United States Patent 6,284,770: Scope, Claims, Expiration, and Patent Landscape for 5-HT3 Antagonists in Female IBS

U.S. Patent No. 6,284,770 protected the use of specified 5-HT3 receptor antagonists, particularly alosetron hydrochloride, to treat female patients with nonconstipated, diarrhea-predominant, or alternating-type irritable bowel syndrome. The patent issued on September 4, 2001 and expired in 2017 under the applicable 20-year patent term. It no longer creates a blocking patent right for generic alosetron or other listed 5-HT3 antagonists.

The patent was a method-of-treatment patent. It did not claim alosetron as a chemical compound, a tablet formulation, a manufacturing process, or a particular dosing schedule.

What does U.S. Patent 6,284,770 cover?

The patent covers administering a 5-HT3 receptor antagonist to a female patient with a specified IBS phenotype.

The claims divide into two principal categories:

A genus of 5-HT3 antagonists expressly identified by name.
Alosetron, separately claimed and with an express hydrochloride-salt limitation.

The covered patient populations are:

Female patients with nonconstipated IBS.
Female patients with diarrhea-predominant IBS.
Female patients with alternating constipation/diarrhea IBS.

The core therapeutic concept is the use of 5-HT3 blockade to treat female IBS characterized by diarrhea or the absence of constipation.

Patent identification

Item	Details
Patent	U.S. Patent No. 6,284,770
Title	5-HT3 receptor antagonists for treating irritable bowel syndrome
Patent type	Method of treatment
Issue date	September 4, 2001
Patent holder/assignee	Glaxo-related entity, subsequently associated with GlaxoSmithKline
Therapeutic area	Gastroenterology; irritable bowel syndrome
Principal product	Alosetron hydrochloride, marketed as Lotronex
Patent status	Expired
Expiration	2017
FDA product associated with claims	Lotronex, alosetron hydrochloride tablets

The patent’s enforceable term ended before the current market period for generic alosetron. Patent expiration does not eliminate regulatory restrictions attached to the drug’s safety profile or FDA labeling.

What are the claims of U.S. Patent 6,284,770?

Claims 1 and 4: Named 5-HT3 antagonist genus

Claims 1 and 4 cover treatment using one of the following named compounds or a pharmaceutically acceptable derivative:

Granisetron
Azasetron
Tropisetron
Ramosetron
Ondansetron
Lerisetron
(R)-Zacopride
Cilansetron
Itasetron
Indisetron
Dolasetron

Claim 1 applies to nonconstipated female IBS. Claim 4 applies specifically to diarrhea-predominant female IBS.

The phrase "selected from the group consisting of" generally creates a closed Markush group. A compound outside the listed group would not fall within the literal scope of these claims merely because it is another 5-HT3 antagonist.

Claims 2, 5, and 8: Alosetron

Claims 2, 5, and 8 separately cover alosetron treatment:

Claim 2: nonconstipated female IBS.
Claim 5: diarrhea-predominant female IBS.
Claim 8: alternating constipation/diarrhea IBS.

These claims are narrower as to the active ingredient than claims 1, 4, and 7, but they avoid the need to prove that alosetron falls within the broader named-antagonist group.

Claims 3, 6, and 9: Alosetron hydrochloride

Claims 3, 6, and 9 narrow the corresponding alosetron claims to alosetron hydrochloride:

Claim 3 depends on claim 2.
Claim 6 depends on claim 5.
Claim 9 depends on claim 8.

These claims directly correspond to the salt form used in Lotronex tablets.

How broad is the claim scope?

The patent has meaningful therapeutic breadth but limited technical breadth.

Breadth by active ingredient

The patent covers 11 specifically named 5-HT3 antagonists in the genus claims. It does not cover every possible 5-HT3 antagonist. The use of the closed Markush wording limits the group to the listed compounds and their pharmaceutically acceptable derivatives.

The alosetron claims are particularly important commercially because they target the active ingredient used in Lotronex. Claims 3, 6, and 9 add protection for the hydrochloride salt.

Breadth by patient population

The claims require treatment of female IBS patients. A method directed only to male IBS patients would not literally satisfy the gender limitation.

The claims also require a nonconstipated, diarrhea-predominant, or alternating constipation/diarrhea phenotype. A treatment method directed solely to constipation-predominant IBS would fall outside the express claim language.

