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Patent landscape, scope, and claims: |
Patent Analysis: U.S. Drug Patent 5,637,320
U.S. Patent 5,637,320, titled "Substituted 3-phenylpropylamine derivatives," was granted on June 10, 1997, to Pfizer Inc. The patent claims a class of chemical compounds and their use in treating various conditions.
What Compounds Are Claimed by U.S. Patent 5,637,320?
The patent's primary claims focus on a broad chemical genus of substituted 3-phenylpropylamine derivatives. These compounds share a core structure with specific variations at defined positions.
Claim 1: The Core Composition of Matter
Claim 1, the broadest composition of matter claim, defines the fundamental chemical structure and its permissible substituents. It covers compounds of the formula:
R1
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Ar - CH2 - CH2 - CH - NH2
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R2
Where:
- Ar is a phenyl group, which may be substituted with one or two substituents selected from the group consisting of lower alkyl, lower alkoxy, halo, nitro, and trifluoromethyl.
- R1 is selected from the group consisting of lower alkyl, halo, hydroxy, lower alkoxy, trifluoromethyl, and cyano.
- R2 is selected from the group consisting of phenyl, substituted phenyl, and 2-, 3-, or 4-pyridyl.
The patent provides specific examples of compounds falling within this general formula. These include, but are not limited to, compounds identified by experimental designations and chemical names. For instance, it describes compounds like (S)-3-(4-fluorophenyl)-3-(2-methylphenyl)propylamine and (S)-3-(4-chlorophenyl)-3-(3-methoxyphenyl)propylamine [1]. The stereochemistry at the chiral center (the carbon bearing R2) is also a critical aspect, with the patent specifically claiming the (S)-enantiomer in many instances, indicating a focus on stereoselective synthesis and activity [1].
Claims Related to Pharmaceutical Compositions
Beyond the isolated compounds, the patent also claims pharmaceutical compositions. These compositions include a therapeutically effective amount of one or more of the claimed compounds along with a pharmaceutically acceptable carrier or diluent [1]. This claim encompasses formulations suitable for various administration routes, such as oral or parenteral.
What Are the Alleged Uses of These Compounds?
The patent asserts that the claimed substituted 3-phenylpropylamine derivatives are useful in the treatment of a range of disorders, primarily those affecting the central nervous system.
Treatment of Central Nervous System Disorders
The asserted therapeutic applications center on the compounds' ability to modulate neurotransmitter systems. Specifically, the patent identifies their utility in treating:
- Depression: The compounds are claimed to be effective in alleviating symptoms of depression.
- Anxiety Disorders: Conditions characterized by excessive worry and fear are also targeted.
- Obesity: The patent suggests potential use in weight management.
- Attention Deficit Hyperactivity Disorder (ADHD): The compounds are claimed to address symptoms associated with ADHD [1].
The mechanism of action, as described or implied by the patent, relates to their interaction with monoamine transporters, such as the norepinephrine transporter (NET) and the serotonin transporter (SERT) [2]. This modulation of neurotransmitter reuptake is a common strategy in developing drugs for these conditions.
What is the Patent Landscape Surrounding U.S. Patent 5,637,320?
Analyzing the patent landscape for U.S. Patent 5,637,320 involves understanding its relationship to prior art and subsequent patent filings. This patent is part of a broader innovation space for compounds affecting monoamine neurotransmission.
Prior Art Considered
The patent application was filed in 1995, meaning the prior art considered would include patents and scientific literature predating this period. Key prior art likely would have focused on:
- Monoamine Reuptake Inhibitors: Existing antidepressants and stimulants that target NET, SERT, or dopamine transporters (DAT). Examples include fluoxetine (Prozac), sertraline (Zoloft), and various amphetamine derivatives.
- Phenylpropylamine Structures: Other chemical compounds with similar core structures explored for various pharmacological activities.
- CNS Drug Discovery: General knowledge and patents related to the treatment of depression, anxiety, and ADHD.
The novelty and inventiveness of U.S. Patent 5,637,320 would have been assessed against this existing body of knowledge.
Subsequent Patent Filings and Key Drugs
U.S. Patent 5,637,320 is linked to specific pharmaceutical products. The most prominent drug associated with this patent is Sibutramine.
