United States Patent 4,996,335: Claim Scope, Loteprednol Etabonate Coverage, Expiration, and Patent Landscape

US 4,996,335 is a broad corticosteroid compound patent covering 17-carboxylic acid derivatives, esterified and salt forms, pharmaceutical compositions, and topical anti-inflammatory methods. Its most commercially important disclosed compound is loteprednol etabonate, the active ingredient in Lotemax and related ophthalmic products. The patent issued February 26, 1991, and its ordinary 17-year patent term expired in 2008, subject to any applicable patent-term adjustment or extension. It is no longer a primary U.S. blocking patent for generic loteprednol etabonate.

What drug does US 4,996,335 protect?

US 4,996,335 covers a family of “soft” corticosteroid derivatives designed to provide local anti-inflammatory activity while permitting hydrolytic metabolism to inactive products. The central chemical structure is a corticosteroid nucleus bearing:

A 17β-carboxylic acid or ester group.
A 17α-carbonyloxy substituent.
An 11β-hydroxyl group or related oxidation state.
Optional 9α-fluoro, 16α-methyl, 16β-methyl, and related substitutions.
A saturated or unsaturated 1,2 bond.
Optional 3-keto, 3,11-diketo, or related steroid functionality.

The patent’s commercial significance comes from claim 69, which recites:

chloromethyl 17α-ethoxycarbonyloxy-11β-hydroxyandrosta-1,4-dien-3-one-17β-carboxylate.

That compound is loteprednol etabonate. Its common chemical description is chloromethyl 17α-ethoxycarbonyloxy-11β-hydroxy-3-oxoandrosta-1,4-diene-17β-carboxylate.

Patent claim	Commercial relevance
Claims 1-2	Broad genus claims covering steroidal 17-carboxylate derivatives
Claims 3-9	Structural subclasses corresponding to named formula types
Claims 10-60	Narrower substituent, stereochemical, halogen, ester, salt, and ring-substitution combinations
Claims 61-87	Individually identified chemical compounds
Claim 69	Loteprednol etabonate
Claims 88-90	Topical or local pharmaceutical compositions and anti-inflammatory methods
Claims 91-103	Fluoromethyl and related later-added compound classes
Claims 104-113	Further structural subgenera and specific substituent combinations

How broad are the independent chemical claims?

Claim 1: broad genus coverage

Claim 1 covers compounds of formula I and several related formula classes. It allows extensive variation at R1 and R2, including:

Alkyl, hydroxyalkyl, haloalkyl, alkenyl, cycloalkyl, cycloalkenyl and aryl groups.
Ester-linked groups such as -CH2COOR6.
Amide-linked groups such as -CH2CONR7R8.
Thioether, sulfoxide, sulfone and ether substituents.
Phenyl, benzyl and substituted phenyl or benzyl groups.
Heterocyclic amine residues, including morpholino, piperidino, piperazinyl and pyrrolidinyl groups.
Cyclic thioether, sulfoxide, sulfone and ether systems.

The steroid nucleus is also broad. R3 may be hydrogen, hydroxy, methyl, methylene or another steroid substituent. R4 and R5 may be hydrogen, fluoro, chloro or methyl. X may be oxygen or sulfur, and the A-ring 1,2 bond may be saturated or unsaturated.

This claim is a Markush genus. It is potentially wide on its face, but its enforceable scope depends on written-description support, enablement, claim construction, prosecution history and the relationship between the generic language and the disclosed examples.

Claim 2: narrowed genus

Claim 2 reduces many substituent ranges to C1-C6 groups and limits selected positions to oxygen-containing structures. It is materially narrower than claim 1 but still covers a large number of compounds.

The claim specifically includes:

C1-C6 alkyl and haloalkyl groups.
Cycloalkyl, phenyl and benzyl groups.
Fluoro-substituted steroid structures.
Ester, ether, thioether, sulfoxide and sulfone derivatives.
The same broad set of formula classes and salts.

Claims 3-60 then narrow the genus through dependent limitations. These claims are important for validity analysis because they identify commercially plausible subfamilies and provide fallback positions if the broadest Markush claims are challenged.

Which claim covers loteprednol etabonate?

