United States Drug Patent 5,070,877: Claim Scope, Expiration, and Adenosine Stress-Imaging Patent Landscape

U.S. Patent No. 5,070,877 covers diagnostic methods that induce coronary vasodilation with an adenosine receptor agonist and then assess myocardial function, coronary artery disease, ventricular dysfunction, or coronary flow reserve. The patent is a method-of-use patent, not a composition, formulation, manufacturing, or device patent. Based on its 1991 issue date and the pre-URAA 17-year patent term, the patent expired in December 2008. It should not create current U.S. generic, clinical, or biosimilar entry risk.

What does U.S. Patent 5,070,877 protect?

The patent protects the use of pharmacologically induced coronary vasodilation as a diagnostic stress test. Its central combination is:

Administration of an adenosine receptor agonist to a human.
Administration through an intravenous or intracoronary route.
Delivery at a specified dose or dose range.
Sufficient coronary artery dilation.
Performance of an imaging or coronary blood-flow technique.
Detection or assessment of myocardial dysfunction.

The claims do not require a particular commercial adenosine product. They claim a diagnostic method defined by the pharmacologic stimulus, route, dosage, and diagnostic procedure.

The broadest independent claims are claims 1 and 2. Claims 17, 19, 27, 28, 35, and 37 create more specific diagnostic-method categories. Claims 43 through 48 are highly specific combination claims directed to adenosine, thallium-201, scintigraphy, echocardiography, and Doppler flow measurement.

What are the main claim categories?

Claim group	Diagnostic objective	Drug administration	Diagnostic technique
Claims 1-16	Myocardial dysfunction generally	IV or intracoronary adenosine agonist	Perfusion imaging, ventricular imaging, or coronary flow measurement
Claims 17-26	Coronary artery disease	IV or intracoronary agonist	Radiopharmaceutical myocardial perfusion imaging
Claims 27-34	Ventricular dysfunction caused by coronary artery disease	Primarily IV, with a dose inconsistency in claim 28	Echocardiography, contrast ventriculography, or radionuclide angiography
Claims 35-42	Coronary flow reserve or flow difference	IV or intracoronary agonist	Doppler flow catheter, DSA, or radiopharmaceutical imaging
Claims 43-48	Narrow adenosine diagnostic protocols	IV infusion or intracoronary bolus	Thallium scintigraphy, echocardiography, or Doppler flow catheter

How broad are the independent claims?

Claims 1 and 2 are broad method claims. Claim 1 covers intravenous administration at approximately 20 to 200 mcg/kg/minute. Claim 2 covers intracoronary administration at approximately 2 to 20 mcg.

Both claims require an adenosine receptor agonist "sufficient to provide coronary artery dilation." This functional limitation is important. Merely administering an adenosine-related compound without achieving coronary vasodilation would not satisfy the claim as written.

The claims also require a technique "to detect the presence and assess the severity" of myocardial dysfunction. A procedure performed solely for treatment, routine monitoring, or a non-diagnostic purpose may not meet this limitation.

What limitations are required for infringement?

A potentially infringing protocol would generally need to satisfy all of the following:

Human subject.
Adenosine receptor agonist.
Claimed intravenous or intracoronary route.
Claimed dosage range, unless a doctrine-of-equivalents theory were available.
Coronary artery dilation.
Diagnostic assessment of myocardial dysfunction or coronary flow.
Performance of the claimed type of imaging or flow measurement for the specified purpose.

The patent does not broadly claim every use of adenosine in cardiology. It does not cover adenosine treatment of supraventricular tachycardia, general vasodilation, pharmaceutical compositions, or the manufacture of adenosine.

Which compounds fall within the claimed genus?

Claim 4 lists:

Adenosine.
1-methyl-2-phenylethyl-adenosine.
5-ethyl carboxamide-adenosine.
Cyclopentyl adenosine.
2-chloro adenosine.
Adenine.
Inosine.
Adenosine monophosphate.
Adenosine diphosphate.
Adenosine triphosphate.

Claims 20, 29, and 38 repeat substantially the same group, although claim 20 contains a duplication of "adenosine" and omits "adenine" compared with claim 4.

