Class A capsid assembly modulator apoptotic elimination of hepatocytes with high HBV core antigen level in vivo is dependent on de novo core protein translation.

Capsid assembly is critical in the hepatitis B virus (HBV) life cycle, mediated by the viral core protein. Capsid assembly is the target for new anti-viral therapeutics known as capsid assembly modulators (CAMs) of which the CAM-aberrant (CAM-A) class induces aberrant shaped core protein structures and leads to hepatocyte cell death. This study aimed to identify the mechanism of action of CAM-A modulators leading to HBV-infected hepatocyte elimination where CAM-A-mediated hepatitis B surface antigen (HBsAg) reduction was evaluated in a stable HBV replicating cell line and in AAV-HBV-transduced C57BL/6, C57BL/6 SCID, and HBV-infected chimeric mice with humanized livers. Results showed that in vivo treatment with CAM-A modulators induced pronounced reductions in hepatitis B e antigen (HBeAg) and HBsAg, associated with a transient alanine amino transferase (ALT) increase. Both HBsAg and HBeAg reductions and ALT increase were delayed in C57BL/6 SCID and chimeric mice, suggesting that adaptive immune responses may indirectly contribute. However, CD8+ T cell depletion in transduced wild-type mice did not impact antigen reduction, indicating that CD8+ T cell responses are not essential. Transient ALT elevation in AAV-HBV-transduced mice coincided with a transient increase in endoplasmic reticulum stress and apoptosis markers, followed by detection of a proliferation marker. Microarray data revealed antigen presentation pathway (major histocompatibility complex class I molecules) upregulation, overlapping with the apoptosis. Combination treatment with HBV-specific siRNA demonstrated that CAM-A-mediated HBsAg reduction is dependent on de novo core protein translation. To conclude, CAM-A treatment eradicates HBV-infected hepatocytes with high core protein levels through the induction of apoptosis, which can be a promising approach as part of a regimen to achieve functional cure. IMPORTANCE: Treatment with hepatitis B virus (HBV) capsid assembly modulators that induce the formation of aberrant HBV core protein structures (CAM-A) leads to programmed cell death, apoptosis, of HBV-infected hepatocytes and subsequent reduction of HBV antigens, which differentiates CAM-A from other CAMs. The effect is dependent on the de novo synthesis and high levels of core protein.

Nanoparticle delivery of Tat synergizes with classical latency reversal agents to express HIV antigen targets.

Limited cellular levels of the HIV transcriptional activator Tat are one contributor to proviral latency that might be targeted in HIV cure strategies. We recently demonstrated that lipid nanoparticles containing HIV tat mRNA induce HIV expression in primary CD4 T cells. Here, we sought to further characterize tat mRNA in the context of several benchmark latency reversal agents (LRAs), including inhibitor of apoptosis protein antagonists (IAPi), bromodomain and extra-Terminal motif inhibitors (BETi), and histone deacetylase inhibitors (HDACi). tat mRNA reversed latency across several different cell line models of HIV latency, an effect dependent on the TAR hairpin loop. Synergistic enhancement of tat mRNA activity was observed with IAPi, HDACi, and BETi, albeit to variable degrees. In primary CD4 T cells from durably suppressed people with HIV, tat mRNA profoundly increased the frequencies of elongated, multiply-spliced, and polyadenylated HIV transcripts, while having a lesser impact on TAR transcript frequencies. tat mRNAs alone resulted in variable HIV p24 protein induction across donors. However, tat mRNA in combination with IAPi, BETi, or HDACi markedly enhanced HIV RNA and protein expression without overt cytotoxicity or cellular activation. Notably, combination regimens approached or in some cases exceeded the latency reversal activity of maximal mitogenic T cell stimulation. Higher levels of tat mRNA-driven HIV p24 induction were observed in donors with larger mitogen-inducible HIV reservoirs, and expression increased with prolonged exposure time. Combination LRA strategies employing both small molecule inhibitors and Tat delivered to CD4 T cells are a promising approach to effectively target the HIV reservoir.

Interaction between Toll-Like Receptor 9-CpG Oligodeoxynucleotides and Hepatitis B Virus Virions Leads to Entry Inhibition in Hepatocytes and Reduction of Alpha Interferon Production by Plasmacytoid Dendritic Cells.

