US Drug Patent 8,450,287: Scope, Claim Analysis, Expiration, Orange Book Status, and Generic Risk

US Patent 8,450,287 protects a narrow ophthalmic formulation combining tobramycin, dexamethasone, deacetylated xanthan gum, an ionizable species, controlled viscosity, and an acidic pH. The claim set is directed to a formulation platform, not to tobramycin or dexamethasone as chemical entities.

The commercial product most closely aligned with the claims is Alcon's TOBRADEX ST ophthalmic suspension, containing 0.3% tobramycin and 0.05% dexamethasone. The principal infringement risk concerns generic or reformulated products that reproduce the xanthan-gum viscosity-control system rather than products containing the active ingredients alone.

What does US Patent 8,450,287 protect?

The patent claims a topical ophthalmic composition with five principal technical requirements:

Claim element	Independent claim 1 requirement
Tobramycin	0.1 to 0.5% w/v
Dexamethasone	0.03 to 0.1% w/v
Polymer	Deacetylated xanthan gum at 0.3 to 0.9%
Ionic component	Sufficient ionizable species to limit interaction between tobramycin and xanthan gum
Rheology and pH	10 to 700 cps at 6 sec-1 and 25°C; pH 5 to 6

The invention addresses the interaction between the cationic aminoglycoside tobramycin and anionic xanthan gum. Without sufficient ionic control, the formulation can develop excessive viscosity or inconsistent rheological behavior. The patent therefore combines composition limits with a functional viscosity result.

The claims do not require a particular bottle, dropper, preservative, particle-size distribution, sterilization method, or dosing schedule unless those elements are present in a dependent claim or in a separately asserted patent.

How broad is independent claim 1?

Claim 1 is moderately narrow in chemical composition and comparatively broad in its list of permissible ionic species.

A product must satisfy all of the following limitations to fall literally within the claim:

It must be an ophthalmically acceptable topical composition.
Tobramycin must be present at 0.1 to 0.5% w/v.
Dexamethasone must be present at 0.03 to 0.1% w/v.
The vehicle must contain deacetylated xanthan gum at 0.3 to 0.9%.
One or more ionizable species must be present in an amount sufficient to limit ionic interactions between tobramycin and the polymer.
Viscosity must be 10 to 700 cps at the specified shear rate and temperature.
The formulation must have a pH from 5 to 6.

The claim is therefore not satisfied by a conventional tobramycin/dexamethasone suspension that lacks deacetylated xanthan gum. It also may not be satisfied by a xanthan-containing product outside the claimed concentration or viscosity ranges.

The functional language concerning ionic interaction creates an important enforcement issue. An accused product may contain sodium chloride or another electrolyte, but the patent requires that the amount be sufficient to limit the interaction. The patentee would likely rely on formulation testing, viscosity measurements, rheological data, and composition records to establish that limitation.

What do dependent claims 2 through 12 add?

The dependent claims progressively narrow claim 1 and create fallback positions.

Claims 2 through 4: ionizable species

Claim 2 covers inorganic electrolytes, organic buffering agents, or combinations. Claim 3 lists specific species, including:

Sodium chloride
Potassium chloride
Calcium chloride
Magnesium chloride
Sodium sulfate
Sodium citrate
Potassium citrate
Sodium phosphate
Potassium phosphate
Sodium acetate
Sodium borate
Boric acid/mannitol complexes
Boric acid/sorbitol complexes

Claim 4 narrows the formulation to sodium chloride, sodium sulfate, or both.

These claims are important because sodium chloride and sodium sulfate are conventional excipients with broad regulatory acceptance. A generic manufacturer cannot avoid claims 2 to 4 merely by selecting an electrolyte from the listed group if the rest of the claim limitations remain present.

Claims 5 and 6: narrower viscosity ranges

Claim 5 limits viscosity to 10 to 300 cps. Claim 6 further requires an initial viscosity of 25 to 175 cps.

The initial-viscosity limitation is narrower than the general viscosity limitation and may be relevant to products designed to provide drop retention without excessive administration force. A formulation with viscosity above 300 cps could avoid claim 5 but remain within claim 1 if it does not exceed 700 cps.

Claim 7: in vitro/in vivo viscosity ratio

Claim 7 requires an in vitro/in vivo viscosity ratio of 0.01 to 0.65. This is a technically unusual limitation and may create both claim value and litigation risk.

The limitation requires a defined comparison between laboratory viscosity and in-eye behavior. The patent holder would need a reproducible methodology for measuring the in vivo component. Differences in test protocol, residence time, sampling, temperature, shear conditions, or animal and human models could affect enforceability and infringement proof.

Claims 11 and 12: commercial formulation profile

Claim 11 narrows the composition to:

Tobramycin: 0.3% w/v
Xanthan gum: 0.6% w/v
Dexamethasone: 0.05% w/v

Claim 12 adds a pH of approximately 5.7.

These limitations closely track the marketed TOBRADEX ST formulation profile. Claim 12 is the most commercially targeted claim in the set because it combines the common active-ingredient strengths with a specific polymer concentration and acidic pH.

What product is most closely associated with US 8,450,287?

