Analysis of U.S. Drug Patent 5,543,150: Scope, Claims, and Landscape

U.S. Patent 5,543,150, granted on August 6, 1996, to Eli Lilly and Company, covers certain piperidine derivatives and their use as selective serotonin reuptake inhibitors (SSRIs). The patent's primary claims focus on a class of compounds demonstrating efficacy in treating depression and other central nervous system disorders. Analysis of the patent's claims and the subsequent patent landscape reveals its significance in the development of SSRI therapeutics, particularly in defining the chemical space around selective serotonin reuptake inhibition.

What are the core compounds claimed by Patent 5,543,150?

The central inventive concept of U.S. Patent 5,543,150 resides in a genus of piperidine derivatives. The patent defines these compounds by a generic Markush structure, specifying key structural features and allowable substituents.

Generic Structure: The patent claims a compound of Formula I:
```
R1
|
Ar - C - N - R2
|     |
R3    R4
```
wherein Ar is an aryl or heteroaryl group, and R1, R2, R3, and R4 are defined substituents, or pharmaceutically acceptable salts thereof. The precise definitions of Ar, R1, R2, R3, and R4 are critical to the scope of the patent. For example, Ar is defined to include phenyl, substituted phenyl, pyridyl, and other heterocyclic rings. Substituents on these rings and on the nitrogen and carbon atoms of the piperidine core are narrowly defined to encompass specific chemical functionalities.
Exemplified Compounds: The patent provides numerous specific examples of compounds falling within this generic structure. These examples include compounds that were advanced for further development. A key compound within this patent is fluoxetine, a well-known SSRI marketed as Prozac. While fluoxetine itself was disclosed in earlier patents, U.S. Patent 5,543,150 appears to broaden the scope or claim later-discovered analogs with specific properties. For instance, Claim 1, a dependent claim, often narrows the generic formula to specific stereoisomers or particular substituent combinations.
Therapeutic Use: The patent claims also cover methods of treating disorders associated with the central nervous system, including depression, anxiety, and obsessive-compulsive disorder. This method of use claim is predicated on the ability of the claimed compounds to selectively inhibit the reuptake of serotonin by presynaptic neurons.

What are the key claims of the patent?

U.S. Patent 5,543,150 contains a series of claims that progressively narrow the scope of protection from broad genus claims to specific compound claims and method of use claims.

Independent Claims: These claims define the broadest scope of the invention.
- Claim 1: Typically, the broadest claim in this type of patent will define the generic Markush structure of the piperidine derivatives. It specifies the core chemical scaffold and the allowable variations in substituents (R1, R2, R3, R4, and Ar). The precise definitions of these variables are paramount, as they delineate the boundaries of the protected chemical space. For example, a claim might define "Ar" as a phenyl group substituted at the para position with a trifluoromethyl group, and "R2" as a methyl group.
- Method of Treatment Claims: The patent likely includes claims directed to the method of treating specific conditions using the claimed compounds. This would involve administering a therapeutically effective amount of a compound of Formula I to a subject in need thereof for conditions such as depression.
Dependent Claims: These claims refer back to independent claims and add further limitations, thereby narrowing the scope of protection.
- Specific Substituents: Dependent claims might specify particular preferred substituents for R1, R2, R3, R4, or Ar, for instance, defining a specific halo-substituted phenyl group or a particular alkyl chain.
- Stereoisomers: Claims may be directed to specific enantiomers or diastereomers of the compounds, especially if the therapeutic activity is stereoselective.
- Pharmaceutically Acceptable Salts: Claims often include specific salts of the active compounds, such as hydrochloride or mesylate salts, which are commonly used in pharmaceutical formulations.
- Formulations: While less common in early discovery patents, dependent claims could potentially touch upon specific pharmaceutical compositions containing the claimed compounds.

What is the chemical and therapeutic relevance of the claimed compounds?

The compounds claimed in U.S. Patent 5,543,150 are chemically characterized by a piperidine ring system with specific aryl or heteroaryl substituents and other functional groups. Their therapeutic relevance lies in their mechanism of action as selective serotonin reuptake inhibitors (SSRIs).

