WO2022252131A1

WO2022252131A1 - Multivalent recombinant ace2 and uses thereof

Info

Publication number: WO2022252131A1
Application number: PCT/CN2021/097782
Authority: WO
Inventors: Xiaohu Liu; Yanal M. Murad; Kuan Zhang; William Wei-Guo JIA
Original assignee: Virogin Biotech Canada Ltd.; Virogin Biotech (Shanghai) Ltd.
Priority date: 2021-06-01
Filing date: 2021-06-01
Publication date: 2022-12-08
Also published as: WO2022253272A1

Abstract

Recombinant multivalent proteins are provided having two or more angiotensin-converting enzyme 2 (ACE2) fragments and a human immunoglobin Fc domain, wherein the ACE2 fragments are capable of binding to a coronavirus. Within one embodiment the human immunoglobin Fc domain has an N-terminal flexible hinge region which is joined to the C-terminal ends of a first and a second of the two or more ACE2 fragments. Also provided are expression vectors and host cells for producing the recombinant multivalent proteins, as well as pharmaceutical compositions comprising recombinant multivalent proteins, and methods of using the same (e.g., for the treatment and/or prevention of coronavirus infections).

Description

MULTIVALENT RECOMBINANT ACE2 AND USES THEREOF

FIELD OF THE INVENTION

The present invention relates generally to blocking of SARS-CoV-2 infection with multivalent recombinant ACE2.

REFERENCE TO SEQUENCE LISTING, TABLE OR COMPUTER PROGRAM

The official copy of the Sequence Listing is submitted concurrently with the specification as an ASCII formatted text file via EFS-Web, with a file name of “VIRO414_ST25. txt” , a creation date of May 31, 2021, and a size of 28.4 KB. The Sequence Listing is part of the specification and is incorporated in its entirety by reference herein.

BACKGROUND

Humanity is facing a global COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) . Despite the growing number of effective vaccines, there exists a pressing need for COVID-19 treatment to be used in individuals who fail to develop a strong immune response against SARS-CoV-2 after vaccination or cannot get vaccinated due to medical reasons.

Recombinantly prepared antibodies have been used and/or suggested for therapeutic usage. Representative examples include GB202019709D0 entitled “Anti-Coronavirus antibodies and methods of use” , CN111620946B entitled “Isolated novel coronavirus monoclonal antibodies or antigen binding portions thereof” . However, there remains a need in the art for alternative therapeutic compositions and methods that can treat and/or prevent coronavirus infections, and which overcome one or more of the shortcomings associated with the prior art.

All of the subject matter discussed in the Background section is not necessarily prior art and should not be assumed to be prior art merely as a result of its discussion in the Background section. Along these lines, any recognition of problems in the prior art discussed in the Background section or associated with such subject matter should not be treated as prior art unless expressly stated to be prior art. Instead, the discussion of any subject matter in the Background section should be treated as part of the inventor’s approach to the particular problem, which in and of itself may also be inventive.

SUMMARY

Briefly stated, the present invention provides compositions and methods for treating and/or preventing coronavirus infections, such as SARS-CoV-1 or CoV-2 infections. Within particularly preferred embodiments of the invention soluble ACE2 receptor trap constructs are provided that have high binding affinities to the SARS-CoV-2 spike protein. For example, within one embodiment of the invention recombinant multivalent proteins are provided comprising two or more angiotensin-converting enzyme 2 (ACE2) fragments (e.g., SEQ ID NO: 1) and an antibody (e.g., a humanized immunoglobin Fc domain, SEQ ID NO: 2) , wherein the ACE2 fragments are capable of binding to a coronavirus. Within related embodiments the human immunoglobin Fc domain comprises an N-terminal flexible hinge region, and wherein the C-terminal ends of a first and a second of the two or more ACE2 fragments are joined to the N-terminal flexible hinge region of the human immunoglobin Fc domain.

Within further embodiments expression vectors are provided which comprise a nucleic acid sequence encoding the recombinant multivalent protein as disclosed herein, operably linked to a suitable promoter, as well as host cells which can contain the expression vector (and from which the recombinant multivalent protein can be expressed) .

Also provided are pharmaceutical compositions comprising the recombinant multivalent protein provided herein, as well as methods of neutralizing a coronavirus, blocking the ability of a coronavirus to infect a target cell, and for treating or preventing coronavirus infections.

This Summary has been provided to introduce certain concepts in a simplified form that are further described in detail below in the Detailed Description. Except where otherwise expressly stated, this Brief Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

The details of one or more embodiments are set forth in the description below. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Thus, any of the various embodiments described herein can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications as identified herein to provide yet further embodiments. Other features, objects and advantages will be apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary features of the present disclosure, its nature and various advantages will be apparent from the accompanying drawings and the following detailed description of various embodiments. Non-limiting and non-exhaustive embodiments are described with reference to the accompanying drawings, wherein like labels or reference numbers refer to like parts throughout the various views unless otherwise specified. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements are selected, enlarged, and positioned to improve drawing legibility. The particular shapes of the elements as drawn have been selected for ease of recognition in the drawings. One or more embodiments are described hereinafter with reference to the accompanying drawings in which.

FIG. 1A is a schematic illustration of two exemplary multivalent recombinant ACE2 protein constructs.

FIG. 1B is a schematic illustration of expression vectors encoding two exemplary multivalent recombinant ACE2 protein constructs.

