US Patent 5,565,467: Dutasteride Claims, Scope, Expiration, and Patent Landscape

US Patent 5,565,467 covers dutasteride as a chemical compound, pharmaceutical formulations containing dutasteride, and selected combination formulations. The patent’s principal commercial subject is dutasteride, the active ingredient in Avodart and one component of Jalyn. The patent expired on October 15, 2013, based on its 17-year term from grant. It no longer creates an enforceable barrier to generic dutasteride, subject to separate patents, regulatory exclusivities, and other rights that may have applied to particular products or uses.[1]

What drug does US Patent 5,565,467 protect?

The compound in claim 1 is dutasteride, also known as:

Dutasteride
17β-N-(2,5-bis(trifluoromethyl)phenylcarbamoyl)-4-aza-5α-androst-1-en-3-one
A dual 5-alpha-reductase inhibitor
The active ingredient in Avodart

Dutasteride inhibits both type 1 and type 2 5-alpha-reductase enzymes, reducing conversion of testosterone to dihydrotestosterone. The FDA approved Avodart for the treatment of benign prostatic hyperplasia, or BPH, in a 0.5 mg oral capsule.[2]

What is the protected chemical structure?

Claim 1 covers the specific dutasteride molecule and pharmaceutically acceptable solvates. It is a single-compound claim rather than a Markush claim covering a broad genus of steroidal 5-alpha-reductase inhibitors.

The chemical claim therefore reaches:

Dutasteride itself
Dutasteride in a pharmaceutically acceptable solvate form
Dutasteride supplied as an active pharmaceutical ingredient
Dutasteride used in a pharmaceutical product, subject to the patent’s other claim limitations

The claim does not expressly cover every 5-alpha-reductase inhibitor. Finasteride, for example, is chemically distinct and falls outside claim 1.

How many claims does US Patent 5,565,467 contain?

The patent has 10 claims. They divide into four practical categories.

Claims	Claim category	Commercial relevance
1	Dutasteride compound and solvates	Core active-ingredient protection
2-3	Dutasteride pharmaceutical formulation	Broad composition coverage
4-6	Dutasteride plus alpha-1 adrenergic receptor blocker	BPH combination products
7-8	Dutasteride plus clomiphene or tamoxifen	Endocrine and reproductive-use combinations
9-10	Dutasteride plus an anti-androgen, specifically flutamide	Combination therapy coverage

The patent does not contain claims directed to a manufacturing process, a specific dosage strength, a specific capsule shell, a particular particle-size distribution, a polymorph, or a method of treating BPH.

What does claim 1 cover?

Claim 1 covers:

Dutasteride or a pharmaceutically acceptable solvate thereof.

This is the strongest claim in the patent from a product perspective because it targets the active compound directly. A product containing dutasteride as its active ingredient would have been exposed to claim 1 during the patent term, regardless of whether it used a different excipient system, capsule design, manufacturer, or commercial name.

Does claim 1 cover dutasteride salts?

The claim recites the compound or a pharmaceutically acceptable solvate. It does not expressly recite salts, esters, prodrugs, stereoisomers, or broad derivatives. A separate chemical form would require a claim-construction and infringement analysis based on whether it is legally the claimed compound or a pharmaceutically acceptable solvate.

The claim also does not expressly require:

A 0.5 mg dose
Oral administration
Treatment of BPH
A capsule
A particular purity level
A particular crystalline form
A particular manufacturing route

That breadth made claim 1 the principal barrier to commercial dutasteride products before expiration.

What do claims 2 and 3 protect?

Claims 2 and 3 cover pharmaceutical formulations containing dutasteride and a pharmaceutically acceptable carrier.

Claim 2 requires:

The compound of claim 1; and
A pharmaceutically acceptable carrier.

Claim 3 adds the requirement that the formulation contain a “safe and effective amount” of dutasteride.

The formulation claims are broad. They do not identify a particular carrier, dosage form, concentration, release profile, or route of administration. A carrier could include conventional excipients used in oral solid dosage forms, including diluents, binders, disintegrants, lubricants, coatings, and capsule materials.

What formulations are protected by claims 2 and 3?

During the patent term, the claims potentially reached formulations such as:

Dutasteride capsules
Dutasteride tablets
Dutasteride suspensions
Dutasteride solutions
Dutasteride-containing oral dosage forms
Dutasteride combined with standard pharmaceutical excipients

The claims do not appear limited to Avodart’s precise commercial formulation. A generic manufacturer using different excipients could still have faced claim 2 or claim 3 if its product contained dutasteride and a pharmaceutically acceptable carrier.

Because claim 1 covers the compound itself, changing the formulation would not have avoided infringement of the compound claim.

What combination products are covered?

Claims 4 through 10 cover formulations combining dutasteride with additional pharmacological agents.

Alpha-1 adrenergic blocker combinations

Claim 4 covers dutasteride formulations that also contain an alpha-1 adrenergic receptor blocker.

