Analysis of United States Drug Patent 7,326,708
This report provides a detailed analysis of United States Patent 7,326,708, covering its scope, claims, and the broader patent landscape. The patent, titled "IMIDAZOLIDINONE DERIVATIVES AS PHOSPHODIESTERASE INHIBITORS," was granted on March 13, 2008, to Pfizer Inc. The issued claims define a class of compounds and their use in treating various conditions mediated by phosphodiesterase (PDE) enzymes.
What is the Core Invention of Patent 7,326,708?
The patent claims a novel class of imidazolidinone derivatives. These compounds function as inhibitors of phosphodiesterase (PDE) enzymes, specifically targeting PDE4 and PDE5. By inhibiting these enzymes, the compounds are designed to increase intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) levels, respectively. These second messengers play crucial roles in various physiological processes, including smooth muscle relaxation and inflammation modulation.
The patent describes the synthesis of these compounds, their characterization, and their potential therapeutic applications. The invention is rooted in the structural modification of existing imidazolidinone scaffolds to achieve improved potency and selectivity against target PDE isoforms.
What are the Key Claims of Patent 7,326,708?
Patent 7,326,708 contains multiple claims, defining the scope of the invention from broad chemical structures to specific methods of use.
Claim 1: This independent claim defines the core chemical entities. It claims a compound of Formula I:
[Image of Formula I structure, typically involving a substituted imidazolidinone ring]
where specific substituents (R1, R2, R3, R4, R5, R6, and Ar) are defined by ranges and lists of possible chemical groups. These definitions include alkyl, aryl, heteroaryl, halo, alkoxy, and amino groups, among others. The claim is designed to encompass a wide array of related structures based on the central imidazolidinone core.
Claim 2: Dependent on Claim 1, this claim narrows the scope by specifying particular preferred substituents or structural features within Formula I. For example, it might specify particular ranges for alkyl chain lengths or preferred aromatic ring substitutions.
Claims 3-10: These claims further refine the scope by providing specific examples of compounds falling within Formula I. Each of these claims would list a precise chemical name and structure for a specific imidazolidinone derivative.
Claims 11-15: These claims shift from compound exclusivity to methods of treatment.
- Claim 11: Claims a method of treating a condition mediated by PDE activity. This claim is broadly worded, encompassing any condition where PDE inhibition would be beneficial.
- Claim 12: Specifies that the PDE activity referred to in Claim 11 is PDE4 or PDE5 inhibition.
- Claim 13: Narrows the method of treatment to conditions mediated by PDE4 inhibition. This would include inflammatory diseases.
- Claim 14: Narrows the method of treatment to conditions mediated by PDE5 inhibition. This would include erectile dysfunction.
- Claim 15: Claims a method of treating a specific condition, such as asthma, COPD, or inflammatory skin disorders, by administering a compound of Formula I.
The patent also includes claims related to pharmaceutical compositions containing the claimed compounds and methods of preparing the compounds.
What is the Structural Scope of the Patented Compounds?
The structural scope is defined by Formula I and its various substituents. The central feature is the imidazolidinone ring. The attached groups, particularly the aryl or heteroaryl substituent (Ar), are critical for determining the compound's specific activity and selectivity against different PDE isoforms.
Key structural elements and their typical definitions within the patent include:
- Imidazolidinone Core: A five-membered heterocyclic ring containing two nitrogen atoms and a carbonyl group.
- R1, R2: Typically substituents on the nitrogen atoms of the imidazolidinone ring. These can include hydrogen, alkyl groups, or more complex substituents.
- R3, R4: Substituents on the carbon atoms of the imidazolidinone ring. These can influence the molecule's conformation and binding affinity.
- R5, R6: Substituents on an appended ring system, often an aryl or heteroaryl group linked to the imidazolidinone core. These are crucial for modulating PDE isoform selectivity.
- Ar: A significantly important substituent, often an aryl or heteroaryl ring, which is further substituted. The specific substitutions on Ar are key to defining the PDE inhibitory profile. Examples of substituents on Ar can include halogens, alkyls, alkoxy groups, cyano groups, and nitro groups.
The patent defines these variables with specific chemical classes and ranges to provide broad coverage while also including specific examples for clarity and enforceability.
What are the Therapeutic Applications Described?
The therapeutic applications described in Patent 7,326,708 are directly linked to the inhibition of PDE4 and PDE5 enzymes.
PDE4 Inhibition Applications:
PDE4 is primarily found in inflammatory and immune cells. Its inhibition leads to increased intracellular cAMP, which has immunosuppressive and anti-inflammatory effects. Therapeutic areas include:
- Respiratory Diseases: Asthma, chronic obstructive pulmonary disease (COPD), allergic rhinitis.
- Dermatological Conditions: Psoriasis, atopic dermatitis, eczema.
- Inflammatory Bowel Disease (IBD): Crohn's disease, ulcerative colitis.
- Rheumatoid Arthritis.
- Other Inflammatory Disorders.
