The IGF1-R Inhibitor AEW541 Is a Potent Anti-Myeloma Agent That Overcomes Drugs Resistance, and Has Synergistic Activity with Other New Drugs.

Multiple myeloma (MM) represents an incurable disease for which development of new therapies is required. Here we report the effect on myeloma cells of AEW541, a new small molecule, belonging to the pyrrolo[2,3-d] pyrimidine class, identified as inhibitor of the IGF-1R in vitro kinase activity. AEW541 showed a potent antimyeloma activity (IC₅₀ <4.5 μM) on MM cell lines both sensitive (MM1S, U266, OPM2, RPMI8226) and resistant (MM1R and U266LR7) to conventional chemotherapeutic agents. In fresh cells from five MM patients a marked antitumor activity was confirmed. AEW541 showed a synergistic effect with dexamethasone and lenalidomide, while it was additive with melphalan and bortezomib. Moreover the triple combination of AEW541, bortezomib and dexamethasone showed even higher anti-MM activity. Gene expression profiles of MM1S cells identified a total of 967 genes to be significantly deregulated (transcriptional changes in gene expression of 2-fold or greater) by treatment with AEW541. The classification of these genes according to functional categories indicated that 3.5% were involved in apoptosis/responses to stress and 13% in the control of cell cycle/proliferation. By Western analyses, we observed that AEW541 affected genes involved in cell cycle and cell death pathways. AEW541 blocked cell cycle progression, and this was accompanied by p27, up-regulation and pRb, CCND1, CCNA and CCNE downregulation. AEW541 induced cell death through an increase in the mitochondrial outer membrane permeability and provoked DNA fragmentation. AEW541 induced apoptosis and at late time points, also activated caspases 8,9 and 3. The pan-caspase inhibitor Z-VAD-FMK only slightly decreased the sensitivity to AEW541. In addition, AEW541 stimulated a caspase-independent pathway, through the release of AIF and Endonuclease G from the mitochondria. It is therefore conceivable that both caspase dependent and independent pathways are activated by AEW541 in MM cells, although the effect of AEW541 on cell cycle arrest is an earlier and more potent event. Finally, AEW541 was able to overcome the protective effect that confers IL-6, IGF-1 and BMSCs to myeloma cells in a dose dependent manner. All these data indicate that AEW541 could be a useful drug for the treatment of MM patients, particularly in combination with other novel agents such as bortezomib or lenalidomide together with dexamethasone.