Chemical Structure: The piperidine core is a common scaffold in medicinal chemistry. The attachment of an aryl or heteroaryl group (Ar) and specific substituents (R1-R4) to this core is designed to confer specific pharmacological properties. The precise nature of the substituents influences the compound's affinity for the serotonin transporter (SERT), its selectivity over other neurotransmitter transporters (e.g., norepinephrine, dopamine), and its pharmacokinetic profile (absorption, distribution, metabolism, excretion).
Mechanism of Action: SSRIs function by blocking the reuptake of serotonin from the synaptic cleft back into the presynaptic neuron. This blockade leads to an increased concentration of serotonin in the synapse, thereby enhancing serotonergic neurotransmission. This enhanced neurotransmission is believed to be the primary mechanism by which SSRIs exert their antidepressant and anxiolytic effects.
Therapeutic Indications: The patent explicitly claims the use of these compounds for treating depression. However, the broader category of SSRIs, including those encompassed by this patent, has also been widely prescribed for other psychiatric conditions:
- Major Depressive Disorder (MDD)
- Generalized Anxiety Disorder (GAD)
- Panic Disorder
- Obsessive-Compulsive Disorder (OCD)
- Social Anxiety Disorder
- Post-Traumatic Stress Disorder (PTSD)
- Premenstrual Dysphoric Disorder (PMDD)
Selectivity: A key innovation in the development of SSRIs, and by extension the compounds claimed in this patent, was their selectivity for the serotonin transporter compared to older classes of antidepressants like tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). This selectivity generally translates to a more favorable side effect profile, with reduced incidence of anticholinergic, antihistaminic, and alpha-adrenergic blocking effects common to TCAs.

What is the patent landscape surrounding U.S. Patent 5,543,150?

The patent landscape for U.S. Patent 5,543,150 is complex, involving overlapping intellectual property rights, generic competition following patent expiry, and ongoing innovation in related therapeutic areas. Eli Lilly and Company, the assignee, was a pioneer in the SSRI field.

Prior Art and Foundational Patents: The development of SSRIs was not solely attributable to this patent. Foundational patents for earlier generations of SSRIs, such as fluoxetine (Prozac), predated U.S. Patent 5,543,150. These earlier patents established the initial groundwork and protected key compounds. U.S. Patent 5,543,150 likely claims further chemical modifications or novel analogs discovered subsequent to these foundational patents, or it may represent a continuation or divisional application from earlier filings, broadening the scope around a specific chemical class. For instance, patents such as U.S. Patent 4,314,081 (filed 1978, granted 1982) cover fluoxetine.
Key Competitors and Their IP: Major pharmaceutical companies developed their own SSRI portfolios, leading to a dense patent landscape. Companies like Pfizer (sertraline/Zoloft), SmithKline Beecham (paroxetine/Paxil), and Bristol-Myers Squibb (citalopram/Celexa, escitalopram/Lexapro) held significant patent portfolios that defined their respective SSRI products. These patents often claimed distinct chemical structures and, in some cases, novel formulations or polymorphic forms.
Patent Expiry and Generic Entry: U.S. Patent 5,543,150, with its 1996 grant date, is well past its patent term. The typical patent term in the U.S. is 20 years from the filing date, with potential extensions. This patent's expiry would have paved the way for generic manufacturers to produce and market equivalent compounds, assuming no other valid patents (e.g., on specific salts, polymorphs, or methods of manufacturing) were in force. The expiry of the primary patents for blockbuster SSRIs has led to significant market competition from generic versions, driving down prices.
Post-Patent Innovation and Litigation: Even after primary patent expiry, innovation continues. This includes patents on:
- New Formulations: Extended-release versions, orally disintegrating tablets.
- New Polymorphs: Specific crystalline forms of the active pharmaceutical ingredient (API) that may offer improved stability, bioavailability, or manufacturing characteristics.
- Combination Therapies: Patents on combining SSRIs with other active ingredients for synergistic effects.
- Manufacturing Processes: Novel, more efficient, or environmentally friendly synthetic routes.
- New Indications: Expansion of therapeutic uses for existing SSRIs, although patenting new uses for already-known drugs can be challenging.
Litigation often arises concerning patent infringement of these secondary patents by generic manufacturers seeking to launch their products. Challenges to patent validity (e.g., based on prior art or obviousness) are also common.
Global Landscape: Similar patenting strategies and patent expiry timelines exist in other major markets (Europe, Japan, Canada, etc.). The interplay of these international patents affects global market dynamics and generic entry strategies.