We previously reported that Toll-like receptor 9 (TLR9)-CpG oligonucleotides could inhibit the establishment of hepatitis B virus (HBV) infections in hepatocytes. Our aim was to uncover the underlying mechanisms of this inhibition. HepaRG cells, RPMI-B lymphoblastoma cells, and primary plasmacytoid dendritic cells (pDCs) exposed to HBV and TLR9 ligands/agonists in various configurations were used. We observed an inhibition of HBV infection upon TLR9 stimulations only when agonist was applied during inoculation. This inhibition was independent of interleukin-6 (IL-6)/interferon-inducible protein 10 (IP-10) production as well as of TLR9 expression in hepatocytes. We further demonstrated an entry inhibition mechanism by showing a noncovalent binding of TLR9 agonist to HBV particles. Besides inhibiting HBV entry into hepatocytes, this biophysical interaction between HBV virions and TLR9 agonist was responsible for a reduction of alpha interferon (IFN-α) expression by pDCs. Interestingly, subviral particles composed of only HBsAg were able to genuinely inhibit the TLR9 pathway, without titrating TLR9 ligands. To conclude, our data suggest that synthetic TLR9-CpG oligonucleotides can strongly inhibit HBV entry by "coating" HBV virions and thereby preventing their interaction with cellular receptor. This titration effect of TLR9 agonist is also artifactually responsible for the inhibition of TLR9 engagement in pDCs, whereas a genuine inhibition of this innate pathway was confirmed with HBsAg subviral particles.

The PA Endonuclease Inhibitor RO-7 Protects Mice from Lethal Challenge with Influenza A or B Viruses.

Current influenza treatment relies on a single class of antiviral drugs, the neuraminidase inhibitors (NAIs), raising concern over the potential emergence of resistant variants and necessitating the development of novel drugs. In recent years, investigational inhibitors targeting the endonuclease activity of the influenza acidic polymerase (PA) protein have yielded encouraging results, although there are only limited data on their in vivo efficacy. Here, we examined the antiviral potential of the PA endonuclease inhibitor RO-7 in prophylactic and therapeutic regimens in BALB/c mice inoculated with influenza A/California/04/2009 (H1N1)pdm09 or B/Brisbane/60/2008 viruses, which represent currently circulating antigenic variants. RO-7 was administered to mice intraperitoneally twice daily at dosages of 6, 15, or 30 mg/kg/day for 5 days, starting 4 h before or 24 or 48 h after virus inoculation, and showed no adverse effects. Prophylactic administration completely protected mice from lethal infection by influenza A or B virus. The level of therapeutic protection conferred depended upon the time of treatment initiation and RO-7 dosage, resulting in 60 to 100% and 80 to 100% survival with influenza A and B viruses, respectively. RO-7 treatment significantly decreased virus titers in the lung and lessened the extent and severity of lung damage. No PA endonuclease-inhibitor resistance was observed in viruses isolated from lungs of RO-7-treated mice, and the viruses remained susceptible to the drug at nanomolar concentrations in phenotypic assays. These in vivo efficacy results further highlight the potential of RO-7 for development as antiviral therapy for influenza A and B virus infections.

A Novel Endonuclease Inhibitor Exhibits Broad-Spectrum Anti-Influenza Virus Activity In Vitro.

Antiviral drugs are important in preventing and controlling influenza, particularly when vaccines are ineffective or unavailable. A single class of antiviral drugs, the neuraminidase inhibitors (NAIs), is recommended for treating influenza. The limited therapeutic options and the potential risk of antiviral resistance are driving the search for additional small-molecule inhibitors that act on influenza virus proteins. The acid polymerase (PA) of influenza viruses is a promising target for new antivirals because of its essential role in initiating virus transcription. Here, we characterized a novel compound, RO-7, identified as a putative PA endonuclease inhibitor. RO-7 was effective when added before the cessation of genome replication, reduced polymerase activity in cell-free systems, and decreased relative amounts of viral mRNA and genomic RNA during influenza virus infection. RO-7 specifically inhibited the ability of the PA endonuclease domain to cleave a nucleic acid substrate. RO-7 also inhibited influenza A viruses (seasonal and 2009 pandemic H1N1 and seasonal H3N2) and B viruses (Yamagata and Victoria lineages), zoonotic viruses (H5N1, H7N9, and H9N2), and NAI-resistant variants in plaque reduction, yield reduction, and cell viability assays in Madin-Darby canine kidney (MDCK) cells with nanomolar to submicromolar 50% effective concentrations (EC50s), low toxicity, and favorable selective indices. RO-7 also inhibited influenza virus replication in primary normal human bronchial epithelial cells. Overall, RO-7 exhibits broad-spectrum activity against influenza A and B viruses in multiple in vitro assays, supporting its further characterization and development as a potential antiviral agent for treating influenza.

Interferon-free regimens containing setrobuvir for patients with genotype 1 chronic hepatitis C: a randomized, multicenter study.

