AU2021251760A1 - De novo protein decoys of angiotensin-converting enzyme 2 (ACE2) - Google Patents
De novo protein decoys of angiotensin-converting enzyme 2 (ACE2) Download PDFInfo
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- AU2021251760A1 AU2021251760A1 AU2021251760A AU2021251760A AU2021251760A1 AU 2021251760 A1 AU2021251760 A1 AU 2021251760A1 AU 2021251760 A AU2021251760 A AU 2021251760A AU 2021251760 A AU2021251760 A AU 2021251760A AU 2021251760 A1 AU2021251760 A1 AU 2021251760A1
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Abstract
Provided herein are de novo protein decoys of ACE2 and uses thereof. In some embodiments, methods of treating coronavirus infection using the ACE2 protein decoys are provided.
Description
DE NOVO PROTEIN DECOYS OF ANGIOTENSIN-CONVERTING ENZYME 2 (ACE2) CROSS-REFERENCE TO RELATED APPLICATIONS [001] This application claims the benefit of priority of US Provisional Application No. 63/006,463, filed April 7, 2020; US Provisional Application No.63/028,401, filed May 21, 2020; US Provisional Application No.62/705,150, filed June 13, 2020; US Provisional Application No.63/055,051, filed July 22, 2020; US Provisional Application No. 63/060,489, filed August 3, 2020; US Provisional Application No.63/094,179, filed October 20, 2020; and US Provisional Application No.63/145,352, filed February 3, 2021; each of which is incorporated by reference herein in its entirety for any purpose. FIELD [002] The present invention is related to de novo protein decoys of ACE2. BACKGROUND [003] Viruses often exploit cell surface-associated proteins to enter and infect host cells. Neutralizing antibodies can inhibit this process by binding to the surface of the virus, impeding its interaction with the target cell’s surface protein(s) and/or preventing viral- associated conformational changes necessary for infection. Vaccination has, therefore, been a broadly useful tool to combat many viral diseases. RNA-based viruses are a frequent exception to this strategy. Neutralizing antibodies bind to viral proteins in a fundamentally different fashion than how the virus interacts with its cell target. Therefore, RNA viruses with high mutational rates often exploit such structural discrepancy to escape the immune system by remodeling the shape of their receptor-binding proteins to evade neutralizing antibodies while retaining the interaction with their target receptor(s). [004] Coronaviruses are large, enveloped, positive-stranded RNA viruses. The genome is packed inside a helical capsid formed by the nucleocapsid protein and is further surrounded by the viral envelope. At least three structural proteins are associated with the viral envelope, including the envelope-anchored spike protein. Coronaviruses recognize a variety of receptors, and binding by the spike protein mediates coronavirus entry into host cells via those receptors. Coronaviruses are believed to enter host cells via a two-step process. First, the spike protein binds to a receptor on the host cell surface through its S1 subunit and then fuses the viral and host membranes through its S2 subunit. Both the viral attachment step and membrane fusion process are mediated by recognition of the host receptor by the spike protein. The alphacoronavirus HCoV-NL63 and the betacoronavirus SARS-CoV both
recognize the receptor zinc peptidase angiotensin-converting enzyme 2 (ACE2). Recently, it has been discovered that ACE2 is also the functional receptor for 2019-nCov, a new SARS- like coronavirus that emerged from Wuhan, China in 2019, also referred to as SARS-CoV- 2. [005] SARS-CoV-2 is a highly contagious virus that causes coronavirus disease 2019 (COVID-19). Since its emergence in December 2019, SARS-CoV-2 has caused millions of cases of COVID19 and has become a global pandemic. While the majority of subjects are asymptomatic or have mild disease, a number of subjects will develop either severe disease with dyspnea or hypoxia or critical disease with symptoms of respiratory failure requiring positive pressure ventilation, shock, or multi-organ failure. A need exists for identifying agents that can prevent viruses, such as coronaviruses, from invading host cells. The present invention meets this and other needs. BRIEF DESCRIPTION OF THE DRAWINGS [006] Figure 1 – Figure 1 is a schematic showing inhibition of viral entry into cells by a de novo designed ACE2 protein decoy. SARS-CoV and SARS-CoV-2 viruses enter cells by first binding to the ACE2 receptor on the surface of human cells via the RBD domain of the spike protein (left). The de novo designed ACE2 decoy binds to the RBD domain in the same manner as natural ACE2 but, unlike ACE2, has no biological function. The decoys effectively sequester the virus from binding the native ACE2 receptors and prevent viral entry into cells while keeping native ACE2 function levels intact (right). [007] Figure 2A-F – Figure 2A-F demonstrate by yeast surface display that the de novo ACE2 protein decoy CTC-445 binds to SARS-CoV-2 Spike/RBD Protein. Figure 2A-B show a positive (ACE-2) control and Figure 2C-D show a negative control (human IL-21R). Figure 2E-F show CTC-445. [008] Figure 3A-D - Figure 3A-D demonstrate that control human ACE2 (3A-B) and de novo protein decoy CTC-445 (3C-D) bind to SARS-CoV-2 Spike/RBD Protein and compete with soluble ACE2 for binding to the Spike/RBD protein. [009] Figure 4 – Figure 4 shows the kinetics of binding of purified ACE2 protein decoy CTC-445 via an Octet biolayer interferometry (BLI) binding assay. [0010] Figure 5A-H – Figure 5A-H shows the kinetics of binding of select purified ACE2 protein decoys via Octet BLI binding assays. [0011] Figure 6A-H – Figure 6A-H shows the kinetics of binding of select purified ACE2 protein decoys via Octet BLI binding assays.
[0012] Figure 7A-H – Figure 7A-H shows the kinetics of binding of select purified ACE2 protein decoys CTC-445 variants via Octet BLI binding assays. [0013] Figure 8A-C – Circular dichroism absorption at 222 nm of ACE2 protein decoys CTC-445 (A), CTC-445.2 (B) and CTC-445.2d (C). The insets show far UV wavelength spectra of the test articles at 20 °C, after heating to 95-99 °C (dashed) and after cooling the heated sample to 20 °C. The Y axes for 8B and 8C is the same as that for 8A. [0014] Figure 9A-C – Figure 9A-C shows the thermal recovery of ACE2 protein decoys CTC-445, CTC-445.2 and CTC-445.2d after repeated cycles of heating and cooling. The data shows that the designed proteins refold even after repeated thermal denaturation. [0015] Figure 10A-C – Figure 10A-C show the kinetics of binding of purified ACE2 protein decoys CTC-445 (A), CTC 445.2 (B) and CTC-445.2d (C) via Octet BLI binding assays. [0016] Figure 11 – Figure 11 provides a plot of the potency of select ACE2 protein decoys vs their molecular weight. IC50 is measured by ELISA. [0017] Figure 12A-B – Figure 12A shows a neutralization assay performed using a non- replicative VSV pseudovirus carrying a luciferase reporter gene and expressing the spike protein of SARS-CoV-2 on its surface. Viral neutralization with ACE2 protein decoys CTC- 445.2 and CTC-445.2d was performed on HEK 293T cells overexpressing ACE2. The test proteins were pre-incubated with pseudovirus prior to incubation with cells. Samples were tested in duplicate utilizing 3-fold serial dilutions started at 20 μM (CTC-445.2) or 10 μM (CTC-445.2d). A cell viability assay (12B) was run in parallel. [0018] Figure 13 – Figure 13 shows bioavailability of ACE2 protein decoy CTC-445.2d in mice lung (top) and plasma (bottom) after intranasal administration. Protein concentration in lung lysates and blood plasma are quantified using Meso Scale Discovery platform. [0019] Figure 14 – Figure 14 shows ACE2 functional activity as measured by enzymatic release of a free fluorophore from Mca-APK(DNP) substrate. ACE2 inhibition was shown using DX600 peptide as a positive control. [0020] Figure 15A-B – Figure 15 shows the kinetics of binding of ACE2 protein decoys CTC-445.2 (A) and CTC-445.2d (B) to SARS-CoV-1 via Octet BLI binding assays. [0021] Figure 16A-E – Figure 16A-E show the shows the kinetics of binding of ACE2 protein decoy CTC-445.2 to SARS-CoV-2 RBD mutants via Octet binding assays. [0022] Figure 17 – Figure 17 provides the designed ACE2 protein decoy CTC-445 in complex with the SARS-CoV-2 spike protein RBD (surface representation). The graph on
the right on the cartoon representations shows biased forward folding simulations of designed sequence. The designed sequence was subjected to ab initio structure prediction using Rosetta. Each point in the plot represents an independent folding trajectory which was computed by Monte Carlo insertion of fragments from solved protein structures. Folding simulations were biased towards the designed conformation by using a small subset of fragments at each residue position with the lowest RMSD (9- and 3-mers) to the designed structure. Red (or black for B&W) dots are trajectories computed using the 5 fragments from Rosetta's vall structural database with lowest RMSD to the designs at each amino acid position. Brown (or gray) dots are trajectories computed using fragments from the design model itself plus the 8 lowest RMSD 3mers and 9mers. The funnel-shaped energy landscape suggests that the designed structure is the global energy minima and has a substantial energy gap with respect to alternative conformations. [0023] Figure 18A-B –Figure 18A-B shows a structural alignment of ACE2 protein decoy CTC-640 with a non-redundant database of known structures. Structural alignment was performed using MICAN in rewiring and reverse mode with maximum distance between C⍺ atoms to be aligned of 10.0 A. Each gray point represents the structural alignment of CTC- 640 with a different structure in the database. Each black point represents the structural alignment of CTC-640 with different structures of ACE2. For both plots, structural alignments of <50 total residues were discarded. A) Structural alignments are performed using TMalign, which aligns structures based on the order of the secondary structure elements in the polypeptide chain. Sequence identity is computed based on the structurally aligned residues. Although CTC-640 mimics the ACE2 binding surface, it does not align well in lineal structure or sequence to any protein in the database, including ACE2. B) Structural alignment is performed using MICAN in rewiring/reverse mode, which allows inverse direction of secondary structures, alternative alignments, and non-sequential alignments. The highest sequence identity observed for CTC-640 is with ACE2 where H1+H2+H3 correctly align to their counterparts in ACE2 with sequence identity of 33.7% for aligned residues. [0024] Figure 19A-C – Figure 19A-C shows the kinetics of binding of ACE2 protein decoy CTC-708 (CTC-445.2t) via Octet binding assays to SARS-CoV-2 (19A), SARS- CoV-1 (19B), and results of a competition assay [0025] Figure 20A-C – Figure 20A-C provides results from deep mutational scanning of ACE2 protein decoy CTC445.2 and plotted as sequence logo using logomaker [ref: https://www.biorxiv.org/content/10.1101/635029v1]. Letters are scaled according to their
probability and ordered from highest probability (top) to lowest (bottom). The native sequence of CTC445.2 is shaded in black. Residues 1-54 are shown in 20A, residues 55-107 are shown in 20B and residues 108-160 are shown in panel 20C. [0026] Figure 21A-C - Figure 21A shows neutralization of SARS-CoV-2 infection with ACE2 protein decoys CTC445.2d and CTC445.3d in engineered HEK293T cells overexpressing hACE2 determined using a non-replicative VSV pseudovirus carrying a luciferase reporter gene and expressing the spike protein of SARS-CoV-2 (GenBank: QHD43416.1) on its surface. Figure 21B shows a neutralization assay using control pseudovirus expressing VSVg instead of spike protein. Figure 21C shows cell viability of engineered HEK293T cells incubated with ACE2 protein decoys CTC-445.2d and CTC- 445.3d. SUMMARY [0027] The present inventors have built de novo proteins that can accurately recapitulate the natural binding surface targeted by some coronaviruses. In particular, the present inventors have built de novo proteins that present a binding surface recognized by coronaviruses, in particular, coronaviruses that use ACE2 to mediate entry into host cells. By binding to the coronavirus, these de novo proteins can act as decoys for host ACE2 protein and, in certain aspects, prevent the virus from binding to its receptor, ACE2. Accordingly, provided herein are, inter alia, de novo proteins, ACE2 protein decoys, that bind to the coronavirus spike protein of SARS-CoV and SARS-CoV-2. The proteins of the present invention are useful, inter alia, for inhibiting or neutralizing the activity of the virus. In some embodiments, the proteins are useful for blocking binding of the virus to its host cell receptor and for preventing the entry of the coronavirus into host cells. In some embodiments, the proteins function by inhibiting the cell-to-cell transmission of the virus. In certain embodiments, the proteins are useful in preventing, treating or ameliorating at least one symptom of coronavirus infection in a subject. In certain embodiments, the proteins may be administered prophylactically or therapeutically to a subject having or at risk of having coronavirus infection. [0028] In a first aspect, the present invention provides de novo proteins, ACE2 protein decoys, that bind specifically to coronavirus spike protein, in particular, spike protein from those coronaviruses that use ACE2 as their receptor to facilitate viral entry into target cells, for example, SARS-CoV and SARS-CoV-2. Also provided are de novo proteins, ACE2 protein decoys, that block (e.g., partially or fully) coronavirus spike protein binding to its
native receptor and, in particular, block coronavirus spike protein binding to ACE2. In some embodiments, the present invention provides de novo proteins, ACE2 protein decoys, that block the binding of coronavirus to its native human, camel or bat ACE2 receptor. [0029] The de novo proteins of the present invention are non-naturally occurring and are comprised of peptide domains, including at least two alpha helical domains, H1 and H2, and an optional beta hairpin domain, H3. These three domains interface with the coronavirus spike protein. Exemplary de novo proteins of the present invention further comprise at least one structural domain that facilitates protein folding and binding- competent presentation of the H1 and H2 alpha helices and H3 beta hairpin domains to the coronavirus spike protein. In some aspects, exemplary de novo proteins of the present invention comprise at least two structural domains that facilitate protein folding and binding-competent presentation of the H1 and H2 alpha helices and H3 beta hairpin domains to the coronavirus spike protein. The H1 and H2 alpha helical domains and optional beta hairpin comprise amino acid residues that interact with/act as binding sites to the coronavirus spike protein. [0030] The de novo proteins of the present invention interact with amino acid residues in the receptor binding domain of coronavirus spike protein. Without wishing to be bound by theory, for SARS-CoV, the expected binding residues on the RBD (receptor binding domain) are: 442, 443, 461, 462, 463, 470, 471, 472, 473, 475, 476, 479, 481, 482, 483, 486, 487, 488, 489 and 491 and for SARS-CoV-2, the expected binding residues are: 455, 456, 475, 476, 477, 486, 487, 489, 490, 493, 496, 497, 498, 500, 501, 502, 504, and 505. [0031] In a related aspect, the present invention provides not only the proteins comprising the peptide domains, H1, H2 and H3, but the peptide domains themselves. [0032] In a second aspect, the present invention provides nucleic acid molecules encoding the de novo proteins and peptide domains of the present invention. For example, the present invention provides nucleic acid molecules encoding any of the proteins and peptide domains described herein. [0033] In a related aspect, the present invention provides recombinant expression vectors capable of expressing the proteins of the present invention. For example, the present invention includes recombinant expression vectors comprising any of the nucleic acid molecules mentioned above. Also included within the scope of the present invention are host cells into which such vectors have been introduced, as well as methods of producing
the proteins by culturing the host cells under conditions permitting production of the proteins, and recovering the proteins so produced. [0034] In a third aspect, the invention provides a pharmaceutical composition comprising a therapeutically effective amount of a de novo ACE2 protein decoy of the present invention and a pharmaceutically acceptable carrier. In a related aspect, the invention features a composition which is a combination of a de novo protein of the present invention and a second therapeutic agent. In one embodiment, the second therapeutic agent is any agent that is advantageously combined with a de novo protein of the present invention. Exemplary agents include, without limitation, other agents that inhibit viral activity including infectivity of host cells. [0035] In a fourth aspect, the invention provides therapeutic methods for treating a disease or disorder associated with a coronavirus that uses ACE2 as its receptor to facilitate viral entry into target cells. The methods include, for example, treating a viral infection in a subject using de novo ACE2 protein decoy of the invention, wherein the therapeutic methods comprise administering a therapeutically effective amount of a pharmaceutical composition comprising the ACE2 protein decoy to the subject in need thereof. The disorder treated is any disease or condition which is improved, ameliorated, inhibited or prevented by inhibition of SARS-CoV or SARS-CoV-2 coronavirus activity or activity of any other coronavirus that gains access to its target cells using the ACE2 receptor. In certain embodiments, the present invention provides methods to prevent, treat or ameliorate at least one symptom of coronavirus infection, the method comprising administering a therapeutically effective amount of a protein of the present invention to a subject in need thereof. In some embodiments, the present invention provides methods to ameliorate or reduce the severity of at least one symptom or indication of coronavirus infection in a subject by administering a protein of the invention, wherein at least one symptom or indication is selected from the group consisting of: inflammation in the lung, alveolar damage, fever, cough, shortness of breath, diarrhea, heart failure, arrhythmias, multiple organ dysfunction, pneumonia, septic shock and/or death. In certain embodiments, the invention provides methods to decrease viral load in a subject, the methods comprising administering to the subject an effective amount of a ACE2 protein decoy of the invention that binds the coronavirus spike protein from SARS-CoV or SARS-CoV-2 or another coronavirus spike protein from a coronavirus that gains entry into its target cells by use of the ACE2 receptor and blocks binding of the spike protein to its host cell receptor. In some embodiments, the de novo protein may be administered prophylactically or therapeutically
to a subject having or at risk of having a coronavirus infection. The subjects at risk include, but are not limited to, an immunocompromised person, an elderly adult (more than 65 years of age), healthcare workers, adults or children in close contact with a person(s) with confirmed or suspected coronavirus infection, and people with underlying medical conditions such as pulmonary disease or infection, heart disease or diabetes. In certain embodiments, the de novo proteins of the present invention are administered in combination with a second therapeutic agent to a subject in need thereof. The second therapeutic agent may be, for example, selected from the group consisting of an anti-inflammatory drug (such as corticosteroids, and non-steroidal anti-inflammatory drugs), an anti-infective drug, or an anti-viral drug. In certain embodiments, the second therapeutic agent may be an agent that helps to counteract or reduce any possible side effect(s) associated with a de novo protein of the invention, if such side effect(s) should occur. For example, in some aspects, the second therapeutic is one to treat cytokine release syndrome (e.g., a cytokine storm). The de novo protein thereof may be administered, for example, subcutaneously, intravenously, intradermally, intraperitoneally, orally, or intramuscularly. In some aspects, the de novo proteins are inhaled. [0036] Also included in the present invention are methods for treating a viral infection in a subject using the nucleic acids of the invention. The methods comprise administering a therapeutically effective amount of a nucleic acid encoding an ACE2 protein decoy of the present invention to a subject in need thereof. [0037] The present invention also includes use of protein or nucleic acid of the invention in the manufacture of a medicament for the treatment of a disease or disorder that would benefit from the blockade of coronavirus binding and/or activity. [0038] In a fifth aspect, the invention provides methods for detecting coronavirus spike protein in a biological sample. The methods comprise the steps of contacting the biological sample with an ACE2 protein decoy of the present invention and detecting coronavirus spike protein in the biological sample. [0039] Other embodiments will become apparent from a review of the ensuing detailed description. DEFINITIONS [0040] The term “SARS-CoV” refers to the Severe Acute Respiratory Syndrome coronavirus that emerged in China in 2002. It binds via the viral spike protein to human host cell receptor ACE2. The term “SARS-CoV-S”, also called “S protein”, refers to the
spike protein of the SARS coronavirus (S1 and S2). The SARS-CoV spike protein mediates receptor recognition and membrane fusion. During viral infection, the S protein is cleaved into two subunits, S1 and S2. The receptor binding domain is found in the S1 subunit and it directly binds to the peptidase domain (PD) of ACE2. S2 is responsible for membrane fusion. When S1 binds to ACE2, S2 is cleaved by host proteases. This cleavage of S2 is believed to be critical for viral infection. An exemplary SARS-CoV-S protein is provided herein as SEQ ID NO:2. The signal peptide is amino acids 1-13, S1 spike protein is amino acids 14-667, and S2 spike protein is amino acids 668-1255. The term SARS-CoV-S and SARS-CoV spike protein includes protein variants of SARS-CoV spike protein isolated from different SARS-CoV isolates. SARS-CoV isolates include, for example, Isolate BJ01, Isolate BJ02, Isolate BJ03, Isolate BJ04, Isolate GZ50, Isolate CUHK-W1, Isolate HKU- 36871, Isolate GD01, Isolate GD03, Isolate Shanghai LY, Isolate Frankfurt 1, Isolate FRA, Isolate SZ23, Isolate SZ3, and Isoalte Tor2. [0041] The term “COVID-19” or “2019-nCov” or “SARS-CoV-2” refers to a new SARS- like coronavirus that emerged from Wuhan, China in 2019 and was labeled by the WHO as a pandemic on March 11, 2020. As with SARS-CoV, it binds via the viral spike protein to human host cell receptor ACE2. The term “SARS-CoV-2-S”, also called “S protein” refers to the spike protein of the SARS-CoV-2 coronavirus. An exemplary SARS-CoV-2 S protein is provided herein as SEQ ID NO:3. The term SARS-CoV-2-S and SARS-CoV-2 spike protein includes protein variants of SARS-CoV-2 spike protein isolated from different SARS-CoV-2 isolates. The term “coronavirus ACE2-binding spike protein” or “ACE2- binding spike protein” as used herein refers to a coronavirus spike protein that uses ACE2 to mediate its entry into host cells. [0042] “ACE2” refers to the angiotensin-converting enzyme 2 that acts as a receptor for select coronaviruses. The full length of the human ACE2 protein is provided herein as SEQ ID NO:1. The signal peptide is amino acid residues 1-17; the extracellular PD domain is amino acid residues 18-740; the transmembrane segment is residues 741-761; and the intracellular domain is residues 762-805. [0043] The primary physiological role of ACE2 is in the maturation of angiotensin, however, it has also been hijacked as a cellular receptor for some coronaviruses. The ACE2 protein decoys of the present invention were designed to act as decoys for human ACE2, nevertheless, in some embodiments, they can act as protein decoys for ACE2 from other mammalian species.
[0044] The term “coronavirus infection” or “SARS-CoV infection” or “SARS-CoV-2 infection”, as used herein, refers to infection by a coronavirus that use the ACE2 receptor to gain entry into host cells, and in particular, SARS or COVID-19 coronavirus. Severe acute respiratory illness is associated with both SARS and COVID-19 coronavirus infection. A wide range of additional complications are associated with COVID-19 coronavirus, including thrombotic events and neurological disease. Symptoms of infection include fever, cough, shortness of breath pneumonia, gastro-intestinal symptoms such as diarrhea, organ failure (kidney failure, heart failure, and renal dysfunction), septic shock and death in severe cases. [0045] The term “recombinant”, as used herein, refers to proteins of the invention created, expressed, isolated or obtained by technologies or methods known in the art as recombinant DNA technology which include, e.g., DNA splicing and transgenic expression. [0046] The term “specifically binds,” or “binds specifically to”, or the like, means that a first moiety has a greater affinity for a second moiety than it does for other moieties. Specific binding does not, however, require exclusive binding. In some embodiments, a first moiety specifically binds a second moiety and the resulting complex is relatively stable under physiologic conditions. Specific binding can be characterized, in some embodiments, by an equilibrium dissociation constant of about 650 nM or less, or in some embodiments, 100 nM or less (e.g., a smaller KD denotes a tighter binding). Methods for determining whether two moieties specifically bind are well known in the art and include, for example, equilibrium dialysis, surface plasmon resonance, and the like. As described herein, proteins have been identified which bind specifically to coronavirus spike protein, in particular, proteins that bind specifically to coronavirus ACE2-binding spike protein. [0047] The phrase “therapeutically effective amount” refers to an amount that produces the desired effect for which it is administered. The exact amount will depend on the purpose of the treatment and will be ascertainable by one skilled in the art using known techniques (see, for example, Lloyd (1999) The Art, Science and Technology of Pharmaceutical Compounding). [0048] As used herein, the term “subject” refers to an animal, preferably a mammal, more preferably a human, in need of amelioration, prevention and/or treatment of a disease or disorder such as viral infection. The term includes human subjects who have or are at risk of having a coronavirus infection.
[0049] As used herein, the terms “treat”, “treating”, or “treatment” refer to the reduction or amelioration of the severity of at least one symptom or indication of a coronavirus infection due to the administration of a therapeutic agent such as a protein of the present invention to a subject in need thereof. The terms include inhibition of progression of disease or of worsening of infection. The therapeutic agent may be administered at a therapeutic dose to the subject. [0050] The term “prevent”, “preventing” or “prevention” refers to inhibition of the onset of symptoms of a coronavirus infection. In some embodiments, prevention encompasses inhibition of a coronavirus infection and/or inhibition of the spread of coronavirus infection from a subject to another individual. [0051] As used herein, the term “anti-viral drug” refers to any anti-infective drug or therapy used to treat, prevent, or ameliorate a viral infection in a subject. The term “anti- viral drug” includes, but is not limited to ribavirin, remdesivir, oseltamivir, zanamivir, interferon-alpha2b, analgesics and corticosteroids. In the context of the present invention, the viral infections include infection caused by human coronaviruses, including SARS-CoV and SARS-CoV-2. [0052] The term “identity”, as used herein in reference to polypeptide sequences, refers to the amino acid sequence identity between two molecules. When an amino acid position in both molecules is occupied by the same amino acid, then the molecules are identical at that position. The identity between two polypeptides is a direct function of the number of identical positions. In general, the sequences are aligned so that the highest order match is obtained (including gaps if necessary). Identity can be calculated using published techniques and widely available computer programs, such as the GCG program package (Devereux et al., Nucleic Acids Res.12:387, 1984), BLASTP, FASTA (Atschul et al., J. Molecular Biol.215:403, 1990), etc. Sequence identity can be measured, for example, using sequence analysis software such as the Sequence Analysis Software Package of the Genetics Computer Group at the University of Wisconsin Biotechnology Center (1710 University Avenue, Madison, WI 53705), with the default parameters thereof. When determining identity for the present invention, it is also important to consider positioning of the binding interface residues with the coronavirus spike protein. If amino acids are added or deleted, it should be done in such a way that doesn’t substantially interfere with presentation of the protein to its binding partner or with secondary structure. Unless indicated otherwise, percent identity is determined across the length of the reference sequence.
[0053] In some aspects, amino acid substitutions relative to the reference peptide domains can be, for example, conservative amino acid substitutions. As used herein, “conservative amino acid substitution” means a given amino acid can be replaced by an amino acid having similar physiochemical characteristics, e.g., substituting one aliphatic residue for another (such as Ile, Val, Leu, or Ala for one another), or substitution of one polar residue for another (such as between Lys and Arg; Glu and Asp; or Gln and Asn). Other such conservative substitutions, e.g., substitutions of entire regions having similar hydrophobicity characteristics, are known. Polypeptides comprising conservative amino acid substitutions can be tested in any one of the assays described herein to confirm that a desired activity is retained. Amino acids can be grouped according to similarities in the properties of their side chains. Alternatively, naturally occurring residues can be divided into groups based on common side-chain properties. Non-conservative substitutions will entail exchanging a member of one of these classes for a member of another class. Particular conservative substitutions include, for example; Ala to Gly or Ser; Arg to Lys; Asn to Gln or H; Asp to Glu; Cys to Ser; Gln to Asn; Glu to Asp; Gly to Ala or Pro; His to Asn or Gln; Ile to Leu or Val; Leu to Ile or Val; Lys to Arg, Gln or Glu; Met to Leu, Tyr or Ile; Phe to Met, Leu or Tyr; Ser to Thr; Thr to Ser; Trp to Tyr; Tyr to Trp; and/or Phe to Val, Ile or Leu. A common hydrophobic grouping is glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), and phenylalanine (Phe). [0054] As used herein, the natural amino acid residues are abbreviated as follows: alanine (Ala; A), asparagine (Asn; N), aspartic acid (Asp; D), arginine (Arg; R), cysteine (Cys; C), glutamic acid (Glu; E), glutamine (Gln; Q), glycine (Gly; G), histidine (His; H), isoleucine (Ile; I), leucine (Leu; L), lysine (Lys; K), methionine (Met; M), phenylalanine (Phe; F), proline (Pro; P), serine (Ser; S), threonine (Thr; T), tryptophan (Trp; W), tyrosine (Tyr; Y), and valine (Val; V). As used herein “any amino acid” typically refers to the 20 natural amino acids. The skilled practitioner will appreciate, however, that one or more, (e.g., from 1 to 10, 1 to 5, 1 to 3, or 1 or 2) unnatural amino acids can be used in place of a natural amino acid. As used herein, the term “unnatural amino acid” refers to an amino acid other than the 20 amino acids that occur naturally in protein. Unnatural amino acids are known in the art. [0055] As used herein, the terms "polypeptide”, “protein” or “peptide” refer to any chain of amino acid residues, regardless of its length or post-translational modification (e.g., glycosylation or phosphorylation).
[0056] “Operably linked” is intended to mean that the nucleotide sequence of is linked to the regulatory sequence(s) in a manner that allows for expression of the nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell). “Regulatory sequences” include promoters, enhancers, and other expression control elements (e.g., polyadenylation signals). The expression constructs of the invention can be introduced into host cells to thereby produce the proteins disclosed herein. [0057] The terms “host cell” and “recombinant host cell” are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but also to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell but are still included within the scope of the term as used herein. [0058] As used herein, the terms “transformation” and “transfection” refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, particle gun, or electroporation. [0059] As used herein, the term “pharmaceutically acceptable carrier” includes, but is not limited to, saline, solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. Supplementary active compounds (e.g., antibiotics) can also be incorporated into the compositions. GENERAL [0060] The inventors have described herein de novo ACE2 protein decoys that specifically bind to the spike protein on coronaviruses and modulate the interaction of the spike proteins with their innate receptor. In particular, the de novo ACE2 protein decoys bind to the spike protein on those coronaviruses that use ACE2 as their receptor to facilitate viral entry into target cells. Notably, although the de novo ACE2 protein decoys of the present invention contain the domains necessary for interacting with and binding to coronavirus spike protein, they typically do not contain domains associated with other enzymatic activities of native ACE2, including for example the catalytic domain (e.g., metalloprotease catalytic domain) of ACE2. Exemplary de novo ACE2 protein decoys of the present invention do not catalyze the cleavage of angiotensin (i.e., any forms of angiotensin, including angiotensin I and II).
