The pharmaceutical industry witnesses the discontinuation of numerous drug products annually for a variety of reasons. While some of these withdrawals are due to safety or efficacy concerns, a significant number result from market dynamics or strategic business decisions.1 This landscape of discontinued drugs represents a potentially valuable, yet often overlooked, resource for addressing unmet medical needs and fostering pharmaceutical innovation.1 The reintroduction of such drugs, often termed revival or repurposing, is gaining increasing attention as the cost and timeline for developing novel therapeutic entities continue to rise.1 This analysis delves into the multifaceted process of reviving a discontinued drug, exploring the underlying reasons for their initial withdrawal, the potential benefits and inherent challenges of bringing them back to market, the complex regulatory and intellectual property considerations, the critical assessment of market potential, the ethical responsibilities involved, and the strategic role of data analysis in informing these endeavors.
Why Drugs Get Discontinued: Understanding the Initial Exit
A multitude of factors can lead a pharmaceutical company to discontinue a drug, and these reasons often fall into three primary categories: market factors, safety concerns, and manufacturing issues.3 Market forces frequently dictate the viability of a drug product. A decline in sales revenue can render a previously profitable drug unsustainable, leading to a voluntary market withdrawal by the manufacturer.4 Similarly, the emergence of more competitive or superior treatment options can diminish the market share of an existing drug, prompting its discontinuation in favor of newer, more lucrative products.5 Strategic business decisions, such as a company’s shift in therapeutic focus, mergers, or acquisitions, can also result in the discontinuation of even successful drugs if they no longer align with the overarching corporate strategy.8 Furthermore, the introduction of generic versions of a branded drug can significantly erode its profitability, leading the original manufacturer to lose interest in its continued marketing.1 The financial implications of ongoing patent litigation or the terms of settlement agreements can also necessitate a temporary or permanent cessation of a drug’s availability.1 It is important to recognize that many market-driven discontinuations are based on economic factors rather than inherent problems with the drug’s safety or effectiveness, suggesting a potential for revival under different market conditions or for alternative indications.
Safety concerns represent another significant driver of drug discontinuation. Even after rigorous testing during clinical trials, rare or unpredictable adverse events may only become apparent once a drug is used by a larger and more diverse patient population in the real-world setting.3 Instances of unexpected toxicity, such as the case of Baycol (cerivastatin) linked to rhabdomyolysis, can lead to voluntary withdrawal or regulatory action.3 The availability of safer therapeutic alternatives for the same condition can also contribute to the decision to discontinue a drug with a less favorable safety profile, as seen with Seldane (terfenadine).3 Furthermore, the discovery of dangerous interactions with other commonly used medications, certain foods, or vitamins can render a drug too complex to prescribe safely, as was the case with Posicor (mibefradil) and Seldane.3 Post-marketing surveillance plays a crucial role in identifying unacceptable health risks associated with drugs, sometimes leading to their removal from the market.10 Specific safety issues, including hepatotoxicity, cardiac disorders, hypersensitivity reactions, and nephrotoxicity, have been identified as major reasons for drug withdrawals.12 Drugs discontinued due to safety issues, particularly those involving rare but serious adverse events, might be considered for revival only under very specific conditions, such as for a different indication where the risk-benefit profile is more favorable, or with stringent risk mitigation strategies in place.
Manufacturing issues constitute the third major category of reasons for drug discontinuation. Problems related to manufacturing quality and disruptions in the supply chain are increasingly recognized as contributors to drug shortages and discontinuations.5 Contamination of the product, mislabeling, or other defects in the manufacturing process can lead to product recalls and potential discontinuation if the issues are systemic or costly to rectify.15 Shortages of essential raw materials or active pharmaceutical ingredients (APIs) can interrupt production, potentially leading to discontinuation if alternative sources cannot be secured.16 In the generic drug market, economic pressures and low profit margins can make the continued manufacturing of certain drugs unsustainable, resulting in their discontinuation.17 Failure to adhere to Good Manufacturing Practices (cGMPs) can lead to regulatory scrutiny, plant shutdowns, and ultimately, drug shortages or discontinuations.16 Drugs discontinued due to manufacturing challenges might be viable candidates for revival if these underlying issues can be resolved by a different manufacturer or through investment in updated production facilities. It is important to note the distinction between market withdrawals, which are typically business decisions, and product recalls, which are initiated due to violations of FDA regulations or safety concerns.18 This distinction can influence the regulatory pathway for any potential reintroduction.
