Details for Patent: 5,766,573

Summary for Patent: 5,766,573

Title:	Medicinal aerosol formulations
Abstract:	A self-propelling aerosol formulation which may be free from CFC's which comprises a medicament, 1,1,1,2-tetrafluoroethane, a surface active agent and at least one compound having a higher polarity than 1,1,1,2-tetrafluoroethane.
Inventor(s):	Tarlochan S. Purewal, David J. Greenleaf
Assignee:	3M Innovative Properties Co
Application Number:	US08/783,737
Patent Claim Types: see list of patent claims	Use; Formulation; Delivery;

United States Patent 5,766,573 (Method for Lung Delivery Using HFA-134a Aerosol Propellant): Scope, Claim Construction, and US Patent Landscape

Executive summary: US Patent 5,766,573 is directed to a method of delivering an inhalable aerosol formulation from a pressurized aerosol container with a metering valve using a propellant that is essentially free of chlorofluorocarbons and comprises 1,1,1,2-tetrafluoroethane (HFA-134a). Claim scope is driven by (1) the delivery method (lung inhalation from a metered aerosol), (2) the propellant composition restriction (CFC-free and containing HFA-134a), and (3) optional formulation add-ons (specific cosolvents/emollients) and medicament recitations (a defined set of respiratory drugs). The landscape is shaped by the broader “CFC-to-HFA” reformulation and delivery-method patent clusters, where infringement risk often hinges on whether the accused product uses HFA-134a (alone or in the required “comprising” sense) in a metered inhaler aerosol delivering lung-targeted medicament.

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What does US Patent 5,766,573 claim and what is the scope of protection?

Core idea: The patent claims a delivery method defined by the propellant identity and delivery hardware (aerosol container with metering valve) for a formulation that is suitable for lung inhalation.

Claim 1: Method scope that is triggered by “HFA-134a in a CFC-free propellant”

Claim text (paraphrased for scope):
A method of delivering an aerosol formulation containing a medicament from an aerosol container with a metering valve, where the formulation is suitable for lung delivery by inhalation, the improvement being that the formulation uses a propellant essentially free of chlorofluorocarbons and comprising 1,1,1,2-tetrafluoroethane (HFA-134a).

Key scope-defining limitations

1. Delivery system: “aerosol container equipped with a metering valve”
   • This targets pressurized metered-dose inhaler (pMDI)-type systems.
2. Route and suitability: formulation “suitable for delivery to the lung by inhalation from said container”
   • This is a use/fitness limitation tied to the intended pulmonary delivery of a medicament via inhalation.
3. Propellant restriction (the main enforceable hook):
   • “essentially free of chlorofluorocarbons”
   • “comprising 1,1,1,2-tetrafluoroethane” (HFA-134a)

Interpretation consequences (practical):

• The use of HFA-134a is central. If the propellant does not contain HFA-134a, Claim 1 is not met.
• If the formulation contains HFA-134a and is essentially CFC-free, the claim is likely implicated even if other non-CFC components are present, because Claim 1 uses “comprising,” not “consisting of.”
• “Essentially free of chlorofluorocarbons” is a compositional cleanliness qualifier. A product with de minimis or trace CFC contamination could still be argued as “essentially free,” but the claim is strongest against commercial products marketed/produced as CFC-free.

Claim 2: Narrower scope adding specific cosolvents/emollients

Claim 2 adds: the improvement further comprises use of a compound selected from:

• ethyl alcohol
• isopropyl alcohol
• n-pentane
• isopentane
• neopentane
• isopropyl myristate

Scope effect: Claim 2 is a subset of Claim 1. It captures products whose HFA-134a-based formulation additionally includes one of the listed compounds as a formulation component.

Claim 3: Narrower medicament list

Claim 3 specifies that the medicament is one of:

• salbutamol
• beclomethasone dipropionate
• disodium cromoglycate
• pirbuterol
• isoprenaline
• adrenaline
• rimiterol
• ipratropium bromide

Scope effect: Claim 3 is a subset of Claim 1 and 2. If a product uses HFA-134a and fits the aerosol metering/lung delivery method, Claim 3 is implicated only when the medicament is within the recited list.

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How do US claims 1-3 read on metered-dose inhalers vs other aerosol delivery systems?

Hardware limitation: “aerosol container equipped with a metering valve”

This language is aligned to pressurized metered-dose delivery where a valve delivers a dose upon actuation.

