Our overall objective of this R61/R33 proposal is to design and study novel therapeutic agents for sickle cell disease (SCD) that inhibit and/or destabilize the initial, hypoxia-induced hemoglobin (Hb) polymerization, thereby reducing the subsequent secondary pathophysiology, with minimal liability for toxicity. When deoxygenated, sickle Hb polymerizes into long, rigid, and insoluble fibers, causing red blood cells (RBCs) to sickle. The proposal leverages the complementary expertise, commitment, and experience of the investigative team; and a compelling body of preliminary data to test the hypothesis that novel synthetic molecules that directly destabilize polymer formation, in addition to increasing Hb affinity for O2, will provide a superior therapeutic option for SCD. The specific aims are: 1: Design, synthesize and conduct in-vitro functional and biological assessment of novel vanillin derivatives. We have previously established novel antisickling derivatives that exhibit significant pharmacologic improvement over their parent compounds. This aim further utilizes an intricate and informed strategy to derivatize lead compounds to increase direct polymer destabilization, as well as decrease stoichiometry of compound binding to Hb. We will subject the compounds to a battery of screening assays to evaluate in-vitro functional and biological properties, to include Hb modification, inhibition of cell sickling, effect on Hb affinity for O2, and X-ray crystallography to elucidate their atomic interactions with Hb. Aim 1 studies will identify superior candidates and inform further structural modifications to enhance potency for subsequent Aim 2 studies of the R61 phase. 2: Establish Hb binding kinetics, in-vitro metabolism and ADME, and preliminary in-vivo pharmacodynamics properties of select compounds. In this concluding Aim of the R61 phase, we will conduct further validation studies on select candidates from Aim 1. Specifically, we will characterize their efficiency of partitioning into the RBC compartment and Hb binding kinetics, in-vitro metabolic and ADME/safety profiles, and preliminary in-vivo pharmacodynamic profiles. Results from the planned studies will firmly and conclusively identify and validate superior lead molecule(s) for further development in Aim 3 (R33 Phase). 3: Conduct in-vivo functional and biological studies to establish promising lead compounds for development. Aim 3 (R33) will focus on in-vivo PK/PD efficacy studies in wild-type and SCD mice. We will conduct scale-up synthesis of optimized lead molecules, optimize formulation, and formally conduct detailed in- vivo PK/PD and efficacy studies that include in-vivo modification of Hb to the non-sickling, high affinity variant; reduction in circulating sickled cells under normoxia and hypoxia; amelioration of hemolysis, inflammation, endothelial damage; and overall reversal of the SCD pathophysiology observed in this model. The novel compounds are expected to exhibit enhanced ef...