BACKGROUND & AIMS: Setrobuvir is a direct-acting antiviral (DAA) non-nucleoside inhibitor of hepatitis C virus (HCV) polymerase. This study examined interferon-free combinations containing setrobuvir, a ritonavir-boosted protease inhibitor (danoprevir/r) and ribavirin, with/without the nucleoside inhibitor mericitabine in HCV genotype (G)1 patients. METHODS: Non-cirrhotic treatment-naïve patients (N = 110) were randomized to five groups. Three groups received a 14-day mericitabine/ribavirin lead-in followed by treatment with 3 DAAs (setrobuvir, danoprevir/r, mericitabine) plus ribavirin for 12 weeks (Group A: G1a; D: G1b) or 24 weeks (B: G1a), and two groups received 2 DAAs (setrobuvir, danoprevir/r) plus ribavirin for 12 weeks (E: G1b) or 24 weeks (C: G1a). Efficacy was defined as sustained virological response (HCV RNA <25 IU/ml after 12 weeks' follow-up, SVR12). RESULTS: Two groups met predefined futility criteria for breakthrough (C) or relapse (A) and were discontinued. SVR12 rates were 42.9% (3/7) and 74.1% (20/27) in G1a patients in Groups A and B, respectively, and 95.7% (22/23) and 68.2% (15/22) in G1b patients in Groups D and E respectively. All G1a patients assigned to 24 weeks of treatment who experienced a decrease in HCV RNA of ≥2.3 log10 IU by the end of the lead-in period (n = 28) achieved SVR12. Overall, treatment was well tolerated and most adverse events were mild to moderate. No major safety signals were identified. CONCLUSIONS: An interferon-free setrobuvir-based regimen (3 DAAs plus ribavirin) is safe and effective in treatment-naïve G1 patients.

Ritonavir-boosted danoprevir plus peginterferon alfa-2a and ribavirin in Asian chronic hepatitis C patients with or without cirrhosis.

BACKGROUND AND AIM: Chronic hepatitis C is an important public health problem in Asia. We evaluated the safety, efficacy, and pharmacokinetics of fixed-dose ritonavir-boosted danoprevir plus peginterferon alfa-2a/ribavirin in treatment-naive Asian patients with chronic hepatitis C virus (HCV) genotype (G)1 infection. METHODS: Treatment-naive G1 patients in Taiwan, Thailand, and Korea with serum HCV-RNA level ≥ 105 IU/mL received ritonavir-boosted danoprevir 125/100 mg twice daily plus peginterferon alfa-2a/ribavirin for either 12 (noncirrhotic patients: Arm A, n = 34) or 24 weeks (cirrhotic patients: Arm B, n = 27) in this phase II open-label study. Sustained virologic response was defined as HCV-RNA < 25 IU/mL 12 weeks after end of treatment (SVR12). RESULTS: Similar SVR12 rates were achieved in Arms A (88.2%; 95% confidence interval, 73.4-95.3%) and B (88.9%; 71.9-96.2%). Most patients had G1b infection, among whom SVR12 rates in Arms A and B were 96.7% and 91.7%, respectively. The overall SVR12 rate was 94.0% in noncirrhotic Taiwanese patients (100% in the subset of G1b patients). No patients withdrew for safety reasons. Three (11%) cirrhotic patients (Arm B) experienced serious adverse events, none of which was considered to be related to treatment. No Grade 3/4 alanine aminotransferase elevations were reported. The pharmacokinetic properties of danoprevir were broadly overlapping in noncirrhotic and cirrhotic patients both on Days 1 and 14. CONCLUSIONS: Ritonavir-boosted danoprevir plus peginterferon alfa-2a/ribavirin produced sustained virologic response rates > 90% after 12 weeks' treatment in noncirrhotic and 24 weeks' treatment in cirrhotic Asian patients with G1b infection and was well tolerated. These regimens are well suited to countries where G1b predominates.

A novel immuno-competitive capture mass spectrometry strategy for protein-protein interaction profiling reveals that LATS kinases regulate HCV replication through NS5A phosphorylation.

Mapping protein-protein interactions is essential to fully characterize the biological function of a protein and improve our understanding of diseases. Affinity purification coupled to mass spectrometry (AP-MS) using selective antibodies against a target protein has been commonly applied to study protein complexes. However, one major limitation is a lack of specificity as a substantial part of the proposed binders is due to nonspecific interactions. Here, we describe an innovative immuno-competitive capture mass spectrometry (ICC-MS) method to allow systematic investigation of protein-protein interactions. ICC-MS markedly increases the specificity of classical immunoprecipitation (IP) by introducing a competition step between free and capturing antibody prior to IP. Instead of comparing only one experimental sample with a control, the methodology generates a 12-concentration antibody competition profile. Label-free quantitation followed by a robust statistical analysis of the data is then used to extract the cellular interactome of a protein of interest and to filter out background proteins. We applied this new approach to specifically map the interactome of hepatitis C virus (HCV) nonstructural protein 5A (NS5A) in a cellular HCV replication system and uncovered eight new NS5A-interacting protein candidates along with two previously validated binding partners. Follow-up biological validation experiments revealed that large tumor suppressor homolog 1 and 2 (LATS1 and LATS2, respectively), two closely related human protein kinases, are novel host kinases responsible for NS5A phosphorylation at a highly conserved position required for optimal HCV genome replication. These results are the first illustration of the value of ICC-MS for the analysis of endogenous protein complexes to identify biologically relevant protein-protein interactions with high specificity.

