Remark

Introduction

The new disease caused by the coronavirus (COVID-19) was reported in the city of Wuhan, Hubei province in China, and has spread rapidly around the world. Infected patients have been reported in 210 countries. This disease was declared as pandemic by the World Health Organization on March 12th (WHO) ¹.

SARS-CoV-2 is a positive single-stranded RNA beta-coronavirus. Like SARS and MERS, the genome encodes non-structural proteins such as chymotrypsin type 3 protease, papain-like protease, helicase, and RNA-dependent RNA polymerase; and structural proteins such as spike glycoprotein and accessory proteins ². So far, there are no vaccines that had been approved. However, just a few weeks after the first reports of the disease, several laboratories began investigating for a vaccine that immunizes against this virus, and approximately 37 research laboratories and academic centres are currently doing so ³. Vaccine development already has a starting point from the knowledge gained from the SARS-CoV and MERS epidemics and the selection of antigens based on them. However, it would take several months for a vaccine to have a consistent safety profile across populations and to mimic the immune response ⁴.

Another option would be to develop new molecules that allow treating the disease according to its stage; however, this process could be even slower. Furthermore, de novo drug development takes place in an environment where preclinical research findings may not be replicated ⁵. Likewise, when researching new molecules in humans, it is necessary to ask several questions that could improve the designs, and avoid some failures, such as, for example, did the drug hit the target?, did the medication change the target?, what was the dose response?, and what are the characteristics of the study patients?. To answer these questions, you need financial resources and time, which in many occasions must be abundant ⁶.

According to the advances in technology and knowledge of human disease, the transfer of these benefits in advance has great expectations, and moreover, the challenges of the pharmaceutical industry are great and exhausting ⁷. The costs and time required for the development of a medicine have made working with the industry less attractive to researchers ⁸, which is accentuated by the global economic crisis secondary to the pandemic.

Due to this, the strategy that could offer results in less time, with better levels of safety and at a lower cost is known as “Drug Repurposing”. This strategy consists of identifying new uses of approved drugs different from the original therapeutic indication. ⁹. This strategy differs from “Off Label” use in that it requires research and development to gain regulatory agency approval ¹⁰. It has several advantages; first, the risk of toxicity failure is low because the drug is safe enough and has been tested in preclinical and early human studies. Second, the time is reduced since preclinical and safety studies have already been carried out, and third, the necessary resources are less ¹¹. These advantages can generate a quick return on investment (300 million dollars in repositioning against 2-3 trillion dollars in the study of a new molecule) and in case of failure there is less loss ¹². About 3422 medicines that have been described in human clinical trials are in the marketing phase around the world, thus, the possibility of selection is wide ¹³.

Three actors have been identified in the field of repurposing: the academy, the research institutes and, of course, the pharmaceutical industry, each with its own characteristics. In academia and research institutes, there is less need for economic or commercial success, but they depend on securing resources from the state or other funder. Furthermore, the pharmaceutical industry has the complete platform to do the trials, but they are not always motivated because many countries do not recognize second-use patents ¹⁴.

Among the diseases in which researchers are using repositioning are cancer (thalidomide, metformin, chlorpromazine, digoxin, doxycycline) ^15-17, neurodegenerative diseases such as Parkinson’s (ambroxol, amantadine) ¹⁸, viral and infectious diseases (azithromycin, mycophenolic acid) ^19,20, asthma and allergies (ruxolitinib, imatinib, metformin) ²¹, neuropathic pain (gabapentin, amitriptyline) ²², kidney disease (levosimendan, allopurinol) ²³ and cardiovascular-pulmonary disease (tadalafil, fasudil) ^24-26.

The best examples of Drug Repurposing are in the cardiovascular system, from the use of aspirin as a platelet antiplatelet ²⁷ to the approval of Sildenafil, a drug previously used for erectile dysfunction that is now the first-line treatment in pulmonary hypertension. ^28,29.