The relationship among the patient categories is significant:

Diarrhea-predominant IBS is generally within the broader concept of nonconstipated IBS.
Alternating IBS is separately claimed and may not always fit a strict clinical definition of nonconstipated IBS at every point in the disease course.
Constipation-predominant IBS is outside the stated patient populations.

Breadth by treatment requirements

Each independent claim requires:

A female patient.
A specified IBS diagnosis or symptom pattern.
Administration of an effective amount.
A listed 5-HT3 antagonist, or alosetron for the alosetron claims.

The claims do not require:

A specific dose.
A specific dosage form.
Oral administration.
A specific treatment duration.
A particular endpoint, such as reduction in stool frequency or abdominal pain.
A specific diagnostic scoring system.
Concomitant dietary or behavioral treatment.

What formulations are protected by Patent 6,284,770?

The patent does not claim a specific formulation architecture. It covers therapeutic administration of the active ingredient regardless of whether the product is supplied as a tablet, capsule, liquid, or another conventional dosage form, provided the method satisfies the claim limitations.

The alosetron hydrochloride claims cover the salt form, but they do not require the commercial Lotronex formulation. A generic tablet containing alosetron hydrochloride could have fallen within the claims during the patent term if used according to the claimed IBS indications.

The patent does not independently protect:

Extended-release alosetron.
Enteric-coated alosetron.
A particular excipient system.
A specific tablet hardness or dissolution profile.
A manufacturing process for alosetron hydrochloride.
A proprietary packaging configuration.

Any separate formulation or process patents would have to be analyzed independently.

What method-of-use protection did the patent provide?

The patent is principally a method-of-use patent for IBS treatment.

Claim group	Patient population	Active ingredient
Claims 1, 2, 3	Nonconstipated female IBS	Listed 5-HT3 antagonists; alosetron; alosetron hydrochloride
Claims 4, 5, 6	Diarrhea-predominant female IBS	Listed 5-HT3 antagonists; alosetron; alosetron hydrochloride
Claims 7, 8, 9	Alternating constipation/diarrhea IBS	Listed 5-HT3 antagonists; alosetron; alosetron hydrochloride

The patent’s commercial significance came from linking alosetron to the female diarrhea-predominant IBS population, which is the population reflected in the FDA’s restricted Lotronex indication.

When did U.S. Patent 6,284,770 lose exclusivity?

U.S. Patent 6,284,770 expired in 2017. Its statutory term was governed by the post-1995 patent-term rule, generally calculated as 20 years from the relevant nonprovisional filing or international filing date, subject to any applicable patent-term adjustment.

The expiration ended the patent-based exclusivity for the claimed treatment methods. It also eliminated the principal basis for a Paragraph IV certification against this patent in a later alosetron ANDA.

Patent expiration did not remove:

FDA labeling requirements.
Risk-management obligations.
Any remaining regulatory exclusivity.
Other patents covering alosetron chemistry, formulations, or manufacturing.
Trade-secret protection for manufacturing processes.

What was the FDA status of Lotronex and alosetron?

Alosetron hydrochloride was developed and commercialized by Glaxo Wellcome, later part of GlaxoSmithKline.

FDA event	Date
Lotronex approval	February 2000
Voluntary market withdrawal	November 2000
Reintroduction under restricted conditions	June 2002
Active ingredient	Alosetron hydrochloride
Original indication	Women with severe diarrhea-predominant IBS who have failed conventional therapy

The withdrawal and later reintroduction followed reports of serious gastrointestinal adverse events, including ischemic colitis and complications related to severe constipation. The restricted-use framework became a central commercial and regulatory feature of the product.

The patent claims are broader in wording than the eventual commercial label. A patent claim may cover a therapeutic concept that the FDA approves only for a narrower population or under more restrictive prescribing conditions.

What was the Orange Book status?

The relevant Orange Book analysis must distinguish between product patents and method-of-use patents.

Alosetron hydrochloride was listed in connection with the Lotronex NDA. U.S. Patent 6,284,770 was directed to methods of using alosetron and therefore had potential Orange Book significance as a method-of-use patent during its term. The listed patent did not operate as a permanent bar to all generic alosetron products because its claims were tied to particular IBS indications.

A generic applicant could address a method-of-use patent through:

A Paragraph IV certification challenging validity, enforceability, or infringement.
A Section viii statement carving out the patented use from the proposed labeling.
A labeling strategy that omitted the claimed female IBS indication, subject to FDA approval and infringement analysis.