TOBRADEX ST is the principal marketed product associated with the patent landscape. It is an ophthalmic suspension containing tobramycin 0.3% and dexamethasone 0.05%. The product uses xanthan gum as a viscosity-modifying excipient and has an acidic formulation environment consistent with the patent claims. [1]

The original TOBRADEX product and other tobramycin/dexamethasone products are not automatically covered. Product-by-product analysis is required because the patent claims depend on deacetylated xanthan gum concentration, ionic control, viscosity, and pH.

Product category	Likely relevance to US 8,450,287
TOBRADEX ST	High, because the active strengths and xanthan-gum system align with claims 11 and 12
Original TOBRADEX suspension	Depends on xanthan-gum content, viscosity, and pH; active ingredients alone are insufficient
Generic tobramycin/dexamethasone suspension without xanthan gum	Lower literal infringement risk
Tobramycin-only ophthalmic products	Outside the claimed combination
Dexamethasone-only ophthalmic products	Outside the claimed combination
Loteprednol/tobramycin products	Outside the claimed active-ingredient combination
Fluoroquinolone/steroid combinations	Outside the claimed active-ingredient combination

When does US Patent 8,450,287 expire?

The patent was granted on June 11, 2013. Its nominal patent term runs 20 years from the applicable nonprovisional filing date, subject to patent-term adjustment and any other statutory adjustment. Public patent records place the expected expiration in 2029. [2]

The patent should be analyzed separately from FDA regulatory exclusivity. Patent expiration does not determine whether an ANDA applicant can launch before that date. A generic applicant may file an ANDA with a Paragraph IV certification and litigate before expiration, subject to the statutory 30-month stay and settlement terms.

The relevant exclusivity framework is:

Protection type	Relevance
Patent term	Expected to extend into 2029, subject to the official USPTO term calculation
New chemical entity exclusivity	Not applicable to the old active ingredients tobramycin and dexamethasone
New clinical investigation exclusivity	Potentially relevant only if FDA granted qualifying exclusivity for the specific product or indication
Pediatric exclusivity	Would add six months only if separately awarded
Formulation patent	Central protection represented by US 8,450,287
Orange Book listing	Determines whether an ANDA applicant must address the patent through a certification

What is the Orange Book status of US 8,450,287?

US 8,450,287 is associated with the regulatory patent landscape for TOBRADEX ST. FDA Orange Book listings identify patents submitted by NDA holders for approved drug products and provide expiration information used by ANDA applicants. [3]

An Orange Book listing does not establish validity or infringement. It does, however, affect the ANDA pathway. An applicant generally must certify that:

No patent information has been submitted;
The patent has expired;
The applicant will wait until patent expiration; or
The patent is invalid, unenforceable, or will not be infringed.

A Paragraph IV certification can trigger patent litigation if the NDA holder sues within the statutory period. The resulting 30-month stay can delay approval, although it does not necessarily extend the patent term.

What Paragraph IV challenges and generic-entry risks exist?

A generic applicant would likely evaluate three principal design-around strategies.

1. Remove or replace deacetylated xanthan gum

The cleanest design-around is a formulation that uses a different viscosity modifier, such as a cellulose derivative, carbomer, polyvinyl alcohol, or another ophthalmic polymer. The applicant would need to confirm that the substitute does not meet the claim's deacetylated-xanthan limitation under an equivalents theory.

2. Change the polymer concentration

A formulation containing xanthan gum below 0.3% or above 0.9% may avoid claim 1. This strategy carries technical and regulatory risk because viscosity, suspension stability, drop size, ocular residence time, and patient tolerability may change.

3. Change the active concentration or pH

A product outside the claimed tobramycin, dexamethasone, or pH ranges may avoid literal infringement. The commercial value of this strategy is limited because the reference product's 0.3%/0.05% strengths are likely important to ANDA sameness and substitutability.

A Paragraph IV challenge could attack the patent on:

Obviousness based on known tobramycin/dexamethasone ophthalmic products, xanthan-gum vehicles, and electrolyte-controlled rheology;
Indefiniteness of "sufficient to limit ionic interactions";
Enablement or written-description issues concerning the breadth of ionic species and viscosity results;
Lack of reliable support for the in vitro/in vivo viscosity ratio in claim 7;
Noninfringement based on polymer identity, concentration, pH, or viscosity.

The strongest infringement position is likely against a product duplicating the 0.3% tobramycin, 0.05% dexamethasone, 0.6% xanthan-gum, sodium chloride or sodium sulfate, and approximately pH 5.7 profile.

How strong is the patent estate?

US 8,450,287 has meaningful commercial value but a narrower scope than a composition-of-matter patent.

Strength factor	Assessment
Active ingredients	Weak exclusivity position because both are established drugs
Formulation specificity	Stronger, particularly at 0.3%/0.05% strengths
Polymer limitation	Useful barrier against exact xanthan-gum copies
Functional viscosity limitation	Supports formulation differentiation but may create proof issues
Electrolyte limitation	Broadens coverage across conventional excipients
pH limitation	Narrows the claims and facilitates design-around
Manufacturing protection	Limited in the supplied claims; no process claims are shown
Regulatory leverage	Potentially significant if listed for TOBRADEX ST
Biosimilar protection	Not relevant because the product contains small-molecule active ingredients
Generic design-around potential	Moderate

The patent's commercial strength rests on the combination of limitations. Individual elements are generally familiar in ophthalmic formulation science. The inventive-position argument is more credible when based on the interaction between tobramycin, deacetylated xanthan gum, ionic species, and controlled viscosity.