The list creates a closed or substantially closed Markush group for those dependent claims. A compound not listed may still fall within claims 1, 2, 17, 19, 27, 28, 35, or 37 if it qualifies as an adenosine receptor agonist and satisfies the other limitations.

Does regadenoson fall within the claims?

Regadenoson is an adenosine A2A receptor agonist, but it is not one of the specifically named compounds in the dependent-claim lists. The broader independent claims use the functional term "adenosine receptor agonist." Whether regadenoson would fall within an independent claim would depend on claim construction, prosecution history, the relevant dosage and route, and whether the diagnostic protocol satisfied all other limitations.

Regadenoson was developed and commercialized after the patent’s filing and issue dates. Its principal U.S. product, Lexiscan, is an intravenous pharmacologic stress agent used with myocardial perfusion imaging. Later patents covering regadenoson composition, formulation, dosing, or diagnostic use would need to be analyzed separately from Patent 5,070,877.

What imaging methods and radiopharmaceuticals are protected?

Claims 10-12 and 21-26 cover broad categories of myocardial perfusion imaging and radiopharmaceutical agents.

Imaging techniques listed in the patent

Scintigraphy.
Single-photon emission computed tomography, or SPECT.
Positron emission tomography, or PET.
Nuclear magnetic resonance imaging.
Perfusion contrast echocardiography.
Digital subtraction angiography.
Ultrafast X-ray computed tomography, identified as CINE CT.

Radiopharmaceutical agents listed in the patent

Thallium-201.
Technetium-99m.
Derivatives of technetium-99m.
Nitrogen-13.
Rubidium-82.
Iodine-123.
Oxygen-15.

Claim 43 is the most commercially recognizable species claim in the supplied text. It requires:

IV infusion of adenosine at approximately 20 to 200 mcg/kg/minute.
Administration of thallium-201.
Scintigraphy to assess coronary artery disease.

Claim 46 covers the intracoronary counterpart using a 2 to 20 mcg adenosine bolus, thallium-201, and scintigraphy.

The claims are not limited to a particular imaging machine, tracer supplier, scanner manufacturer, or image-processing algorithm.

What does the patent cover for ventricular dysfunction?

Claims 27-34 cover pharmacologic assessment of ventricular dysfunction caused by coronary artery disease.

The listed ventricular imaging techniques are:

Echocardiography.
Contrast ventriculography.
Radionuclide angiography.

Claim 44 narrows the protocol to IV adenosine followed by echocardiography. Claim 47 covers intracoronary adenosine followed by echocardiography.

A key limitation is causation: claims 27 and 28 specify ventricular dysfunction "caused by coronary artery disease." A ventricular-function study directed to nonischemic cardiomyopathy, valvular disease, or another unrelated cause would present a weaker literal-infringement case under these claims.

What does the patent cover for coronary flow reserve?

Claims 35-42 address the difference in coronary blood flow through disease-free and stenotic vessels. The stated objective is assessment of vasodilatory capacity or coronary flow reserve.

The listed techniques are:

Doppler flow catheter.
Digital subtraction angiography.
Radiopharmaceutical imaging techniques.

Claims 45 and 48 provide narrow protocols using adenosine and a Doppler flow catheter. Claim 45 uses intracoronary bolus administration. Claim 48 uses intravenous infusion.

These claims require more than an imaging study showing perfusion. They focus on measuring or determining the difference in coronary blood flow between disease-free and stenotic vessels.

Are there drafting defects that affect claim interpretation?

Several drafting issues are evident from the supplied claim text.

Claim 28 has a route and dosage inconsistency

Claim 28 identifies intravenous administration but recites a dose of approximately 2 to 20 mcg, which corresponds to the intracoronary dosage in claim 2 rather than the intravenous dosage in claim 1. This may reflect a transcription error, prosecution amendment, or an issued-claim defect.

The inconsistency could affect the scope and enforceability of claim 28. It does not necessarily affect claim 27 or the other claim families.

Claim 20 contains a duplicated compound

Claim 20 lists adenosine twice and does not match the compound list in claim 4 exactly. This is unlikely to expand the claim beyond the compounds actually recited.

