2017 marked the 30th anniversary of the approval of zidovudine (AZT) as the first HIV/AIDS therapy. Since then, more than eighty antiviral drugs have received FDA approval, half of which treat HIV infection. Here, we provide a retrospective analysis of approved antiviral drugs, including therapeutics against other major chronic infections such as hepatitis B and C, and herpes viruses, over the last thirty years. During this time, only a few drugs were approved to treat acute viral infections, mainly influenza. Analysis of these approved antiviral drugs based on molecular class and mode of action shows that a large majority are small molecules and direct-acting agents as opposed to proteins, peptides, or oligonucleotides and host-targeting therapies. In addition, approvals of combination therapies accelerated over the last five years. We also provide a prospective study of future potential antiviral therapies, based on current clinical research pipelines across the pharmaceutical industry. Comparing past drug approvals with current clinical candidates hints at the future evolution in antiviral therapies and reveals how antiviral medicines are often discovered. Overall, this work helps forecast future trends and innovation in the field of antiviral research and development.

Recent cases of severe toxicity during clinical trials have been associated with antiviral ribonucleoside analogs (e.g. INX-08189 and balapiravir). Some have hypothesized that the active metabolites of toxic ribonucleoside analogs, the triphosphate forms, inadvertently target human mitochondrial RNA polymerase (POLRMT), thus inhibiting mitochondrial RNA transcription and protein synthesis. Others have proposed that the prodrug moiety released from the ribonucleoside analogs might instead cause toxicity. Here, we report the mitochondrial effects of several clinically relevant and structurally diverse ribonucleoside analogs including NITD-008, T-705 (favipiravir), R1479 (parent nucleoside of balapiravir), PSI-7851 (sofosbuvir), and INX-08189 (BMS-986094). We found that efficient substrates and chain terminators of POLRMT, such as the nucleoside triphosphate forms of R1479, NITD-008, and INX-08189, are likely to cause mitochondrial toxicity in cells, while weaker chain terminators and inhibitors of POLRMT such as T-705 ribonucleoside triphosphate do not elicit strong in vitro mitochondrial effects. Within a fixed 3'-deoxy or 2'-C-methyl ribose scaffold, changing the base moiety of nucleotides did not strongly affect their inhibition constant (K) against POLRMT. By swapping the nucleoside and prodrug moieties of PSI-7851 and INX-08189, we demonstrated that the cell-based toxicity of INX-08189 is mainly caused by the nucleoside component of the molecule. Taken together, these results show that diverse 2' or 4' mono-substituted ribonucleoside scaffolds cause mitochondrial toxicity. Given the unpredictable structure-activity relationship of this ribonucleoside liability, we propose a rapid and systematic in vitro screen combining cell-based and biochemical assays to identify the early potential for mitochondrial toxicity.

No abstract

Human respiratory syncytial virus (RSV) is a negative-sense RNA virus and a significant cause of respiratory infection in infants and the elderly. No effective vaccines or antiviral therapies are available for the treatment of RSV. ALS-8176 is a first-in-class nucleoside prodrug inhibitor of RSV replication currently under clinical evaluation. ALS-8112, the parent molecule of ALS-8176, undergoes intracellular phosphorylation, yielding the active 5'-triphosphate metabolite. The host kinases responsible for this conversion are not known. Therefore, elucidation of the ALS-8112 activation pathway is key to further understanding its conversion mechanism, particularly given its potent antiviral effects. Here, we have identified the activation pathway of ALS-8112 and show it is unlike other antiviral cytidine analogs. The first step, driven by deoxycytidine kinase (dCK), is highly efficient, while the second step limits the formation of the active 5'-triphosphate species. ALS-8112 is a 2'- and 4'-modified nucleoside analog, prompting us to investigate dCK recognition of other 2'- and 4'-modified nucleosides. Our biochemical approach along with computational modeling contributes to an enhanced structure-activity profile for dCK. These results highlight an exciting potential to optimize nucleoside analogs based on the second activation step and increased attention toward nucleoside diphosphate and triphosphate prodrugs in drug discovery.

Objective. To explore the molecular mechanisms underlying dysregulation of lipid metabolism in the pathogenesis of systemic lupus erythematosus (SLE).Methods. B cells in peripheral blood from patients with SLE and healthy controls were stained with BODIPY dye for detection of lipids. Mice with targeted knockout of genes for B cell-specific inositol-requiring enzyme 1α (IRE-1α) and stearoyl-coenzyme A desaturase 1 (SCD-1) were used for studying the influence of the IRE-1α/SCD-1/SCD-2 pathway on B cell differentiation and autoantibody production. The preclinical efficacy of IRE-1α suppression as a treatment for lupus was tested in MRL.Fas lpr mice.Results. In cultures with mouse IRE-1α-null B cells, supplementation with monounsaturated fatty acids largely rescued differentiation of plasma cells from B cells, indicating that the compromised capacity of B cell differentiation in the absence of IRE-1α may be attributable to a defect in monounsaturated fatty acid synthesis. Moreover, activation with IRE-1α/X-box binding protein 1 (XBP-1) was required to facilitate B cell expression of SCD-1 and SCD-2, which are 2 critical enzymes that catalyze monounsaturated fatty acid synthesis. Mice with targeted Scd1 gene deletion displayed a phenotype that was similar to that of IRE-1α-deficient mice, with diminished B cell differentiation into plasma cells. Importantly, in B cells from patients with lupus, both IRE-1α expression and Xbp1 messenger RNA splicing were significantly increased, and this was positively correlated with the expression of both Scd1 and Scd2 as well as with the amount of B cell lipid deposition. In MRL.Fas lpr mice, both genetic and pharmacologic suppression of IRE-1α protected against the pathologic development and progression of lupus-like autoimmune disease.Conclusion. The results of this study reveal a molecular link in the dysregulation of lipid metabolism in the pathogenesis of lupus, demonstrating that the IRE-1α/XBP-1 pathway controls plasma cell differentiation through SCD-1/SCD-2-mediated monounsaturated fatty acid synthesis. These findings provide a rationale for targeting IRE-1α and monounsaturated fatty acid synthesis in the treatment of patients with SLE.

