An inhaled ACE2 decoy confers protection against SARS-CoV-2 infection in preclinical models

Engineered ACE2 decoy in dry powder form for inhalation: A novel therapy for SARS-CoV-2 variants

The persistent threat of SARS-CoV-2 and the emergence of new variants has prompted the development of a novel, easily administered modality that can overcome viral mutations. The engineered ACE2 decoy shows neutralizing activity comparable to monoclonal antibodies and is broadly effective against SARS-CoV-2 variants and ACE2-utilizing sarbecoviruses. In addition to intravenous administration, this decoy has shown antiviral efficacy through nebulized aerosol inhalation in murine and primate models, offering a dose-sparing advantage. Clinically, dry powder formulation is ideal for convenience and storage but poses challenges for protein biologics. This study developed a freeze-dried spray formulation of the ACE2 decoy for inhalation. The trehalose and leucine-based excipient maintained neutralizing activity and prevented aggregate formation. The dry powder showed aerodynamic distribution from bronchi to alveoli, aiding protection against SARS-CoV-2 infections. Neutralizing activity, structural stability, and powder dispersibility were preserved after 6 months of storage. In a mouse model of SARS-CoV-2 infection, significant reductions in viral replication and lung pathology were observed with intratracheal administration 24 h post-infection. The ACE2 decoy retained activity against recent JN.1 and current KP.3 strains, confirming its robust efficacy against viral mutations. This ACE2 decoy powder inhalant is a self-administered, next-generation treatment addressing the ongoing immune-evading evolution of SARS-CoV-2.

In vivo production of engineered ACE2 decoy protects lungs from SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants repeatedly evade the immune system within short periods. Thus, next-generation therapeutics that are resistant to mutations and can be rapidly supplied to individuals in an emergency are required. Here, we designed an mRNA encoding an engineered angiotensin-converting enzyme 2 (ACE2) decoy, 3N39v4, composed of high-affinity ACE2 and a human immunoglobulin G Fc domain. The 3N39v4-encoded mRNA was encapsulated in lipid nanoparticles for efficient in vivo delivery. Systemic delivery of mRNA in mice resulted in a dose-dependent expression of 3N39v4 in plasma (20-261 μg/mL at 1-10 mg/kg) with sufficient tolerability. An improved pharmacokinetic profile of the produced protein was compared to injection of the 3N39v4 protein. In vivo-expressed 3N39v4 exhibited broad neutralization against nine SARS-CoV-2 variants and other sarbecoviruses, including the currently circulating Omicron subvariants JN.1 and BA.2.86. A single intravenous injection of 3N39v4-encoded mRNA resulted in a robust, dose-dependent improvement in the outcomes of mice infected with SARS-CoV-2. The mRNA treatment in monkeys produced 3N39v4 in sera, which inhibited the replication of the authentic viruses. The rapid development of mRNA drugs highlights the potential of mRNA-encoded ACE2 decoys in emergencies to combat diverse SARS-CoV-2 variants, including future variants.

Development of Stable, Maleimide-Functionalized Peptidoliposomes Against SARS-CoV-2

Throughout the last 5 years, extensive research has been carried out towards the development of effective treatments for coronavirus disease 2019 (COVID-19). Regardless of the worldwide efforts, only a few drugs have passed clinical trials, and there is still a need to develop therapies, especially for those who are particularly vulnerable to a severe disease course. Maleimide-functionalized liposomes are proposed to serve as a platform for the immobilization, stabilization, and delivery of a short peptide sequence with high affinity towards severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, extensive optimizations should be performed in order to achieve features required for a reliable drug candidate, such as homogeneity of physical parameters and their long-term stability. Here, we present a step-by-step development process for maleimide-functionalized liposomes, which-once decorated with the SARS-CoV-2-binding peptide-could inhibit the infection progress of COVID-19. The main emphasis is placed on defining optimal lipid composition and formation conditions of PEGylated liposomes. We propose that the developed nanocarrier technology can be used as a universal platform for the construction of multiple antiviral agents.

