US Drug Patent 8,252,305: Scope, Claims, Expiration and Patent Landscape for Granisetron Extended-Release Injection

US Patent 8,252,305 protects methods of treating chemotherapy-induced emesis with an injectable, semi-solid granisetron depot containing a defined polyorthoester and polyethylene glycol monomethyl ether. The patent is directed to the formulation and its use, rather than to granisetron as a molecule. Its strongest commercial relevance is to SUSTOL, Heron Therapeutics' extended-release subcutaneous granisetron product.

The patent's central limitation is cumulative: an accused product must contain granisetron at the claimed concentration, a qualifying polyorthoester, polyethylene glycol monomethyl ether, and, for the narrower claims, specified polymer reactants, excipient ranges, structural parameters, or administration conditions.

What does US Patent 8,252,305 protect?

US 8,252,305 protects a method of treating emesis by administering a pharmaceutical composition comprising:

A semi-solid delivery vehicle;
A specific polyorthoester falling within the claimed formula;
Polyethylene glycol monomethyl ether; and
Granisetron at 1% to 5% by weight of the composition.

The patent issued on August 28, 2012. The claims are method-of-treatment claims, although they indirectly define the composition that must be administered. The patent therefore has product-by-process and formulation significance in an infringement analysis, even though it does not principally claim a composition in independent claim 1.

Core claim elements

Element	Claim 1 requirement
Therapeutic use	Treatment of emesis
Patient	Patient in need thereof
Dosage form	Pharmaceutical composition in a semi-solid delivery vehicle
Polymer	Defined polyorthoester of formula I
Polyorthoester backbone	R* is ethyl; n is 5 to 1,000
Functional units	About 0.05 to 30 mol% of A units are R1 units
Excipient	Polyethylene glycol monomethyl ether
Active ingredient	Granisetron
Granisetron concentration	1% to 5% by weight

The claim does not cover every granisetron formulation, every sustained-release formulation, or every polyorthoester. It requires the claimed combination.

How narrow is claim 1 of US 8,252,305?

Claim 1 is materially narrower than a conventional broad method claim because it incorporates detailed polymer chemistry. The relevant polyorthoester must have the specified structural architecture, including the ethyl-substituted backbone and the defined R1 and R3 units.

The formula limitations create several potential infringement and validity disputes:

Whether the accused polymer falls within the chemical definition of formula I;
Whether the polymer contains the required 0.05% to 30% molar proportion of R1 units;
Whether the polymer's molecular structure satisfies the definitions of p, s and x;
Whether polyethylene glycol monomethyl ether is present, rather than a different PEG derivative;
Whether granisetron constitutes 1% to 5% by weight of the complete composition;
Whether administration is performed for treatment of emesis rather than for another indication.

The phrase "about" applies to the molar percentage range. Its construction would depend on the intrinsic patent record, prosecution history and expert evidence. It does not automatically eliminate the need to prove that the accused polymer contains the required structural units.

What do claims 2 through 16 add?

The dependent claims create narrower positions directed to chemotherapy-induced emesis, injection, subcutaneous delivery, syringe gauge, PEG molecular weight, polymer composition and specific formulation ratios.

Claim	Additional limitation
2	Emesis induced by a chemotherapeutic agent
3	Administration by injection
4	Subcutaneous injection
5	Syringe with a 16-25 gauge needle
6	PEG monomethyl ether molecular weight of 200-4,000
7	PEG monomethyl ether 550
8	PEG monomethyl ether at 5%-60% by weight
9	Polyorthoester made from DETOSU, TEG and TEG-diGL
10	78.4% polyorthoester, 19.6% PEG monomethyl ether and 2% granisetron
11	p is 1-7 in a portion of the formula I units
12	x is 2 in a portion of the formula I units
13	s is 2 in a portion of the formula I units
14	PEG monomethyl ether at 5%-80% by weight
15	DETOSU/TEG/TEG-diGL polymer plus PEG molecular weight of 200-4,000
16	R1 units at approximately 0.1%-25% molar concentration

Claims 9, 10 and 15 are especially important commercially. They move from a structural definition to a manufacturing recipe or a precise formulation.