Therapeutic alternatives in the management of SARS-CoV-2 infection

Since the first reports of coronavirus’s infections began to be known in late 2019 in China, studies have been started with drugs approved for other diseases. To date, there are 908 studies registered at www.clinicaltrials.gov, of which 560 are intervention studies that include clinical trials of repositioning in Covid-19, mostly from China. ³⁰.

Chloroquine, which was initially approved for the treatment of malaria ³¹, and which has been studied in approximately 400 diseases (with the first trial being carried out in 1946) ³², was evaluated for the treatment of SARS-CoV infection in 2003 ³³ and now in the SARS-CoV-2 pandemic ³⁴. Hydroxychloroquine, a chloroquine analogous, is a medicine widely used in the treatment of systemic autoimmune diseases ³⁵, being currently the most studied drug for treating COVID-19. Hydroxychloroquine is metabolized in the liver and is eliminated via the kidneys after 30 to 50 days. It is a 4-aminoquinolone with immunosuppressive, anti-autophagic and antimalarial properties. Although its mechanism of action is unknown, it can suppress immune function by interfering with antigen processing and presentation ^36,37. It is a medicine with a higher risk / benefit than chloroquine and allows higher doses to be used. In COVID 19, 133 clinical trials are registered, taking different degrees of severity, ranging from prophylactic use in the general population and in health workers ³⁸ to patients with severe acute respiratory syndrome (SARS). It is believed that, as happened with SARS-CoV, it could reduce the viral load of patients in pre and post infection stages, in addition to reducing the expression of CD154 in T cells ³⁹.

The results obtained so far are controversial, since on the one hand it has been reported that treatment with hydroxychloroquine did not generate additional effects to standard treatment and instead increased the risk of ventilatory support ⁴⁰, and on the other, French researchers documented that the addition of azithromycin to hydroxychloroquine treatment can generate synergistic effects by improving the elimination of the virus. It is necessary to clarify that the previously described are preliminary studies and that they require large sample sizes to generate a definitive conclusion ⁴¹. This mixture is being studied for treating patients with and without complications (Table 1).

Antivirals are other group of drugs being tested to combat the pandemic. In Wuhan, more than 85% of patients received medications such as Oseltamivir, Remdesivir, Ganciclovir, Lopinavir/Ritonavir and Ribavirin ^42,43. These antivirals have been combined with systemic corticosteroids and inhalation of interferon in the treatment of patients with severe complications ⁴⁴. Satisfactory results were achieved using Remdesivir, obtaining clinical improvement in 68% of patients with SARS, with a significant reduction in mortality, days of hospitalization and days of mechanical ventilation. This study was developed with patients from the United States, Japan, Italy, Austria, France, Germany, the Netherlands, Spain and Canada ⁴⁵, however, just as it happens with hydroxychloroquine, its effectiveness should be contrasted with more clinical trials and in more patients.

Immunotherapy has shown effectiveness in the treatment of infectious diseases; thus, the use of monoclonal antibodies constitutes a new stage in their prevention, due to its versatility and specificity. ^46,47. Therapy with antibodies that bind to the angiotensin 2-converting enzyme receptor may block the virus from entering the cell ^48,49. Currently there are 15 trials registered in Clinical Trials that are testing this hypothesis, using monoclonal antibodies, which are being performed only in complicated patients, none in stable patients or in prophylaxis.

