US Patent 7,754,731: Raltegravir Potassium Crystal, Formulation, Manufacturing and HIV-Treatment Patent Analysis
US Patent 7,754,731 protects an anhydrous crystalline potassium salt of raltegravir, the active ingredient in Merck's Isentress and Isentress HD products. Its strongest claims are directed to the specific crystalline form identified by XRPD peaks at 5.9°, 20.0° and 20.6° 2θ, with optional additional peaks at 12.5° and 25.6°, and a DSC endotherm at approximately 279°C. The patent also covers pharmaceutical compositions, HIV-treatment methods and multiple crystallization processes.
The product claims are narrow but commercially important. A competing manufacturer that makes, sells or uses the claimed raltegravir potassium form may face direct infringement exposure even if it uses a different tablet formulation. Process claims create a separate risk for manufacturers using potassium-base crystallization, acetonitrile/ethanol solvent systems, seeded crystallization or concurrent-feed manufacturing.
What drug does US Patent 7,754,731 protect?
US 7,754,731 protects raltegravir potassium in a defined anhydrous crystalline form. Raltegravir is an HIV-1 integrase strand-transfer inhibitor developed by Merck & Co., Inc. The potassium salt is used in Isentress tablets, chewable tablets and oral suspension products.
The patent's Compound A is raltegravir, and the claimed material is its monopotassium salt. The patent is primarily a solid-state and manufacturing patent rather than a basic composition-of-matter patent covering raltegravir itself.
| Item |
Description |
| Active ingredient |
Raltegravir |
| Salt |
Potassium salt, principally monopotassium raltegravir |
| Product |
Anhydrous crystalline raltegravir potassium |
| Originator |
Merck & Co., Inc. |
| Brand products |
Isentress and Isentress HD |
| Therapeutic category |
HIV-1 integrase strand-transfer inhibitor |
| Main technical subject |
Crystal form and crystallization processes |
| Patent |
US 7,754,731 B2 |
| Grant date |
July 13, 2010 |
| Listed inventorship/ownership |
Merck-affiliated entities |
| Primary jurisdiction |
United States |
Raltegravir binds HIV integrase and inhibits integration of viral DNA into the host-cell genome. The patent does not claim every raltegravir salt, every polymorph or every dosage form. Its central limitation is the particular anhydrous crystalline potassium salt.
What are the strongest claims in US 7,754,731?
Claims 1 through 5 are the core product claims. Claim 1 requires an anhydrous crystalline potassium salt of raltegravir characterized by three XRPD reflections:
- 5.9° 2θ
- 20.0° 2θ
- 20.6° 2θ
Claims 3 and 4 add two further reflections:
Claims 2 and 4 add a DSC limitation requiring a single endothermic peak at approximately 279°C under the stated test conditions.
| Claim group |
Subject matter |
Commercial significance |
| Claims 1-5 |
Defined anhydrous crystalline potassium salt |
Strongest direct product protection |
| Claims 6-7 |
Pharmaceutical compositions containing the claimed salt |
Covers drug-product incorporation |
| Claim 8 |
Treatment of HIV infection, AIDS or delayed AIDS onset |
Method-of-use protection |
| Claims 9-13 |
Seeded crystallization using aqueous potassium base or organic solvent |
Broad process coverage |
| Claims 14-16 |
Concurrent-feed crystallization using potassium alkoxide |
Commercial-scale process protection |
| Claims 17-23 |
Concurrent crystallization using KOH and water-dissolving organic solvent |
Alternative process coverage |
The product claims are identity claims. Infringement normally turns on whether the accused material has the claimed crystal form, not on whether the manufacturer copied Merck's manufacturing instructions.
How narrow are the XRPD and DSC limitations?
The XRPD limitations materially narrow the product claims. A salt that has the same chemical formula but is amorphous, hydrated, solvated or a different polymorph may fall outside claims 1 through 5.
Claim 1 is broader than claims 3 and 4 because it requires only three specified XRPD peaks. Claim 3 requires five peaks. Claim 2 adds the DSC peak to the claim 1 form. Claim 4 adds the DSC peak to the more specifically identified claim 3 form.
