US Patent 6,589,960: Hydromorphone Composition Claims, Expiration, and Patent Landscape

US Patent 6,589,960 covers hydromorphone compositions defined by impurity concentrations and manufacturing processes that convert morphine to hydromorphone using acid and palladium in the substantial absence of hydrogen gas. The patent does not claim hydromorphone generally, a particular dosage form, a controlled-release tablet, or a method of treating pain. Its commercial scope was concentrated on hydromorphone active pharmaceutical ingredient, impurity specifications, and process conditions.

The patent issued on July 8, 2003. Its ordinary US patent term expired in 2020 based on the application and priority record. It therefore does not create current US patent exclusivity for hydromorphone products. Any present-day barrier would have to arise from a different patent, regulatory exclusivity, controlled-substance requirements, manufacturing know-how, or an unexpired foreign right.

What does US Patent 6,589,960 protect?

The patent has four principal claim groups:

Claim group	Claims	Subject matter
Impurity-profile compositions	1-8, 15-17, 26, 28	Hydromorphone containing specified ranges of dihydromorphine, morphine, 8-hydroxy hydromorphone, bis-hydromorphone, and other impurities
Process-defined compositions	9-17, 27-29	Hydromorphone compositions prepared through specified acid, catalyst, heating, and hydrogen-exclusion conditions
Purification or conversion methods	18-25	Heating aqueous hydromorphone mixtures to reduce 8-hydroxy hydromorphone
Narrow composition examples	7-8	Tightly defined impurity profiles, including the approximately 0.26% dihydromorphine composition

The independent claims are claims 1, 7, 8, 15, 16 and 18. Claims 9 through 14 and 27 through 29 add manufacturing limitations to composition claims. Claims 18 through 25 are method claims.

What impurity ranges are covered by the patent?

Claim 1 establishes the broadest stated impurity profile:

Component	Claim 1 range
Dihydromorphine	About 0.05% to about 1.0%
Morphine	Up to about 0.1%
8-hydroxy hydromorphone	Up to about 0.8%
Bis-hydromorphone	Up to about 0.5%
Other impurities	Up to about 0.2%

Claim 2 narrows the dihydromorphine concentration to approximately 0.05% to 0.5%. Claims 3 through 6 narrow the maximum concentrations of the other listed impurities.

Claim 7 is materially narrower:

Component	Claim 7 range
Dihydromorphine	About 0.22% to about 0.29%
Morphine	Up to about 0.02%
8-hydroxy hydromorphone	About 0.04% to about 0.05%
Bis-hydromorphone	Up to about 0.02%
Other impurities	Up to about 0.06%

Claim 8 recites an approximately fixed impurity profile:

About 0.26% dihydromorphine
About 0.01% morphine
About 0.04% 8-hydroxy hydromorphone
About 0.02% bis-hydromorphone
About 0.06% other impurities

The patent’s commercial theory appears to be that hydromorphone made through a particular morphine conversion route has a recognizable impurity fingerprint. The claims attempt to capture both the fingerprint and the process that produces it.

How broad are the composition claims?

The composition claims are broad in subject matter but limited by numerical ranges.

Claim 1 requires all five impurity categories. A hydromorphone sample outside any one of the claimed limits would not literally satisfy claim 1. For example, a sample containing 1.1% dihydromorphine, 0.15% morphine, or 0.25% other impurities would fall outside claim 1 as written.

Claim 15 is potentially broader because it requires hydromorphone, dihydromorphine at approximately 0.05% to 1.0%, and one or more compounds selected from morphine, 8-hydroxy hydromorphone, bis-hydromorphone, and other impurities. Unlike claim 1, it does not require every listed impurity category to be present or impose the full set of individual upper limits.

Claim 16 recites a hydromorphone composition “substantially free of impurities.” Claim 17 then narrows that concept by reciting the same impurity ranges found in claim 1. The relationship between “substantially free” and the permitted impurity levels would depend heavily on the patent specification and the court’s construction of the term.

