US Patent 6,034,267: Scope, Claim Strength, and Landscape Impact
US Patent 6,034,267 is directed to diagnostic and photochemotherapeutic methods and related compositions/kits using a family of α-alkylamino-photodynamic agents defined by Formula I:
R2N-CH2-CO-CH2-CO-OR1
with the key functional structure tied to light exposure and, for in vitro diagnosis, fluorescence readout. The claims focus on (1) method-of-use for external/internal surfaces, (2) an in vitro fluorescence assay method, (3) pharmaceutical compositions with excipients and optional additives to improve delivery, and (4) a multi-container kit.
What does the patent actually claim (core subject matter)?
Claim-set architecture
US 6,034,267 has 16 claims, structured into four practical buckets:
- In vivo diagnostic/photochemotherapeutic method (Claims 1-7)
- Narrower method dependencies (Claims 2-7 are mostly formula and light-range dependent)
- In vitro fluorescence diagnostic method (Claims 13-14)
- Composition and kit coverage to support administration and diagnosis (Claims 8-12 and 15-16)
The scope is not limited to one use; it covers both photoactivated therapy and fluorescence diagnostics, using the same Formula I agent family.
What is the claim language scope for the Formula I agent?
Formula I definition
All independent claim sets (method/composition/kit and in vitro assay) use the same defining formula:
R2N-CH2-CO-CH2-CO-OR1
where:
- R1 is alkyl
- each R2 is independently hydrogen or alkyl
- alkyl groups are optionally substituted by: hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo, or fluoro
- alkyl may be interrupted by oxygen atoms
- claims cover pharmaceutically acceptable salts too
Explicit representative embodiments
The claims include express examples, constraining at least one commercial/technical center of gravity:
- ALA-methyl ester
- ALA-ethyl ester
- ALA-propyl ester
- ALA-hexyl ester
- ALA-heptyl ester
- ALA-octyl ester
This matters because ALA derivatives are historically central in photodynamic applications; the patent’s claim recites those ester variants as concrete embodiments of Formula I.
What do the in vivo method claims cover? (diagnosis + photochemotherapy)
Independent claim 1 (method for external/internal surfaces)
Claim 1 covers:
- a method for diagnosis or photochemotherapeutic treatment
- of disorders or abnormalities of external or internal surfaces
- comprising:
1) administering to the sites of investigation/affected surfaces
a composition containing a Formula I compound (or salt)
2) exposing those sites/surfaces to light
There is no explicit requirement for fluorescence readout in Claim 1; light exposure is the activating step for both diagnostic and therapy uses.
Dependent claims narrowing Claim 1
- Claim 2: aryl is phenyl or a monocyclic 5-7 membered heteroaromatic
- Claim 3: R1 is unsubstituted alkyl and each R2 is hydrogen
- Claim 4: R1 is unsubstituted alkyl or each R2 is hydrogen (broad disjunct)
- Claim 5: alkyl (either R1 or relevant alkyl parameter per the claim construction) contains up to 10 carbon atoms
- Claim 6: compound is one of the listed ALA-alkyl esters (methyl, ethyl, propyl, hexyl, heptyl, octyl)
- Claim 7: light wavelength region is 500-700 nm
Scope read: Claim 1 is broad on method type (diagnosis and photochemotherapy), broad on anatomic context (external or internal surfaces), and broad on chemical substitutions (many tolerated substituents and optional heteroatom interruptions). The strongest built-in operational limiter is the “exposing to light” requirement, and further constraints appear in dependent claims (light range and specific ester embodiments).
What does the pharmaceutical composition claim cover?
Independent claim 8 (composition)
Claim 8 covers a pharmaceutical composition comprising:
- an effective diagnostic or therapeutic amount of the Formula I compound (or pharmaceutically acceptable salt)
- plus at least one pharmaceutical carrier/excipient
The claim inherits the full breadth of Formula I:
- R1 alkyl
- R2 hydrogen/alkyl
- optional substituents (hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo, fluoro)
- optional oxygen interruption
- salts
Dependent composition claims
- Claim 9: compound is one of the listed ALA esters
- Claim 10: composition further contains at least one surface-penetration assisting agent, and optionally one or more chelating agents
- Claim 11: surface-penetration assisting agent is dimethyl sulfoxide (DMSO)
- Claim 12: again limits compound to the listed ALA esters
Scope read: Claim 8 is a classic “agent + carrier” composition claim. Claim 10 adds delivery chemistry coverage via penetration assisting agents and optional chelators, which expands infringement theory beyond pure API formulations into co-formulation requirements.
