United States Patent 5,990,100: Claim Scope, Expiration, and Psoriasis Formulation Patent Landscape

U.S. Patent No. 5,990,100 covers liquid topical psoriasis compositions and treatment methods that combine an anti-psoriatic agent with a high concentration of isopropyl myristate (IPM). The core independent claims require: an anti-psoriatic agent, 15 to 97 weight percent IPM, a liquid topical dosage form, and use in treating psoriasis. The patent’s practical scope is concentrated in IPM-rich vehicles containing corticosteroids, calcipotriol, retinoids, or tar.

The patent is an old small-molecule formulation patent. Its statutory term has expired, or at minimum reached its ordinary term no later than the late 2010s, subject to any patent-term adjustment or other recorded term event. It therefore does not present a current U.S. blocking patent risk based on the claims provided. The principal commercial relevance is historical: the patent illustrates a vehicle-based formulation strategy rather than a claim to a new anti-psoriatic active ingredient.

What does U.S. Patent 5,990,100 protect?

The patent protects two related categories:

Liquid topical pharmaceutical compositions containing IPM and a specified anti-psoriatic agent.
Methods of treating psoriasis by topically administering those compositions to a human.

The broadest composition claim is claim 1. It requires all of the following:

Required element	Claim 1 requirement
Therapeutic indication	Treatment of psoriasis
Active ingredient	Corticosteroid, calcipotriol, retinoid, tar, or mixture
Active concentration	0.0001 to 30 weight percent
Vehicle	15 to 97 weight percent IPM
Dosage form	Liquid
Route and population	Topical administration to a human
Functional limitation	Active present in an effective anti-psoriatic amount

The claim is not directed to IPM generally. It requires IPM at a substantial concentration and requires the composition to contain one of the listed anti-psoriatic classes.

Claim 7 is the corresponding independent method claim. It requires topical administration to a human with psoriasis of a composition meeting substantially the same active, IPM, concentration, and liquid-form limitations.

How broad is the independent composition claim?

Claim 1 is compositionally broad but technically constrained.

It covers:

Low concentrations of active ingredient, down to 0.0001 weight percent.
IPM concentrations from 15 to 97 weight percent.
Multiple active classes.
Mixtures of listed anti-psoriatic agents.
Any liquid topical human dosage form meeting the stated concentration ranges.

It does not expressly require:

A particular corticosteroid.
A particular retinoid.
A surfactant.
Water or alcohol.
A particular pH.
A specific container or delivery device.
A particular viscosity.
A particular commercial product.
A named formulation such as a cream, ointment, foam, gel, lotion, spray, or solution, although the claim requires a liquid suitable for topical administration.

The term “effective anti-psoriatic weight percent” introduces a functional requirement. A composition containing a listed active at a nominal concentration could fall outside the claim if it is not present in an amount effective for the claimed therapeutic purpose. Conversely, the unusually broad lower concentration range may capture very dilute formulations when the functional limitation is satisfied.

What formulations are protected by the dependent claims?

The dependent claims narrow the IPM level, solvent system, active concentration, or formulation ingredients.

IPM concentration ranges

Claims	IPM limitation
1, 7	15 to 97 wt%
2, 9, 16, 18, 26, 27, 32, 33	At least 25 wt% or more specific dependent limitation
3, 27	At least 40 wt%
4, 6, 12, 30	38 to 60 wt%
5, 10, 29	At least 38 wt%
20, 28	30 to 55 wt% or 30 to 60 wt%
31	At least 35 wt%

The most commercially specific formulation cluster is claims 6 and 12, which require:

38 to 60 weight percent IPM;
1.5 to 10 weight percent water; and
35 to 60 weight percent ethanol.

Because those ranges can overlap numerically, the percentages must be read as composition constraints subject to the total composition equaling 100 weight percent and any additional ingredients permitted by the claim.

