MS-553 + venetoclax + rituximab

MS-553 + venetoclax + rituximab is a **combination regimen under early clinical investigation for chronic lymphocytic leukemia (CLL)**, especially in patients with relapsed or refractory disease who have failed previous targeted therapies, including BTK inhibitors. - **MS-553** is a novel, highly selective, oral small molecule inhibitor of **protein kinase C beta (PKCβ)**, a key signaling molecule downstream of the B-cell receptor pathway, critical for CLL cell survival and proliferation. Preclinical and early clinical data indicate that PKCβ inhibition by MS-553 can overcome BTK inhibitor resistance and has cytotoxic effects in both treatment-naive and heavily pretreated CLL patients[1][2][3][4][5]. - **Venetoclax** is an oral small molecule inhibitor of **B-cell lymphoma 2 (BCL-2)**, promoting apoptosis in CLL cells by targeting their heightened dependence on BCL-2 for survival. - **Rituximab** is a chimeric monoclonal antibody targeting **CD20** on B lymphocytes, mediating cell death via immune mechanisms. This combination is being investigated due to rationale that **MS-553 may sensitize CLL cells to venetoclax by increasing BCL-2 dependence**, potentially yielding enhanced efficacy when administered with venetoclax and rituximab[3]. Early-phase studies are ongoing to determine safety, tolerability, and preliminary efficacy in high-risk/refractory CLL[3][5].