradable implant?

Three commercial scenarios are material.

Scenario 1: Direct equivalent implant

A generic applicant markets an intravitreal dexamethasone implant with substantially the same biodegradable polymer, release period, and indications. This product has the highest historical infringement exposure but may receive approval after relevant patents expire or after a settlement date.

Scenario 2: Polymer or formulation design-around

A competitor uses a different biodegradable polymer or changes the implant’s release mechanism. This approach may avoid claim 2 while still requiring analysis under claim 1 and other family patents.

Scenario 3: Nonimplant alternative

A competitor uses an injectable suspension, solution, nonbioerodible implant, or different sustained-release platform. Such a product may avoid the claims of Patent 8,043,628 but would not necessarily be therapeutically interchangeable for FDA purposes.

The business value of a design-around depends on bioequivalence, comparative pharmacokinetics, duration of effect, injection procedure, safety, labeling, and reimbursement.

What manufacturing and intellectual-property barriers remain?

Even after Patent 8,043,628 expires, manufacturing barriers can remain significant.

A successful biodegradable ocular implant requires control over:

Drug-polymer compatibility;
Implant geometry and dose uniformity;
Polymer molecular-weight distribution;
Residual solvent levels;
Sterility and endotoxin limits;
Drug release over the intended period;
Injection-force requirements;
Stability during storage;
Batch-to-batch erosion behavior.

These characteristics can be protected through patents, trade secrets, regulatory data, know-how, and manufacturing controls. A competitor may avoid an expired composition claim yet still face process patents or difficulty demonstrating pharmaceutical equivalence.

How does Patent 8,043,628 compare with competing ocular implant patents?

Patent 8,043,628 is narrower than a composition-of-matter patent covering dexamethasone itself but broader than a claim limited to a specific implant dimension or formulation ratio.

Patent category	Breadth	Main risk to competitor
Active pharmaceutical ingredient patent	High for the molecule, if unexpired	Usually irrelevant for old generic dexamethasone
Biodegradable implant method patent	Moderate to high	Covers treatment, delivery system, and vitreous placement
PLGA formulation patent	Moderate	Targets polymer-specific implementations
Nonbioerodible implant patent	Separate technology	May apply to fluocinolone products, not necessarily PLGA systems
Method-of-use patent	Variable	Depends on approved indication and labeling
Manufacturing patent	Narrower but practical	Can constrain production without covering the finished product

The key distinction is that Patent 8,043,628 is a use-and-delivery claim. It does not necessarily block every ocular edema treatment or every dexamethasone product.

What is the geographic coverage of Patent 8,043,628?

Patent 8,043,628 has U.S.-only enforceability. Parallel protection may exist in Canada, Europe, Japan, Australia, and other jurisdictions through corresponding applications or national-phase filings, but each foreign patent has separate claims, prosecution history, term, and legal status.

A U.S. expiration does not establish expiration of foreign counterparts. The relevant diligence should compare:

Priority claims;
National-phase filing dates;
Grant status;
Patent-term adjustments or supplementary protection certificates;
Local claim scope;
Local litigation and settlement records;
Regulatory exclusivity in each market.

Key Takeaways

Patent 8,043,628 covers a method of treating ocular edema by placing a bioerodible immunosuppressive-agent delivery system in the vitreous.
Claim 1 is not limited to dexamethasone or PLGA, but it requires vitreous placement and a bioerodible delivery system.
Claim 2 specifically targets PLGA-containing systems.
Claims 3 and 4 add minimum release periods of approximately five days and three weeks.
The patent is closely associated with the biodegradable intravitreal implant technology used in Ozurdex.
Its statutory term reached its endpoint in the 2024 period, materially reducing current blocking value.
Related patents, Orange Book listings, manufacturing patents, and approved method-of-use claims remain relevant to generic entry.
The strongest historical infringement case would involve a PLGA-based, sustained-release intravitreal immunosuppressive implant used for ocular edema.
The main design-around routes are a different polymer, different delivery architecture, different release profile, or nonvitreous administration.
Expiration of this patent does not establish freedom to operate for all dexamethasone implants or all ocular-edema products.

FAQs About U.S. Patent 8,043,628

Does Patent 8,043,628 cover Ozurdex?

It covers a method that closely corresponds to the core Ozurdex delivery concept: a biodegradable intravitreal implant containing an immunosuppressive agent for treating ocular edema. It does not, by its text alone, establish coverage of every Ozurdex formulation, indication, manufacturing step, or applicator.

Does a non-PLGA implant avoid Patent 8,043,628?

It may avoid claim 2, which requires PLGA, but it could still implicate claim 1 if it contains an immunosuppressive agent, uses another bioerodible polymer, is placed in the vitreous, and treats ocular edema.

Does a five-day release product infringe claim 4?

Not necessarily. Claim 4 requires delivery for at least about three weeks. A product releasing drug for approximately five days may satisfy claim 3 but would generally present a noninfringement position against claim 4.

Does a topical ocular formulation fall within these claims?

Ordinarily no. The claims require placing the bioerodible delivery system in the vitreous. A topical formulation applied to the cornea or conjunctival surface does not meet that limitation literally.

Can an expired patent still block FDA approval?

An expired patent cannot support a new period of patent exclusivity, but a generic applicant must still address all relevant unexpired Orange Book patents and regulatory exclusivities. Expiration of Patent 8,043,628 alone does not resolve the full approval pathway.

References

U.S. Food and Drug Administration. (2009). Ozurdex dexamethasone intravitreal implant prescribing information. FDA.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, 21 U.S.C. § 355(j).
United States Patent and Trademark Office. (2011). U.S. Patent No. 8,043,628, methods for treating edema in an eye. USPTO.
U.S. Food and Drug Administration. (n.d.). Purple Book and patent-related regulatory resources. FDA.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	306951	⤷ Start Trial
Australia	2002236495	⤷ Start Trial
Australia	2006201271	⤷ Start Trial
Australia	3649502	⤷ Start Trial
Brazil	0115772	⤷ Start Trial
Canada	2429998	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,043,628

Summary for Patent: 8,043,628