# US Patent 10,835,492: Claim Scope, Vyxeos Relevance, Patent Strength, and Generic-Entry Risk

US Patent 10,835,492 protects a method of administering a reconstituted lyophilized liposomal formulation containing at least two therapeutic or diagnostic agents. Its commercial significance is highest for fixed-ratio daunorubicin and cytarabine liposomes, the technology used in Jazz Pharmaceuticals’ Vyxeos product. The patent is narrower than a composition or product-by-process patent because infringement requires administration of a formulation satisfying multiple physical, chemical, and stability limitations.

The principal risk to a generic or competing product is claim 1, reinforced by claims 2, 5, 6, 7, 8, 9, and 10. The strongest commercial limitation is the combination of a gel-phase liposome, external cryoprotectant, substantially no internal cryoprotectant, preservation of liposome size after lyophilization and reconstitution, and substantial retention of both agents.

What does US Patent 10,835,492 protect?

The patent claims a treatment method rather than the liposomal composition standing alone.

Claim 1 requires all of the following:

Claim element	Scope
Subject	An animal subject
Administration	Administration of a reconstituted formulation
Starting material	A lyophilized liposomal composition
Liposome phase	Gel-phase liposomes with a melting temperature, Tc, of at least 37°C
Payload	At least two therapeutic or diagnostic agents stably associated with the liposomes
Cryoprotection	A cryoprotectant external to the liposomes
Internal excipient	Substantially no internal cryoprotectant
Reconstitution result	Mean liposome diameter is maintained
Drug retention	Agents are substantially retained in the liposomes

The claim is cumulative. A formulation that uses the correct drug pair but fails the external-cryoprotectant or retention limitations would not satisfy claim 1 as written. The same applies to a formulation with the correct liposome size but a membrane transition temperature below 37°C.

The claims do not expressly require daunorubicin and cytarabine. Those agents enter through dependent claims 3 to 5. Claim 1 therefore reaches a broader set of two-agent liposomal formulations, subject to the structural and performance limitations.

How do the dependent claims narrow the patent?

The dependent claims create several distinct infringement pathways.

Fixed-ratio claims

Claim 2 requires the agents to be present at a fixed ratio and limits post-reconstitution ratio change to no more than 25%.

Claim 5 narrows the daunorubicin/cytarabine embodiment to a 1:5 ratio. This is the commercially important CPX-351 ratio associated with Vyxeos.

The ratio limitation is measured before and after reconstitution. A competitor could attempt to avoid the claim by using a different drug ratio, but that strategy would need to remain commercially viable and clinically acceptable. A product using a 1:5 ratio with equivalent post-reconstitution stability faces a higher risk.

Antineoplastic-agent claims

Claim 3 covers two stably associated antineoplastic agents. Claim 4 identifies two combinations:

Daunorubicin and cytarabine.
Irinotecan and floxuridine.

Claim 4 is not limited to the 1:5 daunorubicin/cytarabine ratio. Claim 5 adds that ratio as a further limitation.

Membrane-composition claim

Claim 6 requires a liposome membrane containing 50 to 80 mol% DSPC. DSPC is distearoylphosphatidylcholine, a high-transition-temperature phospholipid commonly used to form rigid or gel-phase liposomes.

This limitation is important because many liposomal formulations may use phospholipid mixtures, but not every product will contain DSPC within the claimed molar range. A formulation using another high-Tc phospholipid, or DSPC outside the stated range, may avoid claim 6 while remaining potentially exposed to claim 1.

Physical-stability claims

Claims 7 through 10 impose quantitative stability requirements:

Claim	Required performance
7	Liposome mean diameter increases by no more than 25% after lyophilization and reconstitution
8	Mean diameter remains maintained for at least six months at 5°C to 25°C
9	At least 75% of each agent remains retained after reconstitution
10	Liposome size distribution changes by no more than 25%

These claims convert formulation performance into infringement-relevant limitations. Testing methodology, sampling points, statistical treatment, and the definition of “mean diameter” can become central to claim construction and litigation.

Why is US 10,835,492 relevant to Vyxeos?

Vyxeos is a fixed-ratio liposomal formulation of daunorubicin and cytarabine approved by the FDA for certain adults with newly diagnosed therapy-related acute myeloid leukemia and AML with myelodysplasia-related changes. The product is administered intravenously after reconstitution.

The commercial formulation aligns with several limitations in the patent claims:

Vyxeos-related characteristic	Relevance to patent
Daunorubicin and cytarabine	Falls within claim 4
Fixed 1:5 molar ratio	Falls within claim 5
Liposomal delivery	Required by claim 1
Lyophilized presentation	Required by claim 1
Reconstitution before administration	Required by claim 1
Parenteral administration	Claim 11
Human patient	Claim 12
Cancer treatment	Claims 13 to 15

The patent does not cover every use of free daunorubicin and cytarabine. It also does not necessarily cover every liposomal version of those drugs. The product must satisfy the claimed formulation architecture and post-reconstitution performance.