Famotidine, a histamine H2 receptor antagonist; have shown effects on inmune system ⁵⁰ It is currently being studied and results obtained in patients in China can generate positive expectations, currently in the United States, they are in the recruitment phase; the reduction of the mortality and its low probability of adverse effects generates an attractiveness for researchers ^51,52. Glucocorticoids (Methylprednisolone and Dexamethasone) as monotherapy with discrete results ⁵³, or accompanying other medications such as thalidomide ⁵⁴; anti-inflammatories such as colchicine ⁵⁵, or drugs that do not yet have a clear mechanism of action such as pirfenidone, are being studied to be repositioned in Covid-19. China and the United States lead most of the trials, however, countries such as Italy, Spain, the United Kingdom, Canada, and Denmark ⁵⁶ also participate in the search for a medicine that could change the course of a crisis that can only be compared to the world wars of the early twentieth century. With all the limitations, repositioning tests are an attractive strategy, providing the possibility of combinations that seek synergism ⁵⁷. The search for these treatments is an obligation acquired by science and public health.

Research strategies to evaluate drug repositioning

There are controversies about the maximum and minimum recommendations and the essential requirements to conduct a good clinical trial of drug repositioning. The infrastructure, the preparation of products, materials, protocols, forms of reporting, databases, statistics, monitoring and reports, as well as laboratory evaluations are often insufficient ⁵⁸ and their availability is reserved, a situation that is accentuated with the pandemic _⁵⁹, therefore, the maximum recommendations should be flexible when approving studies.

The COVID-19 Clinical Research Coalition initiative establishes flexible guidelines that allow research to be carried out. This initiative shows that the research agenda should not be controlled, but facilitated, for which 4 objectives are proposed: first, to facilitate rapid reviews by ethics committees and regulatory agencies; second, to facilitate permits for the importation of medicines and materials, as was done with the Ebola vaccine trials; third, to ensure simple data collection strategies sufficient to strengthen efficacy analyses; and fourth, to provide a reference framework for governments to share the results obtained before publishing in scientific journals ⁶⁰. Compliance with these objectives will allow studies to be carried out in shorter times and with enough resources to ensure quality. Thus, the Food and Drug Administration (FDA) in the United States ⁶¹, and the INVIMA in Colombia, approved the use of hydroxychloroquine in hospitalized patients via fast track.

To move forward and generate fast and reliable results, it might be considered doing a proof of concept, double blind, add-on event-driven. In Add-On studies, one group receives the standard treatment, while the other group receive the drug to be tested in addition to the standard treatment. Using these studies, the comparison of relative or absolute efficacy could be obtained in short periods of time ⁶². The FDA Recognizes Add-On designs in Cancer, Behavioural Disorders, HIV, and Heart Failure studies ⁶³. In this methodology processes are developed over time and results are produced that then turn into events that ultimately lead to additional results as the narrative unfolds. ⁶⁴.

Unlike most diseases, there are currently no proven treatments to treat COVID-19. Therefore, there are 183 registered studies that use placebo as a comparator of the drug to be repurposed ^65-67. The ethics committees are expected to be willing to meet the needs that the ethical conflict the placebo group generates, with enough updating to control the ethical aspects without preventing the execution of the projects. Probably there will be problems, one of them would be the entry of participants linked to the health system who could “sabotage” the study, taking the drug without belonging to the experimental group or trying another drug at the same time in the hope of avoiding a contagion or treating the illness.

Conclusion

The dissemination of these findings should be responsible, avoiding anecdotal evidence ⁶⁸. Differences in plasma concentrations of medicines from person to person could generate more adverse reactions, and therefore, rapid clinical trials but with high scientific quality should be carried out ³⁸. While the vaccine arrives, the repositioning of medicines will continue to be the first research strategy against this crisis that has changed the rhythm of life of humanity.

References

WHO. Coronavirus Disease (COVID-19) - events as they happen; 2020. Available from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/events-as-they-happen.

