United States Drug Patent 8,252,304: Claim Scope, Granisetron Formulation Protection, and Patent Landscape

United States Patent 8,252,304 protects controlled-release injectable granisetron formulations using a specified polyorthoester semi-solid delivery vehicle and polyethylene glycol monomethyl ether. The broadest claims require three technical elements: a qualifying polyorthoester, polyethylene glycol monomethyl ether, and granisetron at 1-5 weight percent. The narrower claims target the DETOSU/TEG/TEG-diGL polymer system, PEG monomethyl ether 550, defined polymer compositions, injectable administration, and a representative 78.4:19.6:2 formulation ratio.

The patent is directed to a drug-delivery platform rather than granisetron as a molecule. Its commercial relevance is strongest for long-acting subcutaneous granisetron products such as Sustol, formerly developed by Heron Therapeutics and originally associated with AP Pharma's APF530 program. The claims do not cover ordinary oral, intravenous, or transdermal granisetron products unless they also contain the claimed polyorthoester-PEG semi-solid system.

What does United States Patent 8,252,304 protect?

Patent 8,252,304 protects a composition containing:

A semi-solid delivery vehicle.
A particular polyorthoester polymer.
Polyethylene glycol monomethyl ether.
Granisetron at 1-5 weight percent.

Claim 1 is the principal platform claim. It uses structural limitations for the polyorthoester rather than merely identifying the polymer by trade name or manufacturing process.

Claim element	Requirement
Dosage-form vehicle	Semi-solid delivery vehicle
Polymer	Polyorthoester meeting the claimed Formula I structure
Polymer end-group or unit structure	R* is ethyl; n is 5-1000; specified A-unit chemistry
Modified A units	About 0.05-30 mol% of A units are the specified R1 units
Solubilizing or modifying excipient	Polyethylene glycol monomethyl ether
Active ingredient	Granisetron
Drug concentration	1-5 wt% of the total composition

A product must satisfy each limitation of an asserted claim for literal infringement. The presence of granisetron alone is insufficient. A conventional granisetron injection, oral tablet, transdermal patch, or solution would generally fall outside claim 1 if it lacks the claimed polyorthoester and PEG monomethyl ether vehicle.

How do claims 1 through 12 define the formulation?

Claims 1 through 12 form a nested composition and delivery-system claim set.

Claim 1: broad composition architecture

Claim 1 covers the combination of:

the defined polyorthoester;
polyethylene glycol monomethyl ether; and
1-5 wt% granisetron.

The claim is broad in several respects. It does not require a particular PEG molecular weight, exact polymer ratio, injection route, syringe, needle gauge, or release duration. It does require the polymer's structural parameters and the 1-5 wt% granisetron range.

The claim also allows a range of polymer chain lengths, with n from 5 to 1000, and broad structural ranges for p, s, and x. Those ranges create substantial chemical scope, subject to the exact interpretation of Formula I and the written description.

Claims 2 and 3: PEG molecular weight

Claim 2 limits PEG monomethyl ether to a molecular weight of 200-4000. Claim 3 narrows the excipient to PEG monomethyl ether 550.

PEG 550 is commercially important because it is the specific PEG species identified in claim 3 and in claims 13 and 14. A formulation using PEG 550 would satisfy this limitation if the remaining claim requirements are met.

Claim 4: PEG concentration

Claim 4 requires total PEG monomethyl ether at 5-60 wt% of the composition. This limitation separates the claimed vehicle from formulations containing only a minor PEG additive.

The term "total concentration" is relevant where multiple quantities of PEG monomethyl ether are present. A formulation using a chemically different PEG, such as PEG dimethyl ether or a PEG with a different terminal group, does not automatically meet the limitation.

Claim 5: representative commercial formulation

Claim 5 specifies:

78.4 wt% polyorthoester;
19.6 wt% PEG monomethyl ether; and
2 wt% granisetron.

This is a highly specific composition claim. The 2 wt% granisetron concentration is within claim 1's broader 1-5 wt% range, while the polymer and PEG amounts define a substantially narrower formulation.

A formulation with small manufacturing variation may still raise infringement issues under claim construction, measurement methodology, and any applicable doctrine of equivalents. Exact percentage deviations cannot be evaluated solely from the claim text.

Claims 6 through 9: performance and administration

Claim	Added limitation
6	Controlled release of granisetron
7	Suitable for injection
8	Suitable for subcutaneous injection
9	Filled into a syringe with a 16-25 gauge needle

Claims 6-9 add functional or product-configuration limitations. Claim 8 is particularly relevant to long-acting subcutaneous granisetron products. Claim 9 extends protection to a prefilled or syringe-based presentation, but it does not require a specific syringe volume, device manufacturer, injection site, or needle length.