ACE2, From the Kidney to SARS-CoV-2: Donald Seldin Award Lecture 2023

ACE2 (angiotensin-converting enzyme 2) is a monocarboxypeptidase that cleaves Ang II (angiotensin II) among other substrates. ACE2 is present in the cell membrane of many organs, most abundantly in epithelial cells of kidney proximal tubules and the small intestine, and also exists in soluble forms in plasma and body fluids. Membrane-bound ACE2 exerts a renoprotective action by metabolizing Ang II and therefore attenuating the undesirable actions of excess Ang II. Therefore, soluble ACE2, by downregulating this peptide, may exert a therapeutic action. Our laboratory has designed ACE2 truncates that pass the glomerular filtration barrier to target the kidney renin-angiotensin system directly and, therefore, compensate for loss of kidney membrane-bound ACE2. Membrane-bound ACE2 is also the essential receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Soluble ACE2 proteins have been studied as a way to intercept SARS-CoV-2 from binding to membrane-bound ACE2 and prevent cell entry of SARS-CoV-2 altogether. We bioengineered a soluble ACE2 protein, termed ACE2 618-DDC-ABD, with increased binding affinity for SARS-CoV-2 and prolonged duration of action, which, when administered intranasally, provides near-complete protection from lethality in k18hACE2 mice infected with different SARS-CoV-2 variants. The main advantage of soluble ACE2 proteins for the neutralization of SARS-CoV-2 is their immediate onset of action and universality for current and future emerging SARS-CoV-2 variants. It is notable that ACE2 is critically involved in 2 dissimilar functions: as a receptor for cell entry of many coronaviruses and as an enzyme in the metabolism of Ang II, and yet in both cases, it is a therapeutic target.

Applications of Cell-Based Protein Array Technology to Preclinical Safety Assessment of Biological Products

Off-target evaluation is essential in preclinical safety assessments of novel biotherapeutics, supporting lead molecule selection, endpoint selection in toxicology studies, and regulatory requirements for first-in-human trials. Off-target interaction of a therapeutic antibody and antibody derivatives has been historically assessed via the Tissue Cross-Reactivity (TCR) study, in which the candidate molecule is used as a reagent in immunohistochemistry (IHC) to assess binding of the candidate molecule to a panel of human tissue sections. The TCR approach is limited by the performance of the therapeutic as an IHC reagent, which is often suboptimal to outright infeasible. Furthermore, binding of the therapeutic in IHC conditions typically has poor in vitro to in vivo translation and lacks qualitative data of the identity of putative off-targets limiting the decisional value of the data. More recently, cell-based protein arrays (CBPA) that allow for screening against a large portion of the human membrane proteome and secretome have emerged as a complement, and likely a higher value alternative, to IHC-based off-target assessment. These arrays identify specific protein interactions and may be useful for testing nontraditional antibody-based therapeutic formats that are unsuitable for TCR studies. This article presents an overview of CBPA technologies in the context of TCR and off-target assessment studies. Selected case examples and strategic considerations covering a range of different modalities are presented.

Broad Neutralization Capacity of an Engineered Thermostable Three-Helix Angiotensin-Converting Enzyme 2 Polypeptide Targeting the Receptor-Binding Domain of SARS-CoV-2

The mutational drift of SARS-CoV-2 and the appearance of multiple variants, including the latest Omicron variant and its sub-lineages, has significantly reduced (and in some cases abolished) the protective efficacy of Wuhan spike-antigen-based vaccines and therapeutic antibodies. One of the most functionally constrained and thus largely invariable regions of the spike protein is the one involved in the interaction with the ACE2 receptor mediating the cellular entry of SARS-CoV-2. Engineered ACE2, both as a full-length protein or as an engineered polypeptide fragment, has been shown to be capable of preventing the host-cell binding of all viral variants and to be endowed with potent SARS-CoV-2 neutralization activity both in vitro and in vivo. Here, we report on the biochemical and antiviral properties of rationally designed ACE2 N-terminal, three-helix fragments that retain a native-like conformation. One of these fragments, designated as PRP8_3H and produced in recombinant form, bears structure-stabilizing and binding-affinity enhancing mutations in α-helix-I and in both α-helix I and II, respectively. While the native-like, unmodified three α-helices ACE2 fragment proved to be thermally unstable and without any detectable pseudovirion neutralization capacity, PRP8_3H was found to be highly thermostable and capable of binding to the SARS-CoV-2 spike receptor-binding domain with nanomolar affinity and to neutralize both Wuhan and Omicron spike-expressing pseudovirions at (sub)micromolar concentrations. PRP8_3H thus lends itself as a highly promising ACE2 decoy prototype suitable for a variety of formulations and prophylactic applications.