Li G, De Clercq E. Therapeutic options for the 2019 novel coronavirus (2019-nCoV). Nat Rev Drug Discov. 2020;19(3):149-50. Doi: 10.1038/d41573-020-00016-0

Prompetchara E, Ketloy C, Palaga T. Immune responses in COVID-19 and potential vaccines: lessons learned from SARS and MERS epidemic. Asian Pac J Allergy Immunol. 2020;38(1):1-9. Doi: 10.12932/ap-200220-0772

Della G, Jonsdottir I, Lewis D. Challenges in early clinical development of adjuvanted vaccines. Vaccine. 2015;33:47-51. Doi: 10.1016/j.vaccine.2015.02.031

Esch EW. BA, Huh D. Organs-on-chips at the frontiers of drug discovery. Nat Rev Drug Discov. 2015;14(4):248-60. Doi: 10.1038/nrd4539

Lythgoe MP, Rhodes CJ, Ghataorhe P, Attard M, Wharton J, Wilkins MR. Why drugs fail in clinical trials in pulmonary arterial hypertension, and strategies to succeed in the future. Pharmacol Therapeutics. 2016;164:195-203. Doi: 10.1016/j.pharmthera.2016.04.012

Waring MJ, Arrowsmith J, Leach AR, Leeson PD, Mandrell S, Owen RM, et al. An analysis of the attrition of drug candidates from four major pharmaceutical companies. Nat Rev Drug Discov. 2015;14(7):475-88. Doi: 10.1038/nrd4609

Pushpakom S, Iorio F, Eyers P, Escott K, Hopper S, Wells A, et al. Drug repurposing: progress, challenges and recommendations. Nat Rev Drug Discov. 2019;18(1):41-58. Doi: 10.1038/nrd.2018.168

Ashburn T, Thor K. Drug Repositioning: Identifying and developing new uses for existing drugs. Nat Rev Drug Discov. 2004;3(8):673-83. Doi: 10.1038/nrd1468

Minghetti P, Lanati E, Godfrey J, Solà-Morales O, O. W, S. S. From off-label to repurposed drug in non-oncological rare diseases: definition and state of the art in selected EU countries. MA@PoC. 2017;1 (1): e87-e97. Doi: 10.5301/maapoc.0000016

Breckenridge A, Jacob R. Overcoming the legal and regulatory barriers to drug repurposing. Nat Rev Drug Discov. 2019;18(1):1-2. Doi: 10.1038/nrd.2018.92

Nosengo N. Can you teach old drugs new tricks? Nature. 2016;534(7607):314-6. Doi: 10.1038/534314a

Corsello S, Bittker J, Liu Z, Gould J, McCarren P, Hirschman J, et al. The drug repurposing hub: a next-generation drug library and information resource. Nat Med. 2017;23(4):405-8. Doi: 10.1038/nm.4306

Cha Y, Erez T, Reynolds I, Kumar D, Ross J, Koytiger G, et al. Drug repurposing from the perspective of pharmaceutical companies. British J Pharmacology. 2018;175(2):168-80. Doi: 10.1111/bph.13798

Sleire L, Førde HE, Netland IA, Leiss L, Skeie BS, PØ E. Drug repurposing in cancer. Pharmacol Res. 2017;124:74-91 Doi: 10.1016/j.phrs.2017.07.013

Chen PC, Liu X, Y. L. Drug Repurposing in anticancer reagent development. Comb Chem High Throughput Screen. 2017;20(5):395-402. Doi: 10.2174/1386207319666161226143424

Gilbert DC, Vale C, Haire R, Coyle C, Langley RE. Repurposing vitamin D as an anticancer drug. Clin Oncol (R Coll Radiol). 2016;28(1):36-41. Doi: 10.1016/j.clon.2015.10.004

Athauda D, Foltynie T. Drug repurposing in Parkinson's disease. CNS drugs. 2018;32(8):747-61. Doi: 10.1007/s40263-018-0548-y

Mercorelli B, Palù G, Loregian A. Drug repurposing for viral infectious diseases: how far are we? Trends Microbiol. 2018;26(10):865-76. Doi: 10.1016/j.tim.2018.04.004

Konreddy AK, Rani GU, Lee K, Choi Y. Recent drug-repurposing-driven advances in the discovery of novel antibiotics. Curr Med Chem. 2019;26(28):5363-88. Doi: 10.2174/0929867325666180706101404

