U.S. Patent 4,584,187: Scope, Claims, Expiration, and the Iobenguane I-123/I-131 Patent Landscape

U.S. Patent 4,584,187 covers radioiodinated meta-iodobenzylguanidine, commonly known as radioiodinated MIBG or iobenguane, using iodine-123 or iodine-131. Its claims extend to the radioactive compounds, buffered pharmaceutical compositions, diagnostic imaging of the heart and adrenal medulla, and therapeutic treatment of tumors with iodine-131 MIBG. The patent issued on April 22, 1986, and expired in 2003 under the pre-1995 U.S. patent-term regime. It is no longer a blocking patent for current iobenguane products.

The patent remains important as the foundational U.S. patent for MIBG radiopharmaceutical use. Its commercial relevance now lies in historical origin, freedom-to-operate analysis, and the separation of expired foundational rights from later patents directed to manufacturing, formulation, dosimetry, and specific therapeutic indications.

What patent is U.S. Patent 4,584,187?

U.S. Patent 4,584,187 is titled “Radioiodinated meta-iodobenzylguanidine.” The patent was assigned to the Regents of the University of Michigan and is associated with the development of MIBG for imaging and treatment of tissues derived from the adrenal medulla.

Item	Detail
U.S. patent	4,584,187
Title	Radioiodinated meta-iodobenzylguanidine
Filing date	1983
Issue date	April 22, 1986
Patent term	17 years from issue under the pre-1995 statutory regime
Expiration	April 22, 2003
Core technology	Iodine-123 and iodine-131 MIBG
Principal uses	Diagnostic imaging and therapeutic treatment
Relevant products	AdreView and Azedra
Current blocking status	Expired

The patent describes MIBG as a norepinephrine analogue that is taken up by sympathetic adrenergic tissue. Iodine-123 MIBG is primarily used for diagnostic imaging. Iodine-131 MIBG is used both for imaging and for targeted radiotherapy because iodine-131 emits beta radiation.

What compounds are protected by Patent 4,584,187?

Claims 1 through 3 cover the radioiodinated MIBG compounds themselves.

Claim 1 covers radioiodinated meta-iodobenzylguanidine in which the iodine isotope is either iodine-123 or iodine-131. Claims 2 and 3 narrow that scope to the individual isotopes.

Claim	Subject matter	Scope
1	Radioiodinated MIBG	Iodine-123 or iodine-131
2	Iodine-123 MIBG	Diagnostic isotope
3	Iodine-131 MIBG	Diagnostic and therapeutic isotope

The compound claims are broad with respect to downstream use. They do not require a particular disease, formulation, dose, route of administration, or imaging instrument. A product containing the claimed isotope-labeled MIBG molecule would fall within the literal scope of the compound claims during the patent term.

The claims are directed to the radioiodinated form of MIBG, not to every possible MIBG precursor, unlabeled intermediate, isotope-labeling reagent, or manufacturing process. The patent does not claim all norepinephrine analogues or all radiolabeled guanidines.

What pharmaceutical compositions are protected by the patent?

Claims 4 through 10 cover radiopharmaceutical compositions containing radioiodinated MIBG and a carrier.

Claim 4 is the broad composition claim. Claim 5 identifies physiological buffered saline as the carrier. Claims 6 and 7 distinguish iodine-123 and iodine-131 compositions. Claims 8 through 10 add radioactive-dose limitations.

Claim	Isotope	Dose limitation	Functional context
4	I-123 or I-131	None	Radiopharmaceutical with carrier
5	I-123 or I-131	None	Physiological buffered saline
6	I-123	None	Composition
7	I-131	None	Composition
8	I-123	About 1.0 to 3.0 mCi	Composition
9	I-131	About 0.2 to 1.0 mCi	Composition
10	I-131	About 100 to 200 mCi	Composition

The composition claims are not limited to a particular vial, excipient package, pH, stabilizer, radionuclidic purity, or manufacturing procedure. A later product with different excipients could still have raised infringement issues during the patent term if it contained the claimed radioiodinated MIBG and carrier.

The dose ranges show the patent’s dual diagnostic and therapeutic architecture:

Iodine-123 MIBG at approximately 1 to 3 mCi for imaging.
Iodine-131 MIBG at approximately 0.2 to 1.0 mCi for lower-dose imaging.
Iodine-131 MIBG at approximately 100 to 200 mCi for treatment.

The dose ranges are dependent claims. They narrow the broader composition claims and would not have been necessary to establish infringement of claim 4 if the broader claim were met.

What methods are protected by U.S. Patent 4,584,187?

Claims 11 through 17 cover radio-imaging methods. Claims 18 through 21 cover therapeutic treatment.

Diagnostic imaging claims

Claim 11 requires two principal steps:

Systemically administering a pharmaceutical composition containing radioiodinated MIBG to a human.
Detecting gamma radiation from the composition and forming an image.