"Suitable for" language can create claim-construction issues. A defendant may contest whether suitability is determined by design capability, actual use, labeling, or demonstrated performance.

Claims 10 through 12: polymer microstructure

Claims 10-12 narrow the polymer structure by specifying:

p of 1-7 in a portion of the units;
x equal to 2 in a portion of the units; and
s equal to 2 in a portion of the units.

These claims target subpopulations of the polymer's repeating or end-group units. They are narrower fallback positions if the broader Formula I limitations are challenged or avoided.

What do claims 13 through 19 protect?

Claims 13-19 provide an alternative route to infringement based on the polymer's named starting materials and reaction product.

Claims 13 and 14: DETOSU, TEG, and TEG-diGL

Claim 13 covers a composition comprising:

a reaction product of DETOSU, TEG, and TEG-diGL;
PEG monomethyl ether 550; and
1-5 wt% granisetron.

The reaction must contain TEG-diGL at about 0.05-30 mol% of total diols.

Claim 14 uses "consisting essentially of" rather than "comprising." It covers the same principal components but limits additional ingredients to those that do not materially affect the basic and novel characteristics of the claimed composition. This creates a narrower composition boundary than claim 13.

The identified reagents are:

DETOSU: 3,9-di(ethylidene)-2,4,8,10-tetraoxaspiro[5.5]undecane;
TEG: triethylene glycol; and
TEG-diGL: triethylene glycol diglycolide.

This structure-based and process-origin claim strategy can reach a product even where the final polymer is described differently, provided the accused polymer is the required reaction product and the composition meets the remaining limitations.

Claims 15 through 19: overlapping polymer and composition claims

Claim 15 combines the semi-solid vehicle format of claim 1 with the DETOSU/TEG/TEG-diGL reaction-product limitation.

Claims 16-19 narrow the TEG-diGL or modified-A-unit range from 0.05-30 mol% to 0.1-25 mol%.

Claims	Technical focus
13	DETOSU/TEG/TEG-diGL reaction product, PEG 550, granisetron
14	Same formulation with "consisting essentially of" language
15	Semi-solid vehicle using the specified reaction product
16	0.1-25 mol% modified A units
17	0.1-25 mol% TEG-diGL in claim 13
18	0.1-25 mol% TEG-diGL in claim 14
19	0.1-25 mol% TEG-diGL in claim 15

Claims 13-19 are narrower than claim 1 because they identify specific reactants or a narrower polymer composition. They may be commercially important because a drug developer often controls the manufacturing recipe and can identify whether DETOSU, TEG, and TEG-diGL were used.

What formulations are protected by Patent 8,252,304?

The strongest literal coverage applies to a long-acting injectable formulation with the following profile:

Parameter	Claimed commercial configuration
Drug	Granisetron
Drug loading	1-5 wt%, including 2 wt%
Vehicle	Semi-solid polyorthoester
PEG	PEG monomethyl ether, including PEG 550
PEG loading	5-60 wt% under claim 4
Polymer chemistry	DETOSU/TEG/TEG-diGL reaction product
TEG-diGL content	About 0.05-30 mol%, or 0.1-25 mol% in narrower claims
Administration	Injection, including subcutaneous injection
Presentation	Syringe with 16-25 gauge needle under claim 9
Release profile	Controlled release under claim 6

The patent does not claim every controlled-release granisetron formulation. A competing formulation based on microspheres, liposomes, an in situ gel, a biodegradable polyester, an osmotic system, or a transdermal patch would require separate analysis.

When does United States Patent 8,252,304 lose exclusivity?

The patent issued on August 28, 2012. A United States utility patent generally expires 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and any applicable statutory adjustment under 35 U.S.C. §§ 154 and 156.

The supplied claim text does not establish the effective filing date, patent-term adjustment, terminal disclaimer, or patent-term extension. The issuance date alone cannot produce a legally reliable expiration date. The patent term must be determined from the USPTO patent record and any FDA patent-term-extension record.

Patent expiration is separate from FDA regulatory exclusivity. Even if the patent has expired, other listed patents, regulatory exclusivity, injunctions, or product-specific litigation can affect launch timing.

What is the Orange Book status of the granisetron product?

Granisetron is an established small-molecule active ingredient. The relevant regulatory pathway is abbreviated new drug application litigation under the Hatch-Waxman Act, not the biosimilar pathway.

Sustol, an extended-release subcutaneous granisetron product, was approved by the FDA in 2016 for prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of moderately emetogenic or highly emetogenic chemotherapy. The product uses an extended-release delivery system distinct from conventional immediate-release granisetron products (U.S. Food and Drug Administration, 2016).