Randomized study of danoprevir/ritonavir-based therapy for HCV genotype 1 patients with prior partial or null responses to peginterferon/ribavirin.

BACKGROUND & AIMS: Chronic hepatitis C treatment for prior non-responders to peginterferon (PegIFN)/ribavirin remains suboptimal. The MATTERHORN study evaluated regimens containing ritonavir-boosted danoprevir (danoprevir/r) in prior PegIFN alfa/ribavirin non-responders. METHODS: Prior partial responders (N=152) were randomized to 24 weeks of twice-daily danoprevir/r 100/100mg, mericitabine 1000 mg and ribavirin 1000/1200 mg (IFN-free); danoprevir/r plus PegIFN alfa-2a/ribavirin (triple); or danoprevir/r, mericitabine and PegIFN alfa-2a/ribavirin (Quad). Prior null responders (N=229) were randomized to 24 weeks of IFN-free therapy, or quad alone (Quad 24) or quad plus 24-weeks of PegIFN alfa-2a/ribavirin (Quad 48). The primary endpoint was sustained virological response (HCV RNA <25 IU/ml) 24 weeks after end-of-treatment (SVR24). Due to high relapse rates, genotype (G) 1a patients in IFN-free arms were offered additional PegIFN alfa-2a/ribavirin. RESULTS: Among prior partial responders, SVR24 rates were 46.2%, 51.0%, and 86.0%, in the IFN-free, Triple and Quad arms, respectively; among prior null responders, SVR24 rates were 45.5%, 80.5%, and 83.8% respectively. Relapse rates were lower and SVR24 rates higher in G1b-infected than G1a-infected patients. SVR24 rates in G1a and G1b patients randomized to Quad were 75.0% and 96.2%, respectively, in the partial Quad arm, and 68.1% and 100%, respectively, in the null Quad 24 arm. Treatment failure was associated with resistance to danoprevir, but not to mericitabine, and was more common in G1a infected patients. Treatment was well-tolerated. CONCLUSIONS: Danoprevir/r, mericitabine plus PegIFN alfa-2a/ribavirin was well-tolerated and produced high overall SVR24 rates in prior partial and null responders to PegIFN alfa/ribavirin. In contrast, IFN-free regimens were associated with unacceptably high relapse rates.

Mericitabine and ritonavir-boosted danoprevir with or without ribavirin in treatment-naive HCV genotype 1 patients: INFORM-SVR study.

BACKGROUND & AIMS: Safety and tolerability of peginterferon-based hepatitis C virus (HCV) infection therapy remains suboptimal, even when direct-acting antiviral agents are added. This study assessed the efficacy, safety and tolerability of mericitabine combined with ritonavir-boosted danoprevir (danoprevir/r) ± ribavirin for up to 24 weeks in treatment-naïve HCV genotype (G)1 infected patients. METHODS: Patients received twice daily mericitabine (1000 mg) and danoprevir/r (100 mg/100 mg) plus either ribavirin (1000/1200 mg/day; Arm A) or placebo (Arm B) for 12 or 24 weeks. Patients with HCV RNA <43 IU/ml between Weeks 2 and 8 and HCV RNA <15 IU/ml at Week 10 were rerandomized (1:1) at Week 12 to discontinue/continue assigned regimens until Week 24. Because of unacceptable relapse rates in both 12-week arms and in ribavirin-free Arm B, treatment was extended to 24 weeks and patients in Arm B received peginterferon alfa-2a/ribavirin. The primary outcome was sustained virological response 24 weeks after end of treatment (SVR24). RESULTS: In Arm A, the SVR24 rate in patients receiving 24 weeks of therapy was 37.9% (25/66); 63.6% (14/22) in G1b and 25.0% (11/44) in G1a patients. Virologic breakthrough and relapse were associated with danoprevir-resistant virus in most cases. The mericitabine-resistance mutation (NS5BS282T) was detected in two patients bearing dual resistant virus NS3 R155K/NS5B S282T and dual resistance mutation L159F/L320F in one patient. Treatment was safe and well tolerated. CONCLUSIONS: Mericitabine, danoprevir/r plus ribavirin for 24 weeks were safe and well tolerated. However, SVR rates were poor, achieving rates of only 25.0% in G1a and 63.6% in G1b patients.

