Oral administration of obeldesivir protects nonhuman primates against Sudan ebolavirus.

Obeldesivir (ODV, GS-5245) is an orally administered prodrug of the parent nucleoside of remdesivir (RDV) and is presently in phase 3 trials for COVID-19 treatment. In this work, we show that ODV and its circulating parent nucleoside metabolite, GS-441524, have similar in vitro antiviral activity against filoviruses, including Marburg virus, Ebola virus, and Sudan virus (SUDV). We also report that once-daily oral ODV treatment of cynomolgus monkeys for 10 days beginning 24 hours after SUDV exposure confers 100% protection against lethal infection. Transcriptomics data show that ODV treatment delayed the onset of inflammation and correlated with antigen presentation and lymphocyte activation. Our results offer promise for the further development of ODV to control outbreaks of filovirus disease more rapidly.

Current Trend in Antiviral Therapy for Chronic Hepatitis B.

Since active hepatitis B virus (HBV) replication is the key driver of hepatic necroinflammation and disease progression, the treatment aim of chronic hepatitis B (CHB) is to suppress HBV replication permanently to prevent hepatic decompensation, liver cirrhosis and/or hepatocellular carcinoma and prolong survival. Currently, pegylated interferon (Peg-IFN), entecavir (ETV), tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) are the first-line drugs of choice. Peg-IFN therapy has been used rarely due to its subcutaneous injection and significant side effect profile. Once daily oral ETV, TDF and TAF can suppress HBV DNA profoundly but have no direct action on cccDNA of the HBV-infected hepatocytes, hence continuing long-term therapy is usually needed to maintain HBV suppression, but the ultimate goal of HBsAg loss was rarely achieved (10 year 2%). In addition, long-term NUC therapy comes with several concerns such as increasing cost, medication adherence and loss-to-follow-up. Studies, mainly from Taiwan, have shown that finite NUCs therapy of two to three years in HBeAg-negative patients is feasible, safe and has a great benefit of much increasing HBsAg loss rate up to 30%/5 year. These have led an emerging paradigm shift to finite NUC therapy in HBeAg-negative patients globally. However, off-NUC relapse with hepatitis B flares may occur and have a risk of decompensation or even life-threatening outcomes. Therefore, proper monitoring, assessment, and retreatment decisions are crucial to ensure safety. Ideally, retreatment should be not too late to ensure safety and also not too early to allow further immune response for further HBsAg decline toward HBsAg loss. Assessment using combined HBsAg/ALT kinetics during hepatitis flare is better than biochemical markers alone to make a right retreatment decision. The strategy of finite NUC therapy has set a benchmark of high HBsAg loss rate to be achieved by the new anti-HBV drugs which are under preclinical or early phase study.

Long-term clinical benefit of Peg-IFNα and NAs sequential anti-viral therapy on HBV related HCC.

Analysis of the value of long-term antiviral therapy using sequential Peg-IFN therapy and nucleos(t)ide analogues (NAs) improves the prognosis of HBV-related HCC. HBV-related HCC patients were classified into sequential therapy with Peg-IFNα-2a and NAs, and NAs therapy alone. All patients were followed up for 5 years. The survival rate, HCC recurrence rate, Child-Pugh score, and side effects of drugs were evaluated. Firstly, the early and late cumulative survival rate was higher in patients receiving antiviral therapy compared with the control patients (p<0.05). Patients receiving sequential therapy with Peg-IFNα-2a and NAs showed a higher late cumulative survival rate and significantly reduced early and late recurrence rate, compared to those in the NA-alone group (p<0.05). Single NAs therapy only reduced the late recurrence rate in HCC-patients. Secondly, NAs therapy significantly increased the Child-Pugh score after five years of therapy (five-year therapy 7.03±1.50 vs. initial score 6.63±0.85; p<0.05), whereas the sequential therapy with Peg-IFNα-2a and NAs did not greatly alter the Child-Pugh score (6.88±1.26; p>0.05). Compared to the control patients, patients receiving antiviral therapy (NAs alone or sequential therapy with Peg-IFNα-2a and NAs) exhibited a significantly decreased Child-Pugh score (p<0.05). Compared to NAs alone, sequential therapy with Peg-IFNα-2a and NAs provided a more efficient strategy for improving both the five-year survival rate and the two-year or five-year recurrence rate in patients.

