ACE2 immunodecoys for long-lasting immunoprophylaxis against sarbecovirus and merbecoviruses that target human ACE2 - While vaccines are readily available for SARS-CoV-2, there continues to be significant demand for prophylaxis that are potent and not at risk for viral escape to better protect vulnerable populations. In addition, there is emerging evidence that a number of bat sarbecoviruses and merbecoviruses can use human ACE2 (hACE2) as an entry receptor to infect human cells. Thus, there is also a need to advance effective immunoprophylaxis to protect against such zoonotic coronaviruses with pandemic potential. We have previously advanced an ACE2-immunodecoy as treatment for SARS-CoV-2 infections. Instead of the common approach pursued by many investigators to affinity mature ACE2 to enhance binding to SARS-CoV-2 Spike, we instead sought to optimize the linkage between the extracellular fragment of human ACE2 and IgG1-Fc (ALFc) to promote improved bivalent binding to SARS-CoV-2 Spike. Similar to other ACE2- decoys, ALFc is not susceptible to viral escape. Unlike other ACE2-decoys, the preservation of the full human ACE2 sequence means ALFc is likely active against all ACE2-targeted viruses. We have demonstrated that ALFc maintains picomolar activity (comparable to many of the previous leading monoclonal antibodies that received emergency use authorization) against all variants of SARS-CoV-2, and is highly effective in a hamster challenge model. Importantly, the ALFc has outstanding bioprocessing attributes, including stability at high concentrations and exceptional productivity using cGMP CHO production cell line. These attributes have led the U.S. Army to select ALFc to be advanced into clinical development over other ACE2 decoys; GMP materials for clinical trials and GLP tox studies are currently underway, and a Phase 1 clinical study is planned for 2H 2025. In this proposal, we build on the success of ALFc as an inhaled therapy to establish the efficacy of ALFc as a systemic immunoprophylaxis that can prevent severe pulmonary disease in vulnerable populations. Specifically, the ALFc currently in development possess wildtype IgG1-Fc. For sustained immunoprophylaxis lasting >6-9 months, it is essential to utilize Fc with enhanced affinity to FcRn, such as YTE, LS and DHS mutations. In this proposal, we will first produce and characterize ALFcYTE, ALFcLS and ALFcDHS(Aim 1). We will evaluate their activity against a panel of hACE2-targeting viruses, including emerging bat sarbecoviruses and merbecoviruses, using both pseudotyped alphavirus vectors in cell-lines (BSL-2) and infectious virus clones in well-differentiated cultures of human airway epithelial cells (BSL-3) (Aim 2). Finally, we evaluate the ability of ALFc to protect against infectious clones of SARS-CoV-2 and SHC014-CoV challenge in human ACE2 transgenic mice (Aim 3). Successful completion of these studies will likely advance an intervention for providing immunoprophylaxis against future SARS-CoV-2 variants as well as other hACE2-targeted coronaviruses with pandemic potential.