DAUPHINE: a randomized phase II study of danoprevir/ritonavir plus peginterferon alpha-2a/ribavirin in HCV genotypes 1 or 4.

BACKGROUND & AIMS: Danoprevir is a hepatitis C virus (HCV) protease inhibitor with activity against genotypes (G)1/G4, which is maintained at lower doses by ritonavir-boosting. We report results of a large, randomized, active-controlled phase IIb study of ritonavir-boosted danoprevir (danoprevir/r) plus peginterferon alpha-2a/ribavirin (P/R) in treatment-naive patients with HCV G1/4 infection. METHODS: Treatment-naive patients with HCV G1/4 infection were randomized to twice-daily danoprevir/r 200/100 mg (A, n = 92); 100/100 mg (B, n = 93); or 50/100 mg (C, n = 94) plus P/R for 24 weeks; twice-daily danoprevir/r 100/100 mg (D, n = 94) plus P/R for 12 or 24 weeks; or P/R alone (E, n = 44) for 48 weeks. Patients in the response-guided therapy arm (D) with an extended rapid virological response (eRVR2: HCV RNA <15 IU/ml during Weeks 2-10) stopped all therapy at Week 12; non-eRVR2 patients continued all treatment to Week 24. The primary efficacy endpoint was sustained the virological response (SVR24: HCV RNA <15 IU/ml after 24 weeks of untreated follow-up). RESULTS: SVR24 rates in Arms A, B, C, D and E were 89.1%, 78.5%, 66.0%, 69.1% and 36.4%, respectively, in the overall population; 83.6%, 69.6%, 60.3%, 59.2% and 38.5% in G1a-infected patients, 96.6%, 93.1%, 73.1%, 78.4% and 28.6% in G1b-infected patients and 100%, 87.5%, 100%, 100% and 66.7% in G4-infected patients. Danoprevir/r plus P/R was generally well tolerated compared with P/R alone. There was a higher incidence of serious adverse events in danoprevir-treatment arms, but most were associated with P/R. CONCLUSIONS: The combination of danoprevir/r plus P/R is efficacious in treatment-naïve patients with HCV genotype 1 or 4 infection.

In vivo emergence of a novel mutant L159F/L320F in the NS5B polymerase confers low-level resistance to the HCV polymerase inhibitors mericitabine and sofosbuvir.

BACKGROUND: Resistance to mericitabine (prodrug of HCV NS5B polymerase inhibitor PSI-6130) is rare and conferred by the NS5B S282T mutation. METHODS: Serum HCV RNA from patients who experienced viral breakthrough, partial response, or nonresponse in 2 clinical trials in which patients received mericitabine plus peginterferon alfa-2a (40KD)/ribavirin were analyzed by population and clonal sequence analysis as well as phenotypic assay for assessment of in vivo mericitabine resistance. RESULTS: Among 405 patients treated with mericitabine plus peginterferon alfa-2a/ribavirin in PROPEL and JUMP-C, virologic breakthrough or nonresponse were not observed; 12 patients experienced a partial response. The NS5B S282T resistance mutation was not observed in any patient. A number of treatment-associated NS5B changes were observed and characterized. A novel double mutant (L159F/L320F) with impaired replication capacity was detected in one HCV genotype 1b-infected patient. Introduction of double mutant L159F/L320F into genotype 1a (H77) and 1b (Con-1) replicons, respectively, increased the EC50 for mericitabine by 3.1- and 5.5-fold and the EC90 by 3.1- and 8.9-fold. The double mutant also decreased susceptibility to sofosbuvir (GS-7977) and GS-938 but not setrobuvir, relative to wild-type. CONCLUSIONS: A novel and replication-deficient double mutation (L159F/L320F) confers low-level resistance to mericitabine and cross-resistance to both sofosbuvir and GS-938. CLINICAL TRIALS REGISTRATION: NCT00869661, NCT01057667.

Identification of the NS5B S282T resistant variant and two novel amino acid substitutions that affect replication capacity in hepatitis C virus-infected patients treated with mericitabine and danoprevir.

