Boehringer Ingelheim (canada) Ltd.

Boehringer Ingelheim International Gmbh

Daniel Lamarre

Louise Pilote

Charles Pellerin

George Kukolj

Arnim Pause

Roger Maurice

Diane Thibeault

Martin Marquis

Armin Pause

Lisette Lagacé

Lisette Lagace

The present invention concerns the development of a cell-based assay system having improved sensitivity to HCV NS3 protease activity when compared to known assays, which is useful for screening test compounds capable of modulating (particularly inhibiting) HCV NS3 protease activity. This system provides a first construct comprising a transactivator domain joined downstream of the NS3-5 domains of HCV under the control of a non-cytopathic viral promoter system. A second construct is also provided that comprises a reporter gene under the control of an operator sensitive to the binding of the transactivator. The NS3-5 domains encodes the NS3 polyprotein which comprises: the NS3 protease, followed by the NS4A co-factor, the NS4B and NS5A proteins (including any derivative, variant or fragment thereof, terminated by the NS5B protein (including any derivative, variant or fragment thereof) sufficient to constitute a NS5A/5B cleavage site. The transactivator, when expressed and released from the polyprotein initiates transcription and expression of the reporter gene that is measurable.

Surrogate cell-based system and method for assaying the activity of hepatitis C virus NS3 protease

The present invention concerns the development of a cell-based assay system having improved sensitivity to HCV NS3 protease activity when compared to known assays, which is useful for screening test compounds capable of modulating (particularly inhibiting) HCV NS3 protease activity. This system provides a first construct comprising a transactivator domain joined downstream of the NS3&#x2013;5 domains of HCV under the control of a non-cytopathic viral promoter system. A second construct is also provided that comprises a reporter gene under the control of an operator sensitive to the binding of the transactivator. The NS3&#x2013;5 domains encodes the NS3 polyprotein which comprises: the NS3 protease, followed by the NS4A co-factor, the NS4B and NS5A proteins (including any derivative, variant or fragment thereof), terminated by the NS5B protein (including any derivative, variant or fragment thereof) sufficient to constitute a NS5A/5B cleavage site. The transactivator, when expressed and released from the polyprotein initiates transcription and expression of the reporter gene that is measurable.

A method for producing a refolded, inactive form of recombinantly produced NS2/3 protease which comprises the steps of: a) purifying the protease from inclusion bodies in the presence of a chaotropic agent; and b) refolding the purified protease by contacting it with a reducing agent and lauryldiethylamine oxide (LDAO) in the presence of reduced concentration of chaotropic agent or polar additive. The invention further comprises a method for activating this refolded inactive NS2/3 protease by adding an activation detergent. This method produces large amounts of the active NS2/3 protease to allow small molecules and ligands to be screened as potential inhibitors of NS2/3 protease, which may be useful as therapeutic agents against HCV.

Purified active HCV NS2/3 protease

An inhibitor-resistant HCV NS3 protease is provided which is useful to screen for compounds having therapeutic value against drug resistant HCV strains. In particular, the inhibitor-resistant HCV NS3 protease comprises an amino acid sequence which is mutated in the substrate binding pocket thereof rendering the protease resistant to inhibitor. In a specific aspect of the present invention, at least one of the amino acids at position 155, 156 and 168 of the HCV NS3 protease is mutated to yield an inhibitor-resistant protease.

Inhibitor-resistant HCV NS3 protease

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Terrebonne, Canada

Daniel Lamarre