Research in my laboratory has made critical findings related to the molecular, cellular, and genetic basis of Myelodysplastic Syndromes (MDS), a complex and poorly understood hematopoietic stem cell (HSC) failure syndrome. The complexity and heterogeneity of MDS, and the lack of mouse models, remain as major obstacles to understanding and effectively treating this disease. Overexpression of immune-related genes is widely reported in MDS, and chronic innate immune pathway activation, primarily via Toll-like receptors (TLRs), increases the risk of developing MDS. Multiple independent mechanisms contribute to hyperactivation of TLR signaling in MDS, which converge on the central complex involving IRAK1, IRAK4, and TRAF6. Based on our published and preliminary data, IRAK1 and IRAK4 (IRAK1/4), a dual kinase complex is activated in MDS patients. Moreover, the importance of the IRAK1/4-TRAF6 complex in primary MDS comes from our recent observation that describes genetic and pharmacologic approaches to inhibit IRAK1/4 as effective agents to suppress TRAF6 and the MDS clone. Collectively, these molecular and genetic alterations clearly implicate IRAK1/4-TRAF6 signaling as a pathogenic driver and druggable complex in MDS. Therefore, we hypothesize that small molecule dual inhibitors of IRAK1 and IRAK4 will suppress MDS-propagating cells. We derived a novel chemical series of potent dual IRAK1/4 inhibitors. The lead compound shows potent inhibition of IRAK1 and IRAK4 in MDS, efficacy at suppressing MDS cell viability and function in vitro, and promising pharmacokinetic and pharmacodynamics properties in vivo. As such, the objective of this proposal is to optimize and evaluate our candidate dual IRAK1/4 inhibitors in human MDS cells in vitro (Aim 1), and in mouse and human MDS models in vivo (Aim 2). The specific aims will provide necessary preclinical information on the therapeutic potential of rationally designed dual IRAK1/4 inhibitors for future human MDS trials.