United States Patent 5,210,081 Scope, Claims, and US Patent Landscape for Alkali Metal Salts of 8,9-Dehydroestrone-3-Sulfate

Executive summary: US Patent 5,210,081 claims compositions of matter centered on alkali metal salts of 8,9-dehydroestrone-3-sulfate ester (core genus), with dependent claim coverage that (i) limits the cation to Na, K, or Li, (ii) adds a specific buffer/excipient interaction with tris(hydroxymethyl)aminomethane (TRIS), and (iii) imposes a mixing ratio range for the TRIS/cation-sulfate combination. The claim set is narrow in drug substance identity but broad across alkali cations (for the genus) and broad across “free from other estrogenic steroids” (exclusionary). The patent landscape risk is dominated by two infringement axes: salt identity (is it an alkali metal salt of the same sulfate ester?) and formulation composition (does it include TRIS within the specified ratio and is it “free from other estrogenic steroids”)? The enforceable scope is therefore most sensitive to product formulation facts and analytical proof.

What does US Patent 5,210,081 claim for alkali metal salts of 8,9-dehydroestrone-3-sulfate?

Direct answer (claim scope): The patent claims compositions of matter comprising an alkali metal salt of 8,9-dehydroestrone-3-sulfate ester, plus (in select claims) a TRIS component and an exclusion limitation against other estrogenic steroids.

Independent claim coverage: claim 1

Claim 1 is the central scope driver:

“A composition of matter consisting essentially of an alkali metal salt of 8,9-dehydroestrone-3-sulfate ester.”

Key legal and technical implications:

“Consisting essentially of” is a transitional phrase that permits some additional components, but only if they do not materially affect the basic and novel characteristics of the claimed invention. Here, the basic characteristics are the specific chemical identity: alkali metal salt of 8,9-dehydroestrone-3-sulfate ester.
“Alkali metal salt” is not limited in the independent claim to Na, K, Li, but dependent claims specify those. Practically, the independent claim gives coverage across alkali cations that fall within “alkali metal.”
“8,9-dehydroestrone-3-sulfate ester” is the core chemical anchor. Any design-around that changes the steroid scaffold, substitution position, sulfate linkage, or esterification chemistry can move out of claim coverage.

Dependent claim expansion: claims 2–4

Claim 2: sodium salt
Claim 3: potassium salt
Claim 4: lithium salt

These create explicit additional coverage for three likely commercial salts, supporting enforceability and aiding claim construction if the independent claim is construed narrowly.

Formulation-specific coverage: claims 5–6

Claim 5: alkali metal salt + TRIS (tris(hydroxymethyl)aminomethane), with “free from other estrogenic steroids.”
Claim 6: same as claim 5, with a TRIS : alkali metal salt ratio from 1:0.5 to 0.5:1.

The ratio range inverts between the components and can be read as a band where neither TRIS nor the salt is overwhelmingly predominant. The numeric band reduces ambiguity versus broader “amounts effective” language and narrows infringement to products whose formulation ratios fall within that window.

Exclusion limitation appears in formulation claims: claims 5 and 7

Claim 5 includes “free from other estrogenic steroids.”
Claim 7 recites an alkali metal salt “free from other estrogenic steroids.”

This matters because “free from” can be litigated via:

specification of impurity profile (analytical method-defined),
manufacturing controls (what must be excluded),
and whether trace levels still satisfy the “free from” requirement under claim construction.

Cation specification in salt claims: claims 8–10

Claim 8: sodium salt
Claim 9: potassium salt
Claim 10: lithium salt

Together, these reinforce that the formulation exclusion limitation and the “free from other estrogenic steroids” concept are intended to attach to specific alkali metal salts.

How broad is “alkali metal salt of 8,9-dehydroestrone-3-sulfate ester” under claim 1?

Direct answer: The independent claim is broad in cation scope (any alkali metal) but narrow in chemical identity (same steroid-sulfate ester and salt form). The main breadth is across salts, not across the steroid framework.

