In vitro and In vivo Antitumor Activity of a Novel Alkylating Agent Melphalan-flufenamide Against Multiple Myeloma Cells
Menée in vitro et à l'aide de xénogreffes de myélome multiple, cette étude évalue l'activité antitumorale d'un nouveau promédicament du melphalan, le Mel-flufen
Purpose: The alkylating agent melphalan prolongs survival in multiple myeloma (MM) patients; however, it is associated with toxicities and development of drug-resistance. Here, we evaluated the efficacy of melphalan-flufenamide (Mel-flufen), a novel dipeptide prodrug of melphalan in MM. Experimental Design: MM cell lines, primary patient cells, and the human MM xenograft animal model were utilized to study the antitumor activity of mel-flufen. Results: Low doses of mel-flufen triggers a more rapid and higher intracellular concentrations of melphalan in MM cells than is achievable by free melphalan. Cytotoxicity analysis showed significantly lower IC50 of mel-flufen than melphalan in MM cells. Importantly, mel-flufen induces apoptosis even in melphalan-, and bortezomib-resistant MM cells. Mechanistic studies show that siRNA knockdown of aminopeptidase N, a key enzyme mediating intracellular conversion of mel-flufen to melphalan, attenuates anti-MM activity of mel-flufen. Furthermore, mel-flufen-induced apoptosis was associated with: 1) activation of caspases and PARP cleavage; 2) ROS generation; 3) mitochondrial dysfunction and release of cytochrome-c; and 4) induction of DNA damage. Moreover, mel-flufen inhibits MM cell migration and tumor-associated angiogenesis. Human MM xenograft studies showed a more potent inhibition of tumor growth in mice treated with mel-flufen than mice receiving equimolar doses of melphalan. Finally, combining mel-flufen with lenalidomide, bortezomib, or dexamethasone triggers synergistic anti-MM activity. Conclusions: Our preclinical study supports clinical evaluation of mel-flufen to enhance therapeutic potential of melphalan, overcome drug-resistance, and improve MM patient outcome.