Broad-spectrum antiviral drug

Broad-spectrum antiviral drugs (or broad-spectrum antiviral agents, BSAA) are a class of antiviral drugs, which target and inhibit the replication and development of a broad range of viral pathogens. BSAAs work by inhibiting viral proteins (such as polymerases, proteases, or reverse transcriptases) or by targeting host cell proteins and processes exploited by the virus during infection.
Many BSAs are found showing efficacy against a given virus outside their original indication, showing antiviral activity against other viruses than originally investigated (such as remdesivir and ritonavir/lopinavir) or outside their original therapeutic indications, for example, antibacterials, like azithromycin, antihelminthics, like niclosamide, and antiprotozoals, like emetine. This makes BSAs potential candidates for drug repurposing. Repurposing of BSAs will allow for quicker, cheaper and more efficient development of antivirals than "de novo" drug development. BSAs that have been successfully repurposed outside their original therapeutic indications are known as broad-spectrum therapeutics.
BSAs are potential candidates for treatment of medically important and emerging viruses, such as influenzas, HIV, filoviruses, such as ebola and marburg viruses, and the coronaviruses, SARS-CoV, MERS-CoV and more recently SARS-CoV-2. Efforts in drug repurposing for SARS-CoV-2 is currently underway.
As of 2020, there are 120 known BSA candidates in varying stages of development, effective against 78 human viruses.