US Patent 5,795,564: Scope, Claims, Expiration, and Formoterol Patent Landscape

US Patent No. 5,795,564 protected the use and formulation of substantially pure (R,R)-formoterol, now known as arformoterol, for bronchodilation. Its central distinction was stereochemical purity: at least 99% by weight (R,R)-formoterol and less than 1% (S,S)-formoterol.

The patent issued on August 18, 1998, to Sepracor Inc. Its principal US patent term expired on August 18, 2015, based on the pre-URAA 17-year term from issuance, absent any term adjustment or extension. The patent is therefore no longer an enforceable barrier to generic development. Its claims remain important for understanding the historical origin of arformoterol, Brovana, and related inhaled bronchodilator products.

What drug and technology does US Patent 5,795,564 cover?

US 5,795,564 covers the therapeutic use of the purified (R,R) enantiomer of formoterol rather than racemic formoterol.

Formoterol has two relevant stereoisomers:

Compound	Description	Therapeutic relevance
(R,R)-formoterol	The substantially purified active enantiomer, also called arformoterol	Long-acting beta-2 adrenergic bronchodilator
(S,S)-formoterol	The opposite enantiomer	Associated with the patent's claimed hypersensitivity distinction
Racemic formoterol	Mixture of stereoisomers	Used in products such as formoterol fumarate inhalation products

The patent claims a product containing at least 99% (R,R)-formoterol and less than 1% (S,S)-formoterol. The claims also cover pharmaceutically acceptable salts, particularly formoterol fumarate dihydrate.

The claimed products and uses include:

Bronchodilation;
Treatment or alleviation of bronchospasm;
Inhaled administration;
Oral administration;
Subcutaneous injection;
Intravenous infusion;
Transdermal delivery;
Tablets;
Capsules;
Aerosols;
Transdermal patches.

How many independent claims does US 5,795,564 have?

The supplied claims contain four independent claims: claims 1, 8, 14, and 15.

Independent claim	Claim category	Core limitation
Claim 1	Method of treatment	Administering highly purified (R,R)-formoterol to produce bronchodilation while avoiding hypersensitivity
Claim 8	Composition	Tablet, capsule, patch, or aerosol containing highly purified (R,R)-formoterol
Claim 14	Method of treatment	Producing a bronchodilator effect more than twice as long as a comparable dose of racemic formoterol
Claim 15	Method of treatment	Producing a bronchodilator effect longer than a comparable dose of racemic formoterol

Claims 2 through 7 depend from claim 1. Claims 9 through 13 depend from claim 8.

The patent therefore has two principal claim groups:

Purified (R,R)-formoterol as a treatment method; and
Dosage forms containing purified (R,R)-formoterol.

What does claim 1 protect?

Claim 1 is the patent's primary therapeutic claim. It requires all of the following:

A human patient in need of bronchodilation;
Administration of (R,R)-formoterol or a pharmaceutically acceptable salt;
An amount sufficient to alleviate bronchospasm;
An amount insufficient to cause hypersensitivity;
At least 99% by weight (R,R)-formoterol;
Less than 1% by weight (S,S)-formoterol.

The claim is narrower than a general claim to formoterol. It requires a particular stereochemical composition and a therapeutic administration step.

A product containing racemic formoterol would not satisfy the express purity limitation. A product containing 98% (R,R)-formoterol and 2% (S,S)-formoterol would also fall outside the literal percentage limitation. A product containing 99.5% (R,R)-formoterol and 0.5% (S,S)-formoterol would meet the stated stereochemical threshold, assuming the remaining material does not alter claim interpretation.

The claim does not specify a single disease. It is directed to bronchodilation and relief of bronchospasm. Potentially relevant conditions include asthma, chronic obstructive pulmonary disease, reversible airway obstruction, and other bronchospastic disorders, although infringement would depend on the accused use and the required treatment facts.

What dosage forms and doses are covered?

The dependent claims identify broad delivery routes and specified dose ranges.

