Evaluation of Antiviral Activity of Gemcitabine Derivatives against Influenza Virus and Severe Acute Respiratory Syndrome Coronavirus 2.

Gemcitabine is a nucleoside analogue of deoxycytidine and has been reported to be a broad-spectrum antiviral agent against both DNA and RNA viruses. Screening of a nucleos(t)ide analogue-focused library identified gemcitabine and its derivatives (compounds 1, 2a, and 3a) blocking influenza virus infection. To improve their antiviral selectivity by reducing cytotoxicity, 14 additional derivatives were synthesized in which the pyridine rings of 2a and 3a were chemically modified. Structure-and-activity and structure-and-toxicity relationship studies demonstrated that compounds 2e and 2h were most potent against influenza A and B viruses but minimally cytotoxic. It is noteworthy that in contrast to cytotoxic gemcitabine, they inhibited viral infection with 90% effective concentrations of 14.5-34.3 and 11.4-15.9 µM, respectively, maintaining viability of mock-infected cells over 90% at 300 µM. Resulting antiviral selectivity was comparable to that of a clinically approved nucleoside analogue, favipiravir. The cell-based viral polymerase assay proved the mode-of-action of 2e and 2h targeting viral RNA replication and/or transcription. In a murine influenza A virus-infection model, intraperitoneal administration of 2h not only reduced viral RNA level in the lungs but also alleviated infection-mediated pulmonary infiltrates. In addition, it inhibited replication of severe acute respiratory syndrome virus 2 infection in human lung cells at subtoxic concentrations. The present study could provide a medicinal chemistry framework for the synthesis of a new class of viral polymerase inhibitors.

Tankyrase-selective inhibitor STP1002 shows preclinical antitumour efficacy without on-target toxicity in the gastrointestinal tract.

BACKGROUND: Tankyrase inhibition stabilises AXINs and antagonises the Wnt/ß-catenin pathway in adenomatous polyposis coli (APC)-mutated colorectal cancer (CRC), suggesting that tankyrase is a potential therapeutic target for APC-mutated CRC. However, clinical trials on reported tankyrase inhibitors have been severely limited by on-target toxicity in the gastrointestinal (GI) tract. Herein, we report a new tankyrase-selective inhibitor, STP1002, having preclinical antitumour efficacy without on-target toxicity in APC-mutated CRC models. METHODS: STP1002 was developed and characterised using in vitro and in vivo functional studies; its pharmacokinetics, antitumour efficacy and toxicity were evaluated in vivo. RESULTS: STP1002 showed potent, selective inhibition of tankyrase 1/2 but not of members of the poly (ADP-ribose) polymerase 1/2 (PARP1/2). STP1002 exerted antitumour activity by stabilising AXINs and antagonising the Wnt/ß-catenin pathway in a subset of APC-mutated CRC cell lines but not in inhibitor-resistant cells and APC-wild-type CRC cell lines. STP1002 showed favourable pharmacokinetic profiles for oral administration once daily. STP1002 inhibited tumour growth of APC-mutated CRC xenograft animal models but not of APC-wild type models in a dose-dependent manner. The antitumour efficacy of STP1002 was confirmed using APC-mutated CRC patient-derived tumour xenograft models. STP1002 showed no significant on-target toxicity in the GI tract compared to G007-LK, which shows severe ileum toxicity in preclinical animal models. CONCLUSIONS: These results demonstrate that STP1002, a novel, orally active tankyrase inhibitor, shows preclinical antitumour efficacy without on-target toxicity in the GI tract. Our data provide a rationale for a clinical trial on STP1002 as a potential tankyrase-targeted drug in patients with APC-mutated CRC.

Anticoagulation therapy promotes the tumor immune-microenvironment and potentiates the efficacy of immunotherapy by alleviating hypoxia.

PURPOSE: Here, this study verifies that cancer-associated thrombosis (CAT) accelerates hypoxia, which is detrimental to the tumor immune microenvironment by limiting tumor perfusion. Therefore, we designed an oral anticoagulant therapy to improve the immunosuppressive tumor microenvironment and potentiate the efficacy of immunotherapy by alleviating tumor hypoxia. EXPERIMENTAL DESIGN: A novel oral anticoagulant (STP3725) was developed to consistently prevent CAT formation. Tumor perfusion and hypoxia were analyzed with or without treating STP3725 in wild-type and P selectin knockout mice. Immunosuppressive cytokines and cells were analyzed to evaluate the alteration of the tumor microenvironment. Effector lymphocyte infiltration in tumor tissue was assessed by congenic CD45.1 mouse lymphocyte transfer model with or without anticoagulant therapy. Finally, various tumor models including K-Ras mutant spontaneous cancer model were employed to validate the role of the anticoagulation therapy in enhancing the efficacy of immunotherapy. RESULTS: CAT was demonstrated to be one of the perfusion barriers, which fosters immunosuppressive microenvironment by accelerating tumor hypoxia. Consistent treatment of oral anticoagulation therapy was proved to promote tumor immunity by alleviating hypoxia. Furthermore, this resulted in decrease of both hypoxia-related immunosuppressive cytokines and myeloid-derived suppressor cells while improving the spatial distribution of effector lymphocytes and their activity. The anticancer efficacy of αPD-1 antibody was potentiated by co-treatment with STP3725, also confirmed in various tumor models including the K-Ras mutant mouse model, which is highly thrombotic. CONCLUSIONS: Collectively, these findings establish a rationale for a new and translational combination strategy of oral anticoagulation therapy with immunotherapy, especially for treating highly thrombotic cancers. The combination therapy of anticoagulants with immunotherapies can lead to substantial improvements of current approaches in the clinic.

