United States Patent 6,765,117: Claim Scope, Exclusivity, Litigation Risk, and Patent Landscape

United States Patent 6,765,117 covers stereoselectively produced 9-deoxy-PGF1-type compounds and pharmacologically acceptable salts made through intramolecular cyclization of an enyne. The patent is principally a chemical-compound and product-by-process patent, not a conventional treatment-method patent. Claim 2 narrows the estate to one oxygen-containing, carboxylic-acid compound with an ethylene side chain, a butyl substituent, and a defined hydroxyl stereochemistry.

The supplied claim text contains OCR and transcription defects, including inconsistent numbering, missing structural drawings, and apparent errors in the definitions of M1 and R7. Those defects materially limit exact structure-to-drug identification. The claim language alone does not establish an FDA-approved product, Orange Book listing, active patent term, patent-family scope, licensing history, or litigation outcome.

What does United States Patent 6,765,117 protect?

The patent protects a class of 9-deoxy-PGF1-type compounds defined by both chemical structure and manufacturing process.

The core elements are:

Claim element	Scope
Product class	Stereoselectively produced 9-deoxy-PGF1-type compounds
Core process	Intramolecular cyclization of an enyne
Ring heteroatom Z	O, S, CH2, or NR8
R8	Hydrogen, alkyl, or aryl
X	Hydrogen, cyano, OR9, or COOR9
n	0, 1, 2, or 3
Y1 linker	Trans-alkene, cis-alkene, saturated chain, or alkyne
M1	Defined hydroxyl, protected hydroxyl, hydrogen, or methyl stereochemistry
L1	Hydrogen, methyl, or fluoro stereochemical combinations
R7	Alkyl, phenoxy, substituted phenoxy, aryl, substituted aryl, alkenyl, hydroxyalkyl, or terpenoid-type substituents
Salt form	Pharmacologically acceptable salts in claim 4

The claim set therefore covers a broad Markush genus rather than one narrowly identified active pharmaceutical ingredient.

How broad is claim 1?

Claim 1 combines:

A defined 9-deoxy-PGF1-type molecular framework.
A stereochemical configuration at multiple positions.
Broad alternatives for the ring atom, side chains, linkers and substituents.
A process limitation requiring production through intramolecular enyne cyclization.

The R7 definition is especially expansive. It includes straight-chain alkyl groups, substituted phenoxy groups, substituted aromatic groups, unsaturated chains, hydroxyalkyl groups and selected heterocyclic or cycloalkyl structures. The claim also allows several alternative L1 and M1 stereochemical arrangements.

The practical scope depends on the omitted structural formulas. Chemical patent claims of this type often use the drawings to establish ring numbering, attachment points and stereochemical orientation. Without those drawings, the words alone cannot resolve whether particular prostaglandin analogs fall within the genus.

What does claim 2 cover?

Claim 2 is the most commercially specific claim in the supplied text. It narrows claim 1 to a compound having:

Z as oxygen;
n equal to 1;
X as COOH;
Y1 as -CH2CH2-;
M1 as alpha-OH:beta-R5;
R5 as hydrogen;
L1 with R3 and R4 both hydrogen;
R7 as butyl.

In functional terms, claim 2 is directed to a specific oxygen-containing 9-deoxy-PGF1-type carboxylic acid with a defined hydroxyl stereochemistry and a butyl side chain. It is substantially narrower than claim 1 and could provide stronger validity against prior art if the exact stereoisomer and process limitation are adequately supported.

The claim does not, on its face, cover every salt, ester, prodrug or formulation of the claim 2 acid. Claim 4 separately addresses pharmacologically acceptable salts, but its scope is independently dependent on the precise salt-language construction.

What do claims 3 and 4 add?

What is the scope of claim 3?

Claim 3 appears to duplicate much of claim 1 while changing the drafting of the X and R7 definitions. It also contains apparent OCR errors, including:

"steroselectively" instead of "stereoselectively";
"PFG1" instead of "PGF1";
"lydrogen" instead of "hydrogen";
"bnezyl" instead of "benzyl";
duplicated or renumbered R7 alternatives;
inconsistent chemical notation.

Claim 3 should not be treated as a reliable substitute for the issued claim without comparison against the official patent document. If claim 3 is materially identical to claim 1, it may create redundancy rather than a distinct commercial exclusion. If the issued language differs, the enforceable scope must be determined from the official patent claims, specification and prosecution history.

What is the scope of claim 4?

Claim 4 covers pharmacologically acceptable salt forms of the claimed 9-deoxy-PGF1-type compounds. Its apparent purpose is to extend coverage from the free acid or neutral compound to salts formed with pharmacologically acceptable cations.

The salt claim may be relevant to:

sodium, potassium, calcium or other pharmaceutically acceptable salts;
formulation intermediates;
aqueous or injectable dosage forms;
manufacturing processes using a salt rather than the free acid.