Cation coverage and how dependent claims affect construction

Because dependent claims enumerate Na, K, and Li, a court may still interpret “alkali metal” broadly in claim 1, but the presence of explicit cation claims supports that at least Na/K/L are contemplated as embodiments.
If the specification ties the chemistry to those salts, the practical “effective scope” can narrow even if the literal claim remains broad.

Salt form and product reality

In practice, “alkali metal salt” infringement turns on whether the marketed API or composition contains:

the ionic salt form of the targeted sulfate ester, not merely free base or other salt types (e.g., calcium, ammonium, or organic amines),
and whether the product includes TRIS within the dependent claims 5–6.

What is the scope of the “free from other estrogenic steroids” limitation?

Direct answer: The “free from other estrogenic steroids” language is an exclusion requirement that can constrain both salt-only products (claim 7) and TRIS-containing formulations (claim 5). It can be litigated based on impurity definitions, analytical detection limits, and manufacturing tolerances.

Where the exclusion shows up

Claim 5: alkali salt + TRIS, free from other estrogenic steroids
Claim 7: alkali salt, free from other estrogenic steroids

Practical infringement levers

A product can fall outside claims 5 and 7 if it intentionally includes or unavoidable manufactures other estrogenic steroids above a claim-constructed threshold. A defense argument typically centers on:

analytical detection limits,
whether included materials are “estrogenic steroids” as construed by claim terms,
and whether “free from” means “no detectable” or “below a specified amount.”

This limitation is likely to be the highest-friction issue for formulation and manufacturing challenges because it requires an evidentiary showing tied to control strategy and analytical testing.

What does the TRIS ratio limitation in claim 6 cover?

Direct answer: Claim 6 limits the composition of claim 5 to a TRIS : alkali metal salt ratio from 1:0.5 to 0.5:1. That range is the infringement gate for products using TRIS with this steroid sulfate salt.

Interpreting the ratio mathematically

The range states:

Lower bound: 1:0.5 (TRIS higher relative to salt)
Upper bound: 0.5:1 (salt higher relative to TRIS)

The ratio band is symmetric and targets compositions where TRIS and the alkali salt are within a factor of two by ratio.

Design-around implications

Removing TRIS eliminates claim 5–6 coverage but does not avoid claim 1–4 or 7–10 if the product still sells the same alkali salt.
Using TRIS outside the specified ratio band can avoid claim 6 while still potentially implicating claim 5 (if claim 5 does not include a ratio).
Substituting an alternative buffering agent may avoid TRIS-specific language entirely.

Which alkali metal salts are explicitly covered and how do Na/K/L map to claims?

Direct answer: Sodium, potassium, and lithium are explicitly claimed across both:

the base salt compositions (claims 2–4),
and the TRIS formulation (indirectly through claim 5 and then bounded further by claim 6).

Claim-to-salt mapping table

Salt identity	Claim numbers
Sodium salt	2, 8
Potassium salt	3, 9
Lithium salt	4, 10
Any alkali metal (genus)	1, 5, 7

How many distinct composition inventions are claimed in US 5,210,081?

Direct answer: The claim set effectively covers three clusters:

Alkali metal salts of 8,9-dehydroestrone-3-sulfate ester (genus) (claims 1 and 7),
Cation-identified salts (claims 2–4 and 8–10),
TRIS-buffered compositions with an exclusion of other estrogenic steroids, and a ratio-limited band (claims 5–6).

What “method-of-use” or “process” rights exist in US 5,210,081?

Direct answer: Based on the claims provided, the patent is composition-of-matter only, not a method-of-treatment patent. No process steps are recited in the claim language supplied, so enforceable rights likely focus on manufacture/sale/offer of the claimed compositions rather than therapeutic uses.

What patents typically surround US 5,210,081 in a US steroid-sulfate salt landscape?

Direct answer: In steroid-salt portfolios, adjacent patent families usually cluster around:

alternative salt forms (e.g., ammonium, organic amines, alkaline earth metals),
polymorph/crystal form, hydrate/solvate states,
buffer systems and stabilized formulation compositions,
impurity control and “free from” definitions,
and upstream synthesis routes for the steroid sulfate ester.

However, without a cited claim list or family members beyond US 5,210,081, the landscape scope cannot be exhaustively enumerated here.

