United States Patent 5,079,262: Scope, Claim Analysis, Expiration, and ALA Photodynamic Therapy Patent Landscape

U.S. Patent No. 5,079,262 covers photodynamic treatment of selected malignant and non-malignant lesions by administering 5-aminolevulinic acid, inducing intracellular protoporphyrin IX, and exposing the lesion to activating light. The patent is a foundational ALA photodynamic therapy patent, but its enforceable term has expired. It no longer creates a blocking patent risk for current U.S. products. Later patents focused on formulations, illumination systems, treatment parameters, and specific indications have been more commercially relevant for Levulan and Ameluz.

What does U.S. Patent 5,079,262 protect?

The patent protects a treatment sequence rather than a chemical compound:

A patient has a specified malignant or non-malignant tissue abnormality or lesion.
The patient receives 5-aminolevulinic acid, commonly called ALA or 5-ALA.
The lesion converts ALA through the heme biosynthesis pathway into protoporphyrin IX, or PpIX.
The lesion is exposed to light within the photoactivating spectrum of PpIX.
The resulting photochemical reaction treats the lesion.

The central inventive concept is selective photodynamic therapy based on metabolic accumulation of PpIX after ALA administration.

The patent does not claim ALA as a composition of matter. It does not claim PpIX itself, a particular cream, gel, patch, light source, or device. Its claims are method-of-treatment claims.

Patent identification and legal status

Field	Information
U.S. patent	5,079,262
Patent type	Utility patent
Technology	ALA-induced PpIX photodynamic therapy
Claim category	Medical-treatment method
Core active agent	5-aminolevulinic acid
Core mechanism	Induction of PpIX followed by photoactivation
Principal inventorship	John C. Kennedy and collaborators
Priority period	Late 1980s
U.S. grant date	January 7, 1992
Original term rule	Pre-June 8, 1995 patent term, generally 17 years from grant
Expected ordinary expiration	January 7, 2009
Current blocking status	Expired
Current commercial significance	Foundational prior art and historical platform patent

The patent issued before the Uruguay Round Agreements Act changed U.S. patent term calculation. Its ordinary term therefore ran for 17 years from issuance, subject to any applicable adjustment. No currently enforceable exclusivity should be attributed to U.S. Patent 5,079,262.

How broad is independent claim 1?

Claim 1 is broad in therapeutic concept but limited by several required elements.

Required claim elements

A practicing party would need to satisfy each of the following:

Claim element	Scope
Patient treatment	Treatment must be performed in a patient in need thereof
Lesion location	Skin, conjunctiva, respiratory mucosa, digestive mucosa, vaginal mucosa, endometrium, or urothelium
Lesion sensitivity	The tissue abnormality or lesion must be sensitive to PpIX
Active agent	An effective amount of 5-aminolevulinic acid must be administered
Biological effect	Administration must induce PpIX synthesis in the lesion
Light treatment	The lesion must be exposed to light within the PpIX photoactivating action spectrum
Therapeutic purpose	The method must treat a malignant or non-malignant tissue abnormality or lesion

The claim is not limited to a specific concentration, dosage, formulation, administration interval, incubation period, light dose, irradiance, lesion size, or treatment schedule.

The absence of those limitations gives claim 1 substantial technical breadth. A topical ALA cream, oral ALA regimen, or parenteral ALA treatment could fall within the claim if the other elements were met. The claim also does not require a particular commercial light source.

Geographic and anatomical limits

Claim 1 does not cover every use of ALA-PDT. It expressly identifies anatomical sites:

Skin
Conjunctiva
Respiratory mucosa
Digestive mucosa
Vaginal mucosa
Endometrium
Urothelium

A treatment directed exclusively to a tissue outside these categories would require a separate infringement analysis. The claim also requires a lesion that is sensitive to PpIX. A purely diagnostic use, cosmetic use, or use without lesion treatment would not automatically satisfy the claim.

Chemical limitations

The claim requires 5-aminolevulinic acid. It does not expressly recite:

ALA hydrochloride
A specific salt
A prodrug
A nanoemulsion
A liposomal carrier
A polymeric delivery system
A particular purity level
A specific stereochemical form

A formulation containing ALA hydrochloride could potentially satisfy the active-agent limitation because ALA hydrochloride dissociates to provide ALA. Whether a derivative or prodrug falls within the claim would depend on claim construction, prosecution history, and whether the administered substance is legally treated as 5-aminolevulinic acid rather than a different chemical entity.

What do dependent claims 2 through 7 add?

