United States Drug Patent 5,135,950: Entacapone Polymorph A Claims, Scope and Patent Landscape

US Patent No. 5,135,950 protected crystallographically pure polymorphic Form A of entacapone, a catechol-O-methyltransferase inhibitor developed for use with levodopa in Parkinson's disease. The patent also covered two crystallization processes, pharmaceutical compositions, COMT-inhibition methods, and levodopa combination treatment.

The patent was granted to Orion-Yhtymä Oy on August 4, 1992. Its pre-Uruguay Round patent term expired on August 4, 2009. The patent is no longer an enforceable barrier to generic entacapone or to processes that would otherwise have fallen within its claims.[1]

What drug does US Patent 5,135,950 protect?

The patent protects Form A of entacapone. The chemical name recited in the claims is:

(E)-N,N-diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide.

The compound is commonly known as entacapone and has the molecular formula C14H15N3O5. Entacapone inhibits peripheral catechol-O-methyltransferase, increasing levodopa availability for conversion to dopamine in the central nervous system.

The patent does not claim the basic entacapone molecule in broad chemical terms. Its central product claim is limited to a particular crystalline polymorph identified by crystallographic purity and a specified infrared spectrum.

Patent identification and term

Item	Data
US patent	5,135,950
Title	Crystalline form of entacapone
Applicant/assignee	Orion-Yhtymä Oy
Filing date	December 19, 1990
Priority date	December 20, 1989
Grant date	August 4, 1992
Patent term	17 years from grant under pre-URAA rules
Expiration date	August 4, 2009
Active ingredient	Entacapone
Covered product	Crystallographically essentially pure polymorphic Form A
Therapeutic use	COMT inhibition and Parkinson's disease treatment with levodopa

The patent's term was not governed by the modern 20-year-from-earliest-effective-filing-date rule because the application was filed before the transition to the Uruguay Round Agreements Act patent-term regime.[1,2]

What does claim 1 of US 5,135,950 cover?

Claim 1 is the patent's principal product claim. It covers:

Entacapone;
In polymorphic Form A;
In crystallographically essentially pure form; and
Having the specified potassium-bromide infrared absorption bands.

The infrared bands include peaks at 3339, 3092, 3066, 3039, 2981, 2938, 2217, 1628, 1607, 1580, 1544, 1512, 1441, 1377, 1298, 1281, 1210, 1165, 1150, 800, 779 and 740 cm-1.[1]

Product-by-process implications

Claim 1 is not a product-by-process claim. It identifies the product by its crystalline form and analytical characteristics. A manufacturer could infringe the claim by making, using, importing, selling or offering to sell Form A entacapone, regardless of whether the manufacturer used the patented crystallization process.

The practical scope depends on how a court construes two expressions:

"Crystallographically essentially pure"
The listed infrared absorption bands

The claim does not state a numerical purity threshold. That omission creates a potential claim-construction issue. In enforcement, the patent owner would need to establish that the accused material is Form A and falls within the meaning of "essentially pure" as understood by a skilled person using the patent specification and relevant analytical practice.

The infrared limitation is important because it gives the claim an objective identification method. A materially different polymorph, amorphous entacapone, or a mixture dominated by another solid form would present a stronger noninfringement position. A product with the same Form A crystal structure but minor process-related impurities would present a more difficult issue.

How do claims 2 through 4 protect entacapone manufacturing?

Claims 2 through 4 cover processes for producing Form A entacapone.

Claim 2 requires crystallization of crude entacapone from a lower aliphatic carboxylic acid containing a catalytic amount of hydrochloric acid or hydrobromic acid.

Claim 3 narrows claim 2 to acetic acid.

Claim 4 narrows claim 2 to formic acid.

Process claim limitations

Claim	Required process
2	Crystallize crude entacapone from a lower aliphatic carboxylic acid with catalytic HCl or HBr
3	Claim 2 process using acetic acid
4	Claim 2 process using formic acid

The process claims do not cover every method of producing Form A. A process using a different solvent, a different acid, no catalytic hydrogen halide, or a different isolation technique could fall outside the literal language of claims 2 through 4.

