United States Drug Patent 4,311,708: Claim Scope, Betaxolol Protection, Expiration, and Patent Landscape

U.S. Patent No. 4,311,708 covers a class of substituted phenoxypropanolamines with selective beta-1 adrenergic blocking activity. The most commercially important compound within the claims is betaxolol, chemically identified as 1-[4-(2-cyclopropylmethoxyethyl)phenoxy]-3-isopropylamino-propan-2-ol, generally marketed as betaxolol hydrochloride.

The patent issued on January 19, 1982. Because it is a pre-Uruguay Round Agreements Act patent, its ordinary term was 17 years from issuance. Absent a terminal disclaimer or an unusual patent-term adjustment, the patent expired on January 19, 1999.[1] It therefore does not presently block generic manufacture, ophthalmic formulation development, or commercial sale of betaxolol based on the claimed subject matter alone.

The claims divide into two chemical Markush groups, individual compound claims, and beta-1 receptor blocking method claims. The patent’s strongest historical protection was the compound coverage for betaxolol and related cycloalkyl-substituted analogues. Its present commercial significance is primarily historical and freedom-to-operate related.

What drug does U.S. Patent 4,311,708 protect?

The principal drug associated with the patent is betaxolol.

Attribute	Description
Active ingredient	Betaxolol
Common salt	Betaxolol hydrochloride
Core structure	Aryloxypropanolamine beta blocker
Receptor profile	Relatively selective beta-1 adrenergic antagonist
Major dosage form	Ophthalmic solution or suspension
Main indication	Reduction of elevated intraocular pressure in ocular hypertension and open-angle glaucoma
Key claimed compound	1-[4-(2-cyclopropylmethoxyethyl)phenoxy]-3-isopropylamino-propan-2-ol
Foundational patent	U.S. Patent No. 4,311,708
Issue date	January 19, 1982
Ordinary patent expiration	January 19, 1999

Betaxolol is structurally distinct from nonselective ophthalmic beta blockers such as timolol. Its beta-1 selectivity was commercially relevant because beta-1-selective activity can reduce, although not eliminate, concern over bronchial beta-2 blockade relative to nonselective agents.[2]

The patent claims do not use the generic name “betaxolol.” They protect the chemical structure and its pharmaceutically acceptable salts. A generic applicant would therefore analyze the structure against the claim language rather than rely on the product name.

What chemical structures are covered by claims 1 through 15?

Claims 1 through 15 are composition-of-matter claims. They cover substituted phenoxypropanolamines containing cycloalkyl-derived substituents and one of three linking groups: oxygen, sulfur, or sulfone.

Claims 1 through 11: cycloalkylmethyl-linked derivatives

Claim 1 establishes a broad genus. Based on the named compounds in the dependent claims, the genus includes compounds with the following characteristics:

A phenoxypropanolamine core.
A cycloalkyl group selected from cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl.
A cycloalkylmethyl substituent.
A linker represented by X, where X is oxygen, sulfur, or sulfone.
An A substituent represented as hydrogen or methyl.
A secondary or tertiary amino substituent, depending on the particular structure represented in the formula.
Pharmaceutically acceptable salts.

The claimed cycloalkyl range is closed as written. A cycloheptyl or bicycloalkyl analogue would not fall within the literal cycloalkyl limitation, although it could raise an equivalents issue depending on prosecution history and the accused structure.

Claim	Scope
1	Broad genus covering the specified cycloalkyl, X, and A combinations
2	Claim 1 limited to cyclopropyl
3	Claim 1 limited to X = oxygen
4	Claim 1 limited to X = sulfur
5	Claim 1 limited to X = sulfone
6	Claim 2 with X = oxygen
7	Specific cyclopropylmethyl sulfone compound with an isopropylamino substituent
8	Specific cyclobutylmethoxy compound with an isopropylamino substituent
9	Specific cyclopropylmethylthio compound with an isopropylamino substituent
10	Specific cyclopropylmethoxy compound with an isopropylamino substituent
11	Specific cyclopropylmethoxy compound with a tert-butylamino substituent

Claim 10 corresponds to betaxolol as identified in the provided claim text:

1-[4-(2-cyclopropylmethoxy-ethoxy)-phenoxy]-3-isopropylamino-propan-2-ol.

