United States Patent 8,664,231: Scope, Claims, Expiration, Orange Book Status, and Methotrexate Patent Landscape
U.S. Patent No. 8,664,231 protects a method of treating inflammatory autoimmune disease with a subcutaneous methotrexate product containing more than 30 mg/mL methotrexate. The patent is directed primarily to high-concentration injectable methotrexate, self-administration, and injection-device presentations. It does not claim methotrexate as a compound, methotrexate generally, oral methotrexate, or every injectable methotrexate product.
The patent was assigned to medac Gesellschaft für klinische Spezialpräparate mbH and has a nominal expiration date of March 7, 2028, based on the reported priority and patent-term data. It is associated with the U.S. Rasuvo methotrexate injection franchise and has commercial significance for generic or competing injectable products using concentrations above 30 mg/mL.
What does U.S. Patent 8,664,231 protect?
The independent claim requires all of the following elements:
- Treatment of an inflammatory autoimmune disease.
- A patient in need of treatment.
- Subcutaneous administration.
- A medicament containing methotrexate.
- Methotrexate concentration above 30 mg/mL.
- A pharmaceutically acceptable solvent.
The core legal concept is a treatment-method claim, not a composition claim. A product is not necessarily infringing merely because it contains methotrexate at 50 mg/mL. Infringement generally requires use of the product in a manner that satisfies the claimed treatment and administration limitations.
| Claim element |
Scope |
| Active ingredient |
Methotrexate |
| Route |
Subcutaneous administration |
| Concentration |
More than 30 mg/mL |
| Solvent |
Broadly, a pharmaceutically acceptable solvent |
| Disease |
Inflammatory autoimmune diseases |
| Product format |
Broad in claim 1; devices and containers are addressed in dependent claims |
| Patient use |
Treatment of a patient in need |
| Geographic reach |
United States only |
The threshold is “more than 30 mg/mL.” A product at exactly 30 mg/mL is outside the literal concentration range of claim 1. Concentrations of 30.1 mg/mL, 40 mg/mL, 50 mg/mL, and 100 mg/mL fall within the express scope of the claims, subject to ordinary claim-construction principles.
How do the dependent claims narrow the patent scope?
The dependent claims create several protected subcategories.
Concentration limitations
Claims 2, 3, and 22 narrow the concentration range:
- Claim 2: more than 30 mg/mL to 100 mg/mL.
- Claim 3: approximately 50 mg/mL.
- Claim 22: 40 mg/mL to 80 mg/mL.
Claim 3 is commercially important because it maps directly onto a 50 mg/mL injectable presentation. Claim 22 creates a separate range that captures many commercially practical high-concentration formulations while excluding concentrations below 40 mg/mL and above 80 mg/mL.
The “about 50 mg/mL” language may allow some variation around 50 mg/mL, depending on the specification, prosecution history, and ordinary pharmaceutical measurement tolerances. The broader claim 1 remains the principal risk provision for concentrations between 30 mg/mL and 40 mg/mL and above 80 mg/mL.
Solvent limitations
Claims 4 and 17 specify:
- Water.
- Water for injection.
- Water containing isotonization additives.
- Sodium chloride solution.
- Isotonic sodium chloride solution.
These claims are narrower than claim 1. A formulation using water for injection may fall within claims 4 and 17, but the solvent limitation is not required by claim 1 beyond the general requirement for a pharmaceutically acceptable solvent.
Disease limitations
Claim 5 lists the covered diseases, including:
- Rheumatoid arthritis.
- Juvenile arthritides.
- Vasculitides.
- Collagenoses.
- Crohn’s disease.
- Ulcerative colitis.
- Bronchial asthma.
- Alzheimer’s disease.
- Multiple sclerosis.
- Bechterew’s disease.
- Joint arthroses.
- Psoriasis.
Claim 6 narrows the indication to rheumatoid arthritis. Claim 18 further limits it to juvenile rheumatoid arthritis.