Why claim 10 is commercially significant

Claim 10 recites a formulation containing:

78.4 weight percent polyorthoester;
19.6 weight percent polyethylene glycol monomethyl ether; and
2 weight percent granisetron.

That ratio is close to a product-specific formulation claim. An accused product with materially different concentrations might avoid literal infringement of claim 10 while still presenting risk under claim 1 or another patent in the same family.

Claim 10 is also vulnerable to ordinary formulation variability disputes. The relevant questions would include whether the percentages are measured on a total composition basis, whether manufacturing tolerances are permitted, and whether the commercial product has a consistent composition across lots.

What formulation is associated with the SUSTOL granisetron product?

SUSTOL is a long-acting subcutaneous granisetron formulation approved by the FDA for prevention of acute and delayed nausea and vomiting associated with emetogenic chemotherapy. The product uses a polyorthoester-based delivery system and is administered by subcutaneous injection before chemotherapy.

The FDA-approved product is supplied as granisetron extended-release injection at 10 mg per 0.4 mL. The product's delivery system is designed to release granisetron over an extended period rather than provide the short exposure associated with conventional immediate-release granisetron injection. The label directs subcutaneous administration and does not authorize intravenous administration for the approved product.[2]

The claimed formulation in US 8,252,305 is therefore technically aligned with the commercial characteristics of SUSTOL, particularly claims 3, 4, 9, 10 and 15.

What patents protect SUSTOL and extended-release granisetron?

US 8,252,305 is one identified patent of interest for the SUSTOL formulation and method of use. Its value comes from the combination of:

Granisetron;
A semi-solid polyorthoester depot;
PEG monomethyl ether;
Subcutaneous administration; and
Treatment of chemotherapy-induced emesis.

A complete SUSTOL freedom-to-operate analysis should distinguish at least four patent categories:

Patent category	Relevance
Active-ingredient patents	Granisetron molecule and basic pharmaceutical salts
Depot-platform patents	Polyorthoesters and controlled-release delivery systems
Formulation patents	Specific polymer, PEG, drug concentration and composition ratios
Method-of-use patents	Treatment of chemotherapy-induced nausea and vomiting

US 8,252,305 is strongest in the third and fourth categories. It does not appear, from the claims supplied, to claim granisetron broadly as a chemical entity.

The relevant patent family should be reviewed for continuations, divisionals, terminal disclaimers, reexaminations, patent-term adjustment and related US filings. A family member with broader composition claims could present greater risk than the issued claims reproduced in the question.

When does US Patent 8,252,305 lose exclusivity?

The patent issued on August 28, 2012. Its ordinary expiration date is determined under the modern 20-year patent-term rules, measured from the earliest effective nonprovisional or international filing date, subject to patent-term adjustment, patent-term extension and terminal disclaimers.[1]

The issue date alone does not establish the expiration date. Patent-term calculations must account for:

The earliest effective nonprovisional filing date;
Any PCT filing from which priority was claimed;
Patent-term adjustment under 35 U.S.C. § 154;
Patent-term extension under 35 U.S.C. § 156;
Terminal disclaimers;
Any disclaimer or post-grant proceeding affecting enforceability.

The patent is not an old pre-1995 patent with a fixed 17-year term from issuance. Its enforceable term must be calculated from the application and priority record. The FDA Orange Book entry, if any, may show a listed patent expiration date, but that date should be reconciled against the USPTO patent file and any approved patent-term adjustment.

What is the Orange Book status of US 8,252,305?

The Orange Book is relevant because SUSTOL was approved under an NDA and US 8,252,305 may be listed against the approved drug product. Orange Book listing gives the NDA holder a mechanism to identify the patent to an ANDA applicant. It does not independently determine claim validity or infringement.[3]

For a generic or follow-on applicant, the practical questions are:

Whether US 8,252,305 is listed against the relevant SUSTOL NDA;
Whether the proposed product is the same dosage form and route;
Whether the applicant files a Paragraph IV certification;
Whether the NDA holder brings suit within the statutory period;
Whether the patent is still enforceable when the product could launch.