The Allure of Revival: Benefits and Potential
The prospect of reviving a discontinued drug holds considerable appeal, primarily due to the potential to address unmet medical needs, capitalize on prior research and development efforts, and achieve faster, more cost-effective development pathways.2 One of the most compelling benefits of drug revival is the opportunity to provide therapeutic options for conditions where current treatments are inadequate or non-existent. This is particularly true for rare diseases, which often lack commercially viable drug development pathways due to small patient populations.19 Repurposing discontinued drugs for rare diseases can fill critical therapeutic gaps and offer hope to underserved patient communities, especially with the incentives provided by the Orphan Drug Act.30 This strategy can also be applied to neglected diseases that may not attract significant commercial interest but pose substantial public health challenges.26
Reviving a discontinued drug allows pharmaceutical companies and researchers to leverage the substantial investments already made in its research and development.2 A significant amount of data on the drug’s properties, mechanism of action, pharmacokinetics, pharmacodynamics, and importantly, its safety profile in humans, may already exist.2 This prior knowledge can significantly reduce the time and expense associated with the early stages of drug development, such as preclinical testing and Phase I clinical trials, as these might not need to be repeated.2 Consequently, the clinical development process for a revived drug can be considerably faster and less risky compared to developing a new chemical entity from scratch.2 The average time savings can be substantial, often ranging from five to seven years, with overall development costs potentially reduced by 50-60%.2 Furthermore, regulatory pathways like the FDA’s 505(b)(2) are specifically designed to facilitate the approval of drugs where some reliance can be placed on previously established safety and efficacy data, making the reintroduction process more efficient and cost-effective.22 The economic and temporal advantages of reviving a discontinued drug are particularly compelling when considering the increasing costs and lengthy timelines associated with traditional pharmaceutical R&D, especially in the context of rare diseases where patient populations are small and development can be financially challenging. The pre-existing safety data for discontinued drugs significantly mitigates the risks inherent in drug development, allowing a greater focus on demonstrating efficacy for a new therapeutic use and potentially leading to higher approval rates.
Navigating the Revival Road: Challenges and Complexities
Despite the potential benefits, reviving a discontinued drug is a complex undertaking fraught with challenges, particularly in the areas of regulatory hurdles, manufacturing re-establishment, and intellectual property issues.20 The process of reintroducing a drug to the market is no longer a simple administrative matter; regulatory agencies like the FDA and EMA have established more formal and stringent requirements.1 Manufacturers must notify the respective agencies of their intent to remarket a discontinued drug and provide detailed information about its history, manufacturing processes, any changes made since discontinuation, and the proposed new use.1 The FDA, for instance, will scrutinize the reasons for the original discontinuation, the length of time the drug has been off the market, and whether there have been any transfers of ownership or changes in manufacturing.1 Drugs that were initially discontinued due to safety or effectiveness concerns face a significantly higher regulatory bar for reintroduction and may even be prohibited from being revived.41 Navigating the specific procedures and requirements of different regulatory agencies, such as the FDA in the United States and the EMA in Europe, is crucial and can be a significant hurdle, as these processes can vary considerably.35 Even for drugs not discontinued for safety reasons, obtaining regulatory approval for a new indication or a label extension can be a complex and resource-intensive process.44
Re-establishing the manufacturing of a discontinued drug can also present substantial challenges.46 The original manufacturing facilities or processes might no longer be available, necessitating the identification of new manufacturing partners or the re-building of the original infrastructure, both of which require significant investment and expertise.46 Sourcing the necessary raw materials and active pharmaceutical ingredients (APIs) can be problematic, especially if the original suppliers have ceased operations or if new quality standards require different sourcing strategies.16 Ensuring that the re-established manufacturing process complies with current Good Manufacturing Practices (cGMPs) is paramount and may require extensive validation and regulatory inspections.16
Intellectual property considerations, particularly existing patents, pose another layer of complexity.20 The original patents on the drug or related aspects might still be active, potentially hindering reintroduction or the entry of generic competitors.20 In some instances, a company might have initially discontinued a drug due to ongoing patent litigation or settlement agreements that restricted its marketing.1 To successfully revive a discontinued drug, companies often need to formulate strategies for obtaining new patent protection, such as for novel uses, new formulations, or innovative delivery methods.54 A thorough analysis of the patent landscape surrounding the original drug is therefore essential to identify any potential barriers and to develop a robust intellectual property strategy for the revived product.
