Multiple myeloma (MM) is a clonal plasma B-cell neoplasm formed within the bone marrow. Despite being the second most common haematological malignancy after non-Hodgkin's Lymphoma, MM remains an incurable disease. Auranofin, a linear gold(I) compound known for its anti-arthritic properties has been recently trialled to treat a number of cancers including leukemia and lymphomas. Auranofin binds to the redox-sensitive selenocysteine residue present in thioredoxin reductase 1 (TrxR1) protein and therefore inhibits its activity. Previous studies in our lab demonstrated that auranofin exerts a significant anti-myeloma activity by inhibiting TrxR1 and increasing intracellular reactive oxygen species (ROS) levels. Although auranofin exerts a significant anti-cancer activity in vitro, its in vivo activity may be limited since it reacts readily and non-discriminately to protein thiols. In order to overcome these issues, a bis-chelated tetrahedral Au(I) phosphine complex called [Au(d2pype)2]Cl has been designed, which selectively targets selenol- and thiol- containing redox regulating proteins. In this study, we show that [Au(d2pype)2]Cl significantly inhibited TrxR1 activity in bortezomib-sensitive and resistant myeloma (RPMI8226 and U266) cells. [Au(d2pype)2]Cl treatment significantly inhibited cell proliferation and increased caspase-3 activity, an indicator of apoptosis, in bortezomib-sensitive and resistant myeloma cells. Currently we are investigating the underlying molecular mechanism for the anti-myeloma activity of this gold compound. Our findings indicate that this improved Au(I) compound exerts significant anti-myeloma activity in bortezomib-sensitive and resistant myeloma cells, suggesting it warrants further investigation in vivo.