United States Patent 4,760,071: Finasteride Claims, Scope, Expiration, and Patent Landscape

United States Patent No. 4,760,071 covers finasteride as a chemical compound, specified therapeutic uses, inhibition of testosterone 5α-reductase, and pharmaceutical compositions containing finasteride. The patent was assigned to Merck & Co. and issued on July 26, 1988. Its principal commercial subject matter was later marketed as Proscar 5 mg for benign prostatic hyperplasia and Propecia 1 mg for male pattern hair loss.

The patent has expired. Its claims no longer create a blocking U.S. patent position for finasteride manufacture, sale, formulation, or use. Current commercial risk is therefore driven by regulatory requirements, manufacturing know-how, trademarks, product quality, and later patents rather than by Patent 4,760,071 itself.

What drug does United States Patent 4,760,071 protect?

The patent protects finasteride, chemically identified in claim 1 as:

17β-(N-tert-butylcarbamoyl)-4-aza-5α-androst-1-en-3-one

This is the active pharmaceutical ingredient in Proscar and Propecia. The compound is a 4-aza steroid that inhibits steroid 5α-reductase, the enzyme that converts testosterone to dihydrotestosterone, or DHT.

Patent element	Commercial relevance
U.S. patent	4,760,071
Patent holder	Merck & Co.
Active ingredient	Finasteride
Principal products	Proscar 5 mg; Propecia 1 mg
Therapeutic class	5α-reductase inhibitor
Original claim structure	Compound, treatment methods, enzyme inhibition, composition
Issue date	July 26, 1988
U.S. status	Expired
Biosimilar pathway	Not applicable; finasteride is a small molecule

The chemical claim is directed to the named compound rather than to a broad genus of 4-aza steroids. It does not, on its face, claim every 5α-reductase inhibitor, every finasteride analog, or every DHT-lowering agent.

What is the scope of claim 1 of Patent 4,760,071?

Claim 1 is a single-compound claim. It covers finasteride itself, including the stereochemical configuration specified by the claim.

The claim has several legal and commercial consequences:

It protects the active molecule independently of a particular indication.
It is not limited to a specific tablet strength, excipient, route of administration, or commercial brand.
It is not limited to Proscar or Propecia.
It does not expressly claim a dosage regimen.
It does not expressly claim a particular crystalline form, particle size, coating, sustained-release system, or manufacturing process.

A product containing finasteride would have fallen within the compound claim during the patent term regardless of whether it was labeled for benign prostatic hyperplasia, androgenic alopecia, or another approved or unapproved use.

The claim also has practical limits. A chemically different salt, ester, prodrug, metabolite, analog, or polymorph would require separate claim analysis. Whether a modified form falls within the claim would depend on its chemical identity and the applicable claim-construction and infringement rules. The claim does not automatically reach all compounds that produce the same pharmacological effect.

What methods of treatment are protected by claim 2?

Claim 2 covers administering a therapeutically effective amount of finasteride to treat:

Acne vulgaris
Seborrhea
Female hirsutism
Benign prostatic hypertrophy

The claim is a method-of-treatment claim. It requires both administration of finasteride and treatment of one of the listed hyperandrogenic conditions.

The claim is not a general claim to every dermatological or androgen-related use. It is tied to the conditions identified in the claim. It also requires a patient in need of treatment and a therapeutically effective amount.

The BPH portion of claim 2 is commercially significant because finasteride was approved as Proscar for symptomatic treatment of BPH and reduction of the risk of acute urinary retention and surgery. The FDA-approved Propecia label covers male pattern hair loss, which is not one of the conditions listed in claim 2. [2][3]

Claim 2 does not expressly cover:

Male pattern hair loss
A particular 5 mg or 1 mg dose
A specific dosing frequency
A specific duration of treatment
Combination therapy with an alpha blocker
A specific patient age group
A particular pharmaceutical formulation

Those limitations were addressed, where applicable, by other patents, regulatory labeling, or product development decisions.

How broad is claim 3 covering 5α-reductase inhibition?

Claim 3 covers administering finasteride to a patient for the purpose of inhibiting testosterone 5α-reductase.

This claim is broader in functional terms than claim 2 because it is not limited to acne, seborrhea, hirsutism, or BPH. It focuses on the pharmacological activity of the compound.

The claim still requires:

A patient in need of 5α-reductase inhibition.
Administration of finasteride.
A therapeutically effective amount.
The claimed treatment objective of enzyme inhibition.

The claim does not cover inhibition of every androgen pathway. It is directed to testosterone 5α-reductase. It also does not claim the enzyme as a biological target in isolation, nor does it claim all compounds that inhibit the enzyme.

From a patent enforcement perspective, claim 3 could have been relevant to uses outside the specific diseases named in claim 2. Its practical value was greatest while claim 1 remained enforceable, because a commercial manufacturer of finasteride would ordinarily face the compound claim regardless of the proposed indication.

What pharmaceutical compositions are protected by claim 4?

