United States Drug Patent 8,927,710: Claim Scope, Expiration, Orange Book Status, and CAP-Dependent Endonuclease Patent Landscape
United States Patent No. 8,927,710 covers broad chemical genera of influenza CAP-dependent endonuclease inhibitors, related salts and solvates, pharmaceutical compositions, and methods for treating influenza. The patent was assigned to Shionogi & Co., Ltd. and is associated with the baloxavir development program. Its principal commercial significance is the potential coverage of baloxavir or closely related compounds used in Xofluza, although exact product coverage depends on the structural formula omitted from the supplied claim text and the patent’s prosecution history.
The patent issued January 6, 2015, from an application claiming priority to an earlier Japanese filing. Its expected United States patent term runs to approximately February 8, 2030, subject to any patent-term adjustment, terminal disclaimer, or other term modification recorded by the USPTO. The claims are composition-of-matter claims supported by pharmaceutical-composition and influenza-treatment claims. They do not claim a particular dosage regimen, manufacturing process, formulation excipient system, or combination therapy in the text provided. [1]
What does United States Patent 8,927,710 cover?
Patent 8,927,710 contains two principal compound claim architectures.
| Claim group |
Subject matter |
Commercial relevance |
| Claims 1-8 |
CAP-dependent endonuclease inhibitor compounds of formula (I), including salts and solvates |
Broad chemical genus and fallback substituent limitations |
| Claims 9-21 |
A second, related compound genus using R1a, R2a, R3a, B1 and B2 variables |
More specific compound family with multiple structural narrowing positions |
| Claim 22 |
Pharmaceutical composition containing a claim 9-21 compound, salt or solvate |
Product composition coverage |
| Claim 23 |
Treatment of influenza by administering a claim 9-21 compound |
Method-of-use coverage |
The claims use Markush language. Each variable can represent multiple chemical substituents, including hydrogen, halogen, alkyl, alkenyl, alkynyl, alkoxy, carbonyl-containing groups, carbocyclic groups, heterocyclic groups, amino substituents, sulfonyl groups, amide groups and related functionality.
The central scaffold is defined by a ring system containing either:
- A carbon atom represented by CR5R6 and a nitrogen atom represented by NR7; or
- The reversed arrangement, with NR7 followed by CR5R6.
The claims also require that R5, R6 and R7 are not all hydrogen. In specified embodiments, R3 and one of the ring substituents can form a fused or additional heterocyclic ring.
This structure creates a large compound genus rather than a claim limited to one named molecule.
How broad are claims 1 through 8?
Claims 1 through 8 form a hierarchical narrowing sequence.
Claim 1 is the broad independent compound claim. It covers a CAP-dependent endonuclease inhibitor represented by formula (I), a pharmaceutically acceptable salt, or a solvate. R1, R2 and R3 each have extensive substituent definitions. The claim also covers two alternative heterocyclic arrangements involving A1, A2 and the R5-R7 substituent pattern.
Claims 2 through 4 narrow the R1 substituent options. The narrowing removes certain substituent classes while retaining alkyl, alkoxy, carbonyl, heterocyclic and amino-containing groups.
Claim 5 limits R1 to hydrogen or carboxy.
Claims 6 and 7 narrow R2. Claim 7 is particularly restrictive because R2 is limited to hydrogen or an optionally substituted lower alkyl group.
Claim 8 narrows R3 to selected alkyl, alkenyl, alkynyl, carbocyclic, heterocyclic, amino, sulfonamide, amide and related groups.
The practical claim strategy is conventional for a pharmaceutical compound patent:
- Claim 1 establishes a broad genus.
- Claims 2-4 preserve alternative substitution patterns.
- Claim 5 creates a simple fallback at R1.
- Claims 6-8 narrow the remaining positions toward specific lead-like compounds.
- The dependent claims provide positions that may be more defensible against prior-art references than the broad genus.
Because the structural drawing for formula (I) is not included in the supplied text, the scope cannot be reduced to a precise molecular structure or mapped conclusively to baloxavir without reviewing the issued patent figures and chemical definitions.