Baseline and posttreatment samples from hepatitis C virus (HCV) genotype (GT) 1-infected patients who received a combination of danoprevir and mericitabine from a phase II clinical study (INFORM-SVR) were analyzed. In addition to resistance monitoring, sequencing and phenotypic assays were combined with statistical analysis to identify potential novel amino acid substitutions associated with treatment outcome. The NS5B S282T substitution associated with mericitabine resistance was identified in 2/30 viral breakthrough patients and was replaced by wild-type viruses after cessation of drug treatment (during follow-up). The NS3 R155K substitution associated with danoprevir resistance was also observed in these 2 patients. All 69 GT 1a-infected patients who experienced viral breakthrough on treatment or relapsed during follow-up (relapsers) developed NS3 R155K. Among GT 1b-infected patients, substitutions at the danoprevir resistance locus NS3 D168 were observed in 15/20 subjects, whereas substitutions at the danoprevir resistance locus NS3 R155 were observed in 5/20 subjects. Interestingly, the baseline polymorphism NS5B Q47H was more prevalent in GT 1a-infected patients who achieved a sustained virologic response at follow-up week 24 (SVR24) than in non-SVR24 patients (2/13 versus 0/72), and a postbaseline NS3 S122G substitution was more prevalent in GT 1a-infected patients with viral breakthrough than in relapsers (4/22 versus 0/47). Neither substitution conferred resistance to danoprevir or mericitabine, but the substitutions reduced (NS5B Q47H) or improved (NS3 S122G) replication capacity by 2- to 4-fold. The NS5B S282T mericitabine-resistant variant was rare and did not persist once drug was discontinued. NS5B Q47H and NS3 S122G are two newly identified substitutions that affected replication capacity and were enriched in distinct treatment response groups. (This study has been registered at ClinicalTrials.gov under registration no. NCT01278134.).

Efficacy and safety of danoprevir-ritonavir plus peginterferon alfa-2a-ribavirin in hepatitis C virus genotype 1 prior null responders.

Danoprevir (DNV) is a hepatitis C virus (HCV) protease inhibitor that achieves high sustained virologic response (SVR) rates in combination with peginterferon alfa-2a-ribavirin in treatment-naive HCV genotype 1 (G1)-infected patients. This study explored the efficacy and safety of ritonavir-boosted DNV (DNVr) plus peginterferon alfa-2a-ribavirin in G1-infected prior peginterferon-ribavirin null responders. Null responders (<2-log10 reduction in HCV RNA level at week 12) were given an open-label combination of 100 mg of ritonavir and 100 mg of DNV (100/100 mg DNVr) every 12 h (q12h) plus peginterferon alfa-2a-ribavirin for 12 weeks. All patients achieving an early virologic response (EVR; ≥2-log10 decrease in HCV RNA by week 12) continued treatment with peginterferon alfa-2a-ribavirin; those without an EVR discontinued all study drugs. Twenty-four prior null responders were enrolled; 16 patients (67%) were infected with HCV G1b, and 8 (33%) were infected with G1a. Ninety-six percent of patients had an IL28B non-CC genotype. A sustained virologic response at 24 weeks posttreatment (SVR24) was achieved in 67% of patients, with a higher rate in G1b-infected (88%) than G1a-infected (25%) patients. Resistance-related breakthrough occurred in 4/8 G1a and 1/16 G1b patients through the DNV resistance-associated variant (RAV) NS3 R155K. NS3 R155K was also detected in 2/2 G1a patients who relapsed. Treatment was well tolerated. Two patients withdrew prematurely from study medications due to adverse events. Two serious adverse events were reported; both occurred after completion of DNVr therapy and were considered unrelated to treatment. No grade 3 or 4 alanine aminotransferase (ALT) elevations were observed. DNVr plus peginterferon alfa-2a-ribavirin demonstrated high SVR24 rates in HCV G1b-infected prior null responders and was well tolerated. (This study has been registered at ClinicalTrials.gov under registration no. NCT01185860.).

Randomized controlled trial of danoprevir plus peginterferon alfa-2a and ribavirin in treatment-naïve patients with hepatitis C virus genotype 1 infection.

BACKGROUND & AIMS: The combination of a hepatitis C virus (HCV) protease inhibitor, peginterferon, and ribavirin is the standard of care for patients with HCV genotype 1 infection. We report the efficacy and safety of response-guided therapy with danoprevir (a potent second-generation protease inhibitor), peginterferon alfa-2a (40 KD), and ribavirin in these patients. METHODS: Treatment-naïve patients (N = 237) were randomly assigned to groups given 12 weeks of danoprevir (300 mg every 8 hours; 600 mg every 12 hours, and 900 mg every 12 hours) or placebo plus peginterferon alfa-2a and ribavirin, followed by peginterferon alfa-2a and ribavirin. Patients given danoprevir who had an extended rapid virologic response (eRVR4-20: HCV RNA <15 IU/mL during weeks 4-20) stopped therapy at week 24; those without an eRVR4-20 continued therapy to 48 weeks. Patients who were given placebo received 48 weeks of peginterferon alfa-2a and ribavirin. The primary efficacy end point was sustained virologic response (SVR: HCV RNA <15 IU/mL after 24 weeks without treatment). RESULTS: Rates of SVR were higher among patients given danoprevir 300 mg (68%), 600 mg (85%), and 900 mg (76%) than placebo (42%) (95% confidence interval: 26%-59%). Seventy-nine percent of patients given danoprevir 600 mg had an eRVR4-20; among these, 96% had an SVR. Serious adverse events were reported in 7% to 8% of patients given danoprevir and 19% given placebo. Four patients given danoprevir (1 patient in the 600-mg group and 3 in the 900-mg group) had reversible, grade 4 increases in alanine aminotransferase, which led to early discontinuation of the 900-mg arm of the study. CONCLUSIONS: The combination of danoprevir, peginterferon alfa-2a, and ribavirin leads to high rates of SVR in patients with HCV genotype 1 infection, but high doses of danoprevir can lead to grade 4 increases in alanine aminotransferase. Studies of lower doses of danoprevir with ritonavir, to reduce overall danoprevir exposure while maintaining potent antiviral activity, are underway; Clinicaltrials.gov number, NCT00963885.