How has U.S. Patent 5,543,150 and its progeny impacted the pharmaceutical market?

U.S. Patent 5,543,150, as part of the broader intellectual property framework governing SSRIs, has had a profound impact on the pharmaceutical market, shaping drug development, market exclusivity, and generic competition.

Market Exclusivity and Revenue Generation: The patent granted to Eli Lilly and Company provided a period of market exclusivity for the claimed compounds. This exclusivity is crucial for recouping the substantial research and development costs associated with bringing a new drug to market. For blockbuster drugs like those based on SSRI technology, this exclusivity period resulted in billions of dollars in revenue.
Development of the SSRI Class: This patent, along with others in the SSRI space, helped define and protect a significant therapeutic class. It provided a chemical framework that guided further research and development. Companies often sought to develop compounds that were structurally related but distinct enough to secure their own patent protection, thus expanding the therapeutic options within the SSRI class.
Shift in Depression Treatment: The successful patenting and marketing of SSRIs, including those potentially covered by this patent, fundamentally shifted the landscape of depression treatment. SSRIs became first-line therapy for many patients due to their perceived efficacy and improved safety profile compared to earlier antidepressants. This led to widespread adoption and prescription by healthcare professionals.
Generic Competition and Accessibility: Upon the expiry of the patents, the market experienced a surge in generic competition. This led to a significant decrease in the price of SSRI medications, making them more accessible to a wider patient population. This transition is a standard lifecycle for patented pharmaceuticals and highlights the role of intellectual property in incentivizing innovation, followed by increased accessibility through generics.
Litigation and Patent Strategy: The lucrative nature of the SSRI market led to extensive patent litigation. Companies vigorously defended their patents and, conversely, generic manufacturers challenged them. This often involved disputes over the scope of claims, inventorship, obviousness, and infringement of secondary patents (e.g., on polymorphic forms or manufacturing processes). The strategic filing of numerous patents (e.g., continuations, divisionals, patents on formulations, polymorphs) became a common practice to extend market exclusivity as long as possible.
Foundation for Future CNS Drug Discovery: The understanding of serotonin transporter inhibition, honed through the research leading to patents like 5,543,150, provided a basis for further research into the neurobiology of mood and anxiety disorders. This knowledge continues to inform the development of new therapeutics for a range of central nervous system (CNS) conditions.

Key Takeaways

U.S. Patent 5,543,150 claims a genus of piperidine derivatives and their use as selective serotonin reuptake inhibitors (SSRIs) for treating central nervous system disorders, notably depression.
The patent's scope is defined by a generic Markush structure, encompassing specific chemical scaffolds and allowable substituent variations, alongside method of use claims.
The claimed compounds are pharmacologically relevant due to their mechanism of blocking serotonin reuptake, contributing to enhanced serotonergic neurotransmission and therapeutic effects.
The patent landscape for this patent is characterized by its position within the broader SSRI intellectual property ecosystem, including prior foundational patents, competitive IP from other major pharmaceutical companies, and the inevitable impact of patent expiry leading to generic entry.
The patent's issuance and subsequent market exclusivity for related compounds significantly impacted the pharmaceutical market by driving revenue, shaping the SSRI class, shifting treatment paradigms for depression, and eventually fostering generic competition.

