Bossler, Felicitas

Abstract Inhibitors of the proteasome-ubiquitin system have been found to be effective in the clinical management of multiple myeloma. We here describe the compound VLX1570, an optimized lead of the 19S deubiquitinase inhibitor b- AP15. VLX1570 was shown to inhibit the enzymatic activities of both USP14 and UCHL5 in vitro, and was shown to induce accumulation of high molecular weight polyubiquitinated proteins in multiple myeloma cells. The compound showed limited inhibitory activity of a panel of kinases. VLX1570 induces apoptosis and cell death of multiple myeloma cell lines at submicromolar concentrations. Importantly, a multiple myeloma cell line selected for bortezomib resistance was found to be sensitive to VLX1570. VLX1570 was found to be able to overcome apoptosis resistance by these cells. Induction of the phosphorylation of stress-activated kinases (JNK and p38) and inhibition of ERK phosphorylation was observed in multiple myeloma cells. We finally showed that VLX1570 confers antineoplastic activity in two different myeloma xenograft models and conclude that VLX1570 is a candidate agent for treatment of multiple myeloma. Citation Format: Xin Wang, Chitralehka Mohanty, Padraig D'Arcy, Maria Hägg Olofsson, Felicitas Bossler, Asher Chanan-Khan, Stig Linder. Development of the proteasome deubiquitinase inhibitor VLX1570 for treatment of multiple myeloma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4557A. doi:10.1158/1538-7445.AM2015-4557A