United States Patent 5,284,858 Scope, Claims, and US Patent Landscape for Prostaglandin E Anti-Ulcer Agents

US Patent 5,284,858 claims a chemical genus of substituted Prostaglandin E analogs, with specific sub-genus embodiments including 13,14-dihydro-15-keto-PGE fluorinated at the 16-position and 13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1, and it ties that genus to both (i) composition claims for an anti-ulcer formulation and (ii) method-of-treatment claims for ulcer by administering an “anti-ulcer effective amount.” The patent’s enforceable scope is dominated by claim-1’s Markush-style structural variables (X, R1-R6), then narrowed by dependent claim conditions (fluorine, halogen placement, and named fluorinated prostaglandin embodiments) and by the anti-ulcer framing in claims 7-13.

What does US Patent 5,284,858 claim for substituted Prostaglandin E anti-ulcer treatment?

Answer: a structured Markush genus of Prostaglandin E analogs plus anti-ulcer composition and method-of-use claims.

Claim 1: Prostaglandins E genus (core chemical claim)

Claim 1 recites “Prostaglandins E” defined by a general formula with substituent variables:

X: a defined substructure (given in the patent as ##STR47##).
R1: hydrogen, a physiologically acceptable salt residue, or an ester residue selected from:
- alkyl
- benzyl
- hydroxyalkyl
- alkoxyalkyl
- alkylsilyl
- tetrahydropyranyl
R2: hydrogen or methyl
R3: hydroxyl or hydroxymethyl
R4 and R5: each independently hydrogen, methyl, or halogen, with the condition that at least one of R4 and R5 is a halogen
R6: a C1-C9 alkyl group that may be:
- branched or have a double bond, or
- substituted with an alkoxy group,
- with the C2–C3 bond being single or double

Practical claim construction impact

Claim 1 is broad at the “poly-substituted” level: it covers multiple positions and multiple classes of substituents.
The key limiting feature is the halogen condition at R4/R5 (at least one halogen).
It also covers ester derivatives via R1, which can expand coverage to prodrug-like forms.

Claims 2-4: Halogen/fluorine and methyl refinement (narrower chemical sub-genera)

Claim 2: R4 and R5 are both halogens
Claim 3: at least one of R4/R5 is fluorine
Claim 4: at least one of R4 or R5 is methyl

These provide fallback coverage inside claim 1’s genus. Note the drafting: claim 4 is not “R4 and R5 are methyl”; it is “R4 or R5 is a methyl group”, which is compatible with “at least one is a halogen” depending on which variable is halogen vs methyl.

Claim 5: Named embodiment: 13,14-dihydro-15-keto-PGE fluorinated at 16-position

Claim 5: 13,14-dihydro-15-keto-PGE with one or more fluorine atoms on 16-position or an alkyl ester of it.

This is a concrete sub-genus with a specific ring/functionalization pattern.

Claim 6: Named embodiment: 13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1 (+ esters)

Claim 6: 13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1 or alkyl ester.

This locks in stereochemistry at 16 (“R,S-fluoro”) and a particular diketo pattern at 6 and 15, then again includes alkyl esters.

Claim 7: Anti-ulcer composition claim with the same chemical genus

Claim 7 is an anti-ulcer composition comprising an anti-ulcer effective amount of a prostaglandin E expressed by a formula that mirrors claim 1’s variable definitions.

What changes from claim 1

Claim 7 converts the chemical genus into a formulation/composition setting, but it stays tethered to the same chemical structure variables.

Claims 8-12: composition narrowing to halogen/fluorine and named embodiments

Claim 8: R4 and R5 are halogens
Claim 9: R4 and/or R5 is fluorine
Claim 10: R4 or R5 is methyl
Claim 11: anti-ulcer composition where prostaglandin E is 13,14-dihydro-15-PGE with fluorine on 16-position or alkyl ester
Claim 12: anti-ulcer composition where prostaglandin E is 13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1 or alkyl ester

Claim 13: method-of-treatment of ulcer by administering the prostaglandin E

Claim 13 recites treatment of ulcer by administering an anti-ulcer effective amount of a prostaglandin E defined by the same structural variables.

Enforcement handle

Even if a competitor uses a non-identical formulation, the method claim can still be asserted if the administered active matches claim 13’s chemical structure.

How broad is claim 1’s Markush scope and where are the real structural “pressure points”?

Answer: broad genus coverage, with enforceability concentrated on (i) halogen placement at R4/R5, (ii) ester identity via R1, and (iii) whether a product includes the specific fluorinated 16-position sub-genus.

Pressure point 1: “at least one of R4 and R5 is a halogen”

Claim 1 requires halogen presence at either R4 or R5. That is a clear binary boundary for chemical infringement analysis.

If a candidate has no halogen at R4/R5, it falls outside claim 1 and its dependent composition and method claims tied to the same variables.

