Initial in vivo efficacy testing of PVEK was carried out against eight PDXs consisting of three BCP‐ALL (ALL‐2, ALL‐7, ALL‐19), three MLLr‐ALL (ALL‐3, MLL‐1, MLL‐5), and two Ph+‐ALL (ALL‐4, ALL‐55) PDXs (Figure 2A–D, Supporting Information S1: Figure S2 and Table 1). The gene discussed is KMT2A; the disease is acute lymphoblastic leukemia.