US Patent 8,673,341: Scope, Claims, Expiration, and Patent Landscape for Bimatoprost Intraocular Implants

US Patent 8,673,341 protects a treatment method using a biodegradable intraocular implant that places a prostamide, including bimatoprost, in the anterior chamber to reduce elevated intraocular pressure. Its commercial relevance is closely linked to Allergan’s Durysta bimatoprost implant. The patent does not broadly cover bimatoprost, topical glaucoma formulations, or every sustained-release ocular delivery system. Its principal limitation is the combination of a biodegradable implant, prostamide payload, anterior-chamber placement, and treatment of elevated IOP.

What does US Patent 8,673,341 cover?

US 8,673,341 is directed to methods of treating ocular conditions with biodegradable intraocular implants containing prostamides. The asserted claim set narrows progressively from a general method to a bimatoprost-specific method.

The core elements of claim 1 are:

Treatment of an ocular condition.
The condition is elevated intraocular pressure.
Placement of a biodegradable intraocular implant in the patient’s eye.
A therapeutic component associated with a biodegradable polymer matrix.
Release of an effective amount of the therapeutic component.
Placement in the anterior chamber.
The therapeutic component consists of a prostamide.

A product or procedure must satisfy each limitation of claim 1 to create literal infringement. A biodegradable implant containing a prostamide placed in the vitreous cavity, subconjunctival space, or posterior chamber would not literally meet the anterior-chamber limitation.

The claim language supplied by the requester uses “postamide” in claim 1. The later claims use “prostamide,” and claim 5 expressly identifies bimatoprost. The operative technical term is prostamide.

How do the individual claims differ?

Claim 1: broadest independent method claim

Claim 1 is the principal scope-defining claim. It is a method claim rather than a composition, device, or manufacturing claim.

The claim covers treatment using a biodegradable matrix implant, but it does not require:

A specific polymer;
A specified implant geometry;
A particular dose of prostamide;
A particular release rate;
A specified duration of treatment;
A named brand or formulation;
A particular surgical instrument; or
A particular prostamide structure beyond the claim term.

The requirement that the therapeutic component “consists of” a prostamide is materially narrower than language such as “comprises a prostamide.” That wording can exclude an implant in which the therapeutic component contains multiple active pharmaceutical ingredients, depending on how the term “therapeutic component” is construed. It does not necessarily require the entire implant to contain no other materials. The biodegradable matrix, excipients, coatings, stabilizers, and processing materials remain separate from the therapeutic component.

Claim 2: Markush genus for prostamides

Claim 2 limits claim 1 to prostamides meeting a detailed structural formula. The formula covers a broad chemical genus with variable:

Alkylene or alkenylene chains;
Cycloalkyl, aryl, or heteroaryl groups;
Amine substituents;
Oxo, hydroxyl, ester, and acyl groups;
Saturated or unsaturated hydrocarbon substituents; and
Optional heteroatoms and substituted ring systems.

The formula creates a chemical boundary around the prostamide class. A compound may be pharmacologically characterized as a prostamide but fall outside claim 2 if its structure does not satisfy every Markush limitation.

The missing chemical drawing for formula I prevents a complete atom-by-atom claim construction. The textual variables nevertheless show that claim 2 is intended to capture a family of prostamide analogs rather than bimatoprost alone.

Claim 3: further structural restriction

Claim 3 depends on claim 2 and narrows the covered prostamides through additional variables, including:

A bicyclic or substituted ring system;
Optional alkyl, halo, nitro, amino, thiol, hydroxy, alkoxy, alkylcarboxy, or haloalkyl substituents;
Defined stereochemistry; and
Limited values for x, y, and n.

This claim is narrower than claim 2 and may have greater validity resilience if the disclosed species and examples adequately support the claimed genus. It also creates a potential design-around route if a competing prostamide lacks the required ring substitution or stereochemical configuration.

Claim 4: extended release limitation

Claim 4 requires prostamide release into the eye for more than about one week after placement.

This limitation excludes an implant that releases its full payload within one week, although the meaning of “released into the eye” may depend on the specification and testing method. The phrase “about one week” introduces a range rather than a precise seven-day cutoff.

Claim 4 is particularly relevant to sustained-release implants. It is less relevant to conventional ophthalmic solutions, which are administered repeatedly and do not use an implant matrix.

Claim 5: bimatoprost-specific method

Claim 5 limits claim 1 to bimatoprost. It is the most commercially important claim because bimatoprost is the active ingredient in Durysta.

