US Patent 6,589,508: Scope, Claim Map, and US Landscape for (R,R)-Dominant Formoterol in Asthma

US Drug Patent 6,589,508 is directed to methods of treating asthma and related indications using formoterol enriched to at least 90% by weight (R,R)-formoterol and 10% or less (S,S)-formoterol, including pharmaceutically acceptable salts. The claims are method-of-use claims and are structured around: (i) the stereochemical composition, (ii) therapeutic administration, (iii) route, and (iv) inhaled daily dose ranges (with a specific embodiment tied to formoterol fumarate dihydrate).

What do the independent claim structures cover?

The patent uses three parallel method categories, each defined by the same active composition:

1) Asthma treatment (claim 1)
2) Bronchospasm treatment or prevention (claim 7)
3) Eliciting bronchodilation (claim 13)

Each independent claim is followed by dependent claims specifying route and dose and one or more embodiments specifying the salt form.

Claim-by-claim scope (what is covered and what is not)

Core active composition required

All asserted method claims require administering a therapeutic amount of:

Formoterol containing at least 90% by weight (R,R)-formoterol
10% or less by weight (S,S)-formoterol
or a pharmaceutically acceptable salt thereof

This means coverage is locked to stereochemical purity/enrichment. The claims do not cover:

racemic mixtures without the (R,R) dominance threshold,
(S,S)-dominant mixtures,
or general formoterol compositions unless they meet the defined ≥90% (R,R) and ≤10% (S,S) parameters.

Claim 1: treating asthma

Claim 1 is the foundational method-of-use:

“A method of treating asthma in human”
administering a therapeutically effective amount of the (R,R)-dominant formoterol composition or salt.

Coverage scope:

Applies to human asthma treatment.
Requires therapeutically effective amount (no fixed dosing limitation in claim 1).
No route limitation in claim 1.

Claims 2–6: route and inhalation dose and salt embodiment

Claim 2 adds route options:

Oral, transdermal, inhalation, subcutaneous injection, or intravenous infusion.

Claims 3–4 narrow the inhalation dose and specify a particular subrange:

Claim 3: inhalation at about 1 µg to 100 µg per day
Claim 4: inhalation at about 6 µg to 25 µg per day

Claims 5–6 specify salt:

comprises formoterol fumarate dihydrate

Practical reading:

If a product uses the required stereochemical composition and salt, and the dosing used for inhalation falls within the claimed ranges, it fits the dependent claims.
Outside these dose windows, claim coverage depends on whether the formulation and route still satisfy other claim dependencies (independent claim 1 remains broader on dose, but dependent claims narrow to inhalation dose).

Claims 7–12: bronchospasm treatment or prevention + route/dose/salt

Claim 7 is the second method-of-use:

method of treating or preventing bronchospasm in human
administering the same (R,R)-dominant formoterol composition or salt.

Claims 8–10 mirror claim 2–4:

route: oral, transdermal, inhalation, subcutaneous injection, intravenous infusion
inhalation daily dose: about 1–100 µg/day (claim 9)
further narrowed: about 6–25 µg/day (claim 10)

Claims 11–12 mirror claim 5–6:

comprises formoterol fumarate dihydrate

Claims 13–18: eliciting bronchodilation + route/dose/salt

Claim 13 is the third method-of-use category:

method of eliciting bronchodilation effect in a human
administering the same composition or salt.

Claims 14–16 mirror the same route and dose narrowing:

route options (claim 14): oral, transdermal, inhalation, subcutaneous injection, intravenous infusion
inhalation daily dose: 1–100 µg/day (claim 15)
further narrowed: 6–25 µg/day (claim 16)

Claims 17–18 specify salt again:

comprises formoterol fumarate dihydrate

What is the real “scope hinge”: the stereochemical composition

The claims consistently hinge on a single definitional limitation:

(R,R)-formoterol at ≥90% by weight
(S,S)-formoterol at ≤10% by weight

Everything else is layered on as method variables (asthma vs bronchospasm vs bronchodilation; route; and inhaled daily dose).

This structure signals that the patent’s novelty and enforceability are tied to the enriched stereoisomer composition, not novel delivery mechanics. Route and dose appear as narrowing embodiments rather than the core inventive definition.

Salt-form specificity (formoterol fumarate dihydrate)

Multiple dependent claims explicitly recite:

formoterol fumarate dihydrate (claims 5, 6, 11, 12, 17, 18)

That means:

The salt form is part of those specific narrower claims.
If a product uses a different pharmaceutically acceptable salt, it may still fit broader claims that say “pharmaceutically acceptable salt thereof,” but not necessarily the salt-specific dependent claims.

Inhalation dose architecture

The dependent claims create two inhalation daily-dose bands:

Broader inhalation band: about 1–100 µg/day (claims 3, 9, 15)
Narrower inhalation band: about 6–25 µg/day (claims 4, 10, 16)

Because claims 1/7/13 are not dose-limited, an accused product outside the inhalation bands can still theoretically fit an independent claim if the stereochemical composition and route used do not negate the route limitations (independent claims have no route limit). The dependent claims primarily strengthen coverage for typical asthma inhalation dosing patterns.

Does the patent cover prophylaxis vs treatment?

Yes, explicitly.

Claim 7 covers “treating or preventing bronchospasm.”
No prophylaxis word appears in claim 1 (asthma), but the composition and “method of treating asthma” still encompasses therapeutic regimens used to manage asthma.

How broad is the route coverage?