In some embodiments, the ACE2 protein decoys provided herein have no more than 60%, 55%, 50%, 45%, 40%, or 35% sequence identity to human ACE2 (SEQ ID NO: 1). With regard to identity to ACE2, percent identity is calculated with the ACE2 protein decoy as query and ACE2 as reference, over the length of the query. [0061] In some embodiments, protein decoys of the present invention bind to the spike protein (e.g., spike protein from SARS-CoV-2) with a Kd of 700 nM or less, Kd of 600 nM or less, Kd of 500 nM or less, Kd of 400 nM or less, Kd of 300 nM or less, Kd of 200 nM or less, Kd of 100 nM or less, Kd of 50 nM or less, preferably about 20 nM or less, or even 15 nM, 10 nM, or 5 nM or less. Methods of determining Kd are known in the art and described in the examples. In certain embodiments, the de novo protein decoys of the present invention are blocking proteins in that they may bind to the coronavirus spike protein (e.g., from SARS-CoV-2) and block the interaction of the spike protein with their native receptor (i.e., ACE2). As used herein, blocking proteins may completely block the interaction of the spike protein with their native receptor or may partially block the interaction of the spike protein with their native receptor. In certain embodiments, the de novo protein decoys inhibit the interaction of the spike protein with their native receptor (i.e., ACE2) with an IC50 of 100 nM or less. In some embodiments, the de novo proteins inhibit the interaction of the spike protein with their native receptor (i.e., ACE2) with an IC50 of 50, 40, 30, 20, 10, or 5 nM or less. In some embodiments, the blocking proteins of the invention block the binding of the coronavirus spike protein to its receptor and/or inhibit or neutralize or reduce viral infectivity of host cells. In some embodiments, the blocking proteins may be useful for treating a subject suffering from a coronavirus infection (e.g., COVID-19 coronavirus infection). In some embodiments, The de novo protein decoys of the present invention, when administered to a subject in need thereof, reduce the infection by a coronavirus such as SARS-CoV-2 in the subject. They may be used to decrease viral loads in a subject. Protein decoys of the present invention may be used alone or as adjunct therapy with other therapeutic moieties or modalities known in the art for treating viral infection. The ability of the de novo proteins of the invention to bind to and inhibit/neutralize the activity of SARS-CoV or SARS-CoV-2 may be measured using any standard method known to those skilled in the art, including binding assays, or activity assays, as described herein. For example, in vitro assays for measuring binding and inhibition and/or blocking activity are illustrated in examples. [0062] The de novo protein decoys of the present invention may contain no additional labels or moieties, or they may contain labels (e.g., an N-terminal or C-terminal label or
moiety). In one embodiment, the label or moiety is biotin. In a binding assay, the location of a label (if any) may determine the orientation of the peptide relative to the surface upon which the peptide is bound. For example, if a surface is coated with avidin, a peptide containing an N-terminal biotin will be oriented such that the C-terminal portion of the peptide will be distal to the surface. The label may be, for example, an enzyme, a radionuclide, a fluorescent dye or a MRI-detectable label. Such labeled proteins may be used in diagnostic assays including imaging assays. In some aspects, for ACE-2 protein decoys that do not contain tryptophan, the label may be a C-terminal peptide that allows for detection of protein by absorbance at 280 nm (e.g., GSGWGSG, SEQ ID NO:248). STRUCTURAL AND SEQUENCE CHARACTERISTICS OF THE ACE2 PROTEIN DECOYS [0063] Provided herein are de novo proteins of the present invention, referred to herein as ACE2 protein decoys. These protein decoys are, by nature, non-naturally occurring proteins, and comprise at least two alpha helical domains that interface with the coronavirus spike protein and preferably at least one structural domain that facilitates protein folding and binding-competent presentation of the alpha helices. In some embodiments, the de novo proteins further comprise an optional beta hairpin domain. The alpha helical domains that interface with the coronavirus spike protein and optional beta-hairpin domain interact with/act as binding sites to the coronavirus spike protein. These domains, referred to herein as H1, H2, and H3, comprise both amino acid residues that engage in binding interactions with the coronavirus spike protein and amino acid residues that do not engage in binding interactions with the coronavirus spike protein. Generally, with respect to the H1 and H2 domains, those amino acid residues that do not engage in binding interactions with the coronavirus ACE2- binding spike protein are at positions that can be very promiscuous with respect to the identity of the amino acid that sits at that position. A number of these residues are also at solvent exposed positions. In some embodiments, when replacing amino acids at solvent exposed positions, the use of hydrophilic amino acids are particularly desirable, although non-hydrophilic amino acids are acceptable as well. [0064] The skilled artisan will appreciate that the de novo proteins of the present invention, the ACE2 protein decoys, were designed such that the binding domains align structurally to the corresponding binding sites in the native ACE2 protein whereas the supporting structural domains do not structurally or sequentially align to any other secondary structures in ACE2. In some aspect, the de novo proteins of the present invention
structurally align to the native ACE2 binding motifs within, for example, 2.75 A RMSD (root mean square deviation) and contain one or more secondary structure elements that do not structurally or sequentially align to any other secondary structure elements in ACE2. Methods of determining RMSD are known in the art, for example using the MICAN protein structure alignment algorithm. MICAN identifies the best structural alignment between protein pairs by disregarding the connectivity between secondary structure elements. [0065] In some aspects, the de novo proteins of the present invention comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); H2 comprises the amino acid sequence NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5); and H3, if present, comprises the amino acid sequence X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6), wherein X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, X27, X28, X29, X30, X31, X32, X33, X34, X35, and X36, are each independently selected from any amino acid. [0066] Such de novo proteins further comprise one or more structural domain that facilitates protein folding and binding-competent presentation of H1, H2, and H3. In some embodiments of the present invention, the coronavirus-binding amino acid residues of the ACE2 protein decoys are the same as the coronavirus binding amino acid residues of the ACE2 protein. For example, in some such embodiments, the binding residues of H1, H2 and H3 are identical to the amino acid at the same structural position in the native ACE2 protein. In addition, in some exemplary embodiments, all, or all but one to six, or one to five, or one to four, or one to three of the solvent exposed amino acids of H1 and all, or all but one to six, or one to five, or one to four, or one to three of the solvent exposed amino acids of H2, whether or not they are involved in binding, are the same as the amino acids at the same structural position in the native ACE2 protein. By presenting a virtually identical surface as the one that the virus targets in the protein ACE2, the ability of the virus to mutate to avoid binding to the ACE2 protein decoys of the present invention is minimized. In SEQ ID NO:4, the amino acid residues at positions 1, 5, 6, 9, 10, 12, 13, 16, 17, 19, 20, 23, 24 and 27 are, for the most part, solvent exposed and/or involved in binding to
coronavirus ACE2-binding spike protein; in SEQ ID NO: 176, the amino acid residues at positions 3, 4, 7, 8, 10, 11, 14, 15, 17, 18, 21, 22 and 25 are, for the most part, solvent exposed and/or involved in binding to coronavirus ACE2-binding spike protein; in SEQ ID NO:5, the amino acid residues at positions 1, 4, 8, 12, 15, 16, 19, 22 and 23 are, for the most part, solvent exposed and/or involved in binding to coronavirus ACE2-binding spike protein; and in SEQ ID NO:6 the amino acid residues at positions 7, 8, and 9 are, for the most part, solvent exposed and/or involved in binding to coronavirus ACE2-binding spike protein. In some aspects, when making amino acid substitutions, these residues are not substituted. In other aspects, it may be desirable to modify these residues. For example, modifications to these residues can be made in order to create a protein that binds to ACE2 with a higher affinity than native coronavirus spike protein. Such a protein can be used, for example, for diagnostic purposes. In some aspects, no more than 4, no more than 3, no more than 2 or no more than 1 of the residues at positions 1, 5, 6, 9, 10, 12, 13, 16, 17, 19, 20, 23, 24 and 27 of SEQ ID NO:4 are substituted or no more than 4, no more than 3, no more than 2 or no more than 1 of the residues at positions 3, 4, 7, 8, 10, 11, 14, 15, 17, 18, 21, 22 and 25 of SEQ ID NO:176 are substituted; no more than 3, no more than 2 or no more than 1 of the residues at positions 1, 4, 8, 12, 15, 16, 19, 22 and 23 of SEQ ID NO:5, are substituted; and no more than 1 of the residues of 7, 8, 9 or 11 in SEQ ID NO:6 is substituted or no more than 1 of the residues of 7, 8, or 9 in SEQ ID NO:6 is substituted. In some such aspects, such substitutions are with amino acids selected from D, E, G, K, N, P, Q, R, S, or T. In some such aspects, substitutions are with conservative amino acids. In other aspects, one or more of the following substitutions are made in SEQ ID NO: 4: S1I; E5D; E5Q; E5V; D12V, D12E; Q24K; and Q24L. In other aspects, one or more of the following substitutions are made in SEQ ID NO: 176: E3D; E3Q; E3V; D10V, D10E; Q22K; and Q22L. With some exceptions, the residues identified in SEQ ID NOs: 4, 176, 5, and 6 as X (with a subscript numeral) are not solvent exposed and/or are not directly involved in binding to coronavirus ACE2-binding spike protein. These residues typically may be different from the corresponding amino acids in ACE2. Included in the present invention are those proteins wherein not more than half of, or no more than 8 of, the amino acids represented as X (with a subscript numeral) are the same amino acid as the corresponding position in native ACE2 represented by SEQ ID NO:1. In some aspects, not more than 4, 3 or 2, of the amino acids represented as X (with a subscript numeral) in H1; not more than 4, 3 or 2, of the amino acids represented as X (with a subscript numeral) in H2; and/or not more than 5, 4, 3 or 2, of the amino acids represented as X (with a subscript numeral) in
H3, are the same as the corresponding position in native ACE2. An exemplary corresponding sequence of H1 in ACE2 is ST IEEQAKTFLD KFNHEAEDLF YQSSL (SEQ ID NO:7); an exemplary corresponding sequence of H2 in ACE2 is NMNNAGDKWS AFLKEQSTLA QMY (SEQ ID NO:8); an exemplary corresponding sequence of H3 in ACE2 is TAWD LGKGDFRIL (SEQ ID NO:9). ALPHA HELICAL DOMAIN H1 [0067] The de novo proteins of the present invention (i.e., ACE2 protein decoys) can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein: H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13 are each independently selected from any amino acid. [0068] Included in the present invention are de novo proteins of the present invention wherein H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, E, F, G, I, L, M, N, Q, R, S, T, V, or Y); X2 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably V, A, D, H, I, N, P, T, or W); X3, is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably R, L,C, H, I, K, M, S, T, or Y); X4 is an amino acid selected from C, I, L, M, T, or V ( preferably L, I, T, or V); X5, is an amino acid selected from A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, K, C, E, I, L, N, R, V, or Y); X6 is an amino acid selected from A, C, G, L, M, S, T, or V (preferably A, C, S, or T); X7 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, or V (preferably A, C, E, F, I, L, N, Q, S, T, or V);
X8 is an amino acid selected from A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y (preferably F, D, E, H, L, M, N, Q, or W); X9 is an amino acid selected from A, C, D, F, G, H, I, L, M, N, Q, S, T, V, W, or Y (preferably M, A, C, F, G, L, S, T, or V); X10 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably R, A, C, E, F, G, H, I, M, P, Q, T, V, W, or Y); X11, is an amino acid selected from N, C, F, G, H, L, M, W, or Y (preferably F, N, W, or Y); X12 is an amino acid selected from A, C, F, G, H, I, L, M, N, Q, S, T, V, W, or Y (preferably A, C, S, or T); and X13 is an amino acid selected from A, C, D, E, F, G, H, I, L, M, N, Q, S, T, or V (preferably A, C, F, G, L, M, N, S, T, or V). [0069] Included in the present invention are de novo proteins of the present invention wherein H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X2,X6,X9,X11,X12,and X13, are each independently an amino acid selected from A, F, I, L, M, P or V; X5,X7,X8, and X10 are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X3 is an amino acid selected from A, C, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y or is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X4 is an amino acid selected from A, F, I, L, M, P, V, D, E, G, K, N, P, Q, R, S, or T. De novo ACE2 protein decoys of the present invention include those above wherein phenylalanine is included in the list of amino acids for X1, asparagine is included in the list of amino acids for X2, histidine is included in the list of amino acids for X8, and asparagineis included in the list of amino acids for X11. De novo ACE2 protein decoys of the present invention include those above wherein phenylalanine is included in the list of
amino acids for X1, asparagine is included in the list of amino acids for X2, asparagine is removed from the list of amino acid substitutions for X3, X4 is an amino acid selected from I, L, M, P, V, or T; aspartic acid is removed from the list of amino acid substitutions for X5, X6 is an amino acid selected from A, L, M, or V; proline is removed from the list of amino acid substitutions for X7, histidine is included in the list of amino acids for X8 and lysine and proline are removed, proline is removed from the list of amino acids for X9, asparagine is included in the list of amino acids for X11 and alanine, isoleucine, proline and valine are removed, and proline is removed from the list of amino acid substitutions for X12 and X13. [0070] Included in the present invention are de novo ACE2 protein decoys of the present invention wherein (i) X4 is an amino acid selected from A, F, I, L, M, P or V (preferably I, L, M or V); and X1, X2, X3, X5, X6, X7, X8, X9, X10, X11, X12, and X13 are as described in any of the embodiments provided herein; (ii) X4 is an amino acid selected from A, F, I, L, M, P or V (preferably I, L, M or V); and X5 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T (preferably E, G, K, N, P, Q, R, S, or T); and X1, X2 ,X3, X6, X7, X8,X9, X10,X11,X12, and X13 are as described in any of the embodiments provided herein; (iii) X1 is an amino acid selected from R or S or F; and X2,X3, X4, X5, X6, X7, X8,X9, X10,X11, X12, and X13 are as described in any of the embodiments provided herein; (iv) X3 is an amino acid selected from R, L, A, F, I, M, P, or V; and X1, X2, X4, X5, X6, X7, X8, X9, X10, X11, X12, and X13 are as described in any of the embodiments provided herein; (v) X3 is an amino acid selected from R, L, C, or S,; and X1, X2, X4, X5, X6, X7, X8, X9, X10, X11, X12, and X13 are as described in any of the embodiments provided herein; (vi) X7 is an amino acid selected from A or T; and X1,X2,X3, X4, X5, X6, X8,X9, X10, X11, X12, and X13 are as described in any of the embodiments provided herein; (vii) X10 is an amino acid selected from R, S or L or an amino acid selected from R or S; and X1,X2,X3, X4, X5, X6, X7, X8,X9,X11, X12, and X13 are as described in any of the embodiments provided herein; (viii) X1 is an amino acid selected from R or S or F; X3 is an amino acid selected from R or L; X7 is an amino acid selected from A or T; and X10 is an amino acid
selected from R, S or L; and X2, X4, X5, X6, X8, X9, X11, X12, and X13 are as described in any of the embodiments provided herein; (ix) X5 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T (preferably E, G, K, N, P, Q, R, S, or T); and X1,X2,X3, X4, X6, X7, X8,X9, X10,X11, X12, and X13 are as described in any of the embodiments provided herein; (x) X5 is lysine; and X1,X2,X3, X4, X6, X7, X8,X9, X10,X11, X12, and X13 are as described in any of the embodiments provided herein; (xi) X9 is an amino acid selected from M or L; and X1, X2, X3, X4, X5, X6, X7, X8, X10, X11, X12, and X13 are as described in any of the embodiments provided herein; (xii) X1 is serine; X3 is L; and X2, X4, X5, X6, X7, X8, X9, X10, X11, X12, and X13 are as described herein in any of the embodiments provided herein; or (xiii) X8 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, W, or Y (preferably A, D, E, F, G, I, L, M, N, Q, R, S, T, W, or Y) or X8 is an amino acid selected from F, D, E, G, K, N, P, Q, R, S, or T (preferably F, D, E, G, N, Q, R, S, or T) or X8 is phenylalanine or X8 is phenylalanine or histidine ; and X1,X2,X3, X4, X5, X6, X7, X9, X10, X11, X12, and X13 are as described in any of the embodiments provided herein. [0071] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein: H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 and X5 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X2,X4, X6,X9,X11,X12,and X13, are each independently an amino acid selected from A, F, I, L, M, P or V; X3,X7, and X10,are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X8 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, W, or Y (more preferably from F, D, E, G, K, N, P, Q, R, S, or T). De novo proteins of the present invention include those above wherein phenylalanine is included in the list of amino
acids for X1, asparagine is included in the list of amino acids for X2, histidine is included in the list of amino acids for X8, and asparagine is included in the list of amino acids for X11. De novo proteins of the present invention include those above wherein phenylalanine is included in the list of amino acids for X1, asparagine is included in the list of amino acids for X2, asparagine is removed from the list of amino acid substititions for X3, X4 is an amino acid selected from I, L, M, P, or V; asparatic acid is removed from the list of amino acid substitions for X5, X6 is an amino acid selected from A, L, M, or V; proline is removed from the list of amino acid substitions for X7, histidine is included in the list of amino acids for X8 and lysine and proline are removed; proline is removed from the list of amino acids for X9, asparagine is included in the list of amino acids for X11 and alanine, isoleucine, proline and valine are removed, and proline is removed from the list of amino acid substitions for X12 and X13. [0072] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 is an amino acid selected from R or S; X3 is an amino acid selected from R or L; X7 is an amino acid selected from A or T; X10 is an amino acid selected from R or S or L (preferably R or S); X2, X4, X6, X9, X11, X12, and X13, are each independently an amino acid selected from A, F, I, L, M, P or V; X5 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; and X8 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, W, or Y ( preferably from F, D, E, G, K, N, P, Q, R, S, or T). De novo proteins of the present invention include those above wherein phenylalanine is included in the list of amino acids for X1, asparagine is included in the list of amino acids for X2, histidine is included in the list of amino acids for X8, and asparagine is included in the list of amino acids for X11. De novo proteins of the present invention include those above wherein phenylalanine is included in the list of amino acids for X1, asparagine is included in the list of amino acids
for X2, asparagine is removed from the list of amino acid substititions for X3, X4 is an amino acid selected from I, L, M, P, or V; asparatic acid is removed from the list of amino acid substitions for X5, X6 is an amino acid selected from A, L, M, or V; proline is removed from the list of amino acid substitions for X7, histidine is included in the list of amino acids for X8 and lysine and proline are removed; proline is removed from the list of amino acids for X9, asparagine is included in the list of amino acids for X11 and alanine,isoleucine, proline and valine are removed, and proline is removed from the list of amino acid substitions for X12 and X13. [0073] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 is an amino acid selected from R or S; X2 is V; X3 is an amino acid selected from R or L; X4 is leucine; X5 is lysine; X6 is alanine; X7 is an amino acid selected from A or T; X8 is phenylalanine; X9 is methionine; X10 is an amino acid selected from R or S or L (preferably R or S); X11 is phenylalanine; X12 is A; and X13 is A. [0074] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein: X1 is an amino acid selected from R or S; X2 is valine; X3 is an amino acid selected from R or L or C or S; X4 is leucine; X5 is lysine; X6 is alanine; X7 is an amino acid selected from A or T; X8 is phenylalanine; X9 is M or L; X10 is an amino acid selected from R or S or L (preferably R or S); X11 is phenylalanine; X12 is alanine; and X13 is alanine. [0075] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein:
X1 is an amino acid selected from R or S or F; X2 is an amino acid selected from N or V; X3 is an amino acid selected from R or L or C or S; X4 is leucine; X5 is lysine; X6 is alanine; X7 is an amino acid selected from A or T; X8 is an amino acid selected from F or H; X9 is an amino acid selected from M or L; X10 is an amino acid selected from R or S or L (preferably R or S); X11 is an amino acid selected from F or N; X12 is alanine; and X13 is alanine. [0076] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein: H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein (i) X8 is not valine or (ii) X8 is not an an amino acid selected from V, A, I, L, M, or P or (iii) X8 is phenylalanine; and X1, X2, X3, X4, X5, X6, X7, X9, X10, X11, X12, and X13 are as described herein in any of the embodiments provided herein. [0077] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L X37X38X39X40X41X42 X43X44X45X46 (SEQ ID NO:10); wherein X1- X13 are as provided in the any of the embodiments herein for H1; and X37,X38, X41, X42, X45, and X46 are each independently selected from any amino acid. In some aspects, X1- X13 are as provided in the any of the embodiments herein for H1; and X37, X38, X41, X42, X45, and X46 are each independently an amino acid selected from A, F, I, L, M, P or V; X40 and X44 are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X39 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, I, L, M, P or V); X43 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T. De novo proteins of the present invention include those above wherein isoleucine is removed from the list of amino acids for X37, proline is removed from the list of amino acids for X38; X39 is an amino acid selected from F, I, L, M, V, W, or Y; histidine is included in the list of amino
acids for X40 and proline is removed, proline is removed from the list of amino acids for X41; and the amino acids, T and Y are included in the list of amino acids for X42. In some such aspects X42 is an amino acid selected from A or V. [0078] Also included in the present invention are those ACE2 protein decoys wherein X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13 are as described in any of the embodiments herein and one or more (preferably not more than 1 to 3) of the amino acids at positions 1, 5, 6, 9, 10, 12, 13, 16, 17, 19, 20, 23, 24 and 27 of SEQ ID NO:4 are substituted (or the equivalent positions in SEQ ID NO:176). For example, in some aspects, one or more of the following substitutions are made: S1I; E5D; E5Q; E5V; D12V, D12E; Q24L; and Q24K. In some aspects, one of the following substitutions is made in SEQ ID NO:4: S1I; E5D; E5Q; E5V; D12V, D12E; Q24L; and Q24K (or the equivalent positions in SEQ ID NO:176). In some aspects, one or more of the following substitutions are made in SEQ ID NO:4: T9F, D12I, D12N, E17I, Y23H or the equivalent positions in SEQ ID NO:176). [0079] In some embodiments, de novo proteins of the present invention include those described herein provided that X4 is not an amino acid selected from D, E, G, H, K, N, P, Q, R, S, W, or Y; X6 is not an amino acid selected from D, E, F, H, K, P, Q, R, W, or Y; X7 is not P; X8 is not proline; X9 is not an amino acid selected from K, P, or R; X11 is not an amino acid selected from D E, K, P, R, T or V; X12 is not an amino acid selected from K, P, or R; X13 is not an amino acid selected from P or W; X38 is not an amino acid selected from H, K, P, or R;X39 is not an amino acid selected from D, E, G, K, or P; and/or X41 is not proline. [0080] ACE2 protein decoys of the present invention include those wherein H1 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:11-17, 177-183, 198, or 199: SRVLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:11) SSVREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:12)ƒ44 SRVREQLKTFADKTFHEMEDRFYQAAL (SEQ ID NO:13) SRVREQLKTFADKAFHEMEDSFYQAAL (SEQ ID NO:14) SSVLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:15) SSVLEQLKTFADKTFHEMEDSFYQAAL (SEQ ID NO:16) SRVREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:17) VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:177) VREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:178)
VREQLKTFADKTFHEMEDRFYQAAL (SEQ ID NO:179) VREQLKTFADKAFHEMEDSFYQAAL (SEQ ID NO:180) VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:181) VLEQLKTFADKTFHEMEDSFYQAAL (SEQ ID NO:182) VREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:183) SSVLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:198) VLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:199). [0081] ACE2 protein decoys of the present invention include those wherein H1 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:15 (SSVLEQLKTFADKAFHEMEDRFYQAAL) (SEQ ID NO:15) wherein the amino acid at position 1 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; wherein the amino acid at position 2 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; wherein the amino acid at position 3 is V or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; wherein the amino acid at position 4 is L or if substituted is A, C, D, E, F, G, H, I, K, M, P, Q, R, S, T, V, W, or Y wherein the amino acid at position 5 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y wherein the amino acid at position 6 is Q or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, S, T, V, or W; wherein the amino acid at position 7 is L or if substituted is C, I, M, T, or V; wherein the amino acid at position 8 is K or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 9 is T or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, V, W, or Y; wherein the amino acid at position 10 is F or if substituted is A, C, H, V, W, or Y; wherein the amino acid at position 11 is A or if substituted is C, G, L, M, S, T, or V; wherein the amino acid at position 12 is D or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y;
wherein the amino acid at position 13 is K or if substituted is A, C, F, H, I, L, M, N, Q, R, S, V, W, or Y; wherein the amino acid at position 14 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, S, T, or V; wherein the amino acid at position 15 is F or if substituted is A, C, D, E, G, H, I, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 16 is H or if substituted is A, C, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 17 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 18 is M or if substituted is A, C, D, F, G, H, I, L, N, Q, S, T, V, W, or Y; wherein the amino acid at position 19 is E or if substituted is D, M, N, P, Q, T, or V; wherein the amino acid at position 20 is D or if substituted is E, F, G, H, L, N, or Q; wherein the amino acid at position 21 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y; wherein the amino acid at position 22 is F or if substituted is C, G, H, L, M, N, W, or Y; wherein the amino acid at position 23 is Y or if substituted is H, D, or F; wherein the amino acid at position 24 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y; wherein the amino acid at position 25 is A or if substituted is C, F, G, H, I, L, M, N, Q, S, T, V, W, or Y; wherein the amino acid at position 26 is A or if substituted is C, D, E, F, G, H, I, L, M, N, Q, S, T, or V; and wherein the amino acid at position 27 is L or if substituted is A, C, D, E, F, G, H, I, K, M, N, Q, R, S, T, V, W, or Y. Also included are those ACE-2 protein decoys wherein the amino acids at positions 1 and 2 are absent. In some particulary preferred embodiments, no more 3, 2, or 1 of the amino acids at positions 1, 5, 6, 9, 10, 12, 13, 16, 17, 19, 20, 23, 24 and 27 are substituted. [0082] In some aspects, H1 comprises additional amino acids at the C terminuts (e.g., an additional 11 amino acids at the C terminus). In any of the embodiments for H1 herein (including H1 having an amino acid sequence having at least 70%, 80%, 90%, 95% or
100% identity to an amino acid sequence set forth in SEQ ID NO:11-17, 177-183, 198, or 199), the amino acid sequence AVFEAAEAAAG (SEQ ID NO:18), AVWEAAEAAAG (SEQ ID NO:19), AVFEAVEAAAG (SEQ ID NO:249) or AVWEAVEAAAG (SEQ ID NO:250) can be optionally present at the C terminus. [0083] Accordingly, in some aspects, H1 comprises a sequence having at least 70%, 80%, 90%, 95% or 100% identity to the sequence set forth in SEQ ID NOS.240-243 or 251-254: SSVLEQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:240), VLEQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:241); SSVLEQLKTFADKAFHEMEDLFYQAALAVFEAAEAAAG (SEQ ID NO:242); VLEQLKTFADKAFHEMEDLFYQAALAVFEAAEAAAG (SEQ ID NO:243); SSVLEQLKTFADKAFHEMEDRFYQAALAVFEAVEAAAG (SEQ ID NO:251), VLEQLKTFADKAFHEMEDRFYQAALAVFEAVEAAAG (SEQ ID NO:252); SSVLEQLKTFADKAFHEMEDLFYQAALAVFEAVEAAAG (SEQ ID NO:253); or VLEQLKTFADKAFHEMEDLFYQAALAVFEAVEAAAG (SEQ ID NO:254). ALPHA HELICAL DOMAIN H2 [0084] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, X27 are each independently selected from any amino acid. [0085] Included in the present invention are de novo proteins of the present invention wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X14 is an amino acid selected from A, C, D, G, H, I, L, M, N, P, R, S, T, V, or W (preferably A, C, G, P, T, or V); wherein X15 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, I, K, L, M, N, Q, R, S, T, or V); wherein X16 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, E, H, I, L, M, N, Q, R, S, V, W, or Y); wherein X17 is an amino acid selected from A, C, D, E, G, I, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, G, I, or S);
wherein X18 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably A, C, F, G, H, I, K, L, M, N, Q, R, S, T, V, or Y); wherein X19 is an amino acid selected from from A, C, D, G, I, L, Q, S, T, V, or W (preferably A, L, T, or V); wherein X20 is an amino acid selected from from A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, K, Q, R, S, T, V, W, or Y); wherein X21 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, E, F, G, H, I, K, L, M, N, R, S, T, V, or W); wherein X22 is an amino acid selected from A, C, D, F, G, I, L, M, N, S, T, V, W, or Y (preferably A, C, F, G, I, L, S, or T); wherein X23 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, H, I, L, M, N, R, S, T, V, or Y); wherein X24 is an amino acid selected from A, C, E, F, G, I, L, M, Q, S, T, V, or W (preferably A, I, or S) wherein X25 is an amino acid selected from A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably K, D, G, H, I, Q, or R); wherein X26 is an amino acid selected from A, C, F, G, I, L, S, T, V, or Y (preferably A, or I); wherein X27 is an amino acid selected from A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y (preferably D, C, F, I, S, or T). [0086] Included in the present invention are de novo proteins of the present invention wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X16, X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y. De novo proteins include those above wherein phenylalanine is removed from the list of amino acids for X14 and X17, tyrosine is included in the list of amino acids for X18, glutamic acid and proline are removed from the list of amino acids for X19, proline is removed from the list of amino acids for X20, X22, X23, X24 and X25, methionine is
included in the list of amino acids for X21, histidine is included in the list of amino acids for X23,methionine and proline are removed from the list of amino acids for X26, and isoleucine is included in the list of amino acids for X27 and lysine and proline are removed. [0087] Included in the present invention are de novo proteins of the present invention wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X17, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; X16 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X19 is an amino acid selected from A, F, I, L, M, P, E, T, or V; and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y. De novo proteins include those above wherein phenylalanine is removed from the list of amino acids for X14 and X17, tyrosine is included in the list of amino acids for X18, glutamic acid and proline are removed from the list of amino acids for X19, proline is removed from the list of amino acids for X20, X22, X23, X24 and X25, methionine is included in the list of amino acids for X21, histidine is included in the list of amino acids for X23,methionine and proline are removed from the list of amino acids for X26, and isoleucine is included in the list of amino acids for X27 and lysine and proline are removed. [0088] Included in the present invention are de novo proteins of the present invention wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; X16 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably from A, F, I, L, M, P, E, or V), and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y. De novo proteins include those above wherein phenylalanine is removed from the list of
amino acids for X14 and X17, tyrosine is included in the list of amino acids for X18, glutamic acid and proline are removed from the list of amino acids for X19, proline is removed from the list of amino acids for X20, X22, X23, X24 and X25, methionine is included in the list of amino acids for X21, histidine is included in the list of amino acids for X23,methionine and proline are removed from the list of amino acids for X26, and isoleucine is included in the list of amino acids for X27 and lysine and proline are removed.. [0089] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X14 is A or V X16 is A or E (or X16 is A or E or N) X20 is K or Q X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; and X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V. De novo proteins of the present invention include those above wherein for X17, tyrosine is included in the list of amino acids for X18, proline is removed from the list of amino acids for X19, proline is removed from the list of amino acids for X22, X23, X24 and X25, methionine is included in the list of amino acids for X21, histidine is included in the list of amino acids for X23,methionine and proline are removed from the list of amino acids for X26, andisoleucine is included in the list of amino acids for X27 and lysine and proline are removed. [0090] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein: X14 is A or V; X15 is E; X16 is A or E; X17 is A; X18 is R; X19 is A; X20 is K or Q;
X21 is E; X22 is A; X23 is E X24 is A; X25 is K; X26 is A; and X27 is D. [0091] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X14, X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; X15 E; X16 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably from A, F, I, L, M, P, E, or V); X18 is R X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X21 is E; X23 is E; X25 is K; and X27 is D. De novo proteins of the present invention include those above wherein phenylalanine is removed from the list of amino acids for X14 and X17, proline is removed from the list of amino acids for X20, X22, and X24, and methionine and proline are removed from the list of amino acids for X26. [0092] In some such aspects, X14 is an amino acid selected from A or V; X16 is an amino acid selected from A or E; and X20 is an amino acid selected from K or Q. [0093] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X14 is an amino acid selected from A or V X16 is an amino acid selected from A or E X20 is an amino acid selected from K or Q
X15, X17, X18, X19, X21, X22, X23, X24, X26 X25, X26 and X27 can be as provided in any of the embodiments herein. [0094] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein (i) X15 is E and X14, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, and X27 are as provided in the any of the embodiments herein for H2; (ii) X18 is R and X14, X15, X16, X17, X19, X20, X21, X22, X23, X24, X25, X26, and X27 are as provided in the any of the embodiments herein for H2; (iii) X21 is E and X14, X15, X16, X17, X18, X19, X20, X22, X23, X24, X25, X26, and X27 are as provided in the any of the embodiments herein for H2; (iv) X23 is E and X14, X15, X16, X17, X18, X19, X20, X21, X22, X24, X25, X26, and X27 are as provided in the any of the embodiments herein for H2; (v) X25 is K and X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X26, and X27 are as provided in the any of the embodiments herein for H2; (vi) X26 is A and X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, and X27, are as provided in the any of the embodiments herein for H2; (vii) X27 is D and X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, and X26, are as provided in the any of the embodiments herein for H2; (viii) X16 is A and X14, X15, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, and X27 are as provided in the any of the embodiments herein for H2; or (ix) at least one, two, three, four, five or six of the following are true: X15 is E; X18 is R; X21 is E; X23 is E; X25 is K; and X27 is D. [0095] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H2 comprises the amino acid sequence: X47X48X49X50X51NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MYX52 X53X54X55X56 (SEQ ID NO:20) wherein X14- X27 are as provided in the any of the embodiments herein for H2; and X47, X48, X49, X50, X51, X52, X53, X54, X55, and X56 are are each independently selected from any amino
acid. In some aspects, X14- X27 are as provided in the any of the embodiments herein for H2; and X49, X52, and X55 are each independently an amino acid selected from A, F, I, L, M, P or V; X50 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X54 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, I, L, M, P or V); and X47, X48, X51, X53, and X56 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T. De novo proteins of the present invention include those above wherein cysteine and glutamine are included in the list of amino acids for X47 and lysine is removed, phenylalanine and tyrosine are included in the list of amino acids for X48, histidine is included in the list of amino acids for X52 and X54, and aspartic acid is removed from the list of amino acids for X56. [0096] Included in the present invention are ACE2 protein decoys wherein X14- X27 are as provided in the any of the embodiments herein for H2; X49, X52, and X55 are each independently an amino acid selected from A, F, I, L, M, P or V; X50 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X54 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, I, L, M, P or V); and X48, X51, X53, and X56 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; and X47 is G. De novo proteins of the present invention include those above wherein cysteine and glutamine are included in the list of amino acids for X47 and lysine is removed, phenylalanine and tyrosine are included in the list of amino acids for X48, histidine is included in the list of amino acids for X52 and X54, and aspartic acid is removed from the list of amino acids for X56. [0097] Included in the present invention are ACE2 protein decoys wherein wherein X14- X27 are as provided in the any of the embodiments herein for H2; X49, X52, and X55 are each independently an amino acid selected from A, F, I, L, M, P or V; X50 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y;
X54 is L; and X48, X51, X53, and X56 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; and X47 is G. De novo proteins of the present invention include those above wherein phenylalanine and tyrosine are included in the list of amino acids for X48, histidine is included in the list of amino acids for X52, and aspartic acid is removed from the list of amino acids for X56. [0098] In some aspects, X47 is G or E; X48 is D; X49 is A; X50 is A; and X51 is R. In some such aspects, X47 is G. In other such aspects, X47 is E. [0099] In some aspects, X52 is A; X53 is E; X54 is L or F or N; X55 is A; and X56 is K. In some such aspects, X54 is L. In other such aspects, X54 is F. In yet other aspects, X54 is N. [00100] Also included in the present invention are those ACE2 protein decoys wherein one or more (preferably not more than 1 to 3) of the amino acids at positions 1, 4, 8, 12, 15, 16, 19, 22 and 23 of SEQ ID NO:5 are substituted and X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, X27 are as described in any of the embodiments provided herein. For example, in some aspects, the following substitution is made E15G. In some aspects, one or more of the following substitions are made: Q16N, Q16Y, L19Y, or M22H. [00101] De novo proteins of the present invention include those wherein X4 is not an amino acid selected from K or R; X22 is not an amino acid selected from E, K, Q, or R; X23 is not an amino acid selected from P; X24 is not an amino acid selected from D or P; X26 is not an amino acid selected from D, E, H, K, P, Q, or R; X9 is not K, P, or R; and X27 is not P. [00102] De novo proteins of the present invention include those wherein H2 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in: NAENAARKAKEFAEEQAKLADMY (SEQ ID NO:21) NVENEARKAQEFAEEQAKLADMY (SEQ ID NO:22) [00103] ACE2 protein decoys of the present invention include those wherein H2 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:21 wherein the amino acid at position 1 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 2 is A or if substituted is C, D, G, H, I, L, M, N, P, R, S, T, V, or W; wherein the amino acid at position 3 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y;
wherein the amino acid at position 4 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y wherein the amino acid at position 5 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y wherein the amino acid at position 6 is A or if substituted is C, D, E, G, I, L, M, N, P, Q, S, T, V, W, or Y; wherein the amino acid at position 7 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, Y, or W; wherein the amino acid at position 8 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 9 is A or if substituted is C, D, G, I, L, Q, S, T, V, or W; wherein the amino acid at position 10 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, or W; wherein the amino acid at position 11 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 12 is F or if substituted is A, C, D, E, G, I, K, L, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 13 is A or if substituted is C, D, F, G, I, L, M, N, S, T, V, W, or Y; wherein the amino acid at position 14 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 15 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 16 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, R, S, T, Y, or V; wherein the amino acid at position 17 is A or if substituted is C, E, F, G, I, L, M, Q, S, T, V, or W; wherein the amino acid at position 18 is K or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 19 is L or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, Y, or W; wherein the amino acid at position 20 is A or if substituted is C, F, G, I, L, S, T, V, or Y;
wherein the amino acid at position 21 is D or if substituted is A, C, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 22 is M or if substituted is A, C, D, E, F, G, H, I, K, L, N, Q, R, S, T, V, W, or Y; and wherein the amino acid at position 23 is Y or if substituted is D, F, H, I, L, M, or V. [00104] Also included are those ACE-2 protein decoys wherein no more 3, 2, or 1 of the amino acids at positions 1, 4, 8, 12, 15, 16, 19, 22 and 23 are substituted. [00105] In some aspects H2 comprises additional amino acids at the N terminus (e.g., at least 5 additional amino acids at the N terminus). In some aspects, the amino acid sequence EDAAR (SEQ ID NO:23) or GDAAR (SEQ ID NO:24) is present at the N terminus. Accordingly, in some aspects H1 comprises a sequence having at least 70%, 80%, 90%, 95% or 100% identity to the sequence GDAAR NAENAARKAKEFAEEQAKLADMY AELAK (SEQ ID NO:244). [00106] In some aspects H2 comprises additional amino acids at the C terminus (e.g., at least 5 additional amino acids at the C terminus). In some aspects, the amino acid sequence AELAK (SEQ ID NO:25) or AEFAK (SEQ ID NO:26) or AENAK (SEQ ID NO:27) is present at the C terminus. [00107] In some aspects, the amino acid sequence AELAK (SEQ ID NO:25) is present at the C terminus and the amino acid sequence GDAAR (SEQ ID NO:24) is present at the N terminus. BETA DOMAIN H3 [00108] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X28X29X30X31X32X33 , X34, X35, and X36, are each independently selected from any amino acid. [00109] Included in the present invention are de novo proteins of the present invention wherein H3 comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein wherein:
X28 is an amino acid selected from A, C, D, E, G, I, L, M, P, Q, R, S, T, V, or W (preferably A, G, I, L, M, Q, T, V, or W); X29 is an amino acid selected from A, C, D, E, G, L, M, P, R, S, T, V, or W (preferably E, L, M, P, S, T, V, or W); X30 is an amino acid selected from C, F, I, L, M, T, V, or W (preferably I, F, or V); X31 is an amino acid selected from A, C, D, E, G, I, K, L, M, N, S, T, or V (preferably D, M, or N); X32 is an amino acid selected from F, I, L, M, or V (preferably L, M, or F); X33 is an amino acid selected from D, G, or L; X34 is an amino acid selected from A, C, E, F, G, I, K, L, Q, R, S, T, V, W, or Y (preferably F, A, E, I, K, L, Q, R, S, or V); X35 is an amino acid selected from A, C, D, E, G, H, K, L, M, P, R, S, T, V, W, or Y (preferably E, D, G, L, M, P, S, V, or W); and X36 is an amino acid selected from A, C, D, F, G, H, I, L, M, N, P, Q, R, S, T, V, or W (preferably I, C, F, M, P, Q, S, T, V, or W). [00110] Included in the present invention are de novo proteins of the present invention wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X31 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X35 is an amino acid selected from D, E, G, K, N, P, Q, R, S, V, or T X29 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, E, G, K, N, P, Q, R, S, T, or V) X33 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably G, A, F, I, L, M, P or V ); X30, X32, and X36 are each independently an amino acid selected from A, F, I, L, M, P or V; X28 is an amino acid selected from A, F, I, L, M, P, T, or V; and X34 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y and optionally C (preferably F, D, E, G, K, N, P, Q, R, S, Y, or T). De novo proteins of the present invention include those above wherein glutamine is included in the list of amino
acids for X28, alanine and proline are removed from the list of amino acids for X30, proline, glutamine, and arginine are removed from the list of amino acids for X31, alanine and proline are removed from the list of amino acids for X32, X33 is an amino acid selected from D, G, or L; and aspartic acid and proline are removed from the list of amino acids for X34. [00111] Included in the present invention are de novo proteins of the present invention wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X31 and X35 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X29 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, E, G, K, N, P, Q, R, S, T, or V) X33 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably G, A, F, I, L, M, P or V ); X28, X30, X32, and X36 are each independently an amino acid selected from A, F, I, L, M, P or V; and X34 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y and optionally C (preferably F, D, E, G, K, N, P, Q, R, S, Y, or T). De novo proteins of the present invention include those above wherein glutamine is included in the list of amino acids for X28, alanine and proline are removed from the list of amino acids for X30, proline, glutamine, and arginine are removed from the list of amino acids for X31, alanine and proline are removed from the list of amino acids for X32, X33 is an amino acid selected from D, G, or L; and aspartic acid and proline are removed from the list of amino acids for X34. [00112] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X35 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X28 is A or V; X29 is E or V;
X31 is D X32 is M or L; X33 is G; X30, and X36 are each independently an amino acid selected from A, F, I, L, M, P or V; and X34 is an amino acid selected from F, Y, K or C. De novo proteins of the present invention include those above wherein alanine and proline are removed from the list of amino acids for X30. [00113] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X28 is A or V; X29 is E or V; X30 is I; X31 is D X32 is M or L; X33 is G; X34 is an amino acid selected from F, Y, K or C; X35 is E; and X36 is I. [00114] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H3, if present, comprises the amino acid sequence: X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6); wherein X28 is A or V or T; X29 is E or V; X30 is I; X31 is D X32 is M or L or I;
X33 is G; X34 is an amino acid selected from F, Y, K, I, or C; X35 is E or V; and X36 is I. [00115] The de novo proteins of the present invention can comprise two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein H3, if present, comprises the amino acid sequence: X57X28X29X30X31X32X33KGDX34RX35X36X58 ; (SEQ ID NO:28) wherein X28-X36 are as provided in the any of the embodiments herein for H3; X57 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X58 is an amino acid selected from D, E, G, K, N, P, Q, R, S, C or T. De novo proteins of the present invention include those above wherein cysteine is included in the list of amino acids for X28 and the amino aicds D, K, M, N, P, Q, and Y are removed from the list of amino acids for X28, and the amino acids A, C, F, H, I, L, M, V, or W are included in the list of amino acids for X58.Also included in the present invention are those ACE2 protein decoys wherein X28, X29, X30, X31, X32, X33, X34, X35, and X36, are as described in any of the embodiments herein and the amino acids at position 7 and/or position 8 of SEQ ID NO:6 are substituted. For example, in some aspects, one or more of the following substitutions are made: K7M or G8R. [00116] Proteins of the present invention include those wherein H3 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NOS: 29-34 or 200. AEIDLGKGDFREI (SEQ ID NO:29) AEIDLGKGDCREI (SEQ ID NO:30) VVIDLGKGDFREI (SEQ ID NO:31) VVIDLGKGDCREI (SEQ ID NO:32) AEIDMGKGDCREI (SEQ ID NO:33) AEIDMGKGDFREI (SEQ ID NO:34) VEIDLGKGDFREI (SEQ ID NO: 200).