Some dependent claims are redundant

Claims 7-9, 23-26, 32-34, and 40-42 repeatedly narrow the agonist to adenosine or the diagnostic procedure to a specified technique. The redundancy creates multiple fallback positions but does not materially expand the independent claims.

Typographical defects may not be dispositive

The supplied text includes "coronary arter dilation" in claim 48 and inconsistent capitalization of Doppler. These errors ordinarily would be evaluated under the claim-construction and correction doctrines applicable to issued patents.

When did U.S. Patent 5,070,877 lose exclusivity?

U.S. Patent No. 5,070,877 issued on December 10, 1991. For a U.S. patent subject to the pre-June 8, 1995 term regime, the ordinary term was 17 years from grant. On that basis, the patent term ended on December 10, 2008. [1]

Event	Date or period
Patent issued	December 10, 1991
Ordinary statutory term	17 years from issue
Ordinary expiration	December 10, 2008
Current status for ordinary patent-term analysis	Expired

The analysis assumes no unusual terminal disclaimer, reissue effect, or other event that altered the ordinary term. A patent issued in 1991 would not receive the modern 20-year-from-earliest-effective-filing-date term applicable to later U.S. applications.

What is the Orange Book status of Patent 5,070,877?

Patent 5,070,877 is a diagnostic method-of-use patent. It is not a patent on the adenosine molecule, an injectable composition, a vial, a prefilled syringe, or a manufacturing process.

The FDA Orange Book lists patents associated with approved drug products when the listed patents meet FDA listing requirements. A diagnostic-use patent may be listed only if it is properly associated with the approved product and satisfies the applicable statutory and regulatory criteria. Patent 5,070,877 should not be treated as an active Orange Book barrier to adenosine or regadenoson without a product-specific FDA listing record. [2]

Even if the patent had been listed historically, its expiration in 2008 eliminates current Paragraph IV exposure based on this patent.

Did the patent create a Paragraph IV challenge risk?

During its active term, a generic applicant seeking approval for a product whose labeled use practiced the claimed diagnostic method could have evaluated a Paragraph IV certification if the patent appeared in the relevant Orange Book listing.

The practical risk would have depended on:

Whether the patent was listed for the relevant product.
Whether the generic label included the patented diagnostic use.
Whether the product’s intended use required the claimed dose and route.
Whether the applicant pursued a section viii statement carving out the patented use.
Whether the claims were valid and enforceable.

Today, Patent 5,070,877 cannot provide a live Paragraph IV block because its ordinary term has ended. A generic applicant would instead assess later patents, regulatory exclusivity, labeling, and product-specific patents.

Which companies are challenging the patent?

No active challenge can be inferred from the supplied claims. Because the patent expired in 2008, current litigation based solely on Patent 5,070,877 would not ordinarily present a live infringement dispute.

Historical litigation, assignments, reexaminations, terminal disclaimers, and maintenance-fee records require review of the USPTO Patent Center file and PACER. Those records are separate from the claim text and are not established by the information supplied here.

How strong is the patent estate for adenosine stress testing?

The patent was commercially important as a broad early method patent, but its current exclusionary strength is zero because the patent has expired.

Historical strengths

Broad coverage of IV and intracoronary pharmacologic coronary dilation.
Coverage of multiple diagnostic objectives.
Coverage of multiple imaging modalities.
Specific protection for adenosine, thallium-201, scintigraphy, echocardiography, and Doppler flow testing.
Claims directed to both clinical diagnosis and physiologic assessment.

Historical weaknesses

Functional language such as "sufficient to provide coronary artery dilation."
Broad diagnostic terms such as "myocardial dysfunction."
Multiple drafting inconsistencies.
Potential enablement and written-description issues across a broad agonist and imaging-method genus.
Possible anticipation or obviousness issues based on pre-filing use of adenosine, dipyridamole, and other pharmacologic stress agents.
Method claims requiring proof that each clinical step was performed for the claimed diagnostic purpose.

Current strength

The patent has no remaining blocking value in the United States after expiration. Its concepts may still be relevant as prior art against later patents claiming pharmacologic stress testing, dosing, tracer combinations, or imaging workflows.

How does this patent compare with later competing estates?