Dependent claims include five routes:

orally
transdermally
by inhalation
by subcutaneous injection
by intravenous infusion

There is no route excluded in the dependent claims. If an infringing formulation is stereochemically within spec, and the administration is for one of the claimed therapeutic purposes, the route is unlikely to be a carve-out.

Key design-around levers apparent from the claim language

Given the wording, the most direct non-infringement levers are composition-based rather than formulation-based:

Reduce (R,R) dominance below 90% by weight or increase (S,S) above 10% by weight so the stereochemical limitation is not met.
Use a different formoterol active where stereoisomer distribution does not satisfy the definitional percentages.

Dose-based avoidance has weaker traction because independent claims lack dose limits; dose manipulation mainly impacts dependent-claim strength.

Salt-based avoidance may matter for the dependent claims reciting formoterol fumarate dihydrate, but not for the base “pharmaceutically acceptable salt” language.

US patent landscape implications (composition-centric method-of-use)

A stereoisomer-enriched β2-agonist framework typically clusters around:

process and isolation of the enantiomeric fraction,
formulation and salt selection,
and method-of-use claims for respiratory indications.

US 6,589,508 is positioned in the landscape as a method-of-use enforcement vehicle where the active is defined by enantiomer composition rather than a device or specific inhalation technology.

In practice, that means potential infringement arguments in the US tend to focus on:

what fraction of (R,R) vs (S,S) is actually present in the administered drug (analytical specification and batch testing),
whether the product is a salt or free base that falls within “pharmaceutically acceptable salt,”
whether the labeled or used dosing regimens fall within or outside the dependent inhalation ranges.

Scope matrix (what each claim category covers)

Claim set	Indication	Required stereochemical composition	Route limits	Inhalation daily dose limits	Salt-specific
1	Treat asthma in human	≥90% (R,R) and ≤10% (S,S) (or salt)	None in claim 1	None	None
2–6	Treat asthma in human	Same	Oral, transdermal, inhalation, subQ, IV	1–100 µg/day (claim 3); 6–25 µg/day (claim 4)	Formoterol fumarate dihydrate (claims 5–6)
7	Treat or prevent bronchospasm	Same	None in claim 7	None	None
8–12	Treat or prevent bronchospasm	Same	Oral, transdermal, inhalation, subQ, IV	1–100 µg/day (claim 9); 6–25 µg/day (claim 10)	Formoterol fumarate dihydrate (claims 11–12)
13	Elicit bronchodilation effect	Same	None in claim 13	None	None
14–18	Elicit bronchodilation effect	Same	Oral, transdermal, inhalation, subQ, IV	1–100 µg/day (claim 15); 6–25 µg/day (claim 16)	Formoterol fumarate dihydrate (claims 17–18)

Patent-landscape “watch items” for investors and R&D

1) Analytical compliance with enantiomeric thresholds
The claims require composition-by-weight constraints. Any product positioned as “substantially enriched” must meet the explicit ≥90% / ≤10% limits to risk non-coverage.

2) Labeling and prescribed use
Even though the independent claims are broad on dose and route, infringement is still anchored to the therapeutic purpose: asthma treatment, bronchospasm treatment or prevention, or eliciting bronchodilation.

3) Salt selection strategy
The salt-specific dependent claims are narrower, but the base language includes “pharmaceutically acceptable salt thereof,” so simply switching salt may not avoid the independent claim set. It only reliably avoids the dependent salt-specific recitations.

4) Dose regimen targeting
Dose is most relevant to dependent claims (1–100 µg/day; 6–25 µg/day for inhalation). If dose regimens land outside these windows, the dependent-claim read weakens, while independent claims still remain.

Key Takeaways

US 6,589,508 is a composition-defined, method-of-use patent: it requires formoterol with ≥90% (R,R)-formoterol and ≤10% (S,S)-formoterol (or a pharmaceutically acceptable salt).
The claims cover three respiratory therapeutic purposes in humans: asthma treatment, bronchospasm treatment or prevention, and eliciting bronchodilation.
Dependent claims add route (oral, transdermal, inhalation, subQ, IV) and inhalation daily dose windows (about 1–100 µg/day and about 6–25 µg/day).
Dependent claims also specify formoterol fumarate dihydrate in multiple claim branches (5–6, 11–12, 17–18).
Practical non-infringement is likely composition-based: avoiding the ≥90% (R,R) / ≤10% (S,S) threshold is the cleanest lever because independent claims are not dose-limited.

FAQs

1) What is the active-ingredient requirement in US 6,589,508?

The method requires administering formoterol containing at least 90% by weight (R,R)-formoterol and 10% or less by weight (S,S)-formoterol, or a pharmaceutically acceptable salt of that composition.

2) Does the patent limit the claims to inhalation delivery?

No. Dependent claims list inhalation among multiple routes, including oral, transdermal, subcutaneous, and intravenous. Independent claims do not impose a route limitation.

3) What inhalation dose ranges appear in the claims?

Two dependent inhalation daily dose bands appear: about 1–100 µg/day and about 6–25 µg/day.

4) Is formoterol fumarate dihydrate required?

No, only in the salt-specific dependent claims. Several dependent branches require formoterol fumarate dihydrate, while other claims allow “pharmaceutically acceptable salt thereof.”

5) What indications are explicitly claimed?

Asthma treatment, bronchospasm treatment or prevention, and eliciting bronchodilation effect.

References

[1] United States Patent 6,589,508.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	9107196	Apr 05, 1991

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: 6,589,508

Summary for Patent: 6,589,508