Dual inhibition of mTORC1/2 by DCZ0358 induces cytotoxicity in multiple myeloma and overcomes the protective effect of the bone marrow microenvironment.

Interaction of multiple myeloma (MM) cells with the bone marrow (BM) microenvironment promotes the proliferation, survival and chemoresistance of MM. The mTOR pathway plays a key role in these undesirable BM microenvironment-mediated events. We synthesized a novel alkaloid compound, DCZ0358, that effectively inhibits mTOR signaling via dual mTORC1/2 inhibition and exhibits potent anti-MM activity in cultured and primary MM cells, as well as a MM xenograft model but has little effect on normal cells. Importantly, we show that this compound can block the BM stromal cell-mediated activation of mTOR/Akt signaling and antagonizes the protective effect of the BM microenvironment. Moreover, DCZ0358 abrogates the bortezomib-triggered activation of Akt, leading to the synergism of DCZ0358 and bortezomib in MM cells. Taken together, our results provide the proof-of-concept for clinical evaluation of DCZ0358, alone or in combination, as an anti-MM agent in MM therapy.