The claims do not require a dosage form

The composition claims do not expressly require:

Tablets
Capsules
Injectable solutions
Extended-release systems
A specific hydromorphone salt
A particular excipient
A particular strength
A therapeutic indication

As a result, the claims are directed primarily to drug substance or a composition containing hydromorphone and specified impurities. A finished dosage form could implicate the claims if the hydromorphone component met the claimed profile, but the claims do not independently protect the dosage-form technology.

What manufacturing process does US 6,589,960 claim?

Claims 9 through 14 and claims 20 through 25 focus on conversion of morphine to hydromorphone.

The principal process limitations are:

Morphine is mixed with an acid.
A catalyst is present.
The process is conducted in the substantial absence of hydrogen gas.
The mixture is heated.
Heating reduces 8-hydroxy hydromorphone below approximately 1.0%.
In certain claims, dihydromorphine is reduced to 2.0% or less.
The acid may be hydrochloric acid.
The catalyst may be non-supported palladium.
The aqueous hydromorphone salt may be a bisulfite salt.

The most commercially relevant process combination is therefore:

Morphine or a morphine salt + hydrochloric acid + non-supported palladium + substantial absence of hydrogen gas + heating in an aqueous system.

This is narrower than a generic claim to catalytic hydrogenation or a generic claim to hydromorphone manufacture. A competing process using supported palladium, a different catalyst, a different acid, gaseous hydrogen, or a different purification route could avoid one or more express limitations. The doctrine of equivalents could still be relevant in litigation, but the patent’s expired status removes current US enforcement exposure.

What is the significance of the 8-hydroxy hydromorphone limitation?

The patent treats 8-hydroxy hydromorphone as a process-related impurity that can be reduced through heating. Claim 18 covers heating an aqueous mixture containing:

A hydromorphone salt
8-hydroxy hydromorphone
Dihydromorphine

The heating period must be sufficient to reduce 8-hydroxy hydromorphone below approximately 1.0%. Claims 23 and 24 add time limitations of more than 30 minutes and at least five hours.

This structure creates two possible infringement theories under the issued claims:

A composition theory, based on the final impurity profile.
A process theory, based on the steps used to create or purify the hydromorphone.

A manufacturer could avoid the process claims while still producing a composition that falls within claims 1, 7, 8, 15, 16, or 17. Conversely, a process could satisfy the process claims even if the resulting material does not meet every broad composition limitation.

Are the claims internally consistent?

Several drafting issues affect claim interpretation and freedom-to-operate analysis.

Dihydromorphine versus dihydromorphone

Claims 1 through 8 primarily recite dihydromorphine. Claims 10 and 11 refer to “dihydromorphone,” while claim 18 also uses dihydromorphone. These compounds are chemically distinct. The specification, prosecution history, and any certificate of correction would be important in determining whether the terminology reflects an intentional distinction or an error.

“About” ranges

The claims repeatedly use “about,” including:

About 0.05%
About 1.0%
About 0.26%
About 0.04%
About five hours

The permitted analytical tolerance would depend on the patent specification, assay precision, industry practice, and the prosecution record. A sample at 0.049% or 0.051% cannot be assessed solely from the claim text.

“Substantially free of impurities”

Claim 16 uses a qualitative limitation, while claim 17 permits specified impurity concentrations. The phrase may not mean absolute absence. Its construction would likely turn on how the patent defines impurity content and whether the specification provides a quantitative benchmark.

Claim 23 drafting issue

Claim 23 states “the composition of claims 18,” although claim 18 is a method claim. This appears to be a dependency or drafting defect. Its effect would require review of the issued patent record and any correction or prosecution-history treatment.

When did US Patent 6,589,960 lose exclusivity?

