US Patent 7,183,264: Regadenoson Claims, Scope, Expiration, and Patent Landscape

US Patent 7,183,264 covers methods, injectable pharmaceutical compositions, and myocardial perfusion imaging applications for regadenoson, the selective adenosine A2A receptor agonist marketed as Lexiscan. The patent does not claim regadenoson as a standalone chemical entity. Its principal protection is use-based and formulation-based.

The patent issued February 27, 2007, from an application claiming priority to an application filed in 2000. Its term expired in 2021, subject to any applicable patent-term adjustment recorded by the USPTO. The patent therefore does not currently block generic regadenoson manufacture, marketing, or use in the United States. Its historical significance was substantial because the claims covered the approved clinical use of regadenoson for pharmacologic cardiac stress and myocardial perfusion imaging.

What compound does US Patent 7,183,264 protect?

The claimed compound is regadenoson, chemically identified as:

1-{9-[(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-6-aminopurin-2-yl}pyrazol-4-yl)-N-methylcarboxamide.

Regadenoson is a modified adenosine analog. It activates the A2A adenosine receptor and produces coronary vasodilation with less peripheral vasodilation than nonselective adenosine.

The patent protects the compound only in specified methods and compositions. It does not contain a broad composition-of-matter claim covering every use of regadenoson. A separate composition-of-matter patent, if any, would have been the principal chemical exclusivity asset. Patent 7,183,264 instead focuses on the compound's cardiovascular and diagnostic applications.

Core technical characteristics

Characteristic	Relevance to the patent
Active ingredient	Regadenoson
Pharmacology	Selective adenosine A2A receptor agonist
Primary effect	Coronary vasodilation
Principal clinical use	Pharmacologic stress agent for myocardial perfusion imaging
Dosage form addressed	Solution and injectable composition
Administration route	Intravenous administration, including IV bolus
Claimed administration time	About 10 to about 30 seconds in dependent claims
Diagnostic context	Administration with a radionuclide followed by myocardial imaging
Product associated with the claims	Lexiscan regadenoson injection

What are the independent claims in US Patent 7,183,264?

The supplied claims contain three principal independent claim groups.

Claim 1: Coronary vasodilation

Claim 1 covers:

administering a therapeutically effective amount of regadenoson;
to a mammal;
for stimulating coronary vasodilatation.

Claim 2 narrows the mammal to a human.

The claim does not require imaging, a radionuclide, an IV bolus, a particular concentration, or a specific dosage form. It is therefore the broadest therapeutic-use claim in the set.

A product administered to produce coronary vasodilation would fall within the claim if the remaining patent-law requirements were met. The claim is directed to the act of administration, rather than to the manufacture or sale of regadenoson as a chemical.

Claim 3: Pharmaceutical composition

Claim 3 covers a pharmaceutical composition comprising:

regadenoson; and
one or more pharmaceutical excipients.

This is a broad composition claim. It does not expressly require an injectable dosage form, a particular concentration, a buffer, a preservative, or a specific container.

Claim 4 limits the composition to a solution. Claim 9 limits it to a formulation for injection.

A conventional sterile regadenoson injection would have been a likely target of this claim set during the patent term, assuming the formulation contained at least one pharmaceutical excipient.

Claim 5: Coronary vasodilation without peripheral vasodilation

Claim 5 covers administering regadenoson to a human to produce coronary vasodilation without peripheral vasodilation.

This claim adds a functional limitation. The relevant question is whether the claimed administration produces the specified cardiovascular selectivity, not merely whether regadenoson is present in a vial.

The phrase "without peripheral vasodilation" creates potential claim-construction and proof issues. Absolute absence of peripheral vasodilation would be difficult to establish pharmacologically. In context, the phrase may be interpreted as requiring coronary vasodilation without clinically meaningful or substantial peripheral vasodilation, depending on the intrinsic evidence and prosecution history.

How do the dependent claims narrow the patent scope?

The dependent claims divide into four technical clusters: administration speed, cardiac stress, imaging, and dose.

