Colorectal cancer will claim approximately 55,000 lives in the U.S. in 2005, and although recent advances have been improved survival incrementally, new treatment options and strategies are desperately needed.  Cell signaling inhibitors have recently emerged as a successful anti-tumor strategy, and an antibody inhibitor of the EGFR pathway has made it to the colon cancer clinic.  Another attractive target for anticancer drugs is the Ras/Raf/Mek/Erk signaling cascade, which promotes tumor cell growth, angiogenesis, and resistance to apoptosis.  Mutations that constitutively activate the Ras oncogenic signaling pathway are highly prevalent in colorectal cancer (50-70%).  In addition, the Ras pathway is part of the signaling network for EGFR, which is a validated target in colorectal cancer.  One major obstacle to the development of signal transduction inhibitors is cross-talk between signaling pathways, which can subvert the effects of a given inhibitor.  Our laboratory has found that combinations of inhibitors may overcome this challenge, where a cell line xenograft that is resistant to an EGFR or Erk inhibitor alone becomes sensitive when the two are combined.  BAY 43-9006 is a novel oral Raf kinase inhibitor with inhibitory activity against VEGFR and PDGFR as well.  We hypothesize that combining BAY 43-9006 with the standard treatment for chemoresistant advanced colorectal cancer (irinotecan/cetuximab) will result in synergistic antitumor effects.  The goal is to complete a phase I/I I clinical, pharmacological, and biological study of BAY 43-9006 in combination with cetuximab and irinotecan in patients with advanced colorectal cancer.  Utilizing a lead-in design of BAY 43-9006 with cetuximab, combined with pre- and post treatment tumor and normal tissue samples, the biological effects of this combination will be fully characterized.  Phamacokinetic and pharmacodynamic studies of this combination will represent the foundation and rationale for further studies. [ unreadable] [unreadable] [unreadable]