Claim 12 narrows the carrier to physiological buffered saline. Claims 13 through 16 distinguish the isotope and dose. Claim 17 identifies the target organs or tissues.

Claim	Method	Key limitation
11	Human organ radio-imaging	Administration, gamma detection, image formation
12	Radio-imaging	Physiological buffered saline
13	Radio-imaging	I-123 MIBG
14	Radio-imaging	I-123 at about 1.0 to 3.0 mCi
15	Radio-imaging	I-131 MIBG
16	Radio-imaging	I-131 at about 0.2 to 1.0 mCi
17	Radio-imaging	Heart, adrenal medulla, or adrenal-medulla tumors

Claim 17 is narrower than claim 11 because it limits the imaged human organ or tissue to the heart, adrenal medulla, or tumors of the adrenal medulla. The claim does not expressly recite pheochromocytoma or paraganglioma by name, although tumors of the adrenal medulla can include pheochromocytoma.

Therapeutic treatment claims

Claim 18 covers systemic administration of radioiodinated MIBG to treat a tumor. Claim 19 adds physiological buffered saline. Claim 20 requires iodine-131 MIBG. Claim 21 narrows the iodine-131 dose to approximately 100 to 250 mCi.

Claim	Therapeutic scope
18	Systemic treatment of a tumor using radioiodinated MIBG
19	Claim 18 with physiological buffered saline
20	Claim 18 using iodine-131 MIBG
21	Iodine-131 MIBG at about 100 to 250 mCi

Claim 21 is particularly relevant to modern therapeutic MIBG because its 100-to-250 mCi range overlaps the high-dose treatment paradigm used in iodine-131 MIBG therapy.

When did Patent 4,584,187 lose exclusivity?

Patent 4,584,187 expired in April 2003. It is therefore available for practice without a license from the original patent owner, subject to any later, independently valid patents.

The expiration applies to all issued claims, including:

The iodine-123 MIBG compound.
The iodine-131 MIBG compound.
MIBG compositions with buffered saline.
Imaging methods.
Therapeutic tumor-treatment methods.
The specified diagnostic and therapeutic dose ranges.

The patent cannot now support a new infringement action based solely on practicing the issued claims. A company producing iobenguane I-123 or iobenguane I-131 must instead evaluate later patents, regulatory exclusivity, manufacturing rights, and any contract or licensing restrictions.

Patent expiration does not eliminate other forms of market protection. Later patents can cover a manufacturing process, a purified product, a formulation, a dosing schedule, a patient-selection method, or a specific approved indication.

What is the Orange Book status of the patent?

Patent 4,584,187 is expired and should not operate as a current Orange Book barrier to approval of a competing iobenguane product.

The FDA Orange Book lists patents and regulatory exclusivity associated with approved drug products. An expired foundational patent may remain historically relevant but does not prevent an abbreviated new drug application, 505(b)(2) application, or other applicable submission from relying on the expired technology. Current Orange Book analysis must be performed at the product level because later patents may be listed for a particular NDA.

For iobenguane products, the main regulatory distinction is:

AdreView is an iodine-123 diagnostic product.
Azedra is an iodine-131 therapeutic product.

The FDA approved AdreView in 2008 for localization of neuroendocrine tumors and evaluation of cardiac sympathetic innervation in patients with suspected or known pheochromocytoma or neuroblastoma-related disease. The FDA approved Azedra in 2018 for adults and pediatric patients age 12 and older with iobenguane scan-positive, unresectable, locally advanced or metastatic pheochromocytoma or paraganglioma requiring systemic anticancer therapy. (FDA, 2008; FDA, 2018)

What FDA exclusivity applied to MIBG products?

AdreView

AdreView received FDA approval as an iodine-123 diagnostic radiopharmaceutical. Its regulatory protection was based primarily on the NDA approval and any applicable statutory exclusivity, not on the expired 1986 patent.

Iodine-123 MIBG is a small-molecule radiopharmaceutical. It is not a biologic and therefore does not receive biosimilar exclusivity under the Public Health Service Act. A competing product would generally be evaluated through an abbreviated or 505(b)(2) pathway, depending on formulation, labeling, reference-product status, and the extent of reliance on the listed drug.

Azedra

Azedra received orphan-drug designation and approval for a defined pheochromocytoma and paraganglioma population. Orphan-drug exclusivity generally runs for seven years from approval for the same drug and indication. For a July 2018 approval, the primary seven-year period ran to approximately July 2025, subject to the statutory scope of the exclusivity and any regulatory events affecting the period.

Orphan exclusivity is not the same as patent exclusivity. It can block FDA approval of the same drug for the same disease or condition but does not prevent all forms of competition. A different drug, a materially different indication, or a legally permissible clinical development strategy may fall outside its scope.

