US Patent 5,527,814: Scope, Claims, Expiration, and Riluzole Patent Landscape

US Patent 5,527,814 covers the use of riluzole, chemically identified as 2-amino-6-(trifluoromethoxy)benzothiazole, for treating amyotrophic lateral sclerosis (ALS). The patent issued on June 18, 1996, and its US patent term expired on June 18, 2013. It does not provide current US exclusivity for riluzole, ALS treatment, riluzole dosage levels, or riluzole products.

The patent is a method-of-treatment patent. It does not claim the riluzole molecule itself, a specific tablet, an oral suspension, an oral film, a manufacturing process, or a particular formulation.

What does US Patent 5,527,814 protect?

The patent protects administering riluzole, or a pharmaceutically acceptable salt, to a mammal with ALS in an amount effective to treat the disease. The principal independent claim is claim 1:

"A method for treating a mammal with amyotrophic lateral sclerosis, comprising the step of administering ... an effective amount of 2-amino-6-(trifluoromethoxy)benzothiazole or a pharmaceutically acceptable salt thereof."

The claimed invention therefore has four central elements:

A mammalian patient.
A patient recognized as needing ALS treatment.
Administration of riluzole or a pharmaceutically acceptable salt.
An amount effective to treat ALS.

The patent does not require a particular brand, route of administration, dosage schedule, tablet strength, treatment duration, or formulation excipient in claim 1.

Patent identification and legal status

Item	Information
US patent	5,527,814
Subject matter	Riluzole treatment of ALS
Chemical name	2-amino-6-(trifluoromethoxy)benzothiazole
Common name	Riluzole
Patent type	Method-of-treatment patent
Issue date	June 18, 1996
Original assignee	Rhône-Poulenc Rorer S.A.
Patent term	17 years from issue for the applicable pre-1995 filing regime
Expiration date	June 18, 2013
Current status	Expired
FDA product associated with the active ingredient	Rilutek
Current US blocking right	None from this patent

The expiration date follows the pre-URAA US patent term applicable to the patent. Because the patent issued before the 20-year-from-earliest-effective-filing-date regime applied to most later-filed applications, its term ran for 17 years from issuance, subject to any applicable adjustment. Public patent records identify the patent as expired in 2013. [1]

How do the individual claims differ?

Claims 2 through 13 narrow claim 1 by specifying disease presentation, dose, or administration context.

Claim	Subject	Scope
1	ALS treatment	Broad method claim covering effective administration of riluzole or a salt
2	Early bulbar involvement	ALS with early bulbar involvement
3	Bulbar form	Bulbar ALS
4	Dose range	25 to 200 mg
5	Specific dose	50 mg
6	Specific dose	25 mg
7	Dose range	50 to 400 mg
8	Specific dose	200 mg
9	Specific dose	400 mg
10	Carrier	Riluzole administered with a pharmaceutically acceptable carrier
11	Compatible product	Riluzole administered with a pharmaceutically compatible product
12	Specific dose	100 mg
13	Salt form	Acid addition salt

What is the broadest claim?

Claim 1 is the broadest claim because it does not impose a stated dose, disease subtype, carrier, or salt requirement. It covers an effective amount of riluzole administered for ALS treatment.

A generic manufacturer marketing riluzole for ALS would have practiced the subject matter of claim 1 during the patent term, even if its product used a different tablet excipient or a different manufacturing process. That infringement theory would have depended on the product labeling and the intended use, not only on the physical composition of the product.

What claims cover riluzole dosage levels?

Claims 4 through 9 and claim 12 cover specified amounts:

25 to 200 mg: claim 4
50 mg: claim 5
25 mg: claim 6
50 to 400 mg: claim 7
200 mg: claim 8
400 mg: claim 9
100 mg: claim 12

The claims contain an apparent drafting overlap. Claim 7 recites 50 to 400 mg, while claims 8 and 9 separately recite 200 mg and 400 mg. Claim 12 depends on claim 4 and recites 100 mg. These dependencies do not expand the scope of claim 1. They create narrower fallback positions within the broader treatment claim.

