A comparative analysis of SARS-CoV-2 antivirals characterizes 3CLpro inhibitor PF-00835231 as a potential new treatment for COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for Coronavirus Disease 2019 (COVID-19). There is an urgent need for new effective antiviral treatments, as the only approved direct-acting antiviral so far is remdesivir, which targets the viral polymerase complex. A promising alternative target in the viral lifecycle is the main protease, 3CLpro (Mpro). PF-00835231 is the active compound in the first anti-3CLpro regimen currently in clinical trials.

In this study, we compare the efficacy of PF-00835231 with the preclinical 3CLpro inhibitor GC-376 and the polymerase inhibitor remdesivir in alveolar basal epithelial cells engineered to express ACE2 (A549+ACE2 cells). Our results indicate that PF-00835231 exhibits similar or greater potency than both remdesivir and GC-376. A time-of-drug-addition analysis helps clarify the timing of early steps in the SARS-CoV-2 lifecycle within A549+ACE2 cells, confirming that PF-00835231 acts early in the process.

In a model of human polarized airway epithelium, both PF-00835231 and remdesivir effectively inhibit SARS-CoV-2 at low micromolar concentrations. Furthermore, we demonstrate that the efflux transporter P-glycoprotein, previously thought to reduce the efficacy of PF-00835231 in monkey kidney Vero E6 cells, does not affect its effectiveness in A549+ACE2 cells or human airway epithelial cultures. This study provides in vitro evidence supporting the potential of PF-00835231 as a viable antiviral against SARS-CoV-2, addressing concerns raised by earlier non-human studies.

Importance: The options for SARS-CoV-2-specific antiviral drugs are extremely limited, with only remdesivir currently approved, and its effectiveness is constrained. There is a significant need for additional antiviral compounds with minimal side effects that target different viral mechanisms. One such target is the main protease, 3CLpro (Mpro), which plays a crucial role in processing the viral polyprotein necessary for the viral polymerase complex. This study characterizes PF-00835231, a novel antiviral drug that is part of the first 3CLpro-targeting regimen in clinical trials, demonstrating its potential in inhibiting SARS-CoV-2 using 3D in vitro models of the human airway epithelium.