Active-agent limitations

Claims 8 through 18 and claims 31 through 33 narrow the active ingredient:

Corticosteroid at 0.001 to 5 weight percent.
Corticosteroid other than hydrocortisone.
Calcipotriol at 0.0001 to 0.1 weight percent.
General anti-psoriatic agent at 0.005 to 10 weight percent.

The calcipotriol claims are particularly narrow in active concentration but remain broad as to the precise liquid vehicle, provided that the IPM and water-or-alcohol requirements are met.

Water and alcohol limitations

Claims 5, 10, 14, 16, 18, and 19 require at least 40 weight percent of water, alcohol, or a combination. Some claims limit the alcohol to:

Ethanol;
Isopropyl alcohol; or
A mixture of ethanol and isopropyl alcohol.

These claims create a formulation architecture based on a high-IPM phase combined with a substantial polar solvent fraction.

What do the “consisting essentially of” and “consisting of” claims cover?

Claims 21 through 25 materially change the formulation scope.

Claim 21 covers a composition consisting essentially of:

The anti-psoriatic agent;
IPM; and
At least 40 weight percent water, alcohol, or a water-alcohol mixture.

“Consisting essentially of” generally permits additional ingredients that do not materially affect the basic and novel characteristics of the claimed composition. In this case, the basic formulation characteristics are likely the IPM-rich liquid vehicle, the polar solvent fraction, and delivery of the anti-psoriatic agent.

Claim 24 is narrower. It recites a composition consisting of:

The anti-psoriatic agent;
IPM;
A surfactant; and
At least 40 weight percent of a water-alcohol mixture.

The “consisting of” language generally excludes unrecited components that would make the composition materially different from the listed formulation. A commercial product containing additional penetration enhancers, preservatives, antioxidants, polymers, or other excipients would require a close claim-construction analysis under the specific wording and prosecution history.

How should infringement of U.S. Patent 5,990,100 be analyzed?

A literal infringement analysis should begin with claims 1 and 7, then test the narrower claims.

Composition claim checklist

A competing product would need to be evaluated for:

Whether it is a liquid.
Whether it is suitable for topical administration to a human.
Whether it is labeled, formulated, or intended for psoriasis treatment.
Whether it contains a listed anti-psoriatic agent.
Whether the active concentration falls within the applicable range.
Whether IPM is present at 15 to 97 weight percent.
Whether the composition satisfies any additional water, ethanol, isopropyl alcohol, surfactant, or “consisting” limitation.

A formulation containing a corticosteroid and 10 weight percent IPM would not literally satisfy claim 1 because the minimum IPM concentration is 15 weight percent. A formulation containing 20 weight percent IPM, a corticosteroid, and a liquid topical dosage form could satisfy the broad composition limitations if the active and psoriasis-treatment requirements are met.

A product using a nonlisted active, such as a nonsteroidal immunomodulator, would not literally satisfy the active-agent limitation in claim 1 unless the product also contains one of the listed agents.

Method claim checklist

Method claim risk depends on the actual or induced use of the product for psoriasis. The method claims are narrower than a pure composition claim in one respect because they require treatment of a human having psoriasis. Product labeling, promotional materials, physician instructions, and intended-use evidence would be relevant to an induced-infringement theory.

When does U.S. Patent 5,990,100 lose exclusivity?

The patent is no longer a live U.S. exclusivity barrier under its ordinary patent term. U.S. utility patents generally expire 20 years after the earliest effective nonprovisional filing date for applications subject to the modern term rules, with possible adjustments under 35 U.S.C. § 154(b) and extensions under 35 U.S.C. § 156.[1]

Patent No. 5,990,100 issued in 1999. Its ordinary term therefore ended in the late 2010s, depending on its effective filing date and any recorded term adjustment. No current commercial exclusivity should be inferred from the existence of the patent number.

