Repurposed Medicines for Viruses With Epidemic or Pandemic Potential: A Horizon Scan.

Viruses such as Ebola, Marburg, influenza, mpox, MERS-CoV, SARS-CoV, and SARS-CoV-2 may be considered pathogens of epidemic or pandemic concern. Developing novel antiviral medicines can be time-consuming and resource intensive. Repurposing existing medicines with known or potential antiviral activity offers a faster, cost-effective strategy to expand treatment options during public health emergencies. This scan aimed to map current investigational activity involving repurposed medicines for these viruses. A horizon scanning approach was employed, starting with a targeted search in Embase followed by a systematic search of ClinicalTrials.gov to identify developmental stages of relevant technologies. Eligible technologies included UK- or EU-licensed medicines being investigated for antiviral use, while vaccines, unlicensed medicines, and treatments already approved for the target viruses were excluded. From the literature, 196 repurposed technologies were identified, and the expanded search on the clinical trials registry revealed 58 technologies in active clinical development. Interventional trial activity was limited to influenza and SARS-CoV-2, with 29 technologies for SARS-CoV-2 and two influenza technologies advancing to phase III evaluation. For other viruses, candidate repurposed technologies were identified only at preclinical or exploratory stages. Frequently investigated pharmacological classes included direct-acting antivirals, immunomodulators, and anti-inflammatory agents. While repurposing represents a potentially rapid strategy for therapeutic deployment, inclusion in this horizon scan does not imply clinical efficacy. Rigorous preclinical validation, pharmacokinetic feasibility assessment, and mechanistic confirmation remain essential before clinical translation.