Claim 5 identifies six blockers:

Prazosin
Terazosin
Doxazosin
Indoramin
Trimazosin
Tamsulosin, spelled “tamsolosin” in the supplied claim text

Claim 6 narrows the combination to terazosin.

The claim language is composition-based. It requires the formulation to comprise both dutasteride and the specified blocker. It is not written as a method-of-treatment claim and does not expressly require simultaneous administration from a single capsule or tablet.

Jalyn, which combines dutasteride with tamsulosin, falls within the technical subject matter identified by claims 4 and 5. Jalyn was approved by the FDA in 2010 for BPH.[3] The presence of a combination claim in US 5,565,467 did not by itself establish that the patent was the only or final patent relevant to Jalyn.

Anti-estrogen combinations

Claim 7 covers dutasteride combined with clomiphene or tamoxifen. Claim 8 narrows the claim to tamoxifen.

These claims could be relevant to investigational or therapeutic combinations involving androgen suppression and estrogen-modulating therapy. They are not directed to the ordinary Avodart monotherapy product.

Anti-androgen combinations

Claim 9 covers dutasteride combined with an anti-androgen. Claim 10 narrows the claim to flutamide.

Claim 9 is broader than claim 10 because it does not identify a closed list of anti-androgens. The scope would depend on whether the additional agent qualifies as an anti-androgen under the applicable claim-construction standard.

When did US Patent 5,565,467 expire?

The patent was granted on October 15, 1996. Its 17-year patent term expired on October 15, 2013.[1]

Event	Date
US patent grant	October 15, 1996
Statutory expiration	October 15, 2013
Current status	Expired
Core product affected	Dutasteride
Principal branded product	Avodart
Combination product	Jalyn

The patent was prosecuted under the pre-URAA patent-term framework applicable to the relevant application. The expiration date is distinct from FDA regulatory exclusivity. Patent expiration does not eliminate separate regulatory restrictions that may have applied to a later-approved product, formulation, or indication.

What was the Orange Book status of US Patent 5,565,467?

US Patent 5,565,467 was associated with the Avodart regulatory and patent record. The Orange Book identifies patents submitted by NDA sponsors for approved drug products, including patents covering active ingredients, formulations, and approved methods of use.[4]

The patent’s practical Orange Book significance was greatest before October 2013. After expiration, it ceased to provide an active patent basis for blocking an ANDA solely on the strength of this patent.

An Orange Book listing does not itself prove validity or infringement. It identifies the patent information submitted by the NDA holder and establishes the framework for patent certifications by ANDA applicants.

Did the patent support Paragraph IV challenges?

Yes. An ANDA applicant seeking approval before patent expiration could have filed a Paragraph IV certification asserting that the listed patent was invalid, unenforceable, or would not be infringed by the proposed generic product.[5]

For this patent, the principal Paragraph IV attack points would have included:

Anticipation of the dutasteride compound
Obviousness based on prior 5-alpha-reductase inhibitor disclosures
Written-description and enablement issues
Claim scope for solvates
Infringement based on the proposed generic formulation
Whether a formulation containing dutasteride and a carrier fell within claims 2 or 3
Whether a combination product contained the required additional agent

Because claim 1 is a compound claim, a generic manufacturer could not avoid it merely by changing excipients. The most direct noninfringement strategy would have been to launch after expiration or establish that the proposed product did not contain the claimed compound.

A Paragraph IV certification would ordinarily expose the ANDA applicant to patent litigation under the Hatch-Waxman framework. Once the patent expired, the commercial value of a Paragraph IV challenge to this patent ended, although earlier litigation could have affected launch timing.

What was the patent litigation and settlement landscape?

The patent’s historical commercial importance centered on generic dutasteride entry. Litigation involving Avodart-related patents would have been evaluated together with:

US 5,565,467
Other dutasteride compound or formulation patents
Orange Book-listed method-of-use patents
Regulatory exclusivity for the NDA product
Any settlement agreement governing generic launch

The supplied claims do not identify litigation parties, docket numbers, settlements, or ANDA numbers. Those facts cannot be attributed to this patent from the claim text alone.

The key business point is that expiration of US 5,565,467 removed the basic compound patent barrier. A generic applicant could still face separate risks from other patents, but this patent alone no longer supports an injunction against a current dutasteride product.

How strong was the patent estate?

Chemical-claim strength

Claim 1 was commercially strong during its term because it covered the active ingredient directly. It was difficult to design around while retaining dutasteride as the active pharmaceutical ingredient.

Formulation-claim strength

Claims 2 and 3 were broader but potentially more vulnerable to validity and claim-construction challenges because they recited a compound plus a conventional carrier without narrow technical limitations.

Combination-claim strength

Claims 4 through 10 were narrower because infringement required the additional combination component. They were relevant to combination products but less important to dutasteride monotherapy.

Current strength

The patent has no current blocking strength because it is expired. Its residual value is limited to historical prosecution, validity, claim-construction, and freedom-to-operate analysis.