The disease list creates both breadth and vulnerability. It extends beyond the conventional rheumatoid arthritis market, but a challenger could argue that the specification does not adequately support or enable every listed disease, particularly disease categories for which high-concentration subcutaneous methotrexate was not clinically established at the relevant filing date.
Device and packaging limitations
Claims 7 through 21 cover product configurations designed for self-administration:
- Patient self-administration.
- Single-use injection devices.
- Ready-made syringes.
- Vials.
- Injection bottles.
- Bags.
- Glass ampoules.
- Carpules.
- Pen injectors.
- Multiple applications from a carpule.
- Adjustable doses from 5 mg to 40 mg.
Claims 9 and 19 identify specific dose amounts from 5 mg through 40 mg in 2.5 mg increments. Claims 14 through 21 focus on a carpule and pen injector capable of administering multiple adjustable doses.
These limitations are relevant to prefilled syringes and autoinjector or pen-based products. They do not mean that every product in a listed container infringes. The product must be used in the claimed subcutaneous method, and the specific container or dose limitation must be satisfied for the dependent claim to apply.
What is the patent’s priority, filing, grant, and expiration timeline?
| Event |
Date or status |
| Earliest reported priority |
March 7, 2007 |
| International/PCT filing |
March 7, 2008 |
| U.S. national-stage filing |
2012 |
| U.S. patent grant |
March 4, 2014 |
| Patent number |
U.S. 8,664,231 |
| Nominal expiration |
March 7, 2028 |
| Patent type |
Utility patent |
| Patent status |
Reported active, subject to USPTO maintenance and term records |
The patent term is generally measured from the earliest effective nonprovisional filing date, with international applications entering the U.S. national stage treated under the applicable Patent Cooperation Treaty rules. The reported March 7, 2028 expiration date should be checked against the current USPTO patent-term adjustment record and any terminal disclaimer information before relying on it for a launch decision. (United States Patent and Trademark Office, n.d.-a)
What is the Orange Book status of U.S. Patent 8,664,231?
U.S. Patent 8,664,231 has been associated with Rasuvo, the medac methotrexate injection product approved by the FDA. Rasuvo is a subcutaneous methotrexate product supplied in multiple strengths for once-weekly administration in rheumatoid arthritis, polyarticular juvenile idiopathic arthritis, and psoriasis. (U.S. Food and Drug Administration, 2014)
The Orange Book listing is commercially relevant because an ANDA applicant seeking approval for a product referencing Rasuvo must address listed patents through the applicable certification pathway. A Paragraph IV certification would assert that the listed patent is invalid, unenforceable, or will not be infringed by the proposed ANDA product. The reference product sponsor may then bring patent litigation within the statutory period, triggering the potential 30-month stay under the Hatch-Waxman framework. (U.S. Food and Drug Administration, n.d.)
Orange Book listing does not establish validity or infringement. It identifies patents that the NDA holder or patent owner has submitted for the listed drug. The scope of the listed patent must still be compared with the proposed label, formulation, device, concentration, and use instructions.
When does U.S. Patent 8,664,231 lose exclusivity?
The reported nominal expiration date is March 7, 2028. Commercial exclusivity may end earlier if the patent is invalidated, disclaimed, canceled in post-grant proceedings, or rendered noninfringed by a competing label or product configuration.
The practical loss-of-exclusivity date depends on the competing product:
- A low-concentration methotrexate injection at 25 mg/mL would not meet the express concentration threshold.
- A product at more than 30 mg/mL used subcutaneously for a listed disease presents a direct claim risk.
- A product labeled only for a nonclaimed indication may reduce method-of-use exposure, but label design must avoid inducing the patented use.
- A product with a different route, such as intramuscular or intravenous administration, does not satisfy the subcutaneous limitation.
- A product containing 30 mg/mL or less may avoid literal infringement of the central concentration limitation.
Which companies are challenging the patent?
