On the same line of reasoning, the combination of veliparib and busulfan was effective in myeloproliferative neoplasm (MPN)/AML xenotransplanted models carrying the activating signaling mutation in JAK2V617F, where the pharmacological treatment caused G2/M arrest associated with activation of the ATR-CHK1 pathway [139]. The gene discussed is CHEK1; the disease is myeloproliferative disorder.