DX-027 for COVID-19

Coronavirus infections, such as the global COVID-19 pandemic, have had a profound impact on many aspects of our daily life including working style, economy, and the healthcare system. To prevent the rapid viral transmission and speed up recovery from the infection, many academic organizations and industry research labs have conducted extensive research on discovering new therapeutic options for SARS-CoV-2. Among those efforts, RNA-dependent RNA polymerase (RdRp) inhibitors such as Remdesivir, Molnupiravir and 3CLpro inhibitor such as Nirmatrelvir (PaxlovidTM) have been widely used as the therapeutic options. Given the recent emergence of several new variants that caused a resurgence of the virus, it would be beneficial to discover more diverse therapeutic options with novel anti-viral mechanisms. In this regard, PLpro has been highlighted since it, along with 3CLpro, is one of the two most important proteases that are required for SARS-CoV-2 viral processing. While 3CLpro inhibitors were extensively investigated in the light of Emergency Use Authorizations of Nirmatrelvir, PLpro inhibitors have not been thoroughly investigated even preclinically. Thus, discovery efforts on antivirals acting against PLpro will be valuable. PLpro inhibitors may exert their activity by inhibiting viral replication and enhancing the host defense system through blocking virus-induced cell signaling events for evading host immune response. In this study, we report the discovery and development of two covalent irreversible PLpro inhibitors, HUP0109 and its deuterated analog DX-027, out of our quest for novel anti-COVID 19 therapeutic agents for the past two and half years. HUP0109 selectively targets the viral catalytic cleft of PLpro and covalently modifies its active site cysteine residue (C111). Promising results from preclinical evaluation suggest that DX-027 can be developed as a potential COVID-19 treatment.