A highly potent and safe pyrrolopyridine-based allosteric HIV-1 integrase inhibitor targeting host LEDGF/p75-integrase interaction site.

Allosteric integrase inhibitors (ALLINIs) are a class of experimental anti-HIV agents that target the noncatalytic sites of the viral integrase (IN) and interfere with the IN-viral RNA interaction during viral maturation. Here, we report a highly potent and safe pyrrolopyridine-based ALLINI, STP0404, displaying picomolar IC50 in human PBMCs with a >24,000 therapeutic index against HIV-1. X-ray structural and biochemical analyses revealed that STP0404 binds to the host LEDGF/p75 protein binding pocket of the IN dimer, which induces aberrant IN oligomerization and blocks the IN-RNA interaction. Consequently, STP0404 inhibits proper localization of HIV-1 RNA genomes in viral particles during viral maturation. Y99H and A128T mutations at the LEDGF/p75 binding pocket render resistance to STP0404. Extensive in vivo pharmacological and toxicity investigations demonstrate that STP0404 harbors outstanding therapeutic and safety properties. Overall, STP0404 is a potent and first-in-class ALLINI that targets LEDGF/p75 binding site and has advanced to a human trial.

Comparison of Antiviral Activity of Gemcitabine with 2'-Fluoro-2'-Deoxycytidine and Combination Therapy with Remdesivir against SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID-19) pandemic. The virus still spreads globally through human-to-human transmission. Nevertheless, there are no specific treatments clinically approved. This study aimed to compare antiviral activity of gemcitabine and its analogue 2'-fluoro-2'-deoxycytidine (2FdC) against SARS-CoV-2 as well as cytotoxicity in vitro. Fluorescent image-based antiviral assays revealed that gemcitabine was highly potent, with a 50% effective concentration (EC50) of 1.2 µM, more active than the well-known nucleoside monophosphate remdesivir (EC50 = 35.4 µM). In contrast, 2FdC was marginally active (EC50 = 175.2 µM). For all three compounds, the 50% cytotoxic concentration (CC50) values were over 300 µM toward Vero CCL-81 cells. Western blot and quantitative reverse-transcription polymerase chain reaction analyses verified that gemcitabine blocked viral protein expression in virus-infected cells, not only Vero CCL-81 cells but also Calu-3 human lung epithelial cells in a dose-dependent manner. It was found that gemcitabine has a synergistic effect when combined with remdesivir. This report suggests that the difluoro group of gemcitabine is critical for the antiviral activity and that its combination with other evaluated antiviral drugs, such as remdesivir, could be a desirable option to treat SARS-CoV-2 infection.

Folding and anion-binding properties of fluorescent oligoindole foldamers.

A series of oligoindole foldamers 1 a-d that are highly fluorescent were prepared by using a biindole derivative as the repeating unit, and their folding and anion-binding properties were revealed by (1)H NMR and fluorescence spectroscopy. The oligoindoles exist in an extended conformation, but adopt a compact helical structure in the presence of an anion. The anion is entrapped inside the tubular cavity of the helical strand, comprising four aryl units per turn, by multiple hydrogen bonds with the indole NHs. These structural features were confirmed by (1)H NMR and fluorescence spectroscopy. When folded by anion binding, 1 b-d show characteristic downfield shifts of the NH signals and upfield shifts of the aromatic CH signals by Deltadelta=0.1-1.0 ppm. The average chemical shift for all the aromatic signals of 1 a-d is more upfield shifted as the chain lengthens, as anticipated from the degree of overlapped aromatic surfaces in the helical strand. Moreover, 1 a-d are strongly fluorescent in the absence of an anion. Upon binding an anion such as a chloride, the shorter oligoindoles 1 a and b lead to negligible change in the emission spectra, whereas the longer ones 1 c and d result in dramatic changes, that is, large hypochromic and bathochromic shifts (Deltalambda=65 and 70 nm) of the emission band, confirming the helical folding. The association constants (K(a)) between oligoindoles and tetrabutylammonium chloride strongly depend on the chain length; <1 M(-1) for 1 a, 630 M(-1) for 1 b, 1.1x10(5) M(-1) for 1 c, and 2.9x10(5) M(-1) for 1 d in 20 % (v/v) MeOH/CH(2)Cl(2) at 24+/-1 degrees C. In addition, the association constants of 1 c and 1 d with other anions such as fluoride, bromide, iodide, azide, cyanide, acetate, and nitrate are determined to be in the order of 10(3)-10(6) M(-1) under the same conditions.