Detailed Analysis of the Scope and Claims of United States Patent 5,312,925
Introduction
United States Patent 5,312,925, granted to Pfizer Inc., pertains to the monohydrate of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydro-2H-indole-2-one hydrochloride, commonly known as ziprasidone. This patent is crucial for understanding the synthesis, characterization, and stability of ziprasidone, a neuroleptic agent used in the treatment of schizophrenia.
Background
Ziprasidone, marketed under the brand name Geodon™, was approved by the FDA for the treatment of schizophrenia. The patent in question focuses on a specific form of ziprasidone, the monohydrate of its hydrochloride salt, which exhibits advantageous stability properties[4].
Patent Scope
Claim Structure
The patent includes four claims that define the scope of the invention. These claims are structured to cover the specific compound, its synthesis process, and its characterization.
- Claim 1: This claim defines the monohydrate of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydro-2H-indole-2-one hydrochloride.
- Claims 2-4: These claims specify the process for preparing the monohydrate, including the heating and reflux steps, and the characterization methods such as IR, XRD, and moisture content analysis[1].
Independent Claim Length and Count
The patent scope can be analyzed using metrics such as independent claim length (ICL) and independent claim count (ICC). In this case, the patent has a relatively focused set of claims, indicating a narrower scope. This narrow scope is associated with higher clarity and a higher probability of grant, as well as a shorter examination process[3].
Synthesis Process
The patent describes a detailed process for the synthesis of ziprasidone hydrochloride monohydrate. This involves heating a mixture to reflux, which is a critical step in ensuring the formation of the desired compound. The process is outlined in the patent with specific examples and conditions, such as the use of solvents and the control of temperature and reaction time[2][4].
Characterization
The characterization of the monohydrate is a key aspect of the patent. Methods such as infrared spectroscopy (IR), X-ray diffraction (XRD), and moisture content analysis are used to confirm the structure and purity of the compound. The patent provides detailed data on the IR and XRD spectra, as well as the moisture content of the monohydrate, hemihydrate, and anhydrous forms of ziprasidone hydrochloride[1][4].
Stability
One of the significant advantages of the monohydrate form of ziprasidone hydrochloride is its stability. The patent highlights that this form has improved stability compared to other forms, making it more suitable for pharmaceutical formulations. This stability is crucial for maintaining the efficacy and shelf life of the drug[1].
Patent Landscape
Related Patents
Several other patents are related to the synthesis and formulation of ziprasidone. For example:
- U.S. Patent 4,831,031: Describes a genus of compounds encompassing ziprasidone and its synthesis.
- U.S. Patent 5,206,366: Another method for synthesizing ziprasidone.
- U.S. Patents 6,245,765 and 6,110,918: Methods for synthesizing ziprasidone mesylate dihydrate and trihydrate, respectively[4].
Litigation and Examination
The patent examination process for ziprasidone-related patents has been rigorous, reflecting the importance of patent quality and scope. Studies have shown that narrower claims, like those in this patent, are associated with a higher probability of grant and a shorter examination process. This suggests that the USPTO has been diligent in evaluating the patents related to ziprasidone to ensure clarity and validity[3].
Maintenance Fees
The maintenance fees for U.S. Patent 5,312,925 are no longer due, indicating that the patent has reached the end of its term. This is typical for patents granted in the early 1990s, as they generally have a term of 20 years from the filing date[5].
Industry Impact
The approval and patenting of ziprasidone have had a significant impact on the treatment of schizophrenia. The stability and efficacy of the monohydrate form have made it a preferred choice in clinical settings.
"Ziprasidone has been approved by the FDA for treatment of schizophrenia and goes by the brand name Geodon™ in the United States."[4]
Key Takeaways
- Specific Compound: The patent covers the monohydrate of ziprasidone hydrochloride, emphasizing its stability and synthesis process.
- Claim Structure: The patent includes four focused claims defining the compound, its synthesis, and characterization.
- Characterization Methods: IR, XRD, and moisture content analysis are used to characterize the compound.
- Stability: The monohydrate form exhibits improved stability, crucial for pharmaceutical formulations.
- Related Patents: Several other patents cover different aspects of ziprasidone synthesis and formulation.
- Patent Landscape: The patent has undergone rigorous examination, reflecting the importance of patent quality and scope.
FAQs
What is the main compound described in U.S. Patent 5,312,925?
The main compound is the monohydrate of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydro-2H-indole-2-one hydrochloride, known as ziprasidone.
What is the significance of the monohydrate form of ziprasidone?
The monohydrate form of ziprasidone exhibits improved stability, making it more suitable for pharmaceutical formulations.
How is the monohydrate of ziprasidone synthesized?
The synthesis involves heating a mixture to reflux, with specific conditions and solvents described in the patent.
What methods are used to characterize the monohydrate of ziprasidone?
Characterization methods include infrared spectroscopy (IR), X-ray diffraction (XRD), and moisture content analysis.
Is U.S. Patent 5,312,925 still in force?
No, the patent has reached the end of its term and is no longer in force.
Sources
- US5312925A - United States Patent (19) Patent Number: 5,312,925 Allen et al.
- US8178674B2 - Process for the preparation of ziprasidone - Google Patents
- Patent Claims and Patent Scope - Hoover Institution
- Ziprasidone - New Drug Approvals
- USPTO Fee Processing - Maintenance Fee Details - Patent 5312925
