US Patent 4,775,529 covers topical corticosteroid lotions using a defined hydro-alcoholic vehicle containing propylene glycol, isopropyl alcohol, water, a thickener, and an acidic buffer. Its principal commercial relevance was to low-strength lotions containing betamethasone dipropionate, alclometasone dipropionate, or mometasone furoate. The patent issued in 1988 and, under the pre-Uruguay Round patent-term rules applicable to the patent, expired no later than 2005. It therefore presents no current U.S. exclusivity barrier, although its claim structure remains relevant to historical product development and freedom-to-operate analysis.

US Patent 4,775,529 Patent Scope, Claims, Expiration, and Topical Corticosteroid Landscape

What does US Patent 4,775,529 protect?

US Patent 4,775,529 protects a topical lotion and a method of treating inflammation with that lotion. The independent composition claim, claim 1, requires all of the following:

Required element	Claimed range or requirement
Anti-inflammatory corticosteroid	Dermatologically acceptable and present in an inflammation-treating amount
Propylene glycol	15% to 50% by weight
Isopropyl alcohol	20% to 40% by weight
Water	20% to 60% by weight
Thickening agent	0.1% to 3.0% by weight
Buffer	Sufficient to maintain pH at 3.0 to 6.0
Vehicle	Hydro-alcoholic
Composition language	"Consisting essentially of"

The claims are formulation claims rather than claims to a new corticosteroid molecule. The patent does not claim betamethasone dipropionate, alclometasone dipropionate, or mometasone furoate as chemical entities. It claims their use in a particular lotion platform.

The corresponding method claim, claim 13, repeats the same formulation limitations and requires applying the lotion to skin to treat inflammation. Claims 14 through 18 narrow the method by corticosteroid concentration or active ingredient.

How should the phrase "consisting essentially of" be interpreted?

"Consisting essentially of" generally permits additional ingredients that do not materially change the basic and novel characteristics of the claimed composition. The phrase is narrower than "comprising" and broader than "consisting of."

For this patent, the basic formulation characteristics appear to be:

A hydro-alcoholic solvent system based on propylene glycol, isopropyl alcohol, and water.
A thickened lotion suitable for topical application.
An acidic pH between 3.0 and 6.0.
Delivery of an anti-inflammatory corticosteroid.

An accused product containing fragrance, preservatives, chelating agents, antioxidants, or other conventional excipients could still fall within the claim if those ingredients do not materially alter those characteristics. An ingredient that substantially changes the vehicle, pH, rheology, drug release, or topical performance could create a stronger non-infringement position, but the result would depend on claim construction and technical evidence.

What are the concentration limitations in the patent claims?

Claims 1 and 13 establish the broad vehicle ranges. Claims 2 and 14 require the corticosteroid to comprise 0.01% to 1.0% by weight. Claims 3 and 15 narrow the concentration to 0.02% to 0.2%.

The practical claim hierarchy is:

Claim level	Corticosteroid requirement
Claims 1 and 13	Any effective amount
Claims 2 and 14	0.01% to 1.0%
Claims 3 and 15	0.02% to 0.2%
Claim 5	0.064% betamethasone dipropionate
Claim 6	Specific betamethasone dipropionate formula
Claim 8	Specific alclometasone dipropionate formula
Claim 10	Specific mometasone furoate formula

The 0.064% betamethasone dipropionate concentration corresponds to approximately 0.05% active betamethasone per gram because the dipropionate ester has a higher molecular weight than the betamethasone equivalent identified in the claim.

Which corticosteroids are specifically covered?

Betamethasone dipropionate

Claims 4 through 6 cover betamethasone 17,21-dipropionate. Claim 6 identifies a formulation containing:

Ingredient	Amount
Betamethasone dipropionate USP	0.64 mg/g
Propylene glycol	300 mg/g
Isopropyl alcohol	300 mg/g
Hydroxypropyl cellulose	1.50 mg/g
Sodium phosphate monobasic monohydrate	2.00 mg/g
Phosphoric acid and sodium hydroxide	pH adjustment
Purified water	Quantity sufficient

The target pH is 4.5 ± 0.2. This claim is directed to a narrow product configuration and is materially narrower than claim 1.

Alclometasone dipropionate

Claims 7 and 8 cover alclometasone dipropionate. Claim 8 specifies:

Ingredient	Amount
Alclometasone dipropionate	0.5 mg/g
Carbomer 940	2.60 mg/g
Propylene glycol	200 mg/g
Isopropyl alcohol	300 mg/g
Sodium hydroxide	0.04 mg/g
Hydrochloric acid	pH adjustment
Purified water	Quantity sufficient

This example uses an acrylic acid polymer rather than hydroxypropyl cellulose. Claim 11 separately identifies an acrylic acid polymer as the thickener.