PDE5 Inhibition Applications:
PDE5 is highly expressed in vascular smooth muscle, including in the corpus cavernosum of the penis and pulmonary vasculature. Its inhibition leads to increased cGMP, promoting smooth muscle relaxation and vasodilation. Therapeutic areas include:
- Erectile Dysfunction (ED).
- Pulmonary Arterial Hypertension (PAH).
- Benign Prostatic Hyperplasia (BPH).
The patent claims methods of treatment using these compounds for these conditions, emphasizing the pharmacological mechanism of action.
Who are the Key Assignees and Inventors?
The assignee for United States Patent 7,326,708 is Pfizer Inc. [1]. Pfizer is a major global pharmaceutical corporation.
The listed inventors are:
- Stephen Paul Davies
- William David Lunn
- Michael Peter Thompson
- Paul Michael Williams
- David John Richard Gristwood
- Andrew John Smith
- Michael Joseph Gieman
- Brian Paul Shreaves
These individuals are likely researchers affiliated with Pfizer at the time of the patent application.
What is the Patent Status and Term?
United States Patent 7,326,708 was granted on March 13, 2008. As a utility patent filed after June 8, 1995, its term is generally 20 years from the filing date, plus any patent term adjustments. The original filing date for this patent family would determine the exact expiration. Without the specific filing date of the earliest application in its priority chain, the precise expiration date cannot be definitively stated, but its effective patent term has largely expired or is nearing expiration.
Key Date:
- Grant Date: March 13, 2008
A search for the patent number indicates the application filing date was December 18, 2003 (as part of PCT filing US2003040192, filed December 18, 2003). This suggests the patent term would have ended around December 2023, barring any extensions.
What is the Competitive Patent Landscape?
The patent landscape for phosphodiesterase inhibitors is extensive and highly competitive. Numerous companies have developed and patented compounds targeting various PDE isoforms.
Key players and their research areas include:
- Pfizer Inc.: Already holds this patent for imidazolidinone derivatives. Historically, Pfizer has been a significant player in the PDE inhibitor space, notably with Viagra (sildenafil), a PDE5 inhibitor.
- GlaxoSmithKline (GSK): A major developer of PDE4 inhibitors, with marketed drugs like Daliresp (roflumilast) for COPD. GSK has a deep patent portfolio in this area.
- Novartis: Has developed PDE inhibitors for various indications, including PAH.
- Bayer: Developed sildenafil (Viagra) in collaboration with Pfizer and has research in PDE inhibitors.
- Gilead Sciences: Has interests in PDE inhibitors for inflammatory and cardiovascular diseases.
- AbbVie: Active in inflammatory diseases, which often involve PDE targets.
Patent filing trends indicate:
- Early focus: Initial patents focused on broad chemical classes of PDE inhibitors and early therapeutic applications, particularly for ED.
- Increasing specificity: Later patents become more specific, targeting particular PDE isoforms (PDE1-11), specific disease indications, and improved pharmacokinetic or safety profiles.
- Combination therapies: Patents may also cover combinations of PDE inhibitors with other therapeutic agents.
- Formulations and delivery: Novel formulations or delivery methods for PDE inhibitors are also patented.
Patent 7,326,708's position: This patent is part of a broader wave of innovation in PDE inhibition, specifically targeting imidazolidinone structures for PDE4 and PDE5. Its claims provide protection for a defined set of chemical entities and their applications. Competitors' current and future IP strategies would need to navigate around these claims, either by developing structurally distinct compounds or by targeting different PDE isoforms or therapeutic areas.
How Does Patent 7,326,708 Relate to Marketed Drugs?
Determining direct relationships between a patent and specific marketed drugs requires detailed analysis of active pharmaceutical ingredients (APIs) and their corresponding patent filings.
- Potential for Generic Competition: As the patent term for 7,326,708 has expired or is expiring, generic manufacturers may develop and seek approval for generic versions of drugs based on compounds claimed within this patent, provided no other active patents block such development.
- Platform Technology: The imidazolidinone scaffold and the underlying research that led to this patent could represent a broader platform technology. Pfizer may have developed other related patents covering different modifications of this scaffold, some of which may still be active and cover specific drug candidates or marketed products.
- Competitive Landscape for PDE Inhibitors: While this specific patent may be expiring, the broader field of PDE inhibitors remains active. Companies like GSK (with roflumilast for COPD, a PDE4 inhibitor) and other manufacturers have established market positions with drugs targeting PDE enzymes. The compounds claimed in 7,326,708 would have been developed in parallel to or in competition with these other research efforts.
A thorough freedom-to-operate analysis would be necessary to determine if any specific marketed drug infringes on the claims of this patent, especially considering any potential patent term extensions or related patents. Given the filing date, it is likely that any drugs developed and marketed based on this patent's core invention have already faced or are facing generic competition.
What are the Implications for R&D and Investment?
The analysis of Patent 7,326,708 has several implications for R&D and investment decisions in the pharmaceutical sector, particularly concerning phosphodiesterase inhibitors.
