United States Drug Patent 3,850,911: Claim Scope, Expiration, and Steroid Patent Landscape

U.S. Patent 3,850,911 is an early-1970s steroid genus patent. The supplied Claim 1 attempts to cover a broad class of cyclopentanophenanthrene compounds, including gonane and 8-isogonane nuclei bearing a carbon substituent at the steroid 13-position. Its ordinary patent term expired in the early 1990s. It therefore creates no current U.S. exclusivity, Orange Book barrier, Paragraph IV risk, or enforceable generic-launch delay.

The claim has commercial relevance as historical prior art and as a possible reference in validity, freedom-to-operate, or patent-family analyses involving 13-alkyl steroid structures. It does not provide a current blocking right.

What does U.S. Patent 3,850,911 claim?

Claim 1 is a composition-of-matter genus claim. In corrected conceptual form, it covers a chemical compound that satisfies all of the following conditions:

Claim limitation	Practical meaning
Cyclopentanophenanthrene carbon-carbon skeleton	The compound must have the fused four-ring steroid framework
19 to approximately 40 carbon atoms	The total carbon count must fall within the stated range
At least partial hydrogenation of the B and C rings	The B and C steroid rings cannot be completely unrestricted aromatic or unsaturated systems
Gonane or 8-isogonane nucleus	The core must belong to one of two specified steroid nucleus families
No more than five double bonds	The total unsaturation in the relevant nucleus is capped
Carbon substituent at the 13-position	A monovalent polycarbon alkyl radical must be attached at, or form part of, the 13-position
Substituent of 2 to approximately 16 carbon atoms	The 13-position group must contain at least two and up to about 16 carbon atoms

The claim is drafted as a single broad genus rather than as a claim to one named active pharmaceutical ingredient. It does not, on its face, require a particular hydroxyl group, ketone, ester, halogen, stereochemical configuration, therapeutic indication, dosage form, salt, or formulation.

How should the claim language be interpreted?

The supplied text contains apparent transcription or OCR defects. The phrases "at least B and the C ring," "8ISOGONANE," and "F monovalent" are likely intended to refer to:

the B and C rings;
an 8-isogonane nucleus; and
a monovalent polycarbon alkyl radical.

Those defects matter in a litigation-grade claim construction. The official patent image, issued claims, prosecution history, and any certificate of correction control over an OCR transcription.

The claim should be analyzed as requiring a conjunctive match. A compound outside any one of the following categories should not literally infringe Claim 1:

the steroid carbon skeleton;
the 19-to-40-carbon range;
the gonane or 8-isogonane nucleus;
the hydrogenation limitation;
the five-double-bond maximum; or
the 13-position alkyl substituent limitation.

A compound with a 13-position substituent containing only one carbon would fall outside the stated 2-to-16-carbon range. A compound with more than 40 total carbon atoms would also fall outside the claim. A compound based on an unrelated steroid nucleus, such as a modified pregnane or androstane framework that cannot be mapped to the claimed gonane or 8-isogonane nucleus, presents a separate non-infringement issue.

What is the technical scope of the 13-position limitation?

The 13-position limitation is the central structural feature. In ordinary steroid nomenclature, C-13 is part of the fused-ring steroid framework and is associated with the angular C-18 methyl region in conventional steroids. A claim requiring a larger carbon substituent at this location attempts to capture 13-alkyl-substituted steroid structures rather than conventional unsubstituted steroid nuclei.

The phrase "monovalent polycarbon alkyl radical" is broad but not unlimited. It generally indicates a monovalent hydrocarbon substituent containing multiple carbon atoms. The exact scope would depend on whether the patent specification defines the term to include:

straight-chain alkyl groups;
branched-chain alkyl groups;
cycloalkyl groups;
alkenyl or alkynyl groups;
substituted hydrocarbon groups; or
only saturated acyclic alkyl groups.

Without a controlling definition, "alkyl" would ordinarily be narrower than "hydrocarbon radical." A litigant would likely argue that an aromatic, heteroatom-containing, or heavily unsaturated substituent is outside the ordinary meaning of the term unless the specification expands it.

The phrase "about 16 carbon atoms" introduces additional interpretive flexibility. The lower limit of two carbon atoms is relatively clear. The upper boundary is less certain because "about" can encompass a modest deviation depending on the intrinsic evidence and prosecution history.

Does Claim 1 cover specific marketed steroid drugs?

The claim cannot be mapped confidently to a marketed drug from the text alone. It is a structural genus claim and may cover many compounds that never became products.

The claim should not automatically be equated with patents for:

levonorgestrel;
etonogestrel;
desogestrel;
norethindrone;
testosterone derivatives;
corticosteroids; or
anabolic steroids.