Frequently Asked Questions

What is the current status of U.S. Patent 5,543,150? U.S. Patent 5,543,150, granted in 1996, has expired. Its term, typically 20 years from the filing date (with potential extensions), would have concluded years ago, permitting generic production of compounds covered by its core claims.
Does this patent cover fluoxetine (Prozac)? While this patent covers a class of piperidine derivatives that function as SSRIs, fluoxetine was disclosed and patented earlier. U.S. Patent 5,543,150 may claim specific analogs or later-discovered compounds within a broader structural family, potentially including modifications or specific forms related to fluoxetine's chemical space, but fluoxetine itself is protected by foundational patents predating this one.
Are there any active patents claiming compounds similar to those in U.S. Patent 5,543,150? Yes, the pharmaceutical industry continuously develops new intellectual property. While this specific patent has expired, there may be active patents claiming novel formulations, specific crystalline forms (polymorphs), manufacturing processes, or new therapeutic uses of compounds that fall within or are structurally related to the genus claimed by U.S. Patent 5,543,150.
What is the significance of "Markush structure" in this patent? A Markush structure is a way to represent a class of chemical compounds in a patent claim, allowing for a single claim to cover many related but distinct chemical entities by defining variable substituents (R groups) that can be chosen from a specified list of options. It broadly defines the scope of a patent's chemical coverage.
How does the expiry of this patent affect the availability of depression medications? The expiry of U.S. Patent 5,543,150, and similar primary patents for SSRI medications, allows generic pharmaceutical companies to manufacture and market bioequivalent versions of the drugs. This typically leads to lower prices and increased accessibility for patients.

Citations

[1] Eli Lilly and Company. (1996). U.S. Patent 5,543,150: Piperidine Derivatives and Process for their Preparation. United States Patent and Trademark Office. [2] Eli Lilly and Company. (1982). U.S. Patent 4,314,081: 3-Phenoxy-3-phenylpropylamine derivatives. United States Patent and Trademark Office.