The 50 mg dosage was commercially significant because the FDA-approved Rilutek tablet was a 50 mg tablet. Current generic riluzole tablets also commonly use the 50 mg strength. [2]

What claims cover bulbar ALS?

Claims 2 and 3 narrow the patient population:

Claim 2 covers ALS with early bulbar involvement.
Claim 3 covers the bulbar form of ALS.

These claims are narrower than claim 1. A treatment falling within claim 2 or claim 3 would ordinarily also fall within claim 1 because each dependent claim incorporates the limitations of claim 1.

The claims do not define "early bulbar involvement" or "bulbar form" with a numerical clinical threshold. Their practical scope would have depended on the medical record, prescribing intent, labeling, and expert interpretation.

Is US Patent 5,527,814 a composition or formulation patent?

No. US 5,527,814 is not a composition-of-matter patent and does not claim a finished riluzole product.

It does not claim:

Riluzole as a new chemical compound.
A crystalline or polymorphic form.
A particular riluzole salt as a standalone composition.
A 50 mg tablet composition.
An oral suspension.
An oral film.
Specific excipients.
A manufacturing process.
A particle-size distribution.
A controlled-release dosage form.

Claims 10 and 11 refer to a pharmaceutically acceptable carrier or compatible product, but those limitations are incorporated into a method of administering riluzole. They do not independently claim a formulation.

What other patents protect riluzole?

The riluzole patent estate has several distinct layers:

Patent layer	Typical subject matter	Current significance
Compound patents	Riluzole and related benzothiazoles	Expired
Therapeutic-use patents	ALS treatment with riluzole	US 5,527,814 expired
Formulation patents	Suspensions, films, solubilized products, or alternative dosage forms	Potentially relevant to specific products
Manufacturing patents	Synthesis, purification, particle engineering, or process controls	Potentially relevant to API suppliers
Regulatory exclusivity	New chemical entity, orphan-drug, or product-specific exclusivity	Expired for original riluzole products

The original chemical protection for riluzole also expired before or around the period in which generic competition developed. The commercial barrier for generic riluzole was therefore no longer a live compound patent when the principal generic market formed.

Later riluzole products may have had separate formulation or delivery-system patents. Those rights must be analyzed product by product. A formulation patent covering a suspension or oral film would not revive US Patent 5,527,814 and would not extend protection to ordinary riluzole tablets.

What was the FDA exclusivity timeline for riluzole?

Riluzole was approved in the United States as Rilutek for ALS on December 12, 1995. [2]

FDA milestone	Date or period
Rilutek approval	December 12, 1995
Original NCE exclusivity	Approximately through December 12, 2000
Orphan-drug exclusivity	Approximately through December 12, 2002
US Patent 5,527,814 expiration	June 18, 2013
Generic riluzole competition	Developed after statutory and patent barriers expired
Later dosage forms	Oral suspension and oral film approvals occurred under separate product applications

The five-year new chemical entity exclusivity and seven-year orphan-drug exclusivity were regulatory protections, not patent rights. Neither remains active.

Riluzole is a small molecule. It is not a biologic and does not face biosimilar competition under the Public Health Service Act. Competitive entry occurs through the abbreviated new drug application (ANDA) pathway for generic products, not through a biosimilar application.

What is the Orange Book status of US Patent 5,527,814?

The patent was associated with the Rilutek regulatory and patent-protection history. Its legal relevance ended when the patent expired in 2013.

An expired Orange Book patent does not block approval or commercial launch of a generic. It can remain historically visible in FDA patent records, but it no longer creates a current patent certification barrier.

For a later ANDA, the relevant legal questions would have included:

Whether the patent was listed for the reference product.
Whether the ANDA applicant filed a Paragraph III certification stating that the patent would not be infringed or was expired.
Whether a Paragraph IV certification challenged validity, enforceability, or infringement while the patent remained unexpired.
Whether the FDA 30-month stay was triggered during the patent term.