What generic entry risks exist for products that sell alkali metal salts of 8,9-dehydroestrone-3-sulfate?

Direct answer: The main generic risk is that a generic applicant or follow-on manufacturer sells an API or drug product that:

contains the same alkali metal salt of the same steroid sulfate ester (claim 1/7),
and, if marketed with TRIS, lands within the claim 5–6 formulation boundaries and maintains “free from other estrogenic steroids.”

Risk matrix by product scenario

Scenario	Likely claim exposure
Same steroid sulfate alkali salt, no TRIS	Claim 1–4, 7, 8–10
Same steroid sulfate alkali salt + TRIS but no ratio match	Claim 5, plus 1–4/7/8–10 depending on cation and exclusion
Same steroid sulfate alkali salt + TRIS within ratio band	Claim 5 and 6, plus salt claims
Non-alkali cation (e.g., Ca salt)	Avoids alkali metal salt claims if not captured elsewhere
Wrong steroid scaffold or different sulfate position/linkage	Avoids claim anchor unless equivalents apply

How do “consisting essentially of” and “free from” affect infringement and validity outcomes?

Direct answer: These phrases both increase claim-interpretation leverage. “Consisting essentially of” adds a materiality threshold for additional components. “Free from” can be forced into an evidentiary framework around purity and impurity testing.

“Consisting essentially of”

Infringement can hinge on whether additional ingredients materially affect the basic and novel characteristics.
If a product includes excipients that do not materially affect the salt’s fundamental properties, a broader construction may keep the claim in play.

“Free from other estrogenic steroids”

Validity and infringement can pivot on whether excluded materials are defined and detected in a way consistent with claim construction.
If the market product includes precursor steroids or related estrogenic steroids as impurities, the exclusion can be contested.

What is the likely expiration profile and exclusivity timeline for US 5,210,081?

Direct answer: A complete expiration and exclusivity timeline requires the patent’s filing date, issue date, term adjustments, and any terminal disclaimers. Those facts are not provided in the input, so a precise date cannot be stated here.

Key Takeaways

US 5,210,081 centers on composition-of-matter rights for alkali metal salts of 8,9-dehydroestrone-3-sulfate ester.
The enforceable scope splits into (i) salt-only compositions (claims 1–4 and 7–10) and (ii) TRIS-containing formulations with a purity exclusion (claims 5–6).
The highest infringement sensitivity is on two formulation facts: which cation and whether the product is “free from other estrogenic steroids.”
A second infringement gate exists for formulation products: TRIS inclusion and the specific ratio range in claim 6.
Generic design-arounds will typically focus on switching (a) salt identity, (b) buffer system, and/or (c) purity/impurity profile relative to “free from” language, while staying outside the defined claim boundaries.

FAQs

1. Does US 5,210,081 cover ammonium salts of 8,9-dehydroestrone-3-sulfate ester?
Based on the provided claims, coverage is limited to alkali metal salts, not ammonium salts.

2. If a product includes TRIS but uses a ratio outside claim 6, is it still within claim 5?
Claim 6 narrows claim 5 by ratio; products outside the ratio band can fall outside claim 6 but may still face claim 5 exposure if TRIS is present and other elements match.

3. What analytical evidence most often determines compliance with “free from other estrogenic steroids”?
Product release and stability analytics tied to detection limits and validated methods for identifying estrogenic steroids.

4. Are sodium/potassium/lithium salts protected even without TRIS?
Yes, dependent claims explicitly cover Na/K/L salts in both general salt and “free from other estrogenic steroids” contexts.

5. Does the patent claim a method of treating a disease?
Not based on the claim text provided. The supplied claims are compositions of matter.

References

US Patent 5,210,081, “Alkali metal salts of 8,9-dehydroestrone-3-sulfate ester,” claims as provided in prompt.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	042262	⤷ Start Trial
Argentina	042345	⤷ Start Trial
Austria	174342	⤷ Start Trial
Austria	342272	⤷ Start Trial
Australia	2007697	⤷ Start Trial
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Details for Patent: 5,210,081

Summary for Patent: 5,210,081