Learning from the Past: Case Studies of Successful Drug Revivals
Examining instances where discontinued drugs have been successfully revived provides valuable insights into the factors that contribute to their reintroduction and market acceptance. Several notable examples illustrate the potential and the pathways for successful revival.
Thalidomide, initially marketed as a sedative and for morning sickness in the mid-1950s, was withdrawn due to its association with severe birth defects.20 However, subsequent research revealed its mechanism of action in inhibiting tumor necrosis factor-alpha signaling, leading to its successful repurposing for the treatment of erythema nodosum leprosum (ENL), a serious complication of leprosy, and later for multiple myeloma.20 The revival of thalidomide was contingent on a new scientific understanding of its biological effects and the identification of critical unmet medical needs in these specific conditions. Its use is now governed by strict guidelines to prevent the teratogenic effects observed in its initial use.20
Daptomycin, an antibiotic, was initially abandoned by Eli Lilly after four years of development due to a strategic shift in their business focus.20 However, Cubist Pharmaceuticals recognized its potential and successfully repurposed it as an important antibiotic, particularly effective against drug-resistant bacteria like MRSA.20 Cubist’s success involved redesigning the clinical trials to demonstrate efficacy for its new indication and navigating challenging intellectual property negotiations to secure the rights to the drug.20 Daptomycin now serves as a crucial last-resort medication, highlighting how a dedicated company can champion a shelved asset and bring it to market to address a significant public health need.
Amlexanox, initially developed in Japan for asthma and later approved in the US for aphthous ulcers, saw a decline in use with the advent of newer therapies.26 However, its unique mechanism of action in suppressing nonsense-mediated decay (NMD) and promoting the readthrough of nonsense mutations has opened new possibilities for treating rare genetic diseases.26 Fortuity Pharma is currently leading efforts to revive amlexanox for conditions like WOREE Syndrome, where it has shown promise in preclinical studies by potentially restoring protein function and addressing central nervous system symptoms.26 The story of amlexanox underscores how a drug discontinued for commercial reasons can be revived to address substantial unmet needs in rare diseases through a focus on its specific biological mechanisms.
These case studies demonstrate that successful drug revivals often depend on the convergence of several factors. A deeper understanding of the drug’s mechanism of action, the identification of a significant unmet medical need, the presence of a dedicated entity to drive the revival process, strategic management of intellectual property, and the ability to adapt clinical trial designs to demonstrate efficacy for the new indication are all critical elements that contribute to the successful reintroduction of a discontinued drug.
The Regulatory Maze: Pathways and Requirements for Reintroduction
The regulatory landscape for reintroducing a discontinued drug is complex and differs between major markets like the United States and Europe. In the United States, the Food and Drug Administration (FDA) requires a formal process for remarketing a drug that has been previously discontinued.1 A manufacturer intending to revive a drug must notify the FDA and provide comprehensive information, including the original launch date, the date of discontinuation, the last manufacturing date, any changes in ownership, and details about the API supplier, manufacturing process, and equipment.1 The FDA will assess this information to determine if a supplement to the original New Drug Application (NDA) or Abbreviated New Drug Application (ANDA) is required before the drug can be re-marketed.1 It is crucial to note that drugs discontinued due to safety or effectiveness concerns are listed under § 216.24 of the Code of Federal Regulations and are generally not eligible for compounding under certain exemptions, indicating a more challenging path for revival.42 For drugs not discontinued for these reasons, the 505(b)(2) regulatory pathway often provides a viable route for revival, as it allows an applicant to rely on the FDA’s previous findings of safety and effectiveness for the already-approved drug, potentially reducing the need for extensive new clinical trials.22 Furthermore, manufacturers are legally obligated to notify the FDA of any permanent discontinuance or significant interruption in the manufacturing of certain prescription drugs and biological products, highlighting the agency’s focus on maintaining drug supply.5 In cases where the revived drug addresses a serious condition with an unmet medical need, the Accelerated Approval pathway might be an option to expedite its availability to patients, although this pathway comes with requirements for post-approval confirmatory trials.106
In Europe, the European Medicines Agency (EMA) also plays a central role in the reintroduction of discontinued drugs. The EMA’s safety committee (PRAC) can recommend the withdrawal of marketing authorizations for drugs that pose significant safety risks, as exemplified by the case of amfepramone.108 Reasons for discontinuation in the European Union can range from low sales and production problems to the discovery of serious adverse effects.111 A key aspect of the EU regulatory framework is that only the Marketing Authorisation Holder (MAH) has the authority to request a new indication for an existing medicine.45 For centrally authorized medicines, the centralized procedure is mandatory for certain categories, including those derived from biotechnology or intended to treat conditions like HIV, cancer, diabetes, and neurodegenerative diseases.113 Similar to the FDA’s accelerated approval, the EMA offers mechanisms like conditional marketing authorization and accelerated assessment for drugs that address unmet medical needs or are of major interest for public health innovation.114 The EMA also has specific regulations regarding data exclusivity and market protection, which can impact the timing of generic entry for revived drugs.117 Navigating the regulatory pathways in both the US and Europe necessitates a thorough understanding of their distinct requirements and procedures, and a revival strategy must be tailored to the specific agency being targeted, considering the reasons for the original discontinuation and the proposed new use.
