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We observed differential infectivity and product yield between two recombinant chimpanzee adenovirus C68 constructs whose primary difference was genome length. To determine a possible reason for this outcome, we characterized the proportion and composition of the empty and packaged capsids. Both analytical ultracentrifugation (AUC) and differential centrifugation sedimentation (DCS, a rapid and quantitative method for measuring adenoviral packaging variants) were employed for an initial assessment of genome packaging and showed multiple species whose abundance deviated between the virus builds but not manufacturing campaigns. Identity of the packaging variants was confirmed by charge detection mass spectrometry (CDMS), the first known application of this technique to analyze adenovirus. The empty and packaged capsid populations were separated via preparative ultracentrifugation and then combined into a series of mixtures. These mixtures showed the oft-utilized denaturing A260 adenoviral particle titer method will underestimate the actual particle titer by as much as three-fold depending on the empty/full ratio. In contrast, liquid chromatography with fluorescence detection proves to be a superior viral particle titer methodology.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent of Coronavirus Disease 2019 (COVID-19). There is a dire need for novel effective antivirals to treat COVID-19, as the only approved direct-acting antiviral to date is remdesivir, targeting the viral polymerase complex. A potential alternate target in the viral life cycle is the main SARS-CoV-2 protease 3CLpro (Mpro). The drug candidate PF-00835231 is the active compound of the first anti-3CLpro regimen in clinical trials. Here, we perform a comparative analysis of PF-00835231, the pre-clinical 3CLpro inhibitor GC-376, and the polymerase inhibitor remdesivir, in alveolar basal epithelial cells modified to express ACE2 (A549+ACE2 cells). We find PF-00835231 with at least similar or higher potency than remdesivir or GC-376. A time-of-drug-addition approach delineates the timing of early SARS-CoV-2 life cycle steps in A549+ACE2 cells and validates PF-00835231's early time of action. In a model of the human polarized airway epithelium, both PF-00835231 and remdesivir potently inhibit SARS-CoV-2 at low micromolar concentrations. Finally, we show that the efflux transporter P-glycoprotein, which was previously suggested to diminish PF-00835231's efficacy based on experiments in monkey kidney Vero E6 cells, does not negatively impact PF-00835231 efficacy in either A549+ACE2 cells or human polarized airway epithelial cultures. Thus, our study provides in vitro evidence for the potential of PF-00835231 as an effective SARS-CoV-2 antiviral and addresses concerns that emerged based on prior studies in non-human in vitro models.Importance:The arsenal of SARS-CoV-2 specific antiviral drugs is extremely limited. Only one direct-acting antiviral drug is currently approved, the viral polymerase inhibitor remdesivir, and it has limited efficacy. Thus, there is a substantial need to develop additional antiviral compounds with minimal side effects and alternate viral targets. One such alternate target is its main protease, 3CLpro (Mpro), an essential component of the SARS-CoV-2 life cycle processing the viral polyprotein into the components of the viral polymerase complex. In this study, we characterize a novel antiviral drug, PF-00835231, which is the active component of the first-in-class 3CLpro-targeting regimen in clinical trials. Using 3D in vitro models of the human airway epithelium, we demonstrate the antiviral potential of PF-00835231 for inhibition of SARS-CoV-2.

COVID-19 caused by the SARS-CoV-2 virus has become a global pandemic. 3CL protease is a virally encoded protein that is essential across a broad spectrum of coronaviruses with no close human analogs. PF-00835231, a 3CL protease inhibitor, has exhibited potent in vitro antiviral activity against SARS-CoV-2 as a single agent. Here we report, the design and characterization of a phosphate prodrug PF-07304814 to enable the delivery and projected sustained systemic exposure in human of PF-00835231 to inhibit coronavirus family 3CL protease activity with selectivity over human host protease targets. Furthermore, we show that PF-00835231 has additive/synergistic activity in combination with remdesivir. We present the ADME, safety, in vitro, and in vivo antiviral activity data that supports the clinical evaluation of PF-07304814 as a potential COVID-19 treatment.