In Silico Design of miniACE2 Decoys with In Vitro Enhanced Neutralization Activity against SARS-CoV-2, Encompassing Omicron Subvariants

The COVID-19 pandemic has overwhelmed healthcare systems and triggered global economic downturns. While vaccines have reduced the lethality rate of SARS-CoV-2 to 0.9% as of October 2024, the continuous evolution of variants remains a significant public health challenge. Next-generation medical therapies offer hope in addressing this threat, especially for immunocompromised individuals who experience prolonged infections and severe illnesses, contributing to viral evolution. These cases increase the risk of new variants emerging. This study explores miniACE2 decoys as a novel strategy to counteract SARS-CoV-2 variants. Using in silico design and molecular dynamics, blocking proteins (BPs) were developed with stronger binding affinity for the receptor-binding domain of multiple variants than naturally soluble human ACE2. The BPs were expressed in E. coli and tested in vitro, showing promising neutralizing effects. Notably, miniACE2 BP9 exhibited an average IC50 of 4.9 µg/mL across several variants, including the Wuhan strain, Mu, Omicron BA.1, and BA.2 This low IC50 demonstrates the potent neutralizing ability of BP9, indicating its efficacy at low concentrations.Based on these findings, BP9 has emerged as a promising therapeutic candidate for combating SARS-CoV-2 and its evolving variants, thereby positioning it as a potential emergency biopharmaceutical.

SARS-CoV-2 evolution has increased resistance to monoclonal antibodies and first-generation COVID-19 vaccines: Is there a future therapeutic role for soluble ACE2 receptors for COVID-19?

COVID-19 has caused calamitous health, economic and societal consequences. Although several COVID-19 vaccines have received full authorization for use, global deployment has faced political, financial and logistical challenges. The efficacy of first-generation COVID-19 vaccines is waning and breakthrough infections are allowing ongoing transmission and evolution of SARS-CoV-2. Furthermore, COVID-19 vaccine efficacy relies on a functional immune system. Despite receiving three primary doses and three or more heterologous boosters, some immunocompromised patients may not be adequately protected by COVID-19 vaccines and remain vulnerable to severe disease. The evolution of new SARS-CoV-2 variants has also resulted in the rapid obsolescence of monoclonal antibodies. Convalescent plasma from COVID-19 survivors has produced inconsistent results. New drugs such as Paxlovid (nirmatrelvir/ritonavir) are beyond the reach of low- and middle-income countries. With widespread use of Paxlovid, it is likely nirmatrelvir-resistant clades of SARS-CoV-2 will emerge in the future. There is thus an urgent need for new effective anti-SARS-CoV-2 treatments. The in vitro efficacy of soluble ACE2 against multiple SARS-CoV-2 variants including omicron (B.1.1.529), was recently described using a competitive ELISA assay as a surrogate marker for virus neutralization. This indicates soluble wild-type ACE2 receptors are likely to be resistant to viral evolution. Nasal and inhaled treatment with soluble ACE2 receptors has abrogated severe disease in animal models of COVID-19. There is an urgent need for clinical trials of this new class of antiviral therapeutics, which could complement vaccines and Paxlovid.