Which companies are challenging the MIBG market?

The competitive market is divided between diagnostic iodine-123 MIBG and therapeutic iodine-131 MIBG.

Segment	Reference product	Competitive pathway
Diagnostic imaging	AdreView	Generic or 505(b)(2) iobenguane I-123
Therapeutic treatment	Azedra	505(b)(2), NDA, or other drug-specific pathway
Hospital-compounded MIBG	Radiopharmacy preparations	Process, quality, and regulatory compliance
Alternative imaging	FDG PET and other nuclear imaging agents	Clinical substitution rather than direct patent competition

The commercial barriers are technical as well as legal. A competing sponsor must establish radionuclidic identity, radiochemical purity, sterility, stability, specific activity, labeling consistency, radiation-safety controls, and reliable isotope supply.

A generic manufacturer also must address the short shelf life of radiopharmaceuticals. Iodine-123 has a half-life of approximately 13 hours, while iodine-131 has a half-life of approximately eight days. Distribution logistics can therefore be more important than conventional small-molecule tablet manufacturing.

What manufacturing and formulation IP barriers exist after expiration?

The expired patent does not eliminate potential protection around the production and commercial handling of MIBG. Later patent families may address:

Radioiodination of a MIBG precursor.
Purification of iobenguane after labeling.
Removal of unreacted iodine or precursor impurities.
Sterile filtration and vial filling.
Stabilization during transport.
Specific activity and radionuclidic purity.
Dosimetry and fractionated administration.
Patient selection based on tumor uptake.
Combination therapy or premedication.
Radiation-protection procedures.
Kit formulations or precursor formulations.

A freedom-to-operate review must separate three questions:

Is the active radiolabeled molecule covered by an unexpired composition patent?
Is the manufacturing process covered by an unexpired process patent?
Is the proposed label or dosing regimen covered by an unexpired method-of-use patent?

Patent 4,584,187 answers the first question only for the historical patent term. It does not provide current freedom to operate for every production route or clinical use.

How strong is the patent estate for iobenguane MIBG?

The foundational estate is legally weak today because its core patent expired more than two decades ago. Its historical claim breadth was substantial, but its remaining exclusionary value is zero.

Patent category	Patent 4,584,187 position	Current commercial significance
Active compound	Broadly covered I-123 and I-131 MIBG	Expired
Buffered formulation	Expressly covered	Expired
Diagnostic imaging	Broad human imaging method	Expired
Therapeutic use	Broad tumor-treatment method	Expired
Specific modern indication	Not expressly limited to current Azedra label	Requires later rights analysis
Manufacturing process	Not the principal claim focus	Later patents may matter
Regulatory exclusivity	Not created by the patent	Product-specific
Biosimilar protection	Not applicable	MIBG is a small molecule

The remaining strategic value is therefore concentrated in later product-specific rights and regulatory barriers. A company entering the diagnostic market may face different risks from a company entering therapeutic iodine-131 MIBG.

What generic launch risks exist for iodine-123 and iodine-131 MIBG?

Iodine-123 diagnostic launch

A competing iodine-123 product would likely face:

Demonstration of comparable imaging performance.
Radiochemical and radionuclidic specifications.
A short distribution window.
Hospital and nuclear-medicine adoption requirements.
Reference-product exclusivity or labeling constraints.
Any unexpired Orange Book-listed patents for the reference product.

Because the foundational compound claims expired, the main risks are regulatory execution, isotope supply, manufacturing reliability, and later product patents.

Iodine-131 therapeutic launch

A therapeutic entrant would face greater barriers:

Dosimetry and patient-specific treatment planning.
Inpatient or controlled radiation-management requirements.
Administration protocols.
Blood-count and organ-toxicity monitoring.
Specialized treatment centers.
Orphan-indication competition.
Potential method-of-use or formulation patents.
Long clinical-development timelines.

The high-dose therapeutic claim in Patent 4,584,187 is expired, so it does not prevent a new iodine-131 MIBG therapy. The commercial challenge is proving a safe, reproducible product and securing treatment-center adoption.

What litigation and Paragraph IV issues affect Patent 4,584,187?

Patent 4,584,187 is too old to support a current Paragraph IV dispute. A Paragraph IV certification applies to a patent listed in the Orange Book for an approved reference drug. An expired 1986 patent cannot create a present patent barrier.

Any current Paragraph IV dispute involving iobenguane would more likely concern:

A later formulation patent.
A method-of-use patent.
A manufacturing patent.
A dosing or administration patent.
A product-specific patent listed for AdreView or Azedra.

The existence of a Paragraph IV certification would not itself establish infringement or patent validity. The relevant analysis would require comparison of the proposed label and product attributes against each unexpired listed patent.

No current litigation consequence can be assigned to Patent 4,584,187 itself because its claims are expired.