The following distinctions are important:
| Material characteristic |
Likely relationship to claims 1-5 |
| Anhydrous crystalline monopotassium raltegravir with required peaks |
Within the central claim scope |
| Same salt with only a different polymorph |
Potentially outside product claims |
| Hydrated or solvated potassium salt |
Potentially outside the express anhydrous limitation |
| Amorphous raltegravir potassium |
Outside the crystalline-form claims |
| Sodium, calcium or other raltegravir salt |
Outside the potassium-salt limitation |
| Raltegravir free acid |
Outside the potassium-salt limitation |
| Same XRPD form but DSC peak shifted materially |
May affect claims 2 and 4, but not necessarily claims 1 and 3 |
| Same chemical form produced by a different process |
May still infringe claims 1-5 |
XRPD peak positions are subject to instrument configuration, sample preparation and measurement conditions. A technical infringement analysis would compare the accused batch against the patent's claimed pattern using validated powder-diffraction methods. The claim does not require every possible diffraction peak. It requires a pattern that comprises the listed values.
What formulations are protected by US 7,754,731?
Claims 6 and 7 cover pharmaceutical compositions containing an effective amount of the claimed potassium salt and a pharmaceutically acceptable carrier. These claims are written broadly and do not require a particular tablet excipient, dosage strength, release profile or route of administration.
Potentially covered dosage forms include:
- Immediate-release tablets
- Film-coated tablets
- Chewable tablets
- Oral suspensions
- Powder or granule formulations
- Other pharmaceutical compositions containing the claimed crystalline salt
Claim 7 uses product-by-process language, covering the product made by combining the claimed salt with a pharmaceutically acceptable carrier. The absence of a detailed excipient list gives the claims broad formulation reach, but the composition must still contain the specific claimed potassium salt.
Claims 6 and 7 do not necessarily cover a formulation containing a different raltegravir polymorph, an amorphous salt or a non-potassium salt. The formulation claims inherit the critical identity of the claimed active ingredient.
What method-of-use protection does the patent provide?
Claim 8 covers administering an effective amount of the claimed potassium salt to a subject for:
- Treating HIV infection
- Delaying the onset of AIDS
- Treating AIDS
The method claim is broad as to patient population and dosing regimen. It does not specify a particular combination partner, treatment line, dose or duration. The required technical limitation remains the administration of the claimed crystalline potassium salt.
For a generic product, method-of-use risk depends on the approved label, marketing conduct and the scope of any remaining use claims. A manufacturer may reduce risk for unprotected indications through a section viii carve-out, but a carve-out does not eliminate product-form or composition-of-matter exposure.
How broad are the manufacturing claims?
The manufacturing claims cover seeded crystallization approaches designed to produce the claimed crystalline potassium salt.
Claims 9 through 13: aqueous potassium base and organic solvent routes
These claims cover two principal routes.
The first route mixes an aqueous potassium base with raltegravir, water and alcohol, followed by seeding, optional alcohol dilution and ageing. Claim 10 narrows the route to KOH and ethanol. Claim 11 adds operating parameters:
- 20°C to 30°C for initial dissolution and seeding
- 0°C to 20°C for ageing
- Initial ethanol-to-water ratio of approximately 70:30 to 30:70
- Final ethanol-to-water ratio of at least approximately 80:20
- Seed loading of approximately 1% to 5% by weight
- KOH at approximately 0.9 to 1.1 equivalents
The second route seeds raltegravir in an organic solvent, adds aqueous potassium base and ages the resulting mixture. Claim 12 identifies acetonitrile, while claim 13 adds:
- 20°C to 30°C for seeding and base addition
- 20°C to 30°C for ageing
- Acetonitrile-to-water ratio of at least approximately 90:10
- Seed loading of approximately 1% to 5%
- KOH at approximately 0.9 to 1.1 equivalents
Claims 14 through 16: concurrent-feed potassium alkoxide process
Claim 14 covers adding two feeds concurrently to a crystallizer containing seed crystals:
- A raltegravir solution containing a first solvent and a second solvent.
- A potassium alkoxide solution in the second solvent.
Claim 15 narrows the system to raltegravir in acetonitrile and ethanol, with potassium ethoxide in ethanol. Claim 16 adds:
- Potassium ethoxide at approximately 0.9 to 1.1 equivalents
- Addition at approximately 20°C to 30°C
- Initial ageing at approximately 30°C to 40°C
- Subsequent ageing at approximately 20°C to 30°C
- Seed loading of approximately 10% to 25%
- Final acetonitrile-to-ethanol ratio of approximately 80:20 to 20:80
These claims are directed toward controlled, scalable crystallization rather than laboratory preparation alone.
Claim 17: concurrent-feed KOH process
Claim 17 covers concurrent addition of:
- A raltegravir solution in a water-dissolving organic solvent
- A KOH solution in water
The feeds enter a crystallizer containing seed crystals in an organic-solvent/water mixture. The claim is broader than claim 15 as to specific solvent identity and does not include all of the detailed operating parameters in claim 16.
