Viral Resistance Analyses From the Remdesivir Phase 3 Adaptive COVID-19 Treatment Trial-1 (ACTT-1).

BACKGROUND: Remdesivir is approved for treatment of coronavirus disease 2019 (COVID-19) in nonhospitalized and hospitalized adult and pediatric patients. Here we present severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resistance analyses from the phase 3 ACTT-1 randomized placebo-controlled trial conducted in adult participants hospitalized with COVID-19. METHODS: Swab samples were collected at baseline and longitudinally through day 29. SARS-CoV-2 genomes were sequenced using next-generation sequencing. Phenotypic analysis was conducted directly on participant virus isolates and/or using SARS-CoV-2 subgenomic replicons expressing mutations identified in the Nsp12 target gene. RESULTS: Among participants with both baseline and postbaseline sequencing data, emergent Nsp12 substitutions were observed in 12 of 31 (38.7%) and 12 of 30 (40.0%) participants in the remdesivir and placebo arms, respectively. No emergent Nsp12 substitutions in the remdesivir arm were observed in more than 1 participant. Phenotyping showed low to no change in susceptibility to remdesivir relative to wild-type Nsp12 reference for the substitutions tested: A16V (0.8-fold change in EC50), P323L + V792I (2.2-fold), C799F (2.5-fold), K59N (1.0-fold), and K59N + V792I (3.4-fold). CONCLUSIONS: The similar rate of emerging Nsp12 substitutions in the remdesivir and placebo arms and the minimal change in remdesivir susceptibility among tested substitutions support a high barrier to remdesivir resistance development in COVID-19 patients. Clinical Trials Registration. NCT04280705.

Remdesivir and GS-441524 Retain Antiviral Activity against Delta, Omicron, and Other Emergent SARS-CoV-2 Variants.

Genetic variation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in the emergence and rapid spread of multiple variants throughout the pandemic, of which Omicron is currently the predominant variant circulating worldwide. SARS-CoV-2 variants of concern/variants of interest (VOC/VOI) have evidence of increased viral transmission, disease severity, or decreased effectiveness of vaccines and neutralizing antibodies. Remdesivir (RDV [VEKLURY]) is a nucleoside analog prodrug and the first FDA-approved antiviral treatment of COVID-19. Here, we present a comprehensive antiviral activity assessment of RDV and its parent nucleoside, GS-441524, against 10 current and former SARS-CoV-2 VOC/VOI clinical isolates by nucleoprotein enzyme-linked immunosorbent assay (ELISA) and plaque reduction assay. Delta and Omicron variants remained susceptible to RDV and GS-441524, with 50% effective concentration (EC50) values 0.30- to 0.62-fold of those observed against the ancestral WA1 isolate. All other tested variants exhibited EC50 values ranging from 0.13- to 2.3-fold of the observed EC50 values against WA1. Analysis of nearly 6 million publicly available variant isolate sequences confirmed that Nsp12, the RNA-dependent RNA polymerase (RdRp) target of RDV and GS-441524, is highly conserved across variants, with only 2 prevalent changes (P323L and G671S). Using recombinant viruses, both RDV and GS-441524 retained potency against all viruses containing frequent variant substitutions or their combination. Taken together, these results highlight the conserved nature of SARS-CoV-2 Nsp12 and provide evidence of sustained SARS-CoV-2 antiviral activity of RDV and GS-441524 across the tested variants. The observed pan-variant activity of RDV supports its continued use for the treatment of COVID-19 regardless of the SARS-CoV-2 variant.

Safety and efficacy of sofosbuvir-velpatasvir-voxilaprevir for re-treatment of chronic hepatitis C virus infection in patients with previous direct-acting antiviral treatment failure in Rwanda (SHARED-3): a single-arm trial.

