In a phase Ib/II study of 14 patients (phase I) and 51 patients (phase II) with advanced solid tumors, Rosen and colleagues noted single-agent activity with carfilzomib. Carfilzomib was dosed on days 1, 2, 8, 9, 15, and 16 of a 28 day cycle to a maximum of 12 cycles, with 20-36 mg/m² noted as the recommended phase 2 dose based on DLT data. A PR in both renal and small cell lung cancer, and stable disease > 16 weeks in mesothelioma, ovarian, renal, and non-small cell lung cancer was observed. The treatment was tolerable with the most common adverse events (AEs) including fatigue, headache, diarrhea, nausea and constipation.