Design, synthesis, and biological evaluation of novel water-soluble triptolide derivatives: Antineoplastic activity against imatinib-resistant CML cells bearing T315I mutant Bcr-Abl.

Imatinib (STI571) is the frontline targeted-therapeutic agent for patients with chronic myelogenous leukemia (CML). However, resistance to imatinib due to point mutations in Bcr-Abl kinase domain is an emerging problem. We recently reported that triptolide (compound 1) could effectively kill CML cells including those harboring T315I mutant Bcr-Abl. In the present study, we designed a series of C-14 triptolide derivatives with C-14-hydroxyl substituted by different amine esters (3-18): 3-6 and 13 (by aliphatic chain amine esters); 7-9, 11, 12 and 15-18 (by alicyclic amine esters with different size), and 10 and 14 (by aralkylamine esters).The compounds were examined for their antineoplastic activity against CML cells (including KBM5-T315I cells) in terms of proliferation inhibition, apoptosis and signal transduction. Nude mouse xenograft model was also used to evaluate the in vivo activity. Compounds 2-9, 11-14, 17 and 18 exhibited a potent inhibitory activity against KBM5 and KBM5-T315I cells. This series of derivatives down-regulated Bcr-Abl mRNA. Compounds 4, 5, 8 and 9 were further examined for their impact on signaling and apoptosis with immunoblotting. Compound 5 was chosen for evaluation in a nude mouse xenograft model. The stereo-hindrance of C-14 group appeared to be responsible for the antitumor effect. The computational small molecule-protein docking analysis illustrated the possible interaction between compound 9 and RNA polymerase II. Our results suggest that this series of derivatives may be promising agents to overcome imatinib-resistance caused by the Bcr-Abl-T315I mutation.