FIG. 1C and 1D are gels showing restriction digest patterns of the expression vectors encoding two exemplary multivalent recombinant ACE2 protein constructs.

FIG. 2A and 2B are Western blots showing expression of two exemplary multivalent recombinant ACE2 protein constructs.

FIG. 3 is a graph showing neutralizing efficacy of two exemplary multivalent recombinant ACE2 protein constructs against SARS-CoV-2 pseudoparticles in a cell culture system.

FIG. 4A and 4B present data and a graph, respectively, showing the efficacy of one exemplary multivalent recombinant ACE2 protein construct in inhibiting SARS-CoV-2 infection of cells in culture.

FIG. 5A and 5B present data and a graph, respectively, showing the effects of one exemplary multivalent recombinant ACE2 protein construct on inhibiting cell death caused by SARS-Co-2 infection in vitro.

FIG. 6A and 6B present data and a graph, respectively, showing the toxicity of one exemplary multivalent recombinant ACE2 protein construct to mammalian cells in vitro.

FIG. 7 provides the amino acid sequence of one exemplary construct, VG3.1 (ACE2-Fc4, SEQ ID NO: 8) .

FIG. 8 provides the amino acid sequence of one exemplary construct, VG3.2 (ACE2-Fc4-ACE2, SEQ ID NO: 9) .

Corresponding reference numerals indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the present invention provides, amongst other things, compositions and methods for treating and/or preventing coronavirus infections, such as SARS-CoV-1 or CoV-2 infections, with ACE2 receptor trap constructs which have a high binding affinity to the SARS-CoV-2 spike protein.

In order to further an understanding of the various inventions provided herein, the following definitions are provided:

“Angiotensin-converting enzyme 2” , “ACE2” , is an enzyme attached to the membrane of cells located in the intestines, kidney, testis, gallbladder and heart. A coding sequence for ACE2 can comprise the entire extracellular domain of ACE2, or it may be a fragment thereof. The selected coding sequence of ACE2 can also comprise the natural sequence of ACE2, or it may be modified to contain mutations that increase affinity to SARS-CoV-2 spike protein. A list of such mutations can be found at https: //www. uniprot. org/uniprot/Q9BYF1 under the subheading “Mutagenesis” , and are listed as below.

As used herein, a "vector" refers to a nucleic acid construct for introducing a nucleic acid sequence into a cell. In some embodiments, the vector is an expression vector that is operably linked to a suitable control sequence capable of effecting the expression in a suitable host of the polypeptide encoded in a DNA sequence. In some embodiments, an "expression vector" has a promoter sequence operably linked to a DNA sequence (e.g., transgene) to drive expression in a host cell, and in some embodiments, also comprises a transcription terminator sequence.

As used herein, the term "expression" includes any step involved in the production of the polypeptide including, but not limited to, transcription, post-transcriptional modification, translation, and post-translational modification. In some embodiments, the term also encompasses secretion of the polypeptide from a cell.

As used herein, the term "produces" refers to the production of proteins and/or other compounds by cells. It is intended that the term encompass any step involved in the production of polypeptides including, but not limited to, transcription, post-transcriptional modification, translation, and post-translational modification. In some embodiments, the term also encompasses secretion of the polypeptide from a cell.

As used herein, the terms "host cell" and "host strain" refer to suitable hosts for expression vectors comprising nucleic acid sequences provided herein (e.g., the polynucleotides encoding the recombinant multivalent proteins) . In some embodiments, the host cells are prokaryotic or eukaryotic cells that have been transformed or transfected with vectors constructed using recombinant techniques as known in the art.

“Coronavirus” or “Coronaviruses” are a group of related RNA viruses in the Orthornavirae Kingdom. They are enveloped viruses that have a positive-sense single-stranded RNA genome of approximately 26-32kb. They also have characteristic club-shaped spikes that project from their surface. In humans and other animals such as birds, they cause respiratory tract infections. Mild illnesses in humans include some cases which mimic the of the common cold, while more lethal varieties can cause SARS, MERS, and COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes COVID-19 (coronavirus disease 2019) , the respiratory illness responsible for the COVID-19 pandemic.

“Antibody” refers to any protein or protein fragment derived, designed or constructed (naturally or by synthetic or recombinant means) which is based upon an immunoglobulin (e.g., IgA, IgD, IgE, IgM, or any of the various forms of IgG) . Chimeric constructs including a portion of an immunoglobulin (e.g. an IgG binding domain) fused to another polypeptide are also included within the meaning of the term “antibody” as used herein. A “humanized antibody” refers to an antibody which has had its respective fragment having amino acid residues that are substantially from a human antibody (as opposed to, for example, a mouse antibody) . Humanized antibodies can have human antibody sequences of naturally occurring human antibodies or can be consensus sequences of several human antibodies. Within certain embodiments of the invention the antibody is a humanized Fc fragment.

“Treat” or “treating” or “treatment, ” as used herein, means an approach for obtaining beneficial or desired results, including clinical results. Beneficial or desired clinical results can include, but are not limited to, alleviation or amelioration of one or more symptoms or conditions, diminishment of extent of disease, stabilized (i.e. not worsening) state of disease, preventing spread of disease, delay or slowing of disease progression, amelioration or palliation of the disease state, diminishment of the reoccurrence of disease, and remission (whether partial or total) , whether detectable or undetectable. The terms “treating” and “treatment” can also mean prolonging survival or reducing the infectious of an infected subject, as compared to an individual not receiving treatment.