Claim 69 is the direct compound claim for loteprednol etabonate. The compound has the following relevant features:

Loteprednol etabonate feature	Claim 69 limitation
Chloromethyl 17β-carboxylate	Present
17α-ethoxycarbonyloxy group	Present
11β-hydroxyl group	Present
Androsta-1,4-diene nucleus	Present
3-one group	Present
17β-carboxylate	Present

Claims 1, 2, 3, 5, 11, 26 and related dependent claims also appear to reach loteprednol etabonate through broader structural definitions. Claim 69 is the most commercially direct claim because it names the exact compound rather than relying on a genus construction.

Claims 88-90 potentially cover use of loteprednol etabonate in topical or local anti-inflammatory pharmaceutical compositions. They do not expressly recite an ophthalmic indication. The phrase “topical or other local application” is broad enough to encompass ophthalmic, dermatological and other local formulations, subject to claim construction and prosecution history.

What formulations are protected by US 4,996,335?

The patent claims pharmaceutical compositions containing a compound of formula I with a pharmaceutically acceptable carrier. Claim 88 covers:

An anti-inflammatory effective amount.
A compound having structural formula I.
A non-toxic pharmaceutically acceptable carrier.
Topical or other local application.

The claim is not limited to a particular:

Concentration.
Preservative system.
Viscosity.
Particle size.
Suspension vehicle.
Emulsion system.
Gel structure.
Ophthalmic container.
Dosing schedule.
Sterility process.

The formulation claims therefore reach compositions containing the claimed active compound, but they do not necessarily cover later-developed formulation technology that uses a different active ingredient form, a distinct delivery architecture, or a separately claimed excipient system.

The patent does not appear, from the supplied claims, to claim specific suspension, gel, ointment, nanoparticle, emulsion, preservative-free or controlled-release formulation technology. Those technologies would generally require separate formulation claims.

What methods of use are covered?

Claims 89 and 90 cover methods for alleviating inflammation in a warm-blooded animal by administering an anti-inflammatory effective amount of the claimed composition.

Claim	Method scope
Claim 89	Topical administration for a topical inflammatory response
Claim 90	Local administration for a localized inflammatory response

The method claims are broad and functional. They do not identify a particular disease, anatomical site, treatment duration or dosage regimen. They could reach local treatment of ocular, dermatologic or other localized inflammatory conditions if the other claim elements are satisfied.

The absence of a disease-specific limitation reduces the value of these claims as differentiated regulatory exclusivity assets. Their practical enforceability would depend on the compound, composition, route and accused use meeting the claim language.

When did US 4,996,335 lose exclusivity?

US 4,996,335 issued on February 26, 1991. For a pre-June 8, 1995 application, the ordinary term generally was the longer of 17 years from grant or 20 years from the earliest effective U.S. nonprovisional filing date under the transitional patent-term rules. The patent’s ordinary 17-year term therefore ran to approximately February 26, 2008, absent an applicable extension or adjustment.

Event	Date or period
U.S. patent grant	February 26, 1991
Ordinary 17-year term from grant	Approximately February 26, 2008
Likely blocking status today	Expired
Current generic relevance	Historical compound and method patent, not a live primary barrier

The patent is not a current source of patent exclusivity for loteprednol etabonate. FDA regulatory exclusivity and later formulation patents must be analyzed separately from the expired compound patent.

What is the Orange Book status of the patent?

US 4,996,335 should not be treated as a current Orange Book barrier solely because it covers the active compound. Orange Book listing is product-specific and depends on whether an approved NDA holder submitted the patent for a qualifying drug substance, drug product or method-of-use claim.

For loteprednol products, the relevant regulatory products include:

Lotemax ophthalmic suspension.
Lotemax gel.
Lotemax SM ophthalmic gel.
Alrex ophthalmic suspension.
Generic loteprednol etabonate ophthalmic products.

The FDA Orange Book must be reviewed by NDA and dosage form. A patent may be historically associated with an innovator product yet no longer provide enforceable exclusivity because it expired or because the listing was removed. The expired status of US 4,996,335 means it cannot ordinarily support a current Paragraph IV litigation strategy against a generic applicant.