Technology	Primary protection historically expected	Relationship to Patent 5,070,877
Adenosine injection	Drug product, formulation, manufacturing, labeling, and diagnostic use	Patent 5,070,877 covers a diagnostic method, not the molecule itself
Dipyridamole stress testing	Method of inducing pharmacologic stress and related products	Competing diagnostic approach
Regadenoson/Lexiscan	Composition, formulation, dosing, receptor selectivity, and stress-imaging use	Later-generation alternative; separate patent estate
PET myocardial perfusion agents	Radiopharmaceutical composition, preparation, and imaging use	May overlap conceptually with the expired method claims, but later rights require separate analysis
Echocardiographic stress systems	Device, software, imaging workflow, or contrast-agent patents	Patent 5,070,877 does not claim a specific device
Coronary flow measurement	Catheter, sensor, signal processing, and diagnostic methods	Patent 5,070,877 claims the pharmacologic stimulus and measurement objective

What generic launch risks exist today?

Patent 5,070,877 creates no current U.S. generic launch risk. A present-day applicant evaluating adenosine injection would focus on:

Active product patents, if any.
FDA-listed patents for the specific reference-listed drug.
Injectable formulation and container-closure patents.
Manufacturing and purification patents.
Labeling restrictions.
Drug shortage and supply-chain requirements.
Applicable FDA exclusivity periods.

For regadenoson, the relevant analysis is separate. Regadenoson is a small molecule, so biosimilar law does not apply. A competing product would proceed through the generic-drug pathway rather than the biologics biosimilar pathway, subject to product-specific FDA requirements. [3]

What geographic coverage remains?

The patent’s enforceable rights were limited to the United States. Foreign counterparts, if any, would have had separate national terms and could have expired on different dates. The U.S. patent cannot block diagnostic protocols performed outside the United States.

International freedom-to-operate analysis would require review of family members in jurisdictions such as Europe, Canada, Japan, and Australia. The supplied claim text does not establish the existence, status, or expiration of any foreign counterpart.

Key Takeaways

U.S. Patent 5,070,877 is a diagnostic method patent covering adenosine-receptor-agonist-induced coronary vasodilation followed by myocardial or coronary-flow assessment.
The principal targets are coronary artery disease, ventricular dysfunction, and coronary flow reserve.
The patent covers IV and intracoronary administration and lists adenosine, multiple adenosine analogs, and related purines.
Specific claims cover thallium-201 scintigraphy, echocardiography, and Doppler flow catheter testing.
Claim 28 contains a material IV-route and dose-range inconsistency.
The patent issued December 10, 1991 and ordinarily expired December 10, 2008.
It has no current U.S. blocking value and should not create a live Paragraph IV or generic-entry barrier.
Biosimilar risk is irrelevant because adenosine and regadenoson are small molecules.
Later patents covering regadenoson, formulations, radiopharmaceuticals, imaging devices, and manufacturing processes must be analyzed separately.

FAQs

Does Patent 5,070,877 cover adenosine injection itself?

No. It covers specified diagnostic uses of an adenosine receptor agonist. It does not claim the adenosine molecule, a standalone injectable composition, or the manufacture of adenosine.

Does the patent cover pharmacologic stress testing with regadenoson?

The broad claims use the term "adenosine receptor agonist," which could raise a historical claim-scope question for regadenoson. The patent is expired, so the issue has no current U.S. blocking effect.

Can a generic company use the patented adenosine stress protocol?

Yes, from a Patent 5,070,877 perspective, because the patent’s ordinary U.S. term ended in 2008. Other active patents and FDA requirements may still apply to the product or label.

Is thallium-201 protected by the patent today?

No. The claims once covered specified diagnostic combinations using thallium-201, adenosine, and scintigraphy. The patent’s expiration ended that exclusivity.

Does the patent cover coronary CT angiography or modern cardiac MRI protocols?

Only to the extent a protocol satisfies the issued claim language. The patent lists certain imaging modalities, but it does not automatically cover every modern CT, MRI, perfusion, software, or image-analysis workflow.

References

U.S. Patent and Trademark Office. (1991). U.S. Patent No. 5,070,877.
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application process and generic drug requirements.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	1305922	⤷ Start Trial
European Patent Office	0354638	⤷ Start Trial
Japan	2914454	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 5,070,877