Data emanating from clinical studies indicate about 30% of patients given navitoclax, which inhibits BCL-XL and BCL-2, following failure of ruxolitinib treatment were able to achieve a 35% reduction in spleen volume with favorable impacts on MPN-driving allele burden and bone marrow fibrosis being observed as well [54]. This evidence concerns the gene BCL2L1 and myeloproliferative neoplasm.