A bimatoprost implant placed in the anterior chamber for elevated IOP would fall within claim 5 if the implant is biodegradable and the bimatoprost is associated with a biodegradable polymer matrix. The claim does not require a particular bimatoprost concentration, implant size, insertion device, polymer chemistry, or duration of release.

What product is most directly affected by US 8,673,341?

Allergan and AbbVie Durysta

Durysta is a biodegradable intracameral bimatoprost implant approved by the U.S. Food and Drug Administration for reduction of elevated IOP in patients with open-angle glaucoma or ocular hypertension. Allergan developed the product, and AbbVie became the relevant corporate parent following its acquisition of Allergan.

Durysta is inserted into the anterior chamber through an ophthalmic delivery procedure. The product is designed to release bimatoprost over an extended period without daily topical dosing. Its approved use aligns closely with the elements of claims 1, 4, and 5. The FDA prescribing information identifies Durysta as a biodegradable implant containing bimatoprost and limits administration to one implant per eye, with repeat administration not established in the labeling at approval (U.S. Food and Drug Administration, 2020).

The patent therefore has direct product relevance, although infringement depends on the specific claim coverage, patent term, and any applicable regulatory or litigation developments.

What is the patent and regulatory timeline?

Event	Date or status
Earliest family priority	2001 family priority reported for the prostamide implant technology
US 8,673,341 granted	March 18, 2014
Patent owner or applicant associated with the family	Allergan, Inc.
FDA approval of Durysta	June 4, 2020
FDA pathway	New drug application
Active ingredient	Bimatoprost
Dosage form	Biodegradable intracameral implant
Route	Anterior chamber administration
Regulatory exclusivity	Product-specific FDA exclusivity applied at approval; bimatoprost itself was not a new molecular entity
Orange Book relevance	Product patents and regulatory exclusivity must be evaluated against the current FDA Orange Book listing

The base patent term cannot be determined solely from the grant number. Patent expiration depends on the earliest effective nonprovisional filing date, patent-term adjustment, terminal disclaimers, patent-term extension, and any applicable corrections. A patent that claims priority to an early filing may have a statutory expiration date materially earlier than later patents in the same product family.

For commercial diligence, the controlling date is the expiration date shown in the USPTO patent-term data and the FDA Orange Book listing, not the grant date.

What is the Orange Book status of US 8,673,341?

US 8,673,341 is relevant to Orange Book analysis for Durysta if it is listed against the approved drug product. The listing must be assessed by reviewing:

The current Orange Book patent table for Durysta;
The patent-use code, if any;
The listed expiration date;
Any patent-term extension;
Any delisting or correction history; and
Later continuation or improvement patents listed for the product.

The patent appears to be a method patent focused on intracameral prostamide implants. A listing of the patent would not necessarily block every bimatoprost generic. It would primarily affect an abbreviated new drug application directed to the same implant-based route, dosage form, and method of use.

A conventional bimatoprost ophthalmic solution would generally present a different product and method profile. It would not use a biodegradable intraocular polymer matrix or anterior-chamber implant. Such a product would therefore face a different patent analysis, including patents covering topical formulations, concentrations, preservatives, packaging, and glaucoma treatment methods.

When does US 8,673,341 lose exclusivity?

The patent’s enforceable expiration date depends on the official patent-term calculation. The relevant variables are:

The earliest effective nonprovisional filing date in the family;
Patent-term adjustment under 35 U.S.C. § 154;
Any terminal disclaimer;
Patent-term extension under 35 U.S.C. § 156; and
Whether a later continuation has a separate term.

FDA approval does not itself extend the patent. Regulatory exclusivity and patent exclusivity are separate rights. Durysta’s approval in 2020 could support FDA exclusivity based on the approval of new clinical investigations, but that exclusivity does not prevent all patent challenges and does not extend US 8,673,341 unless a formal patent-term extension was granted.

A definitive launch date for an implant competitor requires the later of:

Expiration or invalidation of relevant listed patents;
Expiration of applicable FDA exclusivity;
Resolution of any Paragraph IV litigation; and
Approval of the competing application.

What patents protect Durysta and the bimatoprost implant platform?

The relevant protection is likely distributed across several patent families rather than concentrated in US 8,673,341 alone.

Protection category	Relevance to Durysta
Prostamide implant method	Covers treatment using a biodegradable intraocular implant containing a prostamide
Bimatoprost-specific method	Directly targets the active ingredient used in Durysta
Polymer matrix composition	May cover biodegradable polymers, implant structure, porosity, and release behavior
Delivery device	May cover the applicator or insertion system used to place the implant
Manufacturing process	May cover molding, drying, drug loading, sterilization, or implant assembly
Dosing and administration	May cover implant size, repeat dosing, administration intervals, or patient selection
Formulation stability	May cover the chemical and physical stability of bimatoprost in the matrix
Method of use	May cover treatment of glaucoma or ocular hypertension with sustained-release bimatoprost

US 8,673,341 is not a complete substitute for a product-level freedom-to-operate review. A competitor could avoid one claim family and still infringe a polymer, device, manufacturing, or dosing patent.

