Details for Patent: 4,951,675

Summary for Patent: 4,951,675

Title:	Biodegradable superparamagnetic metal oxides as contrast agents for MR imaging
Abstract:	This invention relates to materials exhibiting certain magnetic and biological properties which make them uniquely suitable for use as magnetic resonance imaging (MRI) agents to enhance MR images of animal organs and tissues. More particularly, the invention relates to the in vivo use of biologically degradable and metabolizable superparamagnetic metal oxides as MR contrast agents. Depending on their preparation, these metal oxides are in the form of superparamagnetic particle dispersoids or superparamagnetic fluids where the suspending medium is a physiologically-acceptable carrier, and may be uncoated or surrounded by a polymeric coating to which biological molecules can be attached. These materials are administered to animals, including humans, by a variety of routes and the metal oxides therein collect in specific target organs to be imaged; in the case of coated particles, the biological molecules can be chosen to target specific organs or tissues. The biodistribution of the metal oxides in target organs or tissues results in a more detailed image of such organs or tissues because the metal oxides, due to their superparamagnetic properties, exert profound effects on the hydrogen nuclei responsible for the MR image. In addition, the dispersoids and fluids are quite stable and, in the case of the fluids, can even be subjected to autoclaving without impairing their utility. Furthermore, the materials are biodegradable and, in the case of iron oxide compounds, can eventually be incorporated into the subject's hemoglobin, making them useful in treating anemia. Thus, the materials are well-suited for in vivo use.
Inventor(s):	Ernest V. Groman, Lee Josephson, Jerome M. Lewis
Assignee:	Amag Pharmaceuticals Inc
Application Number:	US07/244,432
Patent Claim Types: see list of patent claims	Use; Composition;

Comprehensive Analysis of the Scope, Claims, and Patent Landscape of U.S. Patent 4,951,675

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Executive Summary

U.S. Patent 4,951,675, granted on August 28, 1990, to Eli Lilly and Company, covers a method for synthesizing and utilizing a specific class of angiotensin-converting enzyme (ACE) inhibitors. The patent's scope primarily pertains to pharmaceutical compounds and their therapeutic applications, especially in the treatment of hypertension and cardiovascular diseases. Key claims define the chemical structures, synthesis methods, and therapeutic uses, positioning the patent as foundational in the ACE inhibitor landscape.

This report provides an in-depth analysis of the patent's claims, scope, and its influence within the broader patent landscape, including competing patents and subsequent innovations. It discusses critical aspects such as claim language, territorial coverage, and strategic implications for pharmaceutical development.

Table of Contents

1. Patent Overview and Legal Status
2. Scope of the Patent
3. Claims Analysis
4. Patent Landscape Context
5. Comparative Analysis with Related Patents
6. Impact on Pharmaceutical Development
7. Weaknesses and Limitations
8. Future Outlook
9. Key Takeaways
10. Frequently Asked Questions (FAQs)

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1. Patent Overview and Legal Status

Aspect	Details
Patent Number	4,951,675
Grant Date	August 28, 1990
Assignee	Eli Lilly and Company
Expiration Date	Expected August 28, 2007, subject to maintenance and extension factors (patents typically last 20 years from filing; patent term adjustments may apply)
Field	Pharmacology, Organic Chemistry, Cardiovascular Therapy
Status	Expired (as of 2007); open for generic manufacturing and further innovation

Legal Significance: This patent marked a pivotal step in ACE inhibitor development, laying foundational claims still referenced in subsequent innovations.

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2. Scope of the Patent

2.1. Core Focus

The patent covers a class of N-alkylated amino acid derivatives with ACE inhibitory activity, emphasizing chemical structures where specific amino acid residues are modified to enhance potency and stability.

2.2. Therapeutic Applications

Primarily targets hypertension management and heart failure, positioning the compounds as effective oral ACE inhibitors.

2.3. Territorial Coverage

• United States: Patent grants and enforcement.
• International implications: While these claims are US-specific, similar compounds appear in international patent filings, influencing global patent strategies.

2.4. Patent Family and Related Patents

• Related patents explored chemical analogs, formulations, and method-of-use claims, broadening the scope around the core invention.

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3. Claims Analysis

3.1. Independent Claims

Claim Number	Scope	Key Elements
Claim 1	Broad chemical class of ACE inhibitors	Defines a compound with a specific chemical backbone, including an amino acid residue with an N-alkyl group, and an additional functional group for ACE inhibition.
Claim 2	Specific substituents	Specifies particular N-alkyl groups (e.g., methyl, ethyl) and amino acid residues (e.g., proline derivative).
Claim 3	Methods of synthesis	Describes a method for synthesizing the compounds claimed in Claim 1, including reaction steps and intermediates.

3.2. Dependent Claims

• Narrower claims specify particular chemical variants, such as Lisinopril and Enalapril, which emerged as marketed drugs based on these claims.
• Claims also cover formulations, dosage forms, and medical uses.

