AUTHOR=Martinez Miguel Angel TITLE=Lack of Effectiveness of Repurposed Drugs for COVID-19 Treatment JOURNAL=Frontiers in Immunology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.635371 DOI=10.3389/fimmu.2021.635371 ISSN=1664-3224