Details for Patent: 5,532,241

US Patent 5,532,241: Scope, Claims, Expiration, and Patent Landscape for Vilazodone

US Patent 5,532,241 is the foundational composition-of-matter patent covering vilazodone and related indole-piperazine compounds. Its claims cover a Markush genus of substituted indol-3-yl alkyl piperazines linked to benzofuran, chromanone, or chromene derivatives. Claim 2 expressly identifies the compound marketed as vilazodone, also known as EMD 68843.

The patent was filed in the United States in 1994 and issued on July 2, 1996. Its ordinary 20-year patent term expired in 2014, subject to any applicable patent-term adjustment or terminal-disclaimer calculation. It is therefore no longer an enforceable blocking patent for US commercial manufacture or sale. Its main present value is historical: it established the original composition-of-matter position later supplemented by formulation, crystalline-form, manufacturing, and method-of-use patents.

What drug does US Patent 5,532,241 protect?

US 5,532,241 protects vilazodone and a broader family of serotonin-active indole derivatives.

Vilazodone is:

• An indole derivative
• A serotonin 5-HT1A receptor partial agonist
• A serotonin transporter inhibitor
• Commercialized in the United States as Viibryd
• Approved by the FDA for major depressive disorder in adults

The compound identified in claim 2(c) is vilazodone:

1-[4-(5-cyanoindol-3-yl)butyl]-4-(2-carbamoylbenzofuran-5-yl)piperazine.

The claim 2(c) structure can be summarized as follows:

The patent does not claim only the commercial product. Claim 1 reaches a substantially broader genus of compounds with permitted substitutions on both the indole and benzofuran-related portions.

What is the scope of claim 1?

Claim 1 is the principal Markush composition claim. It covers compounds having the patented core architecture, subject to defined substitutions.

The key limitations are:

The commercial vilazodone structure falls within the genus because it has:

• A 5-cyanoindol-3-yl group
• A four-carbon linker
• A piperazine nitrogen
• A benzofuran-5-yl group
• A benzofuran carboxamide substituent

The claim is chemically broad but structurally constrained. It does not cover every indole-piperazine compound. A potentially infringing compound would need to satisfy the required ring identities, substitution classes, linker length, and nitrogen-containing scaffold.

How do claims 2 through 15 narrow the patent?

Claims 2 through 15 provide narrower species and subgenus claims. Their importance differs considerably.

Claim 2: named chemical species

Claim 2 recites three specific compounds:

• A 5-methoxyindole/hydroxymethylbenzofuran compound
• A 5-cyanoindole/ethoxycarbonylbenzofuran compound
• Vilazodone, the 5-cyanoindole/benzofuran carboxamide compound

Claim 2(c) is the most commercially significant species claim because it identifies the active ingredient in Viibryd.

Claims 3 through 5: indole substitution patterns

These claims narrow the indole group by limiting the number and position of substituents:

• Claim 3 permits up to two indole substituents.
• Claim 4 focuses on 5-substituted indoles.
• Claim 5 focuses on 4-, 6-, or 7-substituted indoles.

These claims create fallback positions if the broader genus in claim 1 were challenged for lack of written description, enablement, or priority support.

Claim 6: alkyl substitution

Claim 6 limits A to methyl or ethyl. This narrows alkoxy, alkylamino, and related groups that otherwise may extend to six carbon atoms under claim 1.

Claim 7: R1 substituent limitations

Claim 7 limits R1 to:

• Benzofuran-5-yl; or
• Chroman-4-on-6-yl

It also specifies hydroxymethyl, carboxamide, alkoxycarbonyl, or substituted amide groups. This claim is closer to the chemical space containing vilazodone than the full genus in claim 1.

Claim 8: four-carbon linker

Claim 8 limits Q to -(CH2)4-. This is a particularly important narrowing limitation because vilazodone uses a four-carbon butyl linker.

Claims 9 and 10: 5-substituted indole species

These claims focus on 5-substituted indoles:

• Claim 9: 5-hydroxy or 5-alkoxy
• Claim 10: 5-carboxamide or 5-cyano

Claim 10 is the relevant subgenus for vilazodone because the drug contains a 5-cyanoindole.

Claims 11 through 15: aromatic substituent classes

These claims separately cover benzofuran, chromanone, and chromene variants, including unsubstituted structures and structures bearing cyano, hydroxymethyl, alkoxymethyl, or carbonyl-derived substituents.

What is the strongest claim against vilazodone?

Claim 2(c) is the most direct claim against vilazodone because it names the exact compound. Claim 10 also captures an important structural subset through the 5-cyanoindole limitation, while claims 1 and 8 provide broader and intermediate fallback positions.

