title: A small-molecule oxocarbazate inhibitor of human cathepsin L blocks severe acute respiratory syndrome and ebola pseudotype virus infection into human embryonic kidney 293T cells.
abstract: 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 severe acute respiratory syndrome (SARS) coronavirus and Ebola pseudotype virus. In the cathepsin L inhibition assay, the oxocarbazate caused a time-dependent 17-fold drop in IC(50) from 6.9 nM (no preincubation) to 0.4 nM (4-h preincubation). Slowly reversible inhibition was demonstrated in a dilution assay. A transient kinetic analysis using a single-step competitive inhibition model provided rate constants of k(on) = 153,000 M(-1)s(-1) and k(off) = 4.40 x 10(-5) s(-1) (K(i) = 0.29 nM). The compound also displayed cathepsin L/B selectivity of >700-fold and was nontoxic to human aortic endothelial cells at 100 muM. The oxocarbazate and a related thiocarbazate (PubChem CID 16725315) were tested in a SARS coronavirus (CoV) and Ebola virus-pseudotype infection assay with the oxocarbazate but not the thiocarbazate, demonstrating activity in blocking both SARS-CoV (IC(50) = 273 +/- 49 nM) and Ebola virus (IC(50) = 193 +/- 39 nM) entry into human embryonic kidney 293T cells. To trace the intracellular action of the inhibitors with intracellular cathepsin L, the activity-based probe biotin-Lys-C5 alkyl linker-Tyr-Leu-epoxide (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 subnanomolar, slow-binding, reversible inhibitor of human cathepsin L that blocked SARS-CoV and Ebola pseudotype virus entry in human cells.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Penn Center for Molecular Discovery, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6383, USA.
authors.forename: Parag P
authors.initials: PP
authors.lastname: Shah
authors.forename: Tianhua
authors.initials: T
authors.lastname: Wang
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Kaletsky
authors.forename: Michael C
authors.initials: MC
authors.lastname: Myers
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Purvis
authors.forename: Huiyan
authors.initials: H
authors.lastname: Jing
authors.forename: Donna M
authors.initials: DM
authors.lastname: Huryn
authors.forename: Doron C
authors.initials: DC
authors.lastname: Greenbaum
authors.forename: Amos B
authors.initials: AB
authors.lastname: Smith
authors.forename: Paul
authors.initials: P
authors.lastname: Bates
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D056668:Cathepsin L / Q000037:antagonists & inhibitors*; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D019142:Hemorrhagic Fever, Ebola / Q000517:prevention & control*; D006801:Humans; D007700:Kinetics; D011804:Quinolines / Q000494:pharmacology*; D015363:Quinolones / Q000494:pharmacology*; D045169:Severe Acute Respiratory Syndrome / Q000517:prevention & control*
chemical_list: C551180:2-(3,4-dihydro-2H-quinolin-1-yl)-2-oxo-ethyl ester; D000998:Antiviral Agents; D015853:Cysteine Proteinase Inhibitors; D011804:Quinolines; D015363:Quinolones; D056668:Cathepsin L
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