Vyxeos was approved in the United States on August 3, 2017. FDA approval materials identify the product as a liposomal combination with a fixed daunorubicin-to-cytarabine ratio. The FDA label states that each vial contains 44 mg of daunorubicin and 100 mg of cytarabine, corresponding to the clinically relevant fixed-ratio formulation.[1]

What is the strongest claim in US Patent 10,835,492?

Claim 1 is the broadest claim, but its multiple limitations make it technically demanding to prove.

Claim 5 is commercially important because it expressly captures daunorubicin and cytarabine at a 1:5 fixed ratio. It is narrower than claim 1 but better aligned with Vyxeos.

Claim 6 may be strong against products using the claimed DSPC range because the limitation is compositional and measurable. Claims 7 through 10 may provide additional protection where the accused product has similar storage and reconstitution behavior.

The relative strength of the claims can be summarized as follows:

Claim group	Breadth	Commercial relevance	Proof burden
Claim 1	High within a defined formulation class	High	High
Claims 2 and 5	Narrow	Very high for fixed-ratio products	Moderate to high
Claim 4	Moderate	High for specified oncology combinations	Moderate
Claim 6	Narrow	High if DSPC is used	Moderate
Claims 7 to 10	Narrow	High where product data are available	High
Claims 11 to 15	Narrow use limitations	High for human cancer treatment	Moderate

The patent is strongest when asserted with a product-specific evidence package showing the liposome composition, cryoprotectant location, drug retention, particle size, and storage data. It is weaker if the patent owner must rely only on public prescribing information that does not disclose all technical parameters.

What formulations are protected by the patent?

The claimed formulations have a distinctive design:

A gel-phase liposome with Tc of at least 37°C.
At least two drugs associated with the liposome.
An external cryoprotectant.
Substantially no cryoprotectant inside the liposome.
Lyophilization followed by reconstitution.
Preservation of particle size and drug loading.

The claim architecture focuses on stabilization during freeze-drying and reconstitution. The external cryoprotectant limitation separates the claimed formulation from systems in which the cryoprotectant is encapsulated inside the liposome or distributed both inside and outside the vesicle.

A competing formulation could pursue several design-around strategies:

Design-around approach	Potential effect
Use a liquid liposomal formulation	May avoid the lyophilized-composition requirement
Use a liposome with Tc below 37°C	May avoid claim 1
Place cryoprotectant inside the liposome	May conflict with the “substantially no internal cryoprotectant” limitation
Use one active agent rather than two	May avoid the multiple-agent requirement
Change the daunorubicin/cytarabine ratio	May avoid claims 2 and 5
Use a non-DSPC membrane	May avoid claim 6, but not necessarily claim 1
Permit more than 25% particle-size change	May avoid claims 7 and 10
Permit less than 75% retention	May avoid claim 9, subject to regulatory and commercial consequences
Use a nonparenteral route	May avoid claim 11, but may not be clinically relevant for the product class

A design-around must be evaluated against all claims, not only claim 5. Avoiding the 1:5 ratio does not avoid the broader combination claim if the alternative product still meets claim 1.

When does US Patent 10,835,492 lose exclusivity?

A precise expiration date requires the patent’s earliest effective nonprovisional priority date, any patent-term adjustment, any patent-term extension, and any terminal disclaimer. Those facts cannot be derived from the claim text alone.

The governing framework is:

Ordinary patent term is generally 20 years from the earliest effective U.S. nonprovisional filing date under 35 U.S.C. §154.
Patent-term adjustment may extend the term for USPTO prosecution delays.
Patent-term extension under 35 U.S.C. §156 may apply to certain regulatory delays, subject to statutory limits.
A terminal disclaimer can shorten the enforceable term.
A continuation patent generally does not receive a new 20-year term independent of its parent’s effective filing date.

For commercial planning, the relevant date is the enforceable expiration of the specific patent, not the nominal 20-year term. The USPTO Patent Center record and FDA Orange Book patent listing should control the final date.[2][3]

What is the Orange Book status of US 10,835,492?

The Orange Book is relevant only if the patent is listed for an approved drug product and remains listed for that product. FDA listing does not establish validity or infringement. It affects abbreviated application procedures and potential Paragraph IV litigation.