ACE2 decoy Fc-fusions and bi-specific killer engager (BiKEs) require Fc engagement for in vivo efficacy against SARS-CoV-2

SARS-CoV-2 virus has continued to evolve over time necessitating the adaptation of vaccines to maintain efficacy. Monoclonal antibodies (mAbs) against SARS-CoV-2 were a key line of defense for unvaccinated or immunocompromised individuals. However, these mAbs are now ineffective against current SARS-CoV-2 variants. Here, we tested three aspects of αSARS-CoV-2 therapeutics. First, we tested whether Fc engagement is necessary for in vivo clearance of SARS-CoV-2. Secondly, we tested bi-specific killer engagers (BiKEs) that simultaneously engage SARS-CoV-2 and a specific Fc receptor. Benefits of these engagers include the ease of manufacturing, stability, more cell-specific targeting, and high affinity binding to Fc receptors. Using both mAbs and BiKEs, we found that both neutralization and Fc receptor engagement were necessary for effective SARS-CoV-2 clearance. Thirdly, due to ACE2 being necessary for viral entry, ACE2 will maintain binding to SARS-CoV-2 despite viral evolution. Therefore, we used an ACE2 decoy Fc-fusion or BiKE, instead of an anti-SARS-CoV-2 antibody sequence, as a potential therapeutic that would withstand viral evolution. We found that the ACE2 decoy approach also required Fc receptor engagement and, unlike traditional neutralizing antibodies against specific variants, enabled the clearance of two distinct SARS-CoV-2 variants. These data show the importance of Fc engagement for mAbs, the utility of BiKEs as therapies for infectious disease, and the in vivo effectiveness of the ACE2 decoy approach. With further studies, we predict combining neutralization, the cellular response, and this ACE2 decoy approach will benefit individuals with ineffective antibody levels.

Abbreviations

ACE2, scFv, mAb, BiKE, COVID-19, Fc, CD16, CD32b, CD64, d.p.i.

Key points

With equal dosing, both neutralization and Fc engagement are necessary for the optimal efficacy of in vivo antibodies and bi-specific killer engagers (BiKEs) against SARS-CoV-2. BiKEs can clear SARS-CoV-2 virus and protect against severe infection in the hACE2-K18 mouse model. ACE2 decoys as part of Fc-fusions or BiKEs provide in vivo clearance of two disparate SARS-CoV-2 variants.

Pathogen-binding nanoparticles to inhibit host cell infection by heparan sulfate and sialic acid dependent viruses and protozoan parasites

Global health faces an immense burden from infectious diseases caused by viruses and intracellular protozoan parasites such as the coronavirus disease (COVID-19) and malaria, respectively. These pathogens propagate through the infection of human host cells. The first stage of this host cell infection mechanism is cell attachment, which typically involves interactions between the infectious agent and surface components on the host cell membranes, specifically heparan sulfate (HS) and/or sialic acid (SA). Hence, nanoparticles (NPs) which contain or mimic HS/SA that can directly bind to the pathogen surface and inhibit cell infection are emerging as potential candidates for an alternative anti-infection therapeutic strategy. These NPs can be prepared from metals, soft matter (lipid, polymer, and dendrimer), DNA, and carbon-based materials among others and can be designed to include aspects of multivalency, broad-spectrum activity, biocidal mechanisms, and multifunctionality. This review provides an overview of such anti-pathogen nanomedicines beyond drug delivery. Nanoscale inhibitors acting against viruses and obligate intracellular protozoan parasites are discussed. In the future, the availability of broadly applicable nanotherapeutics would allow early tackling of existing and upcoming viral diseases. Invasion inhibitory NPs could also provide urgently needed effective treatments for protozoan parasitic infections.

Conversion of Host Cell Receptor into Virus Destructor by Immunodisc to Neutralize Diverse SARS-CoV-2 Variants

