United States Patent 8,658,205: Claim Scope, Definity Formulation Coverage, and Patent Landscape

U.S. Patent No. 8,658,205 covers a narrowly defined perfluoropropane ultrasound-contrast formulation containing DPPA, DPPC, and MPEG5000-DPPE in a 10:82:8 molar ratio, together with sodium chloride, glycerin, propylene glycol, water, and approximately 0.75 mg/mL of the lipid mixture. The claim is directed to a finished composition, not to DPPA, DPPC, MPEG5000-DPPE, or perfluoropropane individually.

What product does U.S. Patent 8,658,205 appear to cover?

The claimed formulation corresponds closely to the excipient and gas system used in Definity, an FDA-approved perflutren lipid microsphere ultrasound contrast agent marketed by Lantheus Medical Imaging. The FDA label identifies Definity as a microsphere product containing perflutren gas encapsulated by a lipid shell and supplied for intravenous use in echocardiography and other ultrasound imaging applications.[1]

The claim identifies the following formulation:

Component	Claimed requirement	Functional role
DPPA, monosodium salt	10 mol%	Lipid-shell component
DPPC	82 mol%	Primary phospholipid-shell component
MPEG5000-DPPE, monosodium salt	8 mol%	PEGylated phospholipid stabilizer
Total lipid	About 0.75 mg/mL	Lipid concentration
Sodium chloride	Required	Isotonicity and formulation control
Glycerin	About 0.1 mL/mL	Tonicity and stabilization
Propylene glycol	About 0.1 mL/mL	Solvent and formulation aid
Water	Required	Continuous phase
Perfluoropropane	Required	Encapsulated ultrasound-scattering gas

The claim uses the chemical name "1,2-dipalmitoyl-sn-glycero-3-phosphotidic acid" for DPPA. "Phosphatidic" is the conventional spelling. The spelling error does not necessarily remove DPPA from the claim if the identity of the compound is clear from the specification, prosecution history, or technical context.

What is the legal scope of claim 1?

Claim 1 is a composition claim with several cumulative limitations. A product must satisfy each material limitation to fall within the literal scope of the claim.

The claim requires three specified lipids

The formulation must contain:

DPPA, monosodium salt;
DPPC; and
MPEG5000-DPPE, monosodium salt.

A formulation using a different phosphatidic acid, a different phosphatidylcholine, or a different PEG-lipid would present a literal-infringement issue because the claim names specific chemical species rather than broad lipid classes.

For example, replacing DPPC with DSPC, substituting a PEG chain other than approximately 5,000 molecular weight, or using a non-sodium salt could avoid literal satisfaction of the relevant limitation. Whether such substitutions could implicate the doctrine of equivalents would depend on prosecution history, claim construction, and the technical effect of the substitution.

The 10:82:8 molar ratio is a central limitation

The claim requires DPPA, DPPC, and MPEG5000-DPPE in a mole ratio of 10% to 82% to 8%. This ratio is not a generic requirement for a lipid-coated microbubble. It is a formulation fingerprint.

The ratio can be expressed as:

[ \text{DPPA:DPPC:MPEG5000-DPPE} = 10:82:8 ]

The use of "in a mole ratio of 10% to 82% to 8%" creates an issue of claim interpretation. It may be read as requiring the exact stated nominal ratio, subject to ordinary manufacturing variation, or as requiring approximately those percentages. The claim does not expressly use "about" for the molar ratio, unlike the concentration limitations. A meaningful departure from 10:82:8 therefore creates a stronger non-infringement position than a minor analytical or manufacturing deviation.

The total lipid concentration is approximately 0.75 mg/mL

The phrase "in an amount of about 0.75 mg/mL" follows the three-lipid recitation. The most natural reading is that the specified lipid system is present at approximately 0.75 mg/mL, although the precise scope depends on the specification and prosecution history.

The concentration limitation is important because a formulation containing the same lipid ratio at a materially different total lipid concentration may fall outside the literal claim. "About" provides tolerance, but it does not eliminate the concentration requirement.

Glycerin and propylene glycol are each approximately 10% by volume

The claim recites:

glycerin at about 0.1 mL/mL; and
propylene glycol at about 0.1 mL/mL.

These limitations describe approximately 10% volume/volume for each component. A competing formulation that uses only one of the two polyols, or replaces either with another tonicity agent or solvent, would not literally satisfy claim 1.

The claim therefore protects more than the lipid shell. It also protects a specific liquid vehicle.

Perfluoropropane is required

Perfluoropropane is the gas limitation in claim 1. The claim does not cover every perfluorocarbon gas. A formulation using perfluorobutane, sulfur hexafluoride, or another gas would raise a literal-scope issue.

The claim also requires the gas in the composition but does not expressly recite:

a particular microsphere diameter;
a specific shell thickness;
a defined gas volume fraction;
a particular vial or delivery device;
a reconstitution step; or
a particular imaging indication.

Those limitations may appear in other claims or in the specification, but they are not required by the quoted claim 1.

Is claim 1 a formulation patent or a method-of-use patent?