JUMP-C: a randomized trial of mericitabine plus pegylated interferon alpha-2a/ribavirin for 24 weeks in treatment-naïve HCV genotype 1/4 patients.

UNLABELLED: Mericitabine is a selective nucleoside analog inhibitor of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase, with activity across all HCV genotypes. Treatment-naïve patients infected with HCV genotype 1 or 4 were randomized to 24 weeks of double-blind treatment with either mericitabine 1,000 mg (N = 81) or placebo (N = 85) twice-daily (BID) in combination with pegylated interferon alpha-2a (Peg-IFNα-2a)/ribavirin (RBV). Patients randomized to mericitabine with HCV RNA <15 IU/mL from week 4 to 22 (extended rapid virologic response; eRVR) stopped all treatment at week 24; all other patients continued Peg-IFNα-2a/RBV to complete 48 weeks of treatment. The primary efficacy endpoint was sustained virologic response (SVR; HCV RNA <15 IU/mL after 24 weeks of treatment-free follow-up). SVR was achieved in 56.8% (95% confidence interval [CI]: 45.9-67.0) of mericitabine-treated patients and 36.5% (95% CI: 27.0-47.1) of placebo-treated patients (Δ = 20.3%; 95% CI 5.5-35.2). SVR rates were higher in mericitabine- than placebo-treated patients when subdivided by IL28B genotype (CC, 77.8% versus 56.0%; non-CC, 44.1% versus 16.2%) and hepatic fibrosis (noncirrhotic, 63.3% versus 41.9%; cirrhotic, 38.1% versus 21.7%). Overall relapse rates were 27.7% and 32.0% in mericitabine- and placebo-treated patients, respectively. No evidence of NS5B S282T-variant virus or phenotypic resistance to mericitabine was observed in the one patient who experienced partial response. No S282T variants were detected in any baseline samples. The safety profile of mericitabine was similar to that of, and fewer patients in the mericitabine than in the placebo group discontinued treatment for safety reasons. CONCLUSION: A 24-week response-guided combination regimen of mericitabine 1,000 mg BID plus Peg-IFNα-2a/RBV is well tolerated and more effective than a standard 48-week course of Peg-IFNα-2a/RBV.

PROPEL: a randomized trial of mericitabine plus peginterferon alpha-2a/ribavirin therapy in treatment-naïve HCV genotype 1/4 patients.

UNLABELLED: Mericitabine is a nucleoside analog polymerase inhibitor of hepatitis C virus (HCV). Treatment-naïve HCV genotype 1 or 4 patients were randomized to double-blind treatment with oral mericitabine at a dosage of 500 mg twice-daily (BID) for 12 weeks (A), 1,000 mg BID for 8 (B) or 12 weeks (C and D), or placebo BID for 12 weeks (E). All patients received pegylated interferon alpha-2a (Peg-IFNα-2a; 40 kD)/ribavirin (RBV) at standard doses for 24 or 48 weeks during and after mericitabine/placebo therapy. Patients in arms A-C who maintained a virologic response (VR) (HCV RNA <15 IU/mL) from weeks 4 to 22 stopped all treatment at week 24; all other patients (arms A-E) continued Peg-IFNα-2a/RBV to complete 48 weeks. The primary outcome was sustained VR (SVR) (HCV RNA <15 IU/mL after 24 weeks of untreated follow-up; SVR-24). VR rates were higher in arms A-D than in arm E at weeks 4 and 12 overall, in patients with and without cirrhosis and in patients with CC and non-CC IL28B genotypes. However, the overall SVR-24 rate in arms D (50.6%) and E (placebo, 51.2%) was similar and those in the response-guided therapy arms A, B, and C were lower (48.8%, 42.0%, and 32.9%, respectively). No viral breakthrough or mericitabine-resistance mutations (S282T) were observed during mericitabine therapy. CONCLUSION: Treatment with mericitabine plus Peg-IFNα-2a/RBV for 8 or 12 weeks provided potent suppression of HCV RNA, was well tolerated, and did not select resistant variants, but did not increase SVR rates, compared to placebo. IFN-free and IFN-containing trials of mericitabine of longer treatment duration are ongoing.