Securing the Future: Patent Strategies for Revived Drugs
For a discontinued drug to be commercially viable upon revival, strategic management of intellectual property is paramount. One key aspect is the potential to obtain new clinical investigation exclusivity from regulatory agencies. In the United States, the FDA can grant three years of new clinical investigation exclusivity for a previously approved drug if the application for a new indication or condition of use contains reports of new clinical investigations, other than bioavailability studies, that were essential for the approval of the new use and were conducted or sponsored by the applicant.51 This exclusivity can provide a valuable period of market protection against generic competition for the specific new conditions of approval.121
Beyond regulatory exclusivities, securing new patents is often a critical component of a successful drug revival strategy. This can involve patenting new formulations of the old drug, such as extended-release versions that improve patient convenience or compliance.66 Innovations in drug delivery methods, such as the development of injectable hydrogels or nanoparticle-based delivery systems for targeted therapy, can also be patentable and offer significant advantages over the original formulation.91 Perhaps the most significant patent opportunity for a revived drug lies in discovering and patenting new therapeutic uses or indications for the compound that differ from its original intended use.60 These “method-of-use” patents can provide substantial market exclusivity for the new application of the drug.
A crucial step before embarking on a drug revival effort is to thoroughly analyze the existing patent landscape.48 Patents held by the original manufacturer or by competitors might still be in force and could potentially block the reintroduction of the drug or its use for specific indications.48 Strategies such as “patent thicketing,” where multiple overlapping patents are filed on different aspects of a drug, and “evergreening,” which involves obtaining new patents on minor modifications to extend protection, can create significant barriers to generic competition and may need to be considered when planning a revival.48 Developing a comprehensive patent strategy that encompasses not only the revived drug itself but also potential new uses, formulations, and delivery methods is essential to maximize market exclusivity and ensure a favorable return on investment.
Assessing the Potential: Market Analysis and Commercial Viability
A thorough evaluation of the market potential and commercial viability is a critical prerequisite for deciding whether to revive a discontinued drug. This assessment involves analyzing the patient population for both the original indication and any potential new therapeutic uses.128 Understanding the size and characteristics of the target patient group is fundamental to estimating the potential market size. Equally important is a comprehensive analysis of the competitive landscape, which includes identifying existing treatments, their effectiveness, their market share, and any potential future competitors or emerging therapies.133 This analysis helps to determine the potential for the revived drug to gain a foothold in the market and differentiate itself from existing options.
Developing a viable pricing strategy is another crucial element of the market assessment.139 Factors such as the drug’s uniqueness, its effectiveness compared to competitors, the cost of development and manufacturing, and the prevailing reimbursement landscape will all influence the optimal pricing strategy. For a revived drug, especially if it is being repurposed for a new indication, assessing its cost-effectiveness relative to existing therapies is particularly important for securing market access and favorable reimbursement policies.144
Market intelligence and data analytics play an increasingly vital role in informing the decision-making process for drug revival.20 Market research can provide valuable insights into the size of the pharmaceutical market, patient demographics, and trends in pharmaceutical sales.129 Advanced data analysis techniques, including the use of real-world data from electronic health records and insurance claims, along with artificial intelligence (AI) and machine learning (ML) algorithms, can help identify potential candidates for drug revival and predict their efficacy for new indications.20 Predictive analytics can be employed to forecast the commercial potential of a revived drug by analyzing various market factors and clinical data.156 A comprehensive market analysis, leveraging both traditional market research and advanced data analytics, is essential to accurately assess the commercial viability of reviving a discontinued drug, even if it addresses a significant unmet medical need. Factors such as the size of the addressable patient population, the strength of the competitive landscape, and the anticipated pricing and reimbursement environment will ultimately determine the success of the reintroduction.