Claim 1 is a formulation or composition claim. It does not require administration to a patient, ultrasound imaging, echocardiography, or diagnosis.

This distinction affects enforcement:

Patent type	Required proof for infringement
Composition claim	Accused product contains the claimed ingredients and meets the quantitative limitations
Method-of-use claim	Accused party performs the claimed medical or imaging steps
Manufacturing claim	Accused party performs the specified process steps
Device claim	Accused product has the claimed structural features

A finished injectable contrast product is the most direct infringement target. A raw-material supplier would generally require a separate analysis because the claim is directed to the complete composition rather than an individual lipid or gas.

What formulation characteristics create the highest design-around value?

The strongest design-around opportunities are the limitations that are both specific and independently measurable.

High-value design-around parameters

Replace one of the three named lipids.
Change the DPPA:DPPC:MPEG5000-DPPE ratio.
Change the PEG-lipid molecular weight.
Use a different perfluorocarbon gas.
Remove or materially alter propylene glycol.
Remove or materially alter glycerin.
Use a different total lipid concentration.
Change the formulation from the claimed liquid vehicle.

A product that retains the same lipid shell but changes the gas from perfluoropropane to another gas may avoid literal infringement of claim 1. A product that retains perfluoropropane but uses DSPC instead of DPPC may also avoid literal infringement, subject to equivalents analysis.

What other patents are relevant to the Definity and perflutren landscape?

The relevant patent estate is broader than claim 1 and generally divides into five technical groups.

Lipid-encapsulated gas microspheres

Earlier patent families cover the basic concept of gas-filled microspheres surrounded by lipid monolayers or bilayers. These patents may claim:

lipid-coated gas bubbles;
phospholipid shell structures;
stabilized ultrasound contrast agents;
particle-size distributions;
gas retention and acoustic response.

These earlier families are important prior-art references and may have covered the platform concept before the issuance of U.S. Patent 8,658,205.

Perfluorocarbon ultrasound contrast agents

A second group covers the use of perfluorocarbon gases, including perfluoropropane, in diagnostic imaging compositions. The claims may focus on:

the gas identity;
gas-to-lipid relationships;
acoustic persistence;
vascular imaging;
echocardiography;
preparation and storage conditions.

A competitor may avoid claim 1 but remain exposed to a separate patent claiming perfluoropropane microspheres or a broader perfluorocarbon contrast agent.

PEGylated phospholipid shells

MPEG5000-DPPE is a PEGylated phospholipid. Patents in this area commonly address:

PEG chain length;
PEG-lipid concentration;
shell stability;
circulation time;
resistance to aggregation;
freeze-drying or storage.

These patents can create overlapping rights even when a product does not use the exact 10:82:8 formulation.

Manufacturing and reconstitution

Additional rights may cover:

forming the microspheres;
gas exchange;
vial headspace;
mechanical agitation;
reconstitution before administration;
control of particle-size distribution;
sterile filling;
storage and shelf-life conditions.

Such patents may create process or supply-chain risk even when a finished formulation claim is avoided.

Method-of-use patents

Separate claims may cover the use of perflutren lipid microspheres for:

left ventricular opacification;
endocardial border delineation;
echocardiography;
ultrasound imaging of organs or tissue;
perfusion imaging;
diagnostic enhancement.

A generic or competing contrast agent can face method-of-use exposure even if its formulation differs from the product protected by claim 1.

What is the Orange Book status of U.S. Patent 8,658,205?

The FDA Orange Book is the relevant source for determining whether a patent is listed against an approved drug application and whether an ANDA applicant must address it through a Paragraph IV certification.[2]

Definity is approved under NDA 021064. The Orange Book analysis should distinguish:

patents listed for the Definity NDA;
patents listed for a particular dosage form or route;
patents that have expired;
patents delisted or removed;
patents that are not Orange Book-eligible because they claim manufacturing methods or uses outside the listing rules.

A patent number alone does not establish Orange Book listing status. Patent 8,658,205 must be checked against the FDA’s current patent-listing records for NDA 021064. A patent can be technically relevant to a product without being listed in the Orange Book.

When does U.S. Patent 8,658,205 lose exclusivity?

The patent expiration date cannot be determined from the claim text or issue number alone. The legally operative date depends on:

the earliest effective nonprovisional priority date;
continuation and divisional relationships;
patent-term adjustment;
terminal disclaimers;
any patent-term extension;
maintenance-fee status; and
post-grant or litigation outcomes.

The patent issued on February 25, 2014. Its issue date is not its expiration date. The expected term generally runs 20 years from the earliest effective U.S. nonprovisional filing date, subject to statutory adjustments under 35 U.S.C. §§ 154 and 156.[3]

Patent 8,658,205 should therefore be evaluated through its continuity data and USPTO Patent Examination Data System records before relying on a specific expiration date in a launch or freedom-to-operate analysis.

What Paragraph IV risks exist for a generic perflutren product?