Claim	Route or dosage form	Claimed range or limitation
2	Injection, infusion, inhalation, transdermal, or oral	Route-specific administration
3	Inhalation	About 1 to about 100 micrograms per day
4	Oral	About 0.1 to about 1 mg per day
5	Pharmaceutical carrier	Carrier-compatible formulation
6	Salt form	(R,R)-formoterol fumarate dihydrate
7	Inhalation dosing frequency	Divided doses two to four times daily
8	Tablet, capsule, patch, or aerosol	Composition claim
9	Inhalation composition	About 6 to about 25 micrograms
10	Inhalation salt form	(R,R)-formoterol fumarate dihydrate
11	Oral composition	Oral dosage form
12	Oral dosage	About 0.1 to about 1 mg
13	Transdermal composition	Patch or other transdermal product

The dose ranges are not identical across the claims. Claim 3 covers an inhaled daily dose of approximately 1 to 100 micrograms, while claim 9 narrows an inhaled composition to approximately 6 to 25 micrograms. The composition claim is therefore more commercially aligned with a unit-dose inhalation product than the broader method claim.

The patent does not require a particular nebulizer, inhaler, propellant, excipient, particle size, container, or device architecture in the supplied claims. Those limitations could matter in evaluating infringement of a specific product, but they are not express elements of the quoted claims.

What do claims 14 and 15 protect?

Claims 14 and 15 are comparative-duration claims.

Claim 14 requires that the (R,R)-formoterol treatment produce a bronchodilator effect more than twice the duration of a comparable dose of racemic formoterol.

Claim 15 requires a bronchodilator effect of longer duration than a comparable dose of racemic formoterol, without requiring the duration to exceed twice the racemate's duration.

Feature	Claim 14	Claim 15
Highly purified (R,R)-formoterol	Required	Required
Bronchodilation	Required	Required
Comparison with racemic formoterol	Required	Required
Longer duration than racemate	Required	Required
More than twice the duration	Required	Not required

These claims create proof issues in an infringement dispute. The patent owner would need to establish the relevant comparator dose, administration conditions, patient population, endpoint used to measure bronchodilation, and duration of effect. "Comparable dose" and "duration" may require construction based on the specification, prosecution history, and scientific evidence.

A generic or follow-on company could challenge these claims by arguing that the comparative limitation is indefinite, insufficiently reproducible, or not met by the accused product. The strength of that argument would depend on the patent specification and the prosecution record, not only on the claim text.

How broad is the stereochemical limitation?

The 99% and 1% thresholds are central to every independent claim in the supplied claim set.

The claims distinguish the protected material from:

Racemic formoterol;
Partially enriched formoterol mixtures;
Material containing 1% or more (S,S)-formoterol;
Products that contain the wrong stereoisomer as a meaningful impurity.

The claims expressly limit the amount of (S,S)-formoterol but do not state a general 1% maximum for every possible impurity. A composition could contain other impurities without automatically failing the literal stereochemical limitation, although the meaning of "at least 99% by weight of (R,R)-formoterol" would need to be calculated against the relevant composition basis.

Analytical testing would be critical. Enantiomeric purity can depend on the assay method, reference standard, sample preparation, and whether the percentage is measured on an active-ingredient basis or total formulation basis.

What is the patent's relationship to arformoterol and Brovana?

Arformoterol is the pharmaceutical name commonly used for the (R,R) enantiomer of formoterol. Brovana is arformoterol tartrate inhalation solution, approved by the FDA for long-term maintenance treatment of bronchoconstriction in patients with chronic obstructive pulmonary disease.

US 5,795,564 is technically relevant to Brovana because it claims:

The purified (R,R) active ingredient;
Inhaled administration;
Bronchodilator treatment;
Formoterol salts;
Inhaled dose ranges;
Compositions containing the purified enantiomer.

The marketed product, however, must be analyzed against the complete regulatory and patent record. A product's FDA approval, labeling, formulation, manufacturing process, container system, and listed patents may involve later patents that are distinct from US 5,795,564.

When did US 5,795,564 lose exclusivity?

The patent's ordinary US term expired in 2015.

Event	Date
Patent issued	August 18, 1998
Ordinary pre-URAA term	17 years from issuance
Expected expiration	August 18, 2015
Current enforceability	Expired

The expiration of US 5,795,564 does not eliminate later patent rights covering arformoterol formulations, inhalation solutions, manufacturing processes, devices, or treatment regimens. A generic company therefore must conduct a separate freedom-to-operate review of later patents and regulatory listings.