What do claims 9 through 21 protect?
Claims 9 through 21 define a second compound family. The variables are renamed R1a, R2a, R3a, B1 and B2, with substituent groups C and D corresponding broadly to the earlier substituent groups A and B.
Claim 9 is an independent compound claim covering:
- The compound represented by the second formula;
- Pharmaceutically acceptable salts;
- Solvates;
- Alternative B1/B2 arrangements;
- Broad substituent classes at R1a, R2a and R3a.
Claims 10 through 13 narrow R1a. Claim 13 limits R1a to hydrogen or carboxy, creating a potentially important fallback position.
Claims 14 and 15 narrow R2a. Claim 15 limits R2a to hydrogen or optionally substituted lower alkyl.
Claims 16 and 17 narrow R3a, with claim 17 retaining hydrogen, lower alkyl, carbocyclic, heterocyclic and carbocycle-lower-alkyl options.
Claims 18 through 20 narrow the B1/B2 arrangement and the R5a-R7a substitution pattern. Claim 18 specifies B1 as NR7a and B2 as CR5aR6a. Claims 19 and 20 further restrict R5a, R6a and R7a, including embodiments where R5a is hydrogen and R6a is hydrogen or substituted lower alkyl.
Claim 21 narrows R7a to a particular group shown in the patent drawing. That omitted structure may be important because it could correspond to a commercially relevant side chain or a defined lead compound.
The second claim group is therefore likely designed to protect a more focused series of CAP-dependent endonuclease inhibitors, with claims 18-21 providing the most structurally concentrated coverage.
Does Patent 8,927,710 cover baloxavir and Xofluza?
Patent 8,927,710 is associated with Shionogi’s influenza endonuclease inhibitor program and is relevant to the intellectual-property position for Xofluza. Xofluza contains baloxavir marboxil, an orally administered prodrug converted in vivo to baloxavir, also known as S-033447. The FDA approved Xofluza in 2018 for treatment of acute uncomplicated influenza and later expanded its use to post-exposure prophylaxis. [2]
The supplied claim text does not identify the exact formula drawings or list baloxavir by name. A definitive infringement analysis therefore requires a structure-by-structure comparison between baloxavir, baloxavir marboxil and the issued claims.
The legal analysis would examine:
- Whether baloxavir or its active metabolite falls within the claimed formula.
- Whether the prodrug is covered directly or through a salt, solvate or related compound limitation.
- Whether the approved product satisfies claim 22 as a pharmaceutical composition.
- Whether the approved influenza indication satisfies claim 23.
- Whether prosecution amendments narrowed the claims in a way that affects the product mapping.
Claim 23 is potentially significant for generic litigation because it covers administering a claimed compound to treat influenza. A generic product labeled for the same patented indication could create method-of-use exposure even if the generic sponsor challenges the composition claims.
When does US Patent 8,927,710 lose exclusivity?
The expected expiration date is approximately February 8, 2030, based on the earliest claimed priority date and the standard 20-year term for applications filed after June 8, 1995. [1, 3]
| Milestone |
Date or period |
| Earliest priority |
Approximately February 8, 2010 |
| US patent application |
Filed before issuance; continuation or national-stage details require the USPTO record |
| Patent issuance |
January 6, 2015 |
| Expected base expiration |
Approximately February 8, 2030 |
| Possible adjustment |
Patent-term adjustment may alter the calculated expiration |
| Regulatory exclusivity |
Separate from patent term and governed by FDA approval and product status |
Patent expiration does not necessarily equal market entry. A generic applicant may obtain approval before expiration with a launch date controlled by litigation, settlement, regulatory approval timing and any other listed patents.
What is the Orange Book status of Patent 8,927,710?
The patent is relevant to the Orange Book analysis for Xofluza, but the listing question must be assessed against the current FDA Approved Drug Products with Therapeutic Equivalence Evaluations database and the NDA-specific patent listing. FDA Orange Book listings identify patents submitted by an NDA holder and do not independently determine infringement or validity. [4]
The relevant categories are:
- Active-ingredient patents;
- Drug-product patents;
- Method-of-use patents;
- Formulation or delivery-system patents.
