US Drug Patent 4,430,343: Claim Scope, Expiration, FDA Status, and Patent Landscape

US Patent 4,430,343 covers a genus of substituted 2-piperazinyl benzimidazole compounds, selected acid-addition salts, and antihistaminic compositions containing them. The patent’s practical value was concentrated in composition-of-matter protection. Its 17-year pre-1995 patent term expired in 2001, leaving no current US enforcement right based on this patent.

The claims supplied identify four specifically named benzimidazole compounds, including piperazine and homopiperazine analogues with ethoxy, propargyloxy, or phenoxy substituents.

What compounds does US Patent 4,430,343 protect?

Claim 1 is a Markush compound claim. It covers a benzimidazole core bearing:

An N-substituted alkoxyethyl-type side chain at the benzimidazole nitrogen;
A piperazine-related substituent at the 2-position;
Defined substituent options for R1;
Defined substituent options for R2;
A ring or spacer variable represented by n, limited to 2 or 3;
Pharmaceutically acceptable acid-addition salts.

Based on the named compounds in dependent claims 2 through 5, the claimed architecture includes the following elements:

Structural element	Claimed options
Benzimidazole nucleus	Substituted benzimidazole
N-1 side chain	Ethoxyethyl, propargyloxyethyl, phenoxyethyl and related members of the genus
C-2 basic substituent	Piperazinyl or homopiperazinyl-type group
Piperazine N-substitution	Hydrogen or C1-C3 alkyl, including methyl
Terminal substituent R1	C1-C3 alkyl, allyl, propargyl, or phenyl
Spacer variable n	2 or 3
Salt form	Pharmaceutically acceptable acid-addition salts
Therapeutic use	Antihistaminic activity

The missing structural drawing designated “##STR20##” is material to interpreting the exact atom-by-atom connectivity of claim 1. The named compounds nevertheless establish the principal claimed scaffold and substitution pattern.

How broad is claim 1 of US 4,430,343?

Claim 1 is the principal patent claim and has substantially greater scope than claims 2 through 5. It is a genus claim rather than a single-compound claim.

Its breadth comes from four sources:

R1 has multiple permitted substituent classes.
R2 may be hydrogen or a lower alkyl group.
n may be 2 or 3.
The claim covers both the free-base chemical entity and its pharmaceutically acceptable acid-addition salts.

A compound would generally fall within claim 1 only if all required structural limitations are met. A benzimidazole antihistamine outside the claimed piperazine or homopiperazine configuration would not infringe merely because it has antihistaminic activity.

The claim is also vulnerable to ordinary chemical-scope limitations. The following changes could move a candidate outside the literal scope, depending on the full formula:

Replacing the benzimidazole nucleus with another heterocycle;
Using a spacer length other than the claimed n values;
Substituting a non-permitted group for R1;
Using a non-permitted substitution pattern on the piperazine nitrogen;
Replacing the claimed piperazine-related ring with a structurally different amine;
Removing the claimed alkoxy, propargyloxy, or phenoxy relationship.

The presence of a pharmaceutically acceptable salt does not create an independent active-ingredient class. Salt claims generally follow the underlying covered free base where the salt is formed from a covered compound.

Which compounds are expressly claimed in US 4,430,343?

Claims 2 through 5 identify specific species within the genus.

Claim	Expressly identified compound	Structural significance
2	1-[2-(ethoxy)ethyl]-2-(4-methyl-1-homopiperazinyl)benzimidazole	Homopiperazine analogue with N-methyl substitution
3	1-[2-(propargyloxy)ethyl]-2-(4-methyl-1-piperazinyl)benzimidazole	Propargyloxyethyl and N-methyl piperazine
4	1-[2-(ethoxy)ethyl]-2-(1-piperazinyl)benzimidazole	Unsubstituted piperazine nitrogen
5	1-[2-(phenoxy)ethyl]-2-(4-methyl-1-piperazinyl)benzimidazole	Phenoxyethyl and N-methyl piperazine

Each claim also covers pharmaceutically acceptable acid-addition salts of the named compound.

Claims 2 through 5 are narrower than claim 1. They provide fallback protection for individually identified species, but they do not expand the genus beyond claim 1.

What antihistaminic compositions are protected?

Claim 6 covers an antihistaminic composition containing:

An effective amount of a compound falling within the claim 1 genus; and
A conventional pharmaceutically acceptable carrier or diluent.

Claims 7 through 10 narrow claim 6 to the four specifically named compounds.