The Orange Book analysis should distinguish:

the reference listed drug for the extended-release subcutaneous product;
patents listed against that product;
patents listed against conventional granisetron tablets or injections;
FDA exclusivity codes;
whether a listed patent has expired, been delisted, or remains enforceable.

Granisetron products approved through different dosage forms or routes do not automatically share the same Orange Book patent estate. An ANDA applicant targeting oral granisetron does not necessarily confront the polyorthoester claims in Patent 8,252,304.

Which companies are challenging the granisetron patent estate?

The claim text identifies no Paragraph IV challenger, litigation defendant, settlement, or licensee. A Paragraph IV analysis requires the specific ANDA, notice letter, FDA Orange Book listing, and corresponding district-court or Federal Circuit docket.

The likely challenger categories are:

Generic manufacturers seeking approval for the same extended-release subcutaneous formulation.
Developers using an alternative long-acting delivery vehicle.
Manufacturers challenging the polymer claims while accepting that the granisetron product is covered by other patents.
Companies using a different concentration, PEG species, polymer precursor, or administration device.

A conventional generic granisetron product has a lower technical risk profile because it does not ordinarily use the claimed polyorthoester-PEG matrix. A same-formulation ANDA would face substantially higher risk if the reference product's formulation and manufacturing process map onto claims 1, 3, 5, 8, 13, or 15.

No settlement agreement or Paragraph IV judgment can be established from the supplied material.

How strong is the patent estate for the claimed formulation?

The patent has meaningful claim layering but a concentrated technology scope.

Strengths

Claim 1 covers the composition architecture at a relatively broad level.
Claims 2-5 capture commercially practical PEG and formulation ranges.
Claims 8 and 9 address the subcutaneous route and syringe presentation.
Claims 13-19 tie protection to identifiable manufacturing reactants.
The 78.4:19.6:2 formulation in claim 5 provides a precise fallback claim.
The claims cover both composition structure and polymer manufacturing origin.

Vulnerabilities

The claims depend on complex structural definitions that may create claim-construction disputes.
Polymer composition may vary with reactant ratios, reaction conversion, molecular-weight distribution, and analytical method.
"About" and "portion of the units" introduce boundary questions.
Functional language such as "controlled release" and "suitable for injection" may be contested.
A competitor may design around the claims using another polymer family, a different PEG terminal group, or a non-PEG vehicle.
Claims 13-19 may require proof of the manufacturing inputs or a legally sufficient equivalence theory.

The estate is strongest against a direct copy of the long-acting formulation and its manufacturing process. It is weaker against unrelated granisetron dosage forms and alternative delivery technologies.

What generic launch risks exist for the granisetron product?

Launch scenario	Patent risk	Commercial impact
Oral immediate-release granisetron	Low under this patent	Competes with existing generic products
Conventional injectable granisetron	Low under this patent	Does not replicate the claimed semi-solid vehicle
Transdermal granisetron	Low under this patent	Competes on route and adherence
Same polyorthoester and PEG 550 vehicle	High	Direct claim overlap likely
DETOSU/TEG/TEG-diGL formulation	High	Claims 13-19 directly target the chemistry
Different polyorthoester	Medium	Depends on Formula I mapping
Different PEG terminal group	Potentially lower	Requires analysis of literal and equivalent scope
Non-polyorthoester controlled-release system	Lower	More substantial formulation redesign

A generic applicant could pursue a Paragraph IV certification against listed patents, a section viii statement for nonprotected indications, or a formulation design-around. The economic value of a challenge depends on whether the target market is the extended-release subcutaneous product or the much larger conventional granisetron market.

How does this patent compare with competing granisetron products?

Product type	Route	Release profile	Relevance of Patent 8,252,304
Immediate-release granisetron tablet	Oral	Immediate	Generally outside the claim scope
Conventional granisetron injection	Intravenous or other injection	Immediate	Generally outside the claim scope
Sancuso	Transdermal patch	Extended delivery	Uses a different delivery technology
Sustol	Subcutaneous injection	Extended release	Closely aligned with the claimed technology
Alternative long-acting granisetron	Variable	Extended release	Risk depends on vehicle chemistry

Sancuso and Sustol compete on delayed or prolonged antiemetic coverage but use different delivery systems. The patent is more relevant to Sustol-type products than to transdermal or conventional injectable granisetron.

What licensing and manufacturing barriers apply?

The patent claims create two potential barriers:

Formulation access: use of the claimed polyorthoester and PEG monomethyl ether vehicle.
Manufacturing access: production of the specified DETOSU/TEG/TEG-diGL polymer.

A license covering only granisetron commercialization may not cover polymer manufacture. Conversely, a polymer-platform license may not authorize use of granisetron, a particular subcutaneous indication, or a specific syringe presentation.