For a product such as Vyxeos, the Orange Book analysis should address:

Issue	Business significance
Patent listed for the reference drug	Determines whether an ANDA applicant must address the patent
Patent type	Determines whether the patent is treated as a formulation, method-of-use, or other listed patent
Use code	Determines the scope of a section viii carve-out
Expiration date	Determines the earliest ordinary generic-entry date
Patent-term extension	May extend the relevant barrier
Delisting or correction	Can alter Paragraph IV exposure

A method-of-use listing can create a pathway for a generic applicant to carve out the patented indication under section viii, but that strategy does not eliminate exposure if the ANDA label or marketing conduct still induces use of the patented method.

How does a Paragraph IV challenge affect generic entry?

A generic applicant submitting an ANDA with a Paragraph IV certification alleges that the listed patent is invalid, unenforceable, or will not be infringed. The reference-product sponsor may sue within the statutory period, triggering an automatic stay of FDA approval for up to 30 months under the Hatch-Waxman framework.[4]

The principal challenge theories for this patent would likely include:

Noninfringement

The applicant could argue that its product lacks one or more required limitations, such as:

Tc of at least 37°C.
An external cryoprotectant.
Substantially no internal cryoprotectant.
At least two stably associated agents.
No more than 25% particle-size change.
At least 75% retention of each drug.

Invalidity for lack of written description or enablement

The broader claims cover multiple drug pairs, diagnostic agents, liposome compositions, and storage conditions. A challenger could argue that the specification does not adequately support or enable the full breadth of claim 1.

Obviousness

A challenger could combine prior art concerning:

Gel-phase liposomes.
DSPC-containing membranes.
Freeze-drying of liposomes.
External cryoprotectants.
Fixed-ratio combination chemotherapy.
Particle-size and drug-retention specifications.

The patent owner would likely rely on the combined stability profile and the claimed exclusion of internal cryoprotectant as evidence that the claimed formulation is not a routine aggregation of known features.

Indefiniteness

Terms such as “substantially associated,” “substantially no internal cryoprotectant,” “substantially retained,” and “maintained” may invite construction disputes. Their enforceability will depend on the specification’s definitions, examples, measurement protocols, and prosecution history.

What patent litigation affects the patent?

The claims alone do not establish whether US Patent 10,835,492 has been litigated, challenged before the Patent Trial and Appeal Board, or included in a settlement agreement.

The relevant litigation searches should cover:

ANDA litigation involving Vyxeos.
District court cases identifying US 10,835,492.
PTAB inter partes review or post-grant review records.
Federal Circuit appeals.
Paragraph IV notices addressing the patent.
Settlement agreements involving Jazz Pharmaceuticals, Celator Pharmaceuticals, or their successors.

A litigation assessment should distinguish between a case naming the patent and a decision that construes, invalidates, or limits these specific claims. A patent citation in a complaint does not establish that the claims survived scrutiny.

Which companies are challenging or competing with Vyxeos?

The most relevant competitive categories are:

Generic daunorubicin and cytarabine administered separately.
Alternative liposomal formulations.
Fixed-ratio combination products.
Clinical regimens using conventional induction chemotherapy.
New AML therapies that compete for the same patient population.

A conventional generic of daunorubicin or cytarabine does not necessarily practice the patent because the patent is directed to a two-agent liposomal formulation that is lyophilized, reconstituted, and administered. The more direct threat would come from a generic or follow-on product replicating the Vyxeos formulation and delivery architecture.

Biosimilar risk is limited. Vyxeos is a chemically defined liposomal drug, not a biologic. A competitor would generally pursue an ANDA or, depending on product differences, a 505(b)(2) pathway rather than a biosimilar application under the Public Health Service Act.[5]

What manufacturing and IP barriers does the patent create?

The patent creates barriers in four areas:

Formulation development

The competitor must develop a product that remains physically stable during lyophilization, storage, and reconstitution. Particle-size control and drug retention must be demonstrated experimentally.

Analytical characterization

The product must be characterized for:

Liposome diameter.
Size distribution.
Transition temperature.
Drug loading.
Drug ratio before and after reconstitution.
Internal and external excipient location.
Stability over the claimed storage period.

Process control

Manufacturing variables can affect infringement risk. Changes in lipid composition, hydration, loading conditions, freeze-drying cycle, cryoprotectant concentration, and reconstitution procedure may alter whether the product meets the claims.

Regulatory consistency

A generic applicant cannot freely change the formulation to avoid patent claims if the change prevents pharmaceutical equivalence, affects bioequivalence, or requires a different clinical package. Patent design-around and FDA approval strategy must be developed together.

How does US 10,835,492 compare with ordinary composition patents?