The terms “prevent” , or “preventing” or “prevention” means precluding or prohibiting a disease state from developing to the point of a subject exhibiting clinical symptoms, or, from being detectable using clinical assays.

In order to further an understanding of the present invention, set forth in more detail below are sections related to: I) Recombinant Multivalent Proteins and Methods of Making such Proteins; II) Pharmaceutical Compositions and Methods of Administration; III) Examples; and IV) Various Embodiments.

I) Recombinant Multivalent Proteins and Methods of Making such Proteins

As noted above, the present invention provides recombinant multivalent proteins comprised of two or more angiotensin-converting enzyme 2 (ACE2) fragments and a humanized antibody (e.g., a humanized immunoglobin Fc domain) , wherein the ACE2 fragments are capable of binding to a coronavirus.

Briefly, entry of SARS-CoV-2 into target cells is mediated by binding of viral spike (S) protein to angiotensin-converting enzyme 2 (ACE2) on the host cell surface. The present invention provides novel soluble ACE2 receptor trap construct with binding affinity to SARS-CoV-2 spike protein that is multiple orders of magnitude greater than the current state of the art. This recombinant multivalent protein can act as a decoy and thereby neutralizes infection by a coronavirus. This receptor trap construct can also be used to neutralize SARS-CoV-1 which likewise relies on ACE2 binding.

One benefit of this strategy is the use of natural ACE2 fragments or engineered ACE2 with high similarity to the natural ACE2 receptor, thereby limiting the possibility of viral escape and enabling inhibition of infection of SARS-CoV-2 variants that can escape vaccine-induced immunity or impair therapeutic antibody targeting.

In one embodiment of the invention a recombinant multivalent protein is a Fc4-fused bivalent ACE2 construct as depicted in Figure 1A (VG3.1) , and which has an exposed ACE2 N-termini to facilitate S binding. VG3.1 is designed to interact with the S protein (as is confirmed by the binding and virus inhibition assays shown in Figures 3-5.

Similarly, the two ACE2 attached to the N-terminal region of Fc4 in the tetravalent molecule (VG3.2) depicted in Figure 1A have their N-terminal regions exposed and available for binding to S protein. However, the two additional ACE2 molecules that are attached to the C-terminal end of Fc4 via the (GS) ₃ linker (SEQ ID NO: 4) do not have their N-terminal regions readily accessible for S protein binding, thus reducing their predicted contribution to the overall interaction with SARS-CoV-2 S protein. Unexpectedly however, Figure 3 shows that VG3.2 possesses a much higher ability to inhibit SARS-CoV-2 pseudovirus infection compared to VG3.1.

Hence, within certain embodiments of the invention recombinant multivalent proteins are provided which have a significantly increased affinity to the WT receptor binding domain (RBD) of the S protein. Specifically, it has been previously shown that a dimeric ACE2-Fc that was engineered with mutations to enhance binding to spike protein can interact with the WT receptor binding domain (RBD) of S protein with an affinity of 22 nM (see Chan et al., “Engineering human ACE2 to optimize binding to the spike protein of SARS coronavirus 2” Science. 2020 Sep 4; 369 (6508) : 1261-1265. doi: 10.1126/science. abc0870. Epub 2020 Aug 4. PMID: 32753553; PMCID: PMC7574912) , while VG3.2 binds to WT RBD of the S protein with more than 20,000 times greater affinity despite lacking any mutations in ACE2 that increase binding affinity. Hence, all four ACE2 in VG3.2 contribute to binding SARS-CoV-2 S protein, and that such binding is facilitated by the unusual configuration of VG3.2. Additional tetravalent and hexavalent constructs can also be produced.

Constructs for expression of recombinant ACE2 can be generated by linking the selected coding sequence of ACE2 to that of an antibody such as human Fc4 (human Fc1 may be used as an alternative option) . The selected coding sequence of ACE2 may comprise the entire extracellular domain of ACE2, or it may be a fragment thereof. The selected coding sequence of ACE2 may comprise the natural sequence of ACE2, or it may be modified to contain mutations that increase affinity to SARS-CoV-2 spike protein. A list of such mutations can be found at https: //www. uniprot. org/uniprot/Q9BYF1 under the subheading “Mutagenesis” . The Fc4 hinge region used in VG3.1 and VG3.2 contains 3 mutations (S228P, F234A, and L235A) when compared to the wild-type human Fc4 hinge region (see Dumet et al., “Insights into the IgG heavy chain engineering patent landscape as applied to IgG4 antibody development” . MAbs. 2019 Nov-Dec; 11 (8) : 1341-1350. doi: 10.1080/19420862.2019.1664365. Epub 2019 Sep 26. Erratum in: MAbs. 2019 Nov-Dec; 11 (8) : 1. PMID: 31556789; PMCID: PMC6816381. Particularly preferred mutations include S228P, F234A and L235A. While unmodified Fc hinge region may be used as an alternative, the S228P mutation is particularly preferred when using Fc4.

