US Patent 8,685,441: Claim Scope, Definity Manufacturing Coverage and Ultrasound Contrast Patent Landscape

US Patent 8,685,441 is a process patent directed to manufacturing a lipid-based ultrasound contrast agent containing DPPC, DPPA and MPEG5000-DPPE with a perfluorocarbon gas, principally perfluoropropane. Its strongest protection is not the general concept of lipid microbubbles. It is the tightly defined solvent-precipitation and reconstitution sequence used to produce the lipid suspension before gas formulation.

The patent creates infringement exposure for a manufacturer that uses the specified phospholipid blend, solvent sequence, temperature conditions, concentration ranges and vial-processing steps in combination with perfluoropropane ultrasound imaging. The claims are most relevant to Definity-type products and manufacturing processes, rather than to sulfur-hexafluoride or albumin-based contrast agents.

What does US Patent 8,685,441 protect?

The patent protects two related methods:

A method of manufacturing and using an ultrasound contrast agent.
A manufacturing process for preparing the lipid suspension and then using it in imaging.

Claim 1 requires every major stage of the process:

Required element	Claim requirement
Lipid components	DPPA, DPPC and MPEG5000-DPPE
First solvent step	Dissolution in a first non-aqueous solvent
Addition sequence	Sequential addition or premixing before solvent addition
Precipitation step	Second non-aqueous solvent precipitates a solid lipid blend
Collection	Solid lipid blend is collected
Re-dissolution	Solid lipid blend dissolves in a third non-aqueous solvent
Aqueous conversion	Lipid blend solution contacts an aqueous solution
Gas formulation	Lipid suspension is formulated with a perfluorocarbon gas
Clinical use	Contrast agent is used for imaging in a subject

The claim is cumulative. A product may contain the same ingredients and perfluorocarbon gas but avoid literal infringement if its lipid suspension is prepared without the claimed solvent precipitation and re-dissolution sequence.

How does claim 1 define the protected manufacturing process?

Claim 1 is a combination claim with both composition and process limitations. It does not claim any lipid suspension containing DPPC, DPPA and MPEG5000-DPPE regardless of manufacturing method.

The required sequence is:

Dissolve the three named phospholipids in a first non-aqueous solvent.
Add a second non-aqueous solvent that precipitates the phospholipids.
Collect the resulting solid lipid blend.
Dissolve that blend in a third non-aqueous solvent.
Add the resulting solution to an aqueous phase.
Produce the ultrasound contrast agent with a perfluorocarbon gas.
Use the agent in imaging.

The claim also covers two alternative ways of performing the first mixing operation:

Adding each phospholipid sequentially to the first solvent.
Combining the phospholipids before adding them to the first solvent.

A process using a materially different order of addition may avoid the express limitation, although the doctrine of equivalents and dependent-claim coverage would require separate analysis.

What solvents and process conditions are protected?

The dependent claims narrow the process to a manufacturing recipe associated with the commercial lipid suspension.

Claim	Protected feature
2	First solvent is methanol and toluene
3	Second solvent is methyl tert-butyl ether
4	Third solvent is propylene glycol
5	Aqueous phase contains sodium chloride, glycerin and propylene glycol
6	Combination of claims 2 through 5
7	0.75 to 1.0 mg lipid blend per mL suspension
8	About 0.75 mg/mL lipid blend
9	Third solvent heated to about 30 to 70°C
10	Third solvent heated to about 50 to 55°C
11	5 to 15 mg solid lipid blend per mL third solvent
12	About 15 mg/mL
13	Aqueous phase heated to about 45 to 60°C
14	Aqueous phase heated to about 50 to 55°C
15	One or two sterilizing filtration steps
16	0.2-micron filters
17	Dispensing into a vial before gas formulation
18	Headspace exchange with perfluorocarbon gas
19	Perfluoropropane
20	Perfluoropropane in the vial headspace process
21	Vial sterilization
22	Sterilization at about 126 to 130°C for 1 to 10 minutes
23	Both solvent and aqueous phase heated to about 50 to 55°C
25	MPEG5000-DPPE, DPPA and DPPC at an 8:10:82 mole-percent ratio

Claims 24, 26 and 27 combine the concentration and composition limitations with the broader process limitations.

The most commercially significant dependent claims are claims 6, 23 and 25. Together, they capture a specific manufacturing platform:

Methanol/toluene dissolution.
Methyl tert-butyl ether precipitation.
Propylene glycol re-dissolution.
Saline, glycerin and propylene glycol aqueous phase.
Heating at approximately 50 to 55°C.
An 8:10:82 MPEG5000-DPPE/DPPA/DPPC ratio.

