Preclinical characterization of a non-peptidomimetic HIV protease inhibitor with improved metabolic stability

Protease inhibitors (PIs) remain an important component of antiretroviral therapy for the treatment of HIV-1 infection due to their high genetic barrier to resistance development. Nevertheless, the two most commonly prescribed HIV PIs, atazanavir and darunavir, still require co-administration with a pharmacokinetic boosting agent to maintain sufficient drug plasma levels which can lead to undesirable drug-drug interactions. Herein, we describe GS-9770, a novel investigational non-peptidomimetic HIV PI with unboosted once-daily oral dosing potential due to improvements in its metabolic stability and its pharmacokinetic properties in preclinical animal species. This compound demonstrates potent inhibitory activity and high on-target selectivity for recombinant HIV-1 protease versus other aspartic proteases tested. In cell culture, GS-9770 inhibits Gag polyprotein cleavage and shows nanomolar anti-HIV-1 potency in primary human cells permissive to HIV-1 infection and against a broad range of HIV subtypes. GS-9770 demonstrates an improved resistance profile against a panel of patient-derived HIV-1 isolates with resistance to atazanavir and darunavir. In resistance selection experiments, GS-9770 prevented the emergence of breakthrough HIV-1 variants at all fixed drug concentrations tested and required multiple protease substitutions to enable outgrowth of virus exposed to escalating concentrations of GS-9770. This compound also remained fully active against viruses resistant to drugs from other antiviral classes and showed no in vitro antagonism when combined pairwise with drugs from other antiretroviral classes. Collectively, these preclinical data identify GS-9770 as a potent, non-peptidomimetic once-daily oral HIV PI with potential to overcome the persistent requirement for pharmacological boosting with this class of antiretroviral agents.

The Natural Stilbenoid (-)-Hopeaphenol Inhibits HIV Transcription by Targeting Both PKC and NF-κB Signaling and Cyclin-Dependent Kinase 9

Despite effective combination antiretroviral therapy (cART), people living with HIV (PLWH) continue to harbor replication-competent and transcriptionally active virus in infected cells, which in turn can lead to ongoing viral antigen production, chronic inflammation, and increased risk of age-related comorbidities. To identify new agents that may inhibit postintegration HIV beyond cART, we screened a library of 512 pure compounds derived from natural products and identified (-)-hopeaphenol as an inhibitor of HIV postintegration transcription at low to submicromolar concentrations without cytotoxicity. Using a combination of global RNA sequencing, plasmid-based reporter assays, and enzyme activity studies, we document that hopeaphenol inhibits protein kinase C (PKC)- and downstream NF-κB-dependent HIV transcription as well as a subset of PKC-dependent T-cell activation markers, including interleukin-2 (IL-2) cytokine and CD25 and HLA-DRB1 RNA production. In contrast, it does not substantially inhibit the early PKC-mediated T-cell activation marker CD69 production of IL-6 or NF-κB signaling induced by tumor necrosis factor alpha (TNF-α). We further show that hopeaphenol can inhibit cyclin-dependent kinase 9 (CDK9) enzymatic activity required for HIV transcription. Finally, it inhibits HIV replication in peripheral blood mononuclear cells (PBMCs) infected in vitro and dampens viral reactivation in CD4⁺ cells from PLWH. Our study identifies hopeaphenol as a novel inhibitor that targets a subset of PKC-mediated T-cell activation pathways in addition to CDK9 to block HIV expression. Hopeaphenol-based therapies could complement current antiretroviral therapy otherwise not targeting cell-associated HIV RNA and residual antigen production in PLWH.

Safety, Tolerability, and Pharmacokinetics of Anti-SARS-CoV-2 Immunoglobulin Intravenous (Human) Investigational Product (COVID-HIGIV) in Healthy Adults: a Randomized, Controlled, Double-Blinded, Phase 1 Study

