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United States Patent 8,492,438 Claims Analysis and U.S. Patent Landscape

Executive summary: US 8,492,438 covers broad, method-of-treatment claims for multiple skin disorders (including rosacea and rosacea-associated lesions) using a composition that contains a histone hyperacetylating agent from a long, enumerated chemical list, delivered in a cosmetically or pharmaceutically acceptable carrier. Dependent claims narrow to topical use and to specific histone hyperacetylators, but the overall claim architecture is expansive: it is not limited to a single active ingredient, formulation type beyond “carrier,” or a single mechanism beyond “histone hyperacetylating agent.” The estate’s practical value depends on (i) how tightly the specification links each named agent to the claimed skin disorders and (ii) whether separate patents exist for key actives and topical delivery systems that could block or invalidate variations through obviousness, lack of written description, or lack of enablement.

What does US Patent 8,492,438 claim and how broad is the coverage?

Core claim (Claim 1) is a method-of-treatment with a highly expansive active-ingredient genus-by-enumeration. It requires:

A method treating a skin disorder by administering a composition to a subject.
“Composition containing an effective amount of a histone hyperacetylating agent” plus a cosmetically or pharmaceutically acceptable carrier.
Skin disorder scope: rosacea; pityriasis rosea; erythema; rhinophyma; and “a rosacea-associated disorder that is pimple, papule, pustule, or telangiectasia.”
Active-ingredient scope: a long list of histone hyperacetylating agents and salts (HDAC inhibitors and related agents by function), including:
- Trichostatin A / Trichostatin C
- Oxamflatin
- Trapoxin A
- FR901228
- Apicidin
- HC-Toxin
- WF27082
- Chlamydocin
- Hydroxamic acids and derivatives (including salicylihydroxamic acid, suberoylanilide hydroxamic acid, azelaic bishydroxamic acid, azelaic-1-hydroxamate-9-an-ilide)
- Carboxamide/hydroxamate series (M-carboxycinnamic acid bishydroxamide; 6-(3-chlorophenylureido) carpoic hydroxamic acid; MW2796; MW2996)
- Short-chain fatty acids / prodrug-like analogs (sodium butyrate, arginine butyrate, isovalerate, valerate, 4-phenylbutyrate, propionate, butyramide, isobutyramide, phenylacetate, 3-bromopropionate)
- Valproate / valproic acid
- Tributyrin
- MS-27-275 and 3′-amino derivatives
- Depudecin
- Scriptaid

Breadth characterization (practical infringement exposure):

Target indication breadth: multiple dermatology endpoints, with rosacea and rosacea-associated lesions explicitly anchored.
Active ingredient breadth: no single active is required; any of the enumerated hyperacetylators can satisfy claim 1.
Dosage form breadth: claim 1 does not limit to topical; dependent claims do.
Delivery and formulation breadth: “composition” + “carrier” is permissive; dependent claim 10 lists many dosage forms as possible topical or other delivery vehicles.

Claim 2-10: How much do dependent claims reduce risk?

Claim 2 limits to topical composition.
Claims 3-9 carve the active list into subsets but still remain inclusive and broad.
Claim 10 expands dosage form possibilities (cream, ointment, gel, lotion, patch, liposome, nanocapsule, etc.) via permissive “wherein the composition is …”

Key legal consequence: If a product matches Claim 1’s elements, Claim 2 and later dependents create additional narrower infringement lanes. But the broad independent claim makes design-around harder: many topical formulations using listed actives can still land within Claim 1 if the claim is read without a topical requirement (subject to claim-construction specifics).

Which skin disorders are explicitly covered by US 8,492,438?

Covered disorders (explicit):

Rosacea
Pityriasis rosea
Erythema
Rhinophyma
Rosacea-associated disorder defined by lesions:
- pimple
- papule
- pustule
- telangiectasia

Critical interpretation points:

The phrase “rosacea-associated disorder” plus lesion types suggests the claim targets rosacea sub-phenotypes commonly used in clinical practice (papules/pustules/telangiectasia), not just rosacea as a disease label.
By listing multiple dermatology conditions, the claim reduces exclusivity tied to a single indication, increasing enforcement leverage against dermatology formulators using HDAC inhibitors.

What histone hyperacetylating agents are enumerated and how does that shape the patent’s strength?

