Biochem/physiol Actions

PBOX-6 belongs to a group of tubulin-targeting pyrrolo-1,5-benzoxazepine (PBOX) compounds that potently induce apoptosis in a wide spectrum of cancer cells, including those originating from the four main types of leukemia and those exhibiting multi-drug resistance (IC50 = 2.28 µM/HL60-MDR1, 2.86 µM/HL60-ABCG2, 1.91 µM/HL60; IC50 = 4.71 µM/A2780-ADR, 4.10 µM/A2780). PBOX-6 inhibits the assembly of purified tubulin in cell-free assays and causes microtubule depolymerization in MCF-7 cells by binding a tubulin site distinct from those targeted by vinblastine and colchicine. When administered via intratumoral injection (7.5 mg/kg/day) in vivo, PBOX-6 is reported to significantly inhibit tumour growth in a murine model of neuroblastoma and a CML model of the imatinib-resistant T315I mutants.