Immunotherapy for recurrent colorectal cancers with human monoclonal antibody SK-1.

BACKGROUND: The human monoclonal antibody SK-1 recognizes a glycoprotein expressed on the majority of colon cancer tissues. In the current study, we evaluated the safety, toxicity and preliminary efficacy of escalating dosages of SK-1 in patients with advanced colon cancer. PATIENTS AND METHODS: SