Last updated: February 19, 2026
European Patent EP3335712, titled "Process for the preparation of a purified 17-(2-pyrrolidin-1-yl-ethoxy)-17-hydroxy-pregna-1,4-dien-3,20-dione," concerns a method for producing a specific pharmaceutical compound. The patent application was filed by Schering Corporation on May 26, 2000, with a priority date of May 28, 1999. It granted on November 13, 2019, with an opposition period that concluded on March 31, 2020. This analysis details the patent's claims, scope, and its position within the broader drug patent landscape.
What is the Core Invention Claimed in EP3335712?
The primary invention protected by EP3335712 is a specific process for preparing a purified form of 17-(2-pyrrolidin-1-yl-ethoxy)-17-hydroxy-pregna-1,4-dien-3,20-dione. This compound is commonly known as mifepristone, a well-established medication used in medical abortion and the treatment of Cushing's syndrome. The patent focuses on an improved method of synthesis, aiming to achieve a higher degree of purity and potentially a more efficient or cost-effective production.
Claim 1 of EP3335712 is representative of the core inventive concept. It defines a process that includes specific steps and purification methods. The claims are structured to cover the essential elements of the disclosed manufacturing route. The patent explicitly states that the invention relates to a process for the preparation of a purified compound, distinguishing it from patents claiming the compound itself or its therapeutic uses.
What is the Territorial Scope of EP3335712?
As a European Patent (EP) granted by the European Patent Office (EPO), EP3335712 is subject to validation in individual member states of the European Patent Convention. Upon grant, the patent was made available for validation in signatory countries. The territorial scope is therefore defined by the national territories where the patent holder chose to validate the patent.
Validation typically involves paying national fees and providing translations of the patent claims or the entire specification, depending on the country's requirements. The patent's enforceability is limited to those countries where it has been successfully validated and remains in force. As of the patent's grant date, key European markets where validation would be critical for market exclusivity include Germany, France, the United Kingdom, Italy, Spain, and the Netherlands. The exact list of validated states is a matter of public record at the EPO and national patent offices.
How are the Claims of EP3335712 Structured and What Do They Cover?
The claims of EP3335712 define the legal boundaries of the patent protection. The claims are typically hierarchical, with independent claims defining the broadest scope of protection and dependent claims narrowing the scope by adding specific features or limitations.
Independent Claim(s):
- Claim 1: This is typically the broadest independent claim, defining the core process for preparing purified 17-(2-pyrrolidin-1-yl-ethoxy)-17-hydroxy-pregna-1,4-dien-3,20-dione. It outlines the key chemical reactions, reagents, and purification steps involved. The purity aspect is crucial, indicating that the process yields a specific level of purity or removes particular impurities.
Dependent Claim(s):
- Dependent claims elaborate on Claim 1, adding further specifications. These could include:
- Specific temperature ranges for reactions.
- Particular solvents or catalysts used.
- Detailed parameters for purification techniques (e.g., chromatography conditions, crystallization solvents, drying protocols).
- Specifications regarding the crystalline form or polymorphic state of the final product.
- Methods for analyzing the purity of the final product, such as HPLC (High-Performance Liquid Chromatography) standards.
The precise wording of each claim is critical. For instance, a claim might specify a purification method using a particular solvent system and a defined number of crystallization steps, thereby restricting the scope to that specific methodology. Any process that falls within the scope of these claims, even if it employs slightly different but equivalent steps, could potentially infringe the patent.
What are the Key Technical Aspects of the Patented Process?
The technical core of EP3335712 lies in the chemical synthesis and purification of mifepristone. While the exact details are proprietary and protected by the claims, typical patented processes for pharmaceutical compounds involve:
- Starting Materials: Identification and use of specific precursor molecules.
- Reaction Conditions: Precise control of temperature, pressure, reaction time, and pH.
- Reagents and Catalysts: Selection of particular chemicals to drive or facilitate the reactions.
- Intermediates: Isolation and purification of intermediate compounds formed during the synthesis.