How does the patent compare with current MIBG products?

Attribute	Patent 4,584,187	AdreView	Azedra
Isotope	I-123 and I-131	I-123	I-131
Primary use	Imaging and therapy	Diagnostic imaging	Therapeutic treatment
Patent issued	1986	Later product-specific rights may apply	Later product-specific rights may apply
Foundational patent status	Expired in 2003	Current regulatory product	Current regulatory product
FDA approval	N/A as a modern NDA product	2008	2018
Disease scope	Broad tumor and organ claims	Diagnostic localization and cardiac imaging	Pheochromocytoma and paraganglioma
Biosimilar pathway	Not applicable	Not applicable	Not applicable
Main competitive barrier	None from the patent	Regulatory and manufacturing requirements	Regulatory, clinical, manufacturing, and orphan-market barriers

What licensing deals are relevant to the patent?

The patent’s original institutional ownership made licensing commercially important during its term. Modern product rights, however, are associated with later commercialization arrangements rather than the expired foundational patent.

AdreView was commercialized by GE Healthcare. Azedra was developed by Progenics Pharmaceuticals and later became associated with the company’s oncology and radiopharmaceutical portfolio. The patent itself does not create a continuing royalty obligation after expiration unless a separate private contract contains independent obligations.

A licensee or acquirer should distinguish:

Patent licenses, which normally terminate or become royalty-free when the licensed patent expires unless the contract provides otherwise.
Know-how licenses, which may continue after patent expiration.
Regulatory-transfer agreements.
Manufacturing and supply agreements.
Trademark and commercialization rights.
Confidential technology rights.

What is the geographic coverage of Patent 4,584,187?

The patent provided protection only in the United States. Foreign counterparts, if any, required separate national filings and had separate terms and legal outcomes.

A U.S. patent does not control:

Manufacturing in Europe.
Distribution in Japan.
Clinical use in Canada.
Importation into another country.
Foreign patent rights owned by the same or a different assignee.

A global MIBG launch therefore requires country-by-country review of patent families, supplementary protection certificates, regulatory exclusivity, radiation regulations, and local product approvals. The U.S. expiration date cannot be used as a universal foreign expiration date.

Key Takeaways

U.S. Patent 4,584,187 covers iodine-123 and iodine-131 MIBG compounds, compositions, imaging methods, and therapeutic tumor-treatment methods.
The patent issued on April 22, 1986, and expired in April 2003.
Its compound claims were broad but are no longer enforceable.
The patent does not create a current Orange Book barrier or support a current Paragraph IV challenge.
AdreView is an iodine-123 diagnostic product approved in 2008.
Azedra is an iodine-131 therapeutic product approved in 2018 for pheochromocytoma and paraganglioma.
MIBG is a small molecule, so biosimilar rules do not apply.
Current freedom-to-operate risk depends on later manufacturing, formulation, dosing, method-of-use, and product-specific patents.
Generic entry is technically more difficult for iodine-131 therapy than for iodine-123 imaging because of dosimetry, radiation controls, and specialized treatment infrastructure.
The expired patent remains historically foundational but has no standalone exclusionary value today.

FAQs About U.S. Patent 4,584,187 and MIBG Exclusivity

Does U.S. Patent 4,584,187 cover Azedra?

It historically covered the iodine-131 MIBG active compound and therapeutic use, but it expired in 2003. It does not currently block Azedra or a competing iodine-131 MIBG product.

Does the patent cover both diagnostic and therapeutic MIBG?

Yes. The claims cover iodine-123 and iodine-131 MIBG. The imaging claims cover diagnostic use, while claims 18 through 21 cover therapeutic tumor treatment with radioiodinated MIBG, particularly iodine-131.

Can a company manufacture iodine-123 MIBG without licensing the patent?

Yes, the patent expired. The company must still evaluate later patents, FDA requirements, manufacturing controls, isotope supply, and any contractual restrictions.

Is MIBG subject to biosimilar approval?

No. Iobenguane MIBG is a chemically defined small-molecule radiopharmaceutical. Competing products are evaluated through applicable small-molecule drug pathways, not the biosimilar framework.

Does orphan exclusivity for Azedra extend beyond the patent expiration date?

Yes, orphan-drug exclusivity is independent of patent term. Azedra’s seven-year orphan period began with its 2018 approval and generally ran to approximately July 2025 for the protected indication, subject to the statutory scope of the exclusivity.

References

U.S. Patent No. 4,584,187. (1986). Radioiodinated meta-iodobenzylguanidine. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2008). AdreView prescribing information. FDA.
U.S. Food and Drug Administration. (2018). Azedra prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
U.S. Food and Drug Administration. (2024). Orphan drug designations and approvals database. FDA.
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term calculation resources. USPTO.

Details for Patent: 4,584,187

Summary for Patent: 4,584,187