The expression construct can also be comprised of any secretory signal peptide known to those skilled in the art, although the specific examples used herein utilize a secretion signal derived from human immunoglobulin heavy chain. The IS peptide (IEEQAKTFLDKFNHEAEDLFYQS) used for a hexavalent construct is a natural part of the ACE2 extracellular domain. Therefore, the IS peptide is also present in the portion of ACE2 used in the bivalent and tetravalent constructs, as shown in the annotated sequence provided in the Figures. Linkage between ACE2 and Fc is mediated by a sequence encoding the flexible (GS) _n peptide linker GGGGSGGGGSGGGGS (SEQ ID NO: 4) . Alternative linkers may be used, including GSAGSAAGSGEF (SEQ ID NO: 5) , GGSGGGSGG (SEQ ID NO: 6) , KRVAPELLGGPS (SEQ ID NO: 7) (see also, generally, Chen et al., “Fusion protein linkers: property, design and functionality” Adv Drug Deliv Rev. 2013 Oct; 65 (10) : 1357-69. doi: 10.1016/j. addr. 2012.09.039. Epub 2012 Sep 29. PMID: 23026637; PMCID: PMC3726540) .

If multiple linkers are used in one construct, the linkers do not have to be identical to each other. The choice of peptide linker will depend upon the ability of the linker to maximize the structural flexibility of the ACE2 construct necessary for binding the SARS-CoV-2 spike protein, while maintaining a functional conformation. The recombinant ACE2 construct sequences are cloned into a suitable vector such as pcDNA3.1 or pET22b for expression and purification. A wide variety of suitable vectors are available and known to those skilled in the art.

II) Pharmaceutical Compositions and Methods of Administration

Therapeutic compositions are provided that may be used to prevent, treat, or ameliorate the effects of a coronavirus infection. More particularly, therapeutic compositions are provided comprising recombinant multivalent protein as described herein. In certain embodiments, the compositions will further comprise a pharmaceutically acceptable carrier. The phrase “pharmaceutically acceptable carrier” is meant to encompass any carrier, diluent or excipient that does not interfere with the effectiveness of the biological activity of the oncolytic virus and that is not toxic to the subject to whom it is administered (see generally Remington: The Science and Practice of Pharmacy, Lippincott Williams &Wilkins; 21st ed. (May 1, 2005 and in The United States PharmacopE1A: The National Formulary (USP 40 –NF 35 and Supplements) .

In the case of recombinant multivalent proteins as described herein, non-limiting examples of suitable pharmaceutical carriers include phosphate buffered saline solutions, water, emulsions (such as oil /water emulsions) , various types of wetting agents, sterile solutions, and others. Such carriers can be formulated by conventional methods and can be administered to the subject at an effective dose. Additional pharmaceutically acceptable excipients include, but are not limited to, water, saline, polyethylene glycol, hyaluronic acid and ethanol. Pharmaceutically acceptable salts can also be included therein, e.g., mineral acid salts (such as hydrochlorides, hydrobromides, phosphates, sulfates, and the like) and the salts of organic acids (such as acetates, propionates, malonates, benzoates, and the like) .

Within preferred embodiments of the invention, the therapeutic composition is provided in a soluble form suitable for parenteral administration (e.g., intravenously, intramuscularly, or by a nasal spray) , or, enterally (e.g., orally) .

The compositions may be stored at a temperature conducive to stable shelf-life and includes room temperature (about 20℃) , 4℃, -20℃, -80℃, and in liquid N2. Because compositions intended for use in vivo generally don’ t have preservatives, storage will generally be at colder temperatures. Compositions may be stored dry (e.g., lyophilized) or in liquid form.

Within further embodiments of the invention, the therapeutic composition are used to treat or prevent a coronavirus infection, comprising the step of administering to a subject in need thereof an effective dose of a recombinant multivalent protein as described herein.

The terms “effective dose” and “effective amount” refers to amounts of the recombinant multivalent protein as described herein that is sufficient to effect treatment or prevention of a coronavirus infection. Effective amounts may vary according to factors such as the subject’s disease state, age, gender, and weight, as well as the pharmaceutical formulation, the route of administration, and the like, but can nevertheless be routinely determined by one skilled in the art.

The recombinant multivalent proteins described herein may be given by a route that is parenteral (e.g., intravenously, intramuscularly, or by a nasal spray) , or, enterally (e.g., orally) .

The optimal or appropriate dosage regimen of the recombinant multivalent protein is readily determinable within the skill of the art, by the attending physician based on patient data, patient observations, and various clinical factors, including for example a subject’s size, body surface area, age, gender, degree of severity of the illness, the general health of the patient, and other drug therapies to which the patient is being subjected.

A therapeutically effective amount is preferably administered. This is an amount that is sufficient to show benefit to the subject. The actual amount administered and time-course of administration will depend at least in part on the nature of the corornavirus infection, the condition of the subject, site of delivery, and other factors.

Within one embodiment of the invention the therapeutic compositions provided herein can be delivered by inhalation, e.g., by use of a device that can create or deliver small particles that can get into the lung. Larger particle sizes (e.g., greater than about 10 um) tend to be deposited in the upper respiratory tract, and smaller particles (e.g., less than about 0.5 um tend to be exhaled. Hence, within certain embodiments of the invention the particles are less than about 10 um in average size, but greater than about 0.5um in average size. Within other embodiments of the invention the particles can range in average size from about 0.5, to 5 um in size (including subsets of this range, e.g., from about 3 to 5 um in size.