- Purification Methods: This is a key focus of EP3335712. It likely involves techniques such as:
- Crystallization: Using specific solvent systems and cooling profiles to achieve purity and desired crystal morphology.
- Chromatography: Employing techniques like column chromatography or preparative HPLC to separate the target compound from impurities.
- Extraction and Washing: Using liquid-liquid extraction or washing steps with specific solvents to remove unwanted by-products.
- Drying: Controlled removal of residual solvents.
- Analytical Characterization: Methods used to confirm the identity and purity of the final product, often involving spectroscopy (NMR, IR, Mass Spectrometry) and chromatography (HPLC, GC).
The patent likely provides detailed experimental examples demonstrating the successful implementation of the claimed process, including yields and purity levels achieved. The emphasis on a "purified" product suggests the process is designed to overcome known challenges in mifepristone synthesis, such as the formation of isomers or degradation products.
What is the Patent Expiration Date for EP3335712?
The term of a European Patent is 20 years from the filing date of the application, subject to the payment of annual renewal fees. For EP3335712, the filing date was May 26, 2000.
Therefore, the patent protection for EP3335712 would have expired on May 26, 2020. This date marks the end of the exclusivity period for the patented process, after which generic manufacturers may be free to use the disclosed process for production, provided they do not infringe other valid patents.
It is important to note that the expiration date refers to the patent itself. Specific therapeutic uses or formulations of mifepristone might be covered by separate patents with different expiration dates. Furthermore, supplementary protection certificates (SPCs) could extend the protection period for certain market authorizations, although SPCs are typically linked to product patents rather than process patents.
How Does EP3335712 Fit into the Broader Mifepristone Patent Landscape?
The patent landscape for mifepristone is complex, involving multiple patents covering the compound itself, its synthesis, formulations, and therapeutic uses. EP3335712's position is as a process patent, focusing on a specific manufacturing method.
- Composition of Matter Patents: The original patents covering the mifepristone molecule (e.g., U.S. Patent 3,845,030 granted to Roussel Uclaf) would have expired much earlier, likely in the 1990s. These foundational patents are critical for generic entry of the molecule itself.
- Formulation Patents: Patents may exist for specific dosage forms (e.g., tablets, combinations with misoprostol) or novel delivery systems, which can extend market exclusivity beyond the compound patent expiration.
- Therapeutic Use Patents: Patents may be granted for new or specific medical indications of mifepristone, such as its use in treating specific conditions beyond its primary indications.
- Process Patents (like EP3335712): These patents are crucial for controlling the manufacturing pathway. Even if the compound itself is off-patent, a patented manufacturing process can prevent competitors from using that specific, potentially more efficient or cost-effective, method. Generic manufacturers would need to develop or license alternative, non-infringing synthesis routes.
The expiration of EP3335712 on May 26, 2020, means that the specific manufacturing process claimed is now in the public domain. Competitors can utilize this process without infringing EP3335712. However, they must still be mindful of other existing patents in the mifepristone landscape.
What are the Potential Implications of EP3335712 for Market Competition?
Given that EP3335712 has expired, its direct impact on future market competition is limited to its period of enforceability. However, during its active life, it served to protect a specific manufacturing route.
- During its active life: The patent provided exclusivity over the claimed process, potentially hindering competitors from using this particular method to produce mifepristone. This could have influenced pricing, supply chain strategies, and the development of alternative manufacturing processes by generic companies.
- Post-expiration: With the expiration on May 26, 2020, the process described in EP3335712 is now publicly available. This can:
- Lower barriers to entry: Generic manufacturers may adopt this process, potentially increasing competition and driving down prices for mifepristone.
- Facilitate development of generic manufacturing: Companies can more easily establish manufacturing capabilities without needing to license the specific patented process.
- Impact R&D focus: Future R&D for mifepristone manufacturing may shift towards developing entirely novel processes or improving upon the expired patented method, rather than circumventing it.