[00117] ACE2 protein decoys of the present invention include those wherein H3 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:29 wherein the amino acid at position 1 is A or if susbstituted is C, D, E, G, I, L, M, P, Q, R, S, T, V, or W; wherein the amino acid at position 2 is E or if susbstituted is A, C, D, G, L, M, P, R, S, T, V, or W; wherein the amino acid at position 3 is I or if substituted is C, F, L, M, T, V, or W; wherein the amino acid at position 4 is D or if substituted is A, C, E, G, I, K, L, M, N, S, T, or V; wherein the amino acid at position 5 is L or if substituted is F, I, M, or V; wherein the amino acid at position 6 is G or if substituted is D, or L; wherein the amino acid at position 7 is K or if substituted is I, M, N, Q, R, or T; wherein the amino acid at position 8 is G or if substituted is D, E, M, R, or S; wherein the amino acid at position 9 is D or if substituted is E, K, or T; wherein the amino acid at position 10 is F or if substituted is A, C, E, G, I, K, L, Q, R, S, T, V, W, or Y; wherein the amino acid at position 11 is R or if substituted is K, M, Q, or S; wherein the amino acid at position 12 is E or if substituted is A, C, D, G, H, K, L, M, P, R, S, T, V, W, or Y; and wherein the amino acid at position 13 is I or if substituted is A, C, D, F, G, H, L, M, N, P, Q, R, S, T, V, or W. Also included are those ACE-2 protein decoys wherein no more 3, 2, or 1 of the amino acids at positions 7, 8, 9, and 11 are substituted, wherein numbering is in accordance with SEQ ID NO: 29. [00118] Also included in the present invention are ACE2 protein decoys comprising a H3 domain wherein the amino acid at position X34 is not cysteine. Also included in the present invention are ACE2 protein decoys comprising a H3 domain wherein if X34 is cysteine, X32 is leucine. Also included in the present invention are ACE2 protein decoys including a H3 domain wherein the amino acid at position X34 is selected from D, E, G, K, N, P, Q, R, S, or T. Also included in the present invention ar ACE2 protein decoys including a H3 domain wherein the amino acid at position X34 is an amino acid selected from F, Y, K or C.
[00119] In some aspects, H3 comprises at least one additional amino acid at the N terminus, preferably an amino acid that doesn’t negatively impact binding to the coronavirus spike protein. In some aspects, the amino acid is selected from D, E, G, K, N, P, Q, R, S, Y, or T. In some aspects, the amino acid is selected from A, C, E, F, G, I, L, R, S, T, V, or W. In other aspects, the amino acid is selected from S, P, T, or Y or from L, S, P, T, or Y. In some aspects, the amino acid is S or P (preferably S). Accordingly, in some aspects H3 comprises a sequence having at least 70%, 80%, 90%, 95% or 100% identity to the sequence SAEIDLGKGDFREIR (SEQ ID NO: 245) or SVEIDLGKGDFREIR (SEQ ID NO:246) [00120] In some aspects H3 comprises at least one additional amino acid at the C terminus, preferably an amino acid that doesn’t negatively impact binding to the coronavirus spike protein. In some aspects, the amino acid is selected from L, D, E, G, K, N, P, Q, R, S, or T or A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V or W . In some aspects, the amino acid is R. [00121] It will be understood by the skilled practitioner than any of the H1, H2, and optional H3 domains described herein can be combined for use in the present invention. [00122] De novo proteins of the present invention comprise at least one structural domain that facilitates protein folding and binding-competent presentation of the alpha helices and beta hairpin domains to the coronavirus spike protein. Preferred structural domains provide the de novo proteins with a hydrophobic core and serve to stabilize the relative position and orientation of the binding motifs in a manner that is competent for binding. The supporting structures can be computationally generated and placed by an available method (e.g. Rosetta fragment assembly, parametric generation, and the like) or extracted from existing structures (see, e.g., examples herein). Unlike the H1, H2, and H3 regions, these structural domains do not substantially map to the structural domains of the ACE2 protein (i.e., do not structurally or sequentially align to other secondary structure elements in ACE2). Using the teachings of the present invention, in addition to the skill in the art, a skilled practitioner could use protein design principles to create structural domains for use in the present invention. [00123] Structural domains that facilitate protein folding and binding-competent presentation of H1, H2, and H3, if present, can comprise an amino acid sequence set forth below for D1 and D2:
D1 – XAXAXBXBXCXBXBXBXAXBXBXAXCXBXCXAXBXCXAXCXCXAXAXBXCXAXA (SEQ ID NO:35). D2 – XAXCXCXAXBXBXAXCXBXBXAXBXBXAXCXBXBXAXBXBXDXAXBXBXAXCXBXBXA XC (SEQ ID NO:36) wherein each XA is independently an amino acid selected from D, E, G, K, N, P, Q, R, S, C, and T; each XB is independently an amino acid selected from A, F, I, L, M, C, and P (preferably A, F, I, L, M, and P), each XC is independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, Y or C; and each XD is independently an amino acid from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, Y or C. In some embodiments XD is an amino acid selected from A, F, I, L, M, P, or V. In other embodiments XD is an amino acid selected from D, E, G, K, N, P, Q, R, S, T, or C. [00124] In some embodiments, D1 comprises the amino acid sequence set forth below: XAXAAAXAALAXAA AXAAMKXAALXAI IXAXAIAXAXA (SEQ ID NO:37); wherein each XA is independently an amino acid selected from D, E, G, K, N, P, Q, R, S, C, or T. [00125] In some embodiments, D1 comprises an amino acid sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identical to the amino acid sequence set forth below: REAAEALAEAARAMKEALEIIREIAEK (SEQ ID NO:38) REAAEALAEAARAMKEALEILREIAEK (SEQ ID NO:222). [00126] ACE2 protein decoys of the present invention include those wherein at least one structural domain (e.g., D1) comprises an amino acid sequence having at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:38 wherein the amino acid at position 1 is R or if substituted is A, C, E, F, G, I, K, L, M, P, S, T, V, or W (preferably C, E, F, G, K, L, M, P, S, T, or W ); wherein the amino acid at position 2 is E or if substituted is A, C, D, F, G, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, G, K, M, V, W, or Y); wherein the amino acid at position 3 is A or if substituted is C, E, G, K, L, M, P, Q, R, S, T, V, W, or Y (preferably C, K, P, Q, or V); wherein the amino acid at position 4 is A or if substituted is D, E, G, I, K, L, M, N, P, R, S, T, V, or W (preferably E, N, T, V, or W) ;
wherein the amino acid at position 5 is E or if substituted is C, D, G, K, L, Q, R, S, T, V, W, or Y (preferably C, D, Q, S, V, W, or Y); wherein the amino acid at position 6 is A or if substituted is C, D, E, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, K, P, R, V, or Y); wherein the amino acid at position 7 is L or if substituted is A, C, F, I, M, Q, S, T, or V (preferably T); wherein the amino acid at position 8 is A or if substituted is C, D, E, F, G, H, I, K, Q, L, M, R, S, T, V, or W (preferably D, E, G, H, I, L, Q, R, S, V, or W); wherein the amino acid at position 9 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, R, S, V, W, or Y (preferably A, D, H, L, M, N, R, S, or V); wherein the amino acid at position 10 is A or if substituted is C, G, L, M, Q, S, T, V, or W (preferably C, G, M, or S); wherein the amino acid at position 11 is A or if substituted is C, D, G, L, M, N, Q, R, S, T, or V (preferably C, G, M, S, T, or V); wherein the amino acid at position 12 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, K, M, N, P, Q, S, T, V, W, or Y); wherein the amino acid at position 13 is A or if substituted is C, D, E, F, G, H, K, L, M, P, Q, R, S, T, V, W, or Y (preferably D, E, K, M, R, S, or V); wherein the amino acid at position 14 is M or if substituted is A, C, D, E, G, H, I, K, L, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, K, R, S, T, V, or Y ); wherein the amino acid at position 15 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, G, H, M, R, S, or Y); wherein the amino acid at position 16 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, G, K, L, M, Q, T, V, or W); wherein the amino acid at position 17 is A or if substituted is C, G, P, S, T, or V (preferably C, G, or T); wherein the amino acid at position 18 is L or if substituted is C, F, H, I, K, M, N, Q, R, T, V, W, or Y (preferably C, F, H, or V); wherein the amino acid at position 19 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, F, G, L, Q, R, S, T, V, or Y);
wherein the amino acid at position 20 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, Q, R, S, T, V, W, or Y (preferably C, E, G, L, Q, R, S, T, V, or Y); wherein the amino acid at position 21 is I or if substituted is A, C, D, E, F, G, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, F, L, M, N, S, T, V, or Y); wherein the amino acid at position 22 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, Y, or W (preferably A, C, D, E, F, G, I, L, M, Q, S, T, V, or Y); wherein the amino acid at position 23 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, F, H, I, M, N, P, T, or W); wherein the amino acid at position 24 is I or if substituted is A, C, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, or Y (preferably C, S, T, or V); wherein the amino acid at position 25 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, G, H, I, M, N, S, V, or Y); wherein the amino acid at position 26 is E or if substituted is A, C, D, F, G, H, I, K, L, M, Q, R, S, T, V, W, or Y (preferably C, F, I, L, S, T, or Y); and wherein the amino acid at position 27 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, F, G, H, M, N, S, or Y). [00127] In some embodiments D2 comprises an amino acid sequence set forth in SEQ ID NO: 39 or 40: XAAXAXAAAXAXA IAXAAIXAXAAAXA AIAXAAAXAIAA XAA (SEQ ID NO:39) XAAXAXAAAXAXA VAXAAIXAXAAAXA AIVXAAAXAIAA XAA (SEQ ID NO:40); wherein each XA is independently an amino acid selected from D, E, G, K, N, P, Q, R, S, C, or T. [00128] In some embodiments D2 comprises the amino acid sequence set forth below: RASEAAKRX59AX60AIRKAAD AIX61X62AAKIAA RA (SEQ ID NO:41), wherein X59 is I or V, X60 is K or R or C, X61 is A or V or C, X62 is E or C. [00129] In some embodiments D2 comprises an amino acid sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identical to an amino acid sequence set forth in SEQ ID NO:42-46: RASEAAKR IAKAIRKAAD AIAEAAKIAA RA (SEQ ID NO:42); RASEAAKR IACAIRKAAD AIAEAAKIAA RA (SEQ ID NO:43); RASEAAKR IAKAIRKAAD AIACAAKIAA RA (SEQ ID NO:44); RASEAAKR VARAIRKAAD AIVEAAKIAA RA (SEQ ID NO:45);
RASEAAKR VACAIRKAAD AIVEAAKIAA RA (SEQ ID NO:46). [00130] ACE2 protein decoys of the present invention include those wherein at least one structural domain (e.g., D2) comprises an amino acid sequence having at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:42 wherein the amino acid at position 1 is R or if susbstituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, H, K, L, N, Q, S, or Y); wherein the amino acid at position 2 is A or if susbstituted is C, G, I, L, M, N, P, Q, S, T, V, or Y (preferably C, M, Q, T, or V); wherein the amino acid at position 3 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y (preferably C, E, F, G, I, L, M, Q, or R); wherein the amino acid at position 4 is E or if substituted is A, C, D, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, I, N, S, or W); wherein the amino acid at position 5 is A or if substituted is C, D, E, F, G, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably D, E, I, M, or Y); wherein the amino acid at position 6 is A or if substituted is C, F, G, S, or T (preferably C or S); wherein the amino acid at position 7 is K or if substituted is A, C, D, E, G, H, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, R, S, T, V, W, or Y); wherein the amino acid at position 8 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, Q, S, T, V, or Y); wherein the amino acid at position 9 is I or if substituted is A, C, F, G, K, L, M, Q, S, T, V, W, or Y (preferably A, C, F, G, L, M, S, T, W, or Y); wherein the amino acid at position 10 is A or if substituted is D, G, T, or V (preferably D, G, or V); wherein the amino acid at position 11 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, L, M, Q, R, S, V, W, or Y); wherein the amino acid at position 12 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably E, G, I, S, or T); wherein the amino acid at position 13 is I or if substituted is A, C, D, E, F, G, H, L, M, N, Q, S, T, V, or Y (preferably A, C, D, F, G, L, M, N, Q, S, T, or V);
wherein the amino acid at position 14 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably F, H, K, L, N, V, or W); wherein the amino acid at position 15 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y); wherein the amino acid at position 16 is A or if substituted is C, F, G, M, P, S, T, V, or Y (preferably G, T, or Y); wherein the amino acid at position 17 is A or if substituted is C, D, E, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably G, T, or V); wherein the amino acid at position 18 is D or if substituted is A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, G, I, L, N, R, S, T, W, or Y) ; wherein the amino acid at position 19 is A or if substituted is C, D, E, F, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably G, K, M, Q, S, or T); wherein the amino acid at position 20 is I or if substituted is A, C, F, G, H, L, M, Q, T, V, W, or Y (preferably G, L, M, T, V, or Y); wherein the amino acid at position 21 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably D, E, G, I, K, M, N, Q, S, T, V, W, or Y); wherein the amino acid at position 22 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, G, K, M, P, S, T, V, W, or Y); wherein the amino acid at position 23 is A or if substituted is C, G, N, S, T, or V (preferably G, S, or T); wherein the amino acid at position 24 is A or if substituted is C, D, E, G, K, M, N, S, T, or V (preferably C, G, or T); wherein the amino acid at position 25 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, I, L, P, Q, R, S, V, W, or Y); wherein the amino acid at position 26 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, K, L, M, P, Q, R, S, or V); wherein the amino acid at position 27 is A or if substituted is C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably F, G, M, N, S, T, or V); wherein the amino acid at position 28 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably C, D, E, G, H, Q, S, T, V, or Y);
wherein the amino acid at position 29 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, G, H, I, K, L, M, N, P, S, T, V, W, or Y); wherein the amino acid at position 30 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, G, H, K, N, P, Q, R, S, T, or V). [00131] It will be understood by the skilled practitioner that the D1 and D2 domains described herein can be combined with any of the H1, H2, and H3 domains described herein. [00132] The de novo proteins of the present invention optionally comprise amino acid linkers between the domains. The amino acid linkers may be of any length as deemed appropriate for an intended use. The linkers can be, for example, from 1 to 100 amino acids in length, such as 1-100, 1-90, 1-80, 1-70, 1-60, 1-50, 1-40, 1-30, 1-20, 1-10, or 1-5 amino acids in length. As with the variability permitted in the amino acid residues and flexibility in domain order, the flexibility in linker stems from the use of de novo protein design to construct the proteins of the present invention. In these proteins, the majority of the contributions to protein folding come from interactions among the secondary structure elements rather than from the linkers. At least for that reason, the linkers can generally be modified in de novo designed proteins without compromising protein folding. In some embodiments, the linkers result in variable loop regions between the domains. [00133] An exemplary ACE2 protein decoy of the present invention is CTC-445 and is as set forth in SEQ ID NO:47. SAEIDMGKGDFREIRASEDAREAAEALAEAARAMKEALEIIREIAEKLRDSSR ASEAAKRIAKAIRKAADAIAEAAKIAARAAKDEDAARNAENAARKAKEFAEE QAKLADMYAEFAKNGDKSRVREQLKTFADKAFHEMEDRFYQAALAVFEAA EAAAG (SEQ ID NO:47) ACE2 protein decoy CTC-445 comprises a H1, H2, and H3 domain as well as two structural domains that facilitate protein folding and binding-competent presentation of H1, H2, and H3. In CTC-445, the order of the domains is H3-D1-D2-H2-H1. H3 is from amino acid 1-15; D1 is from amino acid 21-47; D2 is from amino acid 53-82; H2 is from amino acid 86-118; and H1 is from amino acid 123-160. The ACE2 protein decoy also includes four linkers linking together the various domains. The first linker is from amino acid 16-20, the second linker is from amino acid 48-52, the third linker is from amino acid 83-85 and the fourth linker is from amino acid 119-122. Numbering is according to SEQ ID NO:47. The teachings provided herein with respect to the H1, H2, H3, D1 and D2 domains, in
addition to the examples provided herein and the skill in the art, can be used to make ACE2 protein decoys that are variants of CTC-445. In some embodiments, exemplary variants are those that have introduced amino acid substitutions that play a role in optimizing the stability and/or folding of the protein. Typically, these substitutions are not at the binding interface but at other locations in the protein. Although these substitutions are not at the binding interface, they can lead to improved binding affinity, in addition to improved activity. Methods of testing proteins for improved binding, stability, and or protein folding are known in the art and are described herein. CTC-445 has been demonstrated to specifically bind to the SARS-COV-2 spike protein but only weakly bind to the SARS- CoV-1 spike protein. In some embodiments, ACE2 protein decoys that are variants of CTC- 445 are capable of binding to both the SARS-COV-2 spike protein and the SARS-COV-1 spike protein with higher affinity as compared to CTC-445. Exemplary ACE2 protein decoys having identity to CTC-445 include those set forth in SEQ ID NOS:48-68, 184-188, 104-172, and 224-239. Also included in the present invention are those ACE2 protein decoys comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS:47-68, 184-188, 104-172, 224-239, 255-257 or 265. The teachings provided herein with respect to the H1, H2, H3, D1 and D2 domains, in addition to the examples provided herein and the skill in the art, can be used to make variants of such ACE2 protein decoys. Table 1
In some embodiments, the amino acid residue at position 88 of any of SEQ ID NOS:47-68, 184-187, and 104-172, if not A, is selected from F, I, L, M, P or V. In some embodiments, the amino acid residue at position 137 of any of SEQ ID NOS: 47-68, if not F, is D, E, G, K, N, P, Q, R, S, or T. In some embodiments, if the amino acid residue at position 11 of any of SEQ ID NOS:47-68, 184-187, and 104-172 is cysteine, the amino acid residue at position 6 is L and/or the amino acid residue at position 126 is L and/or the amino acid residue at position 124 is S. In some embodiments, the ACE2 protein decoy does not have the amino acid sequence of CTC- 625 or CTC-626. In some embodiments, the ACE2 protein decoy does not have the amino acid substitutions set forth in CTC-625 (i.e., S1P_F11Y_R42S_E46S_A88N_F116N_R124S_F137V_R143L) or CTC-626 (i.e., S1P_M6L_F11Y_R42S_E46S_A88N_F116N_R124S_F137V_R143L-F152W). [00134] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS:47-68, 184-187, or 104-172, wherein a. the amino acid residue at position 2 is V; or b. the amino acid residue at position 3 is V; or c. the amino acid residue at position 6 is L; or d. the amino acid residue at position 11 is F or C; or e. the amino acid residue at position 41 is L; or
f. the amino acid residue at position 61 is V; or g. the amino acid residue at position 63 is R or C; or h. the amino acid residue at position 73 is V; or i. the amino acid residue at position 74 is E or C; or j. the amino acid residue at position 84 is T; or k. the amino acid residue at position 86 is G; or l. the amino acid residue at position 92 is V; or m. the amino acid residue at position 95 is E; or n. the amino acid residue at position 100 is Q; or o. the amino acid residue at position 116 is L; or p. the amino acid residue at position 124 is S; or q. the amino acid residue at position 126 is L; or r. the amino acid residue at position 136 is T; or s. the amino acid residue at position 143 is S or L; or t. any combinaton of (a)- (s) above. [00135] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS:47-68, 184-187, 104-172, 255-256, or 224-239 wherein no more than 1 of the amino acids at positions 8, 9, or 10 is substituted; no more than 3, no more than 2 or no more than 1 of the amino acids at positions 91, 94, 98, 102, 105, 106, 109, 112, or 113 is substituted; no more than 4, no more than 3, and/or no more than 2 or no more than 1 of the amino acids at positions 123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted. [00136] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS:47-68, 184-187, 104-172, 255-256, or 224-239 wherein no more than 4, 3, 2, or 1 of the amino acids at positions 8, 9, 10, 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted. [00137] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%,
99% or 100% identical to an amino acid sequence set forth in SEQ ID NO:47-68, 184-187, 104-172, 255-256, or 224-239, wherein a. the amino acid residue at position 8 is K; b. the amino acid residue at position 9 is G; c. the amino acid residue at position 10 is D d. the amino acid residue at position 91 is N e. the amino acid residue at position 94 is N f. the amino acid residue at position 98 is K g. the amino acid residue at position 102 is F h. the amino acid residue at position 105 is E i. the amino acid residue at position 106 is Q j. the amino acid residue at position 109 is L k. the amino acid residue at position 112 is M l. the amino acid residue at position 113 is Y m. the amino acid residue at position 123 is S n. the amino acid residue at position 127 is E o. the amino acid residue at position 128 is Q p. the amino acid residue at position 131 is T q. the amino acid residue at position 132 is F r. the amino acid residue at position 134 is D s. the amino acid residue at position 138 is H t. the amino acid residue at position 139 is E u. the amino acid residue at position 141 is E v. the amino acid residue at position 142 is D w. the amino acid residue at position 145 is Y x. the amino acid residue at position 146 is Q; and y. the amino acid residue at position 149 is L [00138] As taught herein, a great deal of variability can be present in the linkers of the exemplary protein decoys. Provided herein are de novo proteins include those comprising a sequence at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99%
or 100% identical to an amino acid sequence set forth in SEQ ID NOS: 69-90, 258-260, 266, or 189-193 wherein XL is an amino acid linker. In some such aspects, the first and second XL linker in each de novo protein is from 0-5 amino acids, the third XL linker in each de novo protein is from 0-3 amino acids, and the fourth XL linker in each de novo protein is from 0-4 amino acids. Table 2
[00139] In some embodiments, the amino acid residue at position 88 of any of SEQ ID NOS: 69-90, 258-259, or 189-192, if not A, is selected from F, I, L, M, P or V; wherein position 88 is in reference to SEQ ID NO:47 with fixed linker lengths. In some embodiments, the amino acid residue at position 137 of any of SEQ ID NOS: 69-90 or 189- 192, if not F, is D, E, G, K, N, P, Q, R, S, or T. In some embodiments, if the amino acid residue at position 11 of any of SEQ ID NOS: 69-90, 258-259, or 189-192 is cysteine, the amino acid residue at position 6 is L and/or the amino acid residue at position 126 is L and/or the amino acid residue at position 124 is S. Positions 88, 137, 11, 124, and 126 referred to above mean the positions in SEQ ID NOs: 69-90, 258-259, or 189-192 that correspond to positions 88, 137, 11, 124, and 126, respectively, in SEQ ID NO:47, and not the actual positions in SEQ ID NOS: 69-90 or 189-193, which may vary due to the non- fixed length of the linkers XL. Thus, reference to “position 88 of any one of SEQ ID NOs: 69-90 or 189-192” means the position in any one of SEQ ID NOs: 69-90, 258-259, or 189- 193 corresponding to position 88 in SEQ ID NO: 47. [00140] Exemplary de novo proteins of the present invention include those comprising a sequence at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99%
or 100% identical to the amino acid sequence set forth in SEQ ID NO: 69-90, 258-259, or 189-192 wherein a. the amino acid residue at position 2 is V; or b. the amino acid residue at position 3 is V; or c. the amino acid residue at position 6 is L; or d. the amino acid residue at position 11 is F or C; or e. the amino acid residue at position 41 is L; or f. the amino acid residue at position 61 is V; or g. the amino acid residue at position 63 is R or C; or h. the amino acid residue at position 73 is V; or i. the amino acid residue at position 74 is E or C; or j. the amino acid residue at position 86 is G; or k. the amino acid residue at position 92 is V; or l. the amino acid residue at position 95 is E; or m. the amino acid residue at position 100 is Q; or n. the amino acid residue at position 116 is L ; or o. the amino acid residue at position 124 is S; or p. the amino acid residue at position 126 is L; or q. the amino acid residue at position 136 is T; or r. the amino acid residue at position 143 is S or L; or any combination of (a) – (r) – above, wherein the noted positions are according to the numbering of SEQ ID NO:47 not of SEQ ID NOS: 69-90 or 189-192 due to the non-fixed length of the linkers XL, as discussed above. [00141] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to the amino acid sequence set forth in SEQ ID NO: 69-90, 258-259, or 189-192 wherein no more than 1 of the amino acids at positions 8, 9, or 10 is substituted; no more than 3, no more than 2 or no more than 1 of the amino acids at positions 91, 94, 98, 102, 105, 106, 109, 112, or 113 is substituted; no more than 3, no more than 2 or no more than 1 of the amino acids at positions 123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted. The noted positions are according to the numbering of SEQ
ID NO:47 not of SEQ ID NOS: 69-90, 258-259, or 189-192 due to the non-fixed length of the linkers XL, as discussed above. [00142] Exemplary de novo proteins of the present invention include those comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to the amino acid sequence set forth in SEQ ID NO: 69-90, 258-259, or 189-192 wherein no more than 4, 3, 2, or 1 of the amino acids at positions 8, 9, 10, 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted. The noted positions are according to the numbering of SEQ ID NO:47 not of SEQ ID NOS: 69-90, 258-259, or 189-192 due to the non-fixed length of the linkers XL, as discussed above. [00143] Exemplary de novo proteins of the present invention include those comprising a sequence at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to the amino acid sequence set forth in SEQ ID NO: 69-90, 258-259, or 189-192 wherein: a. the amino acid residue at position 8 is K; b. the amino acid residue at position 9 is G; c. the amino acid residue at position 10 is D d. the amino acid residue at position 91 is N e. the amino acid residue at position 94 is N f. the amino acid residue at position 98 is K g. the amino acid residue at position 102 is F h. the amino acid residue at position 105 is E i. the amino acid residue at position 106 is Q j. the amino acid residue at position 109 is L k. the amino acid residue at position 112 is M l. the amino acid residue at position 113 is Y m. the amino acid residue at position 123 is S n. the amino acid residue at position 127 is E o. the amino acid residue at position 128 is Q p. the amino acid residue at position 131 is T q. the amino acid residue at position 132 is F
r. the amino acid residue at position 134 is D s. the amino acid residue at position 138 is H t. the amino acid residue at position 139 is E u. the amino acid residue at position 141 is E v. the amino acid residue at position 142 is D w. the amino acid residue at position 145 is Y x. the amino acid residue at position 146 is Q; and y. the amino acid residue at position 149 is L; wherein the noted positions are according to the numbering of SEQ ID NO:47 not of SEQ ID NOS: 69-90 or 189-192 due to the non-fixed length of the linkers XL, as discussed above. [00144] Including in the present invention are ACE2 protein decoys comprising a sequence at least 50%, 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to the amino acid sequence set forth in SEQ ID NO:47 provided that the following substitutions are present (i) M6L_R126L; (ii) F116L_R124S; (iii) M6L_F116L_R124S_R126L; (iv) M6L_E86G_F116L_R124S_R126L; (v) A2V_E3V_M6L_I61V_K63R_A73V_K84T_E86G_A92V_A95E_ K100Q_F116L_R124S_R126L _A136T_R143S; (vi) M6L_F11C_R126L; (vii) M6L_K63C_R126L; (viii) M6L_E74C_R126L; (ix) F11C_F116L_R124S; (x) K63C_F116L_R124S; (xi) E74C_F116L_R124S; (xii) M6L_F11C_F116L_R124S_R126L; (xiii) M6L_K63C_F116L_R124S_R126L; (xiv) M6L_E74C_F116L_R124S_R126L; (xv) A2V_E3V_M6L_F11C_I61V_K63R_A73V_K84T_E86G_A92V_ A95E_K100Q_F116L_R124S_ R126L_A136T_R143S; (xvi) A2V_E3V_M6L_I61V_K63C_A73V_K84T_E86G_A92V_A95E_ K100Q_F116L_ R124S_R126L_A136T_R143S; (xvii) A2V_E3V_M6L_I61V_K63R_A73V_E74C_K84T_E86G_A92V_ A95E_K100Q_F116L_ R124S_R126L_A136T_R143S; (xviii) M6L_F11C_E86G_F116L_R124S_R126L; (xix) M6L_K63C_E86G_F116L_R124S_R126L; (xx) M6L_E74C_E86G_F116L_R124S_R126L; (xxi) A2V_M6L_E86G_F116L_R124S_R126L; (xxii) A2V_M6L_E86G_F116L_R124S_R126L_R143L; (xxiii) M6L_I41L_E86G_F116L_R124S_R126L_R143L; or (xxiv) A2V_M6L_I41L_E86G_F116L_R124S_R126L_R143L.
