Identification of AB8939, a novel synthetic microtubule destabilizer and ALDH inhibitor that overcomes multidrug resistance in tumor cells as a drug candidate for the treatment of refractory acute myeloid leukemia

We identified AB8939, a novel small synthetic molecule that exhibits strong and broad antiproliferative activity against a panel of various cancer cell types with IC50 values in the nanomolar range. In vitro investigations showed that AB8939 is a novel microtubule-targeting agent that interacts with the colchicine-binding site of tubulin. AB8939 disrupts the microtubule network, leading to mitotic arrest in G2/M phase and subsequent apoptosis. Importantly, AB8939 overcomes drug resistance mechanisms, including overexpression of efflux transporters such as P-glycoprotein (P-gp) and aberrant expression of {beta}3-tubulin. AB8939 displays high cytotoxicity against blasts from AML patients, including blasts resistant to cytarabine (Ara-C). In vivo, AB8939 shows strong antitumor activity in MOLM-14, an Ara-C-resistant AML model, as evidenced by tumor growth inhibition and substantial increase in mouse survival. Further experiments performed on an AML PDX TG-AML-36 model demonstrated that AB8939 efficiently kills leukemic stem cells (CD34+/CD38-). Reverse proteomic experiments revealed that AB8939 inhibits ALDH1 and ALDH2, enzymes often overexpressed in tumors and tumor stem cells, thereby favoring tumor progression and relapse. AB8939 is a novel dual-targeting drug that acts on both tubulin and ALDH enzymes, with potential activity against various cancer types, especially refractory AML with complex karyotypes such as those displaying MECOM rearrangement and AML with mutations associated with poor prognosis, such as ASXL1 and TP53.