The supplied text contains an apparent error in the M1 definition, stating "alpha-OH:beta-R4" where the surrounding claims use R5. That error could affect claim construction. Courts generally interpret a claim in light of the specification and prosecution history, but an ambiguous or internally inconsistent limitation can create litigation risk under definiteness, written-description and claim-construction doctrines.

Is Patent 6,765,117 a product patent or a process patent?

The claims are hybrid product-by-process claims.

The claimed subject is a compound "that is produced by" a process involving intramolecular cyclization of an enyne. The claim therefore recites both:

the identity and stereochemistry of the compound; and
the process used to make it.

Under United States patent law, a product-by-process limitation can limit the scope of the claim for infringement even when the product itself is described structurally. The Federal Circuit has treated the process language as relevant to infringement, while patentability is generally assessed by whether the claimed product is structurally or functionally distinct from the prior art, not merely because it was made by a different process (Abbott Laboratories v. Sandoz, Inc., 2009).

The result is a two-part risk profile:

Issue	Commercial implication
Same compound, different process	Potential noninfringement argument, depending on claim construction
Different compound made by the claimed process	Usually outside the product limitation
Same compound made through enyne cyclization	Higher infringement exposure
Salt or ester of the compound	Covered only if the relevant claim language reaches that derivative
Generic process using a different cyclization route	May avoid the process limitation but requires technical proof

A freedom-to-operate analysis would require the complete specification, prosecution history, issued claims and accused manufacturing route.

When does Patent 6,765,117 lose exclusivity?

The exact expiration date cannot be established from the supplied claim text. United States Patent 6,765,117 was issued in 2004. For a post-1995 United States utility patent, the ordinary term is generally 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers and other statutory adjustments (35 U.S.C. §§ 154 and 156).

The relevant exclusivity categories are separate:

Exclusivity type	Relevance to this patent
Patent term	Depends on filing date and adjustments
FDA small-molecule exclusivity	Depends on an approved NDA, not the patent number
New chemical entity exclusivity	Five years if applicable
Three-year approval exclusivity	May apply to certain supplemental approvals
Orphan-drug exclusivity	Seven years if applicable
Pediatric exclusivity	Six-month extension if granted
Patent-term extension	May add time for regulatory review of an approved product

Patent 6,765,117 does not establish FDA exclusivity by itself. A patent can expire while regulatory exclusivity remains, and an FDA exclusivity period can end while later-expiring patents continue to restrict entry.

On the available information, the patent should be treated as an older patent whose ordinary term may have ended or be close to ending, but the precise legal status cannot be stated from the claims alone.

What is the Orange Book status of Patent 6,765,117?

The Orange Book status cannot be inferred from the patent number or claim text.

Orange Book listing requires a connection to an approved drug application and a patent that meets FDA listing requirements. The relevant categories generally include patents covering:

the drug substance;
the drug product or formulation;
approved methods of use.

A broad chemical patent may be absent from the Orange Book if:

no corresponding NDA was approved;
the patent was never submitted for listing;
the claimed compound was not the approved active ingredient;
the patent did not claim the approved formulation or method of use;
the FDA determined that the patent was not listable.

The supplied claims do not contain a treatment indication, dosage regimen, formulation, tablet, capsule, injectable composition or device. They therefore do not resemble a conventional method-of-use or formulation patent. They are more consistent with a compound and manufacturing patent.

Does the patent create biosimilar risk?

No conventional biosimilar pathway is implicated.

The claims cover small-molecule chemical compounds, not proteins, antibodies or other biological products. A follow-on manufacturer would ordinarily pursue an abbreviated new drug application, a 505(b)(2) application or a full NDA, depending on the product and degree of difference. The Public Health Service Act biosimilar pathway is not the normal route for a prostaglandin-type small molecule.

The relevant competitive risks are generic entry, 505(b)(2) entry and non-infringing alternative synthesis.

What Paragraph IV challenges could arise?

A Paragraph IV certification could arise only if the patent were listed in the Orange Book for an approved product and remained relevant to the applicant's product. A challenger could assert that:

the claims are invalid;
the proposed product does not infringe;
the patent is unenforceable;
the patent is not properly listable;
the applicant's compound is outside the claimed stereochemical or structural genus;
the applicant uses a process outside the claimed enyne-cyclization limitation.

Potential invalidity theories include:

anticipation by an earlier 9-deoxy-PGF1 compound;
obviousness based on known prostaglandin analogs and enyne cyclization;
inadequate written description across the broad Markush genus;
lack of enablement for the full range of R7, Z, X, Y1, M1 and L1 alternatives;
indefiniteness caused by inconsistent stereochemical definitions or drafting errors.

The broad genus and product-by-process format create both invalidity and infringement arguments. A challenger would likely focus on whether the specification enables the full claimed chemical space and whether the exact stereoisomer was disclosed in the prior art.

What formulation and method-of-use protection does the patent provide?