Kruse RL, Vanijcharoenkarn K. Drug repurposing to treat asthma and allergic disorders: progress and prospects. Allergy. 2018;73(2):313-22. Doi: 10.1111/all.13305

Sisignano M, Parnham MJ, Geisslinger G. Drug repurposing for the development of novel analgesics. Trends Pharmacological Sci. 2016;37(3):172-83. doi: 10.1016/j.tips.2015.11.006

Panchapakesan U, Pollock C. Drug repurposing in kidney disease. Kidney Int. 2018;94(1):40-8. Doi: 10.1016/j.kint.2017.12.026

Walton GM, Stockley JA, Griffiths D, Sadhra CS, Purvis T, Sapey E. Repurposing treatments to enhance innate immunity. Can statins improve neutrophil functions and clinical outcomes in COPD? J Clin Med. 2016;5(10):89. Doi: 10.3390/jcm5100089

George CH, Mitchell AN, Preece R, Bannister ML, Yousef Z. Pleiotropic mechanisms of action of perhexiline in heart failure. Expert Opin Ther Pat. 2016;26(9):1049-59. Doi: 10.1080/13543776.2016.1211111

Korkmaz-Icöz S, Radovits T, Szabó G. Targeting Phosphodiesterase 5 as a Therapeutic Option Against Myocardial Ischaemia/Reperfusion Injury and for Treating Heart Failure. Br J Pharmacol. 2018;175(2):223-31. Doi: 10.1111/bph.13749

Fuster V, Chesebro J. Aspirin for primary prevention of coronary disease. Eur Heart J. 1995; Suppl E:16-20. Doi: 10.1093/eurheartj/16.suppl_E.16

Barnett CF, Machado RF. Sildenafil in the treatment of pulmonary hypertension. Vasc Health Risk Manag. 2006;2(4):411-22. Doi: 10.2147/vhrm.2006.2.4.411

Baker NC, Ekins S, Williams AJ, Tropsha A. A bibliometric review of drug repurposing. Drug Discov Today. 2018;23(3):661-72. Doi: 10.1016/j.drudis.2018.01.018

NIH. COVID 19 - List Results - ClinicalTrials.gov 2020. Available from: https://clinicaltrials.gov/

Schlitzer M. Malaria Chemotherapeutics Part I: History of antimalarial drug development, currently used therapeutics, and drugs in clinical development. ChemMedChem. 2007;2(7):944-86. Doi: 10.1002/cmdc.200600240

Loeb F, Clark W, Coatney G. Activity of a New Antimalarial Agent, Chloroquine (SN 7618). J Am Med Assoc. 1946;130:1069. Doi: 10.1001/jama.1946.02870160015006

Keyaerts E, Vijgen L, Maes P, Neyts J, Van M. In vitro inhibition of severe acute respiratory syndrome coronavirus by chloroquine. Biochem Biophys Res Commun. 2004;323(1):264-8. Doi: 10.1016/j.bbrc.2004.08.085

Gao J, Tian Z, Yang X. Breakthrough: chloroquine phosphate has shown apparent efficacy in treatment of COVID-19 associated pneumonia in clinical studies. Biosci Trends. 2020;14(1):72-3. Doi: 10.5582/bst.2020.01047

Costedoat-Chalumeau N, Dunogué B, Morel N, Guern V, Guettrot-Imbert G. Hydroxychloroquine: a multifaceted treatment in Lupus. Presse Med. 2014;43(6 Pt 2): e167-e180. Doi: 10.1016/j.lpm.2014.03.007

PubChem. Hydroxychloroquine compound summary; 2020. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/Hydroxychloroquine

Hughes G. Hydroxychloroquine: an update. Lupus. 2018;27(9):1402-3. Doi: 10.1177/0961203318787040

