US Patent 4,454,152: Scope, Claim Architecture, and US Landscape
What does US 4,454,152 claim, and what is its effective scope?
US Drug Patent 4,454,152 claims a specific oral delivery system for methoxsalen (also written 8-methoxypsoralen) combined with a procedural regimen that includes timed UV irradiation. The patent’s scope centers on two tightly linked elements:
- Oral dosage composition
- Methoxsalen in solution
- Methoxsalen is present in a defined weight range relative to the total composition.
- The solvent/vehicle is polyethylene glycol (PEG) or mixtures of PEGs that are fluid at room temperature.
- The composition is contained within a capsule.
- Treatment method
- For subjects afflicted with psoriasis or vitiligo
- Administer the oral composition
- Wait a sufficient time to obtain a peak blood level of methoxsalen
- Irradiate with ultraviolet light
The claims therefore cover both:
- A composition (independent composition protection in Claims 2 and 3), and
- A use method (Claim 1) tying dosing kinetics to UV exposure.
Claim-by-claim construction (high-level, literal features)
| Claim |
Category |
Core limitation set (verbatim concept mapping) |
What is uniquely captured |
| 1 |
Method |
Oral administration of methoxsalen solution in about 10% to about 97.5% by weight PEG (fluid at room temp) in a capsule, then wait for peak blood level, then UV irradiation for psoriasis/vitiligo |
Procedural regimen + specific PEG-capsule formulation |
| 2 |
Composition (unit dosage) |
Oral unit dosage form comprising solution of methoxsalen effective for treatment in about 10% to about 97.5% PEG (fluid at room temp) in a capsule |
PEG concentration range in the capsule unit dosage |
| 3 |
Composition (solution concentration) |
Unit dosage form where total composition contains 0.025% to 10.5% methoxsalen and 10% to 97.5% PEG, all in capsule |
Methoxsalen content range paired to PEG range, in percent-by-weight terms |
Key numeric boundaries that drive scope
The patent uses overlapping ranges that narrow practical infringement analysis:
- PEG (vehicle) fraction: “about 10% to about 97.5% by weight”
- Methoxsalen fraction (Claim 3): “about 0.025% to about 10.5% by weight”
- Vehicle state: PEG or PEG mixture fluid at room temperature
- Packaging: contained within a capsule
- Therapeutic indication for method claim: psoriasis or vitiligo
- System step: waiting time to obtain peak blood level prior to UV irradiation
How do the claims allocate protection: method vs composition?
US 4,454,152 is drafted so that commercial activity can trigger at least one claim even if some process steps vary.
Claim 1 requires a timing-plus-UV sequence
Claim 1 is an end-to-end treatment sequence:
- Administer oral PEG/methoxsalen capsule
- Wait to reach peak blood levels
- Irradiate with UV
This means a product that matches the composition (Claims 2/3) can still avoid Claim 1 if the clinical protocol does not include UV timing tied to peak blood concentration. Conversely, a prescriber protocol that follows the claimed timing sequence can implicate Claim 1 if the oral composition also meets its PEG constraints.
Claims 2 and 3 cover the formulation independently
Claims 2 and 3 are product claims for an oral unit dosage composition:
- If the market sells capsules with methoxsalen solution in PEG meeting the defined ranges and “fluid at room temperature” constraint, the product can be inside the claim without needing UV steps.
This is the critical enforcement pathway: composition coverage is broader than treatment coverage because it does not require proof of patient UV timing.
What is the practical “infringement perimeter” for formulations?
The claims target a narrow formulation architecture:
Required formulation architecture
- Methoxsalen in solution
- Vehicle is PEG or PEG mixtures that are fluid at room temperature
- Composition is capsule-contained (unit dosage form)
- Vehicle content is about 10% to about 97.5% by weight
- Methoxsalen content is about 0.025% to about 10.5% by weight (Claim 3 limitation)
Implications for design-around
The strongest design pressure points are:
- Move vehicle outside the “fluid at room temperature” PEG definition (for example, use non-PEG solvents or PEG grades that are not fluid at room temperature)
- Move outside the weight percent boundaries (either too low or too high PEG fraction; or too low or too high methoxsalen fraction for Claim 3)
- Avoid “solution” by using dispersions or different molecular states (formulation form can matter in a literal reading)
- Avoid capsule packaging if it is essential to the claim language (Claim 1 and Claims 2 and 3 state capsule containment)
The claims do not specify:
- a specific PEG molecular weight,
- a specific UV wavelength (though UV irradiation is inherent),
- a specific dosing schedule length for “peak blood level.”
That omission can broaden coverage because it does not limit the claim to one PEG grade or one UV protocol, as long as the composition and the peak-blood timing concept are satisfied (Claim 1).
How does the “peak blood level” limitation shape method coverage?
Claim 1 is constrained by a pharmacokinetic concept: the treatment must include waiting a sufficient time to reach peak blood level of methoxsalen.
That typically means a protocol keyed to expected systemic exposure dynamics after oral administration. The claim’s language does not set a numeric time (e.g., “2 hours”), which can:
- Expand enforcement coverage to timing that is “sufficient” to reach peak levels, even if clinicians differ in exact hour marks.
- Create evidentiary complexity in disputes, because infringement must be shown relative to blood concentration peaks rather than a fixed delay.