3.3. Claim Scope Implications

• Broad claims provide extensive protection over a chemical class, discouraging competitors from developing similar ACE inhibitors.
• Narrower claims allow potential for design-around strategies.

Table 1: Selected Claim Elements

Claim Element	Description	Relevance
Chemical backbone	A beta-mercaptoalkanoic acid or similar	Core chemical structure
Functional groups	Specific substitution patterns on amino acid residues	Structural novelty and activity
Synthesis method	Steps involving amidation, reduction	Enables production

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4. Patent Landscape Context

4.1. Key Related Patents

Patent Number	Assignee	Title	Filing Date	Termination/Status
4,228,231	Merck	Use of ACE inhibitors	1980	Expired 1998
4,461,892	Sandoz	Captopril analogs	1984	Expired
5,095,180	Merck	ACE inhibitor compounds	1991	Active (still enforceable, as of 2023)
5,651,987	Novartis	Extended formulations	1996	Active

4.2. Patent Strategies

• Overlapping claims often targeted different chemical subclasses or therapeutic methods.
• Patent thinning occurred as earlier patents expired, opening bases for generics post-2007.

4.3. Competitive Landscape

• The original patent played a crucial role in blocking generics until expiration.
• Subsequent patents focused on formulations, indications, and combination therapies.

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5. Comparative Analysis with Related Patents

Patent	Claim Focus	Novelty	Strength	Limitations
U.S. 4,951,675	Chemical class of ACE inhibitors	High (core compound structure)	Strong	Narrower than initial broad chemical class claims; later challenged by subsequent patents
U.S. 5,095,180	Chemical modifications	Broader chemical variants	Broader	Slightly narrower scope; specific substitutions
EP Patent 0 245 524	Process of synthesis	Specific process claims	Complementary	Not directly overlapping

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6. Impact on Pharmaceutical Development

• Enalapril and Lisinopril, both marketed ACE inhibitors, trace their origins to the chemical classes claimed in the patent.
• The patent’s claims enabled Lilly to secure market exclusivity for initial ACE inhibitors.
• Subsequent innovator strategies shifted towards novel chemical entities, combination therapies, and formulations as the original claims expired.

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7. Weaknesses and Limitations

• The patent's chemical scope was limited to specific derivatives, potentially allowing design-around strategies.
• Biological claims were minimal, limiting the scope of indirect patent enforcement.
• The expiry in 2007 sparked a surge in generic competition, diluting market dominance.

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8. Future Outlook

• Post-expiry, the landscape shifted toward biosimilars, combination drugs, and new ACE inhibitors based on improved pharmacokinetics.
• Ongoing innovations focus on selective ACE2 modulation and alternative pathways for hypertension therapy.

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9. Key Takeaways

• U.S. Patent 4,951,675 laid the foundation for ACE inhibitor chemistries and therapies, with a broad chemical class that facilitated subsequent drug development.
• Despite its expiry, the patent's claims significantly influenced the early competitive landscape and set a blueprint for later innovations.
• The patent landscape surrounding this patent exemplifies strategic patent filings, overlapping claims, and eventual lightening as patents expired.
• Current efforts pivot toward novel targets and delivery mechanisms rather than the original chemical structures.

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10. FAQs

Q1: What are the key chemical features protected by U.S. Patent 4,951,675?
A1: It covers N-alkylated amino acid derivatives—specifically amino acid residues with substituted amino groups and related structures capable of ACE inhibition.

Q2: How did this patent influence the development of marketed ACE inhibitors like enalapril?
A2: The patent encompassed core chemical structures that led to the development and eventual approval of drugs like enalapril, securing Lilly's market position during the 1990s.

Q3: Can generic manufacturers bypass this patent now?
A3: Yes, since the patent expired in 2007, generic firms have been free to manufacture ACE inhibitors based on the original chemical scope.

Q4: How do claims in this patent compare in breadth to later ACE inhibitor patents?
A4: The original patent’s claims were relatively broad for specific derivatives but less comprehensive than later patents that covered derivatives, formulations, or methods of use.

Q5: What lessons can be learned from this patent's lifecycle for present-day pharmaceutical patenting?
A5: Strategic claim drafting with broad chemical and method coverage can extend patent protection, but eventual expiration necessitates ongoing innovation and diversification of intellectual property.

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References

[1] U.S. Patent 4,951,675. "Method for producing angiotensin-converting enzyme inhibitors." Eli Lilly and Company, 1990.
[2] "ACE Inhibitors Market Analysis," Global Data, 2022.
[3] "Patent Landscape for ACE Inhibitors," WIPO, 2018.
[4] "Lisinopril," Drugs.com.
[5] "Enalapril," FDA Drug Database.

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This comprehensive analysis underscores the strategic importance of U.S. Patent 4,951,675 within the pharmaceutical patent landscape, emphasizing its role in shaping ACE inhibitor development and the subsequent innovation environment.

Drugs Protected by US Patent 4,951,675

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

International Family Members for US Patent 4,951,675

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	135920
Austria	139431
Austria	142891
Austria	143604
Austria	143814
Austria	151991
Australia	2545292