Pressure point 2: fluorine vs other halogens

Dependent claims 2 and 3 create narrower buckets:

R4/R5 both halogen (claim 2)
R4/R5 fluorine (claim 3)

From a litigation perspective, claim 3 is particularly important because fluorine is commonly used in medicinal chemistry to tune potency, metabolic stability, and receptor interactions. A candidate with fluorine at the relevant position can land directly in these fallbacks even if other variables differ.

Pressure point 3: ester coverage via R1

R1 includes numerous ester types, meaning competitors cannot avoid by switching from an acid to a variety of esters that still fit the R1 list.

The scope includes:

simple alkyl esters
benzyl esters
hydroxyalkyl and alkoxyalkyl esters
alkylsilyl esters
tetrahydropyranyl esters

This is a meaningful infringement lever because many commercial product strategies use ester prodrugs or formulation-compatible derivatives.

Pressure point 4: named fluorinated sub-genus embodiments (claims 5 and 6)

Claims 5 and 6 carve out specific actives:

13,14-dihydro-15-keto-PGE with fluorine at 16-position (claim 5)
13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1 and alkyl esters (claim 6)

Even without perfect mapping to the full genus variables in claim 1, proving that a product-active matches these defined named embodiments can be a cleaner path.

Which dependent claims create the strongest fallback positions against generics or “around” candidates?

Answer: claims 3, 5, and 6 are the highest-yield fallbacks because they narrow to fluorine at specified positions and to specific diketo/keto patterns tied to prostaglandin E analogs.

Claim 3 (fluorine at R4/R5)

If an “around” candidate keeps halogen but uses fluorine, claim 3 can be asserted even when R4/R5 halogen identity is disputed.

Claim 5 (13,14-dihydro-15-keto-PGE with 16-position fluorination)

This is a named sub-genus. If product-active is in that set, the scope narrows dramatically.

Claim 6 (13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1)

Stereochemical language can matter. A design that changes stereochemistry or removes the 6,15-diketo pattern may avoid this claim, but it could still fall within claim 1 unless it avoids halogens at R4/R5 or uses a non-encompassed ester or variable pattern.

How does the patent treat ester prodrugs and what does R1 cover?

Answer: it explicitly covers multiple ester classes for R1, creating infringement risk for prodrug variants using those ester types.

R1 is expressly defined as:

hydrogen
physiologically acceptable salt residue
an ester residue selected from six categories: alkyl, benzyl, hydroxyalkyl, alkoxyalkyl, alkylsilyl, tetrahydropyranyl.

That list is broader than “alkyl ester” alone. A competitor attempting to avoid claim coverage by converting the active into a protected or masked form must show that the ester is outside these categories or that other structural conditions (R2-R6) no longer match.

What is the effective infringement theory: composition vs method vs chemical claim?

Answer: three independent infringement routes: active-ingredient infringement (claim 1), product infringement (claim 7), and administration infringement (claim 13).

Route A: product contains the active molecule

If a competitor sells a drug containing a prostaglandin E that meets claim 1’s structural variables, claim 1 is directly implicated.

Route B: product is sold as an anti-ulcer composition

If the product is marketed for anti-ulcer use and contains an “anti-ulcer effective amount” of the claimed prostaglandin E, claim 7 provides additional coverage.

Route C: physician/label-driven administration

If the product is used for ulcer treatment and the administered amount corresponds to “anti-ulcer effective amount” of the claimed prostaglandin E, claim 13 is a method-of-use hook.

In practice, route C depends on evidence aligning the accused use with the claim’s ulcer-treatment framing and the specific active compound identity.

What patent landscape surrounds US 5,284,858 (and how do you map risk to commercial assets)?

Answer: a full US landscape requires Orange Book, continuation family members, related foreign filings, and any litigation record; those source-specific datasets are not present in the provided material, so no defensible landscape can be produced here.

No dataset was provided for:

the patent’s family members (continuations/divisionals)
whether US 5,284,858 is listed in the Orange Book for any approved product
any FDA approved ulcer indication and active ingredient mapping
any Paragraph IV filings tied to the patent
any district court cases or ITC matters involving 5,284,858

Because the prompt contains only the claim text and no supporting bibliographic or prosecution/litigation facts, a complete and accurate US/Orange Book/Paragraph IV landscape cannot be generated.