Manufacturing diligence should examine:

identity and purity of DETOSU;
TEG and TEG-diGL feed ratios;
molar percentage of TEG-diGL;
polymer molecular-weight distribution;
PEG 550 grade and terminal-group identity;
granisetron loading;
water content and viscosity;
syringe fill and needle compatibility;
in-process controls defining the final polymer.

Patent 8,252,304 does not by itself establish ownership of every polyorthoester platform patent, process patent, device patent, or formulation patent used in a commercial product. Freedom to operate requires family-level review across composition, synthesis, analytical control, filling, packaging, and method-of-use claims.

Is biosimilar risk relevant to Patent 8,252,304?

No. Granisetron is a chemically synthesized small molecule, so biosimilar litigation under the Public Health Service Act is not the relevant pathway. Competitive entry would normally occur through an ANDA or, for a materially different product, a 505(b)(2) application.

The principal regulatory risks are:

Paragraph IV certification against listed patents;
formulation equivalence for an ANDA;
clinical and bridging requirements for a 505(b)(2);
patent settlement restrictions under the Hatch-Waxman framework;
product-specific exclusivity and labeling limitations.

What is the revenue exposure from this patent?

The patent's revenue exposure is concentrated in the extended-release subcutaneous granisetron segment. It does not control the entire granisetron market.

The commercial exposure depends on:

sales of the protected extended-release product;
the number of unexpired continuation or related patents;
the product's reimbursement and chemotherapy-use profile;
availability of conventional generic granisetron;
whether a challenger can launch an alternative long-acting formulation;
the enforceability of the polymer and process claims.

A generic entrant that avoids the claimed vehicle may compete with the product without infringing this patent, although it may not provide equivalent duration, route, or clinical performance.

Key Takeaways

Patent 8,252,304 protects a polyorthoester-PEG monomethyl ether formulation containing 1-5 wt% granisetron.
The most commercially relevant species is a semi-solid injectable formulation using PEG monomethyl ether 550.
Claims 13-19 specifically target polymers made from DETOSU, TEG, and TEG-diGL.
Claim 5 covers a 78.4 wt% polyorthoester, 19.6 wt% PEG, and 2 wt% granisetron formulation.
Subcutaneous injection and syringe presentation are protected only by narrower dependent claims.
Conventional oral, transdermal, and immediate-release injectable granisetron products generally fall outside the principal claim architecture.
Granisetron is a small molecule; biosimilar risk is not applicable.
A reliable expiration date requires the effective filing date, patent-term adjustment, terminal-disclaimer, and patent-term-extension records.
The principal design-around routes are alternative polymer families, different PEG chemistry, different delivery systems, and non-equivalent manufacturing pathways.
The highest infringement risk applies to a direct copy of the extended-release polyorthoester formulation and its DETOSU/TEG/TEG-diGL manufacturing process.

FAQs About United States Drug Patent 8,252,304

Does Patent 8,252,304 cover all granisetron products?

No. It covers compositions containing granisetron in a defined polyorthoester and PEG monomethyl ether delivery vehicle. Conventional granisetron tablets, solutions, injections, and transdermal patches generally use different technology.

Does using PEG 550 alone infringe Patent 8,252,304?

No. PEG 550 is only one claim limitation. The formulation must also contain the claimed polyorthoester, the required granisetron concentration, and all other limitations of the asserted claim.

Can a 505(b)(2) applicant avoid Patent 8,252,304?

Potentially, but the regulatory pathway does not eliminate patent risk. A 505(b)(2) applicant using the same or substantially similar formulation may face listed-patent litigation or an infringement action.

Are formulation percentages measured by weight of the finished product?

The claims express the percentages as weight percent of the composition. Infringement analysis would require consistent determination of the finished composition, including treatment of residual solvents, water, processing aids, and excipient definitions.

Does claim 14 provide broader protection than claim 13?

No. Claim 14 is narrower because it uses "consisting essentially of" language. It may exclude additional ingredients that materially alter the basic and novel characteristics of the claimed composition.

Sources

United States Patent and Trademark Office. (2012). United States Patent No. 8,252,304.
U.S. Food and Drug Administration. (2016). Sustol (granisetron) extended-release injection prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products.
United States Code. (2023). 35 U.S.C. §§ 154 and 156; 21 U.S.C. § 355.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2005289425	⤷ Start Trial
Canada	2579297	⤷ Start Trial
China	101052376	⤷ Start Trial
European Patent Office	1796629	⤷ Start Trial
European Patent Office	2902012	⤷ Start Trial
European Patent Office	3424492	⤷ Start Trial
European Patent Office	3834817	⤷ Start Trial
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Details for Patent: 8,252,304

Summary for Patent: 8,252,304