A listed method-of-use patent can be addressed through a section viii statement when the applicant carves out the patented indication, but that strategy is difficult where the formulation itself is also claimed or where the approved product's principal commercial use falls within the patented method.

What Paragraph IV challenges and litigation affect the patent?

A Paragraph IV challenge would be commercially significant because an ANDA applicant seeking a generic version of a complex subcutaneous depot product would need to address both patent scope and regulatory sameness.

The principal litigation theories would likely include:

Noninfringement because the proposed polymer is outside formula I;
Noninfringement because PEG monomethyl ether is absent or outside the claimed molecular-weight range;
Noninfringement because granisetron concentration is outside 1%-5%;
Invalidity based on anticipation or obviousness;
Lack of written description or enablement for the claimed polymer genus;
Indefiniteness of structural or "about" limitations;
A section viii carve-out for treatment uses not covered by the challenged claims.

A conventional small-molecule generic strategy is less straightforward here. The product is an injectable, semi-solid, controlled-release depot. FDA may require extensive chemistry, manufacturing and controls data, product-performance testing and, depending on the regulatory pathway, clinical or comparative data. A 505(b)(2) applicant could face a different patent and exclusivity profile from a conventional ANDA applicant.[4]

No settlement terms should be inferred from the patent claims. A settlement would require a separate agreement, court filing, or public company disclosure identifying the challenged patent and permitted launch date.

How strong is the patent estate for the polyorthoester formulation?

The estate has moderate-to-strong formulation relevance but narrower legal coverage than a broad composition patent.

Strengths

The claims require a specific drug-delivery platform rather than a generic sustained-release concept.
Claim 9 identifies the polymer reactants DETOSU, TEG and TEG-diGL.
Claim 10 identifies a commercially meaningful formulation ratio.
Claims 3 and 4 align with subcutaneous injection.
Claims 6 through 8 and 14 provide multiple PEG concentration and molecular-weight positions.
The method claims tie the formulation to chemotherapy-induced emesis, the principal clinical use.

Weaknesses and design-around opportunities

A competitor could use a different controlled-release polymer, such as a different polyorthoester composition or another biodegradable depot material.
A formulation could replace PEG monomethyl ether with another solvent, plasticizer or release-modifying excipient.
A product could use a granisetron concentration outside the claimed 1%-5% range, although that could affect dose volume and product performance.
A competitor could challenge the structural definitions of formula I through claim construction or validity arguments.
Claims 10 and 15 are narrow and may be avoided by changing the polymer ratio, PEG grade or component percentages.
Method claims require proof of the claimed treatment and administration steps, not merely possession or manufacture of a formulation.

The most difficult design-around would be a product that retains the same polyorthoester, PEG monomethyl ether and granisetron concentration while changing only nonessential manufacturing parameters. That approach would require a detailed claim chart and chemical characterization.

What manufacturing and intellectual-property barriers exist?

The principal barrier is technical replication of the polyorthoester depot, not granisetron supply. Manufacturing risk includes:

Reproducible synthesis of the DETOSU-based polymer;
Control of polymer molecular weight and distribution;
Control of residual monomers and reaction impurities;
Consistent incorporation of TEG and TEG-diGL;
Sterile manufacture of a viscous or semi-solid injectable;
Syringeability through the claimed needle range;
Stability of granisetron in the polymer matrix;
Release-rate consistency across commercial lots;
Container-closure compatibility;
Subcutaneous tolerability and local-site safety.

These manufacturing attributes may create barriers even if a competitor avoids literal infringement. Regulatory approval would require evidence that the alternative formulation is pharmaceutically equivalent or otherwise clinically appropriate for its chosen pathway.

How does US 8,252,305 compare with conventional granisetron patents?

