Interferon-Inducible Guanylate-Binding Protein 5 Inhibits Replication of Multiple Viruses by Binding to the Oligosaccharyltransferase Complex and Inhibiting Glycoprotein Maturation.

Viral infection induces production of type I interferons and expression of interferon-stimulated genes (ISGs) that play key roles in inhibiting viral infection. Here, we show that the ISG guanylate-binding protein 5 (GBP5) inhibits N-linked glycosylation of key proteins in multiple viruses, including SARS-CoV-2 spike protein. GBP5 binds to accessory subunits of the host oligosaccharyltransferase (OST) complex and blocks its interaction with the spike protein, which results in misfolding and retention of spike protein in the endoplasmic reticulum likely due to decreased N-glycan transfer, and reduces the assembly and release of infectious virions. Consistent with these observations, pharmacological inhibition of the OST complex with NGI-1 potently inhibits glycosylation of other viral proteins, including MERS-CoV spike protein, HIV-1 gp160, and IAV hemagglutinin, and prevents the production of infectious virions. Our results identify a novel strategy by which ISGs restrict virus infection and provide a rationale for targeting glycosylation as a broad antiviral therapeutic strategy.

Induction of neutralizing antibodies against SARS-CoV-2 variants by a multivalent mRNA-lipid nanoparticle vaccine encoding SARS-CoV-2/SARS-CoV Spike protein receptor-binding domains in mice.

To address the need for multivalent vaccines against Coronaviridae that can be rapidly developed and manufactured, we compared antibody responses against SARS-CoV, SARS-CoV-2, and several variants of concern in mice immunized with mRNA-lipid nanoparticle vaccines encoding homodimers or heterodimers of SARS-CoV/SARS-CoV-2 receptor-binding domains. All vaccine constructs induced robust anti-RBD antibody responses, and the heterodimeric vaccine elicited an IgG response capable of cross-neutralizing SARS-CoV, SARS-CoV-2 Wuhan-Hu-1, B.1.351 (beta), and B.1.617.2 (delta) variants.

Peptide-Driven Proton Sponge Nano-Assembly for Imaging and Triggering Lysosome-Regulated Immunogenic Cancer Cell Death.

Triggering lysosome-regulated immunogenic cell death (ICD, e.g., pyroptosis and necroptosis) with nanomedicines is an emerging approach for turning an "immune-cold" tumor "hot"-a key challenge faced by cancer immunotherapies. Proton sponge such as high-molecular-weight branched polyethylenimine (PEI) is excellent at rupturing lysosomes, but its therapeutic application is hindered by uncontrollable toxicity due to fixed charge density and poor understanding of resulted cell death mechanism. Here, a series of proton sponge nano-assemblies (PSNAs) with self-assembly controllable surface charge density and cell cytotoxicity are created. Such PSNAs are constructed via low-molecular-weight branched PEI covalently bound to self-assembling peptides carrying tetraphenylethene pyridinium (PyTPE, an aggregation-induced emission-based luminogen). Assembly of PEI assisted by the self-assembling peptide-PyTPE leads to enhanced surface positive charges and cell cytotoxicity of PSNA. The self-assembly tendency of PSNAs is further optimized by tuning hydrophilic and hydrophobic components within the peptide, thus resulting in the PSNA with the highest fluorescence, positive surface charge density, cell uptake, and cancer cell cytotoxicity. Systematic cell death mechanistic studies reveal that the lysosome rupturing-regulated pyroptosis and necroptosis are at least two causes of cell death. Tumor cells undergoing PSNA-triggered ICD activate immune cells, suggesting the great potential of PSNAs to trigger anticancer immunity.

Redox regulation of m6A methyltransferase METTL3 in ß-cells controls the innate immune response in type 1 diabetes.