Anti-SARS-CoV-2 immunoglobulin (human) investigational product (COVID-HIGIV) is a purified immunoglobulin preparation containing SARS-CoV-2 polyclonal antibodies. This single-center clinical trial aimed to characterize the safety and pharmacokinetics of COVID-HIGIV in healthy, adult volunteers. Participants were enrolled to receive one of three doses of COVID-HIGIV (100, 200, 400 mg/kg) or placebo in a 2:2:2:1 randomization scheme. Between 24 December 2020 and 27 July 2021, 28 participants met eligibility and were randomized with 27 of these 28 (96.4%) being administered either COVID-HIGIV (n = 23) or placebo (n = 4). Only one SAE was observed, and it occurred in the placebo group. A total of 18 out of 27 participants (66.7%) reported 50 adverse events (AEs) overall. All COVID-HIGIV-related adverse events were mild or moderate in severity and transient. The most frequent AEs (>5% of participants) reported in the safety population were headache (n = 6, 22.2%), chills (n = 3, 11.1%), increased bilirubin (n = 2, 7.4%), muscle spasms (n = 2, 7.4%), seasonal allergies (n = 2, 7.4%), pyrexia (n = 2, 7.4%), and oropharyngeal pain (n = 2, 7.4%). Using the SARS-CoV-2 binding IgG immunoassay (n = 22, specific for pharmacokinetics), the geometric means of Cmax (AU/mL) for the three COVID-HIGIV dose levels (low to high) were 7.69, 17.02, and 33.27 AU/mL; the average values of T_max were 7.09, 7.93, and 5.36 h, respectively. The half-life of COVID-HIGIV per dose level was 24 d (583 h), 31 d (753 h), and 26 d (619 h) for the 100 mg/kg, 200 mg/kg, and 400 mg/kg groups, respectively. The safety and pharmacokinetics of COVID-HIGIV support its development as a single-dose regimen for postexposure prophylaxis or treatment of COVID-19.

Semi-Mechanistic Pharmacokinetic-Pharmacodynamic Model of Camostat Mesylate-Predicted Efficacy against SARS-CoV-2 in COVID-19

The SARS-CoV-2 coronavirus, which causes COVID-19, uses a viral surface spike protein for host cell entry and the human cell-surface transmembrane serine protease, TMPRSS2, to process the spike protein. Camostat mesylate, an orally available and clinically used serine protease inhibitor, inhibits TMPRSS2, supporting clinical trials to investigate its use in COVID-19. A one-compartment pharmacokinetic (PK)/pharmacodynamic (PD) model for camostat and the active metabolite FOY-251 was developed, incorporating TMPRSS2 reversible covalent inhibition by FOY-251, and empirical equations linking TMPRSS2 inhibition of SARS-CoV-2 cell entry. The model predicts that 95% inhibition of TMPRSS2 is required for 50% inhibition of viral entry efficiency. For camostat 200 mg dosed four times daily, 90% inhibition of TMPRSS2 is predicted to occur but with only about 40% viral entry inhibition. For 3-fold higher camostat dosing, marginal improvement of viral entry rate inhibition, up to 54%, is predicted. Because respiratory tract viral load may be associated with negative outcome, even modestly reducing viral entry and respiratory tract viral load may reduce disease progression. This modeling also supports medicinal chemistry approaches to enhancing PK/PD and potency of the camostat molecule. IMPORTANCE Strategies to repurpose already-approved drugs for the treatment of COVID-19 has been attractive since the beginning of the pandemic. Camostat mesylate, a serine protease inhibitor approved in Japan for the treatment of acute exacerbations of chronic pancreatitis, inhibits TMPRSS1, a host cell surface serine protease essential for SARS-CoV-2 viral entry. In vitro experiments provided data suggesting that camostat might be effective in the treatment of COVID-19. Multiple clinical trials were planned to test the hypothesis that camostat would be beneficial for treating COVID-19 (for example, clinicaltrials.gov, NCT04353284). The present work used a one-compartment pharmacokinetic (PK)/pharmacodynamic (PD) mathematical model for camostat and the active metabolite FOY-251, incorporating TMPRSS2 reversible covalent inhibition by FOY-251, and empirical equations linking TMPRSS2 inhibition of SARS-CoV-2 cell entry. This work is valuable to guide further development of camostat mesylate and possible medicinal chemistry derivatives for the treatment of COVID-19.

A Targeted Computational Screen of the SWEETLEAD Database Reveals FDA-Approved Compounds with Anti-Dengue Viral Activity

