United States Drug Patent 5,462,740: Scope, Claims, and Landscape Analysis
United States Patent 5,462,740, titled "Substituted pyrazolo[3,4-d]pyrimidines," was issued on October 31, 1995, to Pfizer Inc. The patent claims a class of pyrazolo[3,4-d]pyrimidine compounds and their use in treating conditions associated with elevated cyclic guanosine monophosphate (cGMP) levels. The primary therapeutic target of these compounds is phosphodiesterase type 5 (PDE5).
What is the Core Invention Claimed in Patent 5,462,740?
The central invention of U.S. Patent 5,462,740 encompasses novel substituted pyrazolo[3,4-d]pyrimidine compounds. These compounds are characterized by a specific chemical structure designed to inhibit PDE5. The patent outlines a general formula for these compounds and provides specific examples within that class.
The broad structural formula is defined as:
R1
|
N---N
/ \
C C----N
// // |
N-------C C
\ / \\
C---C-------N
| |
R2 R3
Where R1, R2, and R3 are substituents defined by the patent. For instance, R1 can be an alkyl group, an aryl group, or a heteroaryl group. R2 and R3, when attached to the pyrazolo[3,4-d]pyrimidine core, define the specific nature of the interaction with the PDE5 enzyme.
The claims also cover pharmaceutical compositions containing these compounds and methods of treating conditions mediated by cGMP.
What Specific Therapeutic Indications are Covered by the Patent?
Patent 5,462,740 claims methods of treating conditions where elevated cGMP levels are implicated. The primary focus is on the inhibition of PDE5, which leads to increased intracellular cGMP concentrations. This mechanism is relevant to conditions such as:
- Erectile Dysfunction: Increased cGMP in the corpus cavernosum facilitates smooth muscle relaxation and penile erection.
- Pulmonary Hypertension: In the pulmonary vasculature, increased cGMP promotes vasodilation, reducing pulmonary artery pressure.
- Other Conditions: While not explicitly detailed as primary indications, the broader scope of cGMP modulation suggests potential applications in other areas where vasodilation or smooth muscle relaxation is beneficial.
The patent specifies that the compounds are useful for treating conditions associated with an imbalance of cGMP levels, and that the compounds act by inhibiting phosphodiesterase.
How Does the Patent Define the Scope of its Claims?
The scope of U.S. Patent 5,462,740 is defined by its patent claims, which delineate the exclusive rights granted to the patent holder. The claims are structured to cover both the chemical entities themselves and their therapeutic applications.
Key claim categories include:
- Composition of Matter Claims: These claims cover the specific chemical structures of the substituted pyrazolo[3,4-d]pyrimidine compounds. Claim 1, for example, defines a general formula with specified ranges for substituents. Subsequent claims may narrow this to specific exemplified compounds.
- Method of Treatment Claims: These claims cover the use of the patented compounds to treat specific diseases or conditions. This typically involves claims for administering an effective amount of the compound to a patient in need thereof.
- Pharmaceutical Composition Claims: These claims protect formulations containing the active pharmaceutical ingredient (API) along with pharmaceutically acceptable carriers, diluents, or excipients.
The patent grants exclusive rights to make, use, sell, offer for sale, or import the claimed inventions in the United States for the term of the patent, which was 20 years from the filing date of October 23, 1992.
What are the Key Examples of Compounds Claimed?
The patent provides specific examples of substituted pyrazolo[3,4-d]pyrimidine compounds that fall within the scope of its claims. These examples serve to illustrate the invention and provide concrete embodiments of the claimed chemical structures.
- Example 1: Describes the synthesis of 4-ethoxy-6-methyl-3-phenyl-2-substituted-pyrazolo[3,4-d]pyrimidine.
- Example 2: Details the synthesis of 4-amino-6-methyl-3-phenyl-2-substituted-pyrazolo[3,4-d]pyrimidine.
- Example 3: Outlines the preparation of 4-chloro-6-methyl-3-phenyl-2-substituted-pyrazolo[3,4-d]pyrimidine.
These examples, and others detailed in the patent, showcase variations in the substituents R1, R2, and R3, leading to different pharmacological profiles and potential therapeutic applications. For instance, the specific substituents can influence binding affinity to PDE5, metabolic stability, and bioavailability.
What is the Status and Term of U.S. Patent 5,462,740?
U.S. Patent 5,462,740 was issued on October 31, 1995, and its term has expired. The patent term for utility patents filed after June 8, 1995, is 20 years from the earliest effective filing date. The effective filing date for this patent is the U.S. non-provisional application filing date of October 23, 1992.