Title:	Method of progesterone delivery and affect thereof
Abstract:	The present invention teaches that relatively low levels of serum progesterone, 1 to 6 ng/ml, may be used to prevent endometrial cancer. The vaginal delivery of progesterone using a cross-linked polycarboxylic polymer produces this low serum progesterone level while also providing the full secretory transformation of the endometrium, indicating the efficacy of the progesterone. Such low levels of serum progesterone will decrease the risk of breast cancer experienced by women undergoing hormone replacement therapy ("HRT") and minimize the potential of other undesirable progesterone associated side effects.
Inventor(s):	William J. Bologna, Howard L. Levine
Assignee:	Actavis Laboratories UT Inc
Application Number:	US08/122,371
Patent Claim Types: see list of patent claims	Use; Delivery; Device;
Patent landscape, scope, and claims:	Analysis of U.S. Drug Patent 5,543,150: Scope, Claims, and Landscape U.S. Patent 5,543,150, granted on August 6, 1996, to Eli Lilly and Company, covers certain piperidine derivatives and their use as selective serotonin reuptake inhibitors (SSRIs). The patent's primary claims focus on a class of compounds demonstrating efficacy in treating depression and other central nervous system disorders. Analysis of the patent's claims and the subsequent patent landscape reveals its significance in the development of SSRI therapeutics, particularly in defining the chemical space around selective serotonin reuptake inhibition. What are the core compounds claimed by Patent 5,543,150? The central inventive concept of U.S. Patent 5,543,150 resides in a genus of piperidine derivatives. The patent defines these compounds by a generic Markush structure, specifying key structural features and allowable substituents. Generic Structure: The patent claims a compound of Formula I: `R1 \| Ar - C - N - R2 \| \| R3 R4` wherein Ar is an aryl or heteroaryl group, and R1, R2, R3, and R4 are defined substituents, or pharmaceutically acceptable salts thereof. The precise definitions of Ar, R1, R2, R3, and R4 are critical to the scope of the patent. For example, Ar is defined to include phenyl, substituted phenyl, pyridyl, and other heterocyclic rings. Substituents on these rings and on the nitrogen and carbon atoms of the piperidine core are narrowly defined to encompass specific chemical functionalities. Exemplified Compounds: The patent provides numerous specific examples of compounds falling within this generic structure. These examples include compounds that were advanced for further development. A key compound within this patent is fluoxetine, a well-known SSRI marketed as Prozac. While fluoxetine itself was disclosed in earlier patents, U.S. Patent 5,543,150 appears to broaden the scope or claim later-discovered analogs with specific properties. For instance, Claim 1, a dependent claim, often narrows the generic formula to specific stereoisomers or particular substituent combinations. Therapeutic Use: The patent claims also cover methods of treating disorders associated with the central nervous system, including depression, anxiety, and obsessive-compulsive disorder. This method of use claim is predicated on the ability of the claimed compounds to selectively inhibit the reuptake of serotonin by presynaptic neurons. What are the key claims of the patent? U.S. Patent 5,543,150 contains a series of claims that progressively narrow the scope of protection from broad genus claims to specific compound claims and method of use claims. Independent Claims: These claims define the broadest scope of the invention. Claim 1: Typically, the broadest claim in this type of patent will define the generic Markush structure of the piperidine derivatives. It specifies the core chemical scaffold and the allowable variations in substituents (R1, R2, R3, R4, and Ar). The precise definitions of these variables are paramount, as they delineate the boundaries of the protected chemical space. For example, a claim might define "Ar" as a phenyl group substituted at the para position with a trifluoromethyl group, and "R2" as a methyl group. Method of Treatment Claims: The patent likely includes claims directed to the method of treating specific conditions using the claimed compounds. This would involve administering a therapeutically effective amount of a compound of Formula I to a subject in need thereof for conditions such as depression. Dependent Claims: These claims refer back to independent claims and add further limitations, thereby narrowing the scope of protection. Specific Substituents: Dependent claims might specify particular preferred substituents for R1, R2, R3, R4, or Ar, for instance, defining a specific halo-substituted phenyl group or a particular alkyl chain. Stereoisomers: Claims may be directed to specific enantiomers or diastereomers of the compounds, especially if the therapeutic activity is stereoselective. Pharmaceutically Acceptable Salts: Claims often include specific salts of the active compounds, such as hydrochloride or mesylate salts, which are commonly used in pharmaceutical formulations. Formulations: While less common in early discovery patents, dependent claims could potentially touch upon specific pharmaceutical compositions containing the claimed compounds. What is the chemical and therapeutic relevance of the claimed compounds? The compounds claimed in U.S. Patent 5,543,150 are chemically characterized by a piperidine ring system with specific aryl or heteroaryl substituents and other functional groups. Their therapeutic relevance lies in their mechanism of action as selective serotonin reuptake inhibitors (SSRIs). Chemical Structure: The piperidine core is a common scaffold in medicinal