Discovery of 3-Cyano- N-(3-(1-isobutyrylpiperidin-4-yl)-1-methyl-4-(trifluoromethyl)-1 H-pyrrolo[2,3- b]pyridin-5-yl)benzamide: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor C2 Inverse Agonist.

The nuclear hormone receptor retinoic acid receptor-related orphan C2 (RORC2, also known as RORγt) is a promising target for the treatment of autoimmune diseases. A small molecule, inverse agonist of the receptor is anticipated to reduce production of IL-17, a key proinflammatory cytokine. Through a high-throughput screening approach, we identified a molecule displaying promising binding affinity for RORC2, inhibition of IL-17 production in Th17 cells, and selectivity against the related RORA and RORB receptor isoforms. Lead optimization to improve the potency and metabolic stability of this hit focused on two key design strategies, namely, iterative optimization driven by increasing lipophilic efficiency and structure-guided conformational restriction to achieve optimal ground state energetics and maximize receptor residence time. This approach successfully identified 3-cyano- N-(3-(1-isobutyrylpiperidin-4-yl)-1-methyl-4-(trifluoromethyl)-1 H-pyrrolo[2,3- b]pyridin-5-yl)benzamide as a potent and selective RORC2 inverse agonist, demonstrating good metabolic stability, oral bioavailability, and the ability to reduce IL-17 levels and skin inflammation in a preclinical in vivo animal model upon oral administration.

Synthesis, biological evaluation, and modeling studies of inhibitors aimed at the malarial proteases plasmepsins I and II.

The increasing resistance of the malarial parasite to antimalarial drugs is a major contributor to the reemergence of the disease and increases the need for new drug targets. The two aspartic proteases, plasmepsins I and II, from Plasmodium falciparum have recently emerged as potential targets. In an effort to inhibit these hemoglobinases, a series of inhibitors encompassing a basic hydroxyethylamine transition state isostere as a central fragment were prepared. The synthesized compounds were varied in the P1' position and exhibited biological activities in the range of 31 to >2000 nM. To try to rationalize the results, molecular docking and 3D-QSAR analysis were used.

High-speed optimization of inhibitors of the malarial proteases plasmepsin I and II.

Four focused libraries targeted for inhibition of the malarial proteases plasmepsin I and II were designed, synthesized, purified, and screened. Selected carboxylic acids and organometallic reactants with diverse physical properties were attached to the hydroxylethylamine scaffold in the P3 and P1' positions to furnish inhibitors with highly improved activity. The concept of controlled and sequential microwave heating was employed for rapid library generation. This combinatorial optimization protocol afforded plasmepsin inhibitors not only with K(i) values in the low nanomolar range, but also with high selectivity versus the human protease cathepsin D. With this class of inhibitory agents, modifications of the P1' substituents resulted in the largest impact on the plasmepsin/cathepsin D selectivity.

Design and synthesis of plasmepsin I and plasmepsin II inhibitors with activity in Plasmodium falciparum-infected cultured human erythrocytes.

A series of protease inhibitors targeted at the malarial enzymes plasmepsin I and II, and encompassing a basic hydroxyethylamine transition state isostere scaffold, was prepared. The substituents in the P1' position were varied and the biological activities expressed in K(i)-values ranged from 60 to >2000 nM. A more than 4-fold selectivity for either of the plasmepsins could be achieved. All of the active compounds exhibited high preference for the plasmepsins over cathepsin D, the most closely related human protease. A few active compounds were shown to inhibit parasite growth in cultured infected human erythrocytes. An ED(50) value as low as 1.6 microM was observed for one of the inhibitors despite K(i) values of 115 nM (Plm I) and 121 nM (Plm II).