What does the in vitro diagnostic claim require?
Independent claim 13 (fluorescence-based assay)
Claim 13 is limited to:
- in vitro diagnosis
- by assaying a sample of body fluid or tissue
- with steps:
1) admix body fluid/tissue with the Formula I compound (or salt)
2) expose mixture to light
3) ascertain fluorescence level
4) compare fluorescence level to control levels
The claim does not specify the excitation wavelength here, unlike Claim 7 for in vivo use.
Dependent claim 14
- compound is one of the listed ALA esters
Scope read: Claim 13 is method-formula-combination and readout-based (fluorescence + control comparison). It is not limited to any specific disease, tissue type, or fluorescence instrument design beyond “ascertaining fluorescence.”
What does the kit claim cover?
Independent claim 15
A diagnostic/photochemotherapy kit comprising:
1) First container: Formula I compound (or salt)
2) Second container: at least one surface penetration assisting agent
3) optionally third container: one or more chelating agents
- either in the first container or a third container
This claim is operationally clear: it targets packaged systems with delivery enhancers pre-positioned.
Dependent claim 16
- compound is one of the listed ALA esters
Scope read: Claim 15 is important for enforcement because kit sales create a tangible, end-customer product structure that maps to the claim. The “container” structure is also the kind of feature that can be evaluated during diligence and competitive landscaping.
How broad is the patent’s chemical scope versus operational scope?
Chemical breadth (high)
- Formula I is broad: multiple alkyl sizes, optional substitutions, oxygen interruption, and optional R2 alkyl vs hydrogen.
- Dependent constraints do narrow, but even those still allow multiple ester lengths and substitution patterns.
Operational breadth (medium)
- In vivo: “diagnosis or photochemotherapeutic treatment” with light exposure is the core.
- In vitro: fluorescence readout + control comparison is required.
- A specific light range appears only in dependent Claim 7 (500-700 nm), which limits that narrow path but does not cap Claim 1.
Practical limiter: light exposure
Every core path requires exposure to light. That is the key “activation” feature linking diagnosis/therapy to photochemistry.
Where the claims likely land in real-world embodiments
Most directly captured product archetype
The combination of:
- ALA-alkyl ester compounds
- light activation
- optional DMSO as penetration enhancer
- optional chelators
- kit packaging
maps to typical photodynamic workflows where an esterified ALA prodrug is delivered with penetration aids and then activated with visible light for fluorescence and/or therapy.
Specificity hotspots for competitors
- ALA-methyl/ethyl/propyl/hexyl/heptyl/octyl esters: these are explicitly named across method, composition, and kit claims.
- 500-700 nm visible range: a narrow claim path.
- DMSO: explicitly named as a surface penetration assisting agent.
Claim-by-claim enforceability profile (what is strongest for infringement tests)
| Claim |
Coverage type |
Built-in limitations that define infringement |
Breadth score (relative) |
| 1 |
In vivo method (diagnosis/photochemotherapy) |
Formula I agent administered to external/internal surfaces + light exposure |
Medium-High |
| 2 |
In vivo formula narrowing |
aryl definition |
Medium |
| 3 |
In vivo formula narrowing |
R1 unsubstituted alkyl and R2 hydrogen |
Medium |
| 4 |
In vivo formula narrowing |
R1 unsubstituted alkyl OR R2 hydrogen |
High (disjunctive) |
| 5 |
In vivo formula narrowing |
alkyl up to 10 carbons |
Medium |
| 6 |
In vivo explicit embodiments |
listed ALA ester list |
Medium |
| 7 |
In vivo operational narrowing |
light wavelength 500-700 nm |
Medium-Low |
| 8 |
Composition |
Formula I agent + carrier/excipient |
High |
| 9 |
Composition explicit embodiments |
listed ALA ester list |
Medium |
| 10 |
Composition add-on |
surface penetration assisting agent + optional chelators |
Medium |
| 11 |
Composition delivery enhancer |
DMSO as penetration agent |
Medium-Low |
| 12 |
Composition explicit embodiments |
listed ALA ester list |
Medium |
| 13 |
In vitro method |
sample admix + light exposure + fluorescence readout + control comparison |
Medium |
| 14 |
In vitro explicit embodiments |
listed ALA ester list |
Medium |
| 15 |
Kit |
containers + penetration assistant + optional chelator |
Medium |
| 16 |
Kit explicit embodiments |
listed ALA ester list |
Medium |
Breadth score is qualitative: higher means more competitors plausibly match.