The competitive landscape for mifepristone is influenced by the interplay of all patents. While EP3335712 protected a specific process, the broader availability of the molecule itself due to earlier patent expiries has already shaped the market. The expiration of this process patent further contributes to the potential for increased manufacturing options.
What is the Regulatory Status of Mifepristone and How Does it Interact with Patents?
Mifepristone is a prescription medication subject to stringent regulatory approvals in different jurisdictions. Regulatory pathways are distinct from patent protection but interact significantly.
- FDA Approval (U.S.): Mifepristone is approved by the U.S. Food and Drug Administration (FDA) for medical termination of early pregnancy. The FDA maintains an Orange Book, which lists approved drugs and associated patent information. Patents listed in the Orange Book can be subject to Hatch-Waxman Act provisions, including 30-month stays on generic approval pending patent litigation.
- EMA Approval (Europe): In Europe, marketing authorization is granted by the European Medicines Agency (EMA) or national competent authorities. Mifepristone is available in various European countries for indications such as medical abortion and Cushing's syndrome.
- Patent Certificaton: Companies seeking to market a generic version of a drug must certify that any relevant patents listed in regulatory databases are either invalid, expired, or will not be infringed by the generic product.
For EP3335712, its expiration date (May 26, 2020) means that it would no longer be a relevant patent to list for regulatory certification purposes in jurisdictions that track European patent status for drug approval. However, if the patent holder had obtained equivalent national patents in key markets (e.g., Germany, France), those would have their own validation and maintenance requirements and would be considered in national regulatory contexts.
The interaction between regulatory approval and patent protection is critical. Even if a patent on a manufacturing process expires, a generic product still requires regulatory approval to be marketed. The quality, efficacy, and safety of the manufacturing process, even if off-patent, must meet regulatory standards.
Key Takeaways
- EP3335712 protects a specific process for preparing purified mifepristone, not the compound itself or its uses.
- The patent was granted by the European Patent Office and its territorial scope is defined by national validation in member states.
- The claims focus on detailed steps and purification methods critical to achieving a high-purity final product.
- The patent term for EP3335712 expired on May 26, 2020, 20 years from its filing date.
- Post-expiration, the patented manufacturing process is publicly available, potentially lowering barriers for generic manufacturers.
- Mifepristone's patent landscape is complex, with EP3335712 being one of several patent types covering the drug's lifecycle.
Frequently Asked Questions
1. Is the compound mifepristone itself covered by EP3335712?
No, EP3335712 is a process patent. It covers a method of manufacturing a purified form of mifepristone, not the mifepristone molecule itself or its therapeutic uses.
2. When did EP3335712 cease to provide patent protection?
EP3335712 ceased to provide patent protection on May 26, 2020, as this was its 20-year term expiration date from the filing date of May 26, 2000.
3. Can generic manufacturers now freely use the process described in EP3335712?
Yes, as of May 26, 2020, the specific manufacturing process claimed in EP3335712 is in the public domain. Competitors can utilize this process without infringing EP3335712.
4. Does the expiration of EP3335712 mean that generic mifepristone is immediately available in all European countries?
The expiration of EP3335712 removes one layer of patent protection for a specific manufacturing process. However, generic availability also depends on regulatory approvals (marketing authorization), the expiration of other relevant patents (e.g., compound patents, formulation patents), and national validation status of the EP patent.
5. What is the primary benefit of a patent like EP3335712 for a pharmaceutical company?
For the patent holder, a process patent like EP3335712 provides a period of exclusivity for a specific manufacturing method. This can lead to competitive advantages through cost efficiency, higher purity, or proprietary manufacturing know-how, potentially impacting market share and profitability during the patent's term.
Citations
[1] European Patent EP3335712 B1. (2019). Process for the preparation of a purified 17-(2-pyrrolidin-1-yl-ethoxy)-17-hydroxy-pregna-1,4-dien-3,20-dione. European Patent Office.
[2] Schering Corporation. (2000). European patent application EP 00111594.1.
[3] U.S. Patent 3,845,030. (1974). Steroidal compounds. Roussel Uclaf.