COVID-19 caused by the SARS-CoV-2 virus has become a global pandemic. 3CL protease is a virally encoded protein that is essential across a broad spectrum of coronaviruses with no close human analogs. PF-00835231, a 3CL protease inhibitor, has exhibited potent in vitro antiviral activity against SARS-CoV-2 as a single agent. Here we report, the design and characterization of a phosphate prodrug PF-07304814 to enable the delivery and projected sustained systemic exposure in human of PF-00835231 to inhibit coronavirus family 3CL protease activity with selectivity over human host protease targets. Furthermore, we show that PF-00835231 has additive/synergistic activity in combination with remdesivir. We present the ADME, safety, in vitro, and in vivo antiviral activity data that supports the clinical evaluation of PF-07304814 as a potential COVID-19 treatment., The 3CL protease of SARS-CoV-2 is inhibited by PF-00835231 in vitro. Here, the authors show that the prodrug PF-07304814 has broad spectrum activity, inhibiting SARS-CoV and SARS-CoV-2 in mice and its ADME and safety profile support clinical development.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent of Coronavirus Disease 2019 (COVID-19). There is a dire need for novel effective antivirals to treat COVID-19, as the only approved direct-acting antiviral to date is remdesivir, targeting the viral polymerase complex. A potential alternate target in the viral life cycle is the main SARS-CoV-2 protease 3CLpro(Mpro). The drug candidate PF-00835231 is the active compound of the first anti-3CLproregimen in clinical trials. Here, we perform a comparative analysis of PF-00835231, the pre-clinical 3CLproinhibitor GC-376, and the polymerase inhibitor remdesivir, in alveolar basal epithelial cells modified to express ACE2 (A549+ACE2cells). We find PF-00835231 with at least similar or higher potency than remdesivir or GC-376. A time-of-drug-addition approach delineates the timing of early SARS-CoV-2 life cycle steps in A549+ACE2cells and validates PF-00835231’s early time of action. In a model of the human polarized airway epithelium, both PF-00835231 and remdesivir potently inhibit SARS-CoV-2 at low micromolar concentrations. Finally, we show that the efflux transporter P-glycoprotein, which was previously suggested to diminish PF-00835231’s efficacy based on experiments in monkey kidney Vero E6 cells, does not negatively impact PF-00835231 efficacy in either A549+ACE2cells or human polarized airway epithelial cultures. Thus, our study providesin vitroevidence for the potential of PF-00835231 as an effective SARS-CoV-2 antiviral and addresses concerns that emerged based on prior studies in non-humanin vitromodels.ImportanceThe arsenal of SARS-CoV-2 specific antiviral drugs is extremely limited. Only one direct-acting antiviral drug is currently approved, the viral polymerase inhibitor remdesivir, and it has limited efficacy. Thus, there is a substantial need to develop additional antiviral compounds with minimal side effects and alternate viral targets. One such alternate target is its main protease, 3CLpro(Mpro), an essential component of the SARS-CoV-2 life cycle processing the viral polyprotein into the components of the viral polymerase complex. In this study, we characterize a novel antiviral drug, PF-00835231, which is the active component of the first-in-class 3CLpro-targeting regimen in clinical trials. Using 3Din vitromodels of the human airway epithelium, we demonstrate the antiviral potential of PF-00835231 for inhibition of SARS-CoV-2.

2612 Background: Therapeutic vaccines targeting PC-associated antigens represent attractive approaches in combination with immune checkpoint inhibitors (ICI). Safety/antitumor activity of PF-06753512 (PrCa VBIR) was evaluated in a phase I, dose-escalation and expansion study in patients (pts) with BCR prior to ADT and in pts with mCRPC either prior to or after failure of novel hormone therapy. PrCa VBIR consists of: 1) priming immunization with a replication-deficient adenoviral vector (AdC68) expressing PSA, prostate-specific membrane antigen and prostate stem cell antigen; 2) boosts with plasmid DNA (pDNA) encoding the same antigens by IM electroporation; 3) ICI given subcutaneously, including anti CTLA-4 antibody tremelimumab (TRM) and anti PD-1 antibody sasanlimab (SSL). Methods: AdC68 ± ICI(s) were given on months (mos) 1 and 5 and pDNA ± ICI(s) on mos 2–4 and 6–8. After 8 mos, maintenance pDNA + ICI(s) were given every 1 or 2 mos. In Part A (6 escalation cohorts), pts with mCRPC received AdC68 (4 or 6x10e11 viral particles) + pDNA 5 mg ± ICIs (TRM alone 80 mg; TRM 40 or 80 mg + SSL 130 or 300 mg). In Part B (3 expansion cohorts), pts with mCRPC received AdC68 6x10e11 + pDNA 5 mg + TRM 80 mg + SSL 300 mg; pts with BCR received similar vector and pDNA + TRM 80 mg ± SSL 130 mg. Primary objectives: Assess overall safety (CTCAE v4.03), determine expansion dose. Secondary objectives: Anti-tumor activity (RECIST v1.1, Prostate Cancer Working Group 3, PSA 50 response) and immune response. (Note: Database remains open, some queries pending). Results: As of Sept 15, 2020, 91 pts were treated in dose-escalation (n=38) and expansion (n=53; BCR=35, mCRPC=18). Immune responses (ELISpot) were positive in some pts. Grade (G) 3 or 4 treatment-related adverse events (TRAEs) developed in 38.5% (35/91) of pts. G5 TRAEs occurred in 2 pts (n=1 G4 myasthenia gravis + G5 pulmonary embolism; n=1 G5 myocarditis). irAEs were more frequent in BCR compared to mCRPC. See the table for efficacy data. Conclusions: Vaccination with PrCa VBIR had a manageable safety profile. TRAEs increased when 2 ICIs were given. Some pts with BCR experienced durable PSA-50 responses without ADT; patients with mCRPC had few objective tumor responses, but had prolonged median rPFS. PrCa VBIR appears to stimulate antigen-specific immunity and results in noticeable antitumor activity, particularly in androgen sensitive disease. Clinical trial information: NCT02616185. [Table: see text]

Several potent inhibitors of hepatitis C virus (HCV) NS3/4A protease have been identified that show great clinical potential against genotype 1. Due to the tremendous genetic diversity that exists among HCV isolates, development of broad spectrum inhibitors is challenging. With a limited number of lab strains available for preclinical testing, new tools are required for assessing protease inhibitor activity. We developed a chimeric replicon system for evaluating NS3 protease inhibitor activity against naturally occurring isolates. NS3/4A genes were cloned from the plasma of HCV-infected individuals and inserted into lab strain replicons, replacing the native sequences. The chimeric reporter replicons were transfected into Huh 7.5 cells, their replication monitored by luciferase assays, and their susceptibilities to inhibitors determined. Viable chimeras expressing heterologous genotypes 1, 2, 3, and 4 protease domains were identified that exhibited varying susceptibilities to inhibitors. Protease inhibitor spectrums observed against the chimeric replicon panel strongly correlated with published enzymatic and clinical results. This cell-based chimeric replicon system can be used to characterize the activities of protease inhibitors against diverse natural isolates and may improve the ability to predict dose and clinical efficacy.