In vivo activity of repurposed amodiaquine as a host-targeting therapy for the treatment of anthrax

Authors: SHILMAN, MIKHAIL - Keck Graduate Institute; BARTOLO, GLORIA - Keck Graduate Institute; ALAMEH, SALEEM - Keck Graduate Institute; SLAY, RAYMOND M. - Nih, National Institutes Of Allergy And Infectious Diseases; PETERSON, JOHNNY W. - University Of Texas Medical Branch; LAWRENCE, WILLIAM S - University Of Texas Medical Branch; PEEL, JENNIFER E. - University Of Texas Medical Branch; SIVASUBRAMANI, SATHEESH K. - Naval Medical Research Center; BEASLEY, DAVID W.C. - University Of Texas Medical Branch; COTE, CHRISTOPHER K. - Us Army Medical Research Institute Of Infectious Diseases; DEMONS, SAMANDRA T. - Us Army Medical Research Institute Of Infectious Diseases; HALASAHORIS, STEPHANIE A. - Us Army Medical Research Institute Of Infectious Diseases; MILLER, LYNDA L. - Us Army Medical Research Institute Of Infectious Diseases; KLIMKO, CHRISTOPHER P. - Us Army Medical Research Institute Of Infectious Diseases; SHOE, JENNIFER L. - Us Army Medical Research Institute Of Infectious Diseases; FETTERER, DAVID P. - Us Army Medical Research Institute Of Infectious Diseases; MCCOMB, RYAN - Keck Graduate Institute; HO, CHI-LEE C. - University Of California (UCLA); BRADLEY, KENNETH A. - University Of California (UCLA); HARTMANN, STELLA - Keck Graduate Institute; Cheng, Luisa; CHUGUNOVA, MARINA - Claremont Colleges; KAO, CHIU-YEN - Claremont Colleges; TRAN, JENNIFER - Keck Graduate Institute; DERBEDROSSIAN, ARAM - Keck Graduate Institute; ZILBERMINTZ, LEEOR - Keck Graduate Institute; AMALI-ADEKWU, EMIENE - Keck Graduate Institute; LEVITIN, ANASTASIA - Keck Graduate Institute; WEST, JOEL - Keck Graduate Institute

Submitted to: ACS Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2021
Publication Date: 7/4/2021
Citation: Shilman, M.M., Bartolo, G., Alameh, S., Slay, R., Peterson, J., Lawrence, W., Peel, J., Sivasubramani, S., Beasley, D., Cote, C., Demons, S., Halasahoris, S., Miller, L., Klimko, C., Shoe, J., Fetterer, D., Mccomb, R., Ho, C., Bradley, K., Hartmann, S., Cheng, L.W., Chugunova, M., Kao, C., Tran, J., Derbedrossian, A., Zilbermintz, L., Amali-Adekwu, E., Levitin, A., West, J. 2021. In vivo activity of repurposed amodiaquine as a host-targeting therapy for the treatment of anthrax. ACS Infectious Diseases. 7(8):2176-2191. https://doi.org/10.1021/acsinfecdis.1c00190.
DOI: https://doi.org/10.1021/acsinfecdis.1c00190

Interpretive Summary: Bacillus anthracis is the causative agent of anthrax and a Select Agent. Few therapeutics are available to combat anthrax. Current treatments involve the use of antibiotics and antibodies, neither of which are highly effective. In this study, the small molecule drug amodiaquine (AQ) was repurposed for use as a treatment for anthrax. AQ was shown to inhibit anthrax host cell entry. When given orally, AQ doubled the survival of mice infected subcutaneously with B. anthracis to 70% of the animals. In rabbits given 200 times the LD50 of aerosolized B. anthracis, AQ delayed death, and doubled the survival of previously infected animals when given together with the antibiotic levofloxacin. AQ not only worked by blocking the cellular uptake of anthrax toxin but was found to increase the activity of immune cells such as macrophages to kill the bacilli. This study establishes AQ as a repurposed host-targeted therapy and adds to the arsenal of tools for the treatment of anthrax.

Technical Abstract: Anthrax is caused by Bacillus anthracis and often results in high mortality due to anthrax toxin. The FDA has recently approved several toxin-neutralizing antibodies. However, these toxin-directed drugs are potentially ineffective against naturally- or intentionally-mutated strains of Bacillus. We previously discovered that an approved small molecule, amodiaquine (AQ), and its active metabolite, desethyl-amodiaquine (DEAQ), act as host-oriented inhibitors of anthrax toxin entry into host cells by targeting endocytosis-mediating Cathepsin B. In this study, we determined the pharmacokinetics and safety of AQ and DEAQ in mice, rabbits, and humans, as well as demonstrated the efficacy of AQ in mouse, rabbit, and fly models of anthrax infection. In the therapeutic-intervention studies, when administered orally at 10 mg/kg/day for five days starting at the time of the infection, AQ doubled the survival of mice infected subcutaneously with B. anthracis dose lethal to 70% of the animals (LD70). In rabbits challenged with 200 times the LD50 of aerosolized B. anthracis, AQ delayed the death as monotherapy, and doubled the survival of previously infected animals that received a suboptimal amount of antibacterial levofloxacin. Surprisingly, the anthrax efficacy of AQ relies on two host-directed mechanisms. In addition to blocking the endocytosis of anthrax toxin, AQ also decreases bacterial count in the plasma of infected animals by increasing the ability of macrophages, but not neutrophils, to kill the bacilli, without directly affecting the bacterial growth. This antibacterial host-directed AQ efficacy was validated in the toxin-independent Drosophila model of Bacillus infection. Lastly, a systematic literature review of the safety and pharmacokinetics of AQ and DEAQ in humans from over 2,000 published articles revealed that AQ is likely safe when taken as prescribed, and its pharmacokinetics predicts a favorable anthrax efficacy in humans. This study establishes AQ as a repurposed host-targeted therapy for the treatment of anthrax.