Systems more likely to match

• pMDIs using canisters and metering valves
• breath-actuated or manually actuated pMDI architectures that still use a metering valve

Systems less likely to match

• nebulizers that do not use a metering valve in the same sense
• dry powder inhalers where propellant is not used as the aerosol formation mechanism
• soft mist inhalers without a metering-valve canister architecture (depending on structure)

Formulation suitability language

“Suitable for delivery to the lung by inhalation” is broad enough to cover formulations developed for pulmonary delivery, even if the medicament is not directly tested inside the claim language.

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What patents protect HFA-134a, CFC-free aerosol propellants, and lung inhalation delivery methods in the US?

Because the topic is CFC replacement and HFA reformulation, the US patent estate typically clusters into three adjacent families:

1. Propellant composition and CFC-free claims (including HFA-134a)
2. Aerosol formulation and cosolvent selection (alcohols, alkanes, esters)
3. Delivery methods and device systems (metered valves, canister architectures, dose uniformity methods)

Directly tied to 5,766,573:

• The method claim is anchored in HFA-134a presence plus CFC-free plus metered aerosol lung delivery.
• Claim 2 anchors the cosolvent/cosupport list.
• Claim 3 anchors a medicament list that is heavily represented in respiratory inhalation portfolios (beta-agonists, anticholinergics, steroids).

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What is the effective infringement risk for products using HFA-134a vs HFA-227 (and mixed blends)?

HFA-134a as a “comprising” limitation

Claim 1 requires a propellant “comprising” HFA-134a. This typically means:

• The propellant can be a mixture that includes HFA-134a plus other components that are not chlorofluorocarbons (subject to the “essentially free” qualifier).
• The presence of HFA-134a is the gating factor.

Products using only HFA-227ea (1,1,1,2-tetrafluoroethane is not the same)

• If the propellant is not HFA-134a, Claim 1 is unlikely to read.
• The patent is not a generic “HFA-based inhalation” claim; it is tied to tetrafluoroethane specifically.

Mixed propellant systems

For products that use propellant blends including HFA-134a:

• If the blend is essentially CFC-free, the method claim is more likely to be asserted.
• If CFC contamination is present above “essentially free” boundaries, the claim is potentially avoidable, though modern commercial production typically targets CFC-free status.

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How many claim pathways are there to practice infringement under US 5,766,573?

Based on independent structure:

Pathway A (broadest)

• Claim 1: metered aerosol container + lung-inhalation suitability + medicament formulation + propellant essentially CFC-free + propellant comprises HFA-134a.

Pathway B (intermediate)

• Claim 2 in addition to Claim 1: the formulation includes one of the enumerated additives (ethyl alcohol, isopropyl alcohol, n-pentane, isopentane, neopentane, isopropyl myristate).

Pathway C (narrowest)

• Claim 3 in addition to Claim 1: medicament is one of the listed respiratory agents.

In practice, infringement arguments often focus on Claim 1, then use Claim 2 and 3 as alternative or reinforcing theories depending on the specific product label and formulation composition.

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How strong is US 5,766,573 relative to typical CFC-to-HFA reformulation patents?

Strength drivers

• Single enforceable propellant identity: Claim 1’s HFA-134a requirement narrows the universe but increases technical clarity for claim-mapping.
• Hardware + propellant + lung delivery: three independent categories of limitations reduce the plausibility of accidental coverage.
• Cosolvent list in Claim 2: adds formulation specificity that can be used to differentiate among competing HFA-134a products.

Potential weakness drivers

• Medicaments are limited in Claim 3: if the accused product uses a non-enumerated medicament, only Claim 1 may apply.
• “Essentially free of chlorofluorocarbons”: can become a factual/technical dispute about acceptable residual CFC levels.

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What claim-mapping details matter most for an HFA-134a inhaler product?

1) Propellant assay and specification

Infringement analysis turns on whether the canister propellant:

• contains HFA-134a
• is “essentially free” of chlorofluorocarbons (CFCs)

2) Formulation excipients matching Claim 2

If the product includes any of:

• ethyl alcohol, isopropyl alcohol
• n-pentane, isopentane, neopentane
• isopropyl myristate
  then Claim 2 becomes a likely add-on hook.

3) Medicament identity matching Claim 3

If the product is for:

• salbutamol, beclomethasone dipropionate, disodium cromoglycate, pirbuterol, isoprenaline, adrenaline, rimiterol, ipratropium bromide
  then Claim 3 can be asserted.

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What is the US regulatory context for CFC-free HFA-134a inhalers relevant to patent landscape?

Orange Book status and FDA labeling linkage

For method patents tied to propellants and delivery systems, the practical enforcement pathway in the US typically follows:

• product approval in a relevant NDA/ANDA/BLA framework
• listing and exclusivity in the Orange Book when applicable
• patent challenges (Paragraph IV for ANDAs; biosimilar pathways for biologics, not directly implicated here)

Method claims like those in 5,766,573 can be asserted against approved pMDIs whose composition and use map to the claim limitations.

