Phase I trial of 131I-huA33 in patients with advanced colorectal carcinoma

Geoffrey Chong, Fook Thean Lee, Wendie Hopkins, Niall Tebbutt, Jonathan S. Cebon, Angela J. Mountain, Bridget Chappell, Anthony Papenfuss, Paul Schleyer, Paul U, Roger Murphy, Veronika Wirth, Fiona E. Smyth, Nicole Potasz, Aurora Poon, Ian D. Davis, Tim Saunder, Graeme J. O'Keefe, Antony W. Burgess, Eric W. HoffmanLloyd J. Old, Andrew M. Scott

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Purpose: Humanized monoclonal antibody A33 (huA33) targets the A33 antigen which is expressed on 95% of colorectal cancers. A previous study has shown excellent tumor-targeting of iodine-131 labeled huA33 (131I-huA33). Therefore, we did a phase I dose escalation trial of 131I-huA33 radioimmunotherapy. Experimental Designs: Fifteen patients with pretreated metastatic colorectal carcinoma each received two i.v. doses of 131I-huA33. The first was an outpatient trace-labeled "scout" dose for biodistribution assessment, followed by a second "therapy" dose. Three patients were treated at 20, 30, and 40 mCi/m2 dose levels, and six patients at 50 mCi/m2 to define the maximum tolerated dose. Results: Hematologic toxicity was 131I dose-dependent, with one episode of grade 4 neutropenia and two episodes of grade 3 thrombocytopenia observed at 50 mCi/m2. The maximum tolerated dose was determined to be 40 mCi/m2. There were no acute infusion-related adverse events, and gastrointestinal toxicity was not observed despite uptake of 131I-huA33 in bowel. Seven patients developed pruritus or rash, which was not related to 131I dose. There was excellent tumor-targeting of 131I-huA33 shown in all patients. The serum T1/2β of 131I-huA33 was (mean ± SD) 135.2 ± 46.9 hours. The mean absorbed tumor dose was 6.49 ± 2.47 Gy/GBq. Four patients developed human anti-human antibodies. At restaging, 4 patients had stable disease, whereas 11 patients had progressive disease. Conclusion: Radioimmunotherapy using 13lI-huA33 shows promise in targeting colorectal tumors, and is deliverable at a maximum tolerated dose of 40 mCi/m2. Further studies of 131I-huA33 in combination with chemotherapy are planned.

Original languageEnglish
Pages (from-to)4818-4826
Number of pages9
JournalClinical Cancer Research
Issue number13
Publication statusPublished - 1 Jul 2005

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