8UH5 image
Entry Detail
PDB ID:
8UH5
Keywords:
Title:
Crystal structure of SARS-CoV-2 main protease in complex with an inhibitor TKB-272
Biological Source:
PDB Version:
Deposition Date:
2023-10-06
Release Date:
2023-12-13
Method Details:
Experimental Method:
Resolution:
1.74 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:3C-like proteinase nsp5
Chain IDs:A
Chain Length:306
Number of Molecules:1
Biological Source:Severe acute respiratory syndrome coronavirus 2
Primary Citation
An orally available P1'-5-fluorinated M pro inhibitor blocks SARS-CoV-2 replication without booster and exhibits high genetic barrier.
Pnas Nexus 4 pgae578 pgae578 (2025)
PMID: 39831159 DOI: 10.1093/pnasnexus/pgae578

Abstact

We identified a 5-fluoro-benzothiazole-containing small molecule, TKB272, through fluorine-scanning of the benzothiazole moiety, which more potently inhibits the enzymatic activity of SARS-CoV-2's main protease (Mpro) and more effectively blocks the infectivity and replication of all SARS-CoV-2 strains examined including Omicron variants such as SARS-CoV-2XBB1.5 and SARS-CoV-2EG.5.1 than two Mpro inhibitors: nirmatrelvir and ensitrelvir. Notably, the administration of ritonavir-boosted nirmatrelvir and ensitrelvir causes drug-drug interactions warranting cautions due to their CYP3A4 inhibition, thereby limiting their clinical utility. When orally administered, TKB272 blocked SARS-CoV-2XBB1.5 replication without ritonavir in B6.Cg-Tg(K18-hACE2)2-Prlmn/J-transgenic mice, comparably as did ritonavir-boosted nirmatrelvir. When the ancestral SARS-CoV-2 was propagated with nirmatrelvir in vitro, a highly nirmatrelvir-resistant E166V-carrying variant (SARS-CoV-2E166V-P14) readily emerged by passage 14; however, when propagated with TKB272, no variants emerged by passage 25. SARS-CoV-2E166V showed some cross-resistance to TKB272 but was substantially sensitive to the compound. X-ray structural analyses and mass-spectrometric data showed that the E166V substitution disrupts the critical dimerization-initiating Ser1'-E166 interactions, thereby limiting nirmatrelvir's Mpro inhibition but that TKB272 nevertheless forms a tight binding with Mpro's catalytic active sight even in the presence of the E166V substitution. TKB272 shows no apparent genotoxicity as tested in the micro-Ames test. Highly potent TKB272 may serve as a COVID-19 therapeutic, overcome resistance to existing Mpro inhibitors.

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