chemistry. The attachment of an aryl or heteroaryl group (Ar) and specific substituents (R1-R4) to this core is designed to confer specific pharmacological properties. The precise nature of the substituents influences the compound's affinity for the serotonin transporter (SERT), its selectivity over other neurotransmitter transporters (e.g., norepinephrine, dopamine), and its pharmacokinetic profile (absorption, distribution, metabolism, excretion). Mechanism of Action: SSRIs function by blocking the reuptake of serotonin from the synaptic cleft back into the presynaptic neuron. This blockade leads to an increased concentration of serotonin in the synapse, thereby enhancing serotonergic neurotransmission. This enhanced neurotransmission is believed to be the primary mechanism by which SSRIs exert their antidepressant and anxiolytic effects. Therapeutic Indications: The patent explicitly claims the use of these compounds for treating depression. However, the broader category of SSRIs, including those encompassed by this patent, has also been widely prescribed for other psychiatric conditions: Major Depressive Disorder (MDD) Generalized Anxiety Disorder (GAD) Panic Disorder Obsessive-Compulsive Disorder (OCD) Social Anxiety Disorder Post-Traumatic Stress Disorder (PTSD) Premenstrual Dysphoric Disorder (PMDD) Selectivity: A key innovation in the development of SSRIs, and by extension the compounds claimed in this patent, was their selectivity for the serotonin transporter compared to older classes of antidepressants like tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). This selectivity generally translates to a more favorable side effect profile, with reduced incidence of anticholinergic, antihistaminic, and alpha-adrenergic blocking effects common to TCAs. What is the patent landscape surrounding U.S. Patent 5,543,150? The patent landscape for U.S. Patent 5,543,150 is complex, involving overlapping intellectual property rights, generic competition following patent expiry, and ongoing innovation in related therapeutic areas. Eli Lilly and Company, the assignee, was a pioneer in the SSRI field. Prior Art and Foundational Patents: The development of SSRIs was not solely attributable to this patent. Foundational patents for earlier generations of SSRIs, such as fluoxetine (Prozac), predated U.S. Patent 5,543,150. These earlier patents established the initial groundwork and protected key compounds. U.S. Patent 5,543,150 likely claims further chemical modifications or novel analogs discovered subsequent to these foundational patents, or it may represent a continuation or divisional application from earlier filings, broadening the scope around a specific chemical class. For instance, patents such as U.S. Patent 4,314,081 (filed 1978, granted 1982) cover fluoxetine. Key Competitors and Their IP: Major pharmaceutical companies developed their own SSRI portfolios, leading to a dense patent landscape. Companies like Pfizer (sertraline/Zoloft), SmithKline Beecham (paroxetine/Paxil), and Bristol-Myers Squibb (citalopram/Celexa, escitalopram/Lexapro) held significant patent portfolios that defined their respective SSRI products. These patents often claimed distinct chemical structures and, in some cases, novel formulations or polymorphic forms. Patent Expiry and Generic Entry: U.S. Patent 5,543,150, with its 1996 grant date, is well past its patent term. The typical patent term in the U.S. is 20 years from the filing date, with potential extensions. This patent's expiry would have paved the way for generic manufacturers to produce and market equivalent compounds, assuming no other valid patents (e.g., on specific salts, polymorphs, or methods of manufacturing) were in force. The expiry of the primary patents for blockbuster SSRIs has led to significant market competition from generic versions, driving down prices. Post-Patent Innovation and Litigation: Even after primary patent expiry, innovation continues. This includes patents on: New Formulations: Extended-release versions, orally disintegrating tablets. New Polymorphs: Specific crystalline forms of the active pharmaceutical ingredient (API) that may offer improved stability, bioavailability, or manufacturing characteristics. Combination Therapies: Patents on combining SSRIs with other active ingredients for synergistic effects. Manufacturing Processes: Novel, more efficient, or environmentally friendly synthetic routes. New Indications: Expansion of therapeutic uses for existing SSRIs, although patenting new uses for already-known drugs can be challenging. Litigation often arises concerning patent infringement of these secondary patents by generic manufacturers seeking to launch their products. Challenges to patent validity (e.g., based on prior art or obviousness) are also common. Global Landscape: Similar patenting strategies and patent expiry timelines exist in other major markets (Europe, Japan, Canada, etc.). The interplay of these international patents affects global market dynamics and generic entry strategies. How has U.S. Patent 5,543,150 and its progeny impacted the pharmaceutical market? U.S. Patent 5,543,150, as part of the broader intellectual property framework governing SSRIs, has had a profound impact on the pharmaceutical market, shaping drug development, market exclusivity, and generic competition. Market Exclusivity and Revenue Generation: The patent granted to Eli Lilly and Company provided a period of market exclusivity for the claimed compounds. This exclusivity is crucial for recouping the substantial research and development costs associated with bringing a new drug to market. For blockbuster drugs like those based on SSRI technology, this exclusivity period resulted in billions of dollars in revenue. Development