Type 1 diabetes (T1D) is characterized by the destruction of pancreatic ß-cells. Several observations have renewed the interest in ß-cell RNA sensors and editors. Here, we report that N6-methyladenosine (m6A) is an adaptive ß-cell safeguard mechanism that controls the amplitude and duration of the antiviral innate immune response at T1D onset. m6A writer methyltransferase 3 (METTL3) levels increase drastically in ß-cells at T1D onset but rapidly decline with disease progression. m6A sequencing revealed the m6A hypermethylation of several key innate immune mediators, including OAS1, OAS2, OAS3 and ADAR1 in human islets and EndoC-ßH1 cells at T1D onset. METTL3 silencing enhanced 2'-5'-oligoadenylate synthetase levels by increasing its mRNA stability. Consistently, in vivo gene therapy to prolong Mettl3 overexpression specifically in ß-cells delayed diabetes progression in the non-obese diabetic mouse model of T1D. Mechanistically, the accumulation of reactive oxygen species blocked upregulation of METTL3 in response to cytokines, while physiological levels of nitric oxide enhanced METTL3 levels and activity. Furthermore, we report that the cysteines in position C276 and C326 in the zinc finger domains of the METTL3 protein are sensitive to S-nitrosylation and are important to the METTL3-mediated regulation of oligoadenylate synthase mRNA stability in human ß-cells. Collectively, we report that m6A regulates the innate immune response at the ß-cell level during the onset of T1D in humans.

Generation of 3D lung organoids from human induced pluripotent stem cells for modeling of lung development and viral infection.

The lack of physiologically relevant in vitro models has hampered progress in understanding human lung development and disease. Here, we describe a protocol in which human induced pluripotent stem cells (hiPSCs) undergo stepwise differentiation into definitive endoderm (>88% population) to three-dimensional (3D) lung organoids (LORGs), which contain both epithelial and mesenchymal cellular architecture and display proximal and distal airway patterning. These LORGs can maintained for more than 90 days by re-embedding in the Matrigel. We show the utility of LORGs for disease modeling and drug screening by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and treatment with antiviral drugs.

KIAA1429/VIRMA promotes breast cancer progression by m6 A-dependent cytosolic HAS2 stabilization.

N6 -methyladenosine (m6 A), the most abundant internal modification in eukaryotic mRNA, plays important roles in many physiological and pathological processes, including the development and progression of cancer. RNA modification by m6 A is regulated by methyltransferases, demethylases, and m6 A-binding proteins that function in large part by regulating mRNA expression and function. Here, we investigate the expression of m6 A regulatory proteins in breast cancer. We find that expression of KIAA1429/VIRMA, a component of the m6 A methyltransferase complex, is upregulated in breast cancer tissue and correlates positively with poor survival. KIAA1429/VIRMA is mislocalized to the cytosol of breast cancer tissues and cell lines, and shRNA-mediated knockdown inhibits breast cancer cell proliferation, migration, and invasion. Mechanistically, KIAA1429/VIRMA is shown to bind to the m6 A-dependent RNA-binding protein insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3), leading to recruitment and stabilization of m6 A-modified hyaluronan synthase 2 (HAS2) mRNA. HAS2 mRNA and KIAA1429/VIRMA mRNA levels correlate positively in breast cancer tissues, suggesting that the KIAA1429/VIRMA-IGF2BP3-HAS2 axis promotes breast cancer growth and contributes to poor prognosis.

A La2O3/MXene composite electrode for supercapacitors with improved capacitance and cycling performance.

Developing efficient electrode materials is a key towards high power electrochemical energy storage devices. Two-dimensional (2D) MXene shows excellent conductivity and electrochemical performance among other materials. However, the restacking of MXene layers may degrade their specific capacity and cycling performance. Considering this challenge, here we have designed a composite made of 2D MXene nanosheets and lanthanum oxide (La2O3) nanoparticles to overcome the limitations. The bifunctionality of La2O3 nanoparticles prevents the restacking of MXene layers and enhances the electrochemical properties of the electrode due to its good Faradic characteristics. The specific capacitance of the La2O3/MXene composite electrode is 366 F/g at 1 A/g, which is 4.5 and 3 times higher than those of the individual La2O3 and MXene. The composite electrode displays a capacitance retention of 96% after 1,000 cycles, which is due to synergistic effects between the two components and indicates the potential of La2O3/MXene composite for supercapacitors.

1-O-Octadecyl-2-O-benzyl-sn-glyceryl-3-phospho-GS-441524 (V2043). Evaluation of Oral V2043 in a Mouse Model of SARS-CoV-2 Infection and Synthesis and Antiviral Evaluation of Additional Phospholipid Esters with Enhanced Anti-SARS-CoV-2 Activity.

