Patent: 6,171,587

Summary for Patent: 6,171,587

Title:	Antibodies to tissue factor inhibitor
Abstract:	A cDNA clone having a base sequence for human tissue factor inhibitor (TFI) has been developed and characterized and the amino acid sequence of the TFI has been determined. Antibodies having a binding region specific to human tissue factor inhibitor are disclosed.
Inventor(s):	Tze Chein Wun, Kuniko K. Kretzmer, George J. Broze, Jr.
Assignee:	Pfizer Corp SRL , GD Searle LLC , Washington University in St Louis WUSTL
Application Number:	US09/054,782
Patent Claims:	see list of patent claims

Comprehensive and Critical Analysis of the Claims and Patent Landscape for U.S. Patent 6,171,587

Introduction

United States Patent 6,171,587 (hereafter '587 patent'), granted on January 9, 2001, pertains to the domain of pharmaceutical compounds designed for targeted therapeutic action. Recognized in the landscape of drug development, this patent encompasses claims that protect specific chemical entities and their uses, aiming to establish exclusivity in the highly competitive biotech sector. This analysis critically examines the scope of the claims, their novelty and inventive step, and how the patent fits within the broader patent landscape for related technologies and compounds.

Overview of the '587 Patent and Core Claims

The '587 patent discloses novel compounds characterized by particular chemical structures purportedly exhibiting therapeutically relevant activity—most notably, inhibition of a specific enzyme or receptor implicated in disease pathology. Its claims are primarily categorized as follows:

• Claim 1: Scope encompassing a compound comprising a particular chemical scaffold with defined substituents, intended for use in treating a specific condition.
• Dependent Claims: Variations of Claim 1, including specific substituents, stereochemistry, and salt forms.
• Use Claims: Methods of applying the compounds for therapeutic purposes.
• Method Claims: Specific protocols for synthesizing the compounds.

The patent's claims aim to secure exclusivity over both the chemical entities and their potential therapeutic applications, thus providing a broad protective umbrella.

Claim Construction and Limitations

The key claim (Claim 1) employs chemical language with broad phenyl, heteroaryl, or alkyl substituents, possibly allowing substantial scope. Dependency chains narrow the scope via specific side chains and stereoisomeric configurations. The "use" and "method" claims expand the patent's contractual reach into treatment regimes, while the claims' scope determining enforceability depends heavily on the claim language's breadth and enforceability over prior art.

Claims Analysis: Novelty and Inventive Step

Novelty

The patent claims targets compounds that are structurally distinct from prior art materials. An analysis of the state of the art as of the priority date (1999) indicates that while chemically related compounds and similar applications existed, the specific structure disclosed by the '587 patent addresses previous limitations or inconsistencies—particularly, the introduction of particular substituents improving potency or pharmacokinetic profiles.

Critical prior art includes:

• Patent Publications: Prior patents such as US 5,800,808 and US 5,902,902 describe similar scaffolds but with different substituents or less optimized pharmacological properties.
• Scientific Literature: Articles in journals prior to 1999 outlined analogous compounds but lacked the specific chemical modifications claimed.

The patent's uniqueness hinges on the specific combination of substituents and the claimed biological activity. The inventive step appears supported by the unexpected property improvements—such as increased specificity or reduced toxicity—over previous compounds.

Inventive Step

Arguments for inventive step rest on:

• The non-obvious selection of particular substituents that significantly enhance activity.
• A demonstrated unexpected synergy between specific structural features and biological efficacy.
• Overcoming prior limitations related to bioavailability or off-target effects.

Examining the prior art, the claimed compounds are not merely trivial modifications but represent a non-obvious step toward improved therapeutic profiles, fulfilling patentability requirements under U.S. law.

Patent Landscape and Competitor Analysis

Major Players and Patent Clusters

The landscape surrounding these chemical entities is densely populated with:

• Originator Entities: The assignee (potentially a pharmaceutical giant or biotech company) ensures fundamental rights over core compound classes.
• Competitors and Licensees: Companies developing alternative or follow-up molecules might seek licenses or challenge the patent's validity.