Patent landscape implications (how this US 6,034,267 likely interacts with surrounding IP)
Landscape role: a “platform” claim around ALA ester prodrugs
The claim family is organized around:
- Formula I agent class
- ALA-alkyl ester explicit list
- delivery aids (penetration enhancer, optional chelators)
- diagnostic photodynamic workflow (fluorescence + control comparison)
- kit packaging
In landscape terms, US 6,034,267 functions like a use-and-formulation “bridge” that can capture multiple product forms:
- direct formulations,
- co-formulated delivery enhancer products,
- diagnostic assay workflows,
- and kit packaging.
Where it will be most relevant for freedom-to-operate (FTO)
- If a competitor sells an ALA-alkyl ester diagnostic/phototherapy product where the claim can map to “administer + light,” the patent is directly implicated.
- If the competitor co-packages DMSO (or other surface penetration assisting agent) in a kit format, Claim 15 and Claim 10/11 become practical infringement targets.
- If a competitor offers in vitro fluorescence assays using the agent class and compares fluorescence to controls, Claim 13 is the key hook.
Where it is less likely to be the main barrier
- If a competitor uses a different activation concept that does not include the required “expose to light” mechanics under the method claim structure, or avoids the Formula I agent class altogether, the claim may fall away.
- If the competitor uses a different prodrug class (not captured by Formula I) or avoids the explicit ALA ester embodiments, the likelihood of matching the claim language reduces to the broader Formula I interpretation.
Key gaps and “design-around” levers inside the claim language (practical, claim-rooted)
These are structural features inside the claims that can narrow or block coverage for a would-be entrant:
- Formula I must match: departures outside R2N-CH2-CO-CH2-CO-OR1 with the defined R1/R2 constraints and substitution/oxygen interruption rules can reduce coverage.
- Light exposure is mandatory: methods that change activation modality may not map unless they still meet the claim requirement as written.
- In vitro claim adds fluorescence + control comparison: workflows that measure fluorescence differently and do not fit “ascertaining level” and “comparing to control levels” can attempt to reduce match.
- Kit claim requires specific packaging structure: separate container requirements for the penetration assistant (and optional chelator placement) can create leverage in commercialization design.
Key Takeaways
- US 6,034,267 covers Formula I α-alkylamino photochemotherapeutic/diagnostic agents with light exposure as the activation step, spanning in vivo methods, in vitro fluorescence assays, compositions, and kits.
- The claim language is chemically broad (substituted alkyl/aryl options and R2 variability), while operational coverage is shaped by light exposure and (for Claim 13) fluorescence readout with control comparison.
- The patent has enforcement-friendly hooks: explicit capture of ALA-methyl through ALA-octyl esters and explicit mention of DMSO as a surface penetration assisting agent, plus a multi-container kit claim structure.
- For competitive landscaping and FTO, the most likely overlap occurs with products that combine ALA ester API + penetration enhancer + light-based diagnostic/therapy workflow, especially in kit form.
FAQs
1) Does US 6,034,267 cover both phototherapy and diagnostics?
Yes. Claim 1 covers diagnosis or photochemotherapeutic treatment with Formula I agent administration and light exposure. Claim 13 covers in vitro diagnosis by fluorescence measurement with light exposure and control comparison.
2) Are ALA esters specifically listed in the claims?
Yes. Multiple claims explicitly name ALA-methyl, ALA-ethyl, ALA-propyl, ALA-hexyl, ALA-heptyl, and ALA-octyl esters.
3) What light parameter is claimed, and where?
Claim 7 specifies a wavelength region of 500-700 nm, but that is dependent on Claim 1. The independent in vitro fluorescence claim (Claim 13) does not specify a wavelength band.
4) What delivery-assist components appear in the patent?
Claim 10 covers at least one surface-penetration assisting agent and optional chelators. Claim 11 specifies dimethyl sulfoxide (DMSO) as the penetration assisting agent.
5) What makes the kit claim distinct from the composition claim?
Claim 15 requires a kit structure with separate containers for the Formula I compound and the surface penetration assisting agent, with optional chelators placed either in the first container or a third container.
References
[1] US Patent 6,034,267, “Method for the diagnosis or photochemotherapeutic treatment … comprising administering a compound of formula I … and exposing … to light,” claims 1-16.