A manufacturer could still face product-claim exposure under claim 1 even if it avoids claims 2 through 4. The product claim and process claims therefore operate independently:

Avoiding the claimed process does not avoid claim 1 if the resulting product is Form A.
Producing a different polymorph may avoid claim 1 but does not by itself establish noninfringement if the process uses all limitations of claim 2.
Claims 3 and 4 have narrower solvent limitations and are easier to design around than claim 2.

The phrase "lower aliphatic carboxylic acid" would ordinarily encompass short-chain carboxylic acids, with acetic and formic acid expressly identified in dependent claims. The patent specification and prosecution history would be relevant to determining the full scope of that phrase.

What do claims 5 through 10 cover?

Claims 5 through 10 extend the polymorph claim into pharmaceutical and therapeutic use.

Claim	Subject matter
5	Pharmaceutical composition containing Form A entacapone and a pharmaceutically acceptable carrier
6	Method of inhibiting COMT by administering Form A entacapone
7	Treating Parkinson's disease with Form A entacapone and levodopa
8	Claim 7 treatment also using a peripheral decarboxylase inhibitor
9	Claim 8 where the inhibitor is carbidopa
10	Claim 8 where the inhibitor is benserazide

Claims 7 through 10 are combination-treatment claims. They require administration of entacapone with levodopa. Claims 9 and 10 further specify the peripheral decarboxylase inhibitor.

Method-of-use scope

Claim 6 is broad within its stated therapeutic objective. It requires administration of Form A entacapone in a COMT-inhibiting amount to a patient requiring treatment.

Claim 7 is narrower because it requires:

Form A entacapone;
Levodopa;
Treatment of Parkinson's disease; and
A sufficient amount of each agent for the stated treatment.

Claim 9 is narrower than claim 8 because it specifically requires carbidopa. Claim 10 substitutes benserazide.

These claims would have been relevant to combination products such as entacapone/levodopa/carbidopa. They would not necessarily cover:

Entacapone in a different polymorphic form;
Entacapone administered for a non-Parkinson's indication;
Levodopa treatment without Form A entacapone;
A formulation containing entacapone but not used for the claimed method;
A treatment using a different COMT inhibitor.

After patent expiration, these method claims no longer create a US patent infringement risk.

What formulations are protected by US Patent 5,135,950?

Claim 5 protects a pharmaceutical composition containing Form A entacapone and a pharmaceutically acceptable carrier. It does not require a particular tablet, capsule, excipient, dose, release profile or manufacturing method.

The claim therefore has broad dosage-form coverage but narrow active-form coverage. It can reach:

Immediate-release tablets;
Capsules;
Other oral solid dosage forms;
Compositions containing conventional pharmaceutical excipients.

It does not expressly claim:

A particular excipient system;
A dissolution specification;
A fixed-dose ratio;
A bilayer tablet;
A sustained-release formulation;
A specific tablet coating;
A manufacturing parameter.

A formulation containing Form A would have been exposed to claim 5 even if it used excipients or a dosage form not described in the claim. A formulation using a different crystalline form could avoid claim 5, subject to proof that the material was not Form A.

What was the Orange Book status of entacapone?

Entacapone was approved by the FDA as Comtan tablets under NDA 020796. Entacapone was also approved in combination with levodopa and carbidopa as Stalevo under NDA 021485.[3,4]

US Patent 5,135,950 was associated with the original entacapone product and was relevant to the product's US exclusivity history. Its expiration in 2009 removed the principal polymorph patent barrier to generic entacapone products.

FDA approval of a generic does not itself determine patent infringement. An ANDA applicant can certify under Paragraph IV that listed patents are invalid, unenforceable or not infringed. Under the Hatch-Waxman framework, the NDA holder may file an infringement action within 45 days, triggering a statutory stay of approval for up to 30 months, subject to statutory exceptions.[5]

Because US 5,135,950 expired in 2009, a later generic applicant would not need to maintain a Paragraph IV challenge against that patent as an ongoing commercial barrier. The patent's expiration date, rather than a settlement date, controlled the end of its exclusionary effect.

When did entacapone lose exclusivity?

Entacapone lost the enforceable exclusivity provided by US 5,135,950 on August 4, 2009.