Mometasone furoate

Claims 9 and 10 cover mometasone furoate. Claim 10 specifies:

Ingredient	Amount
Mometasone furoate	1.0 mg/g
Isopropyl alcohol	400 mg/g
Propylene glycol	300 mg/g
Hydroxypropyl cellulose	1.50 mg/g
Sodium phosphate monobasic monohydrate	2.0 mg/g
Phosphoric acid	pH adjustment
Purified water	Quantity sufficient

The formulation contains 0.1% mometasone furoate and has a target pH of 4.5 ± 0.1.

What formulations are protected by the patent?

The patent protects a defined formulation architecture rather than a single commercial product. A product is most likely to fall within the broad composition claims when it has:

15% to 50% propylene glycol;
20% to 40% isopropyl alcohol;
20% to 60% water;
0.1% to 3.0% thickener;
pH from 3.0 to 6.0; and
a dermatologically acceptable corticosteroid.

The examples fall within the broad ranges:

Example	Propylene glycol	Isopropyl alcohol	Thickener	Corticosteroid	pH
Betamethasone	30%	30%	0.15% HPC	0.064% betamethasone dipropionate	4.5
Alclometasone	20%	30%	0.26% carbomer 940	0.05% alclometasone dipropionate	4.5
Mometasone	30%	40%	0.15% HPC	0.1% mometasone furoate	4.5

The dependent claims do not require a particular disease. "Inflammation" is broad enough to encompass inflammatory dermatological conditions such as eczema, dermatitis, psoriasis, and related corticosteroid-responsive disorders, subject to the patent's disclosure and applicable claim-construction principles.

When did US Patent 4,775,529 expire?

US Patent 4,775,529 issued on October 4, 1988. Because it was governed by the pre-1995 U.S. patent term rules, its term was generally 17 years from issue rather than 20 years from the earliest effective filing date. On that basis, the patent expired on October 4, 2005, absent an unusual adjustment or extension. The public patent record identifies the patent as expired.[1]

The patent cannot currently block manufacture, sale, or FDA approval of a product that falls within the former claims. Patent expiration does not eliminate the technical relevance of the formulation disclosure, but it removes the patent as an enforceable U.S. exclusivity right.

What was the FDA and Orange Book relevance?

The claim set closely corresponds to topical corticosteroid lotion products, including formulations associated with betamethasone dipropionate and mometasone furoate. FDA approval of a topical corticosteroid lotion is separate from patent protection. A formulation can be FDA-approved without being protected by an unexpired patent, and a patent can cover a formulation that is not currently marketed.

For small-molecule topical products, the principal FDA pathways are:

a new drug application for the reference product;
an abbreviated new drug application for a generic equivalent; and -, in some cases, a suitability petition or other regulatory route depending on dosage form and active ingredient.

The patent is not a biologic patent. Biosimilar provisions under the Biologics Price Competition and Innovation Act do not apply. Generic applicants would typically address any relevant listed patents through the Hatch-Waxman certification process.

Because US Patent 4,775,529 expired in 2005, it should not create a current Orange Book Paragraph IV barrier. Any historical listing would no longer provide an enforceable patent term. Current Orange Book status must be evaluated against the specific reference product, NDA, dosage form, and any later patents.[2]

How would a Paragraph IV challenge have applied?

Before expiration, a generic applicant seeking approval for a product that matched a listed reference formulation could have made a Paragraph IV certification if it concluded that the patent was invalid, unenforceable, or not infringed. The principal non-infringement positions would have included:

Propylene glycol below 15% or above 50%.
Isopropyl alcohol below 20% or above 40%.
Water outside the claimed range.
Thickener below 0.1% or above 3.0%.
pH outside 3.0 to 6.0.
A vehicle that was not materially the claimed hydro-alcoholic base.
A formulation containing no corticosteroid covered by the relevant claim.
A formulation whose additional ingredients materially changed the basic and novel characteristics of the claimed composition.

Potential validity positions would have focused on anticipation, obviousness, indefiniteness, written description, and enablement. The prior-art risk would have been strongest for the broad vehicle ranges and weakest for the narrower combinations tied to specific corticosteroids, thickener systems, and pH conditions. The patent's age and expiration now make those issues historical rather than commercially dispositive.

What patent litigation and settlements affect US Patent 4,775,529?

The supplied patent and claims establish the scope and expiration date, but they do not establish a litigation docket, consent judgment, license, or settlement agreement. The patent's expiration means that any historical litigation cannot produce present-day exclusionary rights under this patent.

A current product review should distinguish this expired patent from:

later formulation patents;
process or manufacturing patents;
crystalline or polymorphic patents;
container or delivery-system patents;
method-of-treatment patents;
regulatory exclusivity; and
patents listed against a specific NDA in the Orange Book.