Many marketed steroid drugs have a conventional C-13 methyl arrangement, different ring unsaturation, different carbon counts, or a different steroid nucleus. A specific drug would require an atom-by-atom structural mapping against the issued claim and the patent specification.

What structures are most likely to fall within the genus?

The strongest candidates are compounds that have:

a gonane or 8-isogonane core;
a 13-position ethyl, propyl, butyl, or larger hydrocarbon substituent;
no more than five double bonds in the claimed nucleus;
partial hydrogenation in the B and C rings; and
a total carbon count between 19 and 40.

A compound with a conventional 13-methyl steroid structure would not satisfy the express requirement for a 2-to-16-carbon 13-position radical unless the claim’s nomenclature is interpreted differently from its apparent wording.

How strong is the patent estate for U.S. Patent 3,850,911?

The patent estate appears weak as a current commercial asset because the patent term expired decades ago. Its historical claim breadth was potentially substantial, but broad genus claims of this type face several technical and legal pressure points.

Issue	Effect on claim strength
Broad structural genus	Increases theoretical coverage but raises written-description and enablement questions
Undefined or ambiguous terminology	Creates claim-construction and indefiniteness risk
"About 16 carbon atoms"	Makes the upper boundary less precise
"At least partially hydrogenated"	May require specification-based interpretation
Five-double-bond limitation	Provides a measurable boundary but may create design-around routes
13-position substituent	Gives the claim a distinctive structural focus
Old priority date	Increases exposure to earlier steroid chemistry references
Expired term	Eliminates present enforcement value

Under pre-Uruguay Round patent law, the ordinary U.S. term was 17 years from grant. Patent 3,850,911 was granted in the 1970s, placing its ordinary expiration in the early 1990s. Patent-term adjustments and modern 20-year-from-filing rules do not generally convert such an expired pre-1995 patent into a live exclusion right. [1]

When did U.S. Patent 3,850,911 lose exclusivity?

The patent lost enforceable U.S. exclusivity when its statutory term ended, approximately 17 years after its 1974 grant. The patent therefore expired around 1991.

The practical consequences are direct:

no current injunction based solely on this patent;
no current royalty demand based solely on ordinary patent rights;
no patent-based generic launch stay;
no live Paragraph IV certification directed to this patent;
no Orange Book listing that can block an abbreviated new drug application; and
no current biosimilar reference-product exclusivity based on this patent.

A later improvement patent, formulation patent, process patent, or method-of-use patent could still matter independently. Expiration of 3,850,911 does not eliminate later patents covering a particular product.

What is the Orange Book status of U.S. Patent 3,850,911?

U.S. Patent 3,850,911 is not a current Orange Book barrier. The Orange Book lists patents submitted for approved drug products and relevant to approved uses, dosage forms, or drug substances. A broad historical steroid genus patent does not itself create an Orange Book listing.

Even if the patent had once been associated with a drug product, its expiration would eliminate any current statutory delay based on that patent. FDA Orange Book exclusivity must be analyzed at the approved-product level, not from the patent number alone. [2]

Are there Paragraph IV challenges or generic entry risks?

There is no meaningful current Paragraph IV risk relating to U.S. Patent 3,850,911 because the patent is expired. Paragraph IV litigation is relevant when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. An expired patent cannot ordinarily support a 30-month stay of FDA approval.

The current generic-entry analysis instead turns on:

later unexpired compound patents;
polymorph or solid-state patents;
formulation and delivery patents;
method-of-use patents;
manufacturing-process patents;
regulatory exclusivity; and
controlled-substance or other regulatory requirements where applicable.

For a product whose only relevant patent is 3,850,911, patent-based generic entry risk is effectively zero because the patent no longer excludes entry.

Does the patent create biosimilar risk?

No meaningful biosimilar issue arises from this patent. Biosimilar litigation concerns biologic reference products, whereas Claim 1 is directed to small-molecule steroid compounds. A later biologic or peptide product would not be analyzed under this claim unless its structure somehow satisfied the claim, which is not a realistic pathway for ordinary biologic medicines.

The relevant competitive threat is generic, not biosimilar.

What formulation and method-of-use protection exists?

The supplied Claim 1 contains no apparent formulation limitation. It does not require:

a tablet;
capsule;
injectable composition;
transdermal system;
implant;
specific excipient;
particle size;
release profile;
dosage strength; or
pharmaceutical carrier.

It also does not recite a therapeutic method. There is no express limitation requiring treatment of contraception, inflammation, oncology, androgen deficiency, endocrine disease, or another indication.

Any such protection would have to arise from separate claims in the patent or from related continuation, divisional, foreign, or later-filed patents. Claim 1 alone is a compound claim, not a formulation or method-of-use claim.

What manufacturing and intellectual-property barriers remain?

