Since the Spike protein on the surface of SARS coronavirus 2 (SARS-CoV-2) binds to the ACE2 receptor in human cells, the development of neutralizing proteins or antibodies targeting the receptor binding domain (RBD) of the spike protein is an important strategy for SARS-COV-2 therapy. We chose to develop molecularly-evolved soluble ACE2 protein on three grounds; 1) it can trap and neutralize the SARS-CoV-2 as neutralizing antibodies do, 2) it can supplement angiotensin II-converting enzyme activities that protect lung, heart, and kidneys of severe cases of infections and patients with underlying diseases, and 3) it may trap effectively SARS-CoV-2 mutants even though the mutations compromise the protection by neutralizing antibodies or vaccine. For the enhancement of ACE2 binding affinity to RBD, we used the 3D complex structure between ACE2 and RBD to select the major contributing ACE2 amino acids, a library targeting selected amino acids and random mutations were constructed and screened using yeast surface display. The engineered ACE2, EU129, was fused with the human IgG1 Fc for long half-life and viral clearance. The binding affinity of EU129 to RBD was increased by about 500-folds compared to ACE2 wild-type in SPR analysis, and the neutralizing activity was also increased by about 130-folds compared to ACE2 wild-type in surrogate virus neutralization test (sVNT). In addition, it was confirmed that the enzymatic activity of ACE2, which prevents organ damage due to SARS-CoV-2 infection in the human, is maintained at a level similar to that of ACE2 wild-type. In vitro assays using live SARS-CoV-2 virus and Vero E6 cells, EU129 was shown to be more effective in inhibiting viral infection and amplification than ACE2 wild-type, which was confirmed through protein and RNA level and cell morphology change of the live virus. In vivo stability assays using BALB/c mice, EU129 showed enhanced binding to the RBD and maintained enzymatic activity similar to ACE2 wild-type. We generated EU129 with the improved binding affinity and neutralizing activity through ACE2 receptor engineering. It has angiotensin II-converting enzymatic activity for organ protection, thus EU129 is a better therapeutic candidate for severe cases of SARS-CoV-2 infection and patients with underlying diseases such as cancers.

Citation Format: Byoung S. Kwon, Seunghyun Lee, Jin-Kyung Choi, Bora Hwang, Sun-Woo Im, Yun-Sook Lim, Bumseok Kim, Soon B. Hwang, HoonSung Jeh. Development of SARS-CoV-2 neutralizing protein by ACE2 receptor engineering for severe infection and patients with underlying diseases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB075.