The supplied claims do not expressly claim:

a pharmaceutical composition;
a tablet, capsule or injectable formulation;
a sustained-release delivery system;
a specific dosage;
a therapeutic indication;
a method of treating pulmonary hypertension, glaucoma, vascular disease or another condition;
a device or combination therapy.

Any formulation or method-of-use protection would have to arise from separate patents in the same family or related patent families. The supplied claims alone do not establish such protection.

How strong is the patent estate?

The patent has potentially meaningful chemical scope but limited apparent lifecycle value if its term has expired or is near expiration.

Factor	Assessment
Structural breadth	Broad, because of multiple Markush alternatives
Claim 2 specificity	Narrower and potentially easier to defend if supported
Stereochemical coverage	Significant; stereochemistry is central to the claims
Process limitation	Creates both a technical barrier and a possible noninfringement route
Formulation coverage	Not shown in the supplied claims
Method-of-use coverage	Not shown
Biosimilar relevance	Low
Generic relevance	Potentially significant if an approved product maps to the claims
Manufacturing barrier	Potentially meaningful where the enyne cyclization is commercially necessary
Validity risk	Elevated for broad genus, enablement and inconsistent text
Remaining value	Depends principally on legal term, approved-product linkage and family members

What patent litigation, licensing deals and settlements affect the patent?

No litigation, licensing transaction or settlement can be established from the supplied claims. Those issues require the patent's prosecution history, assignment records, related family members, court dockets and FDA product records.

The patent number alone does not show:

whether the patent was asserted;
whether a Paragraph IV notice was served;
whether a generic applicant challenged it;
whether a case settled;
whether rights were licensed;
whether a terminal disclaimer applies;
whether the patent was disclaimed or administratively corrected.

What are the likely generic launch scenarios?

Three launch scenarios are relevant:

A generic matches a claimed compound and uses the claimed enyne-cyclization process. This creates the highest infringement risk if the patent remains enforceable.
A generic matches the compound but uses a demonstrably different manufacturing route. The product-by-process language may support a noninfringement position, subject to claim construction and proof.
A generic uses a structurally different prostaglandin analog or a different salt outside the claims. The patent may not block launch, although separate patents could apply.

The principal commercial question is not whether the patent claims a broad prostaglandin class in the abstract. It is whether the approved or proposed active ingredient falls within the exact stereochemical structure and whether the manufacturing process satisfies the claim limitation.

Key Takeaways

Patent 6,765,117 claims stereoselectively produced 9-deoxy-PGF1-type compounds.
Claims 1 and 3 are broad Markush product-by-process claims.
Claim 2 is a substantially narrower compound claim centered on an oxygen-containing carboxylic acid with a butyl substituent.
Claim 4 extends the claimed subject matter to pharmacologically acceptable salts.
The patent does not, based on the supplied claims, provide clear formulation, device or method-of-use protection.
It is a small-molecule patent and does not create conventional biosimilar risk.
Orange Book listing, Paragraph IV exposure, litigation, licensing and exact expiration cannot be determined from the claim text.
The omitted structural drawings and apparent OCR errors are material to claim construction.
The principal generic strategy would be to challenge validity, avoid the claimed stereochemical structure, or use a manufacturing route outside the enyne-cyclization limitation.

FAQs

What drug is associated with United States Patent 6,765,117?

The supplied claims do not identify a marketed drug by name. The claimed genus consists of 9-deoxy-PGF1-type prostaglandin analogs, but the omitted structural drawings prevent reliable mapping to a specific active ingredient.

Can a generic avoid Patent 6,765,117 by using a different synthesis?

Potentially. Because the claims include a product-by-process limitation, a different manufacturing route may support a noninfringement position. The result depends on the issued claim language, prosecution history and actual process used.

Does claim 2 cover the free acid or only a salt?

Claim 2 expressly recites X as COOH and therefore appears directed to the free carboxylic acid. Claim 4 separately addresses pharmacologically acceptable salt forms, although its defective transcription requires confirmation against the issued patent.

Are prostaglandin formulations protected by this patent?

No formulation protection is apparent from the supplied claims. The claims do not recite excipients, dosage forms, release profiles, devices or specific pharmaceutical compositions.

Could the patent block a 505(b)(2) application?

It could if the proposed product falls within an enforceable claim and the patent is listed or otherwise relevant to the regulatory strategy. The claims alone do not establish an approved product, Orange Book listing or remaining enforceable term.

References

Abbott Laboratories v. Sandoz, Inc., 566 F.3d 1282 (Fed. Cir. 2009).
Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
United States Patent No. 6,765,117. (2004). 9-Deoxy-PGF1-type compounds. United States Patent and Trademark Office.
United States Code, Title 35, §§ 154 and 156.
United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure. U.S. Department of Commerce.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	245628	⤷ Start Trial
Canada	2307163	⤷ Start Trial
Canada	2847985	⤷ Start Trial
China	1264819	⤷ Start Trial
China	1283184	⤷ Start Trial
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Details for Patent: 6,765,117

Summary for Patent: 6,765,117