The equivalent conventional structural description is generally rendered as:

1-[4-[2-(cyclopropylmethoxy)ethyl]phenoxy]-3-(isopropylamino)-2-propanol.

The hydrochloride salt is betaxolol hydrochloride.

Claims 12 through 15: a second structural genus

Claims 12 through 15 cover a second formula in which the cycloalkyl-derived substituent is attached through a different connectivity from the claims 1 through 11 series. The named compounds identify the principal variation as a cycloalkylmethyl group connected through a two-carbon chain to the phenyl ring.

Claim	Named compound or scope
12	Second broad genus using cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl; X = oxygen, sulfur, or sulfone; A = hydrogen or methyl
13	Cyclobutylmethylsulfonyl compound with an isopropylamino substituent
14	Cyclobutylmethoxyethyl compound with an isopropylamino substituent
15	Cyclobutylmethylthioethyl compound with an isopropylamino substituent

These claims are separate from the betaxolol-specific claim 10. A compound that satisfies claim 10 may not satisfy claims 12 through 15 because the two formula families appear to differ in the location and connectivity of the cycloalkyl-derived substituent.

What is the significance of the claim 8 dependency error?

The supplied text contains an apparent internal inconsistency.

Claim 6 depends on claim 2 and claim 3. Claim 2 limits the cycloalkyl group to cyclopropyl, while claim 8 is written as a compound of claim 6 but names a cyclobutyl compound:

“1-[4-(2-cyclobutylmethoxy-ethoxy)-phenoxy]-3-isopropylamino-propan-2-ol.”

If the issued patent contains this wording, claim 8 is internally defective on its face because its dependency appears to require cyclopropyl while its specific compound recites cyclobutyl. The legal effect would depend on the official issued patent, prosecution history, any certificate of correction, and judicial claim construction. The apparent inconsistency should not be treated as an expanded claim covering both cyclopropyl and cyclobutyl compounds.

The conflict does not affect claim 10, which independently names the cyclopropylmethoxy compound associated with betaxolol.

What does claim 10 cover?

Claim 10 is the most commercially significant compound claim in the provided set. It covers the specified cyclopropylmethoxy phenoxypropanolamine and its pharmaceutically acceptable salts.

The claim has several important limitations:

The cycloalkyl group is cyclopropyl.
The connecting atom in the relevant side chain is oxygen.
The phenoxypropanolamine core is required.
The amino substituent is isopropylamino.
The claim includes pharmaceutically acceptable salts.

A molecule with a tert-butylamino group would fall outside claim 10 but may be addressed by claim 11. A sulfur or sulfone analogue would fall outside claim 10 but may be addressed by claims 7 or 9. A cyclobutyl analogue would fall outside claim 10 and would require separate analysis under the other claims.

The claim is composition-based. It does not depend on ophthalmic administration, concentration, preservative selection, container design, or glaucoma treatment. It therefore historically covered the active pharmaceutical ingredient across dosage forms, including oral, ophthalmic, and other pharmaceutical presentations, subject to the claim’s structural limitations.

What do claims 16 through 18 protect?

Claims 16 through 18 are method-of-use claims directed to selective beta-1 adrenergic receptor blockade.

Claim	Scope
16	Use of the specifically named cyclopropylmethoxy, isopropylamino compound to selectively block beta-1 receptors
17	Use of specified compounds from claims 1, 7, 8, 9, 10, or 11
18	Use of specified compounds from claims 12 through 15

These claims require more than administration of an arbitrary beta blocker. They require use of a compound within the identified structural class and a purpose involving selective beta-1 adrenergic receptor blockade.

The claims do not expressly recite glaucoma, ocular hypertension, hypertension, angina, arrhythmia, or heart failure. They are pharmacological method claims rather than indication-specific clinical treatment claims. A later product claim directed specifically to an ophthalmic composition or glaucoma treatment method would need to be analyzed separately.