Event	Date
US application filing and priority record	2000-era filing record
Patent issued	July 8, 2003
Ordinary 20-year US term	Expired in 2020
Current enforceable patent term	No longer active in the United States

US utility patents generally expire 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory adjustments. Patent 6,589,960 is no longer a live US exclusivity right based on its term record. The patent’s expiration does not invalidate historical rights during the active term, but it prevents a new infringement action based solely on the expired patent.

What is the Orange Book status of US 6,589,960?

Patent 6,589,960 is not, by its claim structure, a conventional Orange Book product patent. It does not claim a specific approved hydromorphone tablet, capsule, injectable presentation, or extended-release dosage form. It is directed to impurity-defined hydromorphone compositions and manufacturing methods.

The FDA Orange Book can list patents submitted by an NDA holder for an approved drug. Such listings may include drug substance, drug product, formulation, or method-of-use patents. The patent number itself should therefore be checked against the FDA’s current Orange Book data rather than inferred from the patent claims. Its expiration means that any historical listing would not create current patent exclusivity.

The relevant commercial products include immediate-release hydromorphone products such as Dilaudid and extended-release products such as Exalgo. Those products may have had separate formulation, dosage, method-of-use, or regulatory exclusivity positions. Patent 6,589,960 should not be treated as a substitute for a product-specific Orange Book review.

Did this patent create Paragraph IV risk for generic hydromorphone?

During its active term, an ANDA applicant could have faced a Paragraph IV issue if the patent was listed against the relevant reference-listed drug and the proposed product met the claimed composition or process limitations.

That risk would have depended on:

Whether the patent was listed in the Orange Book for the relevant NDA
Whether the ANDA product’s hydromorphone impurity profile fell within the claimed ranges
Whether the applicant used the claimed morphine conversion process
Whether the applicant certified that the patent was invalid, unenforceable, or not infringed
Whether the patent owner filed suit within the statutory period

The patent’s expiration eliminates a current Paragraph IV barrier based on this patent. A generic applicant no longer needs to establish non-infringement of an expired US patent to launch solely because of patent 6,589,960.

Which companies are challenging hydromorphone patents?

The supplied claim set does not identify a litigation party, settlement, license, or Paragraph IV challenger. The public patent record for US 6,589,960 should not be read as evidence of a particular generic challenge.

For current competition, the more relevant parties are:

Generic manufacturers filing ANDAs for hydromorphone tablets, oral solutions, injections, or extended-release products
NDA holders for branded hydromorphone products
API manufacturers producing hydromorphone hydrochloride
Contract manufacturers controlling validated impurity specifications and process knowledge

A company-by-company litigation conclusion cannot be assigned to patent 6,589,960 without a case-specific docket or FDA filing record. The patent itself is expired and does not presently block generic entry.

What licensing deals involve US 6,589,960?

No license is identified in the patent claims or basic bibliographic record. Patent ownership, assignment history, and commercial licensing are separate issues. A patent assignment does not establish a license, and a license does not necessarily appear in the patent file.

The patent’s practical value during its term would have been highest to a hydromorphone API producer or a branded manufacturer seeking control over impurity specifications and morphine-to-hydromorphone conversion technology. Its current licensing value is primarily historical or know-how related because the US patent term has ended.

How strong was the patent estate for hydromorphone?

US 6,589,960 was a focused patent rather than a broad platform patent.

Strength factor	Assessment
Active ingredient coverage	Narrow; hydromorphone compositions only
Composition coverage	Moderate where impurity ranges are met
Process coverage	Narrow to specified acid, catalyst, heating, and hydrogen-exclusion conditions
Dosage-form coverage	None expressly stated
Method-of-use coverage	None
Biologic or biosimilar relevance	None
Manufacturing relevance	Significant during the term
Current US enforceability	None after expiration
Design-around potential	Material, through different process conditions or impurity profile
Commercial blocking power today	None as an unexpired patent

The claims could have been difficult to design around if a manufacturer naturally generated the claimed impurity profile through the same non-hydrogen palladium process. The composition claims also created a potential product-based theory independent of the precise manufacturing route. Their weakness was the reliance on analytical impurity ranges and the absence of dosage-form or therapeutic-use claims.