Yazdany J, Kim A. Use of Hydroxychloroquine and Chloroquine during the COVID-19 pandemic: What Every Clinician Should Know. Ann Intern Med. 2020(3):1-3. Doi: 10.7326/M20-1334

Zhou D, Dai S, Tong Q. COVID-19: A Recommendation to examine the effect of hydroxychloroquine in preventing infection and progression. J Antimicrob Chemother. 2020; ahead of print Doi: 10.1093/jac/dkaa114

Barbosa J, Kaitis D, Freedman R, Le K, Lin X. Clinical outcomes of hydroxychloroquine in hospitalized patients. BMJ. 2020; Doi: 10.1101/2020.03.22.20040758

Gautret P, Lagier J, Parola P, Hoang V, Meddeb L, Mailhe M, et al. Hydroxychloroquine and Azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial. Int J Antimicrob Agents. 2020:105949. doi: 10.1016/j.ijantimicag.2020.105949

Cunningham AG, H. Koh, D. Treatment of COVID-19: old tricks for new challenges. Crit Care. 2020;24:91. doi: 10.1186/s13054-020-2818-6

Lai C, Shih T, Ko W, Tang H, Hsueh P. severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Coronavirus disease-2019 (COVID-19): the epidemic and the challenges. Int J Antimicrob Agents. 2020;55(3):105924. doi: 10.1016/j.ijantimicag.2020.105924

Liu Y, Li J, Feng Y. Critical care response to a hospital outbreak of the 2019-nCoV infection in Shenzhen, China. Crit Care. 2020;24(1):56. doi: 10.1186/s13054-020-2786-x

Grein J, Ohmagari N, Shin D, Diaz G, Asperges E, Castagna A, et al. Compassionate use of remdesivir for patients with severe Covid-19. N Engl J Med. 2020. doi: 10.1056/NEJMoa2007016

Sui J, Li W, Roberts A, Matthews LJ, Murakami A, Vogel L, et al. Evaluation of human monoclonal antibody 80R for immunoprophylaxis of severe acute respiratory syndrome by an animal study, epitope mapping, and analysis of spike variants. J Virol. 2005;79(10):5900-6. doi: 10.1128/JVI.79.10.5900-5906.2005

Both L, Banyard AC, van Dolleweerd C, Wright E, Ma JKC, Fooks AR. Monoclonal antibodies for prophylactic and therapeutic use against viral infections. Vaccine. 2013;31(12):1553-9. doi: 10.1016/j.vaccine.2013.01.025

Masters PS. The molecular biology of coronaviruses. Adv Virus Res. 2006;66:193-292. doi: 10.1016/S0065-3527(06)66005-3

Shanmugaraj B, Siriwattananon K, Wangkanont K, Phoolcharoen W. Perspectives on monoclonal antibody therapy as potential therapeutic intervention for coronavirus disease-19 (COVID-19). Asian Pac J Allergy Immunol. 2020;38(1):10-8. Doi: 10.12932/AP-200220-0773.

Jafarzadeh A, Nemati M, Khorramdelazad H, Hassan ZM. Immunomodulatory properties of cimetidine: Its therapeutic potentials for treatment of immune-related diseases. Int Immunopharmacol. 2019;70:156-166. doi:10.1016/j.intimp.2019.02.026

Rogosnitzky, M., Berkowitz, E., & Jadad, A. R. Delivering Benefits at Speed through Real-World Repurposing of Off-Patent Drugs: The COVID-19 Pandemic as a Case in Point. JMIR Public Health Surveill. 2020; Epub ahead of print. Doi: 10.2196/1999.

Borrel B. New York clinical trial quietly tests heartburn remedy against coronavirus. Science; 2020. Available from: https://www.sciencemag.org/news/2020/04/new-york-clinical-trial-quietly-tests-heartburn-remedy-against-coronavirus.