FDA approval of generic loteprednol products confirms that the active ingredient itself is no longer protected by an enforceable patent monopoly. See FDA, Approved Drug Products with Therapeutic Equivalence Evaluations, and FDA product labeling for Lotemax and Alrex.

Which compounds besides loteprednol etabonate are claimed?

Claims 61-87 and 101-103 identify a wide range of compounds. The principal variables include:

Chloromethyl versus fluoromethyl or other haloalkyl ester groups.
Methoxycarbonyloxy, ethoxycarbonyloxy, propoxycarbonyloxy, isopropoxycarbonyloxy, butoxycarbonyloxy and pentyloxycarbonyloxy groups.
9α-fluoro substitution.
16α-methyl and 16β-methyl substitution.
Androst-4-en-3-one versus androsta-1,4-dien-3-one systems.
11β-hydroxy versus 3,11-diketo structures.
Free carboxylic acids and sodium salts.

Examples include:

Claim	Compound class
Claims 61-64	Nonfluorinated chloromethyl corticosteroid 17-carboxylates
Claims 65-76	Fluorinated and methyl-substituted steroid esters
Claims 77-78	Fluoromethyl and 2-chloroethoxycarbonyl derivatives
Claims 79-83	Free steroid 17β-carboxylic acids
Claim 84	Sodium carboxylate salts
Claims 85-87	Chlorocarbonyloxy and 3,11-diketo derivatives
Claims 101-103	Fluoromethyl analogues

The named examples provide narrower, compound-specific fallback claims. A competitor that avoids loteprednol etabonate but uses a close analogue could still face risk under the broad genus claims, depending on the exact structure and claim construction.

How strong is the patent estate?

The patent estate was strongest against direct manufacture, sale or use of loteprednol etabonate during its term. Its key strengths were:

A direct compound claim to loteprednol etabonate.
Broad genus claims covering structurally related corticosteroid derivatives.
Composition claims directed to topical and local anti-inflammatory products.
Method claims that were not limited to one disease or anatomical site.
Multiple dependent claims providing narrower structural positions.

Its principal limitations were:

The patent has expired.
The claims do not, on their face, provide detailed protection for modern ophthalmic formulation systems.
The broad Markush claims could face written-description, enablement, anticipation or obviousness challenges.
The method claims depend on proving the claimed composition and administration elements.
Product-specific Orange Book protection would have required a qualifying listing and would not automatically extend to every later loteprednol formulation.

The estate should therefore be rated as historically strong for the active compound and presently weak as a blocking right.

What patent litigation and Paragraph IV risks exist?

During the patent’s enforceable period, an ANDA applicant seeking approval for loteprednol etabonate could have filed a Paragraph IV certification alleging that US 4,996,335 was invalid, unenforceable or would not be infringed. A Paragraph IV notice could have triggered a patent-infringement action under 35 U.S.C. §271(e)(2) and potentially a 30-month stay under the Hatch-Waxman framework.

That risk is now principally historical because the patent expired in 2008. Current generic challenges would focus on:

Later formulation patents.
Gel, suspension, emulsion or preservative-free delivery claims.
Method-of-use claims for particular indications.
Product-specific patents listed for individual Lotemax, Alrex or related NDAs.
Regulatory exclusivity that is independent of patent term.

No current litigation conclusion can be drawn from US 4,996,335 alone. The patent number does not establish that a present ANDA dispute exists, that a Paragraph IV notice was filed, or that a settlement agreement remains operative.

How does US 4,996,335 compare with later loteprednol patent protection?

Protection layer	Subject matter	Status relative to US 4,996,335
Core compound patent	Loteprednol etabonate and analogues	US 4,996,335; expired
Formulation patents	Suspensions, gels, emulsions, particle systems and excipients	Potentially later-expiring; product-specific review required
Method-of-use patents	Treatment of ocular inflammation or defined conditions	May have separate terms and claim limitations
Regulatory exclusivity	NDA-based FDA exclusivity	Separate from patent term
Manufacturing patents	Synthesis, purification, crystallization or process controls	May create independent commercial barriers
Trade secrets	Process parameters, scale-up and quality controls	Not listed in the Orange Book and may persist indefinitely

The competitive landscape therefore shifted from compound protection to formulation, manufacturing, regulatory and commercial execution. Generic products can use the same active compound after core patent expiration but may still need to design around live formulation or method claims.