Claim cluster	Claims	Limitation
Human treatment	2	Mammal is a human
Solution formulation	4	Composition is a solution
Injection formulation	9	Composition is formulated for injection
IV bolus	6, 12, 19	Administration by IV bolus
Administration duration	7, 13, 20	About 10 to about 30 seconds
Coronary steal	10, 14, 17	Dose sufficient to stress the heart and induce coronary steal
Cardiac or coronary imaging	11, 15, 18	Dose sufficient for imaging heart or coronary activity
Dose range	16, 21, 22	About 0.01 to about 100 mg/kg
Myocardial perfusion imaging	8	Radionuclide plus regadenoson, followed by examination for insufficient blood flow

Claims 12 through 22 largely replicate or combine limitations from claims 1, 5, and 8. Their practical importance is narrower than the independent claims because a product or use must satisfy every limitation in the applicable claim.

What does the myocardial perfusion imaging claim cover?

Claim 8 covers a method of myocardial perfusion imaging that requires:

administering a radionuclide to a human;
administering regadenoson to the human; and
examining the myocardium for areas of insufficient blood flow after administration.

This claim is directed to a diagnostic workflow rather than merely to administration of the drug. It is relevant to pharmacologic stress imaging using nuclear medicine techniques, including protocols in which regadenoson is used to increase coronary blood flow and expose perfusion defects.

The claim does not expressly require:

a particular radionuclide;
a particular imaging instrument;
a specific dose;
a specific interval between drug administration and imaging; or
a named cardiac imaging modality.

Claims 17 through 21 narrow claim 8 by adding coronary steal, imaging-purpose, IV bolus, administration duration, or dose limitations.

What formulations are protected by US Patent 7,183,264?

The formulation claims cover a regadenoson composition with one or more pharmaceutical excipients. The claims are not limited to the commercial Lexiscan formulation unless a limitation in the specification or prosecution history narrows their interpretation.

Potentially covered formulations during the patent term included:

aqueous regadenoson solutions;
sterile injectable solutions;
ready-to-use IV products;
products containing buffers, tonicity agents, stabilizers, preservatives, or other excipients; and
formulations packaged for IV bolus administration.

The claims do not expressly require a particular excipient combination. That made claim 3 broader than a typical formulation patent limited to a specific pH range, concentration, buffer system, or stability profile.

The formulation claims also do not necessarily cover every manufacturing process for regadenoson. A manufacturer could face separate process, impurity, crystallization, or manufacturing patents if such rights existed in the relevant patent family or in third-party portfolios.

When did US Patent 7,183,264 lose exclusivity?

The patent's ordinary 20-year term ran from its earliest effective nonprovisional filing date and expired in 2021. Public patent records identify the patent as expired by term. The expiration removed the principal US patent barrier created by claims 1 through 22. [1]

The expiration analysis is separate from FDA regulatory exclusivity. FDA approval, labeling, and any regulatory exclusivity period do not extend an expired patent.

Exclusivity timeline

Event	Date or period	Commercial significance
Earliest claimed priority	2000	Controls the effective patent-term framework
Patent issued	February 27, 2007	Claims became enforceable, subject to statutory requirements
Lexiscan approved by FDA	April 10, 2008	Regadenoson entered the US diagnostic stress-agent market
Patent-term expiration	2021	Patent no longer created an ongoing US exclusion right
Post-expiration market	2021 onward	Generic entry became principally dependent on FDA approval and commercial execution

The patent could still have been relevant to historical infringement claims for acts occurring before expiration. Expiration does not eliminate accrued claims, subject to applicable limitation periods and other procedural requirements.

What was the FDA and Orange Book status of regadenoson?

FDA approved Lexiscan, regadenoson injection, under NDA 021385 for use as a pharmacologic stress agent in radionuclide myocardial perfusion imaging. The FDA label identifies regadenoson as an A2A receptor agonist and describes IV administration for cardiac stress testing. [2]

The Orange Book is the relevant FDA publication for approved drug products and listed patents. During the patent term, US Patent 7,183,264 was associated with the Lexiscan patent estate and was relevant to ANDA certification analysis. [3]

Regulatory implications

An ANDA applicant seeking approval for a generic regadenoson injection could have faced:

Paragraph IV certification against listed, unexpired patents;
a 30-month stay if the NDA holder or patent owner filed timely patent litigation;
labeling restrictions for protected methods of use;
formulation-related patent claims; and
commercial risk from claims covering the approved IV stress-imaging protocol.