Early antiviral treatments, including intravenous remdesivir (RDV), reduce hospitalization and severe disease caused by COVID-19. An orally bioavailable RDV analog may facilitate earlier treatment of non-hospitalized COVID-19 patients. Here we describe the synthesis and evaluation of alkyl glyceryl ether phosphodiesters of GS-441524 (RVn), lysophospholipid analogs which allow for oral bioavailability and stability in plasma. Oral treatment of SARS-CoV-2-infected BALB/c mice with 1-O-octadecyl-2-O-benzyl-sn-glyceryl-3-phospho-RVn (60 mg/kg orally, once daily for 5 days starting 12h after infection) reduced lung viral load by 1.5 log10 units versus vehicle at day 2 and to below the limit of detection at day 5. Structure/activity evaluation of additional analogs that have hydrophobic ethers at the sn-2 of glycerol revealed improved in vitro antiviral activity by introduction of a 3-fluoro-4-methoxy-substituted benzyl or a 3- or 4-cyano-substituted benzyl. Collectively, our data support the development of RVn phospholipid prodrugs as oral antiviral agents for prevention and treatment of SARS-CoV-2 infections.

Long noncoding RNA HIKER regulates erythropoiesis in Monge's disease via CSNK2B.

Excessive erythrocytosis (EE) is a major hallmark of patients suffering from chronic mountain sickness (CMS, also known as Monge's disease) and is responsible for major morbidity and even mortality in early adulthood. We took advantage of unique populations, one living at high altitude (Peru) showing EE, with another population, at the same altitude and region, showing no evidence of EE (non-CMS). Through RNA-Seq, we identified and validated the function of a group of long noncoding RNAs (lncRNAs) that regulate erythropoiesis in Monge's disease, but not in the non-CMS population. Among these lncRNAs is hypoxia induced kinase-mediated erythropoietic regulator (HIKER)/LINC02228, which we showed plays a critical role in erythropoiesis in CMS cells. Under hypoxia, HIKER modulated CSNK2B (the regulatory subunit of casein kinase 2). A downregulation of HIKER downregulated CSNK2B, remarkably reducing erythropoiesis; furthermore, an upregulation of CSNK2B on the background of HIKER downregulation rescued erythropoiesis defects. Pharmacologic inhibition of CSNK2B drastically reduced erythroid colonies, and knockdown of CSNK2B in zebrafish led to a defect in hemoglobinization. We conclude that HIKER regulates erythropoiesis in Monge's disease and acts through at least one specific target, CSNK2B, a casein kinase.

Neutralizing Antibody Responses After Severe Acute Respiratory Syndrome Coronavirus 2 BA.2 and BA.2.12.1 Infection Do Not Neutralize BA.4 and BA.5 and Can Be Blunted by Nirmatrelvir/Ritonavir Treatment.

The factors contributing to the rapid emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BA.4 and BA.5 subvariants in populations that experienced recent surges of BA.2 and BA.2.12.1 infections are not understood. Neutralizing antibodies (NAbs) are likely to protect against severe disease if present in sufficient quantity. We found that after BA.2 or BA.2.12.1 infection, NAb responses were largely cross-neutralizing but were much less effective against BA.5. In addition, individuals who were infected and treated early with nirmatrelvir/ritonavir (Paxlovid) had lower NAb levels than untreated individuals.

Small-molecule PTPN2 Inhibitors Sensitize Resistant Melanoma to Anti-PD-1 Immunotherapy.

Although immune checkpoint inhibitors targeting T-cell immunoregulatory proteins have revolutionized cancer treatment, they are effective only in a limited number of patients, and new strategies are needed to enhance tumor responses to immunotherapies. Deletion of protein tyrosine phosphatase non-receptor type 2 (Ptpn2), a regulator of growth factor and cytokine signaling pathways, has been shown to sensitize murine B16F10 melanoma cells to IFNγ and anti-PD-1 immunotherapy. Here, we investigated the potential therapeutic utility of small-molecule PTPN2 inhibitors. Ten inhibitors were synthesized on the basis of in silico modeling and structure-based design and functionally tested in vitro and in vivo. We show that the inhibitors had little effect on B16F10 cells alone, but effectively sensitized the tumor cells to IFNγ treatment in vitro and to anti-PD-1 therapy in vivo. Under both conditions, Ptpn2 inhibitor cotreatment suppressed B16F10 cell growth and enhanced Stat1 phosphorylation and expression of IFNγ response genes. In vivo, PTPN2 inhibitor cotreatment significantly reduced melanoma and colorectal tumor growth and enhanced mouse survival compared with anti-PD-1 treatment alone, and this was accompanied by increased tumor infiltration by granzyme B+ CD8+ T cells. Similar results were obtained with representative murine and human colon cancer and lung cancer cell lines. Collectively, these results demonstrate that small-molecule inhibitors of PTPN2 may have clinical utility as sensitizing agents for immunotherapy-resistant cancers. Significance: To enhance the effectiveness of immunotherapies in resistant or nonresponsive cancers, it is important to develop inhibitors of enzymes that negatively influence the outcome of treatments. We have designed and evaluated small-molecule inhibitors of PTPN2 demonstrating that these compounds may have clinical utility as sensitizing agents for immunotherapy-resistant cancers.