The claim hierarchy is:

Claim 2(c) would generally be the most straightforward infringement theory if the accused product contains vilazodone itself. Claims 16 and 17 could apply to dosage forms containing the claimed compound, although the scope of claim 17 depends on how the 0.2-500 mg limitation is construed.

What formulations are protected by US 5,532,241?

Claim 16 covers a pharmaceutical composition comprising a claimed compound and a pharmaceutically acceptable carrier. Claim 17 narrows that composition to one containing 0.2-500 mg of the compound.

These claims are composition claims, not detailed formulation-platform claims. They do not expressly require:

• A particular tablet coating
• A specific excipient
• A defined dissolution profile
• A particular particle size
• A crystalline polymorph
• A solid dispersion
• A controlled-release system
• A specific food-effect mitigation technology

The formulation claims therefore provide broad coverage of pharmaceutical compositions containing a covered compound, but they may face prior-art and obviousness issues more readily than a narrowly defined formulation claim.

For vilazodone, later commercial protection focused more heavily on formulation, dosage, crystalline form, and use claims than on the expired original composition patent. The FDA-approved product is an oral tablet. The product label states that Viibryd should be taken with food, reflecting the drug's food-dependent absorption characteristics (U.S. Food and Drug Administration, 2023).

When did US Patent 5,532,241 lose exclusivity?

The patent's ordinary term was approximately 20 years from its US nonprovisional filing date. Public patent records identify a 1994 US filing and a July 2, 1996 issue date. On that basis, the ordinary expiration date fell in 2014.

Patent-term adjustment can alter the precise expiration date. The original patent is nevertheless outside its ordinary enforceable term and cannot currently provide a live US composition-of-matter exclusionary right.

The patent's expiration did not eliminate later patent protection for vilazodone. It allowed generic manufacturers to challenge or await expiration of later-listed patents.

What is the Orange Book status of vilazodone?

The FDA Orange Book is the relevant US source for listed patents tied to approved drug products. The original US 5,532,241 patent is not the principal current barrier to generic vilazodone because it expired before the modern generic-entry disputes involving Viibryd.

Later Viibryd-related patents have included patents directed to subjects such as:

• Vilazodone treatment methods
• Pharmaceutical compositions
• Dosage regimens
• Drug administration with food
• Solid-state or formulation characteristics
• Manufacturing or process features

Orange Book listing status can change through patent expiration, delisting, corrections, and FDA updates. A current freedom-to-launch opinion should therefore rely on the latest FDA Orange Book patent table and the relevant patent registers rather than on US 5,532,241 alone (U.S. Food and Drug Administration, 2024).

Which companies challenged vilazodone patents?

Generic manufacturers seeking approval for vilazodone hydrochloride tablets have used abbreviated new drug applications and Paragraph IV certifications against listed Viibryd patents.

Publicly reported generic participants have included manufacturers and applicants such as:

• Teva Pharmaceuticals
• Mylan, later part of Viatris
• Torrent Pharmaceuticals
• Other ANDA applicants identified in FDA records and federal litigation

A Paragraph IV certification asserts that a listed patent is invalid, unenforceable, or not infringed. Filing a Paragraph IV certification can trigger patent litigation under the Hatch-Waxman Act and may create a 30-month stay of FDA approval, subject to statutory conditions (Drug Price Competition and Patent Term Restoration Act of 1984).

The expired 5,532,241 patent would not ordinarily support a current Paragraph IV dispute. The commercial dispute would instead focus on later patents that remained listed when each ANDA was filed.

What patent litigation affects vilazodone?

Vilazodone litigation has centered on later Orange Book patents rather than the original 1996 composition patent. The principal legal issues in this type of litigation are:

• Whether the asserted patent claims cover the generic's active ingredient or dosage form
• Whether the claims are invalid for obviousness
• Whether the claims are anticipated
• Whether the listed patent is properly tied to the approved product
• Whether a proposed generic label induces infringement of a method-of-use claim
• Whether a settlement permits an agreed entry date

The relevant litigation record must be assessed patent by patent. A settlement involving a later Viibryd patent would not revive or extend US 5,532,241.

Are there biosimilar risks for vilazodone?

No. Vilazodone is a small-molecule drug, not a biologic. The relevant competitive pathway is an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act, not a biosimilar application under the Biologics Price Competition and Innovation Act.

Competitive risk comes from:

• Generic vilazodone hydrochloride tablets
• Authorized-generic strategies
• Product-switching and formulary competition
• Later-entry generic manufacturers
• Potential differences in food-use instructions, strengths, and labeling

How strong is the patent estate for vilazodone?

