ruxolitinib + ribociclib

text_content: **ruxolitinib + ribociclib** is a combination of two small molecule kinase inhibitors under investigation for their synergistic antineoplastic effects, primarily in the treatment of myelofibrosis and potentially other myeloproliferative neoplasms. Ruxolitinib is a selective inhibitor of Janus kinase 1 (JAK1) and Janus kinase 2 (JAK2), interrupting the JAK-STAT signaling pathway to reduce abnormal cell proliferation and cytokine production. Ribociclib is a selective inhibitor of cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6), causing cell cycle arrest at the G1 phase by blocking retinoblastoma (pRb) protein phosphorylation. Preclinical studies suggest combining ruxolitinib with a CDK4/6 inhibitor leads to greater normalization of blood counts, reduction of splenomegaly, and improvement in bone marrow fibrosis compared to monotherapy. Clinical use is investigational; no approved combination formulation exists.