What does independent claim 28 cover?

Claim 28 is a process-and-use claim. It repeats the manufacturing sequence of claim 1 but presents the steps as a complete process:

Forming the lipid solution.
Precipitating the solid lipid blend.
Collecting the solid.
Re-dissolving the blend.
Forming the aqueous lipid suspension.
Adding perfluorocarbon gas.
Using the contrast agent for imaging.

Claim 28 does not depend on claim 1. It therefore provides an independent infringement route if a competing process satisfies its elements.

The claim is especially important because it covers the manufacturing process even where the accused party does not market or label the product in a way that directly reproduces all limitations of claim 1. The final imaging-use limitation remains part of the claim, however. A process-only manufacturer may present a different infringement analysis than an integrated manufacturer that makes and uses the agent.

Which commercial product is most closely related to the patent?

The claim structure closely corresponds to a Definity-type ultrasound contrast agent manufactured by Lantheus Medical Imaging. Definity uses perflutren lipid microspheres. Perflutren is a perfluoropropane gas, also known as octafluoropropane, encapsulated in a lipid shell.

The formulation components identified in the patent are associated with this product class:

Product	Sponsor or manufacturer	Gas or core	Shell technology	Relationship to US 8,685,441
Definity	Lantheus Medical Imaging	Perfluoropropane	Lipid microspheres	Closest technical correspondence
Lumason/SonoVue	Bracco	Sulfur hexafluoride	Phospholipid microspheres	Different gas; generally outside literal gas limitation
Optison	GE Healthcare	Perfluoropropane	Human serum albumin microspheres	Different shell material and process

Definity’s FDA-approved indication includes contrast enhancement during echocardiography and other ultrasound imaging applications. Lumason and Optison use different formulation technologies and therefore present a different claim landscape (U.S. Food and Drug Administration, 2024a, 2024b, 2024c).

How strong is the patent estate for a Definity-type product?

The patent is strongest against process replication, not against all competing ultrasound contrast agents.

Strongest infringement scenario

A competitor would face the highest risk if it:

Uses DPPA, DPPC and MPEG5000-DPPE.
Uses methanol/toluene to dissolve the lipids.
Uses methyl tert-butyl ether to precipitate a solid lipid blend.
Re-dissolves the blend in heated propylene glycol.
Adds the solution to a heated saline/glycerin/propylene glycol phase.
Uses a comparable 8:10:82 mole ratio.
Filters through 0.2-micron filters.
Exchanges vial headspace with perfluoropropane.
Uses the resulting agent in ultrasound imaging.

That process could implicate claim 1, claim 6, claim 23, claim 25 and claim 28, depending on the precise operating conditions.

Weaker infringement scenario

Risk declines where a competing manufacturer:

Uses sulfur hexafluoride instead of perfluoropropane.
Uses albumin rather than a phospholipid shell.
Uses a different phospholipid composition.
Forms the lipid suspension through direct hydration or homogenization.
Avoids the precipitation and solid-blend collection steps.
Uses a different solvent system.
Manufactures a product without the claimed clinical-use activity in the relevant jurisdiction.

A process that merely produces lipid microspheres is not necessarily within the patent.

What is the patent expiration timeline?

US Patent 8,685,441 was issued on April 1, 2014. Its expiration is governed by the earliest effective nonprovisional priority date, not by the issue date. Based on the patent family timing, the ordinary term is expected to fall in the 2029 to 2030 period, subject to patent-term adjustment, terminal disclaimers and any applicable regulatory extension.

Event	Date or period
Patent issuance	April 1, 2014
Ordinary statutory term	20 years from the earliest effective nonprovisional filing
Expected expiration window	Approximately 2029 to 2030
Regulatory exclusivity	Separate from patent term
PTE relevance	Must be confirmed against the product’s approved NDA and statutory eligibility

Patent expiration does not automatically eliminate all exclusivity for a commercial ultrasound contrast agent. Separate formulation, manufacturing, use and platform patents may have different terms. FDA regulatory exclusivity also operates independently of patent rights (USPTO, 2024; FDA, 2024d).

Is US Patent 8,685,441 an Orange Book patent?

The Orange Book lists patents submitted by NDA sponsors for approved drug products. Whether US 8,685,441 is currently listed for a particular NDA depends on the sponsor’s submission, FDA acceptance and the specific product relationship.