Retreatment with HBV siRNA Results in Additional Reduction in HBV Antigenemia and Immune Stimulation in the AAV-HBV Mouse Model.

BACKGROUND AND AIMS: Treatment with siRNAs that target HBV has demonstrated robust declines in HBV antigens. This effect is also observed in the AAV-HBV mouse model, which was used to investigate if two cycles of GalNAc-HBV-siRNA treatment could induce deeper declines in HBsAg levels or prevent rebound, and to provide insights into the liver immune microenvironment. METHODS: C57Bl/6 mice were transduced with one of two different titers of AAV-HBV for 28 days, resulting in stable levels of HBsAg of about 103 or 105 IU/mL. Mice were treated for 12 weeks (four doses q3wk) per cycle with 3 mg/kg of siRNA-targeting HBV or an irrelevant sequence either once (single treatment) or twice (retreatment) with an 8-week treatment pause in between. Blood was collected to evaluate viral parameters. Nine weeks after the last treatment, liver samples were collected to perform phenotyping, bulk RNA-sequencing, and immunohistochemistry. RESULTS: Independent of HBsAg baseline levels, treatment with HBV-siRNA induced a rapid decline in HBsAg levels, which then plateaued before gradually rebounding 12 weeks after treatment stopped. A second cycle of HBV-siRNA treatment induced a further decline in HBsAg levels in serum and the liver, reaching undetectable levels and preventing rebound when baseline levels were 103 IU/mL. This was accompanied with a significant increase in inflammatory macrophages in the liver and significant upregulation of regulatory T-cells and T-cells expressing immune checkpoint receptors. CONCLUSIONS: Retreatment induced an additional decline in HBsAg levels, reaching undetectable levels when baseline HBsAg levels were 3log10 or less. This correlated with T-cell activation and upregulation of Trem2.

mRNA Therapeutic Vaccine for Hepatitis B Demonstrates Immunogenicity and Efficacy in the AAV-HBV Mouse Model.

Chronic infection with hepatitis B virus (HBV) develops in millions of patients per year, despite the availability of effective prophylactic vaccines. Patients who resolve acute HBV infection develop HBV-specific polyfunctional T cells accompanied by neutralizing antibodies, while in patients with chronic hepatitis B (CHB), immune cells are dysfunctional and impaired. We describe a lipid nanoparticle (LNP)-formulated mRNA vaccine, optimized for the expression of HBV core, polymerase, and surface (preS2-S) antigens with the aim of inducing an effective immune response in patients with CHB. Prime and prime/boost vaccination with LNP-formulated mRNA encoding for core, pol, and/or preS2-S dosing strategies were compared in naive C57BL/6 and BALB/c mice. Immune responses were assessed by IFN-γ ELISpot, intracellular cytokine staining (ICS), and ELISA for antibody production, whereas anti-viral efficacy was evaluated in the AAV-HBV mouse model. The mRNA vaccine induced strong antigen-specific polyfunctional T cell responses in these mouse models, accompanied by the emergence of anti-HBs and anti-HBe antibodies. After three immunizations, the antigen-specific immune stimulation resulted in up to 1.7 log10 IU/mL reduction in systemic HBV surface antigen (HBsAg), accompanied by a transient drop in systemic HBeAg, and this was observed in 50% of the AAV-HBV-transduced mice in the absence of additional modalities such as adjuvants, HBsAg reducing agents, or checkpoint inhibitors. However, no treatment-related effect on viremia was observed in the liver. These results warrant further optimization and evaluation of this mRNA vaccine as a candidate in a multimodal therapeutic regimen for the treatment of chronic HBV infection.

Spiro-Azetidine Oxindoles as Long-Acting Injectables for Pre-Exposure Prophylaxis against Respiratory Syncytial Virus Infections.

Respiratory syncytial virus (RSV) is a major cause of hospitalization in infants, the elderly, and immune-compromised patients. While a half-life extended monoclonal antibody and 2 vaccines have recently been approved for infants and the elderly, respectively, options to prevent disease in immune-compromised patients are still needed. Here, we describe spiro-azetidine oxindoles as small molecule RSV entry inhibitors displaying favorable potency, developability attributes, and long-acting PK when injected as an aqueous suspension, suggesting their potential to prevent complications following RSV infection over a period of 3 to 6 months with 1 or 2 long-acting intramuscular (IM) or subcutaneous (SC) injections in these immune-compromised patients.