Claim 4 covers a pharmaceutical composition comprising:

A pharmaceutically acceptable carrier; and
An effective amount of finasteride.

This is a broad composition claim. It is not limited to tablets, capsules, oral liquids, topical products, or a particular excipient system. A composition containing finasteride and a pharmaceutically acceptable carrier could have fallen within the claim during the patent term.

The claim does not specify:

Finasteride concentration
Tablet strength
Release profile
Excipients
Coating
Particle size
Manufacturing process
Packaging
Route of administration
Patient population

The broad language distinguishes claim 4 from a narrowly drafted formulation patent. A later patent directed to a specific tablet formulation, coating, dosage regimen, or manufacturing process could have had independent scope, but claim 4 itself is not a detailed formulation patent.

When did Patent 4,760,071 lose exclusivity?

Patent 4,760,071 is expired. Public pharmaceutical patent records commonly identify June 19, 2006 as the relevant expiration date for the finasteride patent estate associated with this patent family. The patent therefore no longer blocks generic manufacture or sale of finasteride in the United States. [1][4]

Event	Date or status
Patent issued	July 26, 1988
Proscar FDA approval	June 19, 1992
Propecia FDA approval	December 19, 1997
Core finasteride patent expiration	June 19, 2006
Current enforceability of Patent 4,760,071	None

The expiration of the patent did not eliminate FDA requirements. A generic applicant still needed an approved ANDA, including bioequivalence data and compliance with applicable manufacturing and labeling standards.

What is the Orange Book status of finasteride?

Finasteride has historically been listed in the FDA Orange Book through the reference products Proscar and Propecia. The Orange Book records patents and exclusivity associated with approved drug products, including products approved under the New Drug Application pathway. [4]

The relevant commercial products are:

Product	Active ingredient	Strength	Approved use
Proscar	Finasteride	5 mg	Benign prostatic hyperplasia
Propecia	Finasteride	1 mg	Male pattern hair loss

Patent 4,760,071 is no longer a live Orange Book barrier. Later use patents, including patents associated with finasteride for androgenic alopecia, were more relevant to generic launch timing for specific labels. A generic company could seek approval for a label that carved out patented indications under the ANDA section viii pathway where legally and regulatorily available.

Which companies challenged finasteride patent exclusivity?

Generic competition developed after expiration of the core compound protection and later use-patent barriers. Companies that have marketed or obtained U.S. approval for generic finasteride products include major generic manufacturers such as Teva, Dr. Reddy’s Laboratories, and other ANDA sponsors.

Paragraph IV challenges were commercially relevant before expiration of later Merck patents. A Paragraph IV certification asserts that a listed patent is invalid, unenforceable, or not infringed. Filing such a certification can trigger patent litigation under the Hatch-Waxman Act. [5]

For Patent 4,760,071 itself, the current Paragraph IV risk is zero because an expired patent cannot support an injunction against a new ANDA applicant. Historical litigation or settlement activity involving later Merck patents should not be attributed automatically to the claims of Patent 4,760,071.

What later patents affected Proscar and Propecia?

The finasteride estate extended beyond Patent 4,760,071. Later patents addressed particular uses, dosage regimens, and commercial indications.

Propecia and androgenic alopecia patents

Male pattern hair loss was commercially protected through later Merck patents rather than through the four claims quoted from Patent 4,760,071. U.S. Patent No. 5,547,957 is associated with methods of treating androgenic alopecia using finasteride and had a later expiration than the original compound patent. [6]

This distinction matters because:

Patent 4,760,071 claim 2 lists female hirsutism but not male pattern hair loss.
Propecia was approved for male pattern hair loss in 1997.
Later method-of-use patents could affect a generic product seeking a full hair-loss label.
Expiration of the compound patent did not necessarily eliminate all method-of-use restrictions immediately.

Proscar and BPH use

The BPH indication was directly aligned with claim 2. Later patents and regulatory exclusivity could affect the timing and labeling of generic 5 mg finasteride products, but the core molecule was no longer protected after the 2006 expiration.

What was the FDA regulatory exclusivity timeline?

FDA milestone	Product and indication
June 19, 1992	Proscar approved for BPH
December 19, 1997	Propecia approved for male pattern hair loss
After patent expiry	Generic finasteride approvals expanded
Current regulatory category	Small-molecule generic drug; ANDA pathway

Finasteride is not a biologic. Biosimilar analysis does not apply. Generic applicants rely on the ANDA pathway and must demonstrate pharmaceutical equivalence and bioequivalence to the relevant reference product. [2][3][7]

Regulatory exclusivity and patent exclusivity are separate. FDA approval dates identify the regulatory history, while the Orange Book identifies listed patents and exclusivity. Neither the Proscar nor Propecia brand retains a current monopoly over finasteride based on Patent 4,760,071.

How strong was the patent estate for finasteride?

During its term, the estate was strong because claim 1 covered the active pharmaceutical ingredient directly. A direct compound claim generally creates a substantial barrier to an ANDA applicant because changing the formulation or manufacturer does not avoid infringement of the molecule claim.

