Abstract: bioRxiv preprint doi: https://doi.org/10.1101/2021.11.04.467077; this version posted November 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 2 The oral protease inhibitor (PF-07321332) protects Syrian hamsters against infection with SARS-CoV2 variants of concern 3 4 5 6 Rana Abdelnabi1,2, Caroline S. Foo1,2, Dirk Jochmans1,2, Laura Vangeel1,2, Steven De Jonghe1, Patrick Augustijns3, Raf Mols3, Birgit Weynand4, Thanaporn Wattanakul5, Richard M. Hoglund5,6, Joel Tarning5,6, Charles E. Mowbray7, Peter Sjö7, Fanny Escudié7, Ivan Scandale7, Eric Chatelain7, Johan Neyts1,2*. 7 1. KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for 8 9 10 11 Medical Research, Laboratory of Virology and Chemotherapy, B-3000 Leuven, Belgium. 2. Global Virus Network, GVN, Baltimore, Maryland, USA. 3. KU Leuven, Department of Pharmaceutical and Pharmacological Sciences, Drug Delivery & Disposition, Box 921, 3000 Leuven, Belgium. 12 4. KU Leuven Department of Imaging and Pathology, Translational Cell and Tissue Research, B-3000 13 5. Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 14 15 16 17 Bangkok, Thailand 6. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK 7. Drugs for Neglected Diseases initiative, Geneva, Switzerland 18 19 *To whom correspondence may be addressed. Prof. Johan Neyts, Email: johan.neyts@kuleuven.be. 20 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.11.04.467077; this version posted November 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 21 Abstract 22 There is an urgent need for potent and selective antivirals against SARS-CoV-2. Pfizer developed PF- 23 07321332 (PF-332), a potent inhibitor of the viral main protease (Mpro, 3CLpro) that can be dosed 24 orally and that is in clinical development. We here report that PF-332 exerts equipotent in vitro activity 25 against the four SARS-CoV-2 variants of concerns (VoC) and that it can completely arrest replication of 26 the alpha variant in primary human airway epithelial cells grown at the air-liquid interface. Treatment 27 of Syrian Golden hamsters with PF-332 (250 mg/kg, twice daily) completely protected the animals 28 against intranasal infection with the beta (B.1.351) and delta (B.1.617.2) SARS-CoV-2 variants. 29 Moreover, treatment of SARS-CoV-2 (B.1.617.2) infected animals with PF-332 completely prevented 30 transmission to untreated co-housed sentinels. 31 32 Keywords 33 SARS-CoV-2; PF-07321332, Variants of concerns (VoC); Antivirals; Mpro inhibitors, 2 bioRxiv preprint doi: https://doi.org/10.1101/2021.11.04.467077; this version posted November 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.