Orally Bioavailable Small-Molecule CD73 Inhibitor (OP-5244) Reverses Immunosuppression through Blockade of Adenosine Production.

The adenosinergic pathway represents an attractive new therapeutic approach in cancer immunotherapy. In this pathway, ecto-5-nucleotidase CD73 has the unique function of regulating production of immunosuppressive adenosine (ADO) through the hydrolysis of AMP. CD73 is overexpressed in many cancers, resulting in elevated levels of ADO that correspond to poor patient prognosis. Therefore, reducing the level of ADO via inhibition of CD73 is a potential strategy for treating cancers. Based on the binding mode of adenosine 5'-(α,ß-methylene)diphosphate (AOPCP) with human CD73, we designed a series of novel monophosphonate small-molecule CD73 inhibitors. Among them, OP-5244 (35) proved to be a highly potent and orally bioavailable CD73 inhibitor. In preclinical studies, 35 completely inhibited ADO production in both human cancer cells and CD8+ T cells. Furthermore, 35 lowered the ratio of ADO/AMP significantly and reversed immunosuppression in mouse models, indicating its potential as an in vivo tool compound for further development.

Overcoming the delivery barrier of oligonucleotide drugs and enhancing nucleoside drug efficiency: The use of nucleolipids.

With the rapid development of synthetic technology and biological technology, many nucleic acid-based drugs have entered the clinical trials. However, their inherent disabilities in actively and efficiently penetrating cell membranes still severely restrict their further application. The main drawback of cationic lipids, which have been widely used as nonviral vectors of nucleic acids, is their high cytotoxicity. A series of nucleoside-based or nucleotide-based nucleolipids have been reported in recent years, due to their oligonucleotide delivery capacity and low toxicity in comparison with cationic lipids. Lipophilic prodrugs of nucleoside analogs have extremely similar structures with nucleolipid vectors and are thus helpful for improving the transmembrane ability. This review introduces the progress of nucleolipids and provides new strategies for improving the delivery efficiency of nucleic acid-based drugs, as well as lipophilic prodrugs of nucleosides or nucleotides for antiviral or anticancer therapies.

Real-world study on clinical outcomes of nucleos(t)ide analogues antiviral therapy in patients with chronic hepatitis B.

Nucleos(t)ide analogues (NAs) are widely used for antiviral therapy in patients with chronic hepatitis B (CHB), but real-world data on treatment patterns and long-term clinical outcomes are not always available. Using data from electronic medical records between January 2011 and December 2016 in Shanghai, China, we evaluated patient characteristics, treatment patterns and clinical outcomes in patients with CHB. There were 6688 patients in the study cohort. The incidences of cirrhosis and hepatocellular carcinoma (HCC) were 41.0‰ and 6.8‰ person-years, respectively. There were more cirrhosis and HCC cases among patients who had shorter NA treatment duration (<365 days), or who were less compliant (<80%). In addition, increased risk of cirrhosis and HCC was observed in patients who did not achieve hepatitis B surface antigen (HBsAg) loss/seroconversion. Moreover, patients with cirrhosis developed after antiviral treatments had a higher incidence of HCC (adjusted hazard ratio 15.86, 95% confidence interval 7.35-34.24). Good compliance with treatment and longer treatment duration significantly decreased the risk of developing cirrhosis and HCC. HBsAg loss seemed to be a protective factor for cirrhosis/HCC in NAs-treated patients with CHB, and cirrhosis was a confirmed risk factor for HCC development as expected.

Hepatitis B surface antigen loss after discontinuing nucleos(t)ide analogue for treatment of chronic hepatitis B patients is persistent in White patients.