Because the patent expired in 2017, it is no longer a current Orange Book barrier to approval or launch.

Were there Paragraph IV challenges or patent litigation?

The principal current conclusion is that U.S. Patent 6,284,770 cannot support a new infringement suit against a generic launch because it is expired.

During the patent term, an ANDA applicant could have challenged the patent under the Hatch-Waxman framework. A Paragraph IV certification would have created a potential action under 35 U.S.C. § 271(e)(2), but the patent’s expiration removes the prospective commercial value of such a challenge.

No continuing litigation risk remains under this patent. Any historical litigation involving alosetron, Lotronex, or related FDA restrictions should be separated from infringement litigation concerning Patent 6,284,770.

The safety-related withdrawal and reintroduction of Lotronex were regulatory events, not evidence that the patent claims were invalid or unenforceable.

Did the patent face biosimilar risk?

No. Alosetron is a synthetic small-molecule drug, not a biologic. Biosimilar provisions under the Public Health Service Act do not apply.

The relevant competitive pathway is an ANDA for a generic version of alosetron hydrochloride. A generic applicant must establish pharmaceutical equivalence and bioequivalence and must address any listed patents and applicable labeling restrictions.

How does Patent 6,284,770 compare with other alosetron protection?

Protection category	Covered subject matter	Commercial relevance after 2017
Composition-of-matter patent	Alosetron chemical entity or related compound	Generally expired
U.S. Patent 6,284,770	Use of alosetron and named 5-HT3 antagonists in specified female IBS populations	Expired
Salt protection	Alosetron hydrochloride, where separately claimed	Requires separate patent review; no extension from Patent 6,284,770
Formulation protection	Tablet, release profile, excipient system	Requires separate patent review
Manufacturing protection	Synthesis, purification, crystallization, or salt formation	Requires separate patent review
Regulatory protection	NDA exclusivity and labeling restrictions	Separate from patent rights

Patent 6,284,770 was strongest against a product whose label expressly included treatment of female diarrhea-predominant IBS. It was less effective against a generic product with a carved-out label omitting the patented use, although physicians’ prescribing practices and induced-infringement theories would still have required analysis during the patent term.

What generic launch risks existed?

During the patent term, the principal generic risks were:

Direct infringement if the generic product was marketed for the claimed IBS populations.
Induced infringement based on promotional materials or labeling.
Regulatory delay following a Paragraph IV lawsuit.
Risk that a skinny-label strategy would be viewed as ineffective if the patented indication remained practically encouraged.
Separate patent exposure under composition, formulation, salt, or manufacturing patents.

After expiration, those patent risks materially declined. The remaining commercial barriers are primarily regulatory and market-based:

Restricted prescribing and safety monitoring.
Limited physician demand.
Generic manufacturing and quality requirements.
The commercial burden of maintaining a product associated with serious gastrointestinal adverse events.
Competition from non-5-HT3 therapies and off-label use of other agents.

What licensing deals affected the patent?

The patent originated within the Glaxo organization and supported the Lotronex commercial program. The principal value chain was internal corporate ownership through Glaxo Wellcome and later GlaxoSmithKline rather than a widely reported third-party license for the claimed IBS method.

The patent should therefore be analyzed as part of the Glaxo alosetron franchise, together with the Lotronex NDA, clinical data, FDA risk controls, and any separate alosetron compound or manufacturing rights.

How strong was the patent estate?

Strengths

Directly targeted the clinically valuable female diarrhea-predominant IBS population.
Claimed alosetron independently from the broader antagonist genus.
Included alosetron hydrochloride, the commercial salt.
Covered multiple IBS phenotypes.
Avoided dependence on a particular dose or dosage form.
Aligned with the principal FDA-approved use of Lotronex.

Limitations

The claims were limited to female patients.
The claims did not cover constipation-predominant IBS.
The antagonist genus was closed and expressly enumerated.
The claims were method claims, not composition claims.
The patent expired in 2017.
The commercial indication was constrained by serious safety risks.
A generic applicant could potentially use a Section viii labeling carve-out for patented indications.

The patent was commercially important during the protected period but does not provide a current blocking position.

What is the current competitive landscape?