BACKGROUND: Hepatitis C virus (HCV) genotype 4 non-a/d subtypes, which frequently have NS5A resistance-associated substitutions, are highly prevalent in sub-Saharan Africa. These subtypes, particularly genotype 4r, have been associated with higher rates of failure of treatment regimens containing the NS5A inhibitors ledipasvir or daclatasvir, which are the most accessible direct-acting antivirals in low-income countries. Clinical evidence regarding the efficacy of re-treatment options for these subtypes is limited. We aimed to evaluate the safety and efficacy of sofosbuvir-velpatasvir-voxilaprevir for the treatment of adults in Rwanda with chronic HCV infection, predominantly of genotype 4, and a history of direct-acting antiviral treatment failure. METHODS: In this single-arm prospective trial, we enrolled adults (aged ≥18 years) with a HCV RNA titre of at least 1000 IU/mL, and a documented history of direct-acting antiviral failure. Patients were assessed for eligibility at a single study site after referral from hospitals with HCV treatment programmes throughout Rwanda, and participants for whom sofosbuvir-ledipasvir treatment had failed in the previous SHARED trial were also included. Participants with decompensated liver disease or hepatitis B virus co-infection were excluded. Participants were treated once daily with an oral fixed-dose combination tablet containing sofosbuvir (400 mg), velpatasvir (100 mg), and voxilaprevir (100 mg) for 12 weeks. The primary endpoint was the proportion of participants with a sustained virological response 12 weeks after completion of treatment (SVR12) in the intention-to-treat population. Viral sequencing of NS3, NS5A, and NS5B genes was done at baseline in all participants and at end of follow-up (week 24) in participants with treatment failure. The study is registered with ClinicalTrials.gov (NCT03888729) and is completed. FINDINGS: Between Sept 23, 2019, and Jan 10, 2020, 49 individuals were screened and 40 participants were enrolled. 20 (50%) were female, 20 (50%) were male, median age was 63 years (IQR 56-68), and median HCV viral load was 6·2 log10 IU/mL (5·8-6·5) at baseline. The genotype subtypes identified were 4r (18 [45%] participants), 4k (six [15%]), 4b (five [13%]), 4q (four [10%]), 4l (two [5%]), 4a (one [3%]), 4m (one [3%]), and 3h (one [3%]). One (3%) genotype 4 isolate could not be subtyped, and one (3%) isolate was of unknown genotype. All successfully sequenced isolates (33 [83%]) had at least two NS5A resistance-associated substitutions and 25 (63%) had three or more. 39 (98% [95% CI 87-100]) participants had SVR12. Seven (18%) participants had a total of ten grade 3, 4, or 5 adverse events, including three (8%) cases of hypertension, and one (3%) case each of cataract, diabetes, gastrointestinal bleeding, joint pain, low back pain, vaginal cancer, and sudden death. Four of these events were categorised as serious adverse events resulting in hospitalisation. The one sudden death occurred at home from an unknown cause 4 weeks after the completion of treatment. No serious adverse event was determined to be related to the study drug or resulted in treatment discontinuation. INTERPRETATION: A 12 week course of sofosbuvir-velpatasvir-voxilaprevir is safe and efficacious for the re-treatment of individuals infected with HCV genotype 4 non-a/d subtypes with frequent baseline NS5A resistance-associated substitutions, following failure of previous direct-acting antiviral treatment. Improved affordability and access to sofosbuvir-velpatasvir-voxilaprevir in regions with these subtypes is crucial. FUNDING: Gilead Sciences.

Safety and efficacy of sofosbuvir-velpatasvir to treat chronic hepatitis C virus infection in treatment-naive patients in Rwanda (SHARED-3): a single-arm trial.