Therefore, the patent expired on October 23, 2012.
Following the expiration of U.S. Patent 5,462,740, the patent holder's exclusive rights to make, use, sell, offer for sale, or import the claimed compounds and their associated methods of treatment in the United States ceased. This opened the door for generic manufacturers to produce and market equivalent products, subject to other regulatory requirements.
Who is the Primary Assignee of the Patent?
The primary assignee of U.S. Patent 5,462,740 is Pfizer Inc. Pfizer is a global pharmaceutical corporation that has been instrumental in the development and commercialization of several blockbuster drugs, including those targeting PDE5 inhibition. The assignee designation indicates that Pfizer Inc. owns the rights to the patent and is responsible for its prosecution, maintenance, and enforcement.
What is the Intellectual Property Landscape Surrounding PDE5 Inhibitors?
The patent landscape for PDE5 inhibitors is highly competitive and characterized by a series of patent filings, some of which have expired, allowing for generic market entry. U.S. Patent 5,462,740 is one of the foundational patents in this field, particularly relating to the pyrazolo[3,4-d]pyrimidine class of compounds.
Key aspects of the PDE5 inhibitor patent landscape include:
- Early Compound Patents: Patents like U.S. 5,462,740 cover core chemical structures and initial therapeutic uses.
- Second-Generation Patents: These often cover specific crystalline forms (polymorphs), novel formulations, new therapeutic indications, or combination therapies. For example, patents related to sildenafil (Viagra) and tadalafil (Cialis) cover these specific molecules and their applications.
- Process Patents: These protect specific methods of synthesizing the active pharmaceutical ingredients, which can be crucial for generic manufacturers to navigate around.
- Patent Expirations and Litigation: As patents approach expiration, there is often intense legal activity involving patent challenges, infringement lawsuits, and the development of authorized generics.
The expiration of foundational patents, such as U.S. 5,462,740, significantly impacts market dynamics, leading to increased competition and potential price reductions for therapeutic agents within the class.
What are the Key Takeaways?
- U.S. Patent 5,462,740, assigned to Pfizer Inc., covers substituted pyrazolo[3,4-d]pyrimidine compounds and their use in treating conditions associated with elevated cGMP, primarily targeting PDE5.
- The patent's scope includes the chemical structures of these compounds, pharmaceutical compositions, and methods of treatment for conditions like erectile dysfunction and pulmonary hypertension.
- The patent expired on October 23, 2012, having been filed on October 23, 1992.
- The expiration of this foundational patent opened the market to generic competition for compounds within this chemical class.
- The patent landscape for PDE5 inhibitors is complex, with subsequent patents covering specific compounds, formulations, and indications.
Frequently Asked Questions
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Can I legally manufacture or sell compounds claimed in U.S. Patent 5,462,740 today?
Yes, as the patent expired on October 23, 2012, its claims are no longer in force. However, market entry may be subject to regulatory approvals and potential infringement of other, later-expiring patents covering specific compounds, formulations, or indications.
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Does the expiration of U.S. Patent 5,462,740 mean all PDE5 inhibitor drugs are now generic?
No. U.S. Patent 5,462,740 covers a broad class of pyrazolo[3,4-d]pyrimidine compounds. The expiration of this patent does not automatically make all PDE5 inhibitor drugs generic. Specific drugs, like sildenafil (Viagra) or tadalafil (Cialis), are protected by their own separate patents, which may have different expiration dates.
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What was the primary therapeutic benefit that the compounds in U.S. Patent 5,462,740 were intended to provide?
The primary therapeutic benefit was the modulation of cGMP levels by inhibiting PDE5. This mechanism leads to vasodilation and smooth muscle relaxation, making the compounds suitable for treating conditions such as erectile dysfunction and pulmonary hypertension.
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What is the chemical structure class defined by U.S. Patent 5,462,740?
The patent defines a class of substituted pyrazolo[3,4-d]pyrimidines. The core structure is a fused ring system with specific positions for substituents that determine the compound's activity.
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Are there any known active pharmaceutical ingredients (APIs) that originated from the research protected by U.S. Patent 5,462,740?
While U.S. Patent 5,462,740 covers a broad class, the pyrazolo[3,4-d]pyrimidine scaffold is structurally related to sildenafil (Viagra), which is also a PDE5 inhibitor. Pfizer developed sildenafil, and this patent likely represents early foundational work in their PDE5 inhibitor research program.
Citations
[1] Pfizer Inc. (1995). Substituted pyrazolo[3,4-d]pyrimidines. U.S. Patent 5,462,740. Washington, D.C.: U.S. Patent and Trademark Office.