After the patent expired, a Paragraph IV challenge to this patent no longer provided a meaningful early-entry mechanism because the patent itself no longer delayed approval as an enforceable barrier.

Were Paragraph IV challenges filed against this patent?

The supplied claim set does not establish whether a particular ANDA applicant filed a Paragraph IV certification or whether litigation was commenced. A reliable answer requires matching FDA Orange Book records with district-court docket records and the relevant ANDA applicant.

The legal significance is clear:

before expiration, a Paragraph IV certification could trigger patent litigation;
a timely suit could produce a 30-month FDA approval stay;
a successful challenge could support earlier generic approval;
after expiration, the patent could no longer provide forward-looking launch exclusivity.

The patent's method-of-use claims would have been more difficult to enforce against an ANDA product if the generic label omitted the patented use. That strategy is limited where the patented use is the central or unavoidable use of the approved product.

Which companies were associated with the regadenoson patent estate?

CV Therapeutics was the original developer and patent holder associated with regadenoson. Astellas obtained US commercial rights and later acquired CV Therapeutics. Astellas commercialized Lexiscan in the United States. [4]

The commercial structure matters because patent ownership, NDA ownership, licensing rights, and product marketing rights can reside with different entities. A patent assignment or license does not by itself establish that the same company owned the NDA or controlled all Orange Book listing decisions.

Commercial participants

Company	Role
CV Therapeutics	Original developer and patent-rights holder associated with regadenoson
Astellas Pharma	US commercial partner and subsequent acquirer of CV Therapeutics
Generic manufacturers	Potential ANDA sponsors after patent expiration
Nuclear-imaging providers	Downstream users of regadenoson-based stress protocols

How strong was the patent estate for regadenoson?

The patent was commercially useful but technically narrower than a composition-of-matter patent.

Strengths

Claim 1 covered the central therapeutic use: coronary vasodilation.
Claim 3 covered a broad pharmaceutical composition containing regadenoson and excipients.
Claims 6, 7, 12, 13, 19, and 20 addressed the clinically relevant IV-bolus administration format.
Claim 8 addressed the principal diagnostic use involving radionuclide myocardial perfusion imaging.
The claims aligned closely with the product's intended clinical use.

Weaknesses

The patent did not claim regadenoson as a standalone molecule.
Method claims require proof of the claimed administration or intended use.
"Without peripheral vasodilation" may create factual and construction disputes.
The 0.01 to 100 mg/kg claims appear poorly aligned with the fixed clinical dose described in the Lexiscan labeling. [2]
Claim 3 may be vulnerable to design-around arguments if a competing product did not satisfy a required claim limitation, although the broad "one or more pharmaceutical excipients" language reduces that opportunity.
The patent's term has expired.

The strongest historical claims were likely the broad method claim in claim 1 and the composition claim in claim 3. The most technically specific claims were those covering IV bolus administration over approximately 10 to 30 seconds and radionuclide myocardial perfusion imaging.

What generic entry risks exist for regadenoson?

The current US risk is primarily regulatory and commercial rather than patent-based.

Generic launch scenario

A generic manufacturer can generally pursue an ANDA for regadenoson injection without infringing an enforceable claim of US Patent 7,183,264 because the patent term has expired. The remaining barriers may include:

FDA bioequivalence and pharmaceutical-equivalence requirements;
sterile injectable manufacturing capability;
facility inspection and compliance;
supply of the active pharmaceutical ingredient;
stability and container-closure validation;
hospital and imaging-center contracting;
product shortage risk;
reimbursement and group purchasing arrangements; and
any later-expiring patents not addressed by this patent.

Because regadenoson is an injectable diagnostic drug, manufacturing and regulatory execution may be more significant than ordinary oral-solid-dose generic competition.

Biosimilar risk

Biosimilar analysis is not applicable. Regadenoson is a chemically synthesized small molecule, not a biological product regulated under the Public Health Service Act. The relevant pathway is an ANDA or, in some circumstances, a 505(b)(2) application, not a biosimilar application.

Does US Patent 7,183,264 create current litigation risk?

No current forward-looking exclusivity should be attributed to this patent. Its claims expired in 2021.

The patent could remain relevant in:

historical infringement disputes;
damages analysis for pre-expiration conduct;
diligence regarding legacy settlements;
interpretation of related continuation patents;
review of prior ANDA litigation; and
analysis of whether a later patent claims a distinct formulation, process, or dosage regimen.

