The purpose of this Phase 1/2 open-label study is to determine the safety and efficacy of a
cetuximab and PX-866 combination treatment. In the Phase 1 part of the study, the dose of
PX-866 to be given in combination with cetuximab will be determined in patients with
incurable metastatic CRC or incurable progressive, recurrent or metastatic SCCHN. The Phase 2
part of the study is a randomized evaluation of the antitumor activity and safety of PX-866
in combination with cetuximab versus cetuximab alone in patients with either incurable
metastatic CRC who have a history of progression or recurrence following prior irinotecan and
oxaliplatin containing regimens or are intolerant of irinotecan (Group 1) or incurable
progressive, recurrent or metastatic SCCHN (Group 2).