An Update on the Current State of SARS-CoV-2 Mac1 Inhibitors

Abstract

Non-structural protein 3 (nsp3) from all coronaviruses (CoVs) contains a conserved macrodomain, known as Mac1, that has been proposed as a potential therapeutic target for CoVs due to its critical role in viral pathogenesis. Mac1 is an ADP-ribose binding protein and ADP-ribosylhydrolase that promotes replication and blocks IFN responses, though the precise mechanisms it uses to carry out these functions remain unknown. Over the past 3 years following the onset of COVID-19, several groups have used high-throughput screening with multiple assays and chemical modifications to create unique chemical inhibitors of the SARS-CoV-2 Mac1 protein. Here, we summarize the current efforts to identify selective and potent inhibitors of SARS-CoV-2 Mac1.

Discovery of 2-Amide-3-methylester Thiophenes that Target SARS-CoV-2 Mac1 and Repress Coronavirus Replication, Validating Mac1 as an Antiviral Target

“…However, both prepared analogues were inactive, and therefore, we decided to continue at this stage to explore other parts of the molecule. We synthesized a dimethyl ester derivative (23) to remove the ability of 1 to form a negative charge and to maintain the potential to form the hydrogen bonds to the backbone amides as seen in the cocrystal structure of 1. This modification improved the compound potency slightly (IC 50 = 11 μM).…”

“…1 H NMR (400 MHz, DMSO-d 6 ) δ ppm 1.52−1.67 (m, 4H), 1.75−1.87 (m, 2H), 2.29−2.37 (m, 1H), 2.41−2.47 (m, 3H), 2.48 (s, 3H), 2.65−2.76 (m, 2H), 2.79−2.90 (m, 2H), 3.00−3.12 (m, 2H), 5.68 (m, 2H), 11.7 (br s, 1H), 12.28 (br s, 1H). 13 (23). 221.3 mg (0.586 mmol) of compound 1r was dissolved in 23 mL of methanol, and 200 μL of conc H 2 SO 4 was added.…”

“…17,20 The discovered SARS-CoV-2 Mac1 inhibitors have also been recently discussed in reviews. 23,24 The majority of the compounds reached low-mid μM potency, though a few reached sub-μM IC 50 's, and in general, they lacked the properties allowing cell permeability and subsequent validation of SARS-CoV-2 Mac1 as a pharmacological target. Using a recently developed robust protein fluorescence resonance energy transfer (FRET)-based assay, 21,25 we performed high-throughput screening of compounds to identify novel inhibitors of SARS-CoV-2 Mac1.…”

“…Initial compounds targeting virus macrodomains have been described for alphaviruses , and coronaviruses. − These efforts have used both screening of compound libraries, ,, in crystallo fragment screening to discover early small inhibitors, and further development to produce more potent compounds. , The discovered SARS-CoV-2 Mac1 inhibitors have also been recently discussed in reviews. , The majority of the compounds reached low-mid μM potency, though a few reached sub-μM IC 50 ’s, and in general, they lacked the properties allowing cell permeability and subsequent validation of SARS-CoV-2 Mac1 as a pharmacological target.…”

1-L Transcription of SARS-CoV-2 Spike Protein S1 Subunit

“…Nsp3 is a multi-domain, non-structural SARS-CoV-2 protein with a conserved Mac1 domain. It has mono-ADP-ribose (MAR) and PAR hydrolase activity [25] required for IFN antagonism and efficient virus replication [26,27]. ADP ribose is a product of PARG and Nsp3 activities.…”