After June 18, 2013, a Paragraph IV challenge to this patent would have had no practical forward-looking value because the patent right had already expired. The patent could not support a current injunction against generic riluzole marketing.

Which companies challenged the riluzole patent?

A reliable assessment must distinguish a formal Paragraph IV challenge from ordinary generic entry.

US Patent 5,527,814 is now expired, and no current Paragraph IV challenge can create a continuing exclusionary period. Generic riluzole products entered the market after the principal patent and regulatory exclusivities had ended.

Publicly available product and patent records do not establish a current, legally operative challenge to this patent. Historical ANDA certifications may have existed during the patent's term, but they no longer affect market access. The commercial result is the same: generic manufacturers can market riluzole without obtaining a license from the former patent owner.

What patent litigation affects riluzole?

The principal litigation risk associated with US Patent 5,527,814 was historical ANDA litigation over whether a generic riluzole product would infringe the ALS-treatment claims before expiration.

That risk has ended. The patent expired more than a decade ago, so:

No injunction can issue under the expired patent for future riluzole sales.
No 30-month stay can be based on the expired patent.
A settlement requiring delayed entry under this patent would have no current patent basis.
A generic manufacturer does not need a license to practice the expired claims.
The patent cannot support a damages claim for post-expiration sales.

Any current litigation involving riluzole would more likely concern a later formulation patent, trade secret, manufacturing dispute, product liability, regulatory exclusivity, or trademark issue rather than US 5,527,814.

Are there formulation patents for riluzole oral suspension or oral film?

Yes, later riluzole dosage forms created separate patent and regulatory questions.

Oral suspension

Tiglutik is an oral suspension formulation of riluzole. Its patent position, if any, must be assessed separately from the expired ALS-use patent. The relevant issues include:

Suspension stability.
Taste masking.
Solubilization.
Preservatives and excipients.
Dose uniformity.
Container and dispensing system.
Product-specific Orange Book listings.

A manufacturer of ordinary riluzole tablets does not necessarily infringe a suspension patent. Conversely, a suspension product may avoid the expired use patent only in the temporal sense; it cannot avoid a live formulation patent merely by using the same active ingredient.

Oral film

Exservan is an oral film formulation of riluzole. The product uses a different delivery system from Rilutek tablets and may be protected by formulation, film, manufacturing, or product-specific patents.

A generic tablet manufacturer generally would not practice an oral-film claim. An oral-film competitor would face a more targeted formulation analysis involving:

Polymer matrix composition.
Film thickness and dissolution.
Riluzole loading.
Taste-masking agents.
Manufacturing conditions.
Packaging and moisture protection.
Product-specific FDA listings.

Neither Tiglutik nor Exservan extends the term of US Patent 5,527,814.

How strong is the patent estate for riluzole?

The current US patent estate for conventional riluzole tablets is weak because the principal compound, use, and regulatory barriers have expired.

Risk category	Assessment
Compound patent risk	Low; original compound protection is expired
ALS method-of-use risk	None from US 5,527,814; expired
50 mg tablet risk	Low from the 814 patent; formulation-specific review still required
Oral suspension risk	Product-specific formulation review required
Oral-film risk	Product-specific formulation and process review required
API manufacturing risk	Depends on later process patents and supplier contracts
Biosimilar risk	Not applicable
FDA exclusivity risk	Expired for the original product
Generic launch risk	Low for standard riluzole tablets
Geographic risk	US rights expired; non-US rights require separate country analysis

The main remaining IP barriers, if any, are product-specific rather than molecule-wide. They are more relevant to differentiated dosage forms than to standard 50 mg riluzole tablets.

What generic launch scenarios exist for riluzole?

Standard tablet

A conventional 50 mg riluzole tablet can generally enter the US market without regard to US Patent 5,527,814 because the patent expired in 2013. The applicant's principal requirements are FDA approval, bioequivalence, manufacturing compliance, labeling compliance, and any remaining valid product-specific patent analysis.

