Rescuing compound bioactivity in a secondary cell-based screening by using γ-cyclodextrin as a molecular carrier

Area of Science:

• Virology
• Medicinal Chemistry
• Drug Discovery

Background:

• * Lead compounds identified in primary in vitro screening often fail in cell-based secondary screenings due to poor cellular internalization and metabolism.
• * Hepatitis C virus (HCV) NS3 protease inhibitors face challenges in achieving therapeutic efficacy in cell-based assays despite potent in vitro activity.

Purpose of the Study:

• * To investigate strategies for improving the cell-based efficacy of allosteric inhibitors targeting the HCV NS3 protease.
• * To evaluate the potential of gamma-cyclodextrin as a carrier molecule to enhance cellular uptake and antiviral activity of lead compounds.

Main Methods:

• * Identification of 15 allosteric inhibitors of HCV NS3 protease via a novel screening procedure.
• * Biophysical characterization of compound-target interactions.
• * Complexation of selected low-potency inhibitors with gamma-cyclodextrin.
• * Assessment of antiviral activity in cell-based assays.

Main Results:

• * Two out of three complexed compounds showed a 5-fold and 16-fold increase in activity compared to free compounds.
• * A third compound, inactive as a free agent, demonstrated significant antiviral activity (EC50 = 5 μM) when complexed with gamma-cyclodextrin.
• * Gamma-cyclodextrin alone exhibited no antiviral activity.

Conclusions:

• * Gamma-cyclodextrin complexation is an effective strategy to improve cellular internalization and rescue antiviral activity of HCV NS3 protease inhibitors.
• * This approach holds promise for advancing drug discovery by overcoming limitations of cell permeability in lead compounds.