[00145] In some preferred embodiments of the present invention, when the ACE2 protein decoy comprises a sequence at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identical to the amino acid sequence for (i) CTC 637: the following amino acids are present: 6L and 126L; (ii) CTC-638; the following amino acids are present: 116L and 124S; (iii) CTC-639; the following amino acids are present: 6L, 116L, 124S, and 126L (iv) CTC-640; the following amino acids are present: 6L, 86G, 116L, 124S, and 126L (v) CTC-641; the following amino acids are present: 2V, 3V, 6L, 61V, 63R, 73V, 84T, 86G, 92V, 95E, 100Q, 116L, 124S, 126L , 136T, and 143S (vi) CTC-642 ; the following amino acids are present: 6L, 11C, and 126L (vii) CTC-643; the following amino acids are present: 6L, 63C, and 126L (viii) CTC-644; the following amino acids are present: 6L, 74C, and 126L (ix) CTC-645; the following amino acids are present: 11C, 116L, and 124S (x) CTC-646; the following amino acids are present: 63C, 116L, and 124S (xi) CTC-647; the following amino acids are present:74C, 116L, and 124S (xii) CTC-648; the following amino acids are present: 6L, 11C, 116L, 124S, and 126L (xiii) CTC-649; the following amino acids are present: 6L, 63C, 116L, 124S, and 126L (xiv) CTC-650; the following amino acids are present: 6L, 74C, 116L, 124S, and 126L (xv) CTC-651; the following amino acids are present: 2V, 3V, 6L, 11C, 61V, 63R, 73V, 84T, 86G, 92V, 95E, 100Q, 116L, 124S, 126L, 136T, and 143S (xvi) CTC-652; the following amino acids are present: 2V, 3V, 6L, 61V, 63C, 73V, 84T, 86G, 92V, 95E, 100Q, 116L, 124S, 126L, 136T, and 143S (xvii) CTC-653; the following amino acids are present: 2V, 3V, 6L, 61V, 63R, 73V, 74C, 84T, 86G, 92V, 95E, 100Q, 116L, 124S, 126L, 136T, and 143S (xviii) CTC-656: the following amino acids are present:1P, 11K, 42S, 46S, 81H, 88N, 116N, 124S, 137V, and 143L; (xix) CTC-693: the following amino acids are present: 6L, 11C, 86G, 116L, 124S, and 126L; (xx) CTC-694: the following amino acids are present: 6L, 63C, 86G, 116L, 124S, and 126L; (xxi) CTC-695: the following amino acids are present: 6L, 74C, 86G, 116L, 124S, and 126L; (xxii) CTC-699; the following amino acids are present 2V, 6L, 86G, 116L, 124S, and 126L; (xxiii) CTC-700; the following amino acids are present: 2V, 6L, 86G, 116L, 124S, 126L, 143L; (xxiv) CTC-701; the following amino acids are present 6L, 41L, 86G, 116L, 124S, 126L, and 143L; and (xxv) CTC-702; the following amino acids are present 2V, 6L, 41L, 86G, 116L, 124S, 126L, and R143. [00146] Included in the present invention are de novo proteins of the present invention comprising a decoy unit comprises an amino acid sequence at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, 91%, 92%, 93%, 94%,
95%, 96%, 97%, 98%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NO: 50 (CTC-640) wherein wherein the amino acid at position 1 is S or if substituted is A, C, E, F, G, I, L, R, S, T, V, or W (preferably C, E, G, I, or L); wherein the amino acid at position 2 is A or if substituted is C, D, E, G, I, L, M, P, Q, R, S, T, V, or W (preferably G, I, L, M, Q, T, V, or W); wherein the amino acid at position 3 is E or if substituted is A, C, D, G, L, M, P, R, S, T, V, or W (preferably L, M, P, S, T, V, or W); wherein the amino acid at position 4 is I or if substituted is C, F, L, M, T, V, or W (preferably F, or V); wherein the amino acid at position 5 is D or if substituted is A, C, E, G, I, K, L, M, N, S, T, or V (preferably M or N); wherein the amino acid at position 6 is L or if substituted is F, I, M, or V (preferably M or F); wherein the amino acid at position 7 is G or if substituted is D or L; wherein the amino acid at position 8 is K or if substituted is I, M, N, Q, R, or T (preferably M); wherein the amino acid at position 9 is G or if substituted is D, E, M, R, or S (preferably R); wherein the amino acid at position 10 is D or if substituted is E, K, or T (preferably unsubstituted); wherein the amino acid at position 11 is F or if substituted is A, C, E, G, I, K, L, Q, R, S, T, V, W, or Y (preferably A, E, I, K, L, Q, R, S, or V); wherein the amino acid at position 12 is R or if substituted is K, M, Q, or S (preferably unsubstituted); wherein the amino acid at position 13 is E or if substituted is A, C, D, G, H, K, L, M, P, R, S, T, V, W, or Y (preferably D, G, L, M, P, S, V, or W); wherein the amino acid at position 14 is I or if substituted is A, C, D, F, G, H, L, M, N, P, Q, R, S, T, V, W (preferably I, C, F, M, P, Q, S, T, V, or W); wherein the amino acid at position 15 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W (preferably C, D, E, F, H, K, L, Q, S, V, W); wherein the amino acid at position 16 is A or if substituted is A, D, E, F, G, L, M, R, S, T,
V, W (preferably E, F, G, L, M, S, T, V, W); wherein the amino acid at position 17 is S or if substituted is A, C, D, E, G, K, L, M, P, Q, R, S, T, V, W (preferably A, C, D, E, G, L, P, T, V, W); wherein the amino acid at position 18 is E or if substituted is A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y (preferably C, G, I, L, M, N, P, R, S, T, V); wherein the amino acid at position 19 is D or if substituted is A, C, D, E, G, I, K, L, M, N, P, R, S, T, V, W, Y (preferably C, E, G, M, P, R, V, W); wherein the amino acid at position 20 is A or if substituted is A, C, E, G, I, L, P, Q, R, S, T, V, W (preferably L, R, S, T, V, W); wherein the amino acid at position 21 is R or if substituted is A, C, E, F, G, I, K, L, M, P, S, T, V, or W (preferably C, E, F, G, K, L, M, P, S, T, or W ); wherein the amino acid at position 22 is E or if substituted is A, C, D, F, G, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, G, K, M, V, W, or Y); wherein the amino acid at position 23 is A or if substituted is C, E, G, K, L, M, P, Q, R, S, T, V, W, or Y (preferably C, K, P, Q, or V); wherein the amino acid at position 24 is A or if substituted is D, E, G, I, K, L, M, N, P, R, S, T, V, or W (preferably E, N, T, V, or W); wherein the amino acid at position 25 is E or if substituted is C, D, G, K, L, Q, R, S, T, V, W, or Y (preferably C, D, Q, S, V, W, or Y); wherein the amino acid at position 26 is A or if substituted is C, D, E, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, K, P, R, V, or Y); wherein the amino acid at position 27 is L or if substituted is A, C, F, I, M, Q, S, T, or V (preferably T); wherein the amino acid at position 28 is A or if substituted is C, D, E, F, G, H, I, K, Q, L, M, R, S, T, V, or W (preferably D, E, G, H, I, L, Q, R, S, V, or W); wherein the amino acid at position 29 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, R, S, V, W, or Y (preferably A, D, H, L, M, N, R, S, or V); wherein the amino acid at position 30 is A or if substituted is C, G, L, M, Q, S, T, V, or W (preferably C, G, M, or S); wherein the amino acid at position 31 is A or if substituted is C, D, G, L, M, N, Q, R, S, T, or V (preferably C, G, M, S, T, or V);
wherein the amino acid at position 32 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, K, M, N, P, Q, S, T, V, W, or Y); wherein the amino acid at position 33 is A or if substituted is C, D, E, F, G, H, K, L, M, P, Q, R, S, T, V, W, or Y (preferably D, E, K, M, R, S, or V); wherein the amino acid at position 34 is M or if substituted is A, C, D, E, G, H, I, K, L, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, K, R, S, T, V, or Y ); wherein the amino acid at position 35 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, G, H, M, R, S, or Y); wherein the amino acid at position 36 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, G, K, L, M, Q, T, V, or W); wherein the amino acid at position 37 is A or if substituted is C, G, P, S, T, or V (preferably C, G, or T); wherein the amino acid at position 38 is L or if substituted is C, F, H, I, K, M, N, Q, R, T, V, W, or Y (preferably C, F, H, or V); wherein the amino acid at position 39 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, F, G, L, Q, R, S, T, V, or Y); wherein the amino acid at position 40 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, Q, R, S, T, V, W, or Y (preferably C, E, G, L, Q, R, S, T, V, or Y); wherein the amino acid at position 41 is I or if substituted is A, C, D, E, F, G, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, F, L, M, N, S, T, V, or Y); wherein the amino acid at position 42 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, Y, or W (preferably A, C, D, E, F, G, I, L, M, Q, S, T, V, or Y); wherein the amino acid at position 43 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, F, H, I, M, N, P, T, or W); wherein the amino acid at position 44 is I or if substituted is A, C, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, or Y (preferably C, S, T, or V); wherein the amino acid at position 45 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, G, H, I, M, N, S, V, or Y); wherein the amino acid at position 46 is E or if substituted is A, C, D, F, G, H, I, K, L, M, Q, R, S, T, V, W, or Y (preferably C, F, I, L, S, T, or Y);
wherein the amino acid at position 47 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, F, G, H, M, N, S, or Y); wherein the amino acid at position 48 is L or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, Y (preferably C, D, F, G, H, I, P, Q, S, T, W, Y); wherein the amino acid at position 49 is R or if substituted is A,C, D, E, F, G, I, K, L, M, P, Q, R, S, T, V, W, Y (preferably A, D, K, M, Q, S, T, V, Y); wherein the amino acid at position 50 is D or if substituted is A, C, D, E, F, G, K, L, M, N, Q, R, S, T, V, W (preferably C, E, M, T, V); wherein the amino acid at position 51 is S or if substituted is A, C, D, E, F, G, I, K, L, M, P, Q, R, S, T, V, W, Y (preferably A, D, E, F, K, M, P, T, V, Y); wherein the amino acid at position 52 is S or if substituted is A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y (preferably A, E, M, Q); wherein the amino acid at position 53 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, H, K, L, N, Q, S, or Y); wherein the amino acid at position 54 is A or if substituted is C, G, I, L, M, N, P, Q, S, T, V, or Y (preferably C, M, Q, T, or V); wherein the amino acid at position 55is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y (preferably C, E, F, G, I, L, M, Q, or R); wherein the amino acid at position 56 is E or if substituted is A, C, D, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, I, N, S, or W); wherein the amino acid at position 57 is A or if substituted is C, D, E, F, G, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably D, E, I, M, or Y); wherein the amino acid at position 58 is A or if substituted is C, F, G, S, or T (preferably C or S); wherein the amino acid at position 59 is K or if substituted is A, C, D, E, G, H, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, R, S, T, V, W, or Y); wherein the amino acid at position 60 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, Q, S, T, V, or Y); wherein the amino acid at position 61 is I or if substituted is A, C, F, G, K, L, M, Q, S, T, V, W, or Y (preferably A, C, F, G, L, M, S, T, W, or Y); wherein the amino acid at position 62 is A or if substituted is D, G, T, or V (preferably D, G, or V);
wherein the amino acid at position 63 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, L, M, Q, R, S, V, W, or Y); wherein the amino acid at position 64 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably E, G, I, S, or T); wherein the amino acid at position 65 is I or if substituted is A, C, D, E, F, G, H, L, M, N, Q, S, T, V, or Y (preferably A, C, D, F, G, L, M, N, Q, S, T, or V); wherein the amino acid at position 66 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably F, H, K, L, N, V, or W); wherein the amino acid at position 67 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y); wherein the amino acid at position 68 is A or if substituted is C, F, G, M, P, S, T, V, or Y (preferably G, T, or Y); wherein the amino acid at position 69 is A or if substituted is C, D, E, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably G, T, or V); wherein the amino acid at position 70 is D or if substituted is A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, G, I, L, N, R, S, T, W, or Y) ; wherein the amino acid at position 71 is A or if substituted is C, D, E, F, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably G, K, M, Q, S, or T); wherein the amino acid at position 72 is I or if substituted is A, C, F, G, H, L, M, Q, T, V, W, or Y (preferably G, L, M, T, V, or Y); wherein the amino acid at position 73 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably D, E, G, I, K, M, N, Q, S, T, V, W, or Y); wherein the amino acid at position 74 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, G, K, M, P, S, T, V, W, or Y); wherein the amino acid at position 75 is A or if substituted is C, G, N, S, T, or V (preferably G, S, or T); wherein the amino acid at position 76 is A or if substituted is C, D, E, G, K, M, N, S, T, or V (preferably C, G, or T); wherein the amino acid at position 77 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, I, L, P, Q, R, S, V, W, or Y);
wherein the amino acid at position 78 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, K, L, M, P, Q, R, S, or V); wherein the amino acid at position 79 is A or if substituted is C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably F, G, M, N, S, T, or V); wherein the amino acid at position 80 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably C, D, E, G, H, Q, S, T, V, or Y); wherein the amino acid at position 81 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, G, H, I, K, L, M, N, P, S, T, V, W, or Y); wherein the amino acid at position 82 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, G, H, K, N, P, Q, R, S, T, or V); wherein the amino acid at position 83 is A or if substituted is C, D, E, G, K, L, Q, R, S, T, V, W, or Y (preferably C, E, L, S, T, or Y); wherein the amino acid at position 84 is K or if substituted is A, C, D, E, F, G, L, M, N, P, Q, R, S, T, V, or W (preferably E, F, G, M, N, S, or W); wherein the amino acid at position 85 is D or if substituted is A, C, E, G, H, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, L, M, N, Q, S, T, V, or W); wherein the amino acid at position 86 is G or if substituted is A, C,D, E, I, L, M, N, P, Q, R, S, T, V, or W (preferably C, D, E, I, M, N, P, Q, R, S, or T); wherein the amino acid at position 87 is D or if substituted is A, C, E, F,G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, F, G, H, I, M, P, Q, R, S, V, W, or Y); wherein the amino acid at position 88 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, E, H, L, M, N, R, T, V, W, or Y); wherein the amino acid at position 89 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, F, G, L, N, P, Q, S, T, V, or W); wherein the amino acid at position 90 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, H, K, N, P, Q, T, V, W, or Y); wherein the amino acid at position 91 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, D, E, G, K, L, M, P, Q, R, S, T, V, or W); wherein the amino acid at position 92 is A or if substituted is C, D, G, H, I, L, M, N, P, R, S, T, V, or W (preferably C, G, P, T, or V); wherein the amino acid at position 93 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, F, I, K, L, M, N, Q, R, S, T, or V);
wherein the amino acid at position 94 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably D, F, G, I, L, M, Q, S, T, V, or W) wherein the amino acid at position 95 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, E, H, I, L, M, N, Q, R, S, V, W, or Y) wherein the amino acid at position 96 is A or if substituted is C, D, E, G, I, L, M, N, P, Q, S, T, V, W, or Y(preferably C, G, I, or S); wherein the amino acid at position 97 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, Y, or W (preferably A, C, F, G, H, I, K, L, M, N, Q, S, T, V, or Y); wherein the amino acid at position 98 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, G, I, L, P, Q, T, V); wherein the amino acid at position 99 is A or if substituted is C, D, G, I, L, Q, S, T, V, or W (preferably L, T, or V); wherein the amino acid at position 100 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, or W (preferably A, C, D, E, F, G, H, I, Q, R, S, T, V, W, or Y); wherein the amino acid at position 101 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, F, G, H, I, K, L, M, N, R, S, T, V, or W); wherein the amino acid at position 102 is F or if substituted is A, C, D, E, G, I, K, L, M, P, Q, R, S, T, V, W, or Y (C, G, I, K, P, V, W, Y); wherein the amino acid at position 103 is A or if substituted is C, D, F, G, I, L, M, N, S, T, V, W, or Y (preferably C, F, G, I, L, S, or T); wherein the amino acid at position 104 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably A, C, D, G, H, I, L, M, N, R, S, T, V, or Y); wherein the amino acid at position 105 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, F, G, H, K, L, M, Q, R, S); wherein the amino acid at position 106 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, R, S, T, Y, or V (preferably C, D, I, K, N, R, T, Y); wherein the amino acid at position 107 is A or if substituted is C, E, F, G, I, L, M, Q, S, T, V, or W (preferably I or S); wherein the amino acid at position 108 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y (preferably D, G, H, I, Q, or R); wherein the amino acid at position 109 is L or if substituted is A, C, D, E, F, G, H, I, K, M, N, Q, R, S, T, V, Y, or W (preferably A, C, D, F, G, H, I, K, M, N, Q, R, S, T, V, W, Y);
wherein the amino acid at position 110 is A or if substituted is C, F, G, I, L, S, T, V, or Y (preferably I); wherein the amino acid at position 111 is D or if substituted is A, C, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y (preferably C, F, I, S, or T); wherein the amino acid at position 112 is M or if substituted is A, C, D, E, F, G, H, I, K, L, N, Q, R, S, T, V, W, or Y (preferably A, D, E, F, H, I, K, L, Q, R, S, T, V, Y); wherein the amino acid at position 113 is Y or if substituted is D, F, H, I, L, M, or V (preferably F); ; wherein the amino acid at position 114 is A or if substituted is C, D, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, or W (preferably C, D, G, H, N, R, S, or V); wherein the amino acid at position 115 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, G, L, M, Q, R, S, T, or V); wherein the amino acid at position 116 is L or if substituted is A, C, D, E, F, G, H, I, K, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, M, N, Q, S, T, V, or Y); wherein the amino acid at position 117 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably C, D, F, G, I, N, P, or T); wherein the amino acid at position 118 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, L, M, N, R, S, T, V, or Y); wherein the amino acid at position 119 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, D, F, G, H, I, K, M, Q, R, S, T, or Y); wherein the amino acid at position 120 is G or if substituted is A, C, D, E, F, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, E, N, or Q); wherein the amino acid at position 121 is D or if substituted is A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, F, or N); wherein the amino acid at position 122 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, or W); wherein the amino acid at position 123 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y (preferably A, C, D, E, G, H, I, K, L, M, N, P, R, T, V, or W); wherein the amino acid at position 124 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y (preferably A, C, E, F, G, I, L, M, N, Q, R, T, V, or Y); wherein the amino acid at position 125 is V or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y (preferably A, D, H, I, N, P, T, or W);
wherein the amino acid at position 126 is L or if substituted is A, C, D, E, F, G, H, I, K, M, P, Q, R, S, T, V, W, or Y (preferably R, C, H, I, K, M, S, T, or Y) wherein the amino acid at position 127 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, F, G, H, M, P, Q, R, T, V, W, or Y) wherein the amino acid at position 128 is Q or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, S, T, V, or W (preferably N or P); wherein the amino acid at position 129 is L or if substituted is C, I, M, T, or V (preferably I, T, or V); wherein the amino acid at position 130 is K or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y(preferably A, C, E, I, L, N, R, V, or Y); wherein the amino acid at position 131 is T or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, V, W, or Y (preferably A, C, F, H, I, K, L, M, Q, R, S, V, W, or Y); wherein the amino acid at position 132 is F or if substituted is A, C, H, V, W, or Y (preferably W); wherein the amino acid at position 133 is A or if substituted is C, G, L, M, S, T, or V preferably C, S, or T); wherein the amino acid at position 134 is D or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, E, H, I, L, N, Q, R, S, T, V, Y); wherein the amino acid at position 135 is K or if substituted is A, C, F, H, I, L, M, N, Q, R, S, V, W, or Y (preferably A, H, M, N, R, S, V, W, or Y); wherein the amino acid at position 136 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, S, T, or V (preferably C, E, F, I, L, N, Q, S, T, or V); wherein the amino acid at position 137 is F or if substituted is A, C, D, E, G, H, I, L, M, N, Q, R, S, T, V, W, or Y (preferably D, E, H, L, M, N, Q, or W); wherein the amino acid at position 138 is H or if substituted is A, C, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, G, I, K, M, P, Q, R, S, or Y); wherein the amino acid at position 139 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, G, I, L, N, Q, S, T, V); wherein the amino acid at position 140 is M or if substituted is A, C, D, F, G, H, I, L, N, Q, S, T, V, W, or Y (preferably A, C, F, G, L, S, T, or V); wherein the amino acid at position 141 is E or if substituted is D, M, N, P, Q, T, or V (preferably D, N, or T);
wherein the amino acid at position 142 is D or if substituted is E, F, G, H, L, N, or Q (preferably E); wherein the amino acid at position 143 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, E, F, G, H, I, M, P, Q, T, V, W, or Y);; wherein the amino acid at position 144 is F or if substituted is C, G, H, L, M, N, W, or Y (preferably N, W, or Y); wherein the amino acid at position 145 is Y or if substituted is H, D, or F (preferably H); wherein the amino acid at position 146 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y (preferably A, C, D, F, G, H, I, K, M, N, S, or V); wherein the amino acid at position 147 is A or if substituted is C, F, G, H, I, L, M, N, Q, S, T, V, W, or Y (preferably C, S, or T); wherein the amino acid at position 148 is A or if substituted is C, D, E, F, G, H, I, L, M, N, Q, S, T, or V(preferably C, F, G, L, M, N, S, T, or V); wherein the amino acid at position 149 is L or if substituted is A, C, D, E, F, G, H, I, K, M, N, Q, R, S, T, V, W, or Y (preferably C, F, I, K, R, T, or V) wherein the amino acid at position 150 is A or if substituted is A, C, D, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably K, M, N, S, or T); wherein the amino acid at position 151 is V or if substituted is A, C, D, F, G, I, L, M, N, Q, S, or T (preferably A, I, L, or T); wherein the amino acid at position 152 is F or if substituted is C, H, I, L, M, V, W, or Y (preferably H, or W); wherein the amino acid at position 153 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably D, G, H, I, K, M, N, Q, S, or T); wherein the amino acid at position 154 is A or if substituted is C, E, F, G, I, L, M, N, Q, R, S, T, V, W, or Y (preferably C, L, Q, or V); wherein the amino acid at position 155 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably C, D, E, G, H, I, L, M, P, Q, S, T, V, W, or Y); wherein the amino acid at position 156 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, H, I, M, N, P, Q, R, S, or T); wherein the amino acid at position 157 is A or if substituted is E, S, or V; wherein the amino acid at position 158 is A or if substituted is E, G, S, T, or V (preferably V);
wherein the amino acid at position 159 is A or if substituted is E, G, S, T, or V (preferably S or T); and wherein the amino acid at position 160 is G or if substituted is E, R, or V (preferably R). In some preferred embodiments, not more than 6, 5, 4, 3, 2 or 1 of positions 8, 9, 10, 12, 91, 94, 98, 102, 105, 106, 109, 112, 113, 123, 127, 128, 131, 132, 134, 135, 138, 139, 141, 142, 145, 146, and 140 are substituted. [00147] In some exemplary embodiments, amino acid residues are added at the N terminus of the protein decoys to add stability. For example, in exemplary embodiments, a PG sequence (i.e., proline-glycine) is added to the N terminus. Any of the amino acid sequence set forth in SEQ ID NOs.47-90, 104-172, 184-193, 224-239, 255-260 and 265-266 and SEQ ID NOs.91-95, 194-197, 223, and 261-263 (as provided below) can be preceded, for example, by a PG sequence, or a MPG sequence. [00148] The ACE2 protein decoys may comprise one, two, three, four, or more decoy units. In some embodiments, the ACE2 protein decoys may comprise one, two, three, or four decoy units. In some embodiments, a decoy unit comprises (i) at least two alpha helical domains, H1 and H2, (ii) an optional beta hairpin domain, H3, and (iii) at least one structural domain. In some embodiments, a decoy unit comprises (i) two alpha helical domains, H1 and H2, (ii) one beta hairpin domain, H3, and (iii) two structural domains. In exemplarly embodiments, the H1, H2, H3 and structural domains are as described herein. Nonlimiting exemplary decoy units are provided in SEQ ID NOS: 47-90, 104-172, 184-193, 224-239, and 255-260. In some aspects, an ACE2 protein decoy is multivalent (e.g. bivalent, trivalent, tetravelent), which means it comprises at least two decoy units. In some embodiments, the ACE2 protein decoy comprises two, three, four, or more amino acid sequences independently selected from SEQ ID NOS: 47-90, 104-172, 184-193, 224-239, 255-260, or 265-266. In some embodiments, the ACE2 protein decoy comprises multiple copies of the same decoy unit. In some embodiments, the ACE2 protein decoy comprises 2 to 4 copies of the same or a different decoy unit. [00149] In some aspects, a the C terminus of a first decoy unit is linked to the N terminus of a second decoy unit. Linkage can be via a chemical or enzymatic crosslinking (e.g. bismaleimide). The two or more decoy units may directly abut each other in the translational fusion or may be linked by a polypeptide linker suitable for the intended purpose. Exemplary such linkers include, but are not limited, to those disclosed in WO2016178905, WO2018153865, and WO 2018170179. In other embodiments, suitable linkers include, but are not limited to peptide linkers, such as, for example, GGGGG (SEQ
ID NO: 96), GSGGG (SEQ ID NO: 97), GGGGGG (SEQ ID NO: 98), GGSGGG (SEQ ID NO: 99), GGSGGSGGGSGGSGSG (SEQ ID NO: 100), GSGGSGGGSGGSGSG (SEQ ID NO: 101), GGSGGSGGGSGGSGGGGSGGSGGGSGGGGS (SEQ ID NO: 102), GGGGSGGSGSGGSGGGS (SEQ ID NO: 175), [GGGGX]n (SEQ ID NO: 103), where X is Q, E or S and n is 2-5, and GGGSGGSGSGGSGGGS (SEQ ID NO: 264). In some embodiments, an amino acid linker between decoy units is from 1-100, from 1-80, from 1- 60, from 1-50, from 1-40, from 1-30, or from 1-20 amino acids in length. [00150] In some aspects, two or more ACE2 protein decoys are different. Any of the ACE2 protein decoys provided herein can be linked together for use in the present invention. [00151] Exemplary ACE2 protein decoys include those comprising one or more of CTC- 640, CTC-693, CTC-694, CTC-695, CTC-702, CTC-705, or CTC-726. In some aspects, an ACE2 protein decoy comprises (i) CTC-640 and/or CTC-693; (ii) CTC-640 and/or CTC- 694; (iii) CTC-640 and/or CTC-694. In some aspects, an ACE2 protein decoy of the present comprises a multivalent, serially duplicated version of CTC-640; a multivalent ACE2 protein decoy wherein each individual decoy unit comprises a sequence having at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, or 99% identity to the amino acid sequence set forth for CTC-640; a multivalent, serially duplicated version of CTC-702; a multivalent ACE2 protein decoy wherein each individual decoy unit comprises a sequence having at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, or 99% identity to the amino acid sequence set forth for CTC-702; a multivalent, serially duplicated version of CTC-705; a multivalent ACE2 protein decoy wherein each individual decoy unit comprises a sequence having at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, or 99% identity to the amino acid sequence set forth for CTC-705; a multivalent, serially duplicated version of CTC-726; or a multivalent ACE2 protein decoy wherein each individual decoy unit comprises a sequence having at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, or 99% identity to the amino acid sequence set forth for CTC-726. [00152] It will be appreciated by the skilled artisan that, in addition to the linkers, additional amino acid residues may be added to the N or C terminus of each individual decoy unit prior to being fused together to create multivalent ACE2 protein decoy, e.g, bivalent, trivalent, tetravalent, etc. In addition, the multivalent ACE2 protein decoys can be cyclized. Methods for cyclizing proteins are known in the art, see, for example, Wood et al., Journal of Biological Chemistry, 289:21; 14512-14519, 2014.