OBJECTIVE: The objective of this study was to determine the long-term clinical outcome and persistence of hepatitis B surface antigen (HBsAg) loss after discontinuation of treatment. BACKGROUND: The prognosis of patients with chronic hepatitis B (CHB) treated with nucleos(t)ide analogues (NAs) who discontinue treatment after loss of HBsAg remains largely unknown, particularly in White patients. PATIENTS AND METHODS: We analysed a cohort of patients with CHB who discontinued NA treatment after loss of HBsAg. A total of 69 patients with hepatitis-B-e antigen-positive or hepatitis-B-e antigen-negative CHB with undetectable HBsAg during NA treatment were included after discontinuation of treatment, and followed up for a median period of 37.8 months (interquartile range: 23.8-54.6 months). RESULTS: At the end of follow-up, none of the patients showed spontaneous reappearance of HBsAg and only one patient had detectable hepatitis B virus DNA (22 IU/ml). Another patient negative for HBsAg and anti-HBs developed hepatitis B virus reactivation without elevated transaminases after treatment with corticosteroids and vincristine for dendritic cell neoplasm, 38 months after withdrawal of the antiviral treatment. Regarding clinical outcome, a patient with cirrhosis developed hepatocellular carcinoma, 6.6 years after discontinuing treatment. None of the patients had hepatic decompensation or underwent liver transplantation. CONCLUSION: HBsAg clearance after discontinuing NAs in patients with CHB is persistent and associated with good prognosis. The risk for developing hepatocellular carcinoma persists among patients with cirrhosis.

Administration of a Nucleoside Analog Promotes Cancer Cell Death in a Telomerase-Dependent Manner.

Telomerase, the end-replication enzyme, is reactivated in malignant cancers to drive cellular immortality. While this distinction makes telomerase an attractive target for anti-cancer therapies, most approaches for inhibiting its activity have been clinically ineffective. As opposed to inhibiting telomerase, we use its activity to selectively promote cytotoxicity in cancer cells. We show that several nucleotide analogs, including 5-fluoro-2'-deoxyuridine (5-FdU) triphosphate, are effectively incorporated by telomerase into a telomere DNA product. Administration of 5-FdU results in an increased number of telomere-induced foci, impedes binding of telomere proteins, activates the ATR-related DNA-damage response, and promotes cell death in a telomerase-dependent manner. Collectively, our data indicate that telomerase activity can be exploited as a putative anti-cancer strategy.

The nucleoside analog GS-441524 strongly inhibits feline infectious peritonitis (FIP) virus in tissue culture and experimental cat infection studies.

Feline infectious peritonitis (FIP) is a common and highly lethal coronavirus disease of domestic cats. Recent studies of diseases caused by several RNA viruses in people and other species indicate that antiviral therapy may be effective against FIP in cats. The small molecule nucleoside analog GS-441524 is a molecular precursor to a pharmacologically active nucleoside triphosphate molecule. These analogs act as an alternative substrate and RNA-chain terminator of viral RNA dependent RNA polymerase. We determined that GS-441524 was non-toxic in feline cells at concentrations as high as 100 uM and effectively inhibited FIPV replication in cultured CRFK cells and in naturally infected feline peritoneal macrophages at concentrations as low as 1 uM. We determined the pharmacokinetics of GS-441524 in cats in vivo and established a dosage that would sustain effective blood levels for 24 h. In an experimental FIPV infection of cats, GS-441524 treatment caused a rapid reversal of disease signs and return to normality with as little as two weeks of treatment in 10/10 cats and with no apparent toxicity.

Increased NK Cell Function After Cessation of Long-Term Nucleos(t)ide Analogue Treatment in Chronic Hepatitis B Is Associated With Liver Damage and HBsAg Loss.