The patent also did not create permanent exclusivity over the arformoterol molecule. Once the patent expired, the claimed purification level, administration methods, and dosage forms became available for use subject to other unexpired rights.

What was the Orange Book status of US 5,795,564?

US 5,795,564 should not be treated as a current Orange Book barrier for Brovana.

The FDA Orange Book lists patents submitted by an NDA holder for an approved drug product. A patent may be absent because it was never listed, because it was not considered listable, because the relevant NDA changed, or because the listing expired or was removed. Patent expiration also prevents the patent from operating as a current exclusion right.

For a current arformoterol or Brovana analysis, the relevant review should separate:

US 5,795,564;
Patents listed for Brovana in the current Orange Book;
Later patents assigned to Sepracor, Sunovion, or other rights holders;
Patents covering arformoterol tartrate inhalation solution;
Device, container, formulation, and manufacturing patents;
Regulatory exclusivity periods associated with the approved NDA.

The supplied patent is not a current Paragraph IV obstacle solely because it covers the same active moiety.

Were there Paragraph IV challenges or generic-entry disputes?

Any Paragraph IV analysis must focus on later, unexpired patents listed for the relevant arformoterol product. An ANDA applicant could challenge US 5,795,564 historically, but a Paragraph IV certification to an expired patent would not normally be the operative basis for blocking current generic entry.

The principal generic-entry theories after expiration of the patent would include:

Non-infringement of later formulation claims;
Invalidity for anticipation or obviousness;
Lack of written description;
Lack of enablement;
Ineligibility of a patent for Orange Book listing;
Failure of the branded product to establish a valid patent-listing basis;
Design-around of device, concentration, excipient, or container limitations.

No current litigation conclusion should be attributed to US 5,795,564 without a docket-specific review. The patent itself expired before the current generic arformoterol market developed.

What are the principal validity vulnerabilities?

The most material validity and enforcement issues are claim construction and proof, rather than the existence of the active ingredient itself.

Purity and measurement

The 99% and less-than-1% limitations require a reliable method for measuring enantiomeric composition. A dispute could arise over:

The analytical method;
Detection limits;
Reference standards;
Lot-to-lot variation;
Whether the claim measures the active ingredient or the complete dosage form.

Functional hypersensitivity language

Claim 1 requires an amount sufficient to alleviate bronchospasm but insufficient to cause hypersensitivity. The phrase may be interpreted as a functional treatment limitation. It does not state a universal numerical hypersensitivity threshold.

An accused product could challenge whether the limitation is definite and whether the required result is attributable to the claimed stereochemical composition.

Comparative duration

Claims 14 and 15 depend on comparison with racemic formoterol. The comparison must be scientifically reproducible. Relevant variables include dose, route, patient population, baseline lung function, endpoint, and observation period.

Obviousness

The patent's central inventive concept is the use of an optically pure enantiomer of a known racemic bronchodilator. An obviousness analysis would examine:

Prior disclosures of formoterol stereochemistry;
Methods for resolving or synthesizing the enantiomers;
Known pharmacological differences between enantiomers;
Motivation to reduce exposure to the opposite enantiomer;
Unexpected duration or safety results;
The predictability of the claimed therapeutic effects.

Written description and enablement

The claims cover several routes, dosage forms, salts, and dose ranges. The enforceability of the broadest claims would depend on whether the specification adequately supports and enables the full scope, particularly oral, intravenous, subcutaneous, and transdermal embodiments.

How does this patent compare with racemic formoterol patents?

Issue	US 5,795,564	Racemic formoterol patents
Active ingredient	Purified (R,R)-formoterol	Mixture of formoterol stereoisomers
Purity threshold	At least 99% (R,R), less than 1% (S,S)	Generally not based on single-enantiomer purity
Therapeutic focus	Bronchodilation with reduced hypersensitivity and longer duration	Long-acting bronchodilation
Product forms	Tablet, capsule, aerosol, patch, salt	Inhalation formulations and devices
Comparative duration claim	Yes, claims 14 and 15	Usually not directed to R,R versus racemate
Current status	Expired	Depends on the individual patent
Commercial product association	Arformoterol and Brovana	Foradil, Perforomist, and combination products

A generic racemic formoterol product does not necessarily infringe a claim requiring at least 99% (R,R)-formoterol. Conversely, a generic arformoterol product may avoid this expired patent but still face later patents on formulation, concentration, container closure, nebulizer delivery, or manufacturing.