BACKGROUND: Hepatitis C virus (HCV) genotype 4 is the predominant type of HCV found in sub-Saharan Africa. Various genotype 4 subtypes, such as 4r, frequently have resistance-associated substitutions that can increase rates of treatment failure with common direct-acting antiviral regimens. In-vitro studies suggest that the NS5A inhibitor velpatasvir is effective against viral isolates containing such resistance-associated substitutions, but its clinical efficacy against genotype 4 non-a/d subtypes in sub-Saharan Africa remains to be confirmed. We aimed to evaluate the safety and efficacy of sofosbuvir-velpatasvir among adults chronically infected with HCV and naive to direct-acting antiviral treatment in Rwanda, where genotype 4 non-a/d subtypes predominate. METHODS: In this single-arm prospective trial, we enrolled adults (age ≥18 years) in Rwanda who had chronic HCV infection and a plasma HCV RNA titre of at least 1000 IU/mL. Patients were referred from hospitals with HCV treatment programmes throughout Rwanda and were sequentially enrolled and assessed for eligibility at a single study site. Individuals with decompensated liver disease or hepatitis B virus co-infection were excluded. Participants were given an oral fixed-dose combination tablet of sofosbuvir (400 mg) and velpatasvir (100 mg) once-daily for 12 weeks. The primary endpoint was the proportion of participants with a sustained virological response 12 weeks after completion of treatment (SVR12) in the intention-to-treat population. Viral sequencing of the NS5A and NS5B genes was done at baseline for all participants and end of follow-up (week 24) for participants who did not have SVR12. This study is registered with ClinicalTrials.gov (NCT03888729) and is completed. FINDINGS: Between Sept 23, 2019, and Jan 10, 2020, 73 individuals were screened for eligibility, of whom 12 (16%) were excluded and 61 (84%) were enrolled. 40 (66%) participants were female, 21 (34%) were male, median age was 64 years (IQR 51-74), and median baseline HCV viral load was 5·7 log10 IU/mL (5·2-6·2). The genotypes identified among the participants were 4k (28 [46%] participants), 4r (11 [18%]), 4v (eight [13%]), 4q (five [8%]), 4l (three [5%]), 4b (one [2%]), 4c (one [2%]), and one undetermined genotype 4 subtype. Three isolates could not be sequenced and were of indeterminate genotype. Of the 55 HCV isolates that were successfully sequenced, all had at least two NS5A resistance-associated substitutions. 59 (97% [95% CI 89-99]) participants had SVR12. 18 (30%) participants had grade 3 adverse events (including 12 [20%] with hypertension), and none had grade 4 adverse events. Four (7%) participants had serious adverse events, including one asthma exacerbation, one abscess, one uterine myoma, and one pelvic fracture related to a motor vehicle accident. No serious adverse events were attributed to the study drug and no adverse event resulted in discontinuation of the study drug. INTERPRETATION: A 12-week regimen of sofosbuvir-velpatasvir is safe and efficacious in treating chronic HCV genotype 4 infection in patients in Rwanda. This regimen could be an effective treatment option in regions known to have a high prevalence of HCV genotype 4 of diverse non-a/d subtypes. FUNDING: Gilead Sciences.

Early Remdesivir to Prevent Progression to Severe Covid-19 in Outpatients.

BACKGROUND: Remdesivir improves clinical outcomes in patients hospitalized with moderate-to-severe coronavirus disease 2019 (Covid-19). Whether the use of remdesivir in symptomatic, nonhospitalized patients with Covid-19 who are at high risk for disease progression prevents hospitalization is uncertain. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving nonhospitalized patients with Covid-19 who had symptom onset within the previous 7 days and who had at least one risk factor for disease progression (age ≥60 years, obesity, or certain coexisting medical conditions). Patients were randomly assigned to receive intravenous remdesivir (200 mg on day 1 and 100 mg on days 2 and 3) or placebo. The primary efficacy end point was a composite of Covid-19-related hospitalization or death from any cause by day 28. The primary safety end point was any adverse event. A secondary end point was a composite of a Covid-19-related medically attended visit or death from any cause by day 28. RESULTS: A total of 562 patients who underwent randomization and received at least one dose of remdesivir or placebo were included in the analyses: 279 patients in the remdesivir group and 283 in the placebo group. The mean age was 50 years, 47.9% of the patients were women, and 41.8% were Hispanic or Latinx. The most common coexisting conditions were diabetes mellitus (61.6%), obesity (55.2%), and hypertension (47.7%). Covid-19-related hospitalization or death from any cause occurred in 2 patients (0.7%) in the remdesivir group and in 15 (5.3%) in the placebo group (hazard ratio, 0.13; 95% confidence interval [CI], 0.03 to 0.59; P = 0.008). A total of 4 of 246 patients (1.6%) in the remdesivir group and 21 of 252 (8.3%) in the placebo group had a Covid-19-related medically attended visit by day 28 (hazard ratio, 0.19; 95% CI, 0.07 to 0.56). No patients had died by day 28. Adverse events occurred in 42.3% of the patients in the remdesivir group and in 46.3% of those in the placebo group. CONCLUSIONS: Among nonhospitalized patients who were at high risk for Covid-19 progression, a 3-day course of remdesivir had an acceptable safety profile and resulted in an 87% lower risk of hospitalization or death than placebo. (Funded by Gilead Sciences; PINETREE ClinicalTrials.gov number, NCT04501952; EudraCT number, 2020-003510-12.).