Claim 2: specified malignant lesions

Claim 2 narrows claim 1 to:

Basal cell carcinoma
Baso-squamous carcinoma
Squamous cell carcinoma

It is a species claim within the broader malignant-lesion category. It would be relevant to dermatology products directed at non-melanoma skin cancers, but the claim does not add a formulation or light-source limitation.

Claim 3: specified non-malignant lesions

Claim 3 covers:

Psoriasis
Genital warts

This claim is narrower than claim 1 because it identifies specific non-malignant indications. It does not cover every benign lesion.

Claim 4: light wavelength

Claim 4 limits the activating light to 350-640 nanometers.

This range includes ultraviolet-visible and blue-to-red portions of the spectrum, although the clinically important region for many ALA-PDT applications is commonly in the blue or red range. A product using light outside 350-640 nm would not satisfy the literal wavelength limitation of claim 4, although claim 1 remains broader because it does not recite a numerical range.

Claim 4 is technically important because it connects the method to the optical activation profile of PpIX. It does not specify:

Light dose in joules per square centimeter
Irradiance
Exposure duration
Continuous or pulsed operation
Broadband or narrowband light
Laser or non-laser operation

Claims 5, 6, and 7: route of administration

Claim	Route
5	Parenteral administration
6	Topical administration
7	Oral administration

These claims create route-specific fallbacks. Claim 6 is the commercially important claim for topical ALA-PDT products such as Levulan and Ameluz, although the patent has expired.

The claims do not distinguish among topical dosage forms. A topical solution, gel, cream, lotion, ointment, patch, or other vehicle could potentially satisfy claim 6 if it delivers ALA and the remaining claim elements are met.

When did U.S. Patent 5,079,262 lose exclusivity?

The patent’s ordinary term expired in January 2009, 17 years after issuance. Because it is an older U.S. patent, its term was generally governed by the pre-1995 grant-based regime rather than the current 20-year-from-earliest-effective-filing-date regime [1].

Event	Date or period
Priority activity	Late 1980s
U.S. grant	January 7, 1992
Ordinary 17-year term	January 7, 2009
Post-expiration status	Public-domain method technology

Expiration means the claims cannot support a new infringement action for conduct occurring after expiration. The patent remains relevant as prior art and as evidence of the historical development of ALA-PDT.

What FDA products are associated with the ALA-PDT technology?

Levulan Kerastick

Levulan Kerastick contains aminolevulinic acid hydrochloride and is used with blue light photodynamic therapy for actinic keratoses. The FDA approved Levulan in 1999 for actinic keratoses of the face or scalp with the BLU-U Blue Light Photodynamic Therapy Illuminator [2].

The product consists of two coordinated components:

ALA hydrochloride topical solution
A designated blue-light illumination system

The FDA-approved product is narrower than claim 1 of the patent because the label focuses on actinic keratoses rather than all listed malignant and non-malignant lesions.

Ameluz

Ameluz is a 10% aminolevulinic acid hydrochloride topical gel approved for actinic keratoses of the face and scalp in combination with the BF-RhodoLED lamp [3]. It uses a different formulation and illumination platform from Levulan.

Ameluz illustrates the commercial shift from the broad foundational method claim toward narrower product-specific protection covering:

Topical gel composition
Excipient system
Skin penetration
PpIX production
Illumination conditions
Treatment of actinic keratoses
Product and device combination

FDA status comparison

Product	Active ingredient	Dosage form	FDA indication	Light platform
Levulan Kerastick	ALA hydrochloride	Topical solution	Actinic keratoses of face or scalp	BLU-U blue light
Ameluz	ALA hydrochloride	10% topical gel	Actinic keratoses of face or scalp	BF-RhodoLED

ALA is a small molecule, not a biologic. Biosimilar approval rules do not apply. Competitive entry is governed by drug, formulation, device, and patent considerations rather than the biosimilar pathway.

What patent landscape surrounds ALA photodynamic therapy?

The post-5,079,262 landscape has several distinct layers.

Foundational method patents

These patents cover the basic concept of administering ALA to induce PpIX and activating the accumulated PpIX with light. U.S. Patent 5,079,262 is the principal example.

Because the patent is expired, the foundational method is available for commercial development, subject to later enforceable patents.

Formulation patents

Later patents have focused on topical formulations that improve:

ALA stability
Skin penetration
PpIX accumulation
Patient tolerability
Storage characteristics
Delivery to actinic keratoses
Compatibility with light treatment

Formulation claims can be commercially important even when the underlying ALA-PDT method is no longer protected. A generic product using a different vehicle may avoid a formulation patent while still practicing the expired method.