Exclusivity issue	Assessment
U.S. patent status	Ordinary term expired
Current composition blocking right	None based on the expired claims
Current method-of-use blocking right	None based on the expired claims
Patent-term extension	No extension is established by the supplied claim record
Regulatory exclusivity	Separate from patent status
Orange Book effect	Depends on whether the patent was listed for an approved drug product

What is the Orange Book status of U.S. Patent 5,990,100?

The patent claims a formulation platform and psoriasis treatment methods. A patent is not automatically listed in the FDA Orange Book merely because it covers a pharmaceutical composition or a method of treatment.

Orange Book listing generally concerns patents submitted for FDA-approved drug products and recognized as covering the drug substance, drug product, or approved method of use under FDA listing rules.[2] A formulation patent can be listed if it covers an approved drug product, but the patent number alone does not establish listing status.

The claims provided do not identify:

An FDA-approved product;
A New Drug Application;
A drug product trade name;
A reference-listed drug;
A listed dosage form; or
A listed Orange Book patent-use code.

The patent should therefore be treated as a formulation patent distinct from any Orange Book status. An expired patent would not support a current Paragraph IV challenge or a current statutory stay in any event.

Are there Paragraph IV challenges or generic-entry issues?

No current Paragraph IV risk follows from an expired patent. Paragraph IV certifications address listed patents for an approved reference drug under the Abbreviated New Drug Application pathway.[3] The relevant questions would have been:

Whether the patent was listed for a reference product;
Whether the patent was unexpired when an ANDA was filed;
Whether a generic applicant certified that the patent was invalid, unenforceable, or not infringed;
Whether the patent owner filed suit within 45 days; and
Whether a 30-month stay applied.

Because the patent’s ordinary term has ended, a new ANDA applicant would not face a live patent term based on these claims. The FDA could still impose requirements based on the reference product’s regulatory status, labeling, bioequivalence, safety, or other listed patents.

How does this patent compare with active psoriasis patent estates?

U.S. Patent 5,990,100 is materially different from modern psoriasis patent estates.

Patent category	Typical protected subject matter	Relevance of Patent 5,990,100
Active-ingredient patent	New chemical entity or analog	Does not claim a new molecular entity
Salt or crystal patent	Solid-state form or salt	Not addressed
Biologic patent	Antibody, sequence, epitope, formulation, or manufacturing	Not applicable
Device patent	Applicator, pump, aerosol, or delivery system	Not addressed
Formulation patent	Vehicle, concentration, release, stability, or delivery	Core category
Method-of-use patent	Treatment of a disease or patient subgroup	Claims 7 and 26-36
Manufacturing patent	Process, mixing order, purification, or scale-up	Not claimed in the supplied claims

The patent’s central inventive concept is the use of a high-IPM liquid carrier for topical delivery of established anti-psoriatic agents. That differs from current estates around biologics such as adalimumab, ustekinumab, secukinumab, ixekizumab, guselkumab, and risankizumab, where patent scope often centers on antibodies, formulations, dosing regimens, patient populations, and manufacturing processes.

What manufacturing and formulation barriers remain after patent expiry?

Patent expiry removes the claimed exclusivity but does not eliminate technical barriers. A commercial developer would still need to address:

Solubility of the anti-psoriatic agent in the IPM and alcohol system.
Phase stability across temperature conditions.
Evaporation and flammability of ethanol or isopropyl alcohol.
Skin tolerability and irritation.
Dose uniformity in a high-solvent liquid.
Packaging compatibility.
Microbial control where water is present.
Calcipotriol photostability and chemical stability.
Corticosteroid potency, impurity, and degradation control.
Manufacturing controls for phase addition and mixing.

These issues may support later formulation patents, trade secrets, or regulatory differentiation, but they are not claimed by U.S. Patent 5,990,100 unless a later patent separately covers them.

Which companies are challenging U.S. Patent 5,990,100?

The supplied record identifies no challenger, Paragraph IV case, settlement agreement, license, or litigation proceeding. The patent’s age and expired status make current litigation exposure unlikely. Any historical dispute would need to be evaluated through USPTO, PACER, FDA Orange Book, and assignment records rather than inferred from the claims.