Enumerated agents include:

Macrocyclic/peptide-like HDAC inhibitors: trichostatin A, apicidin, trapoxin A, oxamflatin, FR901228, HC-Toxin, WF27082, chlamydocin
Hydroxamate HDAC inhibitors: salicylihydroxamic acid, suberoylanilide hydroxamic acid (SAHA-like), azelaic bishydroxamic acid, azelaic-1-hydroxamate-9-an-ilide
Carboxylic acid/hydroxamate analogs: M-carboxycinnamic acid bishydroxamide, 6-(3-chlorophenylureido) carpoic hydroxamic acid, MW2796, MW2996
Short-chain fatty acids and derivatives (HDAC inhibition by hyperacetylation function): sodium butyrate, arginine butyrate, isovalerate, valerate, 4-phenylbutyrate, propionate, butyramide, isobutyramide, phenylacetate, 3-bromopropionate, tributyrin
Valproate family: valproic acid, valproate
Other named hyperacetylators: MS-27-275 (and 3′-amino derivatives), depudecin, scriptaid

Critical issue: enumeration vs genus claim

The claim is not written as “any histone hyperacetylating agent.” It is “selected from the group consisting of” many named agents. That can be favorable for enforceability in one respect (clear mapping for listed actives), but it also means:

A competitor using an unlisted HDAC inhibitor may avoid direct literal infringement of Claim 1.
A competitor using one of the listed actives may not avoid simply by switching formulation type, because carrier and dosage forms are permissive.

What are the formulation and topical delivery claims inside US 8,492,438?

What does the patent allow on dosage forms?

Claim 10 lists a broad set of formulations and routes consistent with dermatology and local delivery:

Cream, ointment, gel, paste
Powder, aqueous solution, spray, suspension, dispersion
Salve, lotion
Patch
Suppository, liposome formulation, mouth wash, enema, eye drop, ear drop
Microcapsule, nanocapsule

Practical consequence: design-arounds by switching between semi-solids (cream/gel) and particulate systems (liposomes, nanocapsules) are unlikely to escape if the active ingredient is one of the listed hyperacetylators and the use is within the claimed skin disorder scope.

What about combination therapy?

Claim 11 expands into combination regimens with an extremely broad set of second agents: cytokines, interleukins, growth factors, vasoactive agents, antibodies, receptor agonists, anti-inflammatory agents (non-steroid and steroid), anti-oxidants, vitamins, mast cell inhibitors, anti-IgE, lidocaine, epinephrine, serotonin pathway drugs, antibiotics, calcineurin inhibitor, DNA methylation inhibitors, collagenase, and combinations.

Claim 12 allows simultaneous or separate topical administration.

Practical consequence: If a challenger formulates with one of the listed “second agents,” the combination lane becomes harder to attack on scope grounds.

How does US 8,492,438 compare with other HDAC-inhibitor dermatology patent estates?

Without an external dataset of cited references, litigation filings, and Orange Book/NDA pairing, the most reliable comparison is claim-architecture-based.

Common HDAC dermatology patent patterns:

Method-of-treatment claims tied to specific actives.
Formulation-specific claims (vehicle, penetration enhancers, microencapsulation, liposomes).
Use claims tied to particular dermatoses (acne/rosacea/psoriasis-like syndromes).

US 8,492,438 is unusual in one key way: it pairs broad disease scope with a long, enumerated list of hyperacetylating agents and adds a wide list of formulation types via dependent claims.

Competitive implication: Companies developing topical HDAC inhibitors for rosacea with one of the enumerated agents face a larger claim-overlap surface area than with patents that are narrower to one active or one formulation.

When does US 8,492,438 expire and what exclusivity stack matters?

This analysis requires the actual patent bibliographic data (filing date, priority date, term adjustments, and any PTA) to calculate legal expiration. That information is not provided in the prompt and cannot be derived from the claim text alone.

Result: No accurate exclusivity timeline can be produced from the provided content.

What generic entry risks exist for topical rosacea HDAC inhibitors under US 8,492,438?

Because US 8,492,438 is a method-of-treatment patent, the “generic entry risk” is best understood as label/use infringement risk, not FDA “Orange Book generic” mechanics in isolation.

Where risk concentrates:

If a generic or follow-on product uses an enumerated histone hyperacetylating agent and is indicated/used for rosacea or one of the other named skin disorders, the product can potentially trigger infringement even if the formulation differs.
If the claimed invention is enforced as part of a settlement with a licensed generic/follow-on, commercial decisions depend on what use is permitted post-launch.

Where risk reduces:

Products using unlisted hyperacetylating agents may reduce direct literal infringement risk.
Products that avoid treating the enumerated skin disorders, or that structure labeling and promotional activities to avoid the claimed conditions, may reduce use-based exposure.

What Paragraph IV, Hatch-Waxman, or biosimilar analogs apply?

This patent is not framed as an NDA “active ingredient” patent. It is a method-of-use patent. For generic entry, the key analog risk is whether the relevant reference product includes a method of use that aligns with the claims and whether litigation centers on infringement of “use” rather than “composition.”

No complete and accurate answer can be given without the identity of the related branded reference product, its NDA/ANDA portfolio, and the listing status of US 8,492,438 in FDA systems.

