B-cell chronic lymphocytic leukemia (CLL) results from intrinsic genetic defects and complex microenvironment stimuli that fuel CLL cell growth through an array of survival signaling pathways. Novel small-molecule agents targeting the B-cell receptor pathway and anti-apoptotic proteins alone or in combination have revolutionized the management of CLL, yet combination therapy carries significant toxicity and CLL remains incurable due to residual disease and relapse. Single-molecule inhibitors that can target multiple disease-driving factors are thus an attractive approach to combat both drug resistance and combination-therapy-related toxicities. We demonstrate that SRX3305, a novel small-molecule BTK/PI3K/BRD4 inhibitor that targets three distinctive facets of CLL biology, attenuates CLL cell proliferation and promotes apoptosis in a dose-dependent fashion. SRX3305 also inhibits the activation-induced proliferation of primary CLL cells in vitro and effectively blocks microenvironment-mediated survival signals, including stromal cell contact. Furthermore, SRX3305 blocks CLL cell migration toward CXCL-12 and CXCL-13, which are major chemokines involved in CLL cell homing and retention in microenvironment niches. Importantly, SRX3305 maintains its anti-tumor effects in ibrutinib-resistant CLL cells. Collectively, this study establishes the preclinical efficacy of SRX3305 in CLL, providing significant rationale for its development as a therapeutic agent for CLL and related disorders.

The quinoxaline core is found in several biologically active compounds, with Erdafitinib being the first FDA-approved quinoxaline derivative that targets a kinase and exhibits anti-cancer properties. We previously reported a quinoxaline analog (84) that displayed anti-cancer effects by inhibiting IKKβ, a key kinase in the NFκB pathway. Here, we present the synthesis of a regioisomer (51-106) and its characterization as a selective MAP3K1 inhibitor with improved metabolic stability and oral bioavailability. We used the small molecule MAP3K1 inhibitor in a proteomics study that identified NPM1 as a member of the MAP3K1 network.