Claims 18 through 23: dependent process limitations
These claims expand the process coverage by identifying acceptable potassium bases, base equivalents, temperature ranges and solvent ratios. Claim 18 includes potassium hydroxide, potassium carbonate, potassium bicarbonate and potassium alkoxides. Claim 19 covers approximately 0.1 to 3 equivalents of potassium base. Claim 20 covers 0°C to 60°C for specified process steps.
A process using a different base, no seeding, a different solvent system or a different crystallization sequence may avoid individual process claims. That does not avoid the product claims if the resulting material is the claimed anhydrous crystalline form.
When does US Patent 7,754,731 lose exclusivity?
The patent's ordinary 20-year term is measured from the earliest effective nonprovisional filing date, subject to patent-term adjustment and any applicable patent-term extension. The relevant priority history, USPTO term calculation and Orange Book listing control the operative expiration date.
Because US 7,754,731 concerns raltegravir potassium, its commercial exclusivity must be analyzed with the related raltegravir patent family rather than in isolation. The basic raltegravir patents, crystalline-form patents, formulation patents and pediatric exclusivity periods can create different end dates.
| Exclusivity layer |
Relevance |
| Basic raltegravir patent |
Protects the active pharmaceutical compound |
| Potassium-salt crystal patent |
Protects the specific commercial solid form |
| Formulation patents |
May cover dosage forms or product configurations |
| Method-of-use patents |
May cover labeled HIV-treatment uses |
| Regulatory exclusivity |
May delay ANDA approval independent of patent term |
| Pediatric exclusivity |
Can add six months to qualifying listed patents |
The patent should not be treated as expired solely because an earlier raltegravir compound patent has expired. A generic entrant must evaluate each unexpired listed patent and each enforceable claim.
What is the Orange Book status of the patent?
The Food and Drug Administration's Orange Book determines whether US 7,754,731 is listed against a particular raltegravir reference product and whether an ANDA applicant must address it in a certification. The relevant listing may differ between Isentress dosage forms and Isentress HD presentations.
For an ANDA referencing a listed product, the applicant generally must submit one of the following certifications for each listed patent:
- Paragraph I: no patent information has been submitted
- Paragraph II: the patent has expired
- Paragraph III: approval is sought after patent expiration
- Paragraph IV: the patent is invalid, unenforceable or will not be infringed
The patent's Orange Book status must be checked against the current FDA listing and the specific reference listed drug. A patent can remain legally relevant even where an individual dosage form has been discontinued, provided the listing and statutory requirements remain applicable.
Which companies are challenging raltegravir patent rights?
Raltegravir generic competition has involved ANDA applicants seeking approval for tablets and other dosage forms. Public patent litigation and settlement information must be analyzed by defendant, product strength, dosage form and patent number. A Paragraph IV filing against a basic raltegravir patent does not automatically resolve risk under US 7,754,731.
The principal competitive groups are:
- Merck, as originator and patent holder
- Generic manufacturers filing ANDAs for raltegravir potassium
- Contract manufacturers supplying active ingredient or finished dosage forms
- Potential suppliers of alternative polymorphs or non-infringing salt forms
A settlement agreement can permit an authorized or licensed generic launch before patent expiry while restricting independent generic entry. The commercial effect depends on the entry date, royalty structure, supply terms, exclusivity provisions and whether the settlement covers all asserted patents.
No conclusion about a particular company's launch rights should be drawn from an ANDA filing alone. The operative documents are the complaint, answer, claim-construction record, settlement agreement and FDA approval status.
How strong is the patent estate for raltegravir potassium?
US 7,754,731 has a mixed-strength profile.
Strengths
- Claims a defined commercial crystal form rather than an abstract formulation concept.
- Includes both product claims and manufacturing claims.
- Uses objective analytical characteristics, including XRPD and DSC.
- Covers several process families, including KOH, potassium alkoxide, ethanol and acetonitrile routes.
- Product claims can apply regardless of whether a competitor copies the patented process.
Vulnerabilities
- Product claims depend on proving the precise crystalline form.
- XRPD and DSC results can vary with testing conditions.
- An alternative polymorph, hydrate or amorphous material may avoid the express product limitations.
- Process claims are vulnerable to process redesign.
- Method claims may be narrowed by label language or indication carve-outs.
- Some process claims use functional or relative terms such as "substantial portion," "about" and "ageing," which may create claim-construction disputes.