The composition claims may reach tablets, capsules, powders, solutions, suspensions, or other pharmaceutical dosage forms if the formulation contains a covered active ingredient and a conventional pharmaceutical carrier. The claims do not appear, from the supplied text, to require a particular dosage strength, excipient, release profile, route of administration, or dosage regimen.

What formulations are protected by the patent?

The supplied claims do not contain a separate formulation invention. They do not expressly require:

Extended release;
Enteric coating;
A particular particle size;
A specific polymorph;
A defined dissolution profile;
A specific pharmaceutical excipient;
A particular tablet or capsule technology;
A defined dose or dosing schedule.

The formulation protection is therefore secondary to the active-ingredient protection. A formulation containing a covered compound could have implicated claim 6 during the patent term even if its excipient system differed from the examples, provided the product satisfied the claim’s composition requirements.

Does the patent contain method-of-use claims?

No method-of-use claim appears in the supplied claims. Claim 6 is a composition claim reciting an antihistaminic composition, not a conventional treatment method requiring administration to a patient.

This distinction matters. The patent does not, on the supplied claim set, separately claim:

Treating allergic rhinitis;
Treating urticaria;
Treating pruritus;
Blocking histamine H1 receptors;
Administering a specified dose;
Treating a defined patient population.

The therapeutic disclosure may support the antihistaminic characterization, but the enforceable claim categories are compounds and compositions.

When did US Patent 4,430,343 lose exclusivity?

US Patent 4,430,343 was granted in 1984. For a US patent issued before June 8, 1995, the ordinary term was the longer of 17 years from grant or 20 years from the earliest effective US nonprovisional filing date, subject to applicable transitional rules and terminal disclaimers.[1]

On the supplied patent number and grant-era framework, the patent’s ordinary US term ended in 2001, approximately 17 years after grant. The patent therefore does not create a live US blocking right in 2026.

Event	Approximate date
US patent grant	1984
Ordinary pre-1995 patent term	17 years from grant
Expected US expiration	2001
Current enforceability	Expired
Current Paragraph IV relevance	None for this patent
Current biosimilar relevance	None

An exact term calculation would depend on the complete USPTO prosecution record, including any terminal disclaimer, patent-term adjustment, or statutory correction. None of those matters can extend a pre-1995 patent beyond the ordinary historical term without a specific record basis.

What is the Orange Book status of US 4,430,343?

US Patent 4,430,343 is not, by itself, an Orange Book-listed patent. The Orange Book lists patents submitted by sponsors for approved drug products, not every historical compound patent issued by the USPTO.[2]

The patent claims do not identify:

An FDA-approved active ingredient;
An approved brand name;
An approved New Drug Application;
A product sponsor;
A dosage form approved by FDA;
An Orange Book patent-use code.

The claims also identify chemical entities that are not recognizable from the supplied text as a currently marketed FDA-approved antihistamine. The practical Orange Book risk is therefore low. A generic applicant would not normally face a current Orange Book patent challenge based on an expired patent.

Are Paragraph IV challenges relevant?

No current Paragraph IV challenge is required against an expired patent.

Under the Hatch-Waxman framework, a generic applicant may certify to listed patents, including through a Paragraph IV certification when asserting invalidity, unenforceability, or noninfringement.[3] That mechanism is relevant only while the patent remains a listed and potentially enforceable barrier to approval.

For US Patent 4,430,343:

The patent term has ended;
The patent cannot support a current injunction against launch;
A Paragraph IV certification directed solely to this patent would have no practical blocking effect;
The patent should not create a 30-month stay under current Hatch-Waxman litigation mechanics.

Is there biosimilar risk associated with this patent?

No. Biosimilar regulation applies to biological products, while US Patent 4,430,343 claims small-molecule benzimidazole compounds and pharmaceutical compositions.[4]

The relevant competitive risks would historically have involved:

Small-molecule generic synthesis;
Salt selection;
Formulation development;
Chemical process patents;
Regulatory exclusivity;
Market authorization for a particular active ingredient.

Biosimilar interchangeability, reference biologics, and the Biologics Price Competition and Innovation Act are not applicable.

How strong was the patent estate?

The patent’s strongest historical protection was claim 1, the composition-of-matter genus. Claims 2 through 5 strengthened the position for named species. Claims 6 through 10 added formulation-level coverage but were narrower because they required an antihistaminic composition containing a covered active compound.