The commercial exclusivity timeline was:

Event	Date
US patent priority	December 20, 1989
US patent filing	December 19, 1990
US patent grant	August 4, 1992
FDA approval of Comtan	1999
FDA approval of Stalevo	2003
US 5,135,950 expiration	August 4, 2009
Generic-entry opportunity	After applicable remaining regulatory and patent barriers expired

FDA regulatory exclusivity and patent exclusivity are separate. The patent's expiration did not automatically eliminate any unexpired regulatory exclusivity attached to a later-approved product, although the principal statutory patent barrier for Form A entacapone had ended.

Which companies challenged the entacapone patent estate?

The relevant competitive field included Orion, Novartis and generic manufacturers seeking approval for entacapone products. Public FDA materials identify generic entacapone products and generic versions of entacapone combination products after the original patent period.[3,4]

A definitive list of Paragraph IV filers and litigation outcomes requires review of ANDA certification records, FDA patent-listing data and PACER case dockets. The patent itself does not identify later challengers, settlements or ANDA filers. US 5,135,950 is expired and therefore does not present a current litigation obstacle.

What patent litigation affected US 5,135,950?

The patent record establishes the grant and term but does not, by itself, establish the complete litigation history. The principal legal issue for a historical challenge would have been whether an accused entacapone product was Form A and "crystallographically essentially pure," rather than whether the product was entacapone generally.

Potential historical defenses included:

The accused material was not Form A;
The material was a polymorphic mixture;
The IR spectrum did not satisfy the claim;
"Essentially pure" lacked a sufficiently definite boundary;
The patent was invalid for anticipation or obviousness;
The specification did not adequately describe or enable the full claimed scope;
The asserted claim was not infringed because the product or process lacked a required limitation.

The process claims would have required proof of the actual manufacturing route. Discovery into batch records, solvent systems, acid catalysts and crystallization conditions would have been central to any process infringement case.

No current enforcement action can arise from the expired patent.

How strong was the patent estate for entacapone?

US 5,135,950 was commercially meaningful but technically narrow.

Strengths

It claimed a specific solid form used in the commercial product.
The IR limitations provided an objective analytical fingerprint.
Claim 1 could cover the product regardless of manufacturing route.
Claim 5 extended coverage to pharmaceutical compositions.
Claims 7 through 10 addressed the intended Parkinson's treatment combinations.
The process claims captured disclosed industrial crystallization routes.

Weaknesses

The patent did not broadly claim all entacapone.
The principal product claim depended on proving Form A.
"Crystallographically essentially pure" was not quantified in the claim.
The process claims could be designed around by changing solvent or catalyst.
The therapeutic claims were tied to the claimed crystal form.
The patent term ended before the major modern generic-entry period for many lifecycle products.

Its strongest historical position was against a commercial product containing Form A entacapone. Its weakest position was against a non-Form-A polymorph, amorphous material, or a process using materially different crystallization conditions.

How does US 5,135,950 compare with later entacapone patents?

US 5,135,950 is best understood as a solid-state and use patent, not the foundational composition-of-matter patent for entacapone.

Patent category	Typical scope	Relationship to US 5,135,950
Basic entacapone compound patent	Chemical compound and broad derivatives	Broader chemical protection, generally earlier
Polymorph patent	Specific crystal form and analytical profile	US 5,135,950's core category
Process patent	Synthesis, purification and crystallization	Claims 2 through 4
Formulation patent	Tablet, excipients, release or combination dosage form	Claim 5 is broad but not formulation-specific
Method-of-use patent	COMT inhibition or Parkinson's treatment	Claims 6 through 10
Combination patent	Entacapone with levodopa/carbidopa or benserazide	Claims 7 through 10

Later patents could have extended commercial protection for formulations, combination products or manufacturing improvements. Those patents would require separate claim and family analysis and cannot be treated as extensions of US 5,135,950.

What generic launch risks existed?

Before August 4, 2009, a generic entacapone applicant faced four principal risks:

Product infringement if the generic contained Form A.
Process infringement if the manufacturing route used the claimed acid-catalyzed crystallization process.
Composition infringement if the final dosage form contained Form A.
Combination-method exposure if the product labeling induced use with levodopa and carbidopa in a manner covered by the method claims.