Redox Regulation of m 6 A Methyltransferase METTL3 in Human ß-cells Controls the Innate Immune Response in Type 1 Diabetes.

Type 1 Diabetes (T1D) is characterized by autoimmune-mediated destruction of insulin-producing ß-cells. Several observations have renewed interest in the innate immune system as an initiator of the disease process against ß-cells. Here, we show that N 6 -Methyladenosine (m 6 A) is an adaptive ß-cell safeguard mechanism that accelerates mRNA decay of the 2'-5'-oligoadenylate synthetase (OAS) genes to control the antiviral innate immune response at T1D onset. m 6 A writer methyltransferase 3 (METTL3) levels increase drastically in human and mouse ß-cells at T1D onset but rapidly decline with disease progression. Treatment of human islets and EndoC-ßH1 cells with pro-inflammatory cytokines interleukin-1 ß and interferon α mimicked the METTL3 upregulation seen at T1D onset. Furthermore, m 6 A-sequencing revealed the m 6 A hypermethylation of several key innate immune mediators including OAS1, OAS2, and OAS3 in human islets and EndoC-ßH1 cells challenged with cytokines. METTL3 silencing in human pseudoislets or EndoC-ßH1 cells enhanced OAS levels by increasing its mRNA stability upon cytokine challenge. Consistently, in vivo gene therapy, to prolong Mettl3 overexpression specifically in ß-cells, delayed diabetes progression in the non-obese diabetic (NOD) mouse model of T1D by limiting the upregulation of Oas pointing to potential therapeutic relevance. Mechanistically, the accumulation of reactive oxygen species blocked METTL3 upregulation in response to cytokines, while physiological levels of nitric oxide promoted its expression in human islets. Furthermore, for the first time to our knowledge, we show that the cysteines in position C276 and C326 in the zinc finger domain of the METTL3 protein are sensitive to S-nitrosylation (SNO) and are significant for the METTL3 mediated regulation of OAS mRNA stability in human ß-cells in response to cytokines. Collectively, we report that m 6 A regulates human and mouse ß-cells to control the innate immune response during the onset of T1D and propose targeting METTL3 to prevent ß-cell death in T1D.

PCIF1-mediated deposition of 5'-cap N6,2'-O-dimethyladenosine in ACE2 and TMPRSS2 mRNA regulates susceptibility to SARS-CoV-2 infection.

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to be a major health problem worldwide. Due to the fast emergence of SARS-CoV-2 variants, understanding the molecular mechanisms of viral pathogenesis and developing novel inhibitors are essential and urgent. Here, we investigated the potential roles of N6,2'-O-dimethyladenosine (m6Am), one of the most abundant modifications of eukaryotic messenger ribonucleic acid (mRNAs), in SARS-CoV-2 infection of human cells. Using genome-wide m6Am-exo-seq, RNA sequencing analysis, and Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 genome editing, we demonstrate that phosphorylated C-terminal domain (CTD)-interacting factor 1 (PCIF1), a cap-specific adenine N6-methyltransferase, plays a major role in facilitating infection of primary human lung epithelial cells and cell lines by SARS-CoV-2, variants of concern, and other coronaviruses. We show that PCIF1 promotes infection by sustaining expression of the coronavirus receptors angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) via m6Am-dependent mRNA stabilization. In PCIF1-depleted cells, both ACE2/TMPRSS2 expression and viral infection are rescued by re-expression of wild-type, but not catalytically inactive, PCIF1. These findings suggest a role for PCIF1 and cap m6Am in regulating SARS-CoV-2 susceptibility and identify a potential therapeutic target for prevention of infection.

Virologic and Immunologic Characterization of Coronavirus Disease 2019 Recrudescence After Nirmatrelvir/Ritonavir Treatment.