Representative examples of inhalation therapy, as well as the pharmacodynamics, pharmacokinetics, manufacture and formulation, and other methods and devices related to the delivery of therapeutic compositions to the respiratory tract are described in: “Pharmaceutical Inhalation Aerosol Technology” , Hickey and R. P. da Rocha (eds. ) , Third Ed., CRC Press, Boca Raton, Florida, 2019, ISBN 9780429055201; Gardenhire et al., “A Guide to Aerosol Delivery Devices for Respiratory Therapists” 3rd Edition, American Association for Respiratory Care, 2013; “Optimization of Aerosol Drug Delivery” , Gradoń and Marijnissen (eds. ) , Springer Science, 2003, ISBN 978-90-481-6436-3; “Advances in Delivery Science and Technology: Controlled Pulmonary Drug Delivery” , Smyth and Hickey (eds. ) , Springer 2011, ISBN 978-1-4419-9745-6; “Pulmonary Drug Delivery, Advances and Challenges” , Nokhodchi and Martin (eds. ) , John Wiley and Sons Ltd., 2015; ISBN 978-1-118-79954-3; US Patent Nos. 4,334,531, 5,355,872, 6,435,175, 6,772,754, 7,677,467, 9,744,313, and 10,029,055; US Patent Application Pub. Nos. 2008/0010452, 2016/0121058, 2017/0368295, 2018/0015240; International Publication No. WO2009/061541; and European Patent No. 0118478 B1; all of the above of which are incorporated by reference in their entirety.

Representative examples of commercially available delivery devices include nebulizers (e.g., small-volume nebulizers, jet nebulizers, pneumatic compressor nebulizers, ultrasonic nebulizers, vibrating mesh/horn nebulizers and microprocessor-controlled breath-actuated nebulizers) ; pressurized metered-dose inhalers, and dry-powder inhalers. Commercially available examples include PARI LC, Sidestream Plus, Hudson T Up-draft II, Marquest ACORN II, DURABLE SIDESTREAM, PARI BABY, Marquest Respirgard II, I-neb Adaptive Aerosol (AAD) System, ALTERA nebulizer system and TYVASO inhalation system.

III) Examples

The Examples and preparations provided below further illustrate and exemplify the compounds of the present invention and methods of preparing such compounds. It is to be understood that the scope of the present invention is not limited in any way by the scope of the following Examples and preparations. In the following Examples, molecules with a single chiral center, unless otherwise noted, exist as a racemic mixture. Those molecules with two or more chiral centers, unless otherwise noted, exist as a racemic mixture of diastereomers. Single enantiomers/diastereomers may be obtained by methods known to those skilled in the art. The starting materials and various reactants utilized or referenced in the examples may be obtained from commercial sources, or are readily prepared from commercially available organic compounds, using methods well-known to one skilled in the art.

Example 1

Design and Expression Cloning of Multivalent Recombinant ACE2 Protein Constructs

This example describes the design and expression cloning of two exemplary multivalent protein constructs engineered to target the SARS-CoV-2 coronavirus and inhibit binding of the virus to target cells.

Expression vector cloning.

The structures of two exemplary multivalent recombinant ACE2 protein constructs, VG3.1 and VG3.2, are depicted in Fig. 1A. These constructs are generated by linking two or more fragments of ACE2 to a human Fc domain. The fragment of ACE2 may include the entire extracellular domain (e.g., the n-terminal domain) of ACE2, or a fragment thereof. In this Example, the VG3.1 construct is bivalent for ACE2 (e.g., includes two ACE2 fragments) , while the VG3.2 construct is tetravalent for ACE2 (e.g., includes four ACE2 fragments) . The human Fc domain used in this Example is the human Fc4 domain with mutations in the hinge region that enhance stability and reduce aggregation (S228P) and eliminate Fc effector function (F234A and L235A) . The VG3.1 construct is designed such that the N-terminal ends of both ACE2 fragments are free and exposed to solution, while the C-terminal ends are joined to the N-terminus of the Fc4 fragment. The VG3.2 construct is constructed such that the additional third and fourth ACE2 fragments are joined to the Fc4 fragments at their N-terminal ends, and are therefore in opposite orientations relative to the first and second ACE2 fragments. The VG3.2 construct further includes a flexible peptide linker joining the third and fourth ACE2 fragments to the Fc4 domain.

To generate expression plasmids encoding the multivalent VG3.1 and VG3.2 protein constructs, the DNA sequences encoding VG3.1 and VG3.2 protein were individually cloned into pCHO 1.0 vectors using restriction enzymes, AvrII and BstZ17I, resulting in plasmids pCHO1.0-VG3.1 and pCHO1.0-VG3.2. The 5’ end of the expression constructs also included DNA fragments encoding the secretory signals derived from the human immunoglobin heavy chain (SEQ ID NO: 3) . The structures of these two expression plasmids are depicted in Fig. 1B.

The successful insertion of the expression cassettes was confirmed by restriction digest with AvrII-BstZ17I and sanger sequencing. Figs. 1C and 1D show the results of agarose gel electrophoresis using plasmid DNA digested with BstZ17I or double-digested with AvrII-BstZ17I. All DNA fragments displayed the expected molecular weight.

Example 2

Expression of Multivalent Recombinant ACE2 Protein Constructs

To test the expression of VG3.1 and VG3.2 protein constructs in mammalian cells, pCHO1.0-VG3.1 and pCHO1.0-VG3.2 plasmids were transfected to HEK293T cells with lipofectamine 3000. Cell lysates were prepared and analyzed by Western Blotting assay to detect VG3.1 and VG3.2 proteins using antibodies against ACE-2 and hFc. Results are presented in Fig. 2 which shows that both VG3.1 and VG3.2 were detected by antibodies against ACE-2 (Fig. 2A) and hFc (Fig. 2B) . Both ACE-2 multivalent protein constructs migrated in the gel at the expected molecular weight.

