Discovery of potent bifunctional small molecules targeting DNA-PK and HDAC6 with desirable pharmacokinetic properties for acute myeloid leukemia treatment.

DNA-PK serves as a critical mediator in DNA damage repair, with its activity modulated by the epigenetic regulator HDAC6. Building on our previous findings that HDAC inhibitors can enhance the DNA damage response, we rationally designed and evaluated a novel series of dual-targeting inhibitors co-targeting DNA-PK and HDAC6 for their therapeutic potential in acute myeloid leukemia (AML). Among these candidates, DH-1 exhibits potent and balanced inhibitory activities against DNA-PK (IC = 84.2 nM) and HDAC6 (IC = 64.8 nM), while potently suppressing the proliferation of AML cells. Mechanistic investigations revealed that DH-1 can arrest AML-derived HL-60 cells in the G/M phase and elevate γ-H2AX levels (a well-recognized hallmark of DNA double-strand breaks). Remarkably, DH-1 demonstrates favorable pharmacokinetic properties in Sprague-Dawley (SD) rats, featuring moderate oral bioavailability (14.4 %) and a satisfactory half-life (7.9 h, p.o.). Furthermore, DH-1 exhibits robust antitumor efficacy in multiple AML models, with a tumor growth inhibition (TGI) rate of 67.9 %. In summary, DH-1 represents a promising DNA-PK/HDAC6 dual-functional inhibitor with superior in vivo efficacy and desirable pharmacokinetic profiles, strongly supporting its further preclinical advancement.