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Sibutramine (Meridia/Reductil): Sibutramine is a serotonin-norepinephrine reuptake inhibitor (SNRI) that was marketed for weight loss. Its chemical structure aligns with the claims of U.S. Patent 5,637,320. Specifically, sibutramine is (±)-1-(4-chlorophenyl)-N,N-dimethyl-α-(2-methylpropyl)cyclobutanemethanamine. While the structure of sibutramine itself is a cyclobutane derivative, and not directly a 3-phenylpropylamine, the patent's scope is broad enough to encompass related structural classes or intermediates used in its synthesis, or perhaps the patent was part of a broader strategy by Pfizer that also encompassed sibutramine development. Correction: Further review indicates that U.S. Patent 5,637,320 does not directly claim sibutramine itself. Sibutramine is a distinct chemical entity. However, the patent family and its exploration of phenylpropylamine derivatives are indicative of Pfizer's research into monoamine transporter modulators. This specific patent is more directly related to compounds that were investigated for antidepressant and anti-obesity properties, and while not sibutramine, it occupies a similar therapeutic and chemical space. Research into compounds claimed by this patent may have informed or overlapped with sibutramine development strategies.
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Patent Term and Expiry: U.S. Patent 5,637,320, granted in 1997, has a term of 20 years from the filing date. The application filing date was October 27, 1995. Therefore, the patent expired on October 27, 2015. This expiry has significant implications for generic competition.
Related Patent Families and Strategic Considerations
Pfizer Inc., as the assignee, likely pursued a portfolio of patents around this class of compounds. This strategy would involve:
- Intermediate Patents: Protecting specific synthetic routes or key chemical intermediates used to manufacture the claimed compounds.
- Polymorph Patents: Claiming different crystalline forms of the active pharmaceutical ingredient (API), which can offer manufacturing advantages or extend market exclusivity.
- Formulation Patents: Protecting specific drug delivery systems or dosage forms.
- Method of Treatment Patents: Claiming new uses or specific patient populations for the compounds.
The existence of such a patent family suggests a concerted effort to build and maintain market exclusivity for drugs derived from this chemical scaffold.
What are the Implications of Patent 5,637,320's Expiry?
The expiration of U.S. Patent 5,637,320 on October 27, 2015, removed the primary patent protection for the claimed chemical compounds.
Generic Competition
Upon patent expiry, other pharmaceutical companies are free to develop and market generic versions of drugs that exclusively rely on the patent's claims for their active ingredient. This typically leads to:
- Price Reduction: Generic drugs are generally significantly cheaper than their branded counterparts.
- Increased Market Access: Lower prices can expand patient access to treatments.
- Competition: The market for the drug becomes more competitive, impacting sales of the originator product.
Litigation and Patent Challenges
Before patent expiry, companies often engage in patent litigation. Generic manufacturers may challenge the validity or enforceability of existing patents, seeking to launch their products earlier. Conversely, patent holders may sue generic companies for infringement. In this case, given the 2015 expiry, the primary period for such litigation has passed.
Orphan Drug Exclusivity and Other Market Exclusivities
It is important to distinguish patent expiry from other forms of market exclusivity. For example, if any of the compounds claimed in the patent were designated as orphan drugs for a rare disease, they could receive an additional six years of exclusivity from the date of approval, regardless of patent status. Similarly, new use patents or formulation patents can provide extended protection. However, the core composition of matter patent has expired.
Key Takeaways
- U.S. Patent 5,637,320 claims a genus of substituted 3-phenylpropylamine derivatives.
- The patent asserts therapeutic utility for these compounds in treating depression, anxiety, obesity, and ADHD.
- The patent expired on October 27, 2015.
- The expiry of this patent has opened the door for generic competition for any drugs relying solely on these composition of matter claims.
Frequently Asked Questions
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What is the primary therapeutic target of the compounds claimed in U.S. Patent 5,637,320?
The patent indicates that the claimed compounds are useful in treating conditions affecting the central nervous system, including depression, anxiety, obesity, and ADHD, by modulating monoamine neurotransmitter systems.
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When did U.S. Patent 5,637,320 expire?
U.S. Patent 5,637,320 expired on October 27, 2015.
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Does the expiration of this patent mean all related drugs are now available as generics?
The expiration of the composition of matter patent removes protection for the core chemical structure. However, other patents, such as those covering specific formulations, methods of use, or crystalline forms, could still be in effect and potentially limit generic entry.
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Was sibutramine directly covered by U.S. Patent 5,637,320?
While sibutramine is a monoamine reuptake inhibitor and occupies a similar therapeutic space, U.S. Patent 5,637,320 does not directly claim sibutramine's specific chemical structure. The patent covers a distinct class of phenylpropylamine derivatives.
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Who is the assignee of U.S. Patent 5,637,320?
The assignee of U.S. Patent 5,637,320 is Pfizer Inc.
Citations
[1] U.S. Patent 5,637,320. (1997). Substituted 3-phenylpropylamine derivatives. Pfizer Inc.
[2] Roth, B. L. (2004). Monoamine transporter signaling. Molecular Pharmacology, 66(3), 797-804.
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