Example 3

Purification of Multivalent Recombinant ACE2 Protein Constructs

The ExpiCHO ^TM Expression System was used to express VG3.1 and VG3.2 proteins in CHO cells. Briefly, pCHO1.0-VG3.1 and pCHO1.0-VG3.2 were transfected to cells with ExpiFectamine ^TM CHO Reagent. The transfected cells were cultured for 2-4 days at 32℃, 120 rpm, with 5%CO ₂. Cell culture medium was collected and clarified by centrifugation. After passing through a 0.22 um filter, culture medium was used for VG3.1 and VG3.2 protein purification. Protein A was used in the initial capture step, followed by washing and elution. The eluted protein was maintained in PBS buffer at 4℃.

Example 4

Pseudoparticle Neutralization Test

To test the neutralizing efficacy of VG3.1 and VG3.2 against the SARS CoV-2 virus, SARS-CoV pseudoparticles expressing the luciferase reporter were incubated with purified VG3.1 or VG3.2 protein constructs. Pseudoparticles co-incubated with gradient concentrations of VG3.1 or VG3.2 protein were subsequently used to infect Huh-7 cells in 96-well plates. The infected cells were cultured at 37℃ with 5%CO ₂ to allow for luciferase expression. Cell lysates were prepared and subjected to a luciferase assay to determine the expression level of the reporter protein. The results of this experiment are presented in Fig. 3, which indicates that both VG3.1 and VG3.2 protein completely neutralize the SARS-CoV pseudoparticle at 316 μg/ml and 1 ug/ml, respectively. The half maximal inhibitory concentration, IC ₅₀, were calculated using the Reed-Muench method. The IC ₅₀ of VG3.1 and VG3.2 were determined to be 5.85 μg/ml and 0.04 μg/ml, respectively.

Example 5

SARS-Cov-2 Neutralization Assay

The efficacy of the VG3.2 protein construct in inhibiting SARS-CoV infection was analyzed in a cell culture system with the SARS-CoV-2 virus and Vero cells. The virus was pre-incubated with a gradient concentration of purified VG3.2 protein. Vero cells were plated in 96-well plates and then infected with virus at a MOI of 0.1. The viral content of cellular supernatant was determined by RT-PCR at 48 hr post infection. Results indicated that the IC ₅₀ of VG3.2 protein in inhibition of SARS-CoV-2 infection was 6.1ng/mL (see Fig. 4A and 4B) . At 3 days post infection, the viability of Vero cells was determined using a commercially available Cell Counting Kit-8 (CCK8) . Results of this experiment are shown in Figs. 5A and 5B, which indicate that the IC ₅₀ of VG3.2 in inhibiting SARS-CoV-2-induced cell death was 0.95 μg/mL.

Example 6

Cytotoxicity of the VG3.2 Protein Construct on Vero Cells

To determine the toxicity of the VG3.2 protein on mammalian cells, Vero cells were plated in a 96-well plate. Cells were then treated with a gradient concentration of purified VG3.2 protein. At 3 days post-treatment, cell viability was determined with a CCK8 Kit. The half cytotoxic concentration (CC ₅₀) of VG3.2 protein was calculated and determined to be over 500 μg/mL (see Figs. 6A and 6B) .

Example 7

Affinity characterization

An Onctet RED96e System was adopted to characterize the affinity of VG3.2 to SARS-CoV-2 spike protein (Sprotein) . Tested S proteins were receptor binding domains (RBD) of lineage 2019-nCoV, South Africa variant (B. 1.351) , Brazil variant (P. 1) , UK variant (B1.1.7) and full-length S protein of UK variant (B1.1.7) . Above proteins with gradient concentrations were mixed with VG3.2 in a 96-well black-wall plate. On rate (Ka) and off rate (Kd) were matured with an Onctet RED96e System. The equilibrium dissociation constant (KD) between VG3.2 and S proteins were calculated accordingly. Results showed that all tested proteins had high affinity with VG3.2 and lineage 2019-nCoV RBD showed strongest interaction with VG3.2 among tested proteins (Table 1) .

Table 1. Affinity of VG3.2 to SARS-CoV-2 spike proteins

Example 8

Protein Complex Co-Crystallization Analysis

The avidity between the VG3.1 or VG3.2 protein constructs and ligand proteins may be analyzed by co-crystallization followed by X-ray crystal analysis. A list of SARS-CoV-2 spike protein ligands is listed in table 1. Briefly, purified VG3.1 or VG3.2 protein is mixed with each of the tested spike proteins and subjected to standard crystallization procedures. The final structures are imaged by X-ray analysis.

Table 2: SARS-CoV-2 spike proteins

The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

The following are some exemplary numbered embodiments of the present disclosure.

It is also to be understood that as used herein and in the appended claims, the singular forms “a, ” “an, ” and “the” include plural reference unless the context clearly dictates otherwise, the term “X and/or Y” means “X” or “Y” or both “X” and “Y” , and the letter “s” following a noun designates both the plural and singular forms of that noun. In addition, where features or aspects of the invention are described in terms of Markush groups, it is intended, and those skilled in the art will recognize, that the invention embraces and is also thereby described in terms of any individual member and any subgroup of members of the Markush group, and Applicants reserve the right to revise the application or claims to refer specifically to any individual member or any subgroup of members of the Markush group.