Issue	US 8,252,305	Conventional granisetron patent
Primary subject	Formulation and treatment method	Active ingredient, salt or immediate-release formulation
Drug specificity	Granisetron required	May claim granisetron broadly or with other actives
Delivery system	Semi-solid polyorthoester depot	Usually oral, intravenous or conventional injectable
Route	Injection, with subcutaneous claim	Often route-specific or broader
Technical barrier	Polymer synthesis and sterile depot manufacture	Conventional pharmaceutical manufacturing
Generic risk	High formulation and regulatory complexity	Greater potential for standard ANDA substitution
Design-around	Alternative polymer, excipient or concentration	Alternative salt, formulation or dosage form

The patent's commercial value is therefore linked to the extended-release delivery system. Loss of protection would not remove patent barriers associated with separate granisetron formulations or unrelated antiemetic products.

What revenue exposure is linked to the patent?

US 8,252,305 is commercially relevant primarily through SUSTOL and any product using the same polyorthoester/PEG/granisetron platform. The patent does not cover the entire antiemetic market and does not block competing products such as conventional granisetron injection, oral granisetron, palonosetron or non-granisetron antiemetics.

Revenue exposure depends on:

Whether SUSTOL has material US sales;
Whether competing extended-release products enter;
Whether a generic or 505(b)(2) product can design around the claims;
Whether other unexpired patents provide additional protection;
Whether FDA exclusivity remains available independently of patent protection.

FDA approval does not guarantee market exclusivity after patent expiry. Conversely, expiration of US 8,252,305 would not necessarily permit immediate launch if other listed patents, regulatory exclusivities, injunctions or manufacturing barriers remain.

Key Takeaways

US 8,252,305 is a formulation-linked method patent for granisetron treatment of emesis.
Claim 1 requires granisetron at 1%-5% by weight in a semi-solid polyorthoester vehicle containing PEG monomethyl ether.
Claims 3 and 4 specifically cover injection and subcutaneous injection.
Claims 9, 10 and 15 are the most product-specific claims, covering the DETOSU/TEG/TEG-diGL polymer and a 78.4%/19.6%/2% composition.
The patent is technically aligned with SUSTOL, the FDA-approved extended-release subcutaneous granisetron product.
The patent does not claim granisetron broadly as a molecule.
Generic risk turns on polymer identity, PEG composition, drug concentration, route, treatment indication and any related family patents.
The expiration date must be calculated from the application record, patent-term adjustment and any terminal disclaimer. The issue date alone is insufficient.
An ANDA or 505(b)(2) applicant would face both patent and complex injectable-depot regulatory barriers.
The strongest design-around route is an alternative release platform or materially different polymer/excipient system.

FAQs

Is US 8,252,305 a composition patent or a method patent?

Its supplied claims are method claims. They require administering a composition with specified formulation characteristics to treat emesis.

Does the patent cover ordinary granisetron injection?

No. Ordinary granisetron injection would not infringe unless it also satisfies the claimed semi-solid polyorthoester, PEG monomethyl ether and concentration limitations.

Does claim 4 cover intravenous administration?

No. Claim 4 requires subcutaneous injection. Claim 3 broadly recites injection, but claim 1's formulation limitations remain necessary.

Can a competitor avoid the patent by changing only the needle size?

Usually, changing needle size alone would not avoid claim 1. It could avoid dependent claim 5 if the changed needle is outside the 16-25 gauge range, but the other limitations would remain relevant.

Does FDA approval of SUSTOL prove that every claim of US 8,252,305 is valid?

No. FDA approval and patent validity are separate legal determinations. Approval may establish product and indication facts, but it does not adjudicate novelty, obviousness, written description, enablement or infringement.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation guidance. https://www.uspto.gov
U.S. Food and Drug Administration. (2018). SUSTOL (granisetron) extended-release injection prescribing information. Heron Therapeutics, Inc.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov
U.S. Food and Drug Administration. (2024). Applications covered by section 505(b)(2). https://www.fda.gov
United States Patent and Trademark Office. (2012). US Patent No. 8,252,305, methods and compositions for treating emesis. https://patents.google.com/patent/US8252305B2/en

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
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,252,305

Summary for Patent: 8,252,305