How strong is the patent estate?

The estate has strong commercial relevance against a product that copies the Durysta architecture. Claim 5 is especially important because it identifies bimatoprost and retains the anterior-chamber implant limitation.

Strengths

The claims map closely to the approved intracameral bimatoprost product.
The anterior-chamber limitation distinguishes the invention from many posterior-segment implants.
Claim 5 provides a direct bimatoprost-specific position.
Claim 4 captures sustained release lasting more than approximately one week.
A product developer cannot avoid the claims merely by changing implant dimensions if the remaining limitations are unchanged.

Vulnerabilities

The claims are method claims, not broad composition claims.
The “effective amount” and “reduce a symptom” language may create factual disputes.
“Biodegradable polymer matrix” may require construction based on the specification’s polymer examples and degradation criteria.
The prostamide genus in claims 2 and 3 may face written-description or enablement challenges if the claims extend materially beyond the working examples.
Prior art involving prostaglandin analogs, biodegradable ocular implants, and sustained-release matrices may be combined in an obviousness challenge.
The anterior-chamber requirement gives competitors a potential design-around through a different ocular compartment or delivery route.

The narrower claims may be more defensible than a broad genus claim, but their commercial reach is correspondingly smaller.

Which companies are challenging or competing with the implant platform?

Glaukos iDose TR

Glaukos has developed iDose TR, a travoprost intraocular implant for glaucoma and ocular hypertension. It is a competing sustained-release implant platform, but its active ingredient and patent estate differ from bimatoprost and US 8,673,341. Glaukos’s technology demonstrates that competitors can pursue a different prostaglandin analog and implant architecture rather than copy the Durysta formulation.

Topical generic manufacturers

Generic manufacturers of bimatoprost ophthalmic solution compete with Durysta at the active-ingredient level but generally do not practice the asserted implant claims. Their exposure is more likely to involve patents covering topical formulations, concentration, preservative systems, or treatment methods.

Other sustained-release developers

Ocular Therapeutix, Envisia Therapeutics, and other ophthalmic drug-delivery developers have pursued sustained-release implants, inserts, and depot formulations. Their risk depends on the location of administration, polymer chemistry, active ingredient, release duration, and whether the product uses an intraocular implant in the anterior chamber.

What generic entry risks exist?

Direct implant generic

A generic or follow-on product that uses bimatoprost in a biodegradable implant placed in the anterior chamber faces the highest risk under claims 1 and 5. The applicant would need to address the listed patent through a Paragraph IV certification, a section viii statement where legally available, or a later filing date.

Topical bimatoprost generic

A topical solution is less exposed to US 8,673,341 because it lacks the implant and anterior-chamber limitations. It may still encounter other Orange Book patents or method-of-use patents, but this patent alone should not block a conventional topical product.

Non-bimatoprost prostamide implant

A non-bimatoprost prostamide could remain within claim 1 if it satisfies the claim’s broad prostamide limitation. Claims 2 and 3 would depend on whether the molecule falls within the structural formulas. A different active ingredient may avoid claim 5 but not necessarily claim 1.

Non-prostamide implant

A biodegradable anterior-chamber implant containing a non-prostamide active ingredient should not literally infringe the asserted claims. It could still face separate patents covering the implant matrix, device, manufacturing process, or ocular use.

Do Paragraph IV challenges affect this patent?

A Paragraph IV challenge is relevant only if an applicant files an ANDA or other abbreviated application that references an approved product and certifies that a listed patent is invalid, unenforceable, or not infringed. For US 8,673,341, the practical target would be an abbreviated application for a comparable biodegradable intracameral bimatoprost implant.

The statutory framework creates several possible outcomes:

The patent owner may sue within the statutory period, triggering a regulatory stay.
The challenger may seek a declaration of noninfringement or invalidity.
The parties may settle with a licensed or delayed-entry date.
The FDA may approve the product after patent and exclusivity barriers expire.
A section viii carve-out may be unavailable if the patented method is inherent in the referenced product’s labeled use.

A topical bimatoprost ANDA would ordinarily have a weaker connection to this patent because the ANDA product would not contain the claimed implant or use the claimed anterior-chamber placement method.

What litigation and settlement issues matter?