Which companies are likely relevant to US 8,492,438 enforcement?

The prompt does not identify the assignee, inventor(s), prosecution history, or known parties in related litigation. Those data are required to name likely challengers or licensees.

Result: No company-specific landscape can be produced from the provided content.

Key vulnerability analysis: where invalidity arguments typically target broad dermatology method claims

Even without the specification text, broad method claims with expansive active lists are commonly attacked on specific validity fronts:

Written description / enablement mismatch
- If the specification does not provide enabling guidance across the entire enumerated list (multiple chemotypes) and across multiple skin disorders, an invalidity challenge can argue non-enablement or lack of adequate disclosure for the full scope.
Indefiniteness risk around functional limitation
- The claim uses “histone hyperacetylating agent” and enumerates compounds. Functional definition disputes can arise if prosecution relied on a broad functional interpretation rather than specific demonstrated hyperacetylation.
Obviousness over HDAC inhibitors + dermatology indications
- Prior art HDAC inhibitors are known in multiple therapeutic areas; invalidity typically frames the claim as an obvious extension into rosacea/erythema/rhinophyma using predictable topical delivery and known pharmacology.
Lack of specific nexus to rosacea lesions
- The claim includes lesion-level definitions (pimple/papule/pustule/telangiectasia). Without disorder-specific evidence, arguments can target whether the disclosure supports treatment of those defined phenotypes, not merely rosacea generally.

These arguments can be strong or weak depending on the specification, examples, and experimental results used in prosecution, none of which are provided.

Claim chart snapshot: infringement mapping for a topical rosacea product

A product is likely to face the strongest infringement test when it satisfies all elements of an asserted claim set (independent and dependent):

Claim element	What must be present	In a rosacea topical scenario
Method treating a skin disorder	Rosacea / pityriasis rosea / erythema / rhinophyma / rosacea-associated pimple/papule/pustule/telangiectasia	Indication, labeling claims, or actual clinical use matching the listed conditions
Administering a composition	Subject receives a composition with an effective amount	Topical dosing regimen delivering active to skin
Histone hyperacetylating agent	Active is one of the enumerated agents (or salt)	Product ingredient must be on the list
Carrier	“cosmetically or pharmaceutically acceptable carrier”	Typical topical vehicle likely meets this broadly
Topical limitation (if Claim 2 asserted)	Composition is topical	Most derm products qualify
Formulation type (if Claim 10 asserted)	Match any listed dosage form	Cream/gel/liposome/nanocapsule all potentially map

Key Takeaways

US 8,492,438 is an expansive method-of-treatment patent covering multiple dermatologic conditions, anchored strongly around rosacea and rosacea-associated lesions.
The active-ingredient scope is very broad but bounded by enumeration: infringement risk is high for products using the listed hyperacetylating agents, even if formulation and delivery system differ.
Topical delivery and diverse dosage forms are explicitly contemplated, making “vehicle-only” design-arounds less effective.
Combination therapy claims are also broad, expanding enforcement leverage against multi-agent rosacea regimens.
The patent’s enforceability and defensibility turn on specification support and prosecution record for the entire enumerated set of actives and the defined skin disorders.

FAQs

1) Does US 8,492,438 cover any histone hyperacetylating agent or only the enumerated list?

Only agents “selected from the group consisting of” the enumerated hyperacetylating compounds (and pharmaceutically acceptable salts) fit Claim 1 as written.

2) Is topical use required to infringe US 8,492,438?

Claim 1 does not require topical use; Claim 2 and later dependents do. A topical product can still implicate Claim 1 depending on claim construction of “administering” and “composition” scope.

3) Can a different dosage form avoid infringement under US 8,492,438?

Not if the active is on the enumerated list and the use matches the claimed disorder scope. Claim 10 lists many dosage forms, including advanced delivery systems.

4) What rosacea sub-features are named in the claims?

The claims explicitly include rosacea-associated disorders characterized as pimple, papule, pustule, or telangiectasia.

5) How do combination therapies change exposure under this patent?

Claim 11 adds a second-agent combination framework with many biologics, small molecules, and anti-inflammatory classes, and Claim 12 allows simultaneous or separate topical administration.

References

User-provided claim text for United States Patent 8,492,438 (Claims 1-19).

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Smith & Nephew, Inc.	SANTYL	collagenase	Ointment	101995	June 04, 1965	8,492,438	2031-02-04
Jubilant Hollisterstier Llc	N/A	positive skin test control-histamine	Injection	103891	March 13, 1924	8,492,438	2031-02-04
Auxilium Pharmaceuticals, Inc.	XIAFLEX	collagenase clostridium histolyticum	For Injection	125338	February 02, 2010	8,492,438	2031-02-04
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Patent: 8,492,438

Summary for Patent: 8,492,438