Publicly available sources identify the patent as part of the Rasuvo patent estate, but the supplied record does not establish a complete list of Paragraph IV filers, litigation defendants, settlements, or launch dates. The patent record alone does not prove that a particular generic company has challenged U.S. Patent 8,664,231.
The principal potential challengers are manufacturers developing:
- High-concentration subcutaneous methotrexate.
- Prefilled methotrexate syringes.
- Methotrexate pen injectors.
- Carpule-based delivery systems.
- ANDA products referencing Rasuvo.
- 505(b)(2) products with differentiated devices or dosing presentations.
A reliable challenger analysis requires matching each FDA filing or litigation docket to the specific patent and use code. A general statement that generic competition exists is not sufficient to establish a Paragraph IV challenge.
What invalidity and noninfringement arguments apply?
The principal legal pressure points are obviousness, written description, enablement, claim construction, and divided infringement.
Obviousness
A challenger could combine prior-art methotrexate injections, known subcutaneous administration, and known concentration or dosing practices. The patent owner would likely rely on the asserted benefits of higher concentration, reduced injection volume, improved patient convenience, and self-administration.
The strongest obviousness defense would identify prior art teaching:
- Subcutaneous methotrexate for autoimmune disease.
- Concentrations above 30 mg/mL.
- Doses in the 5 mg to 40 mg range.
- Prefilled syringes or pen devices.
- Weekly dosing and patient self-administration.
The patent’s defense would depend on whether the prior art gave a reason to select the claimed concentration and whether the claimed formulation produced unexpected clinical or usability advantages.
Written description and enablement
Claim 1 covers inflammatory autoimmune diseases broadly, while claim 5 lists numerous conditions. A challenger could argue that the specification does not support the full disease scope or enable treatment across every listed condition without undue experimentation.
The broad concentration range also creates a potential enablement issue if the specification provides meaningful support only for particular concentrations, solvents, doses, or devices.
Noninfringement
Potential design-arounds include:
- Concentrations at or below 30 mg/mL.
- A route other than subcutaneous administration.
- A label omitting the patented indications.
- A product not supplied for self-administration.
- A single-dose presentation that avoids device limitations.
- A formulation using a concentration outside dependent-claim ranges.
These strategies do not automatically eliminate risk under claim 1, which is broader than the device and solvent claims.
Induced infringement
Even if a manufacturer does not itself administer methotrexate, it may face induced-infringement allegations if its label, promotional material, instructions, or device design encourages physicians or patients to practice the patented method. Label carve-outs must be evaluated against the actual commercial use of the product.
What manufacturing and formulation barriers does the patent create?
The patent does not claim methotrexate manufacturing generally. It creates a narrower barrier around a high-concentration subcutaneous product used for the claimed diseases.
Technical development risks include:
- Methotrexate solubility at concentrations above 30 mg/mL.
- Chemical and physical stability during storage.
- pH control.
- Precipitation and crystallization.
- Compatibility with syringes, cartridges, and pen components.
- Extractables and leachables.
- Accurate low-volume dose delivery.
- Injection-site tolerability.
- Container closure integrity.
- Sterility assurance for injectable products.
A competitor may design around the patent but still face separate formulation, device, regulatory, or trade-secret barriers. The patent does not, by itself, establish exclusivity over every high-concentration methotrexate formulation.
How does this patent compare with competing methotrexate products?
| Product type |
Typical patent risk under 8,664,231 |
Main reason |
| Oral methotrexate tablets |
Low |
No subcutaneous administration |
| Low-concentration injectable methotrexate |
Low to moderate |
May fall at or below 30 mg/mL |
| High-concentration subcutaneous methotrexate |
High |
Core claim elements align |
| Prefilled high-concentration syringe |
High |
May satisfy claims 7-10 and 19 |
| Pen injector with carpule |
High |
May satisfy claims 14-21 |
| Intramuscular methotrexate |
Lower under this patent |
Route limitation differs |
| Intravenous methotrexate |
Lower under this patent |
Route limitation differs |
| High-concentration product for unlisted use |
Moderate |
Label and induced-use analysis required |
The patent is narrower than a composition patent but more commercially targeted than a generic method-of-treatment claim. Its strongest commercial position is against a subcutaneous, high-concentration, patient-administered product modeled on Rasuvo.