The phrase “introducing into the environment of said receptors” is broad and unusual compared with modern patient-treatment claim language. It may encompass in vitro receptor assays, ex vivo systems, or administration to a biological system, depending on construction. It does not automatically establish infringement merely because a product has beta-1 blocking activity. The accused use must satisfy the claim’s method and purpose limitations.

When did U.S. Patent 4,311,708 lose exclusivity?

The patent’s ordinary term ended in 1999.

Event	Date or status
Patent issued	January 19, 1982
Applicable term regime	Pre-URAA, generally 17 years from issue
Ordinary expiration	January 19, 1999
Current blocking effect	None from unexpired claims
Present relevance	Prior-art, historical, validity, and portfolio analysis

The patent did not receive the modern 20-year-from-earliest-effective-filing-date term because it issued before the 1995 statutory transition. Patent-term restoration under the Hatch-Waxman framework generally applies to qualifying regulatory review periods, but it does not convert a pre-URAA patent into a later 20-year term. The relevant expiration analysis must still be checked against the official patent record for any terminal disclaimer, reissue, certificate of correction, or other unusual event.[3]

What is the Orange Book status of betaxolol?

Betaxolol ophthalmic products were approved by the FDA before the expiration of the foundational compound patent. FDA-approved products include Betoptic and later betaxolol ophthalmic formulations.

The Orange Book distinguishes between:

Approved drug products.
Listed patents submitted by the NDA holder.
Patent-use codes.
Generic applicants’ certification obligations.

The expiration of U.S. Patent 4,311,708 does not itself determine the current Orange Book status of every betaxolol ophthalmic product. The Orange Book listing must be assessed by NDA, strength, dosage form, and product version. A formulation patent, method-of-use patent, or later product patent could have had a different expiration date from the foundational compound patent.[4]

For a betaxolol ANDA, the practical questions were:

Whether the reference listed drug had any unexpired Orange Book patents.
Whether the ANDA applicant needed Paragraph IV certification.
Whether the proposed label carved out a patented method of use.
Whether the product used the same dosage form and formulation characteristics.
Whether any later patent covered a suspension, preservative system, or controlled-release presentation.

Because U.S. Patent 4,311,708 expired in 1999, it could not independently support a current Paragraph IV litigation campaign.

Are there Paragraph IV challenges to U.S. Patent 4,311,708?

A current Paragraph IV challenge to this patent would not be commercially meaningful because the patent is expired.

Paragraph IV certification is relevant to an unexpired patent listed in the Orange Book. The applicant certifies that the patent is invalid, unenforceable, or will not be infringed. Once the patent expires, the patent no longer creates a future market-exclusivity barrier, even though expired patents remain relevant to prior-art and invalidity analysis.

The commercial generic-entry risk for betaxolol therefore shifted from the foundational compound patent to:

Later formulation patents.
Product-specific ophthalmic patents.
Regulatory exclusivity.
Manufacturing know-how.
Preservative and delivery-system performance.
State or federal litigation unrelated to the expired compound patent.

What formulation patents protect betaxolol ophthalmic products?

The foundational patent does not claim a specific betaxolol ophthalmic formulation in the provided claims. It claims compounds, salts, and beta-1 receptor blocking methods.

Formulation protection, where available, would ordinarily address technical elements such as:

Betaxolol hydrochloride concentration.
Ophthalmic vehicle composition.
pH and buffering system.
Preservative selection.
Suspending agents.
Viscosity modifiers.
Particle size or suspension stability.
Multidose container design.
Preservative-free delivery.
Reduced irritation or improved ocular residence time.

Betoptic S, for example, is associated with a lower-concentration suspension presentation rather than the original 0.5% solution presentation. The patent analysis for that product must be conducted separately from U.S. Patent 4,311,708 and should focus on the later formulation and product patents listed for the relevant NDA, if any.[5]

An ANDA applicant could avoid a formulation claim by using a different preservative, buffer, vehicle, concentration, or physical presentation, provided the resulting product remains pharmaceutically equivalent and satisfies FDA requirements.

