The chimeric monoclonal anti-GD2 antibody ch14.18 is made up of the variable region of the murine anti-GD2 antibody 14.18 (or its IgG2a switch variant 14G2a) and the constant region of human IgG1k. Ch14.18 mediates antibody dependent cytotoxicity and complement dependent lysis in vitro. In a phase I trial, 13 patients with metastatic melanoma received ch14.18 as a single dose of 5-100 mg. Therapy was associated with an infusion-related abdominal/pelvic pain syndrome, which required intravenous morphine for control. The pharmacokinetics of ch14.18 best fit a two-compartment model with a T1/2 alpha of 24 +/- 1 hr and a T1/2 beta of 181 +/- 73 hr. Eight of 13 patients developed a weak-modest antibody response directed at the variable region of ch14.18. Clinical antitumor responses were not observed at the doses employed in this study. However, patients receiving greater than 45 mg of ch14.18 had antibody detectable on tumor cells analyzed by fluorescent activated cell sorter. Further modification of the therapeutic regime employing larger doses and frequent administration of ch14.18 are planned.