It stratifies CLL based on response to ibrutinib (BTK group n = 50/184), response to the mTOR inhibitor everolimus but not to inhibition of upstream BTK (mTOR group n = 26/184), response to the MEK inhibitor selumetinib, but not to ibrutinib or everolimus (MEK group n = 23/184), and a group with weak response (n = 85/184). Here, BTK is linked to B-cell chronic lymphocytic leukemia.