[00153] Exemplary multivalent ACE2 protein decoys include those comprising a sequence at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS: 91-95, 194-197, 223, or 261-263: Table 3
DOMAIN ORDER [00154] As a result of the proteins of the present invention being de novo synthesized proteins, there is a great deal of variability permitted both in the amino acid residues but also in the ordering of the domains (e.g. H1, H2, H3, D1 and D2). The domains can be
linked together via amino acid linkers in varying order and still be properly folded and presented for binding to the coronavirus spike protein. As noted, the order of domains in CTC-445 and many of the CTC-445 variants provided herein is H3-D1-D2-H2-H1. The skilled artisan will understand, however, that the domains can be re-ordered and still result in active proteins. In some embodiments, re-ordering the domains is referred to as circular permutation and the amino acid sequence of a decoy unit is shifted in order to create a new N- and C-terminus. In some such aspects, re-ordering results in a new order of domains that is H1-H3-D1-D2-H2. All of the CTC-445 variants described herein having an order of domains of H3-D1-D2-H2-H1 can be circular permutated to create a new domain order of H1-H3-D1-D2-H2. Due to the shifting of the H1 domain, an amino acid linker is added in between the H1 and H3 domains, creating a variable loop region between domains H1 and H3. CTC-705 is a circular permutated version of CTC-640. CTC-726 and CTC-786 are two circular permutated versions of CTC-702 that differ with respect to the linker between domains H1 and H3. Circular permutating CTC-640 and CTC-726 in such a manner repositions the termini of the ACE2 protein decoy to allow for different orientation of the multivalent subunits. Additional ordering of domains includes, for example, H2-H1-H3- D1-D2, D2-H2-H1-H3-D1, and D1-D2-H2-H1-H3. EXEMPLARY BIOLOGICAL CHARACTERISTICS OF THE ACE2 PROTEIN DECOYS [00155] In general, the proteins of the present invention function by binding to coronavirus spike protein, in particular, coronavirus spike protein from a coronavirus that gains entry into host cells via ACE2 as its receptor (i.e., coronavirus ACE2-binding spike protein). In certain embodiments, the de novo proteins of the present invention bind to one or more amino acids in the receptor binding domain (RBD) of the spike protein SARS-COV-2. For example, the present invention includes de novo proteins that bind SARS-CoV-2 spike protein with a Kd of less than 100 nM, less than 50 nm, less than 20 nM as measured by biolayer interferometry or yeast display, e.g., using the assay formats as defined in the examples. In certain embodiments, the de novo proteins bind SARS-CoV-S with a Kd of less than about 20 nM, less than about 15 nM, less than about 5 nM as measured by biolayer interferometry or yeast display, e.g., using the assay formats as defined herein, or a substantially similar assay. [00156] The present invention also includes de novo ACE2 protein decoys of the present invention that block more than 50%, more than 60%, more than 70% more than 80% or
more than 90% of SARS-CoV-2-S binding to ACE2 as determined using assays known in the art. [00157] The present invention also includes de novo proteins that neutralize or inhibit the infectivity of a coronavirus (e.g. SARS-CoV-2) for its host cells. In certain embodiments, the proteins neutralize the infectivity of SARS-CoV-2-like pseudoparticles. In some embodiments, the proteins inhibit more than 50%, more than 60%, more than 70% more than 80% or more than 90% binding of SARS-CoV-2 on human host cells in an optimized virus-like pseudo-particle (VLP) neutralization assay, e.g., as shown in the examples, or a substantially similar assay. [00158] The present invention includes de novo ACE2 protein decoys that bind to the receptor binding domain of SARS-CoV-2 spike protein or to a fragment of the domain. [00159] The ACE2 protein decoys of the present invention may possess one or more of the aforementioned biological characteristics, or any combinations thereof. [00160] Other biological characteristics of the proteins of the present invention will be evident to a person of ordinary skill in the art from a review of the present disclosure including the examples provided herein. NUCLEIC ACIDS, EXPRESSION VECTORS, HOST CELLS [00161] In a further aspect, the present invention provides nucleic acids, including isolated nucleic acids, encoding a protein or peptide of the present invention. The isolated nucleic acid sequence may comprise RNA or DNA. Such isolated nucleic acid sequences may comprise additional sequences useful for promoting expression and/or purification of the encoded protein, including but not limited to polyA sequences, modified Kozak sequences, and sequences encoding epitope tags, export signals, and secretory signals, nuclear localization signals, and plasma membrane localization signals. It will be apparent to those of skill in the art, based on the teachings herein, what nucleic acid sequences will encode the polypeptides of the invention. [00162] In another aspect, the present invention provides recombinant expression vectors comprising the isolated nucleic acid of any aspect of the invention operatively linked to a suitable control sequence. "Recombinant expression vector" includes vectors that operatively link a nucleic acid coding region or gene to any control sequences capable of effecting expression of the gene product. “Control sequences” operably linked to the nucleic acid sequences of the invention are nucleic acid sequences capable of effecting the expression of the nucleic acid molecules. The control sequences need not be contiguous
with the nucleic acid sequences, so long as they function to direct the expression thereof. Thus, for example, intervening untranslated yet transcribed sequences can be present between a promoter sequence and the nucleic acid sequences and the promoter sequence can still be considered "operably linked" to the coding sequence. Other such control sequences include, but are not limited to, polyadenylation signals, termination signals, and ribosome binding sites. Such expression vectors include but are not limited to, plasmid and viral-based expression vectors. The control sequence used to drive expression of the disclosed nucleic acid sequences in a mammalian system may be constitutive (driven by any of a variety of promoters, including but not limited to, CMV, SV40, RSV, actin, EF) or inducible (driven by any of a number of inducible promoters including, but not limited to, tetracycline, ecdysone, steroid-responsive). The expression vector must be replicable in the host organisms either as an episome or by integration into host chromosomal DNA. In various embodiments, the expression vector may comprise a plasmid, viral-based vector (including but not limited to a retroviral vector or oncolytic virus), or any other suitable expression vector. In some embodiments, the expression vector can be administered in the methods of the disclosure to express the proteins in vivo for therapeutic benefit. The nucleic acids of the present invention may be administered to a subject to treat a disease described herein. [00163] In a further aspect, the present disclosure provides host cells that comprise the recombinant expression vectors disclosed herein, wherein the host cells can be either prokaryotic or eukaryotic. The cells can be transiently or stably engineered to incorporate the expression vector of the invention, using techniques including but not limited to bacterial transformations, calcium phosphate co-precipitation, electroporation, or liposome mediated-, DEAE dextran mediated-, polycationic mediated-, or viral mediated transfection. (See, for example, Molecular Cloning: A Laboratory Manual (Sambrook, et al., 1989, Cold Spring Harbor Laboratory Press); Culture of Animal Cells: A Manual of Basic Technique, 2nd Ed. (R.I. Freshney.1987. Liss, Inc. New York, NY)). A method of producing a protein according to the invention is an additional part of the invention. The method comprises the steps of (a) culturing a host according to this aspect of the invention under conditions conducive to the expression of the protein, and (b) optionally, recovering the expressed protein. The expressed protein can be recovered from the cell free extract, but preferably they are recovered from the culture medium. [00164] In a further aspect, the present disclosure provides antibodies that selectively bind to the proteins of the disclosure. The antibodies can be polyclonal, monoclonal antibodies,
humanized antibodies, and fragments thereof, and can be made using techniques known to those of skill in the art. As used herein, “selectively bind” means preferential binding of the antibody to the protein of the disclosure, as opposed to one or more other biological molecules, structures, cells, tissues, etc., as is well understood by those of skill in the art. FUSION PROTEINS AND CONJUGATES [00165] Exemplary proteins of the present invention can be prepared as fusion or chimeric polypeptides that include de novo ACE2 protein decoys of the present invention and a heterologous polypeptide. Exemplary heterologous polypeptides can increase the circulating half-life of the resultant chimeric polypeptide in vivo, and may, therefore, further enhance the properties of the proteins of the present invention. In various embodiments, the polypeptide that increases the circulating half-life may be a serum albumin, such as human serum albumin, or the Fc region of the IgG subclass of antibodies that lacks the IgG heavy chain variable region. Exemplary Fc regions can include a mutation (e.g., a mutation that inhibits complement fixation and/or Fc receptor binding) or it may be lytic, i.e., able to bind complement or to lyse cells via another mechanism, such as antibody-dependent complement lysis. The “Fc region” can be a naturally occurring or synthetic polypeptide that is homologous to the IgG C-terminal domain produced by digestion of IgG with papain. The fusion proteins can include the entire Fc region, or a smaller portion that retains the ability to extend the circulating half-life of a chimeric polypeptide of which it is a part. In addition, full-length or fragmented Fc regions can be wild-type or variants of the wild-type molecule. That is, they can contain mutations that may or may not affect the function of the polypeptides. For example, they may have effector function or may be modified as to have one or more activities associated with effector function reduced or completely eliminated. Effector function refers to those biological activities attributable to the Fc region of an immunoglobulin, which vary with the immunoglobulin isotype. Examples of effector function include, C1q binding and complement dependent cytotoxicity (CDC), Fc receptor binding, antibody-dependent cell- mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), cytokine secretion, immune complex-mediated antigen uptake by antigen presenting cells, down regulation of cell surface receptors, and B cell activation. [00166] In some exemplary embodiments, the de novo proteins of the present invention includes an IgG1, IgG2, IgG3, or IgG4 Fc region. In some exemplary embodiments, the de novo proteins include a variant IgG1, IgG2, IgG3, or IgG4 Fc region. In some aspects, the
variant Fc region lacks effector function. In some aspects, a de novo protein of the present invention is fused to the C-terminus of an Fc region (e.g., a native or variant IgG1, IgG2, IgG3, or IgG4 Fc region). In some aspects, two de novo proteins of the present invention are fused to a Fc region (e.g., at the N and C terminus). [00167] In other embodiments, the proteins of the present invention may be linked to other types of stabilization compounds to promote an increased half-life in vivo, including but not limited to attachment of one or more polyethylene glycol chains (PEGylation). [00168] In that regard, the de novo proteins can have amino acid substitutions that enable chemical conjugation with water soluble polymers (e.g., PEG) that increase circulating half- life compared to the protein alone. A “PEG” is a poly(ethylene glycol) molecule which is a water-soluble polymer of ethylene glycol. PEGs can be obtained in different sizes, and can also be obtained commercially in chemically activated forms that are derivatized with chemically reactive groups to enable covalent conjugation to proteins. Linear PEGs are produced in various molecular weights, such as PEG polymers of weight-average molecular weights of 5,000 daltons, 10,000 daltons, 20,000 daltons, 30,000 daltons, and 40,000 daltons. Branched PEG polymers have also been developed. Commonly-used activated PEG polymers are those derivatized with N-hydroxysuccinimide groups (for conjugation to primary ambines such as lysine residues and protein N-termini), with aldehyde groups (for conjugation to N-termini), and with maleimide or iodoacetamide groups (for coupling to thiols such as cysteine residues). Methods of designing moieties for conjugation to PEG are known in the art. For example, addition of polyethylene glycol (“PEG”) containing moieties may comprise attachment of a PEG group linked to maleimide group (e.g., "PEG-MAL") to a cysteine residue of the protein. Suitable examples of PEG-MAL include, for example, methoxy PEG-MAL 5 kD; methoxy PEG-MAL 20 kD; methoxy (PEG)2-MAL 40 kD; methoxy PEG(MAL)25 kD; methoxy PEG(MAL)220 kD; methoxy PEG(MAL)240 kD; or any combination thereof. [00169] With respect to the de novo proteins of the present invention, an amino acid that is not necessary for binding can be replaced by cysteine to allow for attachment of a desirable moiety. In some embodiments, the ACE2 protein decoy comprises 0-4 cysteine amino acids, or in some embodiments, comprises 0 or 1 cysteine amino acids. In some such aspects a water-soluble polymer such as a PEG molecule is linked to one or more (preferably one) of the cysteine residue. Linkage can for example via a maleimide group. Preferred placements of cysteine residues for conjugation to stability moieties are distal to the binding site so that the stability moiety doesn’t interfere with binding to the ACE2
coronovirus spike protein (e.g., in the structural domains that facilitate protein folding and binding-competent presentation of the alpha helices and beta hairpin domains to the coronavirus spike protein). Cysteine residues can be added for reasons other than conjugation to stability moieties, for example, two or more cysteine resides can be placed to allow for formation of disulfide bonds. Disulfide bonds can, in some aspects, lend additional stability to the ACE2 protein decoy. In such embodiments, the added cysteine residues need not be distal to the binding site and may be, in some aspects, at the N and C termini of the ACE2 protein decoy. Accordingly, included in the present invention are ACE2 protein decoys comprising one or more disulfide bonds. [00170] In some exemplary embodiments, a PEG group is linked to a cysteine residue present in any one of the ACE-2 protein decoys. For example, provided herein are ACE2 protein decoys having at least 60%, 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 95%, 97%, 99% or 100% identity to (i) the amino acid sequence of CTC-648 wherein the cysteine residue at position 11 is present and is linked to a PEG group; (ii) the amino acid sequence of CTC-649 wherein the cysteine residue at position 63 is present and is linked to a PEG group; (iii) the amino acid sequence of CTC-650 wherein the cysteine residue at position 74 is present and is linked to a PEG group; (iv) the amino acid sequence of CTC- 651 wherein the cysteine residue at position 11 is present and is linked to a PEG group; (v) the amino acid sequence of CTC-652 wherein the cysteine residue at position 63 is present and is linked to a PEG group; (vi) the amino acid sequence of CTC-653 wherein the cysteine residue at position 74 is present and is linked to a PEG group; (vii) the amino acid sequence of CTC-642 or CTC-645 wherein the cysteine residue at position 11 is present and is linked to a PEG group; (ix) the amino acid sequence of CTC-643 or CTC-646 wherein the cysteine residue at position 63 is present and is linked to a PEG group; (x) the amino acid sequence of CTC-647 wherein the cysteine residue at position 74 is present and is linked to a PEG group; (xi) the amino acid sequence of CTC-693 wherein the cysteine residue at position 11 is present and is linked to a PEG group; the amino acid sequence of CTC-694 wherein the cysteine residue at position 63 is present and is linked to a PEG group; or the amino acid sequence of CTC-695 wherein the cysteine residue at position 74 is present and is linked to a PEG group. Linkage can be, for example, via any methodology known in the art, including malimide groups.
[00171] Chimeric polypeptides that include a de novo protein of the present invention and a heterologous polypeptide can include those chimeric polypeptides comprising a targeting domain. The targeting domain can direct cellular localization of the de novo proteins. [00172] When a targeting domain is a polypeptide, the targeting domain can be any suitable polypeptide that binds to one or more targets of interest and can be attached or associated with a polypeptide of the present invention. In non-limiting embodiments, the targeting domain may include but is not limited to an scFv, a F(ab), a F(ab’)2, a B cell receptor (BCR), a DARPin, an affibody, a monobody, a nanobody, diabody, an antibody (including a monospecific or bispecific antibody); a cell-targeting oligopeptide including but not limited to RGD integrin-binding peptides, de novo designed binders, aptamers, a bicycle peptide, conotoxins, small molecules such as folic acid, and a virus that binds to the cell surface. The targeting domain may be covalently or non-covalently bound to the protein. [00173] In another embodiment, the targeting domain, when present, is a translational fusion with the protein. In this embodiment, the protein and the targeting domain may directly abut each other in the translational fusion or may be linked by a polypeptide linker suitable for an intended purpose. Exemplary such linkers include, but are not limited, to those disclosed in WO2016178905, WO2018153865, and WO 2018170179 (. Methods of making fusion proteins and conjugates are known in the art and not discussed herein in detail. METHODS OF TREATMENT [00174] The de novo ACE2 protein decoys of the present invention are useful for the treatment, and/or prevention of a disease or disorder or condition associated with a coronavirus that uses ACE2 as its receptor, e.g., SARS-CoV or SARS-CoV-2 and/or for ameliorating at least one symptom associated with such disease, disorder or condition. In one embodiment, a protein of the present invention may be administered at a therapeutic dose to a patient with a SARS-CoV or SARS-CoV-2 infection. [00175] In certain embodiments, the proteins of the invention are useful to treat subjects suffering from the severe and acute respiratory infection caused by SARS-CoV or SARS- CoV-2. In some embodiments, the proteins of the invention are useful in decreasing viral titer or reducing viral load in the host. In one embodiment, the proteins of the present invention are useful in preventing or reducing inflammation in the lung of a subject with SARS-CoV or SARS-CoV-2 or another coronavirus that uses ACE2 as its entry into host cells. In one embodiment, the proteins of the present invention are useful in preventing or
reducing interstitial, peribronchiolar or perivascular inflammation, alveolar damage and pleural changes in a subject with SARS-CoV or SARS-CoV-2 or another coronavirus that uses ACE2 as its entry into host cells. [00176] One or more proteins of the present invention may be administered to relieve or prevent or decrease the severity of one or more of the symptoms or conditions of the disease or disorder. The proteins may be used to ameliorate or reduce the severity of at least one symptom of an infection from SARS-CoV or SARS-CoV-2 or another coronavirus that uses ACE2 as its entry into host cells including, but not limited to consisting of fever, cough, shortness of breath, pneumonia, diarrhea, organ failure (e.g., kidney failure, heart failure, and renal dysfunction), septic shock and death. [00177] It is also contemplated herein to use proteins of the present invention prophylactically to subjects at risk for developing a coronavirus infection. In some aspects, the subjects are immunocompromised individuals, elderly adults (more than 65 years of age), healthcare workers, persons with occupational or recreational contact with camels or bats, family members in close proximity to coronavirus patient, adults or children with contact with persons with confirmed or suspected coronavirus infection, and patients with a medical history (e.g., increased risk of pulmonary infection, heart disease or diabetes). [00178] In a further embodiment of the invention the present de novo proteins are used for the preparation of a pharmaceutical composition or medicament for treating patients suffering from a coronavirus infection. In another embodiment of the invention, the present proteins are used as adjunct therapy with any other agent or any other therapy known to those skilled in the art useful for treating or ameliorating a coronavirus infection. [00179] The de novo proteins may be combined with other therapies such an any additional therapeutic agent that may be advantageously combined with a protein of the invention. In some embodiments, the proteins of the invention may be combined with a second therapeutic agent to reduce the viral load in a patient with a coronavirus infection, or to ameliorate one or more symptoms of the infection. [00180] The de novo ACE2 protein decoys can be in any form that allows for them to be administered to a patient. For example, they can be in the form of a solid or liquid. The de novo proteins can be administered by any convenient route, for example by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.). Administration can be systemic or local. Typical routes of administration include, without limitation, oral, topical, parenteral,
sublingual, rectal, vaginal, ocular, intra-tumor, and intranasal. Parenteral administration includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. In one aspect, the de novo proteins are administered parenterally. In yet another aspect, the de novo proteins are administered intravenously or subcutaneously. In some aspects, local administration is desired as it can avoid the toxicities that may be associated with systemic exposure. Accordingly, in some preferred aspects, the de novo proteins are administered locally. In some aspects, the de novo proteins are administered locally to the respiratory tract, for example, via inhalation. Inhalation can be, for example, by aerosol inhaler or inhalable powder. [00181] The proteins of the present invention may be used in combination with an anti- inflammatory drug (e.g., corticosteroids, and non-steroidal anti-inflammatory drugs), an anti-infective drug, or an anti-viral drug. In some aspects, the proteins of the present invention may be used in combination with a drug to treat cytokine release syndrome (e.g., cytokine storm.) [00182] It is also contemplated herein to use nucleic acids of the present invention to subjects for the treatment, and/or prevention of a disease or disorder or condition associated with a coronavirus that uses ACE2 as its receptor, e.g., SARS-CoV or SARS-CoV-2 and/or for ameliorating at least one symptom associated with such disease, disorder or condition. In one embodiment, a nucleic acid of the present invention may be administered at a therapeutic dose to a patient with a SARS-CoV or SARS-CoV-2 infection PHARMACEUTICAL COMPOSITIONS [00183] Pharmaceutical compositions can be formulated so as to allow the de novo ACE2 protein decoys to be bioavailable upon administration of the composition to a patient. The de novo proteins can take the form of solutions, suspensions, emulsion, microparticles, tablets, pills, pellets, capsules, capsules containing liquids, powders, sustained-release formulations, suppositories, emulsions, aerosols, sprays, suspensions, or any other form suitable for use. Other examples of suitable pharmaceutical carriers are described in "Remington's Pharmaceutical Sciences" by E. W. Martin. It will be evident to those of ordinary skill in the art that the optimal dosage of the active ingredient(s) in the pharmaceutical composition will depend on a variety of factors. Relevant factors include, without limitation, the type of animal (e.g., human), the particular form of ACE2 protein decoys, the manner of administration, and the composition employed.
[00184] The pharmaceutically acceptable carrier or vehicle can be particulate, so that the compositions are, for example, in tablet or powder form. The carrier(s) can be liquid, with the compositions being, for example, an oral syrup or injectable liquid. In addition, the carrier(s) can be gaseous or particulate, so as to provide an aerosol composition useful in, e.g., inhalatory administration. [00185] When intended for oral administration, the de novo proteins are preferably in solid or liquid form, where semi-solid, semi-liquid, suspension and gel forms are included within the forms considered herein as either solid or liquid. As a solid composition for oral administration, the composition can be formulated into a powder, granule, compressed tablet, pill, capsule, chewing gum, wafer or the like form. Such a solid composition typically contains one or more inert diluents. In addition, one or more of the following can be present: binders such as carboxymethylcellulose, ethyl cellulose, microcrystalline cellulose, or gelatin; excipients such as starch, lactose or dextrins, disintegrating agents such as alginic acid, sodium alginate, Primogel, corn starch and the like; lubricants such as magnesium stearate or Sterotex; glidants such as colloidal silicon dioxide; sweetening agents such as sucrose or saccharin, a flavoring agent such as peppermint, methyl salicylate or orange flavoring, and a coloring agent. [00186] When the composition is in the form of a capsule, e.g., a gelatin capsule, it can contain, in addition to materials of the above type, a liquid carrier such as polyethylene glycol, cyclodextrin or a fatty oil. The composition can be in the form of a liquid, e.g., an elixir, syrup, solution, emulsion or suspension. The liquid can be useful for oral administration or for delivery by injection. When intended for oral administration, a composition can comprise one or more of a sweetening agent, preservatives, dye/colorant and flavor enhancer. In a composition for administration by injection, one or more of a surfactant, preservative, wetting agent, dispersing agent, suspending agent, buffer, stabilizer and isotonic agent can also be included. Also contemplated are delayed release capsule, including those with an enteric coating. [00187] The liquid compositions, whether they are solutions, suspensions or other like form, can also include one or more of the following: sterile diluents such as water for injection, saline solution, preferably physiological saline, Ringer's solution, isotonic sodium chloride, fixed oils such as synthetic mono or digylcerides which can serve as the solvent or suspending medium, polyethylene glycols, glycerin, cyclodextrin, propylene glycol or other solvents; antibacterial agents such as benzyl alcohol or methyl paraben; antioxidants such as ascorbic acid or sodium bisulfate; chelating agents such as ethylenediaminetetraacetic
acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. A parenteral composition can be enclosed in ampoule, a disposable syringe or a multiple-dose vial made of glass, plastic or other material. Physiological saline is an exemplary adjuvant. An injectable composition is preferably sterile. [00188] In another aspect, the present disclosure provides pharmaceutical compositions, comprising one or more proteins of the disclosure and a pharmaceutically acceptable carrier. The term “carrier” refers to a diluent, adjuvant or excipient, with which de novo protein of the present invention is administered. The pharmaceutical composition may comprise, for example, in addition to the polypeptide of the disclosure (a) a lyoprotectant; (b) a surfactant; (c) a bulking agent; (d) a tonicity adjusting agent; (e) a stabilizer; (f) a preservative and/or (g) a buffer. [00189] In some embodiments, the buffer in the pharmaceutical composition is a Tris buffer, a histidine buffer, a phosphate buffer, a citrate buffer or an acetate buffer. The pharmaceutical composition may also include a lyoprotectant, e.g. sucrose, sorbitol or trehalose. In certain embodiments, the pharmaceutical composition includes a preservative e.g. benzalkonium chloride, benzethonium, chlorohexidine, phenol, m-cresol, benzyl alcohol, methylparaben, propylparaben, chlorobutanol, o-cresol, p-cresol, chlorocresol, phenylmercuric nitrate, thimerosal, benzoic acid, and various mixtures thereof. In other embodiments, the pharmaceutical composition includes a bulking agent, like glycine. In yet other embodiments, the pharmaceutical composition includes a surfactant e.g., polysorbate- 20, polysorbate-40, polysorbate- 60, polysorbate-65, polysorbate-80 polysorbate-85, poloxamer-188, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trilaurate, sorbitan tristearate, sorbitan trioleaste, or a combination thereof. The pharmaceutical composition may also include a tonicity adjusting agent, e.g., a compound that renders the formulation substantially isotonic or isoosmotic with human blood. Exemplary tonicity adjusting agents include sucrose, sorbitol, glycine, methionine, mannitol, dextrose, inositol, sodium chloride, arginine and arginine hydrochloride. In other embodiments, the pharmaceutical composition additionally includes a stabilizer, e.g., a molecule which, when combined with a protein of interest substantially prevents or reduces chemical and/or physical instability of the protein of interest in lyophilized or liquid form. Exemplary stabilizers include sucrose, sorbitol, glycine, inositol, sodium chloride, methionine, arginine, and arginine hydrochloride.
[00190] The proteins may be the sole active agent in the pharmaceutical composition, or the composition may further comprise one or more other active agents suitable for an intended use. [00191] In order to treat disease, the proteins are provided in a therapeutically effective amount. This refers to an amount of the protein effective for treating the disease or having the desired effect. The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. Dosage regimens can be adjusted by clinicians to provide the optimum desired response (e.g., a therapeutic or prophylactic response). The compositions can be administered one from one or more times per day to one or more times per week; including once every other day. The skilled artisan will appreciate that certain factors may influence the dosage and timing required to effectively treat a subject, including but not limited to the severity of the disease or disorder, previous treatments, the general health and/or age of the subject, and other diseases present. Moreover, treatment of a subject with a therapeutically effective amount of the polypeptides can include a single treatment or, can include a series of treatments. [00192] An exemplary dosage range for the de novo ACE2 protein decoys may, for instance, be 0.1 µg/kg-100 mg/kg body weight; alternatively, it may be 0.5 µg/kg to 50 mg/kg; 1 µg/kg to 25 mg/kg, or 5 µg/kg to 10 mg/kg body weight. In some embodiments, the recommended dose could be lower than 0.1 mcg/kg, especially if administered locally. In other embodiments, the recommended dose could be based on weight/m2 (i.e. body surface area), and/or it could be administered at a fixed dose (e.g., .05-100 mg). In some aspects, the fixed dose will be 1, 3, 10 or 20 mg doses. The polypeptides can be delivered in a single bolus, or may be administered more than once (e.g., 2, 3, 4, 5, or more times) as determined by an attending physician. [00193] In some embodiments, the adminstriaton will be via intransal spray and dosing will be fixed dose. In some aspects, the fixed dose will be 0.5, 1, 2, 3, 10 or 20 mg doses. In some embodiments, dosing will be once per day or two times per day for a consecutive number of days. [00194] The following examples are provided to describe certain embodiments of the invention provided herein and are not to be construed to as limiting. ACE2 protein – SEQ ID NO:1 MSSSSWLLLS LVAVTAAQST IEEQAKTFLD KFNHEAEDLF YQSSLASWNY
NTNITEENVQ NMNNAGDKWS AFLKEQSTLA QMYPLQEIQN LTVKLQLQAL QQNGSSVLSE DKSKRLNTIL NTMSTIYSTG KVCNPDNPQE CLLLEPGLNE IMANSLDYNE RLWAWESWRS EVGKQLRPLY EEYVVLKNEM ARANHYEDYG DYWRGDYEVN GVDGYDYSRG QLIEDVEHTF EEIKPLYEHL HAYVRAKLMN AYPSYISPIG CLPAHLLGDM WGRFWTNLYS LTVPFGQKPN IDVTDAMVDQ AWDAQRIFKE AEKFFVSVGL PNMTQGFWEN SMLTDPGNVQ KAVCHPTAWD LGKGDFRILM CTKVTMDDFL TAHHEMGHIQ YDMAYAAQPF LLRNGANEGF HEAVGEIMSL SAATPKHLKS IGLLSPDFQE DNETEINFLL KQALTIVGTL PFTYMLEKWR WMVFKGEIPK DQWMKKWWEM KREIVGVVEP VPHDETYCDP ASLFHVSNDY SFIRYYTRTL YQFQFQEALC QAAKHEGPLH KCDISNSTEA GQKLFNMLRL GKSEPWTLAL ENVVGAKNMN VRPLLNYFEP LFTWLKDQNK NSFVGWSTDW SPYADQSIKV RISLKSALGD KAYEWNDNEM YLFRSSVAYA MRQYFLKVKN QMILFGEEDV RVANLKPRIS FNFFVTAPKN VSDIIPRTEV EKAIRMSRSR INDAFRLNDN SLEFLGIQPT LGPPNQPPVS IWLIVFGVVM GVIVVGIVIL IFTGIRDRKK KNKARSGENP YASIDISKGE NNPGFQNTDD VQTSF ACE2 H1 Motif - ST IEEQAKTFLD KFNHEAEDLF YQSSL ACE2 H2 motif - NMNNAGDKWS AFLKEQSTLA QMY ACE2 Beta Hairpin Motif - DLGK 1-17=signal peptide; 18-805=ACE2; 18-708=processed ACE2 SARS-CoV coronavirus spike protein – SEQ ID NO:2 signal peptide AA 1-13 Spike S1 – 14-667 Spike S2 – 668-1255 (S2 prime is 798-1255) MFIFLLFLTL TSGSDLDRCT TFDDVQAPNY TQHTSSMRGV YYPDEIFRSD TLYLTQDLFL PFYSNVTGFH TINHTFGNPV IPFKDGIYFA ATEKSNVVRG WVFGSTMNNK SQSVIIINNS TNVVIRACNF ELCDNPFFAV SKPMGTQTHT MIFDNAFNCT FEYISDAFSL DVSEKSGNFK HLREFVFKNK DGFLYVYKGY
QPIDVVRDLP SGFNTLKPIF KLPLGINITN FRAILTAFSP AQDIWGTSAA AYFVGYLKPT TFMLKYDENG TITDAVDCSQ NPLAELKCSV KSFEIDKGIY QTSNFRVVPS GDVVRFPNIT NLCPFGEVFN ATKFPSVYAW ERKKISNCVA DYSVLYNSTF FSTFKCYGVS ATKLNDLCFS NVYADSFVVK GDDVRQIAPG QTGVIADYNY KLPDDFMGCV LAWNTRNIDA TSTGNYNYKY RYLRHGKLRP FERDISNVPF SPDGKPCTPP ALNCYWPLND YGFYTTTGIG YQPYRVVVLS FELLNAPATV CGPKLSTDLI KNQCVNFNFN GLTGTGVLTP SSKRFQPFQQ FGRDVSDFTD SVRDPKTSEI LDISPCSFGG VSVITPGTNA SSEVAVLYQD VNCTDVSTAI HADQLTPAWR IYSTGNNVFQ TQAGCLIGAE HVDTSYECDI PIGAGICASY HTVSLLRSTS QKSIVAYTMS LGADSSIAYS NNTIAIPTNF SISITTEVMP VSMAKTSVDC NMYICGDSTE CANLLLQYGS FCTQLNRALS GIAAEQDRNT REVFAQVKQM YKTPTLKYFG GFNFSQILPD PLKPTKRSFI EDLLFNKVTL ADAGFMKQYG ECLGDINARD LICAQKFNGL TVLPPLLTDD MIAAYTAALV SGTATAGWTF GAGAALQIPF AMQMAYRFNG IGVTQNVLYE NQKQIANQFN KAISQIQESL TTTSTALGKL QDVVNQNAQA LNTLVKQLSS NFGAISSVLN DILSRLDKVE AEVQIDRLIT GRLQSLQTYV TQQLIRAAEI RASANLAATK MSECVLGQSK RVDFCGKGYH LMSFPQAAPH GVVFLHVTYV PSQERNFTTA PAICHEGKAY FPREGVFVFN GTSWFITQRN FFSPQIITTD NTFVSGNCDV VIGIINNTVY DPLQPELDSF KEELDKYFKN HTSPDVDLGD ISGINASVVN IQKEIDRLNE VAKNLNESLI DLQELGKYEQ YIKWPWYVWL GFIAGLIAIV MVTILLCCMT SCCSCLKGAC SCGSCCKFDE DDSEPVLKGV KLHYT SARS-CoV-2- coronavirus spike protein - GenBank: QHD43416.1 – SEQ ID NO:3 MFVFLVLLPL VSSQCVNLTT RTQLPPAYTN SFTRGVYYPD KVFRSSVLHS TQDLFLPFFS NVTWFHAIHV SGTNGTKRFD NPVLPFNDGV YFASTEKSNI IRGWIFGTTL DSKTQSLLIV NNATNVVIKV CEFQFCNDPF LGVYYHKNNK SWMESEFRVY SSANNCTFEY VSQPFLMDLE GKQGNFKNLR EFVFKNIDGY FKIYSKHTPI NLVRDLPQGF SALEPLVDLP IGINITRFQT LLALHRSYLT PGDSSSGWTA
GAAAYYVGYL QPRTFLLKYN ENGTITDAVD CALDPLSETK CTLKSFTVEK GIYQTSNFRV QPTESIVRFP NITNLCPFGE VFNATRFASV YAWNRKRISN CVADYSVLYN SASFSTFKCY GVSPTKLNDL CFTNVYADSF VIRGDEVRQI APGQTGKIAD YNYKLPDDFT GCVIAWNSNN LDSKVGGNYN YLYRLFRKSN LKPFERDIST EIYQAGSTPC NGVEGFNCYF PLQSYGFQPT NGVGYQPYRV VVLSFELLHA PATVCGPKKS TNLVKNKCVN FNFNGLTGTG VLTESNKKFL PFQQFGRDIA DTTDAVRDPQ TLEILDITPC SFGGVSVITP GTNTSNQVAV LYQDVNCTEV PVAIHADQLT PTWRVYSTGS NVFQTRAGCL IGAEHVNNSY ECDIPIGAGI CASYQTQTNS PRRARSVASQ SIIAYTMSLG AENSVAYSNN SIAIPTNFTI SVTTEILPVS MTKTSVDCTM YICGDSTECS NLLLQYGSFC TQLNRALTGI AVEQDKNTQE VFAQVKQIYK TPPIKDFGGF NFSQILPDPS KPSKRSFIED LLFNKVTLAD AGFIKQYGDC LGDIAARDLI CAQKFNGLTV LPPLLTDEMI AQYTSALLAG TITSGWTFGA GAALQIPFAM QMAYRFNGIG VTQNVLYENQ KLIANQFNSA IGKIQDSLSS TASALGKLQD VVNQNAQALN TLVKQLSSNF GAISSVLNDI LSRLDKVEAE VQIDRLITGR LQSLQTYVTQ QLIRAAEIRA SANLAATKMS ECVLGQSKRV DFCGKGYHLM SFPQSAPHGV VFLHVTYVPA QEKNFTTAPA ICHDGKAHFP REGVFVSNGT HWFVTQRNFY EPQIITTDNT FVSGNCDVVI GIVNNTVYDP LQPELDSFKE ELDKYFKNHT SPDVDLGDIS GINASVVNIQ KEIDRLNEVA KNLNESLIDL QELGKYEQYI KWPWYIWLGF IAGLIAIVMV TIMLCCMTSC CSCLKGCCSC GSCCKFDEDD SEPVLKGVKL HYT EXAMPLES Example 1 –Design of De Novo ACE2 Protein Decoy CTC-445 and variants thereof. [00195] Computation design of CTC-445 Computational design of ACE2 mimetics took place in four phases: selection of structural motifs from ACE2 to mimic, design of polypeptide backbones to support those structural motifs, design of sequences to support the generated backbones, and filtering of designs to reduce the set of designs to be tested experimentally. [00196] Selection of ACE2 structural motifs to mimic Structural motifs were obtained and computational design and analysis were performed using one or more of the following structures: 1) the crystal structure of ACE2 bound to a chimeric SARS-CoV + SARS-CoV- 2 RBD (PDB ID: 6vw1); 2) the cryo-EM structure of ACE2 bound to SARS-CoV-2 RBD (PDB ID: 6m17); or 3) the cryo-EM structure of ACE2 bound to SARS-CoV RBD (PDB ID: 6cs2). Two RBD-binding helices from ACE2 were identified and extracted from the structures; one (“H1”) spanning residues 19-53; and the other (“H2”) spanning residues 55- 84. In some designs, the beta-hairpin motif spanning residues 346-360 was also included in the set of motifs to mimic. These structural motifs were used as the starting point for backbone design. From these motifs, a set of residues to be preserved in the final sequence designs was selected: 19, 23, 24, 27, 28, 30, 31, 34, 35, 37, 38, 41, 42, 45, 61, 64, 68, 72, 75, 76, 79, 82, 83, 352, 353, 354, 355 and 357. Since these structural motifs alone are not
well-supported by other secondary structure elements from ACE2, de novo secondary structures were placed against the binding motifs. These new secondary structures provide the designed proteins with a hydrophobic core and serve to stabilize the relative position and orientation of the binding motifs in a manner that is competent for binding. The supporting structures were either computationally generated and placed by an available method (e.g. Rosetta combinatorial fragment assembly, parametric generation, etc.) or extracted and copied from existing structures. When the supporting secondary structures were parametrically generated or extracted from existing structures, the initial position and orientation of the helix was determined by visual inspection (using pymol ) and refined by a montecarlo search to identify the optimal location. [00197] Ideal fragment database construction The databases of highly ideal fragments used for the design of the backbones for the de novo mimetics were constructed with the Rosetta application “kcenters_clustering_of_fragments” using an extensive database of non- redundant (publicly available) protein structures from the RCSB protein data bank, which was comprised of 7062 PDBs for the 7-mer database. [00198] Computational design of backbones to support the ACE2 RBD binding motifs The resulting disconnected structural motifs were used as the input for the PyRosetta-based mimetic protocol which has been described previously (Silva et al., De novo design of potent and selective mimics of IL-2 and IL-15, Nature 2019, 565:186). First, the core elements (i.e., the starting motifs and supporting secondary structure) were rebuilt by identifying parametric equations of repetitive phi and psi angles (omega fixed to 180°) that result in secondary structures that recapitulated each of the target helices as close as possible, a “pitch” on the phi and psi angles was allowed every 3rd residue in order to allow the helices the possibility to have curvature. By using these parametric equations, the algorithm can vary the length of each of the core elements up to +/- 12 amino acids (compared to the input structural motifs). All length variations of the core elements were then reconnected pairwise with loops from a clustered database of highly ideal loops (fragment size of 7 amino acids; see “Ideal fragment database construction” above). To connect pairs of secondary structure elements, the mimetic building protocol aims to reconnect the idealized elements by pairs in all possible combinations. For each pair of secondary structure elements, the loop database was filtered to identify the loops that could connect the pair of secondary structure elements. The termini of the loop were superimposed to the termini of the core elements and were required to be <1.2 A RMSD from the core element termini, with each individual loop terminus required to have <1.5 A
RMSD from the corresponding individual core element terminus. Now joined by a loop, the core elements were minimized by cartesian-constrained backbone minimization. After minimization, the solutions are verified to contain highly ideal fragments (i.e. that every overlapping fragment that composes the two connected elements is also contained within the database) and that no backbone clashes with the target (context) binding partner. Successful pairwise connected core elements were then profiled using the same database of fragments in order to determine the most probable amino acids at each position (this information was encoded as metadata on each design). Next, solutions for pairs of connected secondary structures were combinatorially combined (by using graph theory connected components) to produce fully connected backbones. Since the number of solutions grows exponentially with each pair of elements, at each fragment combination step we ranked the designs to favor those with shorter interconnections between pairs of secondary structure core elements (i.e. effectively with shorter loops), and kept only the top solutions. Fully connected backbone solutions were profiled by layer (interface, core, non- core-surface, surface) in order to restrict the identities of the possible amino acids to be layer-compatible. Finally, all the information on hotspots, compatible built-fragment amino acids and layers were combined. [00199] Computational sequence design Fully profiled protein backbones were passed to RosettaScripts for flexible backbone design and filtering. The Rosetta energy functions used for sequence design was “beta.” Sequence design was performed using layer profile identified during backbone design, allowing only the most frequent 60% cumulative fraction of amino acids at each loop position. For each backbone, at least 9 sequences were designed. An ACE2 protein decoy, CTC-445, was selected to advance forward. CTC-445 : SAEIDMGKGDFREIRASEDAREAAEALAEAARAMKEALEIIREIAEKLRDSSRASEAA KRIAKAIRKAADAIAEAAKIAARAAKDEDAARNAENAARKAKEFAEEQAKLADMY AEFAKNGDKSRVREQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:47) [00200] Yeast display screening EB100 yeast were transformed with genes encoding the proteins to be displayed together with a linearized pETcon3 vector. The vector was linearized by 100-fold overdigestion by NdeI and XhoI (New England Biolabs) and then purified by gel extraction (Qiagen). The genes included 60 bases of overlap with the vector on both the 5′ and 3′ ends, such that homologous recombination would place the genes in frame between the AGA2 gene and the Myc tag on the vector. Yeast were grown in
SDCAA medium overnight to saturation before induction in SGCAA medium as previously described (Boder and Wittrup, “Yeast Surface Display for Screening Combinatorial Polypeptide Libraries.” Nature Biotechnology 199715(6): 553-557.). After induction for 12–16 h, cells were washed in chilled display buffer (50 mM NaPO4 pH 7.4, 150 mM NaCl, 1% BSA) and incubated with 200 nM of 2019-nCoV Spike/RBD Protein–Fc Tag receptor (Sino Biological; residues Arg319-Phe541) while being agitated at 4°C. After approximately 30 min, cells were washed again in a chilled buffer and then incubated on ice for 5 min with a FITC-conjugated anti-Myc antibody (1 μl per 3 x 106 cells) and PE anti human IgG Fc (5 μl per 3 x 106 cells). Yeast were then washed and counted by flow cytometry (guava easyCyte™ HT System) or sorted by fluorescence-activated cell sorting (FACS) (Sony SH800). [00201] Variant Design For CTC-613-636, a set of CTC-445 mutations and combinations of mutations were chosen based on visual inspection of the design model and structural alignments to human ACE2. For CTC-637 to CTC-653, protease-stable sequences based on CTC-445 which bind to SARS-CoV-2 at 200 pM were identified by yeast display of an error prone PCR DNA library. From the pool of selected sequences, a set of mutations were identified and the mutations were rationally combined into a set of CTC-445 variants.^ [00202] Recombinant protein expression Protein sequences were synthesized (IDT) and cloned into pET-29b(+) E. coli plasmid expression vectors (both with and without C- terminal 6- His tag). To aid in protein quantification, the expressed sequence for each construct contained a C-terminal GSGWGSG sequence. Plasmids containing the genes of two clones of an ACE2 protein decoy, one non-expressing negative control and a positive control protein were transformed into chemically competent E. coli Lemo21 cells (NEB). Protein expression was then induced with 1 mM of isopropyl β -d-thiogalactopyranoside (IPTG) at 37 °C. After 4 h expression, samples were collected and run on SDS-PAGE gel along with a PageRuler Plus Prestained Protein Ladder. CTC-445 ran as its expected molecular weight. (data not shown) [00203] The amino acid sequences for the variants are the same as that of CTC-445 except for the noted substitution(s). Select variants with cysteine residues were PEGylated. Briefly, proteins were purified in imidazole buffer and buffer exchanged with Centripep (10K MWCO) into PBS at pH 7.4. TCEP was added to 1 mg of sample at a 10x molar excess. Incubation was at 37 degrees Celsius for 30 minutes. Maleimide-PEG (20K linker and 40K branched) was dissolved in PBS and added to the sample at a 10x fold excess and incubated for 12 hours. Unreacted maleimides were removed and purification was via SEC.