The strongest enforcement position is likely against a supplier whose raltegravir potassium active ingredient matches the claimed XRPD pattern. The main technical dispute would concern whether the accused material is the claimed anhydrous form and whether the measured peaks satisfy the claim limitations.
What generic launch risks exist?
A generic entrant faces four principal risk categories.
| Risk |
Exposure |
| Active pharmaceutical ingredient |
Manufacture or purchase of the claimed crystal form |
| Finished product |
Composition claims 6 and 7 |
| Label and marketing |
Method claim 8 |
| Manufacturing route |
Claims 9-23 |
A non-infringing strategy could involve a different solid form, a different salt, an amorphous material or a crystallization process outside the claimed limitations. Each strategy carries regulatory and pharmaceutical-development risks. A form that avoids the patent may have inferior stability, dissolution, bioavailability, manufacturability or shelf life.
The most practical freedom-to-operate analysis requires batch-level characterization of the proposed API, process mapping against claims 9-23 and a review of all other raltegravir patents still in force.
How does US 7,754,731 compare with basic raltegravir patents?
The patent has a narrower technical scope than a basic compound patent but may be more closely aligned with the commercial API.
| Patent type |
Typical protected subject matter |
Design-around potential |
| Basic compound patent |
Raltegravir molecule and broad therapeutic use |
Low before expiry |
| Salt patent |
Potassium or other pharmaceutically acceptable salts |
Moderate |
| Crystal-form patent |
Specific polymorph or anhydrous form |
Higher technically, but commercial constraints apply |
| Formulation patent |
Tablet, suspension, excipient or release profile |
Moderate to high |
| Process patent |
Solvent, seed, temperature and feed sequence |
Often high through process redesign |
| Method-of-use patent |
HIV treatment or dosing regimen |
Label-dependent |
US 7,754,731 is most important where the commercial product uses the claimed crystalline potassium form. It can preserve a barrier after broader compound claims become unavailable, subject to its actual expiration and enforceability.
Key Takeaways
- US 7,754,731 protects an anhydrous crystalline potassium salt of raltegravir.
- Claims 1-5 are the core product claims and rely on specified XRPD peaks, with claims 2 and 4 adding a DSC endotherm at approximately 279°C.
- Claims 6 and 7 cover pharmaceutical compositions containing the claimed crystal form.
- Claim 8 covers HIV, AIDS and delayed-AIDS treatment methods using the salt.
- Claims 9-23 cover seeded and concurrent-feed crystallization processes using KOH, potassium alkoxides, ethanol, acetonitrile and related solvents.
- A different manufacturing process does not avoid product claims if it produces the claimed crystal form.
- A different polymorph, hydrate, solvate or amorphous form may avoid the express product claims, but must be evaluated for pharmaceutical and regulatory suitability.
- Generic-entry analysis requires review of the current Orange Book listing, related raltegravir patents, Paragraph IV litigation and any settlement agreements.
- The patent should be analyzed as part of the full raltegravir patent estate, not as a standalone barrier.
FAQs About US Patent 7,754,731
Does US 7,754,731 cover raltegravir itself?
No. It primarily covers a specified anhydrous crystalline potassium salt of raltegravir, along with compositions, treatment methods and manufacturing processes.
Can a generic avoid the patent by using a different crystallization process?
Only if the resulting API does not meet the product claims or the alternative process falls outside claims 9-23. A different process alone does not avoid claims 1-8 if it produces the claimed crystal form.
Does the patent cover raltegravir sodium?
No. The claims require a potassium salt. A sodium salt is outside that express limitation, although other patents or regulatory issues may apply.
Are amorphous raltegravir potassium products covered?
The express product claims require an anhydrous crystalline form. An amorphous product would generally not satisfy that limitation, but its regulatory, stability and infringement profile requires separate analysis.
What testing is used to assess infringement?
The principal tests are XRPD using copper Kα radiation and DSC under the conditions specified in the claims. Chemical identity, water or solvent content and salt stoichiometry would normally be evaluated with complementary analytical methods.
References
-
Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations (Orange Book). U.S. Department of Health and Human Services.
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Merck & Co., Inc. (2010). US Patent No. 7,754,731 B2: Crystalline potassium salt of raltegravir and processes for its preparation. United States Patent and Trademark Office.
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United States Patent and Trademark Office. (2024). Patent term adjustment and patent term information. U.S. Department of Commerce.
-
National Library of Medicine. (2024). Raltegravir: Drug label information. DailyMed.
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U.S. Food and Drug Administration. (2024). Isentress and Isentress HD prescribing information. U.S. Department of Health and Human Services.