No litigation conclusion follows from the patent number alone. A current diligence review should distinguish among:

Patent infringement actions;
Inter partes review proceedings;
Post-grant review or reexamination;
ANDA litigation under the Hatch-Waxman Act;
Declaratory-judgment actions;
License settlements; and
Product liability or regulatory litigation unrelated to patent validity.

The key legal issues for this patent are likely to be claim construction, written description, enablement, obviousness, and infringement by an implant with a modified polymer or release profile. A settlement could permit early entry without invalidating the patent, while a successful validity challenge could remove the principal barrier before the stated term.

What manufacturing and intellectual-property barriers exist?

The polymer matrix and implant manufacturing process may create barriers that are independent of the chemical identity of bimatoprost. Important technical variables include:

Drug loading uniformity;
Implant dimensions;
Polymer molecular weight;
Degradation rate;
Sterilization conditions;
Residual solvent control;
Release kinetics;
Applicator compatibility;
Stability of bimatoprost during manufacturing; and
Accurate placement in the anterior chamber.

A design-around that changes the polymer may avoid a formulation patent but create new regulatory requirements. A change from a biodegradable implant to a nondegradable reservoir could avoid claim 1 while introducing separate device, surgical, and combination-product issues.

How does US 8,673,341 compare with topical glaucoma patents?

Issue	US 8,673,341	Topical bimatoprost patent
Product type	Biodegradable intraocular implant	Ophthalmic solution or suspension
Active ingredient	Prostamide, including bimatoprost	Usually bimatoprost
Administration	Anterior chamber placement	Topical ocular administration
Release profile	Matrix-mediated sustained release	Conventional repeated dosing
Primary claim type	Method of treatment	Composition, formulation, or method
Main infringement trigger	Implant placement and prostamide release	Composition and labeled or induced use
Main design-around	Change route, compartment, active, or matrix	Change concentration, excipients, or formulation

Key Takeaways

US 8,673,341 is a method patent for treating elevated IOP with a biodegradable anterior-chamber prostamide implant.
Claim 5 is the most commercially important claim because it specifically covers bimatoprost.
Claim 4 adds a sustained-release requirement exceeding approximately one week.
The patent does not broadly cover bimatoprost, topical bimatoprost solutions, or all ocular implants.
Durysta is the product most closely aligned with the asserted claims.
A competing intracameral bimatoprost implant faces materially greater risk than a topical generic.
Patent expiration must be determined from official USPTO term data and the current Orange Book, including any patent-term adjustment or extension.
Separate patents may cover the polymer, applicator, manufacturing process, dosing regimen, and product-specific formulation.
The principal validity issues are likely obviousness, enablement, written description, and construction of the prostamide and biodegradable-matrix limitations.
A Paragraph IV challenge would be most relevant to a follow-on intracameral bimatoprost implant, not a conventional topical product.

FAQs

Can a bimatoprost ophthalmic solution infringe US 8,673,341?

Generally, a topical solution would not meet the claim limitations requiring a biodegradable intraocular implant, biodegradable polymer matrix, and anterior-chamber placement.

Does changing the biodegradable polymer avoid the patent?

Not necessarily. Claim 1 does not identify a single polymer. A competing implant may remain within the claim if it uses a biodegradable polymer matrix and satisfies the other limitations.

Does US 8,673,341 cover posterior-segment implants?

The asserted claims require placement in the anterior chamber. A posterior-segment implant would not literally satisfy that limitation, although other patent claims could apply.

Can a competitor use a different prostaglandin analog?

A different prostaglandin analog may avoid claim 5, but it could remain within claim 1 if it qualifies as a prostamide. It may also encounter separate patents covering the implant platform or treatment method.

Is Durysta protected by this patent after FDA regulatory exclusivity expires?

FDA regulatory exclusivity and patent protection are separate. Expiration of regulatory exclusivity does not eliminate an unexpired patent, and patent expiration does not necessarily end all FDA exclusivity.

References

AbbVie Inc. (2023). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission.
U.S. Food and Drug Administration. (2020). Durysta (bimatoprost implant) prescribing information. FDA.
U.S. Food and Drug Administration. (2020, June 4). FDA approves first implant to reduce eye pressure in patients with open-angle glaucoma or ocular hypertension. FDA.
U.S. Patent and Trademark Office. (2014). U.S. Patent No. 8,673,341, Biodegradable intraocular implants containing prostamides. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
U.S. Congress. (2011). America Invents Act, 35 U.S.C. §§ 154, 156, 271, and 282. United States Code.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	E397934	⤷ Start Trial
Australia	2005244203	⤷ Start Trial
Australia	2007223057	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 8,673,341