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What generic entry risks exist for HFA-134a-based inhalers under this patent?

If a generic follows the same HFA-134a propellant and metered valve delivery

• A generic that uses HFA-134a in a CFC-free formulation for lung inhalation via metered valves creates a direct mapping risk under Claim 1.
• If the generic also uses one of the Claim 2 listed excipients, additional risk increases.

If a generic switches propellant to HFA-227ea

• The core “comprising 1,1,1,2-tetrafluoroethane” limitation becomes non-infringing on its face.

If a generic changes medicament (different labeled drug)

• Claim 3 may drop away, but Claim 1 can still apply if the medicament is still an inhalable medicament and the propellant identity and delivery method limitations are met.

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Which competing products are most likely to fall within Claim 1 or Claim 3?

Claim 3 medicament list defines the closest enforcement targets:

• salbutamol (albuterol) inhalation products in pMDI form using HFA-134a
• beclomethasone dipropionate inhalation pMDIs
• ipratropium bromide inhalers
• disodium cromoglycate and selected beta-agonists/adrenaline analogs in HFA-134a aerosol forms

Claim 1 is broader and can apply to other medicaments if the product is a lung-inhalation aerosol from a metered container using HFA-134a and essentially CFC-free propellant. The medicament list only narrows Claim 3, not Claim 1.

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How does the claim scope compare with adjacent aerosol propellant patents?

In most CFC-to-HFA landscapes, adjacent patents include:

• claims on HFA-134a-containing propellants generally
• claims on formulation components for stability, droplet size, and delivery consistency
• claims on device or metering mechanisms
• claims on delivery methods that are either:
  • generic (“administer to the lung”)
  • or tied to specific propellant/excipient combinations

US 5,766,573’s differentiator is the combination of:

• metered aerosol lung delivery method
• CFC-free propellant
• HFA-134a specifically
  This combination makes it less likely to be rendered redundant by broader “administer to lung” patents that do not constrain the propellant identity.

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Patent landscape: litigation and licensing posture around HFA-134a aerosol methods

Without verified litigation/assignment records for US 5,766,573 in the prompt, no defensible statement can be made about:

• specific defendants/plaintiffs
• settlement structures
• Paragraph IV carveouts tied to this exact patent
• which co-owned families were asserted in court

Accordingly, the analysis here focuses strictly on the claim scope and how infringement typically maps in this technology space.

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Key Takeaways

• US 5,766,573 is a method claim centered on metered aerosol containers delivering lung-inhalable medicaments using a propellant essentially free of CFCs and comprising HFA-134a (1,1,1,2-tetrafluoroethane).
• Claim 1 is the primary coverage hook: it is driven by HFA-134a presence and CFC-free propellant in an aerosol pMDI-type system.
• Claim 2 narrows coverage to formulations containing one of six enumerated additives (alcohols, specific alkanes, or isopropyl myristate).
• Claim 3 further narrows to eight specific medicaments (including salbutamol, beclomethasone dipropionate, and ipratropium bromide).
• Generic entry risk is highest for products that keep HFA-134a and maintain CFC-free propellant standards; risk drops if propellant is switched to HFA-227ea (not HFA-134a).
• The patent’s enforceability in practice turns on propellant composition evidence and formulation/excipient disclosures.

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FAQs

1. Does US 5,766,573 cover inhalers that use HFA-134a with an additional non-CFC co-propellant?
   Yes, because Claim 1 uses “comprising” HFA-134a, subject to the “essentially free of chlorofluorocarbons” qualifier.

2. What excipients trigger added risk under Claim 2 of US 5,766,573?
   Ethyl alcohol, isopropyl alcohol, n-pentane, isopentane, neopentane, and isopropyl myristate.

3. If a product’s medicament is not on the Claim 3 list, can it still infringe?
   Yes, because Claim 1 does not restrict the medicament to the Claim 3 enumerated list.

4. Would changing from a metered-dose inhaler to a nebulizer avoid Claim 1?
   Likely, because Claim 1 requires an aerosol container “equipped with a metering valve.”

5. Is “essentially free of chlorofluorocarbons” a composition-only limitation or does it incorporate manufacturing controls?
   It reads as a compositional limitation tied to propellant content, though infringement analysis typically uses formulation and propellant assay evidence.

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References (APA)

1. User-provided claim text for US Patent 5,766,573 (claims 1-3).

Drugs Protected by US Patent 5,766,573

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

International Family Members for US Patent 5,766,573

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	4595689
Australia	631155
Canada	2004598