Factor	Assessment during term	Current assessment
Dutasteride compound	Strong	No enforceable exclusivity
Broad formulation	Moderate to strong	No enforceable exclusivity
Alpha-1 blocker combination	Product-dependent	No enforceable exclusivity
Tamoxifen or clomiphene combination	Narrow commercial relevance	No enforceable exclusivity
Flutamide combination	Narrow	No enforceable exclusivity
Manufacturing protection	None apparent from supplied claims	No protection under these claims
Geographic scope	United States only	Expired in the United States

What generic entry risks exist for dutasteride?

A generic dutasteride applicant faced three principal risks before patent expiration:

Compound infringement risk. Any product containing dutasteride could have implicated claim 1.
Formulation infringement risk. A product containing dutasteride and a pharmaceutical carrier could have implicated claims 2 or 3.
Separate patent and regulatory risk. Other Orange Book patents, method-of-use claims, regulatory exclusivities, and litigation settlements could have affected launch timing.

After October 15, 2013, claim 1 no longer blocked generic dutasteride. The principal remaining risks shifted to other patents, product-specific regulatory requirements, manufacturing controls, and market competition.

How does dutasteride patent protection compare with finasteride?

Finasteride and dutasteride are both 5-alpha-reductase inhibitors, but they are covered by separate patent estates.

Issue	Dutasteride	Finasteride
Key product	Avodart	Proscar, Propecia
Enzyme activity	Type 1 and type 2 inhibition	Primarily type 2 inhibition
US 5,565,467 coverage	Directly covers dutasteride	Does not cover finasteride
Core patent status	Expired October 15, 2013	Separate historical patent estate
Combination relevance	Includes alpha-1 blockers and anti-androgens	Separate claims and products
Generic strategy	Dutasteride-specific ANDA and patent analysis	Finasteride-specific analysis

A finasteride generic cannot rely on the expiration of US 5,565,467, and a dutasteride generic cannot rely on the expiration of finasteride patents. The products require separate freedom-to-operate assessments.

Does US 5,565,467 create biosimilar risk?

No. Dutasteride is a chemically synthesized small molecule, not a biologic. The relevant competitive pathway is an ANDA for a generic drug, not a biosimilar application under the Public Health Service Act.

The principal regulatory issues are bioequivalence, pharmaceutical equivalence, labeling, manufacturing quality, and any remaining listed patents. FDA approval of a generic dutasteride product does not require biosimilarity evidence.

Key Takeaways

US Patent 5,565,467 covers dutasteride and pharmaceutically acceptable solvates.
Claims 2 and 3 cover broad dutasteride pharmaceutical formulations.
Claims 4 through 10 cover combinations with alpha-1 blockers, anti-estrogens, and anti-androgens.
The patent does not claim a manufacturing process, a specific dosage strength, a polymorph, or a treatment method.
The patent expired on October 15, 2013.
It no longer blocks generic dutasteride in the United States.
Historical Paragraph IV exposure focused primarily on the direct compound claim and broad formulation claims.
Dutasteride is a small molecule, so generic competition proceeds through the ANDA pathway rather than biosimilar regulation.
Separate Avodart or Jalyn patents, regulatory exclusivities, and litigation settlements must be analyzed independently of US 5,565,467.

FAQs About US Patent 5,565,467 and Dutasteride

Is US 5,565,467 still enforceable?

No. The patent expired on October 15, 2013.

Does US 5,565,467 cover Avodart?

Yes. Claim 1 covers dutasteride, the active ingredient in Avodart. Claims 2 and 3 also cover formulations containing dutasteride and a pharmaceutical carrier.

Does the patent cover Jalyn?

The combination subject matter in claims 4 and 5 includes dutasteride with tamsulosin. Jalyn contains dutasteride and tamsulosin. Separate patents and regulatory rights must be evaluated for the marketed product.

Can a generic manufacturer avoid the patent by changing capsule excipients?

Changing excipients would not have avoided claim 1 during the patent term if the product still contained dutasteride. It could have affected formulation-claim analysis under claims 2 and 3.

Is a new dutasteride salt protected by claim 1?

Not automatically. Claim 1 expressly covers dutasteride and pharmaceutically acceptable solvates, but it does not expressly claim every salt, ester, prodrug, or derivative of dutasteride.

References

United States Patent and Trademark Office. (1996). US Patent No. 5,565,467, 4-aza steroidal compounds as 5-alpha reductase inhibitors.
U.S. Food and Drug Administration. (2001). Avodart prescribing information: Dutasteride capsules.
U.S. Food and Drug Administration. (2010). FDA approves Jalyn for treatment of benign prostatic hyperplasia.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, 44th edition.
U.S. Food and Drug Administration. (2015). Approved drug products and patent certifications under the Hatch-Waxman Act.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0719278	⤷ Start Trial	300122	Netherlands	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	SPC/GB03/018	United Kingdom	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	PA2003007	Lithuania	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	PA2003007,C0719278	Lithuania	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	SPC009/2005	Ireland	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	C300122	Netherlands	⤷ Start Trial
European Patent Office	0719278	⤷ Start Trial	PA 2003 007, C 0719278 /L	Lithuania	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,565,467

Summary for Patent: 5,565,467