Affordable and effective antiviral therapies are needed worldwide, especially against agents such as dengue virus that are endemic in underserved regions. Many antiviral compounds have been studied in cultured cells but are unsuitable for clinical applications due to pharmacokinetic profiles, side effects, or inconsistent efficacy across dengue serotypes. Such tool compounds can, however, aid in identifying clinically useful treatments. Here, computational screening (Rapid Overlay of Chemical Structures) was used to identify entries in an in silico database of safe-in-human compounds (SWEETLEAD) that display high chemical similarities to known inhibitors of dengue virus. Inhibitors of the dengue proteinase NS2B/3, the dengue capsid, and the host autophagy pathway were used as query compounds. Three FDA-approved compounds that resemble the tool molecules structurally, cause little toxicity, and display strong antiviral activity in cultured cells were selected for further analysis. Pyrimethamine (50% inhibitory concentration [IC₅₀] = 1.2 μM), like the dengue proteinase inhibitor ARDP0006 to which it shows structural similarity, inhibited intramolecular NS2B/3 cleavage. Lack of toxicity early in infection allowed testing in mice, in which pyrimethamine also reduced viral loads. Niclosamide (IC₅₀ = 0.28 μM), like dengue core inhibitor ST-148, affected structural components of the virion and inhibited early processes during infection. Vandetanib (IC₅₀ = 1.6 μM), like cellular autophagy inhibitor spautin-1, blocked viral exit from cells and could be shown to extend survival in vivo Thus, three FDA-approved compounds with promising utility for repurposing to treat dengue virus infections and their potential mechanisms were identified using computational tools and minimal phenotypic screening.IMPORTANCE No antiviral therapeutics are currently available for dengue virus infections. By computationally overlaying the three-dimensional (3D) chemical structures of compounds known to inhibit dengue virus over those of compounds known to be safe in humans, we identified three FDA-approved compounds that are attractive candidates for repurposing as antivirals. We identified targets for two previously identified antiviral compounds and revealed a previously unknown potential anti-dengue compound, vandetanib. This computational approach to analyze a highly curated library of structures has the benefits of speed and cost efficiency. It also leverages mechanistic work with query compounds used in biomedical research to provide strong hypotheses for the antiviral mechanisms of the safer hit compounds. This workflow to identify compounds with known safety profiles can be expanded to any biological activity for which a small-molecule query compound has been identified, potentially expediting the translation of basic research to clinical interventions.

Validating Enterovirus D68-2Apro as an Antiviral Drug Target and the Discovery of Telaprevir as a Potent D68-2Apro Inhibitor

Enterovirus D68 (EV-D68) is a viral pathogen that leads to severe respiratory illness and has been linked with the development of acute flaccid myelitis (AFM) in children. No vaccines or antivirals are currently available for EV-D68 infection, and treatment options for hospitalized patients are limited to supportive care. Here, we report the expression of the EV-D68 2A protease (2A^pro) and characterization of its enzymatic activity. Furthermore, we discovered that telaprevir, an FDA-approved drug used for the treatment of hepatitis C virus (HCV) infections, is a potent antiviral against EV-D68 by targeting the 2A^pro enzyme. Using a fluorescence resonance energy transfer-based substrate cleavage assay, we showed that the purified EV-D68 2A^pro has proteolytic activity selective against a peptide sequence corresponding to the viral VP1-2A polyprotein junction. Telaprevir inhibits EV-D68 2A^pro through a nearly irreversible, biphasic binding mechanism. In cell culture, telaprevir showed submicromolar-to-low-micromolar potency against several recently circulating neurotropic strains of EV-D68 in different human cell lines. To further confirm the antiviral drug target, serial viral passage experiments were performed to select for resistance against telaprevir. An N84T mutation near the active site of 2A^pro was identified in resistant viruses, and this mutation reduced the potency of telaprevir in both the enzymatic and cellular antiviral assays. Collectively, we report for the first time the in vitro enzymatic activity of EV-D68 2A^pro and the identification of telaprevir as a potent EV-D68 2A^pro inhibitor. These findings implicate EV-D68 2A^pro as an antiviral drug target and highlight the repurposing potential of telaprevir to treat EV-D68 infection.IMPORTANCE A 2014 EV-D68 outbreak in the United States has been linked to the development of acute flaccid myelitis in children. Unfortunately, no treatment options against EV-D68 are currently available, and the development of effective therapeutics is urgently needed. Here, we characterize and validate a new EV-D68 drug target, the 2A^pro, and identify telaprevir-an FDA-approved drug used to treat hepatitis C virus (HCV) infections-as a potent antiviral with a novel mechanism of action toward 2A^pro 2A^pro functions as a viral protease that cleaves a peptide sequence corresponding to the VP1-2A polyprotein junction. The binding of telaprevir potently inhibits its enzymatic activity, and using drug resistance selection, we show that the potent antiviral activity of telaprevir was due to 2A^pro inhibition. This is the first inhibitor to selectively target the 2A^pro from EV-D68 and can be used as a starting point for the development of therapeutics with selective activity against EV-D68.

Pharmacokinetic Changes during Pregnancy According to Genetic Variants: a Prospective Study in HIV-Infected Patients Receiving Atazanavir-Ritonavir

Atazanavir-ritonavir concentrations change over time during pregnancy in HIV-positive patients; the impact of genetic variants is unknown. Twenty patients were enrolled in this study; plasma and intracellular concentrations of antiretrovirals were measured, in addition to single-nucleotide polymorphisms in transport-related genes. Linear logistic regression showed that genetic variants in organic-anion-transporter-1B1- and pregnane-X-receptor-encoding genes affected third-trimester atazanavir exposure. In this prospective study, genetic variants partially explained the observed interpatient variability in third-trimester exposure to antiretrovirals.