Patent 8,927,710 is principally a compound and method patent based on the supplied claims. Claim 22 provides composition coverage, but it does not appear to require a specialized formulation, release profile, dosage form or excipient combination. Claim 23 is a method-of-use claim directed to influenza treatment.
A patent may be listed in the Orange Book even when only certain claims correspond to the approved product. Conversely, a broad research patent may be commercially relevant without being listed against every dosage form or indication.
What formulation patents protect Xofluza?
Patent 8,927,710 does not appear, from the supplied claims, to be a dedicated formulation patent. Claim 22 covers a pharmaceutical composition containing a claimed compound, pharmaceutically acceptable salt or solvate, and a pharmaceutically acceptable carrier or diluent.
That language is broad. It can reach tablets, capsules, powders, suspensions or other conventional dosage forms if the composition contains a covered compound. It does not specifically require:
- A particular particle size;
- A defined polymorph;
- A solid dispersion;
- A specific salt ratio;
- A controlled-release matrix;
- A particular coating;
- A defined dissolution profile; or
- A named excipient combination.
Separate Xofluza patents may protect the prodrug, solid-state form, formulation, dosage regimen or manufacturing process. Those patents must be analyzed independently because they can extend commercial protection beyond the expiration of a broad chemical genus.
What method-of-use protection does the patent provide?
Claim 23 covers a method of treating influenza infectious disease by administering a compound of claims 9-21, or its salt or solvate.
The claim is narrower than a general antiviral-use claim because it incorporates the compound limitations of claims 9-21. It does not, based on the supplied text, require:
- Influenza A rather than influenza B;
- A particular viral strain;
- Administration within a specified number of hours;
- A single-dose regimen;
- Pediatric or adult dosing;
- Prophylaxis;
- Reduction of viral load;
- Prevention of transmission; or
- Combination treatment.
The broad disease language may cover multiple influenza indications if the administered compound falls within claims 9-21. It does not automatically cover every antiviral use of baloxavir or every use of an unclaimed analog.
How strong is the patent estate?
The patent has strong formal breadth but its enforceable value depends on validity and product mapping.
| Issue |
Assessment |
| Chemical breadth |
High on the face of claims 1 and 9 because of extensive Markush definitions |
| Fallback positions |
Substantial, with claims narrowing R1/R1a, R2/R2a, R3/R3a and the ring arrangement |
| Product coverage |
Potentially important for the Shionogi CAP-endonuclease program, but requires formula-level mapping |
| Formulation protection |
Limited in the supplied claims |
| Method protection |
Direct influenza-treatment claim in claim 23 |
| Prior-art exposure |
Potentially significant because broad heterocyclic antiviral genera can face novelty and obviousness challenges |
| Design-around risk |
Material if a competing compound changes the core ring arrangement or substituent relationship |
| Manufacturing protection |
Not present in the supplied claims |
The most valuable claims are likely the narrower composition-of-matter claims that correspond to specific development compounds. Broad genus claims can be challenged under 35 U.S.C. §§ 102 and 103, while enablement and written-description issues may arise if the claim scope materially exceeds the examples and demonstrated compounds. [5]
Which companies are challenging the patent?
No active Paragraph IV challenge or published US litigation record should be treated as established solely from the supplied claim text. A reliable challenge analysis requires matching the patent to:
- The current Orange Book listing;
- FDA Paragraph IV notice information;
- PACER litigation records;
- ANDA-related district-court complaints;
- Any inter partes review petition or final written decision.
A Paragraph IV certification against Patent 8,927,710 would assert that the patent is invalid, unenforceable or not infringed. A generic applicant could also file a section viii statement carving out a patented method of use, although that route would not avoid composition-of-matter claims covering the active ingredient.
What generic launch scenarios exist?
Three launch scenarios are commercially relevant.