The original patent was strong historically because claim 2(c) directly covered the commercial active ingredient. Its current strength is zero as an exclusionary right because the patent term has ended.

The broader estate can be divided into four periods:

The original patent's broad Markush claims would have created meaningful design-around difficulty during their term. A competitor could not avoid the exact species claim merely by changing the salt if the revised salt remained a physiologically acceptable salt covered by the claim.

What are the principal design-around and invalidity issues?

The main design-around routes during the patent term would have included:

• Changing the linker length outside the claimed range
• Replacing piperazine with a different basic heterocycle
• Moving the indole substituent
• Replacing the benzofuran ring with a nonclaimed heteroaromatic system
• Using a substituent outside the listed R2 classes
• Developing a distinct chemical entity rather than a vilazodone salt

Potential validity issues would have included:

• Prior-art indole-piperazine compounds
• Obviousness of combining known indole and benzofuran pharmacophores
• Written-description support for the breadth of the Markush genus
• Enablement across the full range of substitutions
• Construction of the formula and substituent definitions
• Priority support for the claimed species and genus

Because claim 2(c) recites a specific compound, it would generally have been more resilient to written-description and enablement attacks than claim 1, assuming the compound was adequately disclosed and supported in the specification.

What is the geographic coverage?

US 5,532,241 provided rights only in the United States. Corresponding foreign applications and patents may have existed in Europe and other jurisdictions, but those rights required separate evaluation for:

• National-phase status
• Local filing and priority rules
• Patent-term calculations
• Supplementary protection certificates
• Opposition or revocation proceedings
• Local claim construction
• Post-grant validity decisions

Expiration of the US patent did not determine the status of foreign counterparts.

What is the commercial impact of the expired patent?

US 5,532,241 no longer directly protects Viibryd revenue. Its commercial significance is indirect:

• It established the original proprietary position for vilazodone.
• It supported the commercial launch of Viibryd.
• It explains why later patents were important for extending the product's market protection.
• It remains relevant to historical patent valuation and prosecution analysis.
• It does not independently block current generic vilazodone entry.

Revenue exposure should therefore be linked to surviving Orange Book patents, generic approval timing, payer substitution, and post-expiration erosion rather than to US 5,532,241.

Key Takeaways

• US 5,532,241 is the foundational vilazodone composition-of-matter patent.
• Claim 2(c) directly identifies vilazodone.
• Claim 1 covers a broad Markush genus of indole-piperazine compounds.
• Claims 8 and 10 provide important structural subgenus coverage for the commercial drug.
• Claims 16 and 17 cover pharmaceutical compositions containing the claimed compounds.
• The patent's ordinary US term expired in 2014.
• It is no longer a current US barrier to generic vilazodone.
• Current generic-launch risk depends on later Orange Book patents, litigation outcomes, and settlement entry dates.
• Vilazodone is a small molecule, so biosimilar law does not apply.
• The patent's historical strength was high; its present exclusionary value is exhausted.

FAQs

Does US 5,532,241 cover vilazodone hydrochloride?

Yes. Claim 2(c) identifies the vilazodone free-base structure, and claim 1 extends to physiologically acceptable salts. Vilazodone hydrochloride would generally fall within the salt language if it satisfies the claim's chemical and salt limitations.

Can a generic manufacturer avoid US 5,532,241 by using a different vilazodone salt?

That question was relevant during the patent term. The claim expressly includes physiologically acceptable salts, so changing the counterion would not necessarily avoid infringement. Today, the issue is largely historical because the patent has expired.

Does the patent cover vilazodone methods of treatment?

Not based on the claims provided. The claims are directed to compounds and pharmaceutical compositions. They do not expressly recite a method of treating depression or administering vilazodone to a patient.

Does claim 17 require a 0.2-500 mg tablet strength?

The claim recites a composition in which the compound is present in an amount of 0.2-500 mg. Whether that limitation requires a unit dosage form, a tablet-specific amount, or another composition-level interpretation would depend on the specification and prosecution history.

Is US 5,532,241 relevant to current ANDA litigation?

Usually not as an enforceable patent. Current ANDA litigation would generally address later unexpired patents listed for Viibryd, including formulation, dosage, method-of-use, or other secondary patents. The original patent may still appear in historical patent-chain analysis but does not ordinarily support a present injunction.

References

1. U.S. Patent No. 5,532,241. (1996). Indole derivatives. United States Patent and Trademark Office.

2. U.S. Food and Drug Administration. (2023). Viibryd (vilazodone hydrochloride) prescribing information. FDA.

3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

4. Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.

5. United States Patent and Trademark Office. (2024). Patent term adjustment and patent term extension resources. USPTO.