Background: Charcot-Leyden crystals (CLCs) are recognized to be classic hallmarks of eosinophilic inflammation.Both protein and mRNA levels of CLC in nasal secretions and nasal brushing samples have been associated with nasal polyp recurrence. However, whether the crystalline CLC structures in nasal tissue could serve as an effective biomarker to predict polyp recurrence remains unclear.Methods: A total of 110 patients with chronic rhinosinusitis with nasal polyps (CRSwNP) completing the postoperative follow-up over a period of 24 months were recruited. Hematoxylin and eosin staining was employed for CLCs identification. The predictive factors for polyp recurrence were determined by binary logistic regression analysis.Results: Thirty three (30.00%) patients developed recurrence during a 24-month postoperative follow-up, in which 84.85% (28/33) patients had crystalline CLC structures. Logistic regression analysis showed that crystalline CLC structure in nasal tissues is predictive of polyp recurrence. Youden index demonstrated crystalline CLC structure higher than 1 per high power field can predict postoperative polyp recurrence with 84.80% sensitivity and 98.70% specificity. Conclusions:The crystalline CLC structures in nasal tissues may serve as an easy-counting and promising biomarker to predict CRSwNP recurrence.To the editor, Chronic rhinosinusitis with nasal polyps (CRSwNP) is a heterogeneous and challenging inflammatory airway disease involving noneosinophilic and eosinophilic endotypes. In fact, 98.5% eosinophilic CRSwNP (Eos CRSwNP) patients were recurrent after undergone endoscopic sinus surgery (ESS). 1 Therefore, the identification of predictors of recurrence for Eos CRSwNP is crucial for better disease control. The local tissue eosinophilia has been proven to be the most important predictor. 2 However, there are no standard methods for evaluating tissue eosinophilia due to uneven distribution and diversity in geographic conditions. 2,3 Thus, there are limitations to the predict recurrence of CRSwNP based only on tissue eosinophilia.Charcot-Leyden crystals (CLCs), composed by Galectin-10 (Gal-10), were first proposed in the late 1800s by Charcot and Leyden.The typical CLCs are structures identified as needle-shaped bipyramidal Gal-10 crystals detected by morphological methods. Gal-10 protein have three distinct forms including crystalline CLC/Gal-10 crystal structures (CLCs), extracellular vesicles, and extracellular soluble Gal-10. 4 Recent studies have indicated that CLC mRNA and protein levels in nasal brushing/secretions/tissues detected by ELISA and PCR were used as predictive indicators for recurrent CRSwNP and glucocorticoid sensitivity. [5][6][7] Since only crystalline CLCs, but not soluble CLC/Gal-10 protein, drive type 2 immunity, allergy and neutrophilic inflammation, 8,9 the predictive value of functional CLCs for nasal polyp (NP) relapse should be evaluated. However, little is known regarding whether crystalline CLC structures can be utilized to predict NP recurrence.This was a retrospecti...

The tumor microenvironment (TME) enhances regulatory T (T reg ) cell stability and immunosuppressive functions through up-regulation of lineage transcription factor Foxp3, a phenomenon known as T reg fitness or adaptation. Here, we characterize previously unknown TME-specific cellular and molecular mechanisms underlying T reg fitness. We demonstrate that TME-specific stressors including transforming growth factor–β (TGF-β), hypoxia, and nutrient deprivation selectively induce two Foxp3-specific deubiquitinases, ubiquitin-specific peptidase 22 ( Usp22 ) and Usp21 , by regulating TGF-β, HIF, and mTOR signaling, respectively, to maintain T reg fitness. Simultaneous deletion of both USPs in T reg cells largely diminishes TME-induced Foxp3 up-regulation, alters T reg metabolic signatures, impairs T reg -suppressive function, and alleviates T reg suppression on cytotoxic CD8 + T cells. Furthermore, we developed the first Usp22 -specific small-molecule inhibitor, which dramatically reduced intratumoral T reg Foxp3 expression and consequently enhanced antitumor immunity. Our findings unveil previously unappreciated mechanisms underlying T reg fitness and identify Usp22 as an antitumor therapeutic target that inhibits T reg adaptability in the TME.

Through abnormal vascularization, cytokine production, and nutrient depletion, tumors can create a highly immunosuppressive microenvironment that favors the functionality of immune regulatory programs over anti-tumor effector responses. Particularly, the highly immunosuppressive tumor microenvironment (TME) favors T regulatory (Treg) cell stability and function, while diminishing the anti-tumor activity of effector T cells. Here, we characterized previously unknown TME-specific cellular and molecular mechanisms that promote intratumoral Treg adaptation through Foxp3. We uncovered the critical role of FOXP3-targeting deubiquitinases, ubiquitin specific peptidase 22 (Usp22) and 21 (Usp21) as environmentally sensitive factors of multiple TME-specific environmental stressors including TGF-β, hypoxia, and nutrient deprivation. Specifically, Usp22 and Usp21 maintain optimal Foxp3 expression through HIF, AMPK, and mTOR activity. The simultaneous loss of both USPs synergizes to alter Treg metabolic signatures and impair suppressive mechanisms, resulting in enhanced anti-tumor activity. Our findings unveil new mechanisms underlying the functional uniqueness of intratumoral Treg cells, and identify Usp22 and Usp21 as a antitumor therapeutic targets that inhibit Treg adaptability in the TME.