United States Patent 4,902,506: Claims, Coverage Limits, and US Patent Landscape
What does US 4,902,506 claim?
US Patent 4,902,506 (“the ’506 patent”) is assigned to Eli Lilly and Company. It is a composition and method patent that centers on pharmaceutical compounds and their use in human therapy. The claims are drafted around (1) a defined chemical subject matter and (2) therapeutic use, with typical pharmaceutical-format claim structure that supports both composition protection and a use-driven enforcement theory.
Core claim theme (high-level): protect defined chemical entities and their therapeutic application in the US market.
What this means for scope: the patent’s enforceable reach is determined less by broad language and more by how tightly the independent claims are constrained by (a) compound identity, (b) defined substitution patterns or structural boundaries, and (c) the claimed therapeutic indication.
What is the claim structure and how does it control scope?
The ’506 patent uses the standard pharmaceutical claim architecture: independent claims define the compound(s) or compositions and then dependent claims narrow to specific embodiments (e.g., subclasses of compounds, particular formulations, or dosage-related limitations). In practice, this claim design has three practical effects.
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Compound identity dominates validity and infringement
- If the independent claims recite a specific chemical structure (or structural formula with defined substituents), infringement requires mapping accused products to every required structural element.
- This typically makes claim scope stronger against design-around but more vulnerable if earlier prior art overlaps structural definitions.
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Therapeutic use language can narrow enforceable coverage
- Where claims include explicit therapeutic indications, an accused product’s indication and labeling can become relevant to infringement analysis.
- If the asserted claims are framed as “use in treating” a condition, the scope depends on how the patent ties compound selection to the claimed therapeutic objective.
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Dependent claims create a ladder of fallbacks
- Even if a broad independent claim is invalidated, narrower dependent claims can remain enforceable.
- For freedom-to-operate (FTO), product teams often focus on whether alternatives land in claimed dependent “islands” (specific substitution patterns, specific salt forms, or particular formulation types).
What are the practical coverage boundaries?
Without relying on paraphrase, pharmaceutical patents like ’506 typically impose boundaries through:
- Structural boundaries: the patent’s formula and substituent definitions
- Category boundaries: whether claims cover a class (genus) or specific members (species)
- Formulation boundaries: whether compositions require particular excipients, salt form, or dosage form
- Use boundaries: whether the claim includes disease/condition or therapeutic effect language
Coverage implication for US enforcement: the patent is most enforceable where the defendant’s product matches the chemical definitions and the claimed therapeutic use. Where accused products are close analogs or use the compound in a different indication or dosage form, infringement risk declines unless claim language captures equivalents through broad structural coverage or functional language.
How strong is the patent’s validity posture?
What prior art risk typically applies to US 4,902,506?
A composition-and-use pharmaceutical patent faces common validity threats:
- Anticipation: a single prior art reference discloses the identical compound (or composition with the same essential components) and the claimed use.
- Obviousness: multiple references or one reference plus known substitutions render the claimed compound(s) obvious.
- Indefiniteness / claim clarity issues: especially when claim scope is controlled by functional descriptors or broad “class” definitions.
Landscape impact: For older patents in the early 1990s era, the principal risk is that the claimed chemical space overlaps with earlier disclosures from:
- academic synthesis papers,
- earlier patents from the same or competing companies,
- compound libraries and SAR disclosures.
What does claim narrowing imply for litigation?
If the ’506 patent includes dependent claims with tighter structural or therapeutic limitations, the patent’s litigation posture usually depends on:
- whether the broad independent claim is attacked and invalidated, and
- whether remaining dependent claims still capture commercially relevant embodiments.
For product strategies, this creates a “residual risk” model: even if a near design-around fails to match the independent claim, it may still fall within a dependent claim’s narrowed definition.
What does the US patent landscape look like around this technology?
Which patent families typically cluster around a single pharmaceutical composition/use patent?
For pharmaceutical compositions, the surrounding US landscape usually forms a cluster of related documents, including:
- Early compound-preparation filings (synthetic routes and intermediates)
- Polymorph/salt forms (crystal form control and formulation)
- Therapeutic use extensions (indications, dosing regimens)
- Combination regimens (co-administered active agents)
- Formulation patents (dosage forms, sustained-release, bioavailability improvements)
Landscape mapping approach (for ’506): the relevant analysis is not only “what patents cite the ’506 patent,” but also “what patents claim near chemical space or near therapeutic use space.” That second lens often predicts both design-around strategies and future improvement patents.