It is to be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting. It is further to be understood that unless specifically defined herein, the terminology used herein is to be given its traditional meaning as known in the relevant art.

Reference throughout this specification to “one embodiment” or “an embodiment” and variations thereof means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

IV) Additional Embodiments

1. A recombinant multivalent protein comprising two or more angiotensin-converting enzyme 2 (ACE2) fragments and a linker such as an antibody (e.g., a human immunoglobin Fc domain) , wherein said ACE2 fragments are capable of binding to a coronavirus.

2. The recombinant multivalent protein of embodiment 1, wherein said human immunoglobin Fc domain comprises an N-terminal flexible hinge region, and wherein the C-terminal ends of a first and a second of the two or more ACE2 fragments are joined to the N-terminal flexible hinge region of the human immunoglobin Fc domain.

3. The recombinant multivalent protein of embodiment 1, wherein the first and the second of the two or more ACE2 fragments each comprise an extracellular N-terminal domain of the native ACE2 protein, or a fragment thereof.

4. The recombinant multivalent protein of embodiment 1, wherein the first and the second of the two or more ACE2 fragments each comprise one or more mutations that increase binding affinity to a coronavirus.

5. The recombinant multivalent protein of embodiment 1 comprising four or more ACE2 fragments, wherein the N-terminal ends of a third and a fourth of the four or more ACE2 fragments are joined to the C-terminal end of the Fc domain.

6. The recombinant multivalent protein of embodiment 5, wherein the N-terminal ends of the third and the fourth ACE fragments are joined to the C-terminal end of Fc domain by a flexible linker peptide.

7. The recombinant multivalent protein of embodiment 2, wherein the flexible hinge region is a peptide selected from the group consisting of GGGGSGGGGSGGGGS, GSAGSAAGSGEF, GGSGGGSGG, and KRVAPELLGGPS.

8. The recombinant multivalent protein of embodiment 2, wherein the hinge region of the human immunoglobin Fc domain comprises at least one mutation selected from the group consisting of S228P, F234A, and L235A. Within various embodiments of the above, a recombinant multivalent protein is provided with the amino acid sequence comprising the sequence set forth in FIG. 7. Within yet other embodiments a recombinant multivalent protein is provided with the amino acid sequence comprising the sequence set forth in FIG. 8. Within preferred embodiments of any one of embodiments 1-8 a recombinant multivalent protein is provided which is soluble and/or sterile.

9. An expression vector comprising a nucleic acid sequence encoding the recombinant multivalent protein of any of embodiments 1 –8 operably linked to a suitable promoter.

10. The expression vector of embodiment 9, wherein the nucleic acid sequence encoding the recombinant multivalent protein construct of any of embodiments 1 –8 comprises a nucleic acid sequence encoding a secretory signal, wherein the secretory signal is operably linked to the soluble recombinant multivalent protein construct.

11. The expression vector of embodiment 10, wherein the secretory signal comprises a protein fragment derived from the human immunoglobin heavy chain. Within other aspects of the invention, host cells are provided which contain an expression vector according to any one of embodiments 9-11, as well as methods for producing the recombinant multivalent protein constructs utilizing the expression vector containing host cells.

12. A pharmaceutical composition comprising the recombinant multivalent protein of any of embodiments 1 –8 and an a pharmaceutically acceptable excipient or buffer.

13. A method of neutralizing a coronavirus comprising contacting the coronavirus with an effective dose of the composition of embodiment 12.

14. A method of blocking the ability of a coronavirus to infect a target cell comprising administering to the target cell an effective dose of the composition of embodiment 12, wherein the effective dose is capable of neutralizing the coronavirus.

15. The method of embodiment 13 or 14, wherein the coronavirus is SARS-CoV-2.

16. A method of treating or preventing a coronavirus infection in a patient, comprising administering to the patient a therapeutically effective dose of the composition of embodiment 12. Within various embodiments of the invention the therapeutically effective dose is administered parenterally (e.g., intravenously, intramuscularly, or by a nasal spray) . Within other embodiments of the invention the therapeutically effective dose is administered enterally (e.g., orally) . Within certain embodiments the coronavirus infection can be caused by SARS-CoV-1, or, SARS-CoV-2 virus.

17. A method for detecting the presence of coronavirus (SARS-CoV-2) , comprising the step admixing a composition according to any one of embodiments 1-8 with a sample to be tested, and determining whether said composition had bound a coronavirus.

As used in this specification and the appended claims, the singular forms “a, ” “an, ” and “the” include plural referents, i.e., one or more, unless the content and context clearly dictates otherwise. It should also be noted that the conjunctive terms, “and” and “or” are generally employed in the broadest sense to include “and/or” unless the content and context clearly dictates inclusivity or exclusivity as the case may be. Thus, the use of the alternative (e.g., "or" ) should be understood to mean either one, both, or any combination thereof of the alternatives. In addition, the composition of “and” and “or” when recited herein as “and/or” is intended to encompass an embodiment that includes all of the associated items or ideas and one or more other alternative embodiments that include fewer than all of the associated items or ideas.

Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and synonyms and variants thereof such as “have” and “include” , as well as variations thereof such as “comprises” and “comprising” are to be construed in an open, inclusive sense, e.g., “including, but not limited to. ” The term "consisting essentially of" limits the scope of a claim to the specified materials or steps, or to those that do not materially affect the basic and novel characteristics of the claimed invention.

