RIGScan® CR49, a125I-labelled CR monoclonal antibody directed against the tumour-associated antigen TAG-72, is undergoing development with Neoprobe for the intraoperative detection of metastatic colorectal cancer.The Neoprobe's proprietary RIGS®(radioimmunoguided surgery) technology combines an injectable radiolabelled cancer-targeting agent and hand-held radiation detection probe that emits an audible tone when located tissue has accu-mulated a significant amount of the radioactive agent. Neoprobe's RIGS®technology also includes a patented surgical method providing surgeons with real-time information to locate tumour deposits that can not be detected by other conventional methods.The RIGS®technology has been evaluated in late clinical studies for the detection of adenocarcinomas including primary colorectal, gastrointestinal, breast, ovarian, pancreatic, prostate and neuroendocrine/endocrine.Neoprobe signed an option agreement for its first-generation RIGScan®compound, RIGScan®CR, with OncoSurg Inc. (formerly NuRigs Ltd). The second-generation humanised RIGScan®CR agent was also optionally licensed to OncoSurg Inc.In 1997, Neoprobe filed for approval with the US FDA and the EMEA for RIGScan® CR for the intraoperative detection of metastatic colorectal cancer. Both regulatory agencies have requested additional clinical data.On 19 April 2004, Neoprobe announced that it had met with the US FDA to discuss its position on submitting additional clinical information in response to the FDA's questions regarding the Biologic Licence Application (BLA) for RIGScan® CR49. The company provided the FDA with new information related to a survival differential for patients whose colorectal cancer was evaluated with RIGScan® CR49. The information was not available at the time of the BLA's submission in 1997. The agency indicated that it would consider accepting survival data from one of the two phase III trials, NEO2-14, but not from another trial NEO2-13, as supportive data for a prognostic indication for colorectal cancer. The FDA also clarified that two well controlled studies were required for approval, and indicated that Neoprobe needed to complete an additional confirmatory phase III study for a prognostic indication in colorectal cancer.[1]In its Annual Report 2002, Neoprobe stated that it had been working to secure a partner for further development of its proprietary RIGS®technology. The company intends either to find a development partner or sell or licence out their RIGS®assets if the partner is not found.