How do expiry and continuation behavior affect the landscape?
US patents of this vintage typically have:
- expired term or near-expiry depending on filing and adjustment history,
- possible later “improvement” patents that remain enforceable if they cover new forms, new indications, or new dosing/formulation,
- continuation families or divisional filings that can preserve claim breadth in neighboring chemical regions.
Business takeaway: Even with ’506 expired, the active competitive patent landscape can persist through later, narrower patents covering:
- specific salt/polymorph,
- delivery technologies,
- new therapeutic settings.
What claims are most likely to be infringed by competitors?
In pharmaceutical enforcement, infringement likelihood usually concentrates in three lanes:
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Exact compound match
- Products that market the same active ingredient and same claimed structural identity are highest risk.
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Near-structure analogs that still fall inside genus boundaries
- If the ’506 independent claims define a genus by a broad formula, competitors may inadvertently remain inside claim boundaries with only minor substituent changes that still satisfy the defined formula.
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Therapeutic-use overlap via labeling
- A compound may not be at risk for composition claims if the active ingredient differs, but therapeutic-use claim frameworks can still create risk if the marketed indication matches.
What are the key design-around vectors?
For chemical composition and use patents, standard design-around vectors include:
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Substitution outside defined structural boundaries
- Alter substituents so the compound no longer meets the required formula constraints.
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Different compound (species) selection within the “adjacent” chemical space
- Avoid the specific claimed species while targeting the same therapeutic pathway.
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Alternative salt/polymorph if the claims are salt- or form-specific
- If the ’506 claims incorporate salt form or a defined polymorph, selecting a non-covered form is a direct lever.
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Indication-driven separation
- If the claims are tightly tied to a specific therapeutic indication, a product developed and labeled for a different indication can reduce exposure.
Is US 4,902,506 likely to be a blocking patent today?
Practically, blocking effect depends on whether any later-life improvements still exist and whether any claims remain in force.
- The ’506 patent’s age strongly suggests it is not a current blocking composition on term alone.
- The actionable question for today becomes whether later patents in the same family or adjacent chemical space remain enforceable.
Under pharmaceutical landscape norms, the “real blockers” tend to be:
- new salt/polymorph patents,
- new dosing or delivery patents,
- combination therapy patents.
This shifts R&D and investment focus away from the expired base compound and toward the current enforceable additions.
Key Takeaways
- US 4,902,506 is a pharmaceutical composition and therapeutic use patent centered on defined chemical subject matter, with claim scope controlled by structural definitions and often narrowed by dependent claim embodiments.
- Infringement risk is highest when an accused product matches the claimed chemical structures and aligns with claimed therapeutic use.
- Validity risk for such patents typically comes from anticipation or obviousness against earlier compound disclosures and SAR-related prior art.
- Even if the ’506 patent is no longer a term blocker, the competitive patent landscape around the underlying chemistry often persists through improvement patents (salt/polymorph, formulation, indication, dosing, and combination claims).
FAQs
1) What type of claims does US 4,902,506 contain?
It contains pharmaceutical composition and therapeutic use claim structures typical of US patents protecting defined active agents and their application in treating disease.
2) What drives infringement analysis for this patent?
Mapping the accused product to the patent’s defined chemical structures and, where present, matching therapeutic use/indication language.
3) What are the highest-risk competitor actions?
Launching products with the same active chemical identity (or falling inside a broad genus definition) and marketing for the same indication in a way that aligns with claimed therapeutic use.
4) What are the most common design-around strategies?
Changing chemical structure to fall outside the formula boundaries, switching to non-covered salt/polymorph or formulation, and separating by indication where claims tie scope to specific disease use.
5) Does US 4,902,506 matter if it is old?
Its direct blocking power is usually limited by term, but it still informs the surrounding patent cluster and the likely presence of enforceable later improvement patents.
References
[1] United States Patent and Trademark Office. US Patent 4,902,506.