Zhou Y, Qin Y, Lu Y, Sun F, Yang S, Harypursat V, et al. Effectiveness of glucocorticoid therapy in patients with severe novel coronavirus pneumonia: protocol of a randomized controlled trial. Chin Med J. 2020; ahead of print. Doi: 10.1097/CM9.0000000000000791

Chen C, Qi F, Shi K, Li Y, Li J, Chen Y, et al. Thalidomide combined with low-dose glucocorticoid in the treatment of COVID-19 pneumonia. Preprints2020, 2020020395 Available from: https://www.preprints.org/manuscript/202002.0395/v1

Deftereos S, Siasos G, Giannopoulos G, Vrachatis D, Angelidis C, Giotaki S, et al. The greek study in the effects of colchicine in COVID-19 complications prevention (GRECCO-19 Study): rationale and study design. Hellenic J Cardiol. 2020; ahead of print. doi: 10.1016/j.hjc.2020.03.002

Kupferschmidt K, Cohen J. Race to find COVID-19 treatments accelerates. Science. 2020;367(6485):1412-3. Doi: 10.1126/science.367.6485.1412

Rosa S, Santos W. Clinical trials on drug repositioning of COVID-19. Rev Panam Salud Publica. 2020;44:e40 Doi: 10.26633/RPSP.2020.40

Wilson M, Fleming K, Kut IM, Looi L, Lag ON, Ru K. Access to pathology and laboratory medicine services: a crucial gap. Lancet. 2018;391(10133):1927-38. Doi: 10.1016/S0140-6736(18)30458-6

Editor. COVID-19: what science advisers must do now. Nature. 2020; 579: 319

Abdullah N, Abril M, Amare A, Amuasi J, Auewarakul P, Augier A,et al. Global Coalition to Accelerate COVID-19 Clinical research in resource-limited settings. Lancet. 2020;395(10233):1322-1325. Doi: 10.1016/S0140-6736(20)30798-4

FDA. Fact sheet for health care providers emergency use authorization (EUA) of hydroxychloroquine sulfate supplied from the strategic national stockpile for treatment of Covid-19 in certain hospitalized patients; 2020. Available from: https://www.fda.gov/media/136535/download

Charles H, Evans J, Suzanne T. Statistical approaches to analysis of small clinical trials: National Academies Press (US); 2001. Available from: https://www.nap.edu/read/10078/chapter/5

Brody T. Clinical Trials - 2nd Edition: Elsevier; 2016. Available from: https://www.elsevier.com/books/clinical-trials/brody/978-0-12-804217-5.

Mills A, Durepos G, Wiebe E. Event-driven research. In: Encyclopedia of Case Study Research. SAGE; 2010. Available from: https://methods.sagepub.com/reference/encyc-of-case-study-research/n133.xml. doi: 10.4135/9781412957397

Leng Z, Zhu R, Hou W, Feng Y, Yang Y, Han Q, et al. Transplantation of ACE2 - mesenchymal stem cells improves the outcome of patients with COVID-19 pneumonia. Aging Dis. 2020;11(2):216-28. Doi: 10.14336/AD.2020.0228

ClinicalTrial.gov. Hydroxychloroquine versus placebo in COVID-19 patients at risk for severe disease. University Hospital, Angers; 2020. Available from: https://clinicaltrials.gov/ct2/show/NCT04325893.

ClinicalTrial.gov. Evaluation of the efficacy and safety of sarilumab in hospitalized patients with COVID-19. Regeneron Pharmaceuticals; 2020 . Available from: https://clinicaltrials.gov/ct2/show/NCT04315298.

Zimmer C. Scientists identify 69 drugs to test against the Coronavirus. New York Times. 2020 20200322. Available from: https://www.nytimes.com/2020/03/22/science/coronavirus-drugs-chloroquine.html

Author notes

*Corresponding author: Vicente Benavides-Cordoba. Código Postal: 760043. E-mail: vicente.benavides@correounivalle.edu.co.