Does betaxolol face biosimilar risk?

No. Betaxolol is a small-molecule drug, not a biologic.

The relevant FDA pathway is an abbreviated new drug application under section 505(j) of the Federal Food, Drug, and Cosmetic Act, not a biosimilar application under section 351(k) of the Public Health Service Act.

Issue	Betaxolol
Product type	Small molecule
Primary generic pathway	ANDA
Biosimilar pathway	Not applicable
Reference standard	FDA reference listed drug
Core competition	Generic betaxolol ophthalmic products
Key regulatory issues	Pharmaceutical equivalence, bioequivalence or in vitro equivalence, sterility, ophthalmic quality

The absence of biosimilar risk does not eliminate manufacturing barriers. Sterile ophthalmic production requires validated aseptic processing, container-closure controls, particulate control, preservative efficacy, and stability data.

How strong is the patent estate for betaxolol?

The estate was strong during the compound patent’s active term because the patent combined broad genus claims with specific compound claims.

Strengths

Composition claims covered the active molecular class.
Claim 10 specifically covered betaxolol.
Pharmaceutically acceptable salts were included.
Method claims covered beta-1 receptor blockade.
The claims were not limited to a single dosage form.
The Markush structure covered oxygen, sulfur, and sulfone analogues.

Weaknesses

The patent is expired.
The formula images are essential to exact claim construction.
Claim 8 contains an apparent dependency inconsistency.
The method claims use broad pharmacological language.
The patent does not, based on the supplied claims, specifically claim modern ophthalmic formulations.
Later generic competition could avoid any unexpired formulation claim through design-around.

For present-day commercial analysis, the patent estate should be classified as a dead compound patent with possible residual relevance to historical ownership, prior-art review, and chain-of-title analysis.

How does betaxolol compare with competing beta blockers?

Drug	Receptor profile	Common ophthalmic role	Competitive distinction
Betaxolol	Relatively beta-1 selective	Ocular hypertension and glaucoma	Selectivity relative to nonselective agents
Timolol	Nonselective beta blocker	Major glaucoma therapy	Broad efficacy and established generic competition
Carteolol	Nonselective with intrinsic sympathomimetic activity	Ophthalmic use in some markets	Different pharmacology and market reach
Levobunolol	Nonselective beta blocker	Ophthalmic use	Competes on established ophthalmic efficacy
Metipranolol	Nonselective beta blocker	Ophthalmic use in selected markets	Smaller commercial footprint

Betaxolol’s commercial positioning depended on beta-1 selectivity, but selectivity did not create a separate regulatory exclusivity category. Once the compound patent expired, competition depended on approved formulations, physician preference, product availability, and payer substitution.

What licensing and ownership issues matter?

The patent’s commercial value depended on ownership and licensing arrangements involving the original patent applicant, the betaxolol developer, and later ophthalmic product sponsors. A complete licensing analysis requires the assignment history, recorded security interests, merger documents, and NDA ownership records.

For a transaction, the key diligence points are:

Chain of title from the original applicant.
Assignments recorded with the USPTO.
Any patent-family members outside the United States.
Regulatory ownership of the relevant NDA.
Orange Book patent submissions.
Settlement agreements involving later formulation patents.
Royalty obligations that survived patent expiration.
Know-how rights for sterile ophthalmic manufacture.

No royalty or license obligation can be inferred from the claims themselves. Patent expiration also does not automatically terminate a separate technology, trademark, manufacturing, or know-how license.

What geographic coverage did the patent provide?

U.S. Patent 4,311,708 provided rights only in the United States. Comparable protection in Europe, Japan, Canada, and other jurisdictions would depend on separate national patents or regional filings.

The U.S. expiration date did not determine foreign expiration dates. Foreign patents could have:

Different filing dates.
Different priority claims.
Different prosecution amendments.
Different patent-term adjustments.
Supplementary protection certificates.
Narrower or broader granted claims.
Earlier lapse for nonpayment of fees.