Method-of-use patents

Later method patents can target:

Actinic keratoses of particular anatomical sites
Specific lesion severity
Treatment intervals
Pretreatment or occlusion
Daylight PDT
Combination therapy
Treatment of acne, photodamage, or other dermatologic conditions
Particular light wavelengths or treatment parameters

Method-of-use protection is narrower than the expired claim 1 if it covers only a defined indication or treatment protocol. It can still create a Paragraph IV litigation risk where the patent is listed for an approved product and the proposed generic seeks the same indication.

Illumination-system patents

Light-source patents and device patents may cover:

Blue-light LED arrays
Red-light LED systems
Wavelength control
Dose monitoring
Treatment distance
Contact or non-contact illumination
Interlocks and safety systems
Coordinated drug-device operation

A drug competitor may avoid a drug patent but still need to address device patents, regulatory requirements, or restrictions on use of an approved branded illuminator.

Manufacturing and process patents

Manufacturing patents may cover:

ALA hydrochloride production
Purification
Stability enhancement
Mixing and filling
Packaging
In situ preparation
Two-component applicators
Light-protective containers

These patents generally do not prevent all ALA-PDT competition. They can, however, raise development and supply-chain costs where the competitor relies on a protected process or delivery package.

What is the Orange Book status of U.S. Patent 5,079,262?

U.S. Patent 5,079,262 should not be treated as a current Orange Book barrier for Levulan or other ALA products because it expired in 2009. Orange Book-listed patents can include drug-substance, drug-product, and method-of-use patents, but an expired patent does not provide current enforceable exclusivity [4].

For a current abbreviated new drug application strategy, the relevant questions are:

Which patents are currently listed for the reference product?
Which listed patents remain unexpired?
Does the proposed product use the same formulation, indication, route, or device?
Does the applicant need a Paragraph IV certification?
Can the applicant use a Section viii statement to omit a patented method of use?
Is the reference product eligible for an ANDA at all, or is a different pathway required?

A Paragraph IV challenge to U.S. Patent 5,079,262 would have no practical value because the patent has expired. Any present patent dispute would center on later, unexpired patents.

Which companies are exposed to ALA-PDT patent competition?

Levulan-related exposure

Levulan-related commercial rights have historically been associated with DUSA Pharmaceuticals and its corporate successors. The main exposure is not the expired foundational method patent. It is the remaining portfolio surrounding:

The commercial topical formulation
The applicator
The approved indication
The BLU-U illumination system
Label-linked method claims
Manufacturing and packaging

Ameluz-related exposure

Ameluz has been associated with Biofrontera and related corporate entities. Its patent exposure includes the formulation and product-specific protection supporting the 10% gel and coordinated red-light treatment platform.

The principal competitive threat is a topical ALA product that can obtain FDA approval without practicing enforceable formulation or method claims associated with Ameluz.

Competitive landscape

Competitor type	Main advantage	Main patent risk
Generic topical ALA	Lower cost and established active ingredient	Formulation, method-of-use, and Orange Book-listed patents
Levulan alternative	Familiar blue-light treatment model	Product, applicator, and device patents
Ameluz alternative	Gel-based delivery and red-light platform	Gel formulation and product-specific claims
Compounded ALA	Flexible formulation and concentration	Regulatory status, quality, labeling, and commercial scale
Daylight PDT product	Reduced device dependence	Daylight-treatment method claims and label restrictions
New PpIX-inducing agent	Potentially differentiated efficacy or tolerability	New chemical entity and formulation patents

How strong is the patent estate based on U.S. Patent 5,079,262?

The patent estate is historically strong but currently weak as an exclusionary asset.

Strengths at issuance

Broad therapeutic concept
Coverage of multiple mucosal and epithelial sites
Coverage of both malignant and non-malignant lesions
Coverage of parenteral, topical, and oral administration
No narrow formulation limitation in the independent claim
No narrow light-source limitation in the independent claim

Current weaknesses

Expired patent term
No current blocking power
Broad claim language does not revive exclusivity
ALA is an established active ingredient
Current competition depends on later patents and FDA approval strategy
Product claims are likely to be more commercially important than the original platform claim

The patent remains valuable for freedom-to-operate history, prior-art mapping, and identification of the core ALA-PDT mechanism. It does not support a current royalty demand or injunction.

What generic launch scenarios exist?

