Synergy calculations confirm that the benefit of the combination is more than additive. MM.1S cells were plated in triplicate and concurrently treated with bortezomib (up to 10 nm) and lonafarnib (up to 6 μM) for 48 hours. MTT assays were performed to assess growth inhibition. Dose-effect curve and isobologram obtained for the MM.1S cell line are shown.