The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to threaten human health and public safety worldwide.

As of July 2022, the infection has affected approximately 561 million individuals globally, along with being responsible for 6.3 million deaths. Although several vaccines against SARS-CoV-2 have been developed, their efficacy is challenged due to the emergence of new variants. Therefore, new anti-SARS-CoV-2 therapeutics must be developed along with vaccination to treat COVID-19 patients.

Currently, clinical trials are being conducted with two new anti-SARS-CoV-2 pills, Lagevrio (Molnupiravir) and Paxlovid. However, the long-term safety of these drugs is unknown. Moreover, the anti-viral activity of these drugs can be lowered due to structural changes in the target viral enzyme. Therefore, a broad spectrum antiviral agent is required that can be used for many viruses such as paramyxoviruses, flaviviruses, filoviruses, picornaviruses, togaviruses, and bunyaviruses which may lead to future pandemics.

One such approach is to use niclosamide (NIC) which is known to possess broad-spectrum antiviral activity. A 2021 study reported that NIC was capable of inhibiting SARS-CoV-2 proliferation through autophagy. However, NIC has low aqueous solubility, which could trouble the systemic absorption of orally administered NIC. This challenge can be overcome by chemical modification of NIC that could increase its solubility or a drug repurposing technology with pharmaceutically inert substances.