The patent’s claims are manufacturing and method-of-use claims. Manufacturing claims do not automatically qualify for Orange Book listing. The listing question therefore cannot be answered from the patent claims alone. A patent may be enforceable without appearing in the Orange Book, and an Orange Book listing does not itself establish infringement.

For Definity, the relevant regulatory record is the NDA patent listing for NDA 021064 and its current Orange Book entry. A freedom-to-operate review should compare:

Current Orange Book listings.
Patent use codes.
Delisting or expiration status.
Any pediatric-exclusivity or patent-term-extension notation.
The approved product description and manufacturing information.

What Paragraph IV risks exist?

A generic applicant seeking approval of a competing perflutren lipid microsphere product could challenge listed patents through an ANDA Paragraph IV certification. The principal challenge routes would be:

Challenge theory	Application to US 8,685,441
Anticipation	Earlier disclosure of the complete solvent sequence and lipid composition
Obviousness	Combination of known lipid-microsphere manufacturing steps
Written description	Whether the full claimed process is adequately supported
Enablement	Whether the specification enables the full breadth of solvent and temperature ranges
Noninfringement	Different solvent order, gas, lipid ratio or sterilization process
Invalidity based on public use	Earlier commercial manufacture or disclosed batch records

The patent’s narrow process details create both strength and vulnerability. The details can distinguish the claims from broad prior art, but they also give an accused manufacturer multiple design-around opportunities.

A generic applicant could seek approval using a substantially different process while producing a clinically comparable agent. The sponsor could still assert process claims if confidential manufacturing information, batch records or discovery evidence establishes performance of the claimed steps.

Which companies are challenging the relevant market?

The principal competitive products are supplied by Lantheus, Bracco and GE Healthcare.

Company	Product	Competitive issue
Lantheus	Definity	Perfluoropropane lipid microspheres; closest patent relevance
Bracco	Lumason/SonoVue	Sulfur hexafluoride phospholipid microspheres
GE Healthcare	Optison	Perfluoropropane in an albumin shell
Potential generic entrants	Perflutren or alternative microsphere products	Must address CMC reproducibility, sterility, gas loading and patent risk

The competitive landscape is differentiated by gas, shell composition, vial activation, stability and imaging indication. A Lumason-type product is less likely to infringe claims requiring perfluoropropane and the specified three-lipid blend. An Optison-type product may use perfluoropropane but lacks the claimed phospholipid architecture.

What manufacturing and IP barriers affect generic launch?

The largest barriers are technical rather than limited to the patent.

Sterile manufacturing

The process includes sterilizing filtration, vial dispensing, headspace gas exchange and terminal sterilization. Each stage affects particle size, gas retention, shell integrity and dose consistency.

Gas loading

Perfluoropropane headspace exchange must produce reproducible gas incorporation into the lipid suspension. Small changes in vial fill volume, headspace pressure, agitation and storage temperature can alter microbubble performance.

Lipid composition

The claimed 8:10:82 mole-percent ratio creates a narrow composition target. A generic manufacturer may need to establish equivalence despite using a different process or excipient profile.

CMC comparability

The relevant product attributes include:

Microsphere size distribution.
Concentration of microspheres.
Acoustic response.
Gas retention.
Lipid concentration.
Stability after activation.
Sterility and particulate control.
Imaging performance.

These requirements increase development cost and make a simple formulation substitution unlikely to be sufficient for approval.

What licensing and settlement issues are relevant?

The supplied claim set does not establish a licensing agreement, covenant not to sue or patent settlement involving US 8,685,441. Public licensing analysis should distinguish between:

Licenses covering the underlying microbubble platform.
Manufacturing technology licenses.
Patent settlements resolving Paragraph IV litigation.
Distribution agreements that do not transfer patent rights.
Cross-licenses involving diagnostic imaging products.

A commercial agreement for Definity or another ultrasound contrast agent does not, by itself, prove a license to the patent. The relevant evidence would be an executed agreement, SEC filing, litigation settlement, FDA correspondence or court order.

How does this patent compare with broad ultrasound contrast patents?

US 8,685,441 is narrower than foundational patents claiming lipid-encapsulated gas microspheres generally. Its commercial value lies in process coverage around a specific product architecture.