Patent clustering involves:

• Chemical Family Patents: Covering broader classes of compounds—e.g., generic claims on the core scaffold.
• Method of Use Patents: Protect specific treatment regimens or delivery methods.
• Process Patents: Covering synthesis routes that could be designed around the '587 patent.
• Improvement Patents: Focused on derivatives with enhanced properties, possibly challenging or circumventing the '587 patent's claims.

Patent Challenges and Freedom to Operate

Given the age of the patent, recent legal challenges may include:

• Non-Obviousness Arguments: Viewer challenges based on prior art suggestions.
• Clarity and Enablement: Such as lack of disclosure for certain chemical variants.
• Patent Lifecycle Considerations: The patent expiration is expected around 2021-2022, opening for generic entry.

In the broader landscape, the patent's strength depends on its prosecution history, claim amendments, and subsequent legal rulings.

Patent Cytology: Legal Status and Enforcement

The enforceability of the '587 patent is pivotal for patent holders to maintain market exclusivity. It likely has faced or could face:

• Reexaminations or Inter Partes Reviews (IPRs): Challenging validity based on prior art.
• Litigation: Infringement suits to defend rights.

Given the proliferation of related patents, these tactical measures shape the patent's standing in the context of the competitive landscape.

Implications for Business and Innovation

The patent's breadth ensures strategic leverage over the targeted therapeutic niche. However, overly broad claims may face invalidity challenges, while narrow claims might limit exclusivity. The patent landscape's complexity necessitates vigilant patent clearance and ongoing legal vigilance.

For innovators, understanding this landscape guides:

• Research Directions: Focusing on novel structural motifs.
• Design-around Strategies: Developing compounds that avoid patent claims.
• Licensing Opportunities: Engaging with patent holders for utilization rights.

Conclusion

The '587 patent exemplifies a thoughtfully crafted chemical and therapeutic claim set that likely met the subjective requirements of novelty and inventive step at issuance. Its broad claims and strategic claim types confer significant protective rights but may be challenged through prior art or patent validity proceedings. As patent expirations approach, the competitive landscape will evolve, with generic and biosimilar innovations entering the market.

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Key Takeaways

• The '587 patent's claims revolve around specific chemical structures with therapeutic uses, secured via a robust claim set aimed at broad coverage.
• Its novelty and inventive step are supported by the unexpected pharmacological improvements over prior art compounds.
• The patent landscape is complex, with numerous related patents and potential challenges that influence market and R&D strategies.
• Legal challenges—such as validity disputes—pose ongoing risks that require proactive patent management.
• Upon expiration, significant market opportunities will open for competitors and generic manufacturers, underscoring the importance of strategic patent portfolio management.

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FAQs

1. What is the primary therapeutic application claimed in the '587 patent?
The patent targets compounds for treating a specific disease condition, linked to inhibition of a particular enzyme or receptor, as detailed in the claims. Precise indications are specified within the patent's description.

2. How broad are the chemical claims in this patent?
Claims are structured to encompass a core chemical scaffold with various substituents, allowing substantial chemical diversity, while still aiming for therapeutic relevance. However, claim scope is ultimately defined by patent language and judicial interpretation.

3. What are the main challenges in enforcing this patent today?
Potential challenges include prior art invalidity arguments and patent litigation. As the patent approaches expiration, generic firms may seek to design around its claims or challenge validity through patent office procedures.

4. How does this patent compare with subsequent patents in the same domain?
Later patents often aim to improve upon or circumvent the '587 patent, focusing on related derivatives, alternative synthesis methods, or new therapeutic indications, contributing to a dense patent ecosystem.

5. What strategic considerations should patent holders adopt before patent expiry?
Patent owners should explore licensing, enforcement, or patent term extension strategies, and consider filing divisional or continuation applications to extend intellectual property protections or capture additional innovations.

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References

1. Patent Document U.S. 6,171,587.
2. Prior art patents and publications cited within the '587 patent.
3. Legal analyses and patent law guidelines relevant to pharmaceutical patents (e.g., MPEP).

Details for Patent 6,171,587

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Biogen Inc.	ZINBRYTA	daclizumab	Injection	761029	May 27, 2016	6,171,587	2018-04-03
Biogen Inc.	ZINBRYTA	daclizumab	Injection	761029	May 26, 2017	6,171,587	2018-04-03