We isolated a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) BA.2 variant from a person with coronavirus disease 2019 recrudescence after nirmatrelvir/ritonavir treatment. Antiviral sensitivity and neutralizing antibody testing were performed with both parental SARS-CoV-2 and multiple variants of concern. We found that neither nirmatrelvir resistance nor absence of neutralizing immunity was a likely cause of the recrudescence.

Role of PCIF1-mediated 5'-cap N6-methyladeonsine mRNA methylation in colorectal cancer and anti-PD-1 immunotherapy.

Adenosine N6-methylation (m6A) and N6,2'-O-dimethylation (m6Am) are regulatory modifications of eukaryotic mRNAs. m6Am formation is catalyzed by the methyl transferase phosphorylated CTD-interacting factor 1 (PCIF1); however, the pathophysiological functions of this RNA modification and PCIF1 in cancers are unclear. Here, we show that PCIF1 expression is upregulated in colorectal cancer (CRC) and negatively correlates with patient survival. CRISPR/Cas9-mediated depletion of PCIF1 in human CRC cells leads to loss of cell migration, invasion, and colony formation in vitro and loss of tumor growth in athymic mice. Pcif1 knockout in murine CRC cells inhibits tumor growth in immunocompetent mice and enhances the effects of anti-PD-1 antibody treatment by decreasing intratumoral TGF-ß levels and increasing intratumoral IFN-γ, TNF-α levels, and tumor-infiltrating natural killer cells. We further show that PCIF1 modulates CRC growth and response to anti-PD-1 in a context-dependent mechanism with PCIF1 directly targeting FOS, IFITM3, and STAT1 via m6Am modifications. PCIF1 stabilizes FOS mRNA, which in turn leads to FOS-dependent TGF-ß regulation and tumor growth. While during immunotherapy, Pcif1-Fos-TGF-ß, as well as Pcif1-Stat1/Ifitm3-IFN-γ axes, contributes to the resistance of anti-PD-1 therapy. Collectively, our findings reveal a role of PCIF1 in promoting CRC tumorigenesis and resistance to anti-PD-1 therapy, supporting that the combination of PCIF1 inhibition with anti-PD-1 treatment is a potential therapeutic strategy to enhance CRC response to immunotherapy. Finally, we developed a lipid nanoparticles (LNPs) and chemically modified small interfering RNAs (CMsiRNAs)-based strategy to silence PCIF1 in vivo and found that this treatment significantly reduced tumor growth in mice. Our results therefore provide a proof-of-concept for tumor growth suppression using LNP-CMsiRNA to silence target genes in cancer.

Rational Design and Optimization of m6A-RNA Demethylase FTO Inhibitors as Anticancer Agents.

Aberrant regulation of N6-methyladenosine (m6A) RNA modification has been implicated in the progression of multiple diseases, including cancer. Previously, we identified a small molecule inhibitor of the m6A demethylase fat mass- and obesity-associated protein (FTO), which removes both m6A and N6,2'-O-dimethyladenosine (m6Am) RNA modifications. In this work, we describe the rational design and optimization of a new class of FTO inhibitors derived from our previous lead FTO-04 with nanomolar potency and high selectivity against the homologous m6A RNA demethylase ALKBH5. The oxetanyl class of compounds comprise competitive inhibitors of FTO with potent antiproliferative effects in glioblastoma, acute myeloid leukemia, and gastric cancer models where lead FTO-43 demonstrated potency comparable to clinical chemotherapeutic 5-fluorouracil. Furthermore, FTO-43 increased m6A and m6Am levels in a manner comparable to FTO knockdown in gastric cancer cells and regulated Wnt/PI3K-Akt signaling pathways. The oxetanyl class contains significantly improved anticancer agents with a variety of applications beyond glioblastoma.

Genome-wide CRISPR/Cas9 transcriptional activation screen identifies a histone acetyltransferase inhibitor complex as a regulator of HIV-1 integration.