Background: Treatment with nucleos(t)ide analogues (NA) suppresses hepatitis B virus (HBV) DNA but rarely leads to functional cure of chronic hepatitis B (CHB). Following NA cessation, some hepatitis B e antigen (HBeAg)-negative CHB patients experience hepatitis B s antigen (HBsAg) loss. Cellular immune responses, including natural killer (NK) cell responses, explaining virological events following NA treatment cessation remain elusive. Methods: In a single-center prospective trial, 15 HBeAg-negative CHB patients on long-term NA treatment underwent structured NA cessation and were studied longitudinally. The NK cell compartment was assessed using high-dimensional flow cytometry and correlated with the clinical course. Results: Unsupervised stochastic neighbor embedding analysis revealed NA-treated CHB patients to have a significantly affected NK cell compartment compared to controls. Cessation of NA treatment resulted in minor phenotypic alterations, but it significantly augmented NK cell natural cytotoxicity responses in the CHB patients. This increased NK cell functionality correlated with alanine aminotransferase flares in the patients and was particularly enhanced in patients experiencing HBsAg seroclearance at long-term follow-up. Conclusions: Increased NK cell function is associated with active hepatitis and HBsAg seroclearance following structured NA cessation. This adds to our knowledge of the immunological events that develop following cessation of NA treatment in CHB.

Review article: long-term safety of oral anti-viral treatment for chronic hepatitis B.

BACKGROUND: Safety profile of nucleos(t)ide analogues is an important issue in view of its widespread use for decades in patients with chronic hepatitis B (CHB). AIM: To review and evaluate the latest evidence on the safety profiles of the six approved nucleoside analogues. METHODS: Relevant articles related to nucleoside analogue safety were selected for review following extensive language- and date-unrestricted, electronic searches of the literature. RESULTS: Nephrotoxicity has been well reported in patients receiving older generations of nucleotide analogues, namely adefovir dipivoxil and tenofovir disoproxil fumarate (TDF). Yet risks of renal failure and renal replacement therapy were similar in patients treated with nucleoside analogues versus nucleotide analogues in real-life setting. Bone toxicity is closely related to nucleoside analogue effect on renal proximal tubular and phosphaturia. Real-life data demonstrated increased risk of hip fracture in patients receiving adefovir but not TDF. The newly approved tenofovir alafenamide (TAF) has improved renal and bone safety profiles compared to TDF. Long-term use of nucleoside analogues eg entecavir does not increase the risk of other cancers. Muscular toxicity may be seen in telbivudine-treated patients so regular monitoring is advised. Peripheral neuropathy and lactic acidosis are rare adverse events. Latest international guidelines support the use of TDF, telbivudine and lamivudine during pregnancy; breastfeeding is not contraindicated during TDF therapy. CONCLUSIONS: Long-term safety profile of nucleoside analogues is now better defined with more data from large real-life cohorts and clinical trials with long-term follow-up. The new nucleotide analogue, TAF is now available with favourable renal and bone safety profiles.

Dendrimers as nanocarriers for nucleoside analogues.

Dendrimers constitute a class of hyperbranched macromolecules with several potential applications due to their unique properties such as a well-defined structure, multivalency and biocompatibility. These polymers became one of the most promising drug nanocarriers, providing improved solubility of therapeutics, high loading capacity and controllable biodistribution pattern. In addition, the use of dendrimers as drug delivery devices in cancer therapies may help to overcome the resistance mechanisms by transporting activated drug molecules directly to cancer cells. In the recent years, dendrimers were intensively studied for delivery of nucleoside analogues (NAs), essential elements of antiviral therapies, as well as treatments of leukemia, lymphoma and various types of solid tumors. These agents act as antimetabolites, competing with physiological nucleosides, and interacting with intracellular enzymes and nuclear acids to induce cytotoxicity. However, efficiency of NAs-based therapies is often limited by factors like fast metabolism, disadvantageous biodistribution, low solubility and various side effects. In case of treatment of leukemia, target cells usually develop drug resistance, which reduces the activity of nucleoside analogues even further. Thus, drug carrier systems are studied to improve the efficacy and specificity of action of these compounds. In this review, we summarize available data concerning the possibility of application of dendrimers as delivery devices for nucleoside analogues and their active, triphosphate forms.