What patent litigation and settlement issues affect the product?

A complete litigation assessment requires matching the patent against district-court complaints, ANDA notices, docket entries, and settlement filings. The supplied claims alone do not establish that a Paragraph IV case or settlement exists.

For transaction or launch analysis, the relevant litigation questions are:

Whether an ANDA applicant has certified against US 8,450,287.
Whether the NDA holder filed within 45 days of a Paragraph IV notice.
Whether the case produced a 30-month stay.
Whether a settlement permits an authorized generic or licensed launch.
Whether the settlement includes a payment, supply arrangement, or launch date.
Whether related continuation or divisional patents remain enforceable after the patent expires.

No biosimilar pathway applies. A competitor would use the ANDA pathway because tobramycin and dexamethasone are small molecules.

How does US 8,450,287 compare with competing patent strategies?

The patent differs from other ophthalmic exclusivity strategies in several respects.

Strategy	Typical protected subject matter	Relative position versus US 8,450,287
Active-ingredient patent	New chemical entity	Much broader, but unavailable for established actives
Salt or ester patent	Modified active ingredient	Not represented by the supplied claims
Formulation patent	Vehicle, polymer, pH, viscosity, stability	Directly represented
Method-of-use patent	Disease, dosing, or treatment method	Not represented by the supplied claims
Device patent	Bottle, nozzle, or delivery system	Not represented
Manufacturing patent	Sterilization, mixing, or suspension process	Not represented
Clinical exclusivity	FDA-approved new indication or formulation	Separate from patent rights

The patent does not prevent all generic tobramycin/dexamethasone products. It targets a defined delivery system designed to improve ophthalmic retention and manage polymer-drug interactions.

What geographic coverage does the patent provide?

US 8,450,287 provides rights only in the United States. Parallel protection would require separate patents in Europe, Canada, Japan, China, and other jurisdictions. Foreign family members may differ in claim scope, prosecution history, expiration, and enforceability.

A global launch assessment should not assume that the US claim set maps directly onto foreign rights. Patent families often contain narrower or broader claims abroad, and some jurisdictions may have no granted counterpart.

Key Takeaways

US 8,450,287 is a formulation patent, not an active-ingredient patent.
Claim 1 requires tobramycin, dexamethasone, deacetylated xanthan gum, an ionizable species, controlled viscosity, and pH 5 to 6.
Claims 11 and 12 closely target the 0.3%/0.05% commercial formulation profile associated with TOBRADEX ST.
Sodium chloride and sodium sulfate are expressly covered by dependent claims 4 and 10.
Generic risk is highest for an ANDA that copies the xanthan-gum vehicle and rheological profile.
A polymer substitution or concentration change may provide a practical design-around.
The patent's expected term extends into 2029, subject to the official patent-term calculation.
Biosimilar risk is not applicable; competitive entry would proceed through the ANDA pathway.
The principal legal vulnerabilities are obviousness, functional-language proof, indefiniteness, and noninfringement based on formulation differences.
Orange Book listing affects ANDA certification and litigation timing but does not establish patent validity.

FAQs

Does US 8,450,287 cover all tobramycin and dexamethasone eye drops?

No. The claims require deacetylated xanthan gum, an ionizable species, specified concentrations, viscosity characteristics, and pH limits.

Can a generic use sodium chloride and avoid US 8,450,287?

Not necessarily. Sodium chloride is expressly identified in dependent claims. Avoidance would require evaluating every claim element, including polymer concentration, viscosity, pH, and active strengths.

Is TOBRADEX ST a biologic product?

No. TOBRADEX ST contains small-molecule active ingredients and is regulated through the NDA and ANDA framework rather than the biosimilar pathway.

Does changing xanthan gum to another ophthalmic polymer eliminate infringement?

It may avoid literal infringement of the deacetylated-xanthan limitation. The formulation would still require an equivalents analysis and review of other patents in the product family.

Can a generic launch before the 2029 patent expiration?

Potentially. A generic applicant may challenge the patent through a Paragraph IV certification, litigate, settle, or launch after a successful invalidity or noninfringement outcome. FDA approval timing and any statutory stay must be assessed separately from the expiration date.

References

U.S. Food and Drug Administration. (2024). TOBRADEX ST ophthalmic suspension prescribing information.
United States Patent and Trademark Office. (2013). U.S. Patent No. 8,450,287, ophthalmic compositions comprising xanthan gum.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Harrow Eye	TOBRADEX ST	dexamethasone; tobramycin	SUSPENSION/DROPS;OPHTHALMIC	050818-001	Feb 13, 2009		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Details for Patent: 8,450,287

Which drugs does patent 8,450,287 protect, and when does it expire?

Summary for Patent: 8,450,287