What manufacturing and IP barriers remain after expiration?

The expired patent removed one major composition and use barrier but did not eliminate all commercial barriers.

Relevant remaining barriers may include:

Enantiomeric purification or asymmetric synthesis;
Control of (S,S)-formoterol levels;
Salt formation and crystallization;
Formoterol fumarate or tartrate solid-state properties;
Inhalation-solution stability;
Sterile manufacturing;
Unit-dose packaging;
Nebulizer compatibility;
Extractables and leachables;
FDA chemistry, manufacturing, and controls requirements;
Later formulation or process patents;
Approved-product bioequivalence requirements.

For an inhalation solution, regulatory development can be more difficult than for a conventional oral generic because the applicant must control delivered dose, droplet or aerosol performance, container compatibility, sterility where applicable, and device performance.

What is the commercial exposure associated with this patent?

US 5,795,564 had its greatest commercial value before expiration because it covered the purified active ingredient and broad therapeutic use. Its commercial relevance was linked to arformoterol products for COPD maintenance therapy, particularly Brovana.

After expiration, the patent's direct revenue protection fell to zero as a matter of statutory patent exclusivity. The commercial exposure shifted to later patents, FDA exclusivity, manufacturing know-how, product quality, and market access.

The patent did not protect every formoterol product. Its strongest historical position was against products using highly purified (R,R)-formoterol for bronchodilation. Its weakest position was against racemic formoterol, products outside the claimed purity thresholds, and products that did not practice the claimed therapeutic or dosage-form limitations.

Key Takeaways

US 5,795,564 covers purified (R,R)-formoterol, or arformoterol, for bronchodilation.
The core purity limitation is at least 99% (R,R)-formoterol and less than 1% (S,S)-formoterol.
The patent claims therapeutic methods, inhaled and oral doses, pharmaceutical compositions, salts, and multiple delivery routes.
Claims 14 and 15 add comparative duration limitations against racemic formoterol.
The patent issued on August 18, 1998, and its ordinary term expired on August 18, 2015.
It is not a current standalone barrier to generic arformoterol entry.
Later patents, Orange Book listings, formulation rights, device patents, manufacturing patents, and FDA requirements may still affect generic launch.
The most significant historical enforcement issues concern purity testing, hypersensitivity language, comparative duration, and the scope of support for broad delivery-route claims.
Current Paragraph IV risk must be assessed against later patents associated with the relevant arformoterol product, not against this expired patent alone.

FAQs About US Patent 5,795,564 and Arformoterol

Is US 5,795,564 still enforceable?

No. The patent's ordinary US term expired on August 18, 2015.

Does US 5,795,564 cover racemic formoterol?

No. The quoted claims require at least 99% (R,R)-formoterol and less than 1% (S,S)-formoterol.

Is arformoterol the same as (R,R)-formoterol?

Yes. Arformoterol is the pharmaceutical name commonly used for the (R,R) enantiomer of formoterol.

Does the patent cover Brovana?

The claims are technically relevant to Brovana because Brovana contains arformoterol. The expired patent alone does not establish current exclusivity for Brovana.

Can a generic arformoterol product launch after expiration of this patent?

Yes, subject to later unexpired patents, FDA requirements, regulatory exclusivity, product-specific Orange Book listings, and successful approval of the generic or other follow-on application.

References

United States Patent and Trademark Office. (1998). US Patent No. 5,795,564: Method of treating respiratory disorders with (R,R)-formoterol.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2006). Brovana (arformoterol tartrate) inhalation solution prescribing information.
U.S. Food and Drug Administration. (2019). Hatch-Waxman amendments and abbreviated new drug applications.
United States Code, 35 U.S.C. § 154. (2024). Contents and term of patent; provisional rights.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Belgium	1005778	⤷ Start Trial
Canada	2065051	⤷ Start Trial
Switzerland	685672	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,795,564

Summary for Patent: 5,795,564