Viral and Host Responses After Stopping Long-term Nucleos(t)ide Analogue Therapy in HBeAg-Negative Chronic Hepatitis B.

This prospective study investigated viral and host markers after stopping long-term therapy with nucleos(t)ide analogues in noncirrhotic patients with hepatitis B e antigen-negative chronic hepatitis B. After stopping therapy, 13 of 15 patients experienced a virological relapse. Rebound of hepatitis B virus DNA and hepatitis B core-related antigen was associated with induction of plasma tumor necrosis factor, interleukin (IL) 10 , IL-12p70, CXCL10 and subsequent decline in hepatitis B surface antigen (HBsAg), with 20% HBsAg loss after long-term follow-up. The peak levels of hepatitis B virus DNA and hepatitis B core-related antigen after cessation of therapy were positively correlated with the level of HBsAg decline at week 48. Thus, stopping or interrupting NA treatment should be further investigated as a strategy to accelerate HBsAg loss.

Mitochondrial stress induces cellular senescence in an mTORC1-dependent manner.

Although mitochondrial stress is a key determinant of cellular homeostasis, the intracellular mechanisms by which this stress is communicated to the nucleus and its impact on cell fate decisions are not well defined. In this study, we report that activation of mTORC1 signaling triggered by mitochondrial-generated reactive oxygen species (ROS) results in activation of the senescence program. We show that exposure of human fibroblasts to nucleoside analogs commonly used in antiretroviral therapies, and known to induce mitochondrial dysfunction, increases mitochondrial ROS and leads to a rise in intracellular ROS concomitant with activation of mTORC1. In this setting, it appears that mTORC1 activates senescence through HDM2 phosphorylation, facilitating a p53-mediated response. Inhibition of mTORC1 by rapamycin decreases HDM2 phosphorylation and blocks activation of the senescence program in human cells. In addition, decreasing mitochondrial ROS directly blocks mTORC1 signaling and prevents the onset of senescence. Consistent with these results, both total and mitochondrial-specific ROS increased in cells undergoing replicative senescence along with ribosomal p70 phosphorylation. The results reveal a novel link between mitochondrial dysfunction, mTORC1 signaling, and the senescence program.

Oral nucleos(t)ide analogues reduce recurrence and death in chronic hepatitis B-related hepatocellular carcinoma.

BACKGROUND: In patients with chronic hepatitis B (CHB)-related hepatocellular carcinoma (HCC), high viral load was associated with tumour recurrence and deaths. AIMS: To investigate the effect of nucleos(t)ide analogues (NA) on the clinical outcomes after different HCC treatments. METHODS: A territory-wide cohort study was conducted using the database from Hospital Authority. We identified CHB patients with HCC by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes in 2000-2012. HCC treatments, NA use and laboratory parameters were retrieved. The primary endpoint was HCC recurrence and death. A 3-month landmark analysis was used to evaluate the primary outcome in patients with or without NA treatment. RESULTS: A total of 2198 CHB patients (1230 NA-untreated and 968 NA-treated) with HCC, receiving at least one type of HCC treatment were included in the analysis. At a median follow-up of 2.8 (IQR 1.4-4.9) years, tumour recurrence and death occurred in 451 (36.7%) and 578 (47.0%) untreated patients; and in 216 (22.3%) and 301 (31.1%) NA-treated patients respectively. NA therapy reduced the risk of overall HCC recurrence [adjusted sub-hazard ratio (SHR) 0.63, 95% confidence interval (CI) 0.49-0.80; P < 0.001]. The effect was most obvious in patients undergoing resection (SHR = 0.58, 95% CI = 0.37-0.91, P = 0.018). The possibility of NA therapy reducing the risk of death (HR = 0.82, 95% CI = 0.64-1.03, P = 0.092), is most obvious in resection subgroup (HR = 0.64, 95% CI = 0.41-0.99, P = 0.050) but insignificant in the other treatment groups. CONCLUSION: Our findings show that nucleos(t)ide analogues treatment reduces the risk of HCC recurrence in patients with chronic hepatitis B treated by surgical resection.

