Anna Karin Belfrage

Synthesis and SAR of potent inhibitors of the Hepatitis C virus NS3/4A protease: Exploration of P2 quinazoline substituents

Novel NS3/4A protease inhibitors comprising quinazoline derivatives as P2 substituent were synthesized. High potency inhibitors displaying advantageous PK properties have been obtained through the optimization of quinazoline P2 substituents in three series exhibiting macrocyclic P2 cyclopentane dicarboxylic acid and P2 proline urea motifs. For the quinazoline moiety it was found that 8-methyl substitution in the P2 cyclopentane dicarboxylic acid series improved on the metabolic stability in human liver microsomes. By comparison, the proline urea series displayed advantageous Caco-2 permeability over the cyclopentane series. Pharmacokinetic properties in vivo were assessed in rat on selected compounds, where excellent exposure and liver-to-plasma ratios were demonstrated for a member of the 14-membered quinazoline substituted P2 proline urea series.

Discovery of pyrazinone based compounds that potently inhibit the drug-resistant enzyme variant R155K of the hepatitis C virus NS3 protease

Herein, we present the design and synthesis of 2(1H)-pyrazinone based HCV NS3 protease inhibitors with variations in the C-terminus. Biochemical evaluation was performed using genotype 1a, both the wild-type and the drug resistant enzyme variant, R155K. Surprisingly, compounds without an acidic sulfonamide retained good inhibition, challenging our previous molecular docking model. Moreover, selected compounds in this series showed nanomolar potency against R155K NS3 protease; which generally confer resistance to all HCV NS3 protease inhibitors approved or in clinical trials. These results further strengthen the potential of this novel substance class, being very different to the approved drugs and clinical candidates, in the development of inhibitors less sensitive to drug resistance.

Pan-NS3 protease inhibitors of hepatitis C virus based on an R3-elongated pyrazinone scaffold

Herein, we present the design and synthesis of 2(1H)-pyrazinone based HCV NS3 protease inhibitors and show that elongated R3 urea substituents were associated with increased inhibitory potencies over several NS3 protein variants. The inhibitors are believed to rely on β-sheet mimicking hydrogen bonds which are similar over different genotypes and current drug resistant variants and correspond to the β-sheet interactions of the natural peptide substrate. Inhibitor 36, for example, with a urea substituent including a cyclic imide showed balanced nanomolar inhibitory potencies against genotype 1a, both wild-type (Ki = 30 nM) and R155K (Ki = 2 nM), and genotype 3a (Ki = 5 nM).