What is the biosimilar risk?
There is no conventional biosimilar pathway for methotrexate because methotrexate is a small-molecule active ingredient rather than a biologic. Competitive products would generally proceed through an ANDA under section 505(j) or, depending on formulation and device differences, a 505(b)(2) application.
The principal regulatory and patent risks are therefore generic-drug risks, not biosimilar risks:
- Paragraph IV certification.
- Orange Book patent litigation.
- Labeling carve-outs.
- Device sameness or substitutability issues.
- Demonstration of injectable product quality and bioequivalence.
- Manufacturing scale-up and sterile-filling capacity.
What licensing deals affect the patent?
The identified public patent and FDA materials establish medac’s ownership and product relationship but do not establish a separate public license or co-development agreement specifically covering U.S. Patent 8,664,231. Any private license, supply arrangement, or settlement would require review of the relevant SEC filings, court docket, FDA correspondence, or transaction announcement.
Key Takeaways
- U.S. Patent 8,664,231 is a method patent covering subcutaneous administration of methotrexate at concentrations above 30 mg/mL.
- The patent’s commercial center is high-concentration, self-administered methotrexate, including prefilled syringes and pen injectors.
- Claim 1 is broad because it does not require a specific disease, solvent, container, or device beyond subcutaneous administration and the concentration threshold.
- Claims 3 and 22 are particularly relevant to products at approximately 50 mg/mL and 40-80 mg/mL.
- The patent does not cover oral methotrexate, methotrexate as a chemical compound, or every injectable methotrexate product.
- The reported nominal expiration date is March 7, 2028.
- Rasuvo is the principal FDA-linked commercial product associated with the patent.
- Generic risk is highest for a subcutaneous product above 30 mg/mL with a rheumatoid arthritis or psoriasis label.
- Methotrexate has generic-drug competition risk, not conventional biosimilar risk.
- The principal legal challenges are obviousness, enablement, written description, claim construction, and induced infringement.
FAQs About U.S. Patent 8,664,231
Does U.S. Patent 8,664,231 cover methotrexate at exactly 30 mg/mL?
Not literally under the stated concentration limitation. The claims require a concentration of more than 30 mg/mL. A 30 mg/mL product may still require analysis of other patents, labeling, and potential equivalents arguments.
Does the patent cover oral methotrexate tablets?
No. The claims require subcutaneous administration. Oral tablets do not satisfy that route limitation.
Does the patent cover a 50 mg/mL methotrexate formulation?
It can cover the use of that formulation when administered subcutaneously to treat a claimed inflammatory autoimmune disease. Claim 3 specifically recites approximately 50 mg/mL.
Can a generic company avoid the patent by using a vial instead of a prefilled syringe?
A vial may avoid syringe-specific dependent claims, but it does not avoid claim 1 if the product is used subcutaneously, contains more than 30 mg/mL methotrexate, and treats a covered disease.
Is a methotrexate pen injector protected independently of the drug formulation?
The cited claims protect the method using the pen injector and specified dosing configuration. They do not create a standalone device patent covering every methotrexate pen injector or every pen used with another drug.
What is the most important design-around route?
The clearest literal design-around is a product at 30 mg/mL or less, or a product administered by a route other than subcutaneous injection. A label-based design-around requires a separate analysis of actual use and induced infringement.
Sources:
- U.S. Food and Drug Administration. (2014). Rasuvo (methotrexate) injection prescribing information.
- U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book.
- U.S. Patent and Trademark Office. (n.d.-a). Patent Center and patent-term information for U.S. Patent No. 8,664,231.
- U.S. Patent and Trademark Office. (n.d.-b). U.S. Patent No. 8,664,231, Method for treatment of inflammatory autoimmune diseases.
- U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.