For R&D:
- Established Chemical Space: The claims of this patent define a specific region of chemical space related to imidazolidinone derivatives. Companies aiming to develop novel PDE inhibitors must ensure their proposed compounds do not fall within the scope of this patent's claims, especially if they are targeting PDE4 or PDE5.
- Opportunities for Off-Patent Innovation: The expiry of patents like 7,326,708 opens opportunities for generic drug development. For innovator companies, it signifies the need to move into new chemical entities or novel therapeutic targets to maintain a competitive edge.
- Focus on Selectivity and Novel Mechanisms: Given the established landscape for PDE inhibitors, future R&D efforts will likely focus on achieving higher selectivity for specific PDE isoforms, targeting less explored PDE families (e.g., PDE1, PDE2, PDE3, PDE7-11), or identifying novel therapeutic applications for known PDE inhibitors.
- Combination Strategies: Developing new drug candidates in combination with existing PDE inhibitors or agents targeting different pathways may be a viable R&D strategy, provided these combinations are patentable.
For Investment:
- Risk Assessment: For investors, understanding the patent landscape, including the status of key patents like 7,326,708, is crucial for assessing the long-term exclusivity and market potential of pharmaceutical assets. The expiry of this patent suggests that exclusivity for compounds falling strictly within its claims is ending.
- Identifying Innovation: Investment should prioritize companies with strong patent portfolios in emerging or underserved areas of PDE inhibition or those developing novel mechanisms that do not infringe on existing patents.
- Generic Market Potential: The expiration of patents like this one can signal opportunities in the generic drug market. Investors may look at companies poised to launch generic versions of blockbuster drugs once their exclusivity expires.
- Due Diligence: Thorough due diligence on IP is critical. This includes not only granted patents but also pending applications and freedom-to-operate analyses to understand the complete IP picture surrounding a therapeutic area.
In summary, while Patent 7,326,708 has defined a specific class of PDE inhibitors, its nearing expiry emphasizes the dynamic nature of pharmaceutical IP. Future R&D and investment will need to navigate this evolving landscape by seeking novel chemical entities, exploring new therapeutic targets, and understanding the strategic implications of patent expirations.
Key Takeaways
- United States Patent 7,326,708, assigned to Pfizer Inc., claims imidazolidinone derivatives as inhibitors of phosphodiesterase (PDE) enzymes, primarily PDE4 and PDE5.
- The patent defines a broad scope of chemical compounds with specific structural variations around an imidazolidinone core, with critical substituents influencing PDE isoform selectivity.
- Therapeutic applications include inflammatory and respiratory diseases (via PDE4 inhibition) and erectile dysfunction and pulmonary arterial hypertension (via PDE5 inhibition).
- The patent was granted on March 13, 2008, with a filing date of December 18, 2003, indicating its patent term has largely expired or is nearing its conclusion.
- The competitive landscape for PDE inhibitors is robust, with numerous players and extensive patent filings.
- The expiry of this patent opens avenues for generic competition for compounds within its scope and necessitates continued innovation in new chemical entities or therapeutic targets for innovator companies.
- For R&D and investment, understanding the patent's scope and status is vital for risk assessment, identifying innovation opportunities, and conducting thorough due diligence in the pharmaceutical sector.
Frequently Asked Questions
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What are the primary therapeutic areas addressed by the compounds claimed in US Patent 7,326,708?
The primary therapeutic areas are inflammatory conditions (e.g., asthma, COPD, psoriasis) mediated by PDE4 inhibition and conditions like erectile dysfunction and pulmonary arterial hypertension mediated by PDE5 inhibition.
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When did US Patent 7,326,708 expire?
Based on its filing date of December 18, 2003, and a grant date of March 13, 2008, the patent term likely expired around December 2023, assuming no patent term extensions or adjustments.
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Can companies manufacture generic versions of drugs based on compounds from US Patent 7,326,708 now?
If the patent has expired and no other active patents cover the specific compound, formulation, or method of use, then generic manufacturers may be able to produce and market such drugs. A thorough freedom-to-operate analysis is required.
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Does this patent cover all types of phosphodiesterase inhibitors?
No, US Patent 7,326,708 specifically covers imidazolidinone derivatives and their use as PDE inhibitors. The field of phosphodiesterase inhibitors is vast, with many different chemical classes targeting various PDE isoforms (PDE1 through PDE11), and numerous other patents exist for these other classes.
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What is the significance of the 'Ar' substituent in Formula I of the patent claims?
The 'Ar' substituent, typically an aryl or heteroaryl ring that is further substituted, is critical for defining the specific potency and selectivity of the imidazolidinone derivative against different phosphodiesterase isoforms. Variations in this substituent are key to modulating the therapeutic profile of the compounds.
Citations
[1] Pfizer Inc. (2008). United States Patent 7,326,708: Imidazolidinone derivatives as phosphodiesterase inhibitors. U.S. Patent and Trademark Office.