No licensing right is apparent from the claim language. Patent ownership, assignments, security interests, and licenses are separate record issues and do not alter the technical scope of the claims.

How strong is the patent estate for a new IPM psoriasis product?

The current patent strength is effectively zero as an enforceable U.S. exclusion right because the patent has expired. Historically, the estate had moderate breadth at the independent-claim level but limited depth.

Strengths included:

Broad coverage of several anti-psoriatic classes.
A wide IPM range of 15 to 97 weight percent.
Both composition and method claims.
Dependent claims covering corticosteroids and calcipotriol.
Specific protection for high-IPM water-ethanol systems.

Limitations included:

Dependence on IPM at unusually high concentrations.
Requirement for a liquid topical formulation.
Restriction to psoriasis treatment.
Restriction to enumerated anti-psoriatic agents.
No claims to manufacturing, packaging, device design, or pharmacokinetic performance.
No claim to biologic psoriasis therapies or modern nonlisted actives.

Key Takeaways

U.S. Patent 5,990,100 covers liquid topical psoriasis compositions containing 15 to 97 weight percent IPM and a corticosteroid, calcipotriol, retinoid, tar, or mixture.
Claims 6, 12, and 30 are the most formulation-specific, particularly for 38 to 60 weight percent IPM with water and ethanol.
Claims 7 and 26 through 36 cover corresponding topical treatment methods.
Claims 21 through 25 impose “consisting essentially of” and “consisting of” limitations that restrict additional excipients.
The patent is an expired formulation patent and does not create a current U.S. blocking right.
Paragraph IV exposure depends on separate Orange Book-listed patents, not merely on this patent number.
Current commercial risk would arise from later patents, regulatory exclusivity, product-specific patents, or trade-secret manufacturing controls rather than from Patent No. 5,990,100.

FAQs

Does U.S. Patent 5,990,100 cover calcipotriene products?

It covers liquid topical compositions containing 0.0001 to 0.1 weight percent calcipotriol when the IPM and water-or-alcohol limitations in the applicable dependent claims are satisfied. The claim language uses “calcipotriol,” which should be distinguished from other salts, analogs, or formulations unless the relevant chemical identity is legally equivalent.

Does the patent cover a psoriasis cream containing isopropyl myristate?

Only if the product is a liquid under the claim construction, contains at least 15 weight percent IPM, includes a listed anti-psoriatic agent, and satisfies the remaining limitations. A conventional semisolid cream may not meet the liquid requirement.

Does the patent cover corticosteroid sprays?

Potentially, if the spray formulation is a liquid, contains at least 15 weight percent IPM and 0.0001 to 30 weight percent corticosteroid, and is suitable for topical psoriasis treatment. The dependent corticosteroid claims impose narrower concentration and solvent requirements.

Can a generic launch rely on expiration of this patent?

Yes, expiration removes this patent as a continuing U.S. infringement barrier. A generic developer must still assess other unexpired patents, FDA requirements, labeling, and any exclusivity associated with the reference product.

Does high IPM concentration alone infringe the patent?

No. IPM concentration alone is insufficient. The composition must also contain a listed anti-psoriatic agent, fall within the relevant concentration range, be liquid and topically suitable for human psoriasis treatment, and satisfy any additional limitations of the asserted claim.

References

United States Patent and Trademark Office. (2024). Patent term adjustment and patent term extension. https://www.uspto.gov/patents/laws/pta
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
Legal Information Institute. (2024). 21 U.S.C. § 355(j): Abbreviated applications and patent certifications. Cornell Law School. https://www.law.cornell.edu/uscode/text/21/355
United States Patent and Trademark Office. (1999). U.S. Patent No. 5,990,100. Washington, DC: U.S. Department of Commerce.

Details for Patent: 5,990,100

Summary for Patent: 5,990,100