Alternative dosage form

A suspension, oral film, or modified-release product may face a different patent profile. A generic or follow-on applicant may need to address:

Formulation patents.
Device or dispensing patents.
Method-of-use labeling.
Product-specific exclusivity.
Non-infringement or invalidity positions.
Differences between the reference listed drug and the proposed product.

Off-label or narrow-label use

The expired patent does not impose current restrictions on a product label that includes ALS treatment. During the patent term, labeling and intended use could have supported induced-infringement theories. That issue no longer creates an enforceable barrier under the patent.

What is the geographic coverage of the patent?

US Patent 5,527,814 had enforceable effect only in the United States. Its expiration does not determine the status of corresponding foreign patents.

The international landscape requires separate review of:

European Patent Office family members.
National phase patents in major European markets.
Canada.
Japan.
Australia.
China.
South Korea.
Brazil.
Other jurisdictions where riluzole products are sold or manufactured.

A US expiration does not automatically terminate foreign rights. For current commercialization, however, the US patent no longer creates a barrier.

Key Takeaways

US Patent 5,527,814 covers the method of treating ALS with riluzole.
Claim 1 is the broadest claim and covers effective administration of riluzole to an ALS patient.
Claims 2 and 3 narrow the invention to bulbar disease presentations.
Claims 4 through 9 and 12 cover specified dose ranges and dose amounts.
Claims 10, 11, and 13 address carriers, compatible products, and acid addition salts within the treatment method.
The patent is not a composition, tablet, suspension, oral-film, or manufacturing patent.
The patent issued June 18, 1996, and expired June 18, 2013.
Riluzole's NCE and orphan-drug exclusivities also expired.
No current Paragraph IV challenge or license is needed to market standard generic riluzole in the United States.
Any remaining riluzole IP risk is product-specific, particularly for oral suspension, oral film, delivery systems, or manufacturing processes.
Riluzole is a small molecule, so biosimilar analysis does not apply.

FAQs

Does US Patent 5,527,814 cover the riluzole molecule itself?

No. It covers administering riluzole to treat ALS. The patent does not claim riluzole as a standalone chemical composition.

Can a generic company market 50 mg riluzole tablets?

Yes, the patent expired on June 18, 2013. A generic applicant must still satisfy FDA approval and manufacturing requirements and review any later product-specific patents.

Does the patent cover riluzole for other neurological diseases?

No. The claims are directed to ALS treatment. They do not expressly cover unrelated diseases or indications.

Does claim 13 create a separate patent on riluzole acid addition salts?

No. Claim 13 is a dependent method claim. It narrows the administration method to an acid addition salt and does not create an independent composition patent.

Are Tiglutik and Exservan protected by US Patent 5,527,814?

They may fall within the expired method claims when used to treat ALS, but the patent does not specifically claim either dosage form. Any current protection would arise from separate formulation, manufacturing, delivery, regulatory, or product-specific patent rights.

References

United States Patent and Trademark Office. (1996). US Patent No. 5,527,814: Use of 2-amino-6-(trifluoromethoxy)benzothiazole in the treatment of amyotrophic lateral sclerosis. https://patents.google.com/patent/US5527814
U.S. Food and Drug Administration. (2024). Drugs@FDA: Rilutek (riluzole) and riluzole products. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Food and Drug Administration. (2024). Orange Book patent and exclusivity information. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
U.S. Congress. (1994). Uruguay Round Agreements Act, Pub. L. No. 103-465. https://www.congress.gov/bill/103rd-congress/house-bill/5110

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
France	92 02696	Mar 06, 1992

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	149833	⤷ Start Trial
Australia	2948292	⤷ Start Trial
Australia	666150	⤷ Start Trial
Canada	2117466	⤷ Start Trial
Czech Republic	281293	⤷ Start Trial
Czech Republic	9402120	⤷ Start Trial
Germany	69218255	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,527,814

Summary for Patent: 5,527,814