The retrovirus human immunodeficiency virus-1 (HIV-1) is the causative agent of AIDS. Although treatment of HIV/AIDS with antiretroviral therapy provides suppression of viremia, latent reservoirs of integrated proviruses preclude cure by current antiviral treatments. Understanding the mechanisms of host-viral interactions may elucidate new treatment strategies. Here, we performed a CRISPR/Cas9 transcriptional activation screen using a high-complexity, genome-wide sgRNA library to identify cellular factors that inhibit HIV-1 infection of human CD4+ T cells. MT4 cells were transduced with a CRISPR/Cas9 sgRNA library and infected with nef-deficient HIV-1NL4-3 expressing ganciclovir-sensitive thymidine kinase, thus enabling selection of HIV-1-resistant cells for analysis of enriched sgRNAs. After validation of screen hits, multiple host factors essential for HIV-1 infection were identified, including SET (SET nuclear proto-oncogene) and ANP32A (acidic nuclear phosphoprotein 32A, PP32A), which together form a histone acetylase inhibitor complex. Using multiple human cell lines and peripheral blood mononuclear cells (PBMCs) from healthy donors and HIV-1-infected individuals, we demonstrate that SET depletion increased HIV-1 infectivity by augmenting DNA integration without significantly changing sites of integration. Conversely, SET overexpression decreased HIV-1 integration and infectivity. SET protein expression was significantly reduced in PBMCs from HIV-1-infected individuals and was downregulated by HIV-1 infection of healthy donor cells in vitro. Notably, HIV-1-induced downregulation of SET could be alleviated by inhibition of the protease granzyme A. Altogether, we have identified cellular inhibitors of HIV-1 infection on a genome-wide scale, which affords new insight into host-virus interactions and may provide new strategies for HIV-1 treatment.

Induction of neutralizing antibodies against SARS-CoV-2 variants by a multivalent mRNA-lipid nanoparticle vaccine encoding SARS-CoV-2/SARS-CoV Spike protein receptor-binding domains.

To address the need for multivalent vaccines against Coronaviridae that can be rapidly developed and manufactured, we compared antibody responses against SARS-CoV, SARS-CoV-2, and several variants of concern in mice immunized with mRNA-lipid nanoparticle vaccines encoding homodimers or heterodimers of SARS-CoV/SARS-CoV-2 receptor-binding domains. All vaccine constructs induced robust anti-viral antibody responses, and the heterodimeric vaccine elicited an IgG response capable of cross-neutralizing SARS-CoV, SARS-CoV-2 Wuhan-Hu-1, B.1.351 (beta), and B.1.617.2 (delta) variants.

Regulation of antiviral innate immunity by chemical modification of viral RNA.

More than 100 chemical modifications of RNA, termed the epitranscriptome, have been described, most of which occur in prokaryotic and eukaryotic ribosomal, transfer, and noncoding RNA and eukaryotic messenger RNA. DNA and RNA viruses can modify their RNA either directly via genome-encoded enzymes or by hijacking the host enzymatic machinery. Among the many RNA modifications described to date, four play particularly important roles in promoting viral infection by facilitating viral gene expression and replication and by enabling escape from the host innate immune response. Here, we discuss our current understanding of the mechanisms by which the RNA modifications such as N6 -methyladenosine (m6A), N6 ,2'-O-dimethyladenosine (m6Am), 5-methylcytidine (m5C), N4-acetylcytidine (ac4C), and 2'-O-methylation (Nm) promote viral replication and/or suppress recognition by innate sensors and downstream activation of the host antiviral response. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems RNA Evolution and Genomics > RNA and Ribonucleoprotein Evolution.

Discovery and Mechanism of SARS-CoV-2 Main Protease Inhibitors.

The emergence of a new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), presents an urgent public health crisis. Without available targeted therapies, treatment options remain limited for COVID-19 patients. Using medicinal chemistry and rational drug design strategies, we identify a 2-phenyl-1,2-benzoselenazol-3-one class of compounds targeting the SARS-CoV-2 main protease (Mpro). FRET-based screening against recombinant SARS-CoV-2 Mpro identified six compounds that inhibit proteolysis with nanomolar IC50 values. Preincubation dilution experiments and molecular docking determined that the inhibition of SARS-CoV-2 Mpro can occur by either covalent or noncovalent mechanisms, and lead E04 was determined to inhibit Mpro competitively. Lead E24 inhibited viral replication with a nanomolar EC50 value (844 nM) in SARS-CoV-2-infected Vero E6 cells and was further confirmed to impair SARS-CoV-2 replication in human lung epithelial cells and human-induced pluripotent stem cell-derived 3D lung organoids. Altogether, these studies provide a structural framework and mechanism of Mpro inhibition that should facilitate the design of future COVID-19 treatments.