Scenario 1: Topical ALA with a non-infringing formulation

A competitor could develop a topical ALA product using a formulation outside any enforceable branded formulation claims. The primary hurdles would be FDA approval, product quality, stability, skin penetration, and clinical or bioequivalence requirements.

Scenario 2: Label carve-out

If an approved product has patented indications, an ANDA applicant may seek approval for non-patented uses through a Section viii statement, provided the labeling omits the protected method of use.

Scenario 3: Paragraph IV challenge

A Paragraph IV certification would be directed at any unexpired Orange Book-listed patent associated with the reference product. The expired 5,079,262 patent would not be an actionable target.

Scenario 4: Alternative illumination

A competitor could pair ALA with a different light system, subject to medical-device clearance, labeling, and any enforceable device patents. Changing the light source would not avoid the expired foundational method, but it may avoid later device claims.

Scenario 5: Non-approved or compounded products

Compounded ALA may compete in limited settings, but it does not automatically have the same FDA approval, labeling, manufacturing, reimbursement, or market-access position as an NDA product.

What patent litigation and settlements affect this technology?

The principal legal significance of U.S. Patent 5,079,262 is historical. Its expiration eliminates it as a present litigation weapon. Litigation risk for ALA-PDT products is more likely to arise from later patents involving:

Topical gel or solution formulations
Treatment of actinic keratoses
Illumination systems
Product-device combinations
Specific dosing or pretreatment conditions
Manufacturing and packaging

A settlement involving a later listed patent could delay generic entry even though the foundational patent has expired. The existence of a settlement would not extend the legal term of 5,079,262.

What geographic coverage does the patent provide?

U.S. Patent 5,079,262 provided rights only in the United States. Corresponding foreign applications or patents would need separate review. Patent protection in Canada, Europe, Australia, Japan, or other jurisdictions depended on local family members, national-phase prosecution, and each jurisdiction’s term rules.

The global ALA-PDT landscape cannot be inferred solely from the U.S. patent. U.S. expiration does not establish foreign expiration.

Key Takeaways

U.S. Patent 5,079,262 covers ALA administration followed by PpIX-activating light treatment.
Claim 1 is a broad method claim covering specified epithelial and mucosal lesions.
Claims 2 and 3 identify carcinoma, psoriasis, and genital-wart embodiments.
Claim 4 specifies activating light in the 350-640 nm range.
Claims 5, 6, and 7 cover parenteral, topical, and oral administration.
The patent issued January 7, 1992 and ordinarily expired January 7, 2009.
The patent is foundational prior art, not a current exclusivity barrier.
Levulan and Ameluz rely on later product, formulation, method, and device protection.
ALA is a small molecule; biosimilar rules do not apply.
Current generic risk depends on unexpired Orange Book-listed and non-listed patents, FDA pathway, formulation design, and illumination strategy.
Any current Paragraph IV dispute would concern later patents, not U.S. Patent 5,079,262.

FAQs

Can a company practice the core ALA-PDT method without a license to U.S. Patent 5,079,262?

Yes. The patent’s term has expired, so the claimed U.S. method is no longer subject to patent enforcement.

Does using ALA hydrochloride avoid the patent claims?

No. ALA hydrochloride may satisfy an ALA limitation because it delivers 5-aminolevulinic acid. The patent’s expiration makes that infringement question commercially moot for the patent itself.

Does the patent cover daylight photodynamic therapy?

Claim 1 may encompass activating light within the PpIX action spectrum, but claim 4 is limited to 350-640 nm. Separate daylight-PDT patents may impose different risks.

Is a new ALA gel automatically a generic version of Levulan?

No. A new gel may require a different FDA strategy depending on formulation, indication, labeling, and reference-product selection. It also must be assessed against later formulation and method patents.

Can the expired patent support a royalty in a license agreement?

It can be cited as historical technology or prior art, but it cannot support a patent royalty for post-expiration U.S. practice solely because the claimed method is covered by U.S. Patent 5,079,262.

References

United States Patent and Trademark Office. (1992). U.S. Patent No. 5,079,262, Photochemotherapeutic method.
U.S. Food and Drug Administration. (1999). Levulan Kerastick aminolevulinic acid hydrochloride prescribing information.
U.S. Food and Drug Administration. (2016). Ameluz aminolevulinic acid hydrochloride prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	287709	⤷ Start Trial
Australia	3883293	⤷ Start Trial
Australia	5888796	⤷ Start Trial
Australia	6034390	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 5,079,262