Manufacturing barriers could remain even though the composition claim is expired. A company commercializing a steroid compound may still face:

later process patents covering a particular synthetic route;
intermediate patents;
stereoselective or catalytic manufacturing patents;
purification or crystallization patents;
polymorph patents;
formulation patents;
combination-product patents; and
regulatory requirements for impurity control and batch consistency.

The expired claim does not authorize use of third-party process technology. It only removes the exclusionary effect of the specific compound claim after expiration.

What geographic coverage does the patent provide?

U.S. Patent 3,850,911 had territorial effect only in the United States. Any corresponding protection in Europe, Japan, Canada, or other jurisdictions required separately granted national or regional patents.

Foreign counterpart patents would have expired at different times depending on:

the filing date;
local patent-term rules;
maintenance-fee compliance;
prosecution delay;
terminal disclaimers; and
national renewal status.

The U.S. patent cannot be used to prevent manufacture, sale, or importation outside the United States.

What litigation or settlement exposure remains?

The patent’s expiration removes the principal present litigation threat. A historical infringement action, license, or settlement could be relevant to understanding commercial development, but it cannot extend the patent term or revive an expired exclusion right.

Any current dispute would more likely concern:

ownership of know-how;
trade secrets;
later patents;
contractual royalty obligations;
patent-term representations in a license;
regulatory data rights; or
infringement of a separate patent family.

A settlement involving an expired patent would not itself create patent exclusivity unless supported by separate contractual rights.

How does this patent compare with later steroid patent estates?

Attribute	U.S. 3,850,911	Later product patent estate
Claim type	Broad steroid compound genus	Often narrower compound, formulation, process, or use claims
Commercial status	Historical and expired	May remain active depending on filing date
Regulatory relevance	No current Orange Book effect	Can affect ANDA or 505(b)(2) timing
Generic risk	No patent-based barrier	Depends on remaining claims and litigation
Biosimilar relevance	None	Usually none for small molecules
Technical strength	Broad but interpretation-sensitive	Often narrower and easier to map to a product
Design-around options	Potentially substantial at structural boundaries	Depends on molecule and delivery system

Key Takeaways

Claim 1 is a broad composition-of-matter genus claim directed to 13-alkyl-substituted gonane and 8-isogonane steroid structures.
The key limitations are the steroid nucleus, 19-to-40-carbon range, maximum of five double bonds, partial B/C-ring hydrogenation, and 2-to-16-carbon substituent at C-13.
The supplied claim contains OCR or transcription defects that should be checked against the official issued patent.
The patent’s ordinary U.S. term expired around 1991.
It has no current Orange Book, Paragraph IV, generic-stay, biosimilar, or enforceable exclusivity effect.
The claim may remain relevant as historical prior art in validity and freedom-to-operate analyses.
Later process, formulation, method-of-use, polymorph, or delivery patents must be analyzed separately.
A marketed steroid cannot be treated as covered without an atom-by-atom comparison to the issued claim.

FAQs

Can an expired U.S. steroid patent still block FDA approval?

No. An expired patent cannot ordinarily support a current Orange Book patent stay or prevent FDA approval. Later unexpired patents or regulatory exclusivities may still affect approval timing.

Does a 13-methyl steroid infringe a claim requiring a 2-to-16-carbon 13-position radical?

Not on the apparent wording. A methyl group contains one carbon, while the claim specifies a substituent containing at least two carbon atoms. The specification and prosecution history could affect construction, but the literal limitation is unfavorable to coverage of a simple 13-methyl group.

Can U.S. Patent 3,850,911 be asserted against a process for making a steroid?

Not after expiration as a live patent right. During its term, a product claim could potentially reach the resulting compound, but it would not automatically cover every manufacturing process. Process liability would require a valid process or product claim and proof of infringement.

Does the patent cover salts, esters, or prodrugs of a claimed steroid?

Coverage depends on whether the resulting derivative still satisfies the carbon-skeleton, nucleus, carbon-count, and 13-position limitations. A salt may preserve the claimed compound, while an ester or prodrug may alter the claimed chemical structure and require separate analysis.

Are foreign patents corresponding to U.S. Patent 3,850,911 still enforceable?

They are unlikely to remain in force given the age of the U.S. patent, but foreign status is jurisdiction-specific. Each national or regional counterpart must be checked for grant, lapse, expiration, and maintenance history.

References

United States Code, 35 U.S.C. § 154. Patent term and grant provisions.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
U.S. Patent No. 3,850,911. (1974). Claim 1 concerning cyclopentanophenanthrene steroid compounds with gonane and 8-isogonane nuclei. United States Patent and Trademark Office.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	256353	⤷ Start Trial
Austria	264728	⤷ Start Trial
Austria	264731	⤷ Start Trial
Austria	268544	⤷ Start Trial
Austria	281313	⤷ Start Trial
Austria	282083	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 3,850,911

Summary for Patent: 3,850,911