RT Journal Article SR Electronic T1 A small molecule oxocarbazate inhibitor of human cathepsin L blocks SARS and Ebola pseudotype virus infection into HEK 293T cells JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP mol.110.064261 DO 10.1124/mol.110.064261 A1 Parag P Shah A1 Tianhua Wang A1 , Rachel L Kaletsky A1 Michael Myers A1 Jeremy E Puvis A1 Huiyan Jing A1 Donna M Huryn A1 Doron C Greenbaum A1 Amos B Smith A1 Paul Bates A1 Scott L Diamond YR 2010 UL http://molpharm.aspetjournals.org/content/early/2010/05/13/mol.110.064261.abstract AB A tetrahydroquinoline oxocarbazate (PubChem CID 23631927) was tested as an inhibitor of human cathepsin L (EC 3.4.22.15) and as an entry blocker of SARS coronavirus and Ebola pseudotype virus. In the cathepsin L inhibition assay, the oxocarbazate caused a time-dependent 17-fold drop in IC50 from 6.9 nM (no pre-incubation) to 0.4 nM (4 hr pre-incubation). Slowly reversible inhibition was demonstrated in a dilution assay. A transient kinetic analysis using a single step, competitive inhibition model provided rate constants of kon = 153,000 M-1s-1 and koff = 4.40 x 10-5 s-1 (Ki = 0.29 nM). The compound also displayed cathepsin L/B selectivity of > 700-fold and was nontoxic to human aortic endothelial cells at 100 μM. The oxocarbazate and a related thiocarbazate (CID 16725315) were tested in a SARS-CoV and Ebola virus-pseudotype infection assay with the oxocarbozate, but not the thiocarbazate, demonstrating activity in blocking both SARS-CoV (IC50 = 273±49 nM) and Ebola virus (IC50 = 193±39 nM) entry into HEK 293T cells. In order to trace the intracellular action of the inhibitors with intracellular cathepsin L, the activity based probe DCG-04 was used to label the active site of cysteine proteases in 293T lysates. The reduction in active cathepsin L in inhibitor treated cells correlated well with the observed potency of inhibitors observed in the virus pseudotype infection assay. Overall, the oxocarbazate CID 23631927 was a sub-nanomolar slow-binding, reversible inhibitor of human cathepsin L that blocked SARS-CoV and Ebola pseudotype virus entry in human cells.The American Society for Pharmacology and Experimental Therapeutics