Table 4
^ Most of these proteins include a PG motif at the N-terminus of the protein (and each decoy unit) and they may or may not include HIS tags and/or a label that allows for detection of protein by absorbance at 280 nm (e.g., GSGWGSG, SEQ ID NO:248) Example 2 – Binding of CTC-445 to SARS-CoV-2 Spike Protein and Competition Assays: Yeast Display [00204] EB100 yeast were transformed and induced as described in example 1. Following induction for 12–16 h, cells expressing human ACE2 ("Data 1") or Neoleukin CTC-445 ("Data 2") were washed in chilled display buffer (50 mM NaPO4 pH 7.4, 150 mM NaCl, 1% BSA) and incubated with 0-80 nM of 2019-nCoV Spike/RBD Protein – mFc Tag receptor (Sino Biological; residues Arg319-Phe541) while being agitated at 4°C. After approximately 30 min, cells were washed again in a chilled buffer and then incubated on ice for 5 min with a FITC-conjugated anti-Myc antibody (1 μl per 3 x 106 cells) and PE anti mouse IgG Fc (5 μl per 3 x 106 cells). Yeast were then washed and counted by flow cytometry (guava easyCyte™ HT System). Next, cells expressing human ACE2 and the test ACE2 protein decoy ("Data 5") were incubated with 9 nM 2019-nCoV Spike/RBD protein- Fc Tag receptor and 0-750 nM soluble human ACE2. Figure 2A-F show binding of a positive, negative control, and CTC-445 to SARS-CoV-2 Spike Protein via yeast display and 3A-D show that control human ACE2 and de novo protein CTC-445 were able to bind to 2019-nCoV Spike/RBD Protein and compete for binding with soluble ACE2.^ Example 3 – Characterization of De Novo ACE2 Protein Decoys [00205] CTC-445 variants were characterized for expression levels (0-5), solubility (0-5) and binding affinity via biolayer interferometry (0-5). Propensity for aggregation indicates whether large molecular weight aggregates or oligomers were present during size exclusion
chromatography, and the fraction of non-moneric protein is measured by comparing peak areas for monomeric and oligomeric species by analytical size exclusion chromatography. [00206] Size exclusion chromatography with multi-angle light scattering (SEC-MALS). SEC-MALS assays were performed using a 1260 infinity II LC HPLC system (Agilent Technologies) with a Superdex 7510/300 size exclusion column (GE Healthcare), coupled to an inline static light scattering instrument (MiniDawn, Wyatt Technology) and differential refractive index (Optilab rEX, Wyatt Technology) and UV detection systems. Protein samples were prepared in a PBS buffer at concentrations ranging from 2 to 4 mg/mL and filtered with 0.22 µm syringe filters; 100 μL of the samples were injected and run at a flow rate of 0.5 mL/min. Data were analyzed using the software ASTRA 7 (Wyatt Technologies). SEC-MALS demonstrated that CTC-445 variants, CTC-632, 633, 634, 642, 643, and 644 were mostly aggregated or oligomeric and CTC-635, 636, 637, 639, 640, 641,643, 644, 646, 648, 649, 650, 651, 652, and 653 were mostly monomeric (data not shown). Data is shown in table below. [00207] Biolayer Interferometry. Octet binding assay of purified ACE2 protein decoys. Binding data were collected in an Octet RED96 (ForteBio) and processed using the instrument’s integrated software using a 1:1 binding model. SARS-CoV-2 Spike Protein (RBD domain only, mFc Tag, Sino Biological) were immobilized to Protein A sensors (ProtA, ForteBio) at 2 μg ml−1 in binding buffer (10 mM HEPES, pH 7.4, 150 mM NaCl, 3 mM EDTA, 0.05% surfactant P20, 0.5% non-fat dry milk). After baseline measurement in binding buffer alone, the binding kinetics were monitored by dipping the biosensors in wells containing defined concentrations of the designed protein (2.4-200 nM) (association) and then dipping the sensors back into baseline wells (dissociation). In Table 5 below, a value of one (1) indicates binding similar to CTC-445; a value above 1 indicates tighter binding than CTC-445; a value of less than 1 indicates weaker binding than CTC-445; a value of 4 or over indicates very tight binding. A notation of N.D. indicates testing on a binding screen but the assay did not work as intended and led to inconclusive results. It is believed that the proteins may have been aggregated. Figures 4, 5A-H, 6A-H, and 7A-H, show the binding of CTC-445 and select CTC-445 variants to SARS-CoV-2 Spike Protein by Octet. Table 5
Example 4 – Binding kinetics and stability of de novo protein decoys CTC-445, CTC-445.2 and CTC-445.2d [00208] The thermal stability of CTC-445 and select variants was measured using circular dichroism. Far-ultraviolet circular dichroism measurements were carried out with an CHIRASCAN spectrometer V100 (Applied Photophysics) in PBS buffer (pH 7.4) in a 0.1 mm path-length cuvette with protein concentration of 0.2 mg ml−1 (unless otherwise mentioned in the text). Temperature melts were obtained from 20 to 95 °C and monitored absorption signal at 222 nm (steps of 0.5 °C per min, 30 s of equilibration by step). Wavelength scans (195–250 nm) were collected at 20 °C, 95 °C, and again at 20 °C after refolding (roughly 5 min). Melting temperature (Tm) values were calculated from the fitting of the thermal melts to the following equation:
Where fD is the fraction of the protein in the unfolded state, ^HvH is the enthalpy change associated to the unfolding process, yN and mN represent the signal of the native state and its dependence with the temperature, yD and mD represent the signal of the unfolded state and is dependence with the temperature and R is the gas constant. Thermally induced melting of CTC-445, CTC-445.2 or CTC-445.2d fused to a C-terminal thrombin site and 6x His tag were followed by its circular dichroism signal at 208 nm over a temperature range from 20°C to 95°C (heating rate 2°C/min). Figure 8 shows the results for CTC-445 (8A), CTC-445.2 (8B) and CTC-445.2d (8C). The inset shows far UV wavelength spectra of CTC-445.2 at 20 °C, after heating to 95-99 °C (dashed) and after cooling the heated sample to 20 °C. Complete ellipticity-spectra recovery (full reversibility) upon cooling was observed. [00209] Serial thermal ramping protein stability. Serial thermal ramping assays were performed in order to test the unfolding reversibility (thermal recovery) of CTC-445, CTC- 445.2, CTC-445.2d and hACE2 (Sino Biological); to this end, the UNCLE platform (Unchained Labs) was used.8.8 μL of CTC-445, CTC-445.2 and CTC-445.2d at 0.5 mg/mL were loaded in capillary cuvettes and fluorescence spectra (~300-400 nm) were measured for each sample while temperature was increased and decreased repeatedly. Temperature ramps were performed in the next order: 20 °C to 35 °C, 20 °C to 50 °C, 20 °C to 65°C, 20 °C to 80 °C, 20 °C to 95 °C, 20 °C to 80 °C, 20 °C to 65 °C, 20 °C to 50 °C and 20 °C to 35 °C. All samples were in PBS buffer pH 7.4. The barycentric mean (BCM) was calculated for each fluorescence spectrum using the UNCLE analysis program (Unchained Labs). The same value of BCM was observed before and after repeated cycles of heating and cooling for the three proteins (Figure 9A-C). [00210] Octet binding assays of CTC-445, CTC-445.2 (left) and CTC-445.2d (right) against immobilized SARS-CoV-2 S RBD are shown in Figure 10. Biotinylated and His-tagged SARS-CoV-2 S RBD was immobilized to Anti-Penta-HIS (HIS1K, ForteBio) and incubated with varying concentrations of ACE2 decoys. Binding kinetics were monitored by dipping the biosensors in wells containing defined concentrations (4.7-300 nM) of CTC-445, CTC- 445.2, CTC-445.2d (association) and then dipping the sensors back into baseline wells (dissociation). For CTC-445 and CTC-445.2, the results were globally fit using a 1:1 binding model (Kd=646 and 25 nM, kon=8.6 x104 and 4.5 x 105M-1s-1, koff =5.5 x 10-2 and 1.1 x 10-2 s-1). For CTC-445.2d, the results were globally fit using a 2:1 binding model (K d ≤ 7.0 nM, kon =3.0 x 105 M-1s-1, koff=≤2.0 x 10-3 s-1). The insets show steady-state binding of the normalized response at each concentration.
Example 5 – CTC-445 inhibits SARS-CoV-2 Spike Protein RBD binding to human ACE2 [00211] SARS-CoV2 S Protein RBD was coated at 0.5 µg/mL (100 µL/well) in flat, clear bottom, high binding polystyrene 96-well plate (Thermo, Cat#15041) overnight at 4C. On the following day, assay plate was washed 3X with 0.05% Tween-PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hour at 37C. During blocking incubation, three-fold 7-point serial dilution of each test article was prepared starting at 20 µ M (2X final) for CTC-445 and at 360 nM (2X final) for positive control inhibitor (Acro). For all test articles, a ten-fold dilution was prepared for the last concentration rather than three-fold. In addition, a dose response of biotin-hACE2 was prepared by performing a two-fold serial dilution of biotin-hACE2 starting at 0.3 µ g/mL (3.44nM). From the 0.3 µg/mL biotin- hACE2, a constant concentration of 0.06 µg/mL (2X final) was prepared to be used for inhibition by test articles. After blocking, assay plate was washed (3X) and each test article dilution was added to plate at 50 µL/well followed by 50 µL/well of biotin-hACE2 (0.03 µg/mL final). Incubation of test articles with biotin-hACE2 was performed for 1 hour at 37C. Afterwards, the plate was washed (3X) followed by incubation of 0.1 µg/mL (100 µL/well) streptavidin-HRP for 1 hour at 37C. The plate was washed (3X) a final time before addition of 100 µL/well TMB (abCam, Cat#171524). TMB was incubated for 7 minutes and reaction was stopped with addition of 50 µL/well 1M HCl. Mean absorbance in each well was measured from 4 spots at 450 nm. The IC50 results are shown in Table 6 below: Table 6
Example 6 – Select CTC-445 variants inhibit SARS-CoV-2 Spike Protein RBD binding to human ACE2 [00212] SARS-CoV2 S Protein RBD was coated at 0.5 ug/mL (100ul/well) in flat, clear bottom, high binding polystyrene 96-well plate (Thermo, Cat#15041) overnight at 4C. On
the following day, assay plate was washed 3X with 0.05% Tween-PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hours at 37C. Three-fold 6-point serial dilution of each test article was prepared starting at 4uM (2X final) for CTC-445 variants shown in Table 7 below and at 360nM (2X final) for positive control inhibitor (Acro). For all test articles, a ten-fold dilution was prepared for the last two concentrations rather than three- fold. In addition, a dose response of biotin-hACE2 was prepared by performing a three-fold serial dilution of biotin-hACE2 starting at 0.1 µg/mL (1.15nM). From the 0.1 µg/mL biotin- hACE2, a constant concentration of 0.066 µg/mL (2X final) was prepared to be used for inhibition by test articles. After blocking, assay plate was washed (3X) and each test article dilution was added to plate at 30 ul/well (in duplicate wells) followed by 30ul/well of biotin-hACE2 (0.033 µg/mL final). Incubation of test articles with biotin-hACE2 was performed for 1 hour at 37 C. Afterwards, plate was washed (3X) followed by incubation of 0.1 µg/mL (100 ul/well) streptavidin-HRP for 1 hour at 37C. Plate was washed (3X) a final time before addition of 100ul/well TMB (abCam, Cat#171524). TMB was incubated for 7 minutes and reaction was stopped with addition of 50ul/well 1M HCl or equivalent. Mean absorbance in each well was measured from 4 spots at 450nm. The IC50 results are shown in Table 7 below: Table 7
Example 7 – Select PEGylated and non-PEGylated CTC-445 variants inhibit SARS-CoV-2 Spike Protein RBD binding to human ACE2 [00213] SARS-CoV2 S Protein RBD was coated at 0.5 µg/mL (100ul/well) in flat, clear bottom, high binding polystyrene 96-well plate (Thermo, Cat#15041) overnight at 4C. On the following day, assay plate was washed 3X with 0.05% Tween-PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hours at 37C. Four-fold 6-point serial dilution of each test article was prepared starting at 4uM (2X final) for select CTC variants shown in Table 8 below and at 360nM (2X final) for positive control inhibitor (Acro). For all test articles, a ten-fold dilution was prepared for the last two concentrations rather than three-fold. In addition, a dose response of biotin-hACE2 was prepared by performing a three-fold serial dilution of biotin-hACE2 starting at 0.1 µg/mL (1.15nM). From the 0.1 µg/mL biotin-hACE2, a constant concentration of 0.066 µg/mL (2X final) was prepared to be used for inhibition by test articles. After blocking, assay plate was washed (3X) and each test article dilution was added to plate at 30 ul/well (in duplicate wells) followed by 30ul/well of biotin-hACE2 (0.033 µg/mL final). Incubation of test articles with biotin-hACE2 was performed for 1 hour at 37C. Afterwards, plate was washed (3X) followed by incubation of 0.1 µg/mL (100 ul/well) streptavidin-HRP for 1 hour at 37C. Plate was washed (3X) a final time before addition of 100ul/well TMB (abCam, Cat#171524). TMB was incubated for 7 minutes and reaction was stopped with addition of 50ul/well 1M HCl or equivalent. Mean absorbance in each well was measured from 4 spots at 450nm. (Note: starting concentration for CTC654 and CTC655
corrected after performing experiment; starting concentrations > 6uM instead of 2uM). The IC50 results are shown in Table 8 below: Table 8
Example 8 –Select CTC-445 variants inhibit SARS-CoV-2 Spike Protein RBD (and SARS- CoV-1 Spike Protein RBD) binding to human ACE2 [00214] SARS-CoV2 S protein receptor-binding domain (RBD) (Acro Biosystems, Cat#EP- 105) or SARS-CoV-1 S Protein RBD (Acro Biosystems, Cat#SPD-S52H6) was coated at 0.5 µg/mL (100ul/well) in flat, clear bottom, high binding polystyrene 96-well plate (ThermoFisher, Cat#15041) overnight at 4°C. On the following day, each assay plate was washed 3X with 0.05% Tween-PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hours at 37°C. On the following day, 12-point serial dilutions of each test article were prepared at a concentration 2-fold higher than final. For the test articles, a 3-fold serial dilution was performed starting at 4 µM. For human ACE2 (SinoBiological, Cat#10108- H08B), a 3-fold serial dilution was performed starting at 0.8 µM. In addition, a dose response of biotin-hACE2 was prepared by performing a two-fold serial dilution starting at 0.174 µg/mL (2 nM). From the 0.174 µg/mL biotin-hACE2, a constant concentration of 0.07 µg/mL (0.8 nM, 2X final) was prepared to be used for inhibition by test articles. After blocking, each assay plate was washed (3X) and each test article dilution was added to plate at 50 µL/well (single replicate well per concentration) followed by 50 µL/well of biotin- hACE2 (0.035 µg/mL final). Incubation of test articles with 0.4 nM biotin-hACE2 was performed for 1 hour at 37°C. Afterwards, each assay plate was washed (3X) followed by incubation of 0.1 µg/mL (100 µL/well) streptavidin-HRP for 1 hour at 37°C. Finally, each plate was washed (3X) before addition of 100 µL/well TMB (abCam, Cat#171524). TMB was incubated for 7-8 minutes and reaction was stopped with addition of 50 µL/well TMB Stop Solution (abCam, Cat# ab171529). Mean absorbance in each well was measured from 4 spots at 450nm. [00215] As shown in Table 9, all of the tested constructs inhibited SARS-CoV-2 spike protein binding to human ACE2. CTC654 also inhibited SARS-CoV-1 spike protein binding to human ACE2. Table 9: Test article inhibition of spike protein binding to ACE2
ND = not detectable in this assay Example 9 –CTC-445 variants inhibit SARS-CoV-2 Spike Protein RBD binding to human ACE2 [00216] Additional CTC-445 variants were assayed for inhibition of SARS-Cov-2 spike protein binding to human ACE2, substantially as described above. As shown in Table 10A, tested constructs inhibited SARS-Cov-2 spike protein binding to human ACE2 with an IC50 of less than 30 nM, and in most instances, less than 15 nM. See also Figure 19C for CTC- 708. Table 10A: Inhibition of spike protein binding to ACE2
[00217] Additional protein decoys were assayed for inhibition of SARS-Cov-2 spike protein binding to human ACE2 as follows:
[00218] SARS-CoV-2 S protein (D614G), His Tag, Super stable (Acro Biosystems, Cat#SPD-C52H3) was coated at 0.5 µg/mL (50ul/well) in flat, white bottom, high binding polystyrene 96-well plate (LumiNunc MaxiSorp Thermo Scientific, Cat#437796) overnight at 4°C. On the following day, each assay plate was washed 4X with 0.05% Tween-PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hours at 21°C on a shaker set to 600rpm. Twelve-point serial dilutions of each test article were prepared at a concentration 2-fold higher than final. For the test articles, a two-fold serial dilution was performed starting at 220 nM and ending at 0.107 nM. In addition, a dose response of biotin-hACE2 was prepared by performing a two-fold serial dilution starting at 600 ng/mL (68.81 nM, 2X final) and ending at 0.585 ng/ml (6.71 pM). From the 600 ng/mL biotin-hACE2, a constant concentration of 80 ng/mL (0.92 nM, 2X final) was prepared to be used for inhibition by each test article dilution. Each test article dilution was added to a U-bottom polystyrene plate at 90 µL/well followed by 90 µL/well of biotin-hACE2 (0.46 nM final) and mixed well. The biotin-hACE2 dose response was mixed with equal volumes of assay buffer. After blocking, each assay plate was washed (4X) and test article dilutions were added to plate in duplicate wells at 50 µL/well. Incubation of test articles with 0.46 nM biotin-hACE2 was performed for 1 hour at 21°C on a shaker set to 600rpm. Afterwards, each assay plate was washed (4X) followed by incubation of streptavidin-HRP (R&D Systems, DY998), which was prepared at a 1:1000 dilution from stock, for 1 hour at 21°C. Finally, each plate was washed (4X) before addition of 70 µL/well LuminataForte ELISA HRP chemiluminescent substrate premixed with equal volumes of luminol and peroxide solutions (EMD Millipore, Cat# ELLUF0100). Substrate was incubated for 20-30 minutes on a shaker set to 600rpm. The average luminescence in each well was measured from 4 spots at 450nm on a Tecan Infinite M1000 microplate reader. The half maximal inhibitory concentration (IC50) of each test article was determined using a four-parameter logistic (4PL) regression model with 1/Y2 weighting in GraphPad Prism software. Table 10B:
[00219] The protein decoys were expressed and purified and tested for binding via Octet as described herein. The results are show in Table 10C: Table 10C
[00220] In order to determine an optimal amino acid linker length between ACE2 protein decoy units in a bivalent ACE-2 protein decoy comprising a serially duplicated version of CTC-726, a 10 amino acid, 20 amino acid, 30 amino acid, 50 amino acid and 60 amino acid GS linker was used to link the 2 decoy units. IC50s were determined as provided above. The protein decoys were expressed and purified and tested for binding via Octet as described herein and were determined to have an estimated Kd of ~ 1 nM. Table 10D
Example 10 – Potency of CTC-445 variants vs. molecular weight. [00221] IC50 values for CTC-445 variants for binding to SARS-CoV-2 S/RBD were measured by ELISA in the presence of 0.033 nM biotinylated soluble hACE2. hACE2 bound to RBD was quantified by treatment with streptavidin-HRP and measurement of absorbance at 450 nm. SARS-CoV2 S Protein RBD (Acro, Cat#EP-105) was coated at 0.5 µg/mL (100 µL/well) in flat, clear bottom, high binding polystyrene 96-well plate (Thermo, Cat#15041) overnight at 4°C. On the following day, each assay plate was washed 3X with 0.05% Tween- PBS and blocked with 2% BSA/0.05%Tween-PBS for 1-1.5 hours at 37°C. On the following day, 11-point four-fold serial dilutions of each test article were prepared starting at 2 µM (2X final). In addition, a dose response of biotin-hACE2 was prepared by performing a two-fold serial dilution starting at 0.174 µg/mL (2 nM). From the 0.174 µg/mL biotin-hACE2, a constant concentration of 0.07 µg/mL (0.8 nM, 2X final) was prepared to be used for inhibition by test articles. After blocking, each assay plate was washed (3X) and each test article dilution was added to the plate at 50 µL/well (single replicate well per concentration) followed by 50 µL/well of biotin-hACE2 (0.035 µg/mL final). Incubation of test articles with 0.4 nM biotin-hACE2 was performed for 1 hour at 37°C. Afterwards, each assay plate was washed (3X) followed by incubation of 0.1 µg/mL (100 µL/well) streptavidin-HRP for 1 hour at 37°C. Lastly, each plate was washed (3X) before addition of 100 µl/well TMB (abCam, Cat#171524). TMB was incubated for 7-8 minutes and reaction was stopped with addition of 50 µL/well TMB Stop Solution (abCam, Cat# ab171529). Mean absorbance in each well was measured from 4 spots at 450 nm. The results are shown in Figure 11. Example 11 - VSV-luc pseudovirus neutralization [00222] Neutralization activity was determined using a non-replicative VSV pseudovirus with a firefly luciferase gene and expressing the spike protein from Wuhan-1 SARS-CoV-2 isolate (GenBank: QHD43416.1) Neutralization assays were performed with either SARS- CoV-2 / VSV-Luc (expressing the full ectodomain of the SARS-CoV-2 spike protein on the surface of the pseudovirus) or VSVg / VSV-Luc (expressing VSVg). Thirty thousand 293T- ACE2 cells were seeded the day before in white plates in the presence of hygromycin (100 μg/mL). The day of the neutralization assay, 25 μL of media containing pseudovirus was mixed with 25 μL of serial dilutions of the test-item in a different plate, and then incubated for 1 h at 37°C. Pseudovirus and test-item dilutions were performed in DMEM media containing 5% heat-inactivated fetal bovine serum (DMEM5). After the 60 m incubation, the
test-item / pseudovirus mixture was added to the 293T-ACE2 cells. Infection was allowed for 24 h. Firefly luciferase activity was monitored at 24 h using the Britelite reporter gene assay (Perkin Elmer). [00223] Test-items were evaluated in duplicates using serial 3-fold dilutions. Controls included cells infected with a VSV pseudovirus lacking spike protein (NoEnv / VSV-Luc), with pseudovirus carrying VSVg (VSVg / VSV-Luc), or uninfected cells (“mock-infected”). Pseudovirus-infected cells were incubated with test-item or vehicle alone (DMEM5). Some wells included cells challenged with pseudoviruses incubated with dilutions of plasma from a convalescent patient recovered from COVID-19 (COV+) or with a control plasma (COV-). Before collecting blood from COV+, this patient had been confirmed infected with SARS- CoV-2 by RT-PCR, and also for the presence of IgGs against SARS-CoV-2 Spike (S) evaluated with a lateral flow antibody test. COV- plasma was derived from a PCR-negative and IgG-negative for S antibodies. [00224] Average RLU values in mock-infected cells were subtracted from all values (“mock- subtracted values”). The average RLU value of infected samples in the presence of vehicle was obtained. For each data point, once the mock was subtracted, the value was divided by the average value in infected cells in the presence of vehicle alone and then multiplied by 100 to obtain the percentage infectivity value normalized to samples with vehicle alone. The average percentage infectivity for each concentration together with the standard deviation of duplicates was obtained from duplicate values generated. [00225] The 50% inhibitory concentration (IC50) was determined with GraphPad Prism. The IC50 was defined as the concentration of test-item at which the relative luminescence units (RLUs) were reduced by 50% as compared with the values in cells infected with pseudovirus in the absence of test-item). A cell viability assay (right) was run in parallel. The assays were performed using CTC-445.2 and CTC-445.2d (Figures 12A-B) and CTC-445.2d and CTC- 445.3d (Figure 21A-C). CTC 445.2, CTC-445.2d and CTC-445.3d neutralized VSV pseudovirus expressing SARS-CoV-2. No inhibition of pseudovirus infection in HEK293T cells expressing VSVg with CTC-445.2d and CTC-445.3d was observed demonstrating specificity for the RBD of SARS-CoV-2, with no discernable loss of HEK293 cell viability. Example 12 – Pharmacokinetics of the de novo decoys [00226] Eight-week-old Balb/c mice (Charles River) were anesthetized with isoflurane and 30 µL of CTC-445.2d was delivered intranasally. Mice were euthanized at indicated time
points and whole blood and lungs isolated. Whole blood was centrifuged and plasma separated from cells by pipetting into a separate tube before freezing. Lung lysate was prepared through mechanical disruption of tissue using Precellys tissue homogenizer (Bertin) followed by lysis with T-PER tissue lysis buffer (ThermoFisher) containing protease/phosphatase inhibitor cocktail (ThermoFisher). Lysates were cleared by centrifugation and frozen for analysis. Standard 96-well MSD (L15XA) plate was pre-coated with 50 µL of 0.5 µg/mL SARS-CoV-2 S Protein RBD tagless (Sino, 40592-VNAH) overnight at 4 ℃ and sealed. Dilution of capture reagent was prepared in PBS. On the following day, assay plate was washed (6X) with 0.05% Tween-PBS and blocked with 150 µL/well MSD Blocker A (5% protein-PBS solution) for a minimum of 2 hours at RT. For all incubation periods, plate shaking was performed. During blocking incubation, a standard curve was prepared by performing a 4-fold serial dilution of CTC-445.2d in either untreated lung lysate or untreated plasma at 10,000 ng/mL. Prior to addition to assay plate, each sample and standard was diluted 5-fold (MRD = 5) into assay dilution buffer (0.5% MSD Blocker A). In addition, samples were diluted 10-fold in separate wells. After blocking, assay plate was washed (6X) and 50 µL/well of each sample or standard dilution was added. Assay plate was incubated for additional 1 hour at RT with plate shaking followed by washing (6X). For detection, a 1-step detection method was used. With 1-step detection, rabbit anti-His mAb (RevMab, 31-1048-00) and SULFOTAG goat anti-rabbit IgG (H+L) pAb (MSD, R32AB) were pre-mixed at 1 µg/mL each for 1 hour prior to addition to assay plate at 50 µL/well. After last wash, 150 µL/well of MSD Gold Read Buffer was added and luminescence measured on the MSD Quickplex SQ120. Luminescence was converted to concentration based on a standard curve. Figure 13 shows bioavailability of CTC-445.2d in mice lung (top) and plasma (bottom) after intranasal administration. Protein concentration in lung lysates and blood plasma quantified using Meso Scale Discovery platform. The results show high persistence of fully functional CTC-445.2d in the lungs for more than 24 hours. Despite using an intranasal administration route, CTC-445.2d was detected in the blood raising the possibility that intranasal delivery might also allow for some degree of systemic exposure to the protein. Example 13 ACE2 functional assay. [00227] Inhibition of ACE2 enzymatic activity was performed using the ACE2 Inhibitor Screening Kit (Promocell, Heidelberg, Germany).50 µL of ACE2 enzyme solution was added to each well of a 96-well white walled plate (Corning, New York). Test samples were diluted
to 20 µM in the provided assay buffer for the highest concentration, with an 8 point 1 to 4 serial dilution. DX600 was used as the ACE2 inhibitor positive control. 10 µL of diluted samples was added to the ACE2 enzyme solution and incubated for 15 min at room temperature. 40 µL of ACE2 substrate mix was then added to each well. After 15 min, fluorescence was measured in an Infinite M1000 plate reader (Tecan Männedorf, Switzerland) with 320 nm excitation and 420 emission filters. Fluorescence values were normalized using negative controls. Figure 14 shows ACE2 functional activity as measured by enzymatic release of a free fluorophore from Mca-APK(DNP) substrate. ACE2 inhibition was shown using DX600 peptide as a positive control. This assay indicates that the de novo designed proteins do not significantly affect the functional activity of ACE2. Example 14 SARS-1 binding. [00228] Binding kinetics of CTC-445.2 and CTC-445.2d to SARS-CoV-1 RBD was measured by Octet as described herein. CTC-445.2 (left) and CTC-445.2d (right) were incubated with SARS-CoV-1 S RBD immobilized to Anti-Penta_HIS sensors and incubated with varying concentrations of CTC-445.2 (123-10000 nM; left) and CTC-445.2d (82-6667 nM; right). The results were globally fit as described above for CTC-445.2 (Kd=3864 nM, kon=1.0x105 M-1s-1, koff=3.9x10-1 s-1) and CTC-445.2d SARS-CoV-1 S RBD (Kd=1280 nM, kon=3.7 x 105 M-1s-1, koff=4.7x10-1 s-1). See Figure 15 and Table 11. Table 11
*ND – This value could not be determined in this assay Example 15 – Kinetics of binding for CTC-445.2 to SARS-CoV-2 RBD mutants. [00229] Five SARS-CoV-2 RBD mutants were immobilized via Anti-Penta-His sensors, and CTC-445.2 was titrated in solution. Data was globally fit to a 1:1 model for each RBD mutant. Figure 16 demonstrates that CTC-445.2 binds to the mutants. Example 16 – Cytoprotection Assay [00230] The test compounds in PBS were prepared at eight concentrations in MEM solution with 50 µg/mL gentamicin and 2% FBS. Test materials CTC-640 and CTC-641 were evaluated using a high test concentration of 50 µM and seven serial three-fold dilutions. CTC-655 was evaluated using a high test concentration of 10 µM and seven serial three-fold dilutions. The remaining test articles were evaluated using a high test concentration of 20 µM and seven serial three-fold dilutions. One hundred microliters of each concentration were added in triplicate wells for efficacy and in duplicate wells for cytotoxicity. Each dilution was added to 5 wells of a 96-well plate with 80-100% confluent Vero76 cells (3 x 104 cells per well) and incubated at 37°C/5% CO2 for 2 hours. SARS-CoV-2 virus (strain USA-WA1/2020) was prepared to achieve the lowest possible multiplicity of infection (MOI; 0.002) that would yield >80% cytopathic effect (CPE) at four days. Three wells of each dilution were infected with virus and two wells remained uninfected as toxicity controls. After untreated virus control wells reached maximum cytopathic effect (CPE) following four days' infection, plates were stained
with neutral red dye for approximately 2 hours, then supernatant dye was removed and the incorporated dye was extracted in 50:50 Sorensen citrate buffer/ethanol, then read on a spectrophotometer. OD values were normalized based on cell and virus controls, then the EC50 (50% effective concentration) and TC50 (50% toxic concentration) was calculated by regression analysis. Results are shown in Table 12. Table 12