Synthesis of Novel 4'-Trifluoromethyl-5'-Norcarbocyclic C-Nucleoside Phosphonic Acids as Potent Anti-Leukemic Agents.

The syntheses of novel C-nucleoside phosphonic acids as potential antiviral agents are described. The sugar moiety that served as the nucleoside skeleton was produced starting from commercially available 1,3-dihydroxy cyclopentane. The key C-C bond formation from sugar to base precursor was performed using the Knoevenagel-type condensation. The synthesized compounds exhibited anti-HIV activity and cytotoxicity. Also, the synthesized compounds were screened in vitro for tumor growth inhibitory activity against mouse leukemia cell lines (L-1210, P-815).

Antiviral therapy in the improvement of survival of patients with hepatitis B virus-related hepatocellular carcinoma treated with sorafenib.

BACKGROUND AND AIM: To evaluate the role of antiviral therapy with nucleoside analogs (NAs) in sorafenib-treated patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). METHODS: A retrospective cohort study was done in 151 HBV-related HCC patients treated with sorafenib at Sun Yat-sen University Cancer Center between 2007 and 2012. Overall survival (OS), progression-free survival and adverse events were compared in patients treated with/without NAs. Subgroup analysis and Cox regression analysis were performed to determine the efficiency of NAs and prognostic factors for OS. RESULTS: HBV-related HCC patients (n=151) were identified from our database of HCC patients treated with sorafenib. Patients treated with NAs (antiviral group, n=88) had significantly improved OS compared with the patients who received no NAs (non-antiviral group, n=63; median OS: 16.47 months vs 13.10 months, P=0.03). Patients in the antiviral group had a significant risk reduction of death compared with the non-antiviral group (hazard ratio: 0.67, 95% confidence interval: 0.46-0.98, P=0.04). By subgroup analysis, patients of Barcelona Clinic Liver Cancer (BCLC) stage C and patients with higher presorafenib HBV-DNA level achieved better survival improvement. Antiviral therapy with NAs was one of the independent prognostic factors for OS of HBV-related HCC patients who were treated with sorafenib. CONCLUSION: Antiviral therapy with NAs improved OS of HBV-related HCC patients treated with sorafenib, especially in patients with BCLC stage C disease and higher HBV-DNA level.

The use of anthracycline at first-line compared to alkylating agents or nucleoside analogs improves the outcome of salvage treatments after relapse in follicular lymphoma The REFOLL study by the Fondazione Italiana Linfomi.

Follicular lymphoma (FL) patients experience multiple remissions and relapses and commonly receive multiple treatment lines. A crucial question is whether anthracyclines should be used at first-line or whether they would be better "reserved" for relapse and whether FL outcome can be optimized by definite sequences of treatments. Randomized trials can be hardly designed to address this question. In this retrospective multi-institutional study, time-to-next-treatment after first relapse was analyzed in 510 patients who had received either alkylating agents- or anthracycline- or nucleoside analogs-based chemotherapy with/without rituximab at first-line and different second-line therapies. After a median of 42 months, median time-to-next-treatment after relapse was 41 months (CI95%:34-47 months). After adjustment for covariates, first-line anthracycline-based chemotherapy with/without rituximab was associated with better time-to-next-treatment after any salvage than alkylating agents-based chemotherapy with/without rituximab or nucleoside analogs-based chemotherapy with/without rituximab (HR:0.74, P = 0.027). The addition of rituximab to first-line chemotherapy had no significant impact (HR:1.22, P = 0.140). Autologs stem cell transplantation performed better than any other salvage treatment (HR:0.53, P < 0.001). First-line anthracycline-based chemotherapy significantly improved time-to-next-treatment even in patients receiving salvage autologs stem cell transplantation (P = 0.041). This study supports the concept that in FL previous treatments significantly impact on the outcome of subsequent therapies. The outcome of second-line treatments, either with salvage chemoimmunotherapy or with autologs stem cell transplantation, was better when an anthracycline-containing regimen was used at first-line.