A complete current litigation determination would require docket-level review of the Federal District Courts, the Federal Circuit, and any related ANDA cases. Patent 7,183,264 itself should not be treated as an active blocking patent solely because it appears in historical product or patent records.

How does US Patent 7,183,264 compare with other regadenoson rights?

Right type	Coverage	Current strategic value
Composition-of-matter patent	Regadenoson molecule itself	Highest value, but term-dependent
US 7,183,264	Coronary vasodilation, injectable compositions, IV bolus, imaging	Historical value; expired
Formulation patent	Specific concentration, excipient, pH, stability, or container	Could remain relevant if separately issued and unexpired
Method-of-use patent	Cardiac stress, perfusion imaging, dosing protocol	Could remain relevant only if unexpired and properly listed or enforceable
Manufacturing patent	Synthesis, purification, polymorph, impurity control	Potential post-expiration barrier if independently valid and unexpired
Regulatory exclusivity	FDA approval-based protection	Separate from patent term and generally time-limited

The key diligence issue is whether later or related patents claimed a narrower formulation, manufacturing process, or dosing regimen with a later expiration date. Patent 7,183,264 alone does not answer that question.

Key Takeaways

US Patent 7,183,264 covers regadenoson methods and pharmaceutical compositions, not the unqualified molecule itself.
Claim 1 covers coronary vasodilation in a mammal and is the broadest therapeutic-use claim.
Claim 3 covers a regadenoson composition with one or more pharmaceutical excipients.
Claim 8 covers myocardial perfusion imaging using a radionuclide and regadenoson.
Dependent claims address IV bolus administration, a 10-to-30-second administration period, coronary steal, imaging, injection formulations, and dose ranges.
FDA approved Lexiscan in 2008 for pharmacologic stress in radionuclide myocardial perfusion imaging.
The patent expired in 2021 and is no longer a current US blocking right.
Regadenoson is a small molecule, so biosimilar competition is not the applicable framework.
Current generic-entry risk depends on FDA approval, sterile manufacturing, supply, contracting, and any separate unexpired patents.
The principal remaining diligence issue is the existence and status of related continuation, formulation, process, or later-issued patents.

FAQs About US Patent 7,183,264 and Regadenoson

Is regadenoson itself still patented in the United States?

US Patent 7,183,264 does not claim regadenoson as an unrestricted chemical compound. Its method and composition claims expired in 2021. Separate patent families must be reviewed to determine whether any later rights remain.

Can a generic company sell regadenoson injection after expiration of US Patent 7,183,264?

Yes, expiration removes this patent as a continuing infringement barrier. The manufacturer still must obtain FDA approval and satisfy sterile injectable manufacturing, quality, labeling, and supply requirements.

Did US Patent 7,183,264 cover Lexiscan's IV push administration?

Yes. Claims 6, 7, 12, 13, 19, and 20 address IV bolus administration and, in dependent claims, administration over approximately 10 to 30 seconds.

Does the patent cover adenosine myocardial perfusion imaging generally?

No. The claims specifically require regadenoson. They do not broadly cover every myocardial perfusion imaging method using adenosine or another pharmacologic stress agent.

Could a later formulation patent still restrict generic regadenoson?

Yes. Expiration of US Patent 7,183,264 does not invalidate or expire separate patents covering a particular formulation, manufacturing process, impurity profile, container system, or dosing protocol.

References

United States Patent and Trademark Office. (2007). US Patent No. 7,183,264, Methods of inducing coronary vasodilation. https://patents.google.com/patent/US7183264B2/en
U.S. Food and Drug Administration. (2023). Lexiscan (regadenoson injection) prescribing information. Astellas Pharma US, Inc. https://www.accessdata.fda.gov/drugsatfda_docs/label/
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book
Astellas Pharma Inc. (2009). Astellas completes acquisition of CV Therapeutics. https://www.astellas.com/en/news/ ___

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1189916	⤷ Start Trial	C300477	Netherlands	⤷ Start Trial
European Patent Office	1189916	⤷ Start Trial	CA 2011 00005	Denmark	⤷ Start Trial
European Patent Office	1189916	⤷ Start Trial	91785	Luxembourg	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,183,264

Summary for Patent: 7,183,264