Claim category	Historical strength	Present commercial value
Genus compound claim	High, subject to validity and written-description limits	None after expiration
Named species claims	High for listed compounds	None after expiration
Salt claims	Useful against salt-form products	None after expiration
Composition claims	Moderate; dependent on covered active ingredient	None after expiration
Method-of-use claims	Not present in supplied claims	None
Manufacturing claims	Not present in supplied claims	None

Potential validity pressure points would have included enablement, written description, anticipation, obviousness, claim construction, and proof that the specific compounds had the claimed antihistaminic activity. The broad genus claim would have carried greater validity risk than the named species claims if the specification did not adequately disclose representative compounds across the full R1/R2/n range.

What manufacturing and IP barriers would have existed?

The patent does not claim a manufacturing process in the supplied claims. It therefore would not have directly blocked a noninfringing process for making an outside-the-claim compound.

Historical manufacturing barriers may still have included:

Control of regioselective benzimidazole synthesis;
Alkylation of the benzimidazole nitrogen;
Installation of the piperazine or homopiperazine substituent;
Control of residual starting materials;
Salt formation and crystallization;
Analytical characterization of the final active ingredient.

Those issues are technical and regulatory barriers, not continuing rights under US 4,430,343.

What licensing deals or litigation affect the patent?

The supplied claims identify no license, settlement, litigation, or commercial agreement. The patent itself does not establish that a licensing transaction occurred.

Because the patent expired in 2001, any historic license would have no continuing exclusionary effect based solely on this patent. A later agreement could still contain contractual restrictions, but those would arise from the contract rather than from patent enforceability.

No current litigation strategy should treat US 4,430,343 as a live US patent obstacle. Any relevant present-day freedom-to-operate review would need to focus on later patents covering a commercial product, polymorph, process, formulation, combination, or approved therapeutic use.

How does US 4,430,343 compare with a modern drug patent estate?

US 4,430,343 is a compact early small-molecule estate. Its protection is concentrated in one core patent containing:

A Markush compound genus;
Four named species;
Corresponding antihistaminic composition claims.

A modern pharmaceutical franchise often uses a layered estate involving:

Composition-of-matter patents;
Salt and polymorph patents;
Crystalline-form patents;
Formulation patents;
Manufacturing-process patents;
Combination patents;
Method-of-use patents;
Pediatric or regulatory exclusivity;
International counterparts.

The supplied claim set does not show that later layering. Its commercial life therefore depended primarily on the original compound claims and the regulatory status of the covered active ingredients.

Key Takeaways

US Patent 4,430,343 claims substituted piperazinyl and homopiperazinyl benzimidazoles, their acid-addition salts, and antihistaminic compositions.
Claim 1 is the principal broad Markush compound claim.
Claims 2 through 5 cover four expressly named chemical species.
Claims 6 through 10 cover compositions containing the claimed active ingredients, not standalone treatment methods.
No manufacturing-process, polymorph, formulation-specific, or method-of-use claims appear in the supplied claim set.
The patent’s ordinary US term ended in 2001.
The patent presents no current Paragraph IV, biosimilar, or Orange Book blocking risk.
Any current freedom-to-operate risk would have to come from later patents, not US Patent 4,430,343 itself.

Frequently Asked Questions

Does US Patent 4,430,343 cover all benzimidazole antihistamines?

No. It covers a defined structural genus with specific side-chain, piperazine-related, substituent, and spacer limitations. Benzimidazole antihistamines outside those limitations are not automatically covered.

Are the hydrochloride or other acid-addition salts separately protected?

Yes, where the salt is a pharmaceutically acceptable acid-addition salt of a covered compound. The salt language follows the claimed compound rather than creating an unrestricted salt category.

Could a formulation infringe claim 6 without using one of the four named compounds?

Yes. Claim 6 refers to the broader claim 1 genus. A composition containing another compound within that genus could fall within claim 6, subject to the complete structural formula and other claim limitations.

Does the patent block a generic launch today?

No. The patent expired in 2001 and cannot independently block a current US generic launch.

Does the patent cover a treatment method for allergic rhinitis?

Not on the supplied claims. The patent claims compounds and antihistaminic compositions. No patient-treatment method claim is included.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term provisions. https://www.uspto.gov
U.S. Food and Drug Administration. (n.d.). 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
United States Code, 21 U.S.C. § 355(j).
U.S. Food and Drug Administration. (n.d.). Biosimilar and interchangeable biosimilar products. https://www.fda.gov/drugs/biosimilarsաբեր

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	56-178804	Nov 06, 1981

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	19878	⤷ Start Trial
Germany	3271269	⤷ Start Trial
European Patent Office	0079545	⤷ Start Trial
Japan	H0224821	⤷ Start Trial
Japan	S5879983	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,430,343

Summary for Patent: 4,430,343