SMYD2-Mediated Histone Methylation Contributes to HIV-1 Latency.

Transcriptional latency of HIV is a last barrier to viral eradication. Chromatin-remodeling complexes and post-translational histone modifications likely play key roles in HIV-1 reactivation, but the underlying mechanisms are incompletely understood. We performed an RNAi-based screen of human lysine methyltransferases and identified the SET and MYND domain-containing protein 2 (SMYD2) as an enzyme that regulates HIV-1 latency. Knockdown of SMYD2 or its pharmacological inhibition reactivated latent HIV-1 in T cell lines and in primary CD4+ T cells. SMYD2 associated with latent HIV-1 promoter chromatin, which was enriched in monomethylated lysine 20 at histone H4 (H4K20me1), a mark lost in cells lacking SMYD2. Further, we find that lethal 3 malignant brain tumor 1 (L3MBTL1), a reader protein with chromatin-compacting properties that recognizes H4K20me1, was recruited to the latent HIV-1 promoter in a SMYD2-dependent manner. We propose that a SMYD2-H4K20me1-L3MBTL1 axis contributes to HIV-1 latency and can be targeted with small-molecule SMYD2 inhibitors.

The hepatitis C virus core protein inhibits adipose triglyceride lipase (ATGL)-mediated lipid mobilization and enhances the ATGL interaction with comparative gene identification 58 (CGI-58) and lipid droplets.

Liver steatosis is a common health problem associated with hepatitis C virus (HCV) and an important risk factor for the development of liver fibrosis and cancer. Steatosis is caused by triglycerides (TG) accumulating in lipid droplets (LDs), cellular organelles composed of neutral lipids surrounded by a monolayer of phospholipids. The HCV nucleocapsid core localizes to the surface of LDs and induces steatosis in cultured cells and mouse livers by decreasing intracellular TG degradation (lipolysis). Here we report that core at the surface of LDs interferes with the activity of adipose triglyceride lipase (ATGL), the key lipolytic enzyme in the first step of TG breakdown. Expressing core in livers or mouse embryonic fibroblasts of ATGL(-/-) mice no longer decreases TG degradation as observed in LDs from wild-type mice, supporting the model that core reduces lipolysis by engaging ATGL. Core must localize at LDs to inhibit lipolysis, as ex vivo TG hydrolysis is impaired in purified LDs coated with core but not when free core is added to LDs. Coimmunoprecipitation experiments revealed that core does not directly interact with the ATGL complex but, unexpectedly, increased the interaction between ATGL and its activator CGI-58 as well as the recruitment of both proteins to LDs. These data link the anti-lipolytic activity of the HCV core protein with altered ATGL binding to CGI-58 and the enhanced association of both proteins with LDs.

Lipid droplet-binding protein TIP47 regulates hepatitis C Virus RNA replication through interaction with the viral NS5A protein.

