LFM-A13 significantly inhibits BTK activity with an IC50 of 6.2 ± 0.3 μg/mL (= 17.2 ± 0.8 μM). The calculated Kis of LFM-A13 for BTK, JAK1, JAK3, IRK, EGFR and HCK are 1.4, 110, 148, 31.6, 166 and 214 μM. LFM-A13 (200 μM) markedly increases the chemosensitivity of ALL-1 cells to ceramide-induced apoptosis. LFM-A13 (100 μM) suppresses Epo-induced phosphorylation of EpoR, Jak2, Btk, Stat5 and Erk1/2 in R10 cells. LFM-A13 (100 μM) inhibits auto-phosphorylation of Jak2, Tec and Btk rather than Lyn kinase auto-phosphorylation in COS cells. LFM-A13 potently inhibits Plx1 with IC50 of 10 μM; also inhibits BRK, BMX, FYN and with IC50s of 267, 281, 240 and 215 μM.