After expiration, the first three risks disappeared for US 5,135,950. A generic applicant would still need to evaluate other unexpired patents, FDA listing requirements, product quality, bioequivalence and any separate patents covering Stalevo or specific formulations.

A design-around strategy before expiration could have focused on producing a different polymorph or using a different crystallization system. That strategy would have required rigorous solid-state characterization because inadvertent conversion to Form A could defeat the design-around.

Did licensing deals affect the patent rights?

Orion developed entacapone and commercialized it through arrangements involving Novartis for products including Comtan and Stalevo. The patent document does not disclose the commercial terms of licensing or co-promotion agreements.

A license would have affected who could practice the patent, not the patent's expiration date or claim scope. After expiration, the license could remain commercially relevant for trademarks, know-how, supply, regulatory cooperation or other intellectual-property rights, but it could not revive the expired patent monopoly.

What is the current commercial significance of US 5,135,950?

The patent has no current enforceable exclusionary value in the United States. Its commercial importance is historical:

It helped protect the solid form selected for commercial entacapone.
It supported the original Comtan product franchise.
It provided product, process and method-of-use coverage through 2009.
It influenced generic development strategies involving polymorph selection and analytical testing.

Revenue exposure was concentrated in Comtan and Stalevo sales during the period when the patent and related rights remained active. The patent alone cannot be used to calculate product revenue because sales were also affected by regulatory exclusivity, other patents, competition, prescribing patterns and the separate protection of combination products.

Key Takeaways

US 5,135,950 covered crystallographically essentially pure Form A entacapone.
Claim 1 was the key product claim and required the specified IR spectrum.
Claims 2 through 4 covered acid-catalyzed crystallization processes using lower aliphatic carboxylic acids.
Claims 5 through 10 covered compositions, COMT inhibition and Parkinson's treatment with levodopa, with carbidopa or benserazide in narrower claims.
The patent expired on August 4, 2009.
It did not broadly claim every form of entacapone.
Before expiration, the primary design-around options were a different polymorph or a materially different manufacturing process.
The patent is no longer a US barrier to generic entacapone entry.
Separate patents and regulatory requirements for Stalevo, formulations and later manufacturing improvements must be analyzed independently.

FAQs

What is the active ingredient in US Patent 5,135,950?

The active ingredient is entacapone, chemically identified as (E)-N,N-diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide.

Does US 5,135,950 cover amorphous entacapone?

No. The claims are directed to crystallographically essentially pure polymorphic Form A. Amorphous entacapone is outside the literal product claim unless it contains or converts into the claimed crystalline form.

Could a generic use a different entacapone polymorph before the patent expired?

Potentially, yes. A different polymorph could avoid claim 1 if it did not satisfy the Form A structural and IR limitations. The manufacturer would also need to avoid the specific process limitations in claims 2 through 4.

Does the patent cover entacapone with levodopa alone?

Claim 7 requires entacapone and levodopa for Parkinson's disease treatment. Claims 8 through 10 add a peripheral decarboxylase inhibitor, with claims 9 and 10 specifying carbidopa or benserazide.

Is US 5,135,950 still listed as an enforceable patent?

No. The patent expired on August 4, 2009 and cannot presently be asserted to block US manufacture, sale or use of Form A entacapone.

References

Orion-Yhtymä Oy. (1992). Crystalline form of entacapone, U.S. Patent No. 5,135,950. United States Patent and Trademark Office.
United States Patent and Trademark Office. (2023). Patent term adjustment and patent term calculation guidance. U.S. Department of Commerce.
U.S. Food and Drug Administration. (1999). Comtan (entacapone) tablets prescribing information. FDA.
U.S. Food and Drug Administration. (2003). Stalevo (carbidopa, levodopa and entacapone) tablets prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	8924838.9	Nov 03, 1989

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0426468	⤷ Start Trial	91071	Luxembourg	⤷ Start Trial
European Patent Office	0426468	⤷ Start Trial	CA 2004 00007	Denmark	⤷ Start Trial
European Patent Office	0426468	⤷ Start Trial	C00426468/01	Switzerland	⤷ Start Trial
European Patent Office	0426468	⤷ Start Trial	0490007-2	Sweden	⤷ Start Trial
Austria	127447	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,135,950

Summary for Patent: 5,135,950