The nonstructural protein NS5A has emerged as a new drug target in antiviral therapies for Hepatitis C Virus (HCV) infection. NS5A is critically involved in viral RNA replication that takes place at newly formed membranes within the endoplasmic reticulum (membranous web) and assists viral assembly in the close vicinity of lipid droplets (LDs). To identify host proteins that interact with NS5A, we performed a yeast two-hybrid screen with the N-terminus of NS5A (amino acids 1-31), a well-studied α-helical domain important for the membrane tethering of NS5A. Our studies identified the LD-associated host protein, Tail-Interacting Protein 47 (TIP47) as a novel NS5A interaction partner. Coimmunoprecipitation experiments in Huh7 hepatoma cells confirmed the interaction of TIP47 with full-length NS5A. shRNA-mediated knockdown of TIP47 caused a more than 10-fold decrease in the propagation of full-length infectious HCV in Huh7.5 hepatoma cells. A similar reduction was observed when TIP47 was knocked down in cells harboring an autonomously replicating HCV RNA (subgenomic replicon), indicating that TIP47 is required for efficient HCV RNA replication. A single point mutation (W9A) in NS5A that disrupts the interaction with TIP47 but preserves proper subcellular localization severely decreased HCV RNA replication. In biochemical membrane flotation assays, TIP47 cofractionated with HCV NS3, NS5A, NS5B proteins, and viral RNA, and together with nonstructural viral proteins was uniquely distributed to lower-density LD-rich membrane fractions in cells actively replicating HCV RNA. Collectively, our data support a model where TIP47--via its interaction with NS5A--serves as a novel cofactor for HCV infection possibly by integrating LD membranes into the membranous web.

Endosomal trafficking of HIV-1 gag and genomic RNAs regulates viral egress.

HIV-1 Gag can assemble and generate virions at the plasma membrane, but it is also present in endosomes where its role remains incompletely characterized. Here, we show that HIV-1 RNAs and Gag are transported on endosomal vesicles positive for TiVamp, a v-SNARE involved in fusion events with the plasma membrane. Inhibition of endosomal traffic did not prevent viral release. However, inhibiting lysosomal degradation induced an accumulation of Gag in endosomes and increased viral production 7-fold, indicating that transport of Gag to lysosomes negatively regulates budding. This also suggested that endosomal Gag-RNA complexes could access retrograde pathways to the cell surface and indeed, depleting cells of TiVamp-reduced viral production. Moreover, inhibition of endosomal transport prevented the accumulation of Gag at sites of cellular contact. HIV-1 Gag could thus generate virions using two pathways, either directly from the plasma membrane or through an endosome-dependent route. Endosomal Gag-RNA complexes may be delivered at specific sites to facilitate cell-to-cell viral transmission.

The clathrin adaptor complex AP-1 binds HIV-1 and MLV Gag and facilitates their budding.

Retroviral assembly is driven by Gag, and nascent viral particles escape cells by recruiting the machinery that forms intralumenal vesicles of multivesicular bodies. In this study, we show that the clathrin adaptor complex AP-1 is involved in retroviral release. The absence of AP-1mu obtained by genetic knock-out or by RNA interference reduces budding of murine leukemia virus (MLV) and HIV-1, leading to a delay of viral propagation in cell culture. In contrast, overexpression of AP-1mu enhances release of HIV-1 Gag. We show that the AP-1 complex facilitates retroviral budding through a direct interaction between the matrix and AP-1mu. Less MLV Gag is found associated with late endosomes in cells lacking AP-1, and our results suggest that AP-1 and AP-3 could function on the same pathway that leads to Gag release. In addition, we find that AP-1 interacts with Tsg101 and Nedd4.1, two cellular proteins known to be involved in HIV-1 and MLV budding. We propose that AP-1 promotes Gag release by transporting it to intracellular sites of active budding, and/or by facilitating its interactions with other cellular partners.

Tail-interacting protein TIP47 is a connector between Gag and Env and is required for Env incorporation into HIV-1 virions.

The presence of the envelope glycoprotein Env in HIV-1 virions is essential for infectivity. To date, the molecular mechanism by which Env is packaged into virions has been largely unknown. Here, we show that TIP47 (tail-interacting protein of 47 kDa), which has been shown to interact with Env, also binds the MA (matrix) domain of HIV-1 Gag protein and that these three proteins form a ternary complex. Mutations in Gag that abrogate interaction with TIP47 inhibit Env incorporation and virion infectivity as well as colocalization between Gag and Env. We also show that TIP47 silencing impairs Env incorporation and infectivity and abolishes coimmunoprecipitation of Gag with Env. In contrast, overexpression of TIP47 increases Env packaging. Last, we demonstrate that TIP47 can interact simultaneously with Env and Gag. Taken together, our results show that TIP47 is a cellular cofactor that plays an essential role in Env incorporation, allowing the encounter and the physical association between HIV-1 Gag and Env proteins during the viral assembly process.