US 10,835,492 is a method patent with embedded formulation limitations. It differs from a conventional composition claim in several respects:

Issue	US 10,835,492	Typical composition patent
Infringing act	Administration of the claimed formulation	Making, using, selling, or importing the composition
Required patient use	Yes	Usually no
Physical specifications	Extensive	Varies
Product-label relevance	High	Moderate to high
Use-code carve-out potential	Relevant	Usually less relevant
Proof of infringement	Requires product and administration evidence	May be established by product testing
Generic risk	Depends on formulation and label	Often more direct

Because the claims require administration, enforcement may focus on the product label, instructions for reconstitution, clinical use, and evidence that the accused product satisfies the formulation parameters.

What is the revenue exposure associated with this patent?

The patent’s economic value is tied primarily to Vyxeos revenue and to the ability to delay a directly substitutable generic product. The patent does not block all daunorubicin or cytarabine sales, nor does it block all AML therapies.

Revenue exposure depends on:

Vyxeos annual U.S. sales.
The share of sales exposed to ANDA substitution.
The number and timing of generic applicants.
The enforceable expiration date.
The outcome of Paragraph IV litigation.
Whether a settlement permits an earlier launch.
The ability of a generic to obtain an AB rating.
Payer willingness to substitute a fixed-ratio liposomal product.

The most material downside event would be an approved generic matching the claimed fixed-ratio liposomal product before the patent’s enforceable expiration. A conventional generic of either active ingredient would have a smaller direct effect because it would not necessarily be therapeutically or pharmaceutically substitutable for Vyxeos.

Key takeaways

US Patent 10,835,492 claims administration of a reconstituted lyophilized liposomal formulation, not every daunorubicin/cytarabine product.
Claim 1 requires a gel-phase liposome with Tc of at least 37°C, an external cryoprotectant, substantially no internal cryoprotectant, two stably associated agents, and preservation of size and retention after reconstitution.
Claims 4 and 5 directly target daunorubicin/cytarabine products, including the 1:5 ratio associated with Vyxeos.
Claims 6 through 10 add measurable DSPC, particle-size, storage, size-distribution, and drug-retention requirements.
The patent is most commercially relevant to a generic or follow-on product replicating the Vyxeos formulation.
A conventional daunorubicin or cytarabine generic does not automatically infringe.
The patent’s precise expiration date requires review of the USPTO record, patent-term adjustment, terminal disclaimers, and any patent-term extension.
Vyxeos is a small-molecule liposomal product, so biosimilar risk is not the principal pathway. ANDA and 505(b)(2) strategies are more relevant.
The principal generic defenses are noninfringement, obviousness, lack of written description, enablement, and indefiniteness.
The claims alone do not establish the existence or outcome of Paragraph IV litigation, PTAB proceedings, or settlement agreements.

FAQs about US Patent 10,835,492

Does US Patent 10,835,492 cover free daunorubicin and cytarabine?

No. The claims require the agents to be stably associated with gel-phase liposomes in a lyophilized formulation that is reconstituted before administration.

Does a different daunorubicin-to-cytarabine ratio avoid the patent?

It may avoid claim 5, which requires a 1:5 ratio, but it may not avoid broader claims if the product satisfies claim 1 or other applicable limitations.

Can a generic carve out the patented AML indication?

Potentially, if the relevant patent is listed with a method-of-use code and the generic label can omit the patented use without creating induced-infringement risk. The feasibility depends on the Orange Book listing and the final proposed label.

Is a 505(b)(2) product automatically outside the patent?

No. The regulatory pathway does not determine infringement. A 505(b)(2) product can still practice the claimed formulation and administration method.

Does the patent protect the manufacturing process for the liposomes?

The supplied claims do not directly claim a manufacturing process. They claim administration of a formulation with specified structural and performance characteristics. Process steps may still be relevant as evidence of whether the resulting product meets those limitations.

References

U.S. Food and Drug Administration. (2017). Vyxeos prescribing information. FDA.
United States Patent and Trademark Office. (n.d.). Patent Center: U.S. Patent No. 10,835,492. USPTO.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. FDA.
U.S. Code, 21 U.S.C. §355(j).
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application process. FDA.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Jazz Pharms Therap	VYXEOS	cytarabine; daunorubicin	POWDER;INTRAVENOUS	209401-001	Aug 3, 2017		RX	Yes	Yes	10,835,492*PED	⤷ Start Trial			Y		⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	2768484	⤷ Start Trial	301016	Netherlands	⤷ Start Trial
European Patent Office	2768484	⤷ Start Trial	LUC00135	Luxembourg	⤷ Start Trial
European Patent Office	2768484	⤷ Start Trial	CA 2019 00051	Denmark	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,835,492

Which drugs does patent 10,835,492 protect, and when does it expire?

Summary for Patent: 10,835,492