Project Summary/Abstract The rapidly increasing incidences of infections caused by multidrug-resistant Gram-negative bacteria represent an emerging global health care crisis. The fact that no new class of medication against Gram- negative bacteria has been introduced into practice over half of a century, combined with the lengthy development and approval process, add to the urgency to accelerate and streamline research and development processes for new treatment approaches to Gram-negative bacterial infections. LpxC (UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase) is an essential enzyme in the biosynthesis of lipid A, the hydrophobic anchor of lipopolysaccharide and the major lipid component of the outer monolayer of the Gram-negative bacterial outer membrane. Constitutive lipid A biosynthesis is required for bacterial viability and fitness in the human host. As such, LpxC is an attractive target to create a novel class of small molecule inhibitors as antibacterial agents specific to Gram-negative bacterial pathogens. Extensive research over the last two decades shows that (1) potent LpxC inhibitors display outstanding bactericidal effect; (2) with few exceptions in vitro, virtually all Gram-negative bacteria are sensitive to LpxC inhibition in vivo; and (3) LpxC inhibitors are not inactivated by common resistance mechanisms such as extended- spectrum -lactamases (ESBL) or carbapenemases. Although dose-limiting adverse effects have limited the development of the most advanced LpxC inhibitors, ACHN-975 (Achaogen) and RC-0 1 (Recida Therapeutics), these compounds do not show the same liabilities, suggesting that the observed adverse effects do not represent a class limitation. Valanbio Therapeutics was founded to translate basic research activities from Duke University into a potential new class of antibacterial agents against Gram-negative pathogens. Duke University and Valanbio Therapeutics have identified a lead LpxC inhibitor, LPC-233, which we seek to advance to the clinical stage testing. LPC-233 is potently and broadly bactericidal against Gram-negative bacteria in vitro and significantly reduces bacterial counts in the murine thigh infection model at doses as low as 2 mg/kg BID. It also displays an outstanding safety profile in rats. In this proposal, Valanbio Therapeutics plans to (1) develop GMP- compatible large-scale synthesis of LPC-233; (2) continue to evaluate and optimize the efficacy and dosing regimen of LPC-233 against susceptible and multidrug-resistant Gram-negative bacterial pathogens in mice; (3) investigate the potential dose-limiting safety liabilities in vitro and in vivo. The successful execution of the proposed studies will clear the path for IND filing and advance LPC-233 to Phase I human clinical trials.