PS-341, a potent and selective proteasome inhibitor, is the prototype for a new class of therapeutics that targets the ubiquitin - proteasome pathway. It is active as a single agent and potentiates chemotherapy and radiation in pre-clinical models. Early phase clinical studies have demonstrated tolerability and activity in multiple myeloma, lymphoma, prostate cancer and lung cancer. By its mechanism of inhibiting protein degradation, PS-341 targets a wide-range of pathways that are relevant to tumor progression and therapy resistance, and can directly modulate expression of cyclins, p27(Kip1), p53, NF-kappaB, Bcl-2 and Bax. PS-341 is currently in phase I/II clinical development in lung cancer. This paper wilt review the pre-clinical and clinical experience with PS-341 as it relates to lung cancer. (C) 2003 Elsevier Science Ireland Ltd and American Society of Clinical Oncology. Published by Elsevier Science Ireland Ltd. All. rights reserved.