The estate was weaker in three areas:

The quoted use claims did not include every commercially relevant finasteride indication.
Claim 4 lacked detailed formulation limitations and therefore offered limited differentiation from later formulation patents.
Once the compound patent expired, the principal barrier to generic entry shifted to later method-of-use patents and regulatory labeling.

Estate component	Strength during term	Current status
Compound claim	Very strong; direct API coverage	Expired
BPH method claim	Relevant to Proscar	Expired
5α-reductase inhibition claim	Broad functional use coverage	Expired
Composition claim	Broad but nonspecific	Expired
Later hair-loss methods	Relevant to Propecia	Later patents also expired or no longer commercially blocking
Manufacturing know-how	Potentially valuable	May remain confidential if not disclosed

What generic entry risks exist for finasteride?

Generic entry risk for finasteride is no longer primarily patent-based. The main commercial risks are:

FDA approval and bioequivalence requirements
Product quality and supply reliability
API sourcing
Stability and dissolution performance
Label carve-outs for protected indications, where applicable
Trademark restrictions involving Proscar and Propecia
Competition among established generic manufacturers
Pricing pressure in the 1 mg and 5 mg tablet markets

There is no biosimilar risk because finasteride is a synthetic small molecule. There is also no current blocking claim in Patent 4,760,071 against an approved generic finasteride tablet.

Does Patent 4,760,071 create current licensing or litigation exposure?

No current licensing obligation arises solely from the expired claims of Patent 4,760,071. Historical commercial agreements involving Merck, distributors, or generic manufacturers do not revive expired patent rights.

Any current dispute would more likely concern:

Trademark use
Product labeling
False or misleading promotional claims
Manufacturing patents unrelated to the expired compound claim
Confidential information
Contractual rights
State-law commercial conduct

The expired patent itself cannot support a current infringement action for making, using, selling, or importing finasteride in the United States.

Key Takeaways

Patent 4,760,071 covers finasteride as a compound, selected treatment methods, 5α-reductase inhibition, and pharmaceutical compositions.
Claim 1 is the principal commercial claim because it covers the active ingredient directly.
Claim 2 covers acne vulgaris, seborrhea, female hirsutism, and BPH, but not male pattern hair loss.
Claim 3 is a functional method claim directed to inhibition of testosterone 5α-reductase.
Claim 4 broadly covers finasteride pharmaceutical compositions with a pharmaceutically acceptable carrier.
The patent expired on the commonly reported June 19, 2006 expiration date.
Propecia’s male pattern hair-loss protection depended primarily on later method-of-use patents.
Finasteride is a small molecule, so biosimilar analysis does not apply.
Current generic entry is governed by ANDA requirements, bioequivalence, labeling, supply, and commercial pricing rather than Patent 4,760,071.
No current Paragraph IV challenge is needed to overcome this expired patent.

FAQs About U.S. Patent 4,760,071 and Finasteride

Does Patent 4,760,071 cover Propecia?

It covers finasteride, the active ingredient in Propecia, but the quoted method claim does not expressly recite male pattern hair loss. Propecia protection was associated with later patents directed to androgenic alopecia.

Does Patent 4,760,071 cover generic finasteride tablets?

It covered generic finasteride tablets during its enforceable term. Because the patent is expired, it no longer blocks approved generic finasteride tablets.

Is finasteride protected by a formulation patent?

Patent 4,760,071 contains a broad composition claim but does not specify a detailed formulation. Any current formulation protection would need to arise from a separate, unexpired patent.

Can finasteride be approved through the biosimilar pathway?

No. Finasteride is a synthetic small-molecule drug. Generic products use the ANDA pathway rather than the biosimilar pathway.

Did expiration of Patent 4,760,071 immediately eliminate all Propecia patent barriers?

No. Later use patents, particularly those associated with male pattern hair loss, could have affected the timing and scope of generic labeling after expiration of the original compound patent.

References

U.S. Patent and Trademark Office. (1988). U.S. Patent No. 4,760,071: 4-aza steroids.
U.S. Food and Drug Administration. (2024). Proscar (finasteride) prescribing information.
U.S. Food and Drug Administration. (2024). Propecia (finasteride) prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Appendix C: Patent certifications.
U.S. Patent and Trademark Office. (1996). U.S. Patent No. 5,547,957: Treatment of androgenic alopecia with 5α-reductase inhibitors.
U.S. Food and Drug Administration. (2024). ANDA approvals and abbreviated new drug application requirements.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0155096	⤷ Start Trial	SPC/GB93/006	United Kingdom	⤷ Start Trial
European Patent Office	0155096	⤷ Start Trial	93C0055	Belgium	⤷ Start Trial
Austria	46912	⤷ Start Trial
Austria	67503	⤷ Start Trial
Austria	78827	⤷ Start Trial
Australia	2748192	⤷ Start Trial
Australia	3313589	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,760,071

Summary for Patent: 4,760,071