Example 17 – Fusion proteins [00231] CTC-702 was fused to the C-terminus of a IgG1 Fc domain. The fusion protein was expressed and purified and tested for binding via Octet as described herein. The results were globally fit using a 1:1 binding model (Kd=0.54 nM). The fusion showed comparable binding and IC50 to CTC-654 and CTC-725. [00232] The sequence for the fusion protein is as shown in SEQ ID NO:247: MGWSCIILFLVATATGVHSEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVT CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEY KCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWE SNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSL SPGKGGSGGGSGPGSVEIDLGKGDFREIRASEDAREAAEALAEAARAMKEALEILREIAEKLR DSSRASEAAKRIAKAIRKAADAIAEAAKIAARAAKDGDAARNAENAARKAKEFAEEQAKLA DMYAELAKNGDKSSVLEQLKTFADKAFHEMEDLFYQAALAVFEAAEAAAG (SEQ ID NO:247). [00233] Next, CTC-702 was fused to the C-terminus of one IgG1 Fc domain and the N terminus of another. The fusion protein was expressed and purified and tested for binding
via Octet as described herein. The fusion showed comparable binding to the non-fused protein decoy. Example 18 – Optimization of CTC-445 using error-prone PCR and yeast display FACS [00234] Error prone PCRs (epPCR) of the gene coding for CTC-445 were performed using a GeneMorph II Random Mutagenesis Kit (Agilent), according to the standard protocol. Two separate PCR reactions were performed using 10 ng and 1ng of the CTC-445-coding gene as the initial target DNA, in order to obtain a higher and lower error rate pool. Thirty cycles of amplification were used for the PCR, with an annealing temperature of 55°C. The products of both PCRs were combined and purified by ethanol precipitation.12 µg of CTC- 445 epPCR DNA was transformed by electroporation into conditioned Saccharomyces cerevisiae strain EBY100 cells, along with 4 µg of linearized pETcon3 vector (digested with NdeI and XhoI restriction enzymes and purified by gel extraction), using the previously described protocol (Benatuil, L., Perez, J. M., Belk, J. & Hsieh, C.-M. An improved yeast transformation method for the generation of very large human antibody libraries. Protein Eng. Des. Sel. PEDS 23, 155–159 (2010)) The genes included 60 bases of overlap with the vector on both the 5′ and 3′ ends, such that homologous recombination would place the genes in frame between the NdeI and XhoI sites on the vector. The transformation efficiency was 2x106 transformants. Several rounds of cell sorting were performed on the library of CTC-445 epPCR, to identify mutations that improve binding to SARS-CoV-2 and improve the stability to proteases, using fluorescence-activated cell sorting (FACS). Yeast was grown in C-Trp-Uraselective medium and later induced for 12- 18 h in SGCAA medium. Cells were incubated with varying concentrations of SARS-CoV- 2 RBD mFc diluted in PBSF (50mM NaPO4, 150mM NaCl, pH 7.4), with decreasing RBD concentrations at every round of sorting: 200 nM (round 1, 108 cells sorted), 10 nM (round 2, 107 cells sorted), 1 nM (round 3, 106 cells sorted), 100 pM (round 4, 106 cells sorted), and 10 pM and 1 pM (round 5, 106 cells sorted). This incubation was done on ice for 30 min, and later washed with chilled PBSF. At sorting rounds 4 and 5, an additional selection for improved koff was added at this stage, where cells were incubated in 1 ml PBSF buffer at 37 °C for 1 hour. Cells were washed again with chilled PBSF buffer. Lastly, cells were incubated with FITC-conjugated chicken anti-cMyc antibody (ICL) and phycoerythrin- conjugated goat anti-mFc antibody (Jackson ImmunoResearch) at 1 μl per 3 × 106 cells for 10 min on ice, and washed again with chilled PBSF buffer. Sorting was performed with the Sony SH800 instrument, selecting the top 5% of the displaying subpopulation by their
PE/FITC fluorescence ratios at each round. Starting from round 2, cells were pretreated before primary labeling with a mixture of trypsin (12.5µg/mL) and chymotrypsin (5µg/mL) in TBS buffer (25mM Tris-HCl, 150mM NaCl, pH 8.0) for 5 min at room temperature. This reaction was halted by adding a large excess volume of ice-cold TBSF 1% (25mM Tris- HCl, 150mM NaCl, 1% w/v BSA, pH 8.0) and washing the cells four additional times with TBSF 1%. Starting at round 1, selected cells were plated on SDCAA agar plates and about 20 colonies from each round were picked, amplified by PCR, and sequenced by Sanger sequencing (Genewiz) to identify mutations selected in each round of FACS. (Chao, G. et al. Isolating and engineering human antibodies using yeast surface display. Nat. Protoc.1, 755–768 (2006)). The sequences identified as CTC-445.01 through CTC-445.68 were identified using error-prone PCR and yeast display FACS. The skilled artisan can use the results to identify substitutions for the ACE2 protein decoys that won’t substantially interfere with binding to coronavirus spike protein. Example 19 – Binding specificity of CTC445.2d assessed using a comprehensive human proteome binding assay. [00235] CTC445.2d at 1 µg/mL (=30 nM) chemically labeled with Alexa-647 was used for the protein-protein interaction assay. A HuProtTM array (CDI Laboratories, Baltimore, MD) with barcodes containing 21,218 proteins and protein isoforms (including S protein RBD) was incubated with the protein sample for 1 hour. After probing, the arrays were washed and images were taken for data collection. CDI software was used to quantify the binding profile of each individual sample to specific proteins on the array based on Z Scores. Z scores were computed using the average Z score of the duplicate spots of a given protein (each protein is printed in duplicate on a HuProtTM array). The Z score of each spot on a given array is calculated according to the formula Z = [F635–F635(avg)] / F635(std), where F635 is the average foreground signal intensity of 2 replicate spots of a given protein in the detection channel (635 nm); B635 is the average background signal intensity of 2 replicate spots of a given protein in the detection channel; and F635(avg) and F635(std) are the average and standard deviation of the F635 values of all spots on the array, respectively. S score is the difference of the Z Scores of a given protein and the one ranked after it. If the S score of the top hit is > 3 from the next hit, the test protein is considered as highly specific against that hit. [00236] Table 13 shows all hits with Z Score > 10. CTC445.2d demonstrates specific binding to the SARS-CoV-2 RBD, with a Fluorescence value of 65,535 translating to the
highest Z Score of 88.6. The S Score to the next highest binding gene, QDPR, is 27.6, demonstrating highly specific binding to the intended target RBD of SARS-CoV-2. The binding of CTC-445.2d to immobilized SARS-CoV-2 RBD-his, QDPR-his and CLEC10A- his was tested by biolayer interferometry. No binding to QDPR and CLEC10A was detected at any tested concentrations of CTC-445.2d (10 µM, 5 µM and 1 µM) (data not shown). Table 13
Example 20 – Positional probability of mutation after binding selection [00237] Deep mutational scanning was performed by yeast display on a saturation mutagenesis library of CTC445.2 for binding to several different concentrations of SARS- CoV-2 RBD protein (6.25pM, 3.125pM, and 1.5625pM). Deep sequencing was used to compute enrichment values for each mutation, and values for the three concentrations were averaged. Enrichment values were then converted to a positional probability score for each mutation at each position, and plotted as a sequence logo using logomaker [ref: https://www.biorxiv.org/content/10.1101/635029v1]. Letters are scaled according to their probability and ordered from highest probability (top) to lowest (bottom). The native sequence of CTC445.2 is shaded in black. The skilled artisan can use the results to guide the selection of preferred and non-preferred substitions at various positions for the ACE2 protein decoys. See Figure 20A-C
Example 21 – Exemplary Clinical Trial Design for De Novo ACE2 Protein Decoys [00238] A clinical design for a De Novo ACE2 Protein Decoy is designed to identify the safety profile, recommended dose and schedule, and clinical activity of the De Novo ACE2 Protein Decoy. The route of administration is local administration to the respiratory tract (including nasopharynx and lungs) by inhalation of nebulized De Novo ACE2 Protein Decoy, and/or systemic administration intravenously. In one study, patient population are COVID-19 patients with high risk of clinical morbidity or mortality from SARS-CoV-2, e.g. who are hospitalized and who require oxygen supplementation for hypoxia. The trial may avoid recruitment of patients who require positive pressure ventilation. The trial is conducted in two parts. The first part is a dose-escalation study intended to investigate the safety of the De Novo ACE2 Protein Decoy in hospitalized hypoxic COVID-19 patients, and to identify the recommended part 2 dose and schedule (RP2DS). The second part is a cohort-expansion study intended to explore the clinical activity of the De Novo ACE2 Protein Decoy in hospitalized hypoxic COVID-19 patient when administered at the RP2DS. Endpoints include e.g. survival, requirement for positive pressure ventilation, time to recovery and/or discharge, and clinical safety profile. Alternatively, the patient population could be individuals at risk of coronavirus infection and administration could be prophylactic. In another study, patient population are healthy subjects at risk of exposure to SARS-CoV-2 or who have been recently exposed to SARS-CoV-2. Example 22: Discussion [00239] Since its emergence as a global pandemic in December of 2019, SARS-CoV-2 has caused millions of COVID-19 cases. The need for effective strategies to prevent and treat the disease remains unfulfilled and urgent. There are multiple ongoing efforts to develop prophylactics and therapeutics using various approaches. A challenge is that the high mutational rate of positive sense single-strand RNA (+ssRNA) viruses (8–10) can often lead to viral escape, which could compromise the efficacy of many SARS-CoV-2 therapeutics under development. Several mutations have already occurred in the spike (S) protein of SARS-CoV-2 in the infected population. Deep sequencing studies of the receptor binding domain (RBD) have shown that simple mutations can enable the virus to escape known neutralizing antibodies. A pressing need therefore exists to develop novel therapeutics that can be more resistant to SARS-CoV-2 mutational escape.
[00240] Traditional approaches to combat viruses (e.g. vaccination and monoclonal antibodies) ultimately rely on molecules interacting with the pathogens in a way that is fundamentally different than how the pathogen engages with its cellular targets. Viruses can exploit such structural discrepancy to evade neutralization, changing the shape of their proteins to prevent recognition by the neutralizing molecules (e.g. antibodies) while preserving viral fitness. To address these challenges, the inventors have developed a computational protein design strategy that enables the rapid and accurate design of hyperstable de novo protein “decoys” that replicate and stabilize the protein receptor interface that a virus attaches to in order to infect a cell. The decoys can achieve a similar or even higher affinity than the original protein receptor due to their contribution to stabilizing the binding interface. Therefore, at high enough concentration, the decoys can be used to neutralize the virus by outcompeting its interaction with the cell. [00241] SARS-CoV-2 invades host cells in a two-step process. First, its S protein RBD attaches to the cell by binding to hACE2, a membrane associated protein, triggering endocytosis. Subsequently, the virus escapes the endosome via a protease-cleavage- mediated fusion peptide. The process is similar to the beta-coronaviruses HCoV-NL63 and SARS-CoV-1, which also target hACE2 for cellular entry. In principle, inhibiting the viral interaction with hACE2 should prevent infection. The design strategy was applied to engineer, validate and optimize de novo hACE2 decoys to neutralize SARS-CoV-2. [00242] Approximately 35,000 plausible computational models of de novo ACE2 decoys were engeinerred. By using yeast display, 196 of the top ranked designs were individually tested for binding. Out-of-the-box, one of the designs, CTC-445, showed strong/nanomolar and specific binding by yeast display for SARS-CoV-2 RBD . In solution, CTC-445 is a 160 a.a. protein comprising 18 of the natural amino acids (it does not contain cysteine or tryptophan residues) and exhibits weaker binding affinity (KD ~ 357 nM) for SARS-CoV-2 than hACE2 (KD = 31 nM, IC50 @ ACE2[0.4nM] = 10.9 nM), and a weak cross reactivity to SARS-CoV-1 (Kd ≈ 55 µM). As a result, CTC-445 is a weak competitor of SARS-CoV-2 RBD binding to hACE2 (IC50 @ ACE2[0.4nM] = 1.7 µM, Fig.1I). The low binding affinity and potency of CTC-445 are likely the result of instability of its folded state (ΔGNI~ -2.7 kcal mol-1, Tm~ 75.3 °C). A single round of directed evolution and the subsequent rational combination of the five most frequently observed stabilizing and affinity-improving mutations (none of them in the binding interface) led to the de novo protein decoy CTC- 445.2. CTC-445.2 is predominantly monomeric, thermodynamically hyperstable (ΔGNI~ - 5.0 kcal mol-1, Tm ~ 93 ℃), exhibits low nanomolar affinity for the RBD of SARS-CoV-2
(KD ~ 21.0 nM), has improved cross-reactivity to SARS-CoV-1 (KD ~ 7.1 µM), and can efficiently compete hACE2 binding to the SARS-CoV-2 RBD (IC50 @ ACE2[0.4nM] ~ 10.4 nM). The sequence of CTC-445.2 has no significant identity with hACE2 (either in terms of linear sequence alignment or structural sequence alignment, ClustalW ~ 22% , MICAN ~ 34%, respectively, Fig. S9). Serial-duplication (i.e. increase in avidity) of CTC-445.2 led to higher potency molecules with favorable biochemical properties. For example, CTC-445.2d (Fig. 2A), a bivalent version of CTC-445.2, has a ~10-fold improvement in binding affinity for both SARS-CoV-2 RBD (KD ~ 3.5 nM) and SARS-CoV-1 RBD (KD ~ 587 nM), and a similar increase in its ability to compete with hACE2 binding to SARS-CoV-2 RBD (IC50 @ ACE2[0.4nM] ~ 700 pM). As well, a trivalent version of CTC-445.2 resulted in even higher (picomolar) binding affinity and competition potency (KD= 270 pM, IC50 @ ACE@[0.4nM] ~ 110 pM). In a cross-reactivity binding assay containing >21,000 human proteins, CTC-445.2d was confirmed to bind to the SARS-CoV-2 RBD with high selectivity. [00243] In a VSV pseudovirus system expressing the SARS-CoV-2 spike protein, the de novo decoys specifically protected HEK 293T cells overexpressing hACE2 from infection. To define the activity of CTC-445.2d as a locally delivered therapeutic to possibly protect the airway from infection, a high dose (100 µg) of CTC-445.2d was delivered to Balb/c mice via inhalation of intranasal droplets. The persistence of fully functional CTC-445.2d was observed in the lungs for more than 24 hours. CTC-445.2d was also detected in blood, raising the possibility that inhaled therapy might lead to some level of systemic exposure. [00244] As designed, the binding interface of the SARS-CoV-2 RBD with CTC-445.2 closely mirrors the target hACE2 interface. Results from deep mutational scanning of CTC-445.2 were as expected, mutations in the core of the design and in the binding interface are generally not preferred, while mutations in surface/exposed residues are mostly irrelevant. [00245] Deep mutational scanning of the SARS-CoV-2 RBD binding interface was performed, to compare the effect of every single mutation on the binding to hACE2 or CTC-445.2. The effects of ~1700 SARS-CoV-2 RBD mutations analyzed show strong correlation between binding to hACE2 and CTC-445.2, highlighting the decoy’s intrinsic resiliency to mutational escape as a result of precisely recapitulating the hACE2 interface that SARS-CoV-2 targets. Notably, at low target concentrations (100 pM), CTC-445.2 has a large binding advantage over ACE2 for many of the RBD mutations, likely a result of both its higher stability and smaller size.
[00246] The high and specific binding affinity of the optimized de novo protein decoys translated into effective and specific in vitro neutralization of SARS-CoV-2 viral infection. In vitro, the presence of the de novo decoys showed no impact on mammalian cell viability or on the enzymatic activity of hACE2. As shown in the examples, the de novo decoys were able to fully neutralize viral infection in in vitro systems of cell infection. [00247] The de novo protein design approach to generate decoys is orthogonal to traditional therapeutics and has the potential to better overcome the problem of mutational viral evasion. Natural proteins repurposed often present significant challenges for development as therapeutics, such as low stability that can complicate manufacturing, transport and storage; residual/undesirable biological activity; and the risk of eliciting an autoimmune response. In contrast, the de novo protein decoys are easy to manufacture (i.e. in traditional bacterial systems) and their thermodynamic hyperstability can enable simplified transport and storage, possibly without the need of a cold chain. In addition, the de novo decoy’s resilience to viral escape is believed to be a unique feature of the described design strategy.
Claims (144)
- WHAT IS CLAIMED IS: 1. An ACE2 protein decoy comprising a decoy unit comprising (i) at least two alpha helical domains, H1 and H2, (ii) an optional beta hairpin domain, H3, and (iii) at least one structural domain; wherein the ACE2 protein decoy specifically binds to a coronavirus ACE2-binding spike protein, the at least two alpha helical domains and optional beta hairpin domain interface with the coronavirus ACE2-binding spike protein, and the at least one structural domain facilitates protein folding and binding- competent presentation of the alpha helices and beta hairpin domains.
- 2. An ACE2 protein decoy comprising a decoy unit comprising two alpha helical domains, H1 and H2, and an optional beta hairpin domain H3, wherein (a) H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176) (b) H2 comprises the amino acid sequence NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) (c) H3, if present, comprises the amino acid sequence X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6) wherein: (i) H1, H2, and H3, if present, can be in any order in the protein; (ii) amino acid linkers may be present between any two of H1, H2, and H3, if present; (iii) X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, X18, X19, X20, X21, X22, X23, X24, X25, X26, X27, X28, X29, X30, X31, X32, X33, X34, X35, and X36 are each independently selected from any amino acid; and (iv) said ACE2 protein decoy specifically binds to a coronavirus ACE2-binding spike protein.
- 3. The ACE2 binding protein decoy of claim 2, wherein said decoy unit further comprises one or more structural domain that facilitates protein folding and binding- competent presentation of H1, H2, and H3, if present, wherein the one or more structural domains and H1, H2, and H3, if present, can be in any order in the protein and amino acid linkers may be present between any one of the one or more structural domains and H1, H2, and H3, if present.
- 4. The ACE2 protein decoy of claim 2 or claim 3, wherein not more than half of the amino acids represented as Xnumber are the same amino acid at the corresponding position in native ACE2 represented by SEQ ID NO:1.
- 5. The ACE2 protein decoy of claim 2 or claim 3, wherein not more than 8 of the amino acids represented as Xnumber are the same amino acid at the corresponding position in native ACE2.
- 6. The ACE2 protein decoy of claim 2 or claim 3, wherein not more than 4, 3, or 2, of the amino acids represented as Xnumber in H1; not more than 4, 3, or 2, of the amino acids represented as Xnumber in H2; and not more than 5, 4, 3, or 2, of the amino acids in H3, if present, are the same amino acid at the corresponding position in native ACE2.
- 7. The ACE2 protein decoy of any one of claims 1-6 wherein H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176) wherein; X1 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X2,X6,X9,X11,X12,and X13, are each independently an amino acid selected from A, F, I, L, M, P or V; X5,X7,X8, and X10 are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X3 is an amino acid selected from A, C, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y and X4 is an amino acid selected from A, F, I, L, M, P, V, D, E, G, K, N, P, Q, R, S, or T.
- 8. The ACE2 protein decoy of any one of claims 1-7 wherein H1 comprises the amino acid sequence: SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4) or X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176); wherein X1 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X2,X6,X9,X11,X12,and X13, are each independently an amino acid selected from A, F, I, L, M, P or V; X3,X5,X7,X8, and X10 are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X4 is an amino acid selected from A, F, I, L, M, P, V, D, E, G, K, N, P, Q, R, S, or T.
- 9. The ACE2 protein decoy of any one one claims 2-8 wherein X4 is an amino acid selected from A, F, I, L, M, P or V.
- 10. The ACE2 protein decoy of any one one claims 2-9 wherein X5 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T (preferably K).
- 11. The ACE2 protein decoy of any one one claims 2-10 wherein X1 is an amino acid selected from R or S.
- 12. The ACE2 protein decoy of any one of claims 2-11 wherein X3 is an amino acid selected from R, L, A, F, I, M, P, or V.
- 13. The ACE2 protein decoy of claim 12 wherein X3 is an amino acid selected from R or L.
- 14. The ACE2 protein decoy of any one of claims 2-13 wherein X7 is an amino acid selected from A or T.
- 15. The ACE2 protein decoy of any one of claims 2-14 wherein X10 is an amino acid selected from R, S or L.
- 16. The ACE2 protein decoy of any one of claims 2-10 wherein X1 is an amino acid selected from R or S; X3 is an amino acid selected from R or L; X7 is an amino acid selected from A or T; and X10 is an amino acid selected from R, S or L.
- 17. The ACE2 protein decoy of any one of claims 2 to 16 wherein X10 is an amino acid selected from R or S.
- 18. The ACE2 protein decoy of any one of claims 2 to 17 wherein X8 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, W, or Y.
- 19. The ACE2 protein decoy of claim 18 wherein X8 is an amino acid selected from F, D, E, G, K, N, P, Q, R, S, or T.
- 20. The ACE2 protein decoy of claim 19 wherein X8 is F.
- 21. The ACE2 protein decoy of claim 8 wherein X1 is an amino acid selected from R or S; X2 is V; X3 is an amino acid selected from R or L; X4 is L; X5 is K; X6 is A; X7 is an amino acid selected from A or T; X8 is F; X9 is M; X10 is an amino acid selected from R or S or L; X11 is F X12 is A; and X13 is A.
- 22. The ACE2 protein decoy of any one of claims 2 to 21 wherein X1 is S.
- 23. The ACE2 protein decoy of any one of claims 2 to 22 wherein X3 is L.
- 24. The ACE2 protein decoy of any one of claims 2 to 23 wherein X1 is S and X3 is L.
- 25. The ACE2 protein decoy of of any one of claims 2-24, wherein H1 comprises the amino acid sequence set forth in SEQ ID NO:10 SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13LX37X38X39X40X41X42X43X44X45 X46 (SEQ ID NO:10) wherein X37, X38,X39,X41,X42,X45, and X46 are each independently an amino acid selected from A, F, I, L, M, P, or V; X40 and X44 are each independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X43 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T.
- 26. The ACE2 protein decoy of any one of claims 1 to 25 wherein H1 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NOS: 11-17, 177-183, 198, or 199: SRVLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:11) SSVREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:12) SRVREQLKTFADKTFHEMEDRFYQAAL (SEQ ID NO:13) SRVREQLKTFADKAFHEMEDSFYQAAL (SEQ ID NO:14) SSVLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:15) SSVLEQLKTFADKTFHEMEDSFYQAAL (SEQ ID NO:16) SRVREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:17) VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:177) VREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:178) VREQLKTFADKTFHEMEDRFYQAAL (SEQ ID NO:179) VREQLKTFADKAFHEMEDSFYQAAL (SEQ ID NO:180) VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:181) VLEQLKTFADKTFHEMEDSFYQAAL (SEQ ID NO:182) VREQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:183) SSVLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:198) VLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:199).
- 27. The ACE2 protein decoy of claim 26, wherein the amino acids at positions 1, 5, 6, 9, 10, 12, 13, 16, 17, 19, 20, 23, 24 and 27 of SEQ ID NOS: 11-17 or 198 or the amino acids at positions 3, 4, 7, 8, 10, 11, 14, 15, 17, 18, 21, 22 and 25 of SEQ ID NOS: 177-183 or 199 are unchanged.
- 28. The ACE2 protein decoy of any one of claims 1-6 wherein H1 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:15 (SSVLEQLKTFADKAFHEMEDRFYQAAL) (SEQ ID NO:15) wherein the amino acid at position 1 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; wherein the amino acid at position 2 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; wherein the amino acid at position 3 is V or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; wherein the amino acid at position 4 is L or if substituted is A, C, D, E, F, G, H, I, K, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 5 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 6 is Q or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, S, T, V, or W; wherein the amino acid at position 7 is L or if substituted is C, I, M, T, or V; wherein the amino acid at position 8 is K or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 9 is T or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, V, W, or Y; wherein the amino acid at position 10 is F or if substituted is A, C, H, V, W, or Y; wherein the amino acid at position 11 is A or if substituted is C, G, L, M, S, T, or V; wherein the amino acid at position 12 is D or if substituted is A, C, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 13 is K or if substituted is A, C, F, H, I, L, M, N, Q, R, S, V, W, or Y; wherein the amino acid at position 14 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, S, T, or V; wherein the amino acid at position 15 is F or if substituted is A, C, D, E, G, H, I, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 16 is H or if substituted is A, C, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 17 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 18 is M or if substituted is A, C, D, F, G, H, I, L, N, Q, S, T, V, W, or Y; wherein the amino acid at position 19 is E or if substituted is D, M, N, P, Q, T, or V; wherein the amino acid at position 20 is D or if substituted is E, F, G, H, L, N, or Q; wherein the amino acid at position 21 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y; wherein the amino acid at position 22 is F or if substituted is C, G, H, L, M, N, W, or Y; wherein the amino acid at position 23 is Y or if substituted is H, D, or F; wherein the amino acid at position 24 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y; wherein the amino acid at position 25 is A or if substituted is C, F, G, H, I, L, M, N, Q, S, T, V, W, or Y; wherein the amino acid at position 26 is A or if substituted is C, D, E, F, G, H, I, L, M, N, Q, S, T, or V; and wherein the amino acid at position 27 is L or if substituted is A, C, D, E, F, G, H, I, K, M, N, Q, R, S, T, V, W, or Y, wherein position numbering is according to SEQ ID NO:15..
- 29. The ACE2 protein decoy of any one of claims 1-28, wherein H2 comprises the amino acid sequence NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X17, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; X16 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y, X19 is an amino acid selected from A, F, I, L, M, P, E, T, or V, and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y.
- 30. The ACE2 protein decoy of any one of claims 1-28, wherein H2 comprises the amino acid sequence NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; X16 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y, and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y.
- 31. The ACE2 protein decoy of any one of claims 2-30, wherein X16 is A, F, I, L, M, P, E, or V.
- 32. The ACE2 protein decoy of any one of claims 2-31 , wherein X15 E; X18 is R; X21 is E; X23 is E; X25 is K; and X27 is D.
- 33. The ACE2 protein decoy of any one of claims 2-32 wherein X14 is A or V; X16 is A or E; and X20 is K or Q.
- 34. The ACE2 protein decoy of claim 33, wherein X14 is A or V; X15 is E; X16 is A or E; X17 is A; X18 is R; X19 is A; X20 is K or Q; X21 is E; X22 is A; X23 is E X24 is A; X25 is K; X26 is A; and X27 is D.
- 35. The ACE2 protein decoy of any one of claims 2-34, wherein H2 further comprises at its N terminus the amino acid sequence set forth in SEQ ID NO: 173 X47X48X49X50X51 (SEQ ID NO: 173) and at its C terminus the amino acid sequence set forth in SEQ ID NO: 174 X52X53X54X55X56 (SEQ ID NO:174) wherein X49, X52, and X55 are each independently an amino acid selected from A, F, I, L, M, P or V; X50 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X54 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and X47, X48, X51, X53, and X56 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T.
- 36. The ACE2 protein decoy of claim 35 wherein X47 is G or E; X48 is D; X49 is A; X50 is G or A; and X51 is R.
- 37. The ACE2 protein decoy of claim 35 wherein X47 is G or E.
- 38. The ACE2 protein decoy of any one of claims 35-37 wherein X47 is G.
- 39. The ACE2 protein decoy of any one of claims 35-38 wherein X54 is A, F, I, L, M, P or V.
- 40. The ACE2 protein decoy of any one of claims 35-38 wherein X52 is A; X53 is E; X54 is L or F or N; X55 is A; and X56 is K.
- 41. The ACE2 protein decoy of any one of claims 35-39 wherein X54 is F or L.
- 42. The ACE2 protein decoy of claim 41 wherein X54 is L.
- 43. The ACE2 protein decoy of any one of claims 1 to 42, wherein H2 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NOS 21-22: NAENAARKAKEFAEEQAKLADMY (SEQ ID NO:21) NVENEARKAQEFAEEQAKLADMY (SEQ ID NO:22)
- 44. The ACE2 protein decoy of claim 43, wherein the amino acids at positions 1, 4, 8, 12, 15, 16, 19, 22 and 23 of SEQ ID NO: 21 or 22 are unchanged.
- 45. The ACE2 protein decoy of any one of claims 1-28, wherein H2 comprises the amino acid sequence NX14X15NX16X17X18KX19X20X21FX22X23EQX24X25LX26X27MY (SEQ ID NO:5) wherein: X15, X18, X21, X23, X25, and X27 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X14, X16, X17, X19, X22, X24, and X26 are each independently an amino acid selected from A, F, I, L, M, P or V; and X20 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y.