Ethical Considerations: Balancing Revival with Responsibility
The decision to revive a discontinued drug carries significant ethical responsibilities, particularly concerning safety, efficacy, access, and potential conflicts of interest.1 Pharmaceutical companies have a fundamental moral obligation to fully disclose all information pertaining to the true risks and benefits of their drugs, both in their original use and in any proposed new applications.169 When considering the revival of a drug, especially one that was previously discontinued due to safety concerns, maintaining a high standard of evidence and the integrity of clinical research ethics is paramount.173 The risk-benefit ratio for the proposed new indication must be rigorously evaluated, ensuring that the potential benefits outweigh any known or potential risks.168
Ensuring equitable access to a revived drug is another critical ethical consideration.179 This is particularly important if the drug is being repurposed to treat a rare or underserved population. Fairness in the distribution of resources and ensuring that the drug is available to those who need it most are ethical imperatives, especially in emergency situations where the drug might be considered for a new indication.173 Transparency in the pricing of revived drugs is also an increasing area of ethical concern and public scrutiny.191 The ethical imperative of providing timely access to essential medicines, including orphan drugs, needs to be carefully balanced with the economic incentives that drive pharmaceutical development.181
Managing potential conflicts of interest is also crucial in the context of drug revival.199 Financial ties between researchers, pharmaceutical companies, and other stakeholders can create conflicts that may compromise the objectivity of research and the integrity of clinical practice.199 Implementing robust and transparent conflict of interest policies is essential to maintain public trust and ensure that decisions regarding drug revival are made in the best interest of patients.200 The ethical considerations surrounding the revival of a discontinued drug underscore the need for a responsible and transparent approach that prioritizes patient safety, equitable access, and the integrity of the scientific and clinical processes.
Conclusion: Charting the Course for Successful Drug Revival
The revival of a discontinued drug presents a compelling opportunity to address unmet medical needs, leverage prior R&D investments, and potentially bring therapies to patients more efficiently than traditional drug development pathways. However, this endeavor is not without its complexities. A thorough understanding of the reasons for the drug’s initial discontinuation is paramount, as this will inform the regulatory strategy and the potential challenges that may arise. The benefits of revival, particularly in addressing rare and neglected diseases, must be weighed against the significant hurdles in navigating regulatory requirements, re-establishing manufacturing, and managing intellectual property. Learning from the successes of previously revived drugs, such as thalidomide, daptomycin, and amlexanox, highlights the importance of identifying new therapeutic uses, demonstrating efficacy through well-designed clinical trials, and strategically managing intellectual property. Navigating the regulatory landscapes of the US and Europe requires careful attention to their specific procedures and requirements. Securing new patent protection for revived drugs, whether through new uses, formulations, or delivery methods, is often essential for commercial viability. A comprehensive assessment of the market potential, utilizing both traditional market analysis and advanced data analytics, is crucial for making informed decisions. Finally, ethical considerations regarding safety, efficacy, access, and potential conflicts of interest must be at the forefront of any drug revival effort. By carefully considering all these factors, stakeholders can chart a course for the successful revival of discontinued drugs, ultimately benefiting patients and advancing pharmaceutical innovation.
