LAUSR

Background: Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) uses full-length angiotensin converting enzyme 2 (ACE2) as a main receptor to enter target cells. The goal of this study was to demonstrate the preclinical efficacy of a novel soluble ACE2 protein with increased duration of action and binding capacity in a lethal mouse model of COVID-19. Methods: A human soluble ACE2 variant fused with an albumin binding domain (ABD) was linked via a dimerization motif hinge-like 4-cysteine dodecapeptide (DDC) to improve binding capacity to SARS-CoV-2. This novel soluble ACE2 protein (ACE2 1-618-DDC-ABD) was then administered intranasally and intraperitoneally to mice prior to intranasal inoculation of SARS-CoV-2 and then for two additional days post viral inoculation. Results: Untreated animals became severely ill and all had to be humanely euthanized by day 6/7 and had pulmonary alveolar hemorrhage with mononuclear infiltrates. In contrast, all but one mouse infected with a lethal dose of SARS-CoV-2 that received ACE2-1-618-DDC-ABD survived. In the animals inoculated with SARS-CoV-2 that were untreated, viral titers were high in the lungs and brain but virus was absent in the kidneys. However, some untreated animals had variable degrees of kidney proximal tubular injury with increased NGAL and TUNEL staining indicating attenuation of the proximal tubular brush border. In contrast, viral titers in the lung and brain were reduced or non-detectable in mice that received ACE2 1-618 DDCABD, and the animals developed only moderate disease as assessed by a near-normal clinical score, minimal weight loss, and improved lung and kidney injury Conclusions: This study demonstrates the preclinical efficacy of a novel soluble ACE2 protein, termed ACE2 1- 618-DDC-ABD, in a lethal mouse model of SARS-CoV-2 infection that causes severe lung injury as well as variable degrees of moderate proximal tubular injury.