Patent category	Typical scope	Relationship to US 8,685,441
Platform patents	Gas-filled microspheres and ultrasound imaging	Broader but often older
Composition patents	Specific lipids, gases and ratios	Overlapping technical subject matter
Manufacturing patents	Solvent, hydration, filtration and vial steps	Closest category
Method-of-use patents	Echocardiography, vascular imaging or perfusion	Separate infringement analysis
Regulatory patents	Approved product or labeled use	Relevant to Orange Book and ANDA strategy

The patent should be evaluated as one layer in a portfolio, not as the entire Definity estate.

What generic launch scenarios exist?

Scenario 1: Process replication

A generic copies the formulation and manufacturing sequence. This creates the highest infringement risk and the clearest basis for discovery of process evidence.

Scenario 2: Solvent-process design-around

A generic keeps the same lipids and perfluoropropane but uses direct hydration, emulsification or another solvent sequence. Literal infringement risk is materially lower, but composition and other family patents may remain relevant.

Scenario 3: Gas substitution

A generic uses sulfur hexafluoride. This avoids claims requiring perfluoropropane but creates a different product-development and regulatory program.

Scenario 4: Shell substitution

A generic uses albumin or another shell material. This avoids the three-phospholipid limitations but may resemble Optison rather than Definity.

Scenario 5: Post-expiration entry

A manufacturer waits until the relevant patent term expires and launches a product supported by an ANDA or other FDA pathway. This reduces patent risk but does not eliminate separate patent, regulatory or trade-secret barriers.

Key Takeaways

US 8,685,441 is a manufacturing and imaging-use patent centered on DPPC, DPPA and MPEG5000-DPPE.
The core inventive distinction is the solvent precipitation, solid-blend collection, re-dissolution and aqueous conversion sequence.
Claims 6, 23, 25 and 28 are the most commercially important claim combinations.
The patent most directly implicates Definity-type perfluoropropane lipid microspheres.
Lumason/SonoVue and Optison use materially different technologies and offer clearer design-around positions.
The expected statutory expiration window is approximately 2029 to 2030, subject to the official patent-term calculation.
Orange Book status must be assessed separately from patent enforceability.
Generic risk is highest where a competitor copies the lipid composition, solvent system, heating conditions, filtration and perfluoropropane vial process.
Manufacturing know-how, sterile processing and gas-loading reproducibility may remain significant barriers after patent expiry.
The supplied record establishes no licensing agreement or settlement involving this patent.

FAQs

Does US 8,685,441 cover all perfluoropropane ultrasound contrast agents?

No. The claims require specific phospholipids and a defined manufacturing sequence. Perfluoropropane alone is insufficient.

Can a competitor avoid the patent by changing only the solvent?

Potentially. A materially different solvent system may avoid literal infringement of the dependent claims, but the competitor would still need to analyze claim 1 and claim 28 and any related patent-family claims.

Does the patent cover the Definity drug substance itself?

The claims primarily cover methods of making and using the lipid suspension and gas-formulated contrast agent. They do not broadly claim every Definity vial independent of its manufacturing process.

Is a biosimilar application the normal pathway for a competing product?

No. Definity is a drug-device contrast product rather than a biologic subject to the standard biosimilar pathway. A competing product would generally be evaluated under an FDA drug pathway, potentially including an ANDA or a 505(b)(2) application depending on product differences.

Can patent expiration eliminate all generic-entry risk?

No. Expiration of this patent would not eliminate separate composition, formulation, method-of-use, trade-secret, regulatory or platform-patent issues.

References

Bracco Diagnostics Inc. (2024). Lumason prescribing information. U.S. Food and Drug Administration.
GE Healthcare. (2024). Optison prescribing information. U.S. Food and Drug Administration.
Lantheus Medical Imaging, Inc. (2024). Definity prescribing information. U.S. Food and Drug Administration.
U.S. Food and Drug Administration. (2024a). Drugs@FDA: Definity NDA 021064. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (2024b). Drugs@FDA: Lumason NDA 203684. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (2024c). Drugs@FDA: Optison NDA 020451. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (2024d). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book
U.S. Patent and Trademark Office. (2014). U.S. Patent No. 8,685,441: Methods for preparing lipid-based ultrasound contrast agents. https://patents.google.com/patent/US8685441B2/en
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term calculation resources. https://www.uspto.gov/patents/laws/patent-term-calculator

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	016444	⤷ Start Trial
Austria	447976	⤷ Start Trial
Australia	2115599	⤷ Start Trial
Australia	746067	⤷ Start Trial
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Details for Patent: 8,685,441

Summary for Patent: 8,685,441