The relevant competitive set includes:

Generic alosetron hydrochloride.
Branded or generic 5-HT3 antagonists used for other indications.
Ramosetron in jurisdictions where approved for IBS.
Tegaserod, a 5-HT4 agonist with a different pharmacological mechanism.
Eluxadoline for diarrhea-predominant IBS.
Rifaximin for selected IBS with diarrhea patients.
Loperamide and other symptomatic antidiarrheal therapies.
Dietary, neuromodulator, and behavioral approaches.

Ondansetron and granisetron may be clinically relevant 5-HT3 comparators, but their presence in Patent 6,284,770 did not give the patent holder ownership of those compounds or their non-IBS uses.

What geographic coverage did the patent have?

U.S. Patent 6,284,770 provided rights only in the United States. Foreign counterparts would require separate country-by-country analysis.

The patent did not automatically control:

Alosetron sales in Europe.
Ramosetron use in Japan or other Asian markets.
Generic manufacture outside the United States.
Export activity, except where U.S. patent law applied to the relevant conduct.
Foreign formulations or uses.

The international patent family may have included corresponding applications, but each jurisdiction could have different claims, prosecution outcomes, term dates, and legal status.

Key Takeaways

U.S. Patent 6,284,770 was a method-of-treatment patent for female IBS.
It covered alosetron, alosetron hydrochloride, and 10 other named 5-HT3 antagonists.
The principal populations were nonconstipated, diarrhea-predominant, and alternating-type female IBS.
It did not claim the alosetron molecule, a specific tablet formulation, or a manufacturing process.
The patent issued on September 4, 2001 and expired in 2017.
It is no longer a blocking patent for generic alosetron hydrochloride.
No biosimilar pathway applies because alosetron is a small molecule.
Current commercial risk is driven by FDA safety restrictions, generic economics, and market demand rather than this expired patent.
Any remaining alosetron freedom-to-operate review must examine separate composition, formulation, process, regulatory, and foreign rights.

FAQs

Can a generic manufacturer market alosetron for diarrhea-predominant IBS today?

Patent 6,284,770 no longer prevents that use because it expired in 2017. The manufacturer must still comply with FDA approval, labeling, safety, and any current risk-management requirements.

Did Patent 6,284,770 cover male IBS patients?

No. Each claim expressly requires treatment of female IBS patients.

Did the patent cover constipation-predominant IBS?

No. The claims address nonconstipated IBS, diarrhea-predominant IBS, and alternating constipation/diarrhea IBS. Constipation-predominant IBS is not expressly covered.

Is alosetron hydrochloride still protected by the patent?

No. Claims 3, 6, and 9 covered alosetron hydrochloride during the patent term, but the patent expired in 2017.

Could a drug company rely on this patent to block an off-label use of ondansetron?

No. The patent is expired, and it never granted ownership of ondansetron as a compound. Its historical claims covered specified treatment methods involving ondansetron and other listed 5-HT3 antagonists in the defined female IBS populations.

References

U.S. Patent and Trademark Office. (2001). U.S. Patent No. 6,284,770: 5-HT3 receptor antagonists for treating irritable bowel syndrome. Washington, DC: U.S. Department of Commerce.
U.S. Food and Drug Administration. (2000). Lotronex approval package and prescribing information: Alosetron hydrochloride. Silver Spring, MD: U.S. Department of Health and Human Services.
U.S. Food and Drug Administration. (2002). FDA approves return of Lotronex with risk-management program. Silver Spring, MD: U.S. Department of Health and Human Services.
U.S. Congress. (2012). 35 U.S.C. § 154: Contents and term of patent; provisional rights. Washington, DC: Office of the Law Revision Counsel.
U.S. Congress. (2012). 35 U.S.C. § 271(e): Infringement of patent. Washington, DC: Office of the Law Revision Counsel.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Silver Spring, MD: U.S. Department of Health and Human Services.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	9721139	Oct 07, 1997

PCT Information
PCT Filed	October 05, 1998	PCT Application Number:	PCT/EP98/06278
PCT Publication Date:	April 15, 1999	PCT Publication Number:	WO99/17755

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	017296	⤷ Start Trial
Australia	750818	⤷ Start Trial
Australia	9629398	⤷ Start Trial
Brazil	9812886	⤷ Start Trial
Canada	2305751	⤷ Start Trial
China	1281357	⤷ Start Trial
Colombia	5011096	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,284,770

Summary for Patent: 6,284,770