A global betaxolol freedom-to-operate review therefore requires a jurisdiction-by-jurisdiction family analysis. The U.S. patent cannot be treated as evidence that all foreign compound or formulation rights have expired.

What generic launch scenarios exist for betaxolol?

Scenario 1: Immediate generic entry based on expired compound protection

This is the basic scenario for the active ingredient. A manufacturer can pursue an ANDA without infringing the expired claims of U.S. Patent 4,311,708.

Scenario 2: Formulation-specific delay

A later formulation patent could delay or complicate approval for a product that copies a protected ophthalmic suspension, preservative system, or delivery platform. The applicant could respond with a Paragraph IV certification, a section viii labeling carve-out, or a design-around formulation.

Scenario 3: Manufacturing-based differentiation

A generic sponsor could use a different sterile filling process, container, preservative system, or suspension technology while maintaining pharmaceutical equivalence.

Scenario 4: Market-entry competition without patent barriers

Because betaxolol ophthalmic products compete with other generic beta blockers, the principal risks may be price erosion, limited market size, manufacturing concentration, and low-margin reimbursement rather than patent litigation.

Key Takeaways

U.S. Patent 4,311,708 is the foundational U.S. compound patent associated with betaxolol.
Claim 10 specifically covers the cyclopropylmethoxy, isopropylamino phenoxypropanolamine structure identified as betaxolol.
Claims 1 through 15 cover broader and narrower chemical analogues, including oxygen, sulfur, and sulfone derivatives.
Claims 16 through 18 cover beta-1 adrenergic receptor blocking methods.
The patent issued January 19, 1982 and ordinarily expired January 19, 1999.
The patent is not a current barrier to generic betaxolol entry.
Betaxolol is a small molecule subject to the ANDA pathway, not the biosimilar pathway.
Any current patent risk must be assessed through later formulation, delivery-system, manufacturing, or product-specific patents.
Claim 8 contains an apparent dependency conflict because it depends on a cyclopropyl-limited claim but names a cyclobutyl compound.
Foreign patent rights and licensing obligations cannot be determined from the U.S. claims alone.

Frequently Asked Questions

Is betaxolol hydrochloride covered by U.S. Patent 4,311,708?

Yes. Claim 10 covers the betaxolol free-base structure and expressly extends to pharmaceutically acceptable salts. Betaxolol hydrochloride is the principal pharmaceutical salt.

Can a generic manufacturer sell betaxolol without licensing the patent?

The expired U.S. compound patent does not require a license for current manufacture or sale. Separate licenses may still be relevant for trademarks, proprietary formulations, manufacturing technology, or later unexpired patents.

Does claim 16 cover treatment of glaucoma?

Claim 16 recites selective beta-1 adrenergic receptor blockade but does not expressly recite glaucoma or elevated intraocular pressure. Whether a glaucoma treatment infringes would depend on claim construction and the relationship between the prescribed use and the method limitations.

Is a cyclobutyl betaxolol analogue covered by claim 10?

No. Claim 10 identifies a cyclopropylmethoxy compound. A cyclobutyl analogue would not literally satisfy the cyclopropyl limitation, although it may be addressed by another claim or could raise an equivalents issue.

Does patent expiration eliminate all betaxolol market-exclusivity risk?

No. It eliminates the blocking effect of the claims in U.S. Patent 4,311,708. Later formulation patents, regulatory exclusivity, manufacturing rights, trademark rights, or foreign patents may create separate constraints.

References

U.S. Patent No. 4,311,708, “Substituted phenoxypropanolamines,” issued January 19, 1982. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (n.d.). Betaxolol hydrochloride ophthalmic labeling. FDA prescribing information and approved product labeling.
United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, Chapter 2700: Patent term. USPTO.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.
U.S. Food and Drug Administration. (n.d.). Betoptic and Betoptic S ophthalmic product labeling. FDA-approved prescribing information.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
France	75 33899	Nov 6, 1975

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	214303	⤷ Start Trial
Austria	344683	⤷ Start Trial
Austria	A812076	⤷ Start Trial
Australia	1925976	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,311,708

Summary for Patent: 4,311,708