Basal AKT phosphorylation increases during ibrutinib. AKT basal and induced phosphorylation at S473 was analyzed by immunoblotting before and during therapy in a total of 13 patients with CLL. (A-B) Fold change relative to pre-therapy is shown (basal or anti-IgM–induced pAKT/AKT pretherapy values were set to 1). Bars show mean ±SEM. P values were calculated using the Wilcoxon rank test. (C) Association between inducibility of pAKT and sIgM expression is shown. Levels of sIgM were determined before start of ibrutinib therapy. The statistical difference was calculated using the Mann-Whitney U-test.