What generic launch scenarios exist?

Immediate active-ingredient substitution

A generic applicant can rely on the expired compound patent landscape and seek approval for a therapeutically equivalent loteprednol etabonate product. The main requirements are pharmaceutical equivalence, bioequivalence or applicable ophthalmic equivalence standards, manufacturing compliance and labeling conformity.

Formulation design-around

A generic may avoid later formulation claims by using a different:

Vehicle.
Preservative system.
Particle-size distribution.
Gel-forming polymer.
Container or delivery system.
Manufacturing process.

Paragraph III or no-certification pathway

If no unexpired Orange Book patent blocks the product, the applicant may proceed without a Paragraph IV challenge to US 4,996,335. If later patents are listed, the applicant may use Paragraph III, Paragraph IV, or a section viii statement depending on the claims and proposed labeling.

Product-specific risk

The main present risk is not infringement of the expired compound patent. It is infringement of a live patent covering the particular dosage form, formulation, manufacturing process or labeled use.

What manufacturing and geographic barriers remain?

US 4,996,335 is a U.S. patent and its territorial rights were limited to the United States. Parallel foreign applications may have produced separate rights, but U.S. expiration does not establish the status of corresponding patents in Europe, Canada, Japan, China or other markets.

Manufacturing barriers may remain where later patents cover:

Selective esterification at the 17-position.
Haloalkyl ester formation.
Impurity control.
Crystallization or polymorph management.
Sterile ophthalmic processing.
Suspension stability.
Gel manufacturing.
Container-closure systems.

A generic manufacturer can avoid the expired patent while still encountering live foreign rights, process patents, regulatory barriers or trade-secret constraints.

Key Takeaways

US 4,996,335 is a broad corticosteroid compound patent centered on 17-carboxylate derivatives.
Claim 69 directly covers loteprednol etabonate.
Claims 88-90 cover topical or local anti-inflammatory compositions and methods.
The patent issued February 26, 1991, and its ordinary term expired approximately February 26, 2008.
The patent is no longer a primary U.S. barrier to generic loteprednol etabonate.
Current competitive risk is more likely to arise from later formulation, method-of-use, manufacturing or product-specific patents.
Orange Book status must be assessed by NDA and dosage form, not by the existence of the historical compound patent alone.
The patent has substantial historical scope but limited current blocking value.

Frequently Asked Questions

Does US 4,996,335 cover Lotemax?

Yes. Claim 69 directly covers loteprednol etabonate, the active ingredient in Lotemax products.

Is US 4,996,335 still enforceable?

Its ordinary U.S. patent term expired approximately in 2008. It should not be treated as an enforceable current compound patent absent an unusual term adjustment or extension.

Does the patent cover ophthalmic formulations?

Claims 88-90 broadly cover pharmaceutical compositions for topical or local anti-inflammatory use. They do not specifically claim every modern ophthalmic suspension, gel or delivery system.

Can a generic use the same loteprednol etabonate molecule?

Yes, subject to FDA approval requirements and any separate unexpired patents covering the proposed formulation, labeled use or manufacturing process.

Does expiration of this patent eliminate all loteprednol patent risk?

No. Later formulation, method-of-use, manufacturing and product-specific patents may create separate risks even after the core compound patent expires.

References

United States Patent No. 4,996,335. (1991). 17-carboxylic acid esters of corticosteroids. U.S. Patent and Trademark Office.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
U.S. Food and Drug Administration. (2024). Lotemax (loteprednol etabonate ophthalmic suspension) prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Alrex (loteprednol etabonate ophthalmic suspension) prescribing information. FDA.
Patent Act, 35 U.S.C. §§ 154, 271(e)(2), 271(e)(4) (2024).
Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	379816	⤷ Start Trial
Austria	379817	⤷ Start Trial
Austria	A265684	⤷ Start Trial
Austria	A307081	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,996,335

Summary for Patent: 4,996,335