What geographic coverage does the patent provide?

US Patent 6,589,960 provides rights only in the United States. It does not establish rights in:

Canada
Europe
Japan
China
India
Australia
Other jurisdictions

International coverage would require corresponding national or regional patents from the same priority family. Each foreign right would have its own prosecution history, claim scope, term, lapse status, and enforcement record. A US expiration does not automatically determine the status of foreign family members.

What generic launch scenarios exist?

Immediate-release hydromorphone

For an immediate-release generic, this patent is no longer a US launch barrier. The key issues are FDA approval, controlled-substance compliance, bioequivalence, drug-substance quality, and any separate unexpired product or method-of-use patents.

Extended-release hydromorphone

Extended-release products require a separate review of release-control technology, formulation patents, abuse-deterrent features, and Orange Book listings. Patent 6,589,960 does not claim an extended-release system.

Injectable hydromorphone

Injectable products may involve sterile manufacturing, preservative systems, container-closure systems, and product-specific regulatory requirements. The expired impurity patent does not independently block an injectable launch.

API manufacture

An API manufacturer should still assess whether its process reproduces the claimed impurity profile for historical freedom-to-operate documentation, technical benchmarking, or foreign patent review. In the United States, the expired patent does not support a current infringement claim.

Key Takeaways

US Patent 6,589,960 covers hydromorphone impurity profiles and related morphine-conversion and heating processes.
The broadest profile includes approximately 0.05% to 1.0% dihydromorphine, with limits on morphine, 8-hydroxy hydromorphone, bis-hydromorphone, and other impurities.
The narrowest composition claims center on approximately 0.26% dihydromorphine and tightly controlled secondary impurities.
Process claims focus on acid, non-supported palladium, aqueous heating, and the substantial absence of hydrogen gas.
The patent does not expressly claim hydromorphone tablets, extended-release technology, injectable dosage forms, or therapeutic uses.
The US patent term expired in 2020.
The patent does not create current US Paragraph IV or generic-entry risk.
Orange Book, litigation, settlement, licensing, and foreign-family analysis must be conducted separately from the issued claim text.
The principal remaining commercial issues are API manufacturing know-how, product-specific patents, regulatory requirements, and foreign patent-family status.

FAQs About US Patent 6,589,960

Does US 6,589,960 cover all hydromorphone products?

No. It covers only hydromorphone compositions and methods that satisfy the specified impurity or process limitations. It does not claim hydromorphone generally.

Can a generic manufacturer launch hydromorphone despite this patent?

Yes, the US patent term expired in 2020. A launch still requires FDA approval and compliance with any other unexpired patents or regulatory requirements.

Does the patent cover hydromorphone hydrochloride?

Certain method claims refer to a hydromorphone salt and specifically identify bisulfite in dependent claim 25. The claims do not broadly claim every hydromorphone hydrochloride product.

Is 8-hydroxy hydromorphone a formulation ingredient under the patent?

No. It is treated as an impurity or process-related component. The claims use its concentration as part of the composition definition or as a parameter reduced through heating.

Does the patent have biosimilar relevance?

No. Hydromorphone is a small-molecule opioid, not a biologic. Biosimilar approval and Purple Book analysis do not apply.

References

United States Patent and Trademark Office. (2003). US Patent No. 6,589,960, Hydromorphone compositions and methods of making same. https://patents.google.com/patent/US6589960
United States Patent and Trademark Office. (n.d.). Patent term calculator. https://www.uspto.gov/patents/laws/patent-term-calculator
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, 44th edition. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application approvals and patent certifications. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/anda-process-data-management-system-admss/paragraph-iv-drug-product-list-dispute-and-suit-information-filing-dates-controls-and-30-month-stays

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	402937	⤷ Start Trial
Austria	500257	⤷ Start Trial
Australia	1595701	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,589,960

Summary for Patent: 6,589,960