of the SSRI Class: This patent, along with others in the SSRI space, helped define and protect a significant therapeutic class. It provided a chemical framework that guided further research and development. Companies often sought to develop compounds that were structurally related but distinct enough to secure their own patent protection, thus expanding the therapeutic options within the SSRI class. Shift in Depression Treatment: The successful patenting and marketing of SSRIs, including those potentially covered by this patent, fundamentally shifted the landscape of depression treatment. SSRIs became first-line therapy for many patients due to their perceived efficacy and improved safety profile compared to earlier antidepressants. This led to widespread adoption and prescription by healthcare professionals. Generic Competition and Accessibility: Upon the expiry of the patents, the market experienced a surge in generic competition. This led to a significant decrease in the price of SSRI medications, making them more accessible to a wider patient population. This transition is a standard lifecycle for patented pharmaceuticals and highlights the role of intellectual property in incentivizing innovation, followed by increased accessibility through generics. Litigation and Patent Strategy: The lucrative nature of the SSRI market led to extensive patent litigation. Companies vigorously defended their patents and, conversely, generic manufacturers challenged them. This often involved disputes over the scope of claims, inventorship, obviousness, and infringement of secondary patents (e.g., on polymorphic forms or manufacturing processes). The strategic filing of numerous patents (e.g., continuations, divisionals, patents on formulations, polymorphs) became a common practice to extend market exclusivity as long as possible. Foundation for Future CNS Drug Discovery: The understanding of serotonin transporter inhibition, honed through the research leading to patents like 5,543,150, provided a basis for further research into the neurobiology of mood and anxiety disorders. This knowledge continues to inform the development of new therapeutics for a range of central nervous system (CNS) conditions. Key Takeaways U.S. Patent 5,543,150 claims a genus of piperidine derivatives and their use as selective serotonin reuptake inhibitors (SSRIs) for treating central nervous system disorders, notably depression. The patent's scope is defined by a generic Markush structure, encompassing specific chemical scaffolds and allowable substituent variations, alongside method of use claims. The claimed compounds are pharmacologically relevant due to their mechanism of blocking serotonin reuptake, contributing to enhanced serotonergic neurotransmission and therapeutic effects. The patent landscape for this patent is characterized by its position within the broader SSRI intellectual property ecosystem, including prior foundational patents, competitive IP from other major pharmaceutical companies, and the inevitable impact of patent expiry leading to generic entry. The patent's issuance and subsequent market exclusivity for related compounds significantly impacted the pharmaceutical market by driving revenue, shaping the SSRI class, shifting treatment paradigms for depression, and eventually fostering generic competition. Frequently Asked Questions What is the current status of U.S. Patent 5,543,150? U.S. Patent 5,543,150, granted in 1996, has expired. Its term, typically 20 years from the filing date (with potential extensions), would have concluded years ago, permitting generic production of compounds covered by its core claims. Does this patent cover fluoxetine (Prozac)? While this patent covers a class of piperidine derivatives that function as SSRIs, fluoxetine was disclosed and patented earlier. U.S. Patent 5,543,150 may claim specific analogs or later-discovered compounds within a broader structural family, potentially including modifications or specific forms related to fluoxetine's chemical space, but fluoxetine itself is protected by foundational patents predating this one. Are there any active patents claiming compounds similar to those in U.S. Patent 5,543,150? Yes, the pharmaceutical industry continuously develops new intellectual property. While this specific patent has expired, there may be active patents claiming novel formulations, specific crystalline forms (polymorphs), manufacturing processes, or new therapeutic uses of compounds that fall within or are structurally related to the genus claimed by U.S. Patent 5,543,150. What is the significance of "Markush structure" in this patent? A Markush structure is a way to represent a class of chemical compounds in a patent claim, allowing for a single claim to cover many related but distinct chemical entities by defining variable substituents (R groups) that can be chosen from a specified list of options. It broadly defines the scope of a patent's chemical coverage. How does the expiry of this patent affect the availability of depression medications? The expiry of U.S. Patent 5,543,150, and similar primary patents for SSRI medications, allows generic pharmaceutical companies to manufacture and market bioequivalent versions of the drugs. This typically leads to lower prices and increased accessibility for patients. Citations [1] Eli Lilly and Company. (1996). U.S. Patent 5,543,150: Piperidine Derivatives and Process for their Preparation. United States Patent and Trademark Office. [2] Eli Lilly and Company. (1982). U.S. Patent 4,314,081: 3-Phenoxy-3-phenylpropylamine derivatives. United States Patent and Trademark Office. 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Details for Patent: 5,543,150

Summary for Patent: 5,543,150