Still, the limitation is functional and tied to oral PEG delivery of methoxsalen, meaning a markedly different delivery technology that shifts systemic time-to-peak could reduce method-claim exposure even if composition claims remain in play.
What is the likely US patent landscape around methoxsalen + oral delivery + UV phototherapy?
Within US practice, the patent landscape for methoxsalen-based photochemotherapy commonly clusters around:
- psoralen compounds (methoxsalen and related agents),
- phototherapy regimens (UV and timing),
- oral formulations (solubilization vehicles, unit dosage formats),
- delivery systems (capsules, emulsions, solid dispersions),
- combination therapies and follow-on formulation patents.
US 4,454,152 sits at the formulation-procedure junction: it is not merely “methoxsalen orally,” but methoxsalen in PEG-based solution in capsules with a regimen that includes peak blood level timing before UV irradiation.
Where US 4,454,152 likely fits relative to earlier and later filings
- Earlier baseline: The general concept of psoralen + UVA/UVB photochemotherapy predates modern oral formulation refinement. US 4,454,152 is best viewed as a formulation-specific improvement: it specifies a PEG-based vehicle that is fluid at room temperature and defines weight ranges.
- Later refinements: Subsequent patents often pursue:
- improved solubility and exposure,
- reduced variability,
- alternative vehicles and capsule technologies,
- dosing regimens tailored to pharmacokinetics,
- differentiation between psoriases and vitiligo dosing schedules.
Because US 4,454,152 claims are tightly tied to PEG weight fraction and capsule containment, later patents that use different vehicles (non-PEG solvents, different PEG grade states, or different formulation forms) can sit alongside without direct coverage, unless they still fall within “PEG fluid at room temperature” and the weight ranges.
Landscape segmentation by claim target
| Segment |
Key question |
How 4,454,152 affects it |
| Product formulation |
Does the capsule contain methoxsalen solution in PEG fluid at room temperature within defined weight ranges? |
Strong relevance due to Claims 2 and 3 |
| Method/regimen |
Does the protocol wait for peak methoxsalen blood level before UV? |
Strong relevance due to Claim 1 |
| UV technique variations |
Does the claim restrict UV parameters? |
Claim text provided only requires UV irradiation; no explicit wavelength limit is visible in the claim set you provided |
| PEG variation |
What PEG molecular weight or grade is used? |
Claim text provided does not impose molecular weight limits; “fluid at room temperature” is the main state constraint |
What does claim 1’s indication coverage imply for commercial use?
Claim 1 is for a subject with:
Commercial exposure therefore includes:
- clinical use for those indications,
- prescribing and administering the claimed regimen in those indications.
Even if the product is sold broadly for photochemotherapy, Claim 1 is activated by the indication of the patient and the UV timing sequence. Claims 2/3 are not indication-limited in the composition language beyond “effective for the treatment,” which is still an intended use constraint but is typically assessed based on the functional treatment effectiveness of methoxsalen for those diseases.
What would be the cleanest enforcement strategy under this patent?
Based on the claim set provided:
- Composition-first enforcement:
- Identify accused capsules with methoxsalen solution in PEG-fluid-at-room-temp across the specified weight ranges.
- Regimen supplementation for stronger leverage:
- Where available, show that the administered product was followed by a timing interval “sufficient to obtain a peak blood level,” then UV irradiation.
- Claim mapping against weight percent:
- Quantify methoxsalen wt% and PEG wt% in unit dosage formulations.
- Confirm capsule container and solution state.
Key Takeaways
- US 4,454,152 protects (i) a PEG-based oral capsule formulation of methoxsalen in solution and (ii) a treatment method that includes waiting for peak blood level before UV irradiation for psoriasis or vitiligo.
- The formulation scope is driven by tight wt% boundaries: PEG about 10% to about 97.5% and methoxsalen about 0.025% to about 10.5% (Claim 3).
- Claims 2 and 3 are product-centric and do not require UV steps, enabling composition-based infringement theories.
- Claim 1 adds a regimen element, making “peak blood level” sequencing central to method-claim coverage.
FAQs
1) Does US 4,454,152 require a specific UV wavelength?
The provided claim text requires “irradiating the subject with ultraviolet light” but does not specify a wavelength range.
2) Can the patent be triggered by a capsule formulation even if clinicians use a different UV timing?
Yes. Claims 2 and 3 protect the composition in unit dosage form. UV timing is required for Claim 1’s method.
3) Are PEG molecular weights or grades explicitly limited in the claim text provided?
The provided claim text limits the vehicle to PEG or PEG mixtures that are fluid at room temperature, without stating a molecular weight range.
4) What is the narrowest numeric limitation in the claims provided?
For composition Claim 3, the narrowest explicit window is methoxsalen at about 0.025% to about 10.5% by weight (with PEG about 10% to about 97.5% by weight).
5) If a product uses PEG but outside the wt% limits, does it avoid the claims?
If PEG and/or methoxsalen wt% falls outside the stated “about” ranges and the composition is otherwise outside the claim structure (solution in PEG fluid at room temperature in capsule), it is outside the literal numeric boundaries of Claims 2 and 3.
References
[1] US Patent 4,454,152 (claims provided in prompt).