Key claim-by-claim scope matrix (what an accused product would have to match)

Claim	What must be present	Main limitation(s)	Avoidance paths (structural, not legal)
1	Prostaglandin E meeting formula variables X, R1-R6	At least one halogen at R4/R5; R1 must be within listed salt/ester types	Remove halogen from R4 and R5; use R1 ester outside list; shift other R2/R3/R6 features out of range
2	Claim 1 + R4 and R5 halogens	R4 and R5 both halogen	Make only one of R4/R5 halogen or eliminate halogen at one position
3	Claim 1 + fluorine at R4 or R5	Requires fluorine in the defined position space	Replace fluorine with other substituent(s) while keeping claim 1 constraints consistent
4	Claim 1 + R4 or R5 is methyl	Methyl presence in R4/R5 while still requiring at least one halogen	Use hydrogen at both R4/R5 where halogen requirement cannot be satisfied; or replace methyl with non-methyl substituent while keeping halogen logic
5	Specific named sub-genus: 13,14-dihydro-15-keto-PGE with 16-position fluorination or alkyl ester	Defined keto/fluoro pattern at 16	Remove 16-fluoro or change keto pattern; use ester not matching “alkyl ester” definition as read in the patent
6	Specific named sub-genus: 13,14-dihydro-6,15-diketo-16R,S-fluoro-PGE1 or alkyl ester	Stereochemical and diketo constraints	Alter stereochemistry and/or remove 6,15-diketo pattern
7	Composition: anti-ulcer effective amount of compound meeting claim 1	Both chemical match and anti-ulcer composition context	Use an active outside claim 1; change to non-anti-ulcer effective formulation with different active
8-10	Claim 7 + halogen/fluoro/methyl refinements	Uses claim 1 narrowing inside composition setting	Vary R4/R5 substituents to exit each dependent condition
11	Composition with claim-5 sub-genus	Named fluoro/keto pattern	Alter 16-fluoro or keto motif; avoid alkyl ester coverage
12	Composition with claim-6 sub-genus	Named fluorinated diketo stereochemistry	Alter stereochemistry and/or diketo motif
13	Method: ulcer treatment by administering anti-ulcer effective amount of claim-1 prostaglandin	Chemical match + ulcer-treatment use	Use non-matching active; avoid use/label targeting ulcer treatment with the claimed active

What is the commercial risk profile implied by this claim set?

Answer: high risk for competitors developing fluorinated ester variants of 13,14-dihydro prostaglandin E analogs aimed at ulcer indications.

Commercially, the breadth of:

halogen-enabled R4/R5 substitution,
explicit ester class inclusion for R1,
and named fluorinated 16-position sub-genus coverage

creates a “design-around” challenge that tends to push developers toward:

removing the R4/R5 halogen requirement,
using a non-covered ester type,
or changing the core prostaglandin pattern enough to avoid claims 5 and 6.

Key Takeaways

US 5,284,858 claims a substituted prostaglandin E chemical genus using Markush variables (X, R1-R6) with a hard limitation that at least one of R4 and R5 is a halogen.
Dependent claims isolate fluorine (claim 3) and cover named fluorinated prostaglandin E embodiments centered on 16-position fluorination and specific keto/diketo patterns (claims 5 and 6).
The patent includes three infringement vectors: chemical (claim 1), composition for anti-ulcer use (claim 7), and method-of-treatment for ulcer by administration (claim 13).
Ester variation is not a clean workaround because R1 expressly covers multiple ester classes (including alkyl, benzyl, hydroxyalkyl, alkoxyalkyl, alkylsilyl, tetrahydropyranyl).
A full “US patent landscape” (Orange Book status, continuation family, Paragraph IV, litigation, settlement) cannot be produced from the provided input because no bibliographic, FDA, or case-history records were included.

FAQs

Does US 5,284,858 cover only fluorinated prostaglandin E analogs?
No. Claim 1 covers halogen at R4/R5 (at least one halogen), and fluorine is captured via narrower dependent claims and named embodiments.
Are ester prodrugs covered under US 5,284,858?
Yes. Claim 1’s R1 expressly includes multiple ester residue classes; claims 5 and 6 also include alkyl ester variants of the named fluorinated prostaglandins.
What is the most direct avoidance strategy based on structure?
Removing halogen from both R4 and R5 positions (breaking the “at least one halogen” condition) is a principal structural boundary, assuming other variables remain within the claim framework.
Can liability attach even if a product is administered for ulcer treatment rather than sold as an anti-ulcer composition?
Claim 13 creates method-of-use exposure tied to ulcer treatment by administering an anti-ulcer effective amount of the claimed prostaglandin.
Do claims 5 and 6 provide cleaner infringement hooks than claim 1?
Yes. They recite specific named sub-genuses with defined functional patterns and fluorination at 16-position, which narrows mapping for accused actives.

References

No sources were provided beyond the claim text included in the prompt, so no external citations can be listed.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	62-18820	Jan 28, 1987
Japan	62-65352	Mar 18, 1987

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	79610	⤷ Start Trial
Canada	1323364	⤷ Start Trial
Germany	3873797	⤷ Start Trial
European Patent Office	0284180	⤷ Start Trial
Spain	2043798	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,284,858

Summary for Patent: 5,284,858