A generic applicant would likely pursue an ANDA if the reference product and proposed product can be shown to meet the relevant pharmaceutical and performance requirements. The main Paragraph IV risk categories would be:

Risk area	Relevance
Exact lipid composition	High if the proposed product uses the 10:82:8 system
Total lipid concentration	High if approximately 0.75 mg/mL is replicated
Vehicle composition	High if glycerin and propylene glycol are both used at approximately 10% v/v
Perfluoropropane gas	High if the same gas is used
Product performance	Separate regulatory issue involving microsphere size, concentration, stability, and acoustic behavior
Manufacturing process	Potentially relevant if process claims remain enforceable
Method of use	Relevant where labeling includes a patented indication

The strongest non-infringement route would be a formulation that changes a claim-critical component while maintaining comparable ultrasound performance. Regulatory comparability and patent avoidance may point in different directions: the closer the formulation is to Definity, the lower the development risk may be but the higher the literal patent risk may become.

Is biosimilar risk relevant to this product?

Biosimilar risk is generally not the principal pathway issue for Definity. Perflutren lipid microsphere is a drug product rather than a biologic for which a conventional biosimilar analysis would ordinarily be the central framework.

The more relevant competitive pathway is an ANDA or another abbreviated drug application strategy, subject to FDA requirements for injectable contrast agents, product sameness or substitutability, analytical characterization, and clinical performance.

How strong is the patent estate for this formulation?

Claim 1 is relatively narrow but commercially meaningful.

Strengths

It identifies a complete finished formulation.
It recites three specific lipid species.
It uses a distinctive 10:82:8 molar ratio.
It includes both polyols and their approximate concentrations.
It requires perfluoropropane.
A product copied closely from the reference formulation could satisfy all limitations.

Weaknesses

The claim does not broadly cover all lipid-coated perfluoropropane microspheres.
It may be avoided by changing one lipid, the gas, the vehicle, or the concentration.
The use of "about" can create factual disputes over concentration boundaries.
The exact molar-ratio language may limit the claim to a narrow formulation window.
The claim does not independently cover manufacturing, imaging methods, or delivery devices.
Enforceability depends on the patent’s current term and prosecution history.

The claim has high blocking value against a close formulation copy and lower blocking value against a technically differentiated contrast agent.

What litigation and settlement issues should be reviewed?

A complete diligence file should examine:

ANDA Paragraph IV notices involving the Definity NDA;
district-court complaints under the Hatch-Waxman statute;
Federal Circuit appeals;
claim-construction decisions;
prosecution-history estoppel;
terminal disclaimers;
settlement agreements containing launch dates or licenses;
covenants not to sue;
authorized-generic arrangements;
FDA patent-listing changes.

No litigation or settlement conclusion should be inferred solely from the existence of U.S. Patent 8,658,205. Patent validity, enforceability, listing, and commercial blocking status are separate questions.

Key Takeaways

U.S. Patent 8,658,205 claim 1 is a narrow composition claim.
The protected formulation combines DPPA, DPPC, and MPEG5000-DPPE in a 10:82:8 molar ratio.
It also requires approximately 0.75 mg/mL lipid, sodium chloride, approximately 10% glycerin, approximately 10% propylene glycol, water, and perfluoropropane.
The claim closely tracks the formulation architecture associated with Definity perflutren lipid microspheres.
It does not broadly claim every ultrasound contrast agent or every perfluorocarbon microsphere.
The principal design-around levers are lipid identity, lipid ratio, PEG-lipid structure, gas identity, vehicle composition, and lipid concentration.
Orange Book listing must be verified separately from technical relevance.
The patent’s expiration date requires continuity, terminal-disclaimer, patent-term-adjustment, and patent-term-extension analysis.
Generic risk is primarily an ANDA and Paragraph IV issue, not a biosimilar issue.
The claim is strongest against a close Definity copy and weaker against a reformulated perfluorocarbon contrast product.

FAQs

Does U.S. Patent 8,658,205 cover perflutren by itself?

No. Claim 1 requires perfluoropropane together with the specified lipid system and liquid vehicle. Perfluoropropane alone is outside the quoted claim.

Can a formulation using DPPC and MPEG5000-DPPE but no DPPA infringe claim 1?

It would not literally satisfy the DPPA limitation. Separate claims or other patents could create independent exposure.

Does changing the lipid ratio avoid the patent?

A material change to the 10:82:8 ratio may avoid literal infringement, but the effect of "about," manufacturing tolerances, and the doctrine of equivalents must be evaluated.

Are ultrasound contrast microspheres regulated like biologics?

Perflutren lipid microsphere products are generally evaluated as drug products rather than through the conventional biosimilar pathway used for therapeutic biologics.

Does an expired patent still matter in a generic launch analysis?

An expired patent does not block launch through enforceable patent rights, but its disclosures remain relevant as prior art, freedom-to-operate history, and evidence of the technical development of the product.

References

U.S. Food and Drug Administration. (2024). Definity (perflutren lipid microsphere) injectable suspension: Prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book.
United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, §§ 2701-2750.
U.S. Patent No. 8,658,205. (2014). United States Patent and Trademark Office.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	016444	⤷ Start Trial
Austria	447976	⤷ Start Trial
Australia	2115599	⤷ Start Trial
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Details for Patent: 8,658,205

Summary for Patent: 8,658,205