- 46. The ACE2 protein decoy of any one of claims 1-28, wherein H2 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:21: wherein the amino acid at position 1 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 2 is A or if substituted is C, D, G, H, I, L, M, N, P, R, S, T, V, or W; wherein the amino acid at position 3 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 4 is N or if substituted is A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 5 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 6 is A or if substituted is C, D, E, G, I, L, M, N, P, Q, S, T, V, W, or Y; wherein the amino acid at position 7 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, Y, or W; wherein the amino acid at position 8 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 9 is A or if substituted is C, D, G, I, L, Q, S, T, V, or W; wherein the amino acid at position 10 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, or W; wherein the amino acid at position 11 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 12 is F or if substituted is A, C, D, E, G, I, K, L, M, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 13 is A or if substituted is C, D, F, G, I, L, M, N, S, T, V, W, or Y; wherein the amino acid at position 14 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 15 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; wherein the amino acid at position 16 is Q or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, R, S, T, Y, or V; wherein the amino acid at position 17 is A or if substituted is C, E, F, G, I, L, M, Q, S, T, V, or W; wherein the amino acid at position 18 is K or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 19 is L or if substituted is A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, Y, or W; wherein the amino acid at position 20 is A or if substituted is C, F, G, I, L, S, T, V, or Y; wherein the amino acid at position 21 is D or if substituted is A, C, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y; wherein the amino acid at position 22 is M or if substituted is A, C, D, E, F, G, H, I, K, L, N, Q, R, S, T, V, W, or Y; and wherein the amino acid at position 23 is Y or if substituted is D, F, H, I, L, M, or V; wherein position numbering is according to SEQ ID NO:21.
- 47. The ACE2 protein decoy of any one claims 1-46, wherein H3 is present.
- 48. The ACE2 protein decoy of claim 47, wherein H3 comprises the amino acid sequence X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6) wherein: X31 is an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X35 is an amino acid selected from D, E, G, K, N, P, Q, R, S, V, or T; X29 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X33 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X30, X32, and X36 are each independently an amino acid selected from A, F, I, L, M, P or V; X28 is an amino acid selected from A, F, I, L, M, P, T, or V; and X34 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y and optionally C.
- 49. The ACE2 protein decoy of claim 47, wherein H3 comprises the amino acid sequence X28X29X30X31X32X33KGDX34RX35X36 (SEQ ID NO:6) wherein: X31 and X35 are each independently an amino acid selected from D, E, G, K, N, P, Q, R, S, or T; X29 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X33 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; X28, X30, X32, and X36 are each independently an amino acid selected from A, F, I, L, M, P or V; and X34 is an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y and optionally C.
- 50. The ACE2 protein decoy of any one of claims 47-49 , wherein X34 is F, D, E, G, K, N, P, Q, R, S, Y, C, or T.
- 51. The ACE2 protein decoy of any one of claims 47-50, wherein X33 is G, A, F, I, L, M, P or V.
- 52. The ACE2 protein decoy of any one of claims 47-51, wherein X29 is D, E, G, K, N, P, Q, R, S, T, or V.
- 53. The ACE2 protein decoy of any one of claims 47 to 52 wherein X28 is A or V; X29 is E or V; X31 is D; X32 is M or L; X33 is G; and X34 is an amino acid selected from F, Y, K or C.
- 54. The ACE2 protein decoy of any one of claims 47 to 53 wherein X30 is I; X35 is E; and X36 is I.
- 55. The ACE2 protein decoy of any one of claims 47 to 54 wherein X32 is L.
- 56. The ACE2 protein decoy of any one of claims 47 to 55 wherein X31 is D.
- 57. The ACE2 protein decoy of any one of claims 47-56, wherein H3 further comprises at its N terminus an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and H3 further comprises at its C terminus an amino acid selected from D, E, G, K, N, P, Q, R, S, C or T.
- 58. The ACE2 protein decoy of any one of claims 47 to 57, wherein X34 is not C or wherein if X34 is C, X3 is L and/or X32 is L.
- 59. The ACE2 protein decoy of any one of claims 1 to 58, wherein H3 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NOS 29-34 or 200: AEIDLGKGDFREI (SEQ ID NO:29) AEIDLGKGDCREI (SEQ ID NO:30) VVIDLGKGDFREI (SEQ ID NO:31) VVIDLGKGDCREI (SEQ ID NO:32) AEIDMGKGDCREI (SEQ ID NO:33) AEIDMGKGDFREI (SEQ ID NO:34) VEIDLGKGDFREI (SEQ ID NO: 200).
- 60. The ACE2 protein decoy of claim 47 wherein H3 comprises an amino acid sequence having at least 70%, 80%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:29: wherein the amino acid at position 1 is A or if substituted is C, D, E, G, I, L, M, P, Q, R, S, T, V, or W; wherein the amino acid at position 2 is E or if substituted is A, C, D, G, L, M, P, R, S, T, V, or W; wherein the amino acid at position 3 is I or if substituted is C, F, L, M, T, V, or W; wherein the amino acid at position 4 is D or if substituted is A, C, E, G, I, K, L, M, N, S, T, or V; wherein the amino acid at position 5 is L or if substituted is F, I, M, or V; wherein the amino acid at position 6 is G or if substituted is D, or L; wherein the amino acid at position 7 is K or if substituted is I, M, N, Q, R, or T; wherein the amino acid at position 8 is G or if substituted is D, E, M, R, or S; wherein the amino acid at position 9 is D or if substituted is E, K, or T; wherein the amino acid at position 10 is F or if substituted is A, C, E, G, I, K, L, Q, R, S, T, V, W, or Y; wherein the amino acid at position 11 is R or if substituted is K, M, Q, or S; wherein the amino acid at position 12 is E or if substituted is A, C, D, G, H, K, L, M, P, R, S, T, V, W, or Y; and wherein the amino acid at position 13 is I or if substituted is A, C, D, F, G, H, L, M, N, P, Q, R, S, T, V, or W; wherein position numbering is according to SEQ ID NO:29.
- 61. The ACE2 protein decoy of any one of the previous claims, wherein the decoy unit comprises two or more structural domains that facilitate protein folding and binding- competent presentation of the alpha helices and beta hairpin domains to the coronavirus spike protein.
- 62. The ACE2 protein decoy of claim 61, wherein the two or more structural domains that facilitate protein folding and binding-competent presentation of the alpha helices and beta hairpin domains to the coronavirus spike protein independently comprise an amino acid sequence selected from the group consisting of: D1 – XAXAXBXBXCXBXBXBXAXBXBXAXCXBXCXAXBXCXAXCXCXAXAXBXCXAXA (SEQ ID NO:35) and D2 – XAXCXCXAXBXBXAXCXBXBXAXBXBXAXCXBXBXAXBXBXDXAXBXBXAXCXBXBXA XC (SEQ ID NO:36) wherein each XA is an amino acid selected from D, E, G, K, N, P, Q, R, S, C, or T; each XB is independently an amino acid selected from A, F, I, L,M, or P, each XC is independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R,S, T, V, W, Y or C; and each XD is independently an amino acid selected from A, D, E, F, G, I, K, L, M, N, P, Q, R,S, T, V, W, Y or C (preferably A, F, I, L, M, P, or V).
- 63. The ACE2 protein decoy of claim 62, wherein the decoy unit comprises at least two structural domains that facilitate protein folding and binding-competent presentation of the alpha helices and beta hairpin domains to the coronavirus spike protein, wherein a first structural domain comprises the sequence of SEQ ID NO: 35 and the second structural domain comprises the sequence of SEQ ID NO: 36.
- 64. The ACE2 protein decoy of any one of claims 1-63 wherein the decoy unit comprises a structural domain represented by D1 and D1 comprises an amino acid sequence at least 60% , 70%, 80%, 85%, 90%, 95% or 100% identical an the amino acid sequence as set forth in SEQ ID NO:38: REAAEALAEAARAMKEALEIIREIAEK (SEQ ID NO:38).
- 65. The ACE2 protein decoy of any one of claims 1-63 wherein the decoy unit comprises a structural domain represented by D1 and D1 comprises an amino acid sequence at least 60% , 70%, 80%, 85%, 90%, 95% or 100% identical an the amino acid sequence as set forth in SEQ ID NO:222: REAAEALAEAARAMKEALEILREIAEK (SEQ ID NO:222).
- 66. The ACE2 protein decoy of any one of claims 1-65 wherein the decoy unit comprises a structural domain represented by D2 and D2 comprises an amino acid sequence at least 60% , 70%, 80%, 85%, 90%, 95% or 100% identical to an amino acid sequences set forth in SEQ ID NO:41-46: RASEAAKRX59AX60AIRKAADAIX61X62AAKIAARA (SEQ ID NO:41), wherein X59 is I or V, X60 is K or R or C, X61 is A or V or C, and X62 is E or C; RASEAAKR IAKAIRKAADAIAEAAKIAARA (SEQ ID NO:42); RASEAAKR IACAIRKAADAIAEAAKIAARA (SEQ ID NO:43); RASEAAKR IAKAIRKAAD AIACAAKIAA RA (SEQ ID NO:44); RASEAAKR VARAIRKAAD AIVEAAKIAA RA (SEQ ID NO:45); RASEAAKR VACAIRKAAD AIVEAAKIAA RA (SEQ ID NO:46).
- 67. The ACE2 protein decoy of claim 61 wherein at least one structural domain (e.g., D1) comprises an amino acid sequence having at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:38 wherein the amino acid at position 1 is R or if substituted is A, C, E, F, G, I, K, L, M, P, S, T, V, or W (preferably C, E, F, G, K, L, M, P, S, T, or W ); wherein the amino acid at position 2 is E or if substituted is A, C, D, F, G, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, G, K, M, V, W, or Y); wherein the amino acid at position 3 is A or if substituted is C, E, G, K, L, M, P, Q, R, S, T, V, W, or Y (preferably C, K, P, Q, or V); wherein the amino acid at position 4 is A or if substituted is D, E, G, I, K, L, M, N, P, R, S, T, V, or W (preferably E, N, T, V, or W); wherein the amino acid at position 5 is E or if substituted is C, D, G, K, L, Q, R, S, T, V, W, or Y (preferably C, D, Q, S, V, W, or Y); wherein the amino acid at position 6 is A or if substituted is C, D, E, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, K, P, R, V, or Y); wherein the amino acid at position 7 is L or if substituted is A, C, F, I, M, Q, S, T, or V (preferably T); wherein the amino acid at position 8 is A or if substituted is C, D, E, F, G, H, I, K, Q, L, M, R, S, T, V, or W (preferably D, E, G, H, I, L, Q, R, S, V, or W); wherein the amino acid at position 9 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, R, S, V, W, or Y (preferably A, D, H, L, M, N, R, S, or V); wherein the amino acid at position 10 is A or if substituted is C, G, L, M, Q, S, T, V, or W (preferably C, G, M, or S); wherein the amino acid at position 11 is A or if substituted is C, D, G, L, M, N, Q, R, S, T, or V (preferably C, G, M, S, T, or V); wherein the amino acid at position 12 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, K, M, N, P, Q, S, T, V, W, or Y); wherein the amino acid at position 13 is A or if substituted is C, D, E, F, G, H, K, L, M, P, Q, R, S, T, V, W, or Y (preferably D, E, K, M, R, S, or V); wherein the amino acid at position 14 is M or if substituted is A, C, D, E, G, H, I, K, L, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, K, R, S, T, V, or Y ); wherein the amino acid at position 15 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably E, G, H, M, R, S, or Y); wherein the amino acid at position 16 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, G, K, L, M, Q, T, V, or W); wherein the amino acid at position 17 is A or if substituted is C, G, P, S, T, or V (preferably C, G, or T); wherein the amino acid at position 18 is L or if substituted is C, F, H, I, K, M, N, Q, R, T, V, W, or Y (preferably C, F, H, or V); wherein the amino acid at position 19 is E or if substituted is A, C, D, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, F, G, L, Q, R, S, T, V, or Y); wherein the amino acid at position 20 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, Q, R, S, T, V, W, or Y (preferably C, E, G, L, Q, R, S, T, V, or Y); wherein the amino acid at position 21 is I or if substituted is A, C, D, E, F, G, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, F, L, M, N, S, T, V, or Y); wherein the amino acid at position 22 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, Y, or W (preferably A, C, D, E, F, G, I, L, M, Q, S, T, V, or Y); wherein the amino acid at position 23 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, F, H, I, M, N, P, T, or W); wherein the amino acid at position 24 is I or if substituted is A, C, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, or Y (preferably C, S, T, or V); wherein the amino acid at position 25 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably D, G, H, I, M, N, S, V, or Y); wherein the amino acid at position 26 is E or if substituted is A, C, D, F, G, H, I, K, L, M, Q, R, S, T, V, W, or Y (preferably C, F, I, L, S, T, or Y); and wherein the amino acid at position 27 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, F, G, H, M, N, S, or Y); and at least one structural domain (e.g., D2) comprises an amino acid sequence having at least 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100% identity to an amino acid sequence set forth in SEQ ID NO:42 wherein the amino acid at position 1 is R or if susbstituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, E, H, K, L, N, Q, S, or Y); wherein the amino acid at position 2 is A or if susbstituted is C, G, I, L, M, N, P, Q, S, T, V, or Y (preferably C, M, Q, T, or V); wherein the amino acid at position 3 is S or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y (preferably C, E, F, G, I, L, M, Q, or R); wherein the amino acid at position 4 is E or if substituted is A, C, D, F, G, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, I, N, S, or W); wherein the amino acid at position 5 is A or if substituted is C, D, E, F, G, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably D, E, I, M, or Y); wherein the amino acid at position 6 is A or if substituted is C, F, G, S, or T (preferably C or S); wherein the amino acid at position 7 is K or if substituted is A, C, D, E, G, H, L, M, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, R, S, T, V, W, or Y); wherein the amino acid at position 8 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably A, C, D, E, G, H, L, M, Q, S, T, V, or Y); wherein the amino acid at position 9 is I or if substituted is A, C, F, G, K, L, M, Q, S, T, V, W, or Y (preferably A, C, F, G, L, M, S, T, W, or Y); wherein the amino acid at position 10 is A or if substituted is D, G, T, or V (preferably D, G, or V); wherein the amino acid at position 11 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, L, M, Q, R, S, V, W, or Y); wherein the amino acid at position 12 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably E, G, I, S, or T); wherein the amino acid at position 13 is I or if substituted is A, C, D, E, F, G, H, L, M, N, Q, S, T, V, or Y (preferably A, C, D, F, G, L, M, N, Q, S, T, or V); wherein the amino acid at position 14 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, Q, S, T, V, W, or Y (preferably F, H, K, L, N, V, or W); wherein the amino acid at position 15 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, F, G, H, I, L, M, N, Q, R, S, T, V, W, or Y); wherein the amino acid at position 16 is A or if substituted is C, F, G, M, P, S, T, V, or Y (preferably G, T, or Y); wherein the amino acid at position 17 is A or if substituted is C, D, E, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y (preferably G, T, or V); wherein the amino acid at position 18 is D or if substituted is A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, F, G, I, L, N, R, S, T, W, or Y); wherein the amino acid at position 19 is A or if substituted is C, D, E, F, G, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably G, K, M, Q, S, or T); wherein the amino acid at position 20 is I or if substituted is A, C, F, G, H, L, M, Q, T, V, W, or Y (preferably G, L, M, T, V, or Y); wherein the amino acid at position 21 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably D, E, G, I, K, M, N, Q, S, T, V, W, or Y); wherein the amino acid at position 22 is E or if substituted is A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, D, G, K, M, P, S, T, V, W, or Y); wherein the amino acid at position 23 is A or if substituted is C, G, N, S, T, or V (preferably G, S, or T); wherein the amino acid at position 24 is A or if substituted is C, D, E, G, K, M, N, S, T, or V (preferably C, G, or T); wherein the amino acid at position 25 is K or if substituted is A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably A, C, D, E, G, I, L, P, Q, R, S, V, W, or Y); wherein the amino acid at position 26 is I or if substituted is A, C, D, E, F, G, H, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, E, K, L, M, P, Q, R, S, or V); wherein the amino acid at position 27 is A or if substituted is C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y (preferably F, G, M, N, S, T, or V); wherein the amino acid at position 28 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, Y, or W (preferably C, D, E, G, H, Q, S, T, V, or Y); wherein the amino acid at position 29 is R or if substituted is A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y (preferably A, C, D, G, H, I, K, L, M, N, P, S, T, V, W, or Y); and wherein the amino acid at position 30 is A or if substituted is C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y (preferably C, D, G, H, K, N, P, Q, R, S, T, or V); wherein position numbering is according to SEQ ID NO:38 .
- 68. The ACE2 protein decoy of any one of claims 1 to 67 wherein H1 comprises the amino acid sequence SX1X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:4).
- 69. The ACE2 protein decoy of any one of claims 1 to 67 wherein H1 comprises the amino acid sequence X2X3EQX4X5TFX6DKX7X8HEX9EDX10X11YQX12X13L (SEQ ID NO:176).
- 70. The ACE2 protein decoy of claim 68 wherein one or more of the following substitutions are made in SEQ ID NO:4: S1I; E5D; E5Q; E5V; D12V, D12E; Q24K; and Q24L; wherein the noted positions are according to the numbering of SEQ ID NO:4.
- 71. The ACE2 protein decoy of claim 69 wherein one or more of the following substitutions are made in SEQ ID NO:176:; E3D; E3Q; E3V; D10V, D10E; Q22K; and Q22L; wherein the noted positions are according to the numbering of SEQ ID NO:176.
- 72. The ACE2 protein decoy of any one of claims 1 to 71 wherein the following substitution is made in SEQ ID NO:5: E15G; wherein the noted positions are according to the numbering of SEQ ID NO:4.
- 73. The ACE2 protein decoy of any one of claims 1-72 comprising a H1 domain comprising an amino acid sequence having at least 80% identity to VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:177) or VLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:199); a H2 domain comprising an amino acid sequence having at least 80% identity to NAENAARKAKEFAEEQAKLADMY (SEQ ID NO:21); and a H3 domain comprising an amino acid sequence having at least 80% identity to AEIDLGKGDFREI (SEQ ID NO:29) or VEIDLGKGDFREI (SEQ ID NO:200).
- 74. The ACE2 protein decoy of claim 73 comprising a H1 domain comprising an amino acid sequence having at least 90% identity to VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:177) or VLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:199); a H2 domain comprising an amino acid sequence having at least 80% identity to NAENAARKAKEFAEEQAKLADMY (SEQ ID NO:21); and a H3 domain comprising an amino acid sequence having at least 80% identity to AEIDLGKGDFREI (SEQ ID NO:29) or VEIDLGKGDFREI (SEQ ID NO:200).
- 75. The ACE2 protein decoy of claim 73 comprising a H1 domain comprising the amino acid sequence VLEQLKTFADKAFHEMEDRFYQAAL (SEQ ID NO:177) or VLEQLKTFADKAFHEMEDLFYQAAL (SEQ ID NO:199); a H2 domain comprising the amino acid sequence NAENAARKAKEFAEEQAKLADMY (SEQ ID NO:21); and a H3 domain comprising the amino acid sequence AEIDLGKGDFREI (SEQ ID NO:29) or VEIDLGKGDFREI (SEQ ID NO:200).
- 76. The ACE2 protein decoy of any one of claims 1-72 comprising a H1 domain comprising an amino acid sequence having at least 80% identity to VLEQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:241) or VLEQLKTFADKAFHEMEDLFYQAAL AVFEAAEAAAG (SEQ ID NO:243); a H2 domain comprising an amino acid sequence having at least 80% identity to GDAARNAENAARKAKEFAEEQAKLADMYAELAK (SEQ ID NO:244); and a H3 domain comprising an amino acid sequence having at least 80% identity to SAEIDLGKGDFREIR (SEQ ID NO:245) or SVEIDLGKGDFREIR (SEQ ID NO:246).
- 77. The ACE2 protein decoy of claim 76 comprising a H1 domain comprising an amino acid sequence having at least 90% identity to VLEQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:241) or VLEQLKTFADKAFHEMEDLFYQAAL AVFEAAEAAAG (SEQ ID NO:243); a H2 domain comprising an amino acid sequence having at least 90% identity to GDAARNAENAARKAKEFAEEQAKLADMYAELAK (SEQ ID NO:44); and a H3 domain comprising an amino acid sequence having at least 90% identity to SAEIDLGKGDFREIR (SEQ ID NO:245) or SVEIDLGKGDFREIR (SEQ ID NO:246).
- 78. The ACE2 protein decoy of claim 76 comprising a H1 domain comprising the amino acid sequence VLEQLKTFADKAFHEMEDRFYQAALAVFEAAEAAAG (SEQ ID NO:241) or VLEQLKTFADKAFHEMEDLFYQAAL AVFEAAEAAAG (SEQ ID NO:243); a H2 domain comprising the amino acid sequence GDAARNAENAARKAKEFAEEQAKLADMYAELAK (SEQ ID NO:44); and a H3 domain comprising the amino acid sequence SAEIDLGKGDFREIR (SEQ ID NO:245) or SVEIDLGKGDFREIR (SEQ ID NO:246).
- 79. The ACE2 protein decoy of any one of claims 73-78 comprising a structural domain represented by D1 wherein the D1 domain comprises an amino acid sequence having at least 60%, 70%, 80%, 85%, 90%, 95% or 100% identity to REAAEALAEAARAMKEALEIIREIAEK (SEQ ID NO: 38) or REAAEALAEAARAMKEALEILREIAEK (SEQ ID NO:222). 80. The ACE2 protein decoy of any one of claims 73-79 comprising a structural domain represented by D2 wherein D2 comprises an amino acid sequence having at least 60%, 70%,
- 80%, 85%, 90%, 95% or 100% identity to RASEAAKR IAKAIRKAADAIAEAAKIAARA (SEQ ID NO: 42).
- 81. The ACE2 protein decoy of any one of claims 1-80, wherein the order of the two alpha helical domains, H1 and H2 and beta hairpin domain, H3, in the decoy unit is H3, H2, and H1.
- 82. The ACE2 protein decoy of any one of claims 1-80, wherein the order of the two alpha helical domains, H1 and H2 and beta hairpin domain, H3, in the decoy unit is H1, H3, and H2.
- 83. The ACE2 protein decoy of any one of claims 1-82, wherein the decoy unit comprises at least one linker (XL) between the domains, wherein the at least one linker (XL), or each linker (XL), comprises 1-100, 1-90, 1-80, 1-70, 1-60, 1-50, 1-40, 1-30, 1-20, 1-10, or 1-5 amino acids.
- 84. The ACE2 protein decoy of claim 83, wherein each linker (XL) comprises 1-20, 1- 10, or 1-5 amino acids.
- 85. The ACE2 protein decoy of claim 83 or claim 84, wherein the order of alpha helical domains, H1 and H2, and beta hairpin domain, H3, in the decoy unit is H3, H2, and H1, and the decoy unit comprises a first linker between H3 and H2 and a second linker between H2 and H1; or the order is H1, H3, and H2, and the decoy unit comprises a first linker between H1 and H3 and a second linker between H3 and H2.
- 86. The ACE2 protein decoy of any one of claims 1-85, wherein the decoy unit comprises an amino acid sequence at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS: 47-90, 104-172, 184-193, 224-239, 255-260, or 265-266; wherein each XL is, independently, an amino acid linker.
- 87. The ACE2 protein decoy of claim 86 wherein the amino acid at position 88 is selected from A, F, I, L, M, P or V, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184-187, 189-192 or 224-239.
- 88. The ACE2 protein decoy of claim 86 or claim 87 wherein the amino acid at position 137 is selected from F, D, E, G, K, N, P, Q, R, S, or T, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184-187, 189-192 or 224- 239.
- 89. The ACE2 protein decoy of any one of claims 86-88 wherein if the amino acid at position 11 is cysteine, the amino acid at position 6 is L and/or the amino acid at position 126 is L and/or the amino acid at position 124 is S; wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184-187, 189- 192 or 224-239.
- 90. The ACE2 protein decoy of any one of claims 86-89 wherein no more than 4 of the amino acids at positions 8, 9, 10, 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184- 187, 189-192 or 224-239. 91. The ACE2 protein decoy of any one of claims 86-89 wherein no more than 3 of the amino acids at positions 8, 9, 10,
- 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184- 187, 189-192 or 224-239.
- 92. The ACE2 protein decoy of any one of claims 86-89 wherein no more than 2 of the amino acids at positions 8, 9, 10, 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184- 187, 189-192 or 224-239.
- 93. The ACE2 protein decoy of any one of claims 86-89 wherein no more than 1 of the amino acids at positions 8, 9, 10, 91, 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184- 187, 189-192 or 224-239. 94. The ACE2 protein decoy of any one of claims 86-89 wherein none of the amino acids at positions 8, 9, 10, 91,
- 94, 98, 102, 105, 106, 109, 112, 113123, 127, 128, 131, 132, 134, 138, 139, 141, 142, 145, 146, or 149 is substituted, wherein position numbering is according to any one of SEQ ID NOS: 47-90, 104-172, 184-187, 189- 192 or 224-239.
- 95. The ACE2 protein decoy of any one of the preceding claims, wherein the ACE2 protein decoy consists of 100-800 amino acids, 100-500 amino acids, or 100-400 amino acids, or 100-350 amino acids, or 100-300 amino acids, or 100-250 amino acids, or 100-200 amino acids, or 150-500 amino acids, or 150-400 amino acids, or 150-350 amino acids, or 150-300 amino acids, or 150-250 amino acids, or 150-200 amino acids.
- 96. The ACE2 protein decoy of any one claims 1-94, wherein each decoy unit consists of 100-800 amino acids, 100-500 amino acids, or 100-400 amino acids, or 100-350 amino acids, or 100-300 amino acids, or 100-250 amino acids, or 100-200 amino acids, or 150-500 amino acids, or 150-400 amino acids, or 150-350 amino acids, or 150-300 amino acids, or 150-250 amino acids, or 150-200 amino acids.
- 97. The ACE2 protein decoy of any one of the preceding claims, wherein the ACE2 protein decoy has no more than 60%, 55%, 50%, 45%, 40%, or 35% sequence identity to ACE2 (SEQ ID NO: 1).
- 98. The ACE2 protein decoy of any one of claims 1-96, wherein each decoy unit has no more than 60%, 55%, 50%, 45%, 40%, or 35% sequence identity to ACE2 (SEQ ID NO: 1).
- 99. The ACE2 protein decoy of any one of the preceding claims wherein the coronavirus is SARS-CoV-2.
- 100. The ACE2 protein decoy of any one of the preceding claims that blocks more than 50%, more than 60%, more than 70% more than 80% or more than 90% coronavirus binding to human ACE2.
- 101. The ACE2 protein decoy of any one of the preceding claims that inhibits or prevents entry of coronavirus into a host cell.
- 102. The ACE2 protein decoy of any one of the preceding claims that reduces coronavirus viral infectivity of host cells.
- 103. The ACE2 protein decoy of any one of the preceding claims having a Kd of less than about 20 nm, or less than about 15 nM, for the coronavirus spike protein as determined in biolayer interferometry.
- 104. The ACE2 protein decoy of any one of the preceding claims having a Kd of less than about 5 nM for the coronavirus spike protein as determined in biolayer interferometry.
- 105. The ACE2 protein decoy of any one of the preceding claims that inhibits interaction of the spike protein with ACE2 with an IC50 of 50, 40, 30, 20, 10, or 5 nM or less.
- 106. The ACE2 protein decoy of any one of the preceding claims, wherein the decoy unit comprises 0-4 cysteine amino acids or 0-2 cysteine amino acids.
- 107. The ACE2 protein decoy any one of claims 1 to 105, wherein 1-4 amino acids are substituted for cysteine.
- 108. The ACE2 protein decoy of any of the previous claims, wherein the decoy unit comprises one cysteine amino acid.
- 109. The ACE2 protein decoy of any one of claims 106-108 wherein the cysteine amino acid is alkylated.
- 110. The ACE2 protein decoy of any one of claims 106-109 wherein the cysteine is in the one or more structural domain that facilitates protein folding and binding-competent presentation of H1, H2, and H3.
- 111. The ACE2 protein decoy of any one of the preceding claims wherein the ACE2 protein decoy is linked to a stabilization compound.
- 112. The ACE2 protein decoy of claim 111 wherein the stabilization compound is a Fc region of an antibody.
- 113. The ACE2 protein of claim 112 wherein the Fc region is a translational fusion with the ACE2 protein decoy.
- 114. The ACE2 protein decoy of any one of claims 1-113 wherein the ACE2 protein decoy is linked to a stabilization compound at a cysteine of the ACE2 protein decoy.
- 115. The ACE2 protein decoy of claim 107 or claim 114 wherein the stabilization compound is a PEG molecule.
- 116. The ACE2 protein decoy of claim 115 wherein the PEG molecule is linked to the ACE2 protein decoy at a cysteine of the protein.
- 117. The ACE2 protein decoy of claim 116 wherein the PEG molecule is linked to the ACE2 protein decoy at a cysteine of the protein via a maleide group.
- 118. The ACE2 protein decoy of any one of claims 1 to 117, wherein the ACE2 protein decoy comprises one, two, three, four, or more decoy units.
- 119. The ACE2 protein decoy of claim 118 wherein the ACE2 protein decoy comprises two or more decoy units and the C terminus of a first decoy unit is linked to the N terminus of a second decoy unit.
- 120. The ACE2 protein decoy of claim 118 or 119 wherein the ACE2 protein decoy comprises two or more decoy units and the two or more decoy units are different.
- 121. The ACE2 protein decoy of claim 118 or 119 wherein the ACE2 protein decoy comprises two or more decoy units and the two or more decoy units are the same.
- 122. The ACE2 protein decoy of any one of claims 118-121 wherein the ACE2 protein decoy comprises two or more decoy units and the ACE2 protein decoy comprises an amino acid sequence at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS: 91-95, 194- 197, 223 or 261-263.
- 123. The ACE2 protein decoy of claim 122 wherein the ACE2 protein decoy is cyclized.
- 124. A pharmaceutical composition comprising an ACE2 protein decoy of any one of the preceding claims and a pharmaceutically acceptable carrier or diluent.
- 125. An isolated polynucleotide comprising a polynucleotide sequence that encodes an ACE2 protein decoy as set forth in any one of claims 1-123.
- 126. A vector comprising the polynucleotide of claim 125.
- 127. An isolated host cell comprising the vector of claim 126.
- 128. An isolated host cell that expresses the ACE2 protein decoy of any one of claims 1- 123.
- 129. A method of producing an ACE2 protein decoy comprising incubating the host cell of claim 127 or 128 under conditions suitable for expressing the ACE2 protein decoy.
- 130. The method of claim 129, further comprising isolating the ACE2 protein decoy.
- 131. A method of preventing coronavirus infection, the method comprising administering a ACE2 protein decoy of any one of claims 1-123 or the pharmaceutical composition of claim 124 to a subject in need thereof.
- 132. A method of preventing, treating or ameliorating at least one symptom of coronavirus infection, the method comprising administering a ACE2 protein decoy of any one of claims 1-123 or the pharmaceutical composition of claim 124 to a subject in need thereof.
- 133. A method of preventing, treating or ameliorating at least one symptom of coronavirus infection, the method comprising administering a nucleic acid encoding an ACE2 protein decoy of any one of claims 1-123.
- 134. The method of claim 132 or 133, wherein the at least one symptom or indication is selected from the group consisting of inflammation in the lung, alveolar damage, viral load, fever, cough, shortness of breath, pneumonia, diarrhea, organ failure, and septic shock.
- 135. The method of any one of claims 131-134, wherein the pharmaceutical composition or ACE2 protein decoy or nucleic acid encoding ACE2 protein decoy is administered prophylactically or therapeutically to the subject in need thereof.
- 136. The method of any one of claims 131-134, wherein the pharmaceutical composition or ACE2 protein decoy or nucleic acid encoding ACE2 protein decoy is administered in combination with a second therapeutic agent.
- 137. The method of claim 136, wherein the second therapeutic agent is selected from the group consisting of an anti-inflammatory drug (such as corticosteroids, and non- steroidal anti-inflammatory drugs), an anti-viral drug, antibiotics, a dietary supplement such as anti-oxidants and any other palliative therapy to treat coronavirus infection.
- 138. The method of claim 136 or 137, wherein the second therapeutic agent is a drug used to treat cytokine release syndrome.
- 139. The method of any one of claims 123, 124, 131, 132, or 134-138, wherein the pharmaceutical composition or the ACE2 protein decoy is administered systemically.
- 140. The method of any one of claims 123, 124, 131, 132, or 134-138, wherein the pharmaceutical composition or the ACE2 protein decoy is administered locally.
- 141. The method of claim 140, wherein the pharmaceutical composition or the ACE2 protein decoy is administered via inhalation to the lung.
- 142. The method of any one of claims 131-141 wherein the infection is caused by SARS- CoV-2.
- 143. A method of detecting coronavirus spike protein SARS-CoV-2-S in a biological sample comprising the steps of contacting the biological sample with an ACE2 protein decoy of any one of claims 1-122 and detecting coronavirus spike protein in the biological sample.
- 144. An ACE2 protein decoy that specifically binds to coronavirus ACE2-binding spike protein SARS-CoV-2-S, wherein the ACE2 protein decoy comprises an amino acid sequence at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identical to an amino acid sequence set forth in SEQ ID NOS: 47-95, 104-172, 184- 197, 223-239, 255-263, or 264-265 wherein each XL is, independently, an amino acid linker.
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