The CLL cells collected from patients treated for 1 month with ibrutinib at 420 mg per day had ratios of phosphorylated ERK1/2 versus total ERK1/2 that were comparable to that detected in the CLL cells of the same patients prior to therapy (Supplementary Fig. S7A, B), suggesting that ibrutinib does not inhibit the constitutive activation of ERK1/2 that apparently is induced by plasma Wnt5a. The gene discussed is WNT5A; the disease is B-cell chronic lymphocytic leukemia.