A novel derivative (GTN024) from a natural product, komaroviquinone, induced the apoptosis of high-risk myeloma cells via reactive oxygen production and ER stress.

New drugs have significantly improved the survival of patients with multiple myeloma (MM), but the prognosis of MM patients with high-risk cytogenetic changes such as t(4; 14), t(14; 16) or del17p remains very poor. A natural product, komaroviquinone (KQN), was originally isolated from the perennial semi-shrub Dracocephalum komarovi and has anti-protozoal activity against Trypanosoma cruzi, the organism causing Chagas' disease. Here we demonstrate that a novel KQN-derivative, GTN024, has an anti-MM effect both in vitro and in vivo. GTN024 induced the apoptosis of MM cell lines including those with high-risk cytogenetic changes. GTN024 produced reactive oxygen species (ROS) and increased phosphorylated eIF2α. The ROS production and subsequent endoplasmic reticulum (ER) stress are thought to play a key role in GTN024-induced apoptosis, as the apoptosis was completely abrogated by anti-oxidant treatment. In a mouse xenograft model, an intraperitoneal injection of 20 mg/kg of GTN024 significantly delayed tumor growth. Hematological toxicity and systemic toxicity as indicated by weight loss were not observed. These results suggest that the novel KQN-derivative GTN024 could become a candidate drug for treating high-risk MM.

Synthesis and biological evaluation of the natural product komaroviquinone and related compounds aiming at a potential therapeutic lead compound for high-risk multiple myeloma.

Alternatives of treatments for multiple myeloma (MM) have become increasingly available with the advent of new drugs such as proteasome inhibitors, thalidomide derivatives, histone deacetylase inhibitors, and antibody drugs. However, high-risk MM cases that are refractory to novel drugs remain, and further optimization of chemotherapeutics is urgently needed. We had achieved asymmetric total synthesis of komaroviquinone, which is a natural product from the plant Dracocephalum komarovi. Similar to several leading antitumor agents that have been developed from natural compounds, we describe the antitumor activity and cytotoxicity of komaroviquinone and related compounds in bone marrow cells. Our data suggested that komaroviquinone-related agents have potential as starting compounds for anticancer drug development.