Reason for Discontinuation
Category
Example
Snippet IDs
Falling sales revenue
Market Factors
Unspecified
4
Rise in product liability lawsuits
Market Factors
Unspecified
4
Older drugs replaced by newer ones
Market Factors
Unspecified
5
Generic competition eroded market share
Market Factors
Unspecified
1
Strategic business decisions
Market Factors
Momelotinib (Gilead)
8
Rare, unpredictable side effects
Safety Concerns
Unspecified
3
Unexpected toxicity
Safety Concerns
Baycol (cerivastatin)
3
Safer options available
Safety Concerns
Seldane (terfenadine)
3
Dangerous drug combinations
Safety Concerns
Posicor (mibefradil)
3
Post-marketing surveillance revealed risks
Safety Concerns
Vioxx (rofecoxib)
10
Hepatotoxicity
Safety Concerns
Unspecified
12
Manufacturing quality issues
Manufacturing Issues
Unspecified
5
Contamination
Manufacturing Issues
Artificial tears
15
Shortages of raw materials
Manufacturing Issues
Unspecified
16
Generic economic deflation
Manufacturing Issues
Unspecified
17
Failure to meet cGMP
Manufacturing Issues
Unspecified
16
Drug
Initial Reason for Discontinuation
New Indication
Key Players
Critical Success Factors
Snippet IDs
Thalidomide
Severe birth defects
Erythema nodosum leprosum, Multiple myeloma
Chemie Grunenthal, Researchers
New understanding of mechanism of action, Significant unmet medical need
20
Daptomycin
Abandoned by Eli Lilly (strategic)
Antibiotic (MRSA, etc.)
Eli Lilly, Cubist Pharmaceuticals
Champion within Cubist, Redesign of clinical trials, IP negotiations
20
Amlexanox
Commercial reasons
Rare diseases (WOREE Syndrome)
Original manufacturer, Fortuity Pharma
Mechanism of action in suppressing NMD, Potential to cross blood-brain barrier
Rescuing Drugs That are Discontinued in Adult Oncology Development for the Benefit of Children and Adolescents With Cancer – An ACCELERATE Multistakeholder Consensus – PubMed, accessed April 9, 2025, https://pubmed.ncbi.nlm.nih.gov/37885401/
Notifying FDA of a Permanent Discontinuance or Interruption in Manufacturing of a Device Under Section 506J of the FDC Act, accessed April 9, 2025, https://www.fda.gov/media/155245/download
Clinical trial diversity: An opportunity for improved insight into the determinants of variability in drug response – PubMed Central, accessed April 9, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC9306578/
Clinical use of [15O]H2O/[18F]FDG viability positron emission tomography does not reliably predict left ventricular ejection fraction improvement or survival after revascularization | European Heart Journal – Cardiovascular Imaging | Oxford Academic, accessed April 9, 2025, https://academic.oup.com/ehjcimaging/advance-article/doi/10.1093/ehjci/jeaf041/7997951
Percutaneous Revascularization for Ischemic Left Ventricular Dysfunction: Cost-Effectiveness Analysis of the REVIVED-BCIS2 Trial | Circulation: Cardiovascular Quality and Outcomes – American Heart Association Journals, accessed April 9, 2025, https://www.ahajournals.org/doi/10.1161/CIRCOUTCOMES.123.010533
Viability and Outcomes With Revascularization or Medical Therapy in Ischemic Ventricular Dysfunction: A Prespecified Secondary Analysis of the REVIVED-BCIS2 Trial – PubMed, accessed April 9, 2025, https://pubmed.ncbi.nlm.nih.gov/37878295/
Drug Repositioning: New Approaches and Future Prospects for Life-Debilitating Diseases and the COVID-19 Pandemic Outbreak – PubMed Central, accessed April 9, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC7551028/
Restoring Study 329: efficacy and harms of paroxetine and imipramine in treatment of major depression in adolescence | The BMJ, accessed April 9, 2025, https://www.bmj.com/content/351/bmj.h4320
Understanding the challenges and ethical aspects of compassionate use of drugs in emergency situations – PMC – PubMed Central, accessed April 9, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC7446672/
Exploration of Repurposed and Adjuvant Drugs in COVID-19 Patients, as well as Challenges and Ethical Issues Related to Drug Repurposing – Bentham Science Publisher, accessed April 9, 2025, https://www.benthamscience.com/chapter/19054
Katarzyna Klas, Karolina Strzebonska & Marcin Waligora, Ethical challenges of clinical trials with a repurposed drug in outbreaks – PhilPapers, accessed April 9, 2025, https://philpapers.org/rec/KLAECO
Drug Repurposing in the COVID-19 Era: Insights from Case Studies Showing Pharmaceutical Peculiarities – MDPI, accessed April 9, 2025, https://www.mdpi.com/1999-4923/13/3/302
