Multidrug Treatment Using Kampo Medicine for Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne bunyavirus that causes acute febrile illness characterized by thrombocytopenia and a high mortality rate. Currently, no specific antiviral drugs have been approved for the treatment of SFTSV; therefore, identifying effective drugs against the disease and conducting clinical trials of these drugs are crucial. Drug repurposing is a well-established strategy for utilizing existing licensed drugs for newer indications, facilitating the shortest possible transition from bench to bedside. This approach demonstrated that favipiravir, zaltoprofen, ivermectin, and lurasidone, along with the phytochemicals licoflavone C and oleanolic　acid, are efficacious against the SFTSV. Glycyrrhiza, which contains licoflavone C in its extracts, is a component of the Kampo medicines Kakkon-to, Shosaiko-to and Saiko-keishi-to. Ginseng, which contains oleanolic acid in its extracts, is a component of Shosaiko-to and Saiko-keishi-to. Kampo medicine is a traditional Japanese medicine primarily consisting of organic plant-based ingredients, such as Glycyrrhiza, Ginseng, and others. Multidrug treatment is effective due to the synergistic effects resulting from the various mechanisms of action of the concerned drugs. Therefore, the combination of drugs, such as favipiravir, ivermectin, and Shosaiko-to may be more efficacious against the SFTSV.