Any headings used within this document are only being utilized to expedite its review by the reader, and should not be construed as limiting the invention or claims in any manner. Thus, the headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

Where a range of values is provided herein, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

For example, any concentration range, percentage range, ratio range, or integer range provided herein is to be understood to include the value of any integer within the recited range and, when appropriate, fractions thereof (such as one tenth and one hundredth of an integer) , unless otherwise indicated. Also, any number range recited herein relating to any physical feature, such as polymer subunits, size or thickness, are to be understood to include any integer within the recited range, unless otherwise indicated. As used herein, the term "about" means ± 20%of the indicated range, value, or structure, unless otherwise indicated.

All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. Such documents may be incorporated by reference for the purpose of describing and disclosing, for example, materials and methodologies described in the publications, which might be used in connection with the presently described invention. The publications discussed above and throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate any referenced publication by virtue of prior invention.

All patents, publications, scientific articles, web sites, and other documents and materials referenced or mentioned herein are indicative of the levels of skill of those skilled in the art to which the invention pertains, and each such referenced document and material is hereby incorporated by reference to the same extent as if it had been incorporated by reference in its entirety individually or set forth herein in its entirety. Applicants reserve the right to physically incorporate into this specification any and all materials and information from any such patents, publications, scientific articles, web sites, electronically available information, and other referenced materials or documents.

In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Furthermore, the written description portion of this patent includes all claims. Furthermore, all claims, including all original claims as well as all claims from any and all priority documents, are hereby incorporated by reference in their entirety into the written description portion of the specification, and Applicants reserve the right to physically incorporate into the written description or any other portion of the application, any and all such claims. Thus, for example, under no circumstances may the patent be interpreted as allegedly not providing a written description for a claim on the assertion that the precise wording of the claim is not set forth in haec verba in written description portion of the patent.

The claims will be interpreted according to law. However, and notwithstanding the alleged or perceived ease or difficulty of interpreting any claim or portion thereof, under no circumstances may any adjustment or amendment of a claim or any portion thereof during prosecution of the application or applications leading to this patent be interpreted as having forfeited any right to any and all equivalents thereof that do not form a part of the prior art.

Other nonlimiting embodiments are within the following claims. The patent may not be interpreted to be limited to the specific examples or nonlimiting embodiments or methods specifically and/or expressly disclosed herein. Under no circumstances may the patent be interpreted to be limited by any statement made by any Examiner or any other official or employee of the Patent and Trademark Office unless such statement is specifically and without qualification or reservation expressly adopted in a responsive writing by Applicants.

Claims

A recombinant multivalent protein comprising two or more angiotensin-converting enzyme 2 (ACE2) fragments and an antibody (such as a humanized immunoglobin Fc domain) , wherein said ACE2 fragments are capable of binding to a coronavirus.
The recombinant multivalent protein of claim 1, wherein said human immunoglobin Fc domain comprises an N-terminal flexible hinge region, and wherein the C-terminal ends of a first and a second of the two or more ACE2 fragments are joined to the N-terminal flexible hinge region of the human immunoglobin Fc domain.
The recombinant multivalent protein of claim 1, wherein the first and the second of the two or more ACE2 fragments each comprise an extracellular N-terminal domain of the native ACE2 protein, or a fragment thereof.
The recombinant multivalent protein of claim 1, wherein the first and the second of the two or more ACE2 fragments each comprise one or more mutations that increase binding affinity to a coronavirus.
The recombinant multivalent protein of claim 1 comprising four or more ACE2 fragments, wherein the N-terminal ends of a third and a fourth of the four or more ACE2 fragments are joined to the C-terminal end of the Fc domain.
The recombinant multivalent protein of claim 5, wherein the N-terminal ends of the third and the fourth ACE fragments are joined to the C-terminal end of Fc domain by a flexible linker peptide.
The recombinant multivalent protein of claim 2, wherein the flexible hinge region is a peptide selected from the group consisting of GGGGSGGGGSGGGGS, GSAGSAAGSGEF, GGSGGGSGG, and KRVAPELLGGPS.
The recombinant multivalent protein of claim 2, wherein the hinge region of the human immunoglobin Fc domain comprises at least one mutation selected from the group consisting of S228P, F234A, and L235A.
An expression vector comprising a nucleic acid sequence encoding the recombinant multivalent protein of any of claims 1 –8 operably linked to a suitable promoter.
The expression vector of claim 9, wherein the nucleic acid sequence encoding the recombinant multivalent protein construct of any of claims 1 –8 comprises a nucleic acid sequence encoding a secretory signal, wherein the secretory signal is operably linked to the soluble recombinant multivalent protein construct.
The expression vector of claim 10, wherein the secretory signal comprises a protein fragment derived from the human immunoglobin heavy chain.
A pharmaceutical composition comprising the recombinant multivalent protein of any of claims 1 –8 and an a pharmaceutically acceptable excipient or buffer.
A method of neutralizing a coronavirus comprising contacting the coronavirus with an effective dose of the composition of claim 12.
A method of blocking the ability of a coronavirus to infect a target cell comprising administering to the target cell an effective dose of the composition of claim 12, wherein the effective dose is capable of neutralizing the coronavirus.
The method of claim 13 or 14, wherein the coronavirus is SARS-CoV-2.
A method of treating or preventing a coronavirus infection in a patient, comprising administering to the patient a therapeutically effective dose of the composition of claim 12.