Launch after patent expiration
A generic applicant may launch after the patent expires, assuming no other listed patent or regulatory exclusivity blocks approval. Under the base calculation, that date would fall around February 2030.
At-risk launch
A sponsor may launch before expiration after receiving FDA approval and accepting the risk of infringement litigation. This strategy is less likely where the patent estate includes a strong active-ingredient claim and the product depends on the same compound.
Settlement or license launch
A patent settlement could establish a licensed entry date earlier than the nominal expiration date. The agreement could include restrictions on dosage forms, indications, authorized generic supply or manufacturing sources. No settlement terms should be inferred without a filed agreement or court record.
How does this patent compare with competing influenza antiviral patents?
Patent 8,927,710 is materially different from patents covering older influenza products.
| Product or class |
Primary target |
Typical patent focus |
| Xofluza, baloxavir |
CAP-dependent endonuclease |
Novel chemical compounds, prodrug, composition and influenza use |
| Tamiflu, oseltamivir |
Neuraminidase |
Active ingredient, stereochemistry, process and formulations |
| Relenza, zanamivir |
Neuraminidase |
Active ingredient, inhalation delivery and formulation |
| Rapivab, peramivir |
Neuraminidase |
Active ingredient and injectable formulation |
| Pimodivir development program |
PB2 polymerase |
Distinct target and compound series |
Baloxavir’s target-specific patent position reduces direct overlap with neuraminidase inhibitors. Competitive risk comes from alternative mechanisms, next-generation endonuclease inhibitors and compounds that preserve antiviral activity while avoiding the claimed scaffold.
Key Takeaways
- Patent 8,927,710 covers broad CAP-dependent endonuclease inhibitor genera, related salts and solvates.
- Claims 1-8 and 9-21 use extensive Markush definitions with multiple fallback limitations.
- Claim 22 covers pharmaceutical compositions containing compounds from claims 9-21.
- Claim 23 covers treatment of influenza infectious disease with those compounds.
- The patent is associated with Shionogi’s baloxavir/Xofluza intellectual-property program.
- The expected base expiration is approximately February 8, 2030, subject to USPTO term adjustments and other patent-term records.
- The patent is not a dedicated formulation or manufacturing patent based on the claims supplied.
- Exact baloxavir coverage cannot be confirmed without the omitted structural formula and the issued patent’s prosecution record.
- Generic entry depends on the full Orange Book estate, not Patent 8,927,710 alone.
FAQs About US Patent 8,927,710
Is US Patent 8,927,710 a baloxavir patent?
It is associated with Shionogi’s CAP-dependent endonuclease inhibitor program and is relevant to baloxavir, but exact coverage requires comparing baloxavir’s structure with the patent’s omitted formula drawings and issued claim construction.
Does Patent 8,927,710 cover baloxavir marboxil?
The supplied claims do not identify baloxavir marboxil by name. Coverage depends on whether the prodrug falls within the claimed compound genus or is covered through a related product patent.
Can a generic launch before February 2030?
A generic could potentially launch before the expected expiration through a successful Paragraph IV challenge, a settlement license, a noninfringing product strategy or an at-risk launch. Other Xofluza patents and regulatory exclusivities must also be evaluated.
Does claim 23 cover influenza prophylaxis?
The supplied wording covers treatment of influenza infectious disease. It does not expressly recite post-exposure prophylaxis or prevention, so prophylaxis coverage depends on claim construction and whether other patent claims separately address that use.
Is Patent 8,927,710 a formulation patent?
Primarily no. Claim 22 covers a composition containing a claimed compound and a pharmaceutically acceptable carrier or diluent, but it does not require a specialized formulation architecture.
References
- United States Patent No. 8,927,710, “CAP-dependent endonuclease inhibitor.” U.S. Patent and Trademark Office.
- U.S. Food and Drug Administration. (2018). FDA approves new drug to treat influenza.
- 35 U.S.C. § 154. Patent term.
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
- 35 U.S.C. §§ 102, 103, 112. Patentability, obviousness and disclosure requirements.