A settlement involving a generic applicant could have affected launch timing before 2005, but the settlement would not extend the statutory life of US Patent 4,775,529.

How strong is the patent estate for these topical corticosteroid lotions?

The patent estate represented by this patent was commercially meaningful during its term but is now legally weak because the core patent has expired. Its historical strength differed by claim category:

Claim category	Historical scope	Current status
Broad vehicle composition	Broad but dependent on multiple numerical ranges	Expired
Betamethasone formulation	Narrow and commercially specific	Expired
Alclometasone formulation	Narrow, with carbomer-based vehicle	Expired
Mometasone formulation	Narrow, with 0.1% active and HPC vehicle	Expired
Method of treatment	Broadly tied to applying the claimed lotion	Expired
Manufacturing protection	Not expressly claimed in the provided claims	No protection from this patent
Biosimilar protection	Not applicable	Not applicable

The most important continuing barriers are likely to arise from regulatory requirements and formulation performance rather than this patent. A competing product must still demonstrate pharmaceutical equivalence, stability, microbial quality, viscosity, drug content uniformity, topical performance, and any applicable bioequivalence or comparative clinical requirements.

How does this patent compare with current generic entry risks?

For a new generic lotion, US Patent 4,775,529 creates no current launch delay. The principal risks are instead:

whether a later unexpired patent is listed for the reference product;
whether the proposed formulation can meet FDA equivalence requirements;
whether the active ingredient is available in the required pharmaceutical grade;
whether the formulation has adequate stability and preservative performance;
whether the manufacturer can reproduce the viscosity and drug-release profile; and
whether the product is marketed for an approved indication.

The formulation itself is relatively conventional: glycols, alcohol, water, a cellulose or acrylic thickener, and acidic buffering. The technical challenge is reproducibility and regulatory equivalence, not access to the expired formulation concept.

What geographic coverage did the patent provide?

US Patent 4,775,529 provided protection only in the United States. It did not create rights in Europe, Canada, Japan, or other jurisdictions. Foreign counterparts, if any, would require separate review by publication number, national phase, assignee, filing date, and expiration status.

The U.S. patent also did not automatically protect manufacturing conducted abroad unless an infringing act occurred within the territorial reach of U.S. law, such as importation of a covered product into the United States.

Key Takeaways

US Patent 4,775,529 claims topical corticosteroid lotions with defined propylene glycol, isopropyl alcohol, water, thickener, and pH ranges.
The patent specifically covers betamethasone dipropionate, alclometasone dipropionate, and mometasone furoate formulations.
The broadest claims require a hydro-alcoholic vehicle, 0.1% to 3.0% thickener, and pH of 3.0 to 6.0.
The patent issued on October 4, 1988, and expired on October 4, 2005, under the applicable pre-1995 patent-term rules.
It creates no current U.S. patent barrier to generic or competing topical corticosteroid lotions.
Biosimilar law is irrelevant because the products are small-molecule corticosteroids.
Current commercial risk must be assessed against later patents, Orange Book listings, FDA requirements, and formulation equivalence standards.

FAQs

Can a generic company use the exact formulation in claim 6 today?

Yes, the patent's expiration removes its enforceable exclusivity. Other unexpired patents or regulatory requirements could still apply to the specific reference product.

Does the patent cover a lotion with ethanol instead of isopropyl alcohol?

The provided claims require isopropyl alcohol. A formulation using ethanol would not literally satisfy that limitation, although other patents or an infringement theory based on equivalents would require separate analysis.

Does a pH of 6.5 avoid the main composition claims?

A pH of 6.5 is outside the express 3.0 to 6.0 limitation. It would avoid literal infringement of the provided composition claims, subject to analysis of other claims and any doctrine-of-equivalents argument.

Is a cream or ointment covered by US Patent 4,775,529?

The claims are directed to a topical lotion in a hydro-alcoholic base. A conventional cream or ointment would generally have a different dosage-form structure and would not automatically satisfy the claimed limitations.

Does the patent protect the use of hydroxypropyl cellulose by itself?

No. Claim 12 identifies hydroxypropyl cellulose as the thickener, but the claim also requires the other composition limitations inherited from claim 1, including the solvent ranges and pH range.

References

United States Patent and Trademark Office. (1988). Topical corticosteroid compositions, U.S. Patent No. 4,775,529.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
U.S. Food and Drug Administration. (n.d.). Approved drug product labeling and topical corticosteroid products. Drugs@FDA. https://www.accessdata.fda.gov/scripts/cder/daf/
United States Code. (1988). 35 U.S.C. § 154, patent term provisions applicable to patents issued before the 1995 term amendments.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	77745	⤷ Start Trial
Australia	1941788	⤷ Start Trial
Australia	616188	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,775,529

Summary for Patent: 4,775,529