The decreasing efficacy of antiviral drugs due to viral mutations highlights the challenge of developing a single agent targeting multiple strains. Using host cell viral receptors as competitive inhibitors is promising, but their low potency and membrane-bound nature have limited this strategy. In this study, the authors show that angiotensin-converting enzyme 2 (ACE2) in a planar membrane patch can effectively neutralize all tested severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants that emerged during the COVID-19 pandemic. The ACE2-incorporated membrane patch implemented using nanodiscs replicated the spike-mediated membrane fusion process outside the host cell, resulting in virus lysis, extracellular RNA release, and potent antiviral activity. While neutralizing antibodies became ineffective as the SARS-CoV-2 evolved to better penetrate host cells the ACE2-incorporated nanodiscs became more potent, highlighting the advantages of using receptor-incorporated nanodiscs for antiviral purposes. ACE2-incorporated immunodisc, an Fc fusion nanodisc developed in this study, completely protected humanized mice infected with SARS-CoV-2 after prolonged retention in the airways. This study demonstrates that the incorporation of viral receptors into immunodisc transforms the entry gate into a potent virucide for all current and future variants, a concept that can be extended to different viruses.

SARS-CoV-2 Omicron: Viral Evolution, Immune Evasion, and Alternative Durable Therapeutic Strategies

Since the SARS-CoV-2 Omicron virus has gained dominance worldwide, its continual evolution with unpredictable mutations and patterns has revoked all authorized immunotherapeutics. Rapid viral evolution has also necessitated several rounds of vaccine updates in order to provide adequate immune protection. It remains imperative to understand how Omicron evolves into different subvariants and causes immune escape as this could help reevaluate the current intervention strategies mostly implemented in the clinics as emergency measures to counter the pandemic and, importantly, develop new solutions. Here, we provide a review focusing on the major events of Omicron viral evolution, including the features of spike mutation that lead to immune evasion against monoclonal antibody (mAb) therapy and vaccination, and suggest alternative durable options such as the ACE2-based experimental therapies superior to mAbs to address this unprecedented evolution of Omicron virus. In addition, this type of unique ACE2-based virus-trapping molecules can counter all zoonotic SARS coronaviruses, either from unknown animal hosts or from established wild-life reservoirs of SARS-CoV-2, and even seasonal alpha coronavirus NL63 that depends on human ACE2 for infection.

COVID-19 Pandemic: Therapeutic Strategies and Vaccines

Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), a highly pathogenic and transmissible virus, has spurred an impressive accumulation of knowledge [...].

A pan-SARS-CoV-2-specific soluble angiotensin-converting enzyme 2-albumin fusion engineered for enhanced plasma half-life and needle-free mucosal delivery

Immunocompromised patients often fail to raise protective vaccine-induced immunity against the global emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. Although monoclonal antibodies have been authorized for clinical use, most have lost their ability to potently neutralize the evolving Omicron subvariants. Thus, there is an urgent need for treatment strategies that can provide protection against these and emerging SARS-CoV-2 variants to prevent the development of severe coronavirus disease 2019. Here, we report on the design and characterization of a long-acting viral entry-blocking angiotensin-converting enzyme 2 (ACE2) dimeric fusion molecule. Specifically, a soluble truncated human dimeric ACE2 variant, engineered for improved binding to the receptor-binding domain of SARS-CoV-2, was fused with human albumin tailored for favorable engagement of the neonatal fragment crystallizable receptor (FcRn), which resulted in enhanced plasma half-life and allowed for needle-free transmucosal delivery upon nasal administration in human FcRn-expressing transgenic mice. Importantly, the dimeric ACE2-fused albumin demonstrated potent neutralization of SARS-CoV-2 immune escape variants.

[Development of an engineered ACE2 decoy for COVID-19 therapy.]

It has been passed four years since the pandemic caused by the severe acute respiratory syndrome-2 (SARS-CoV-2) that began in 2019. Since June 2020, we have been working on a project to develop a therapeutic drug using receptor decoys, even though we cannot predict how long the pandemic will last or how long our daily lives will be restricted. This receptor decoy utilizes Angiotensin-converting enzyme 2 (ACE2), which is the receptor for SARS-CoV-2, and involves introducing mutations that enhance its binding ability with the spike protein of SARS-CoV-2. This high-affinity ACE2, acting as a decoy protein, is a strategy to inhibit viral infection and to expect therapeutic effects by replacing the endogeneous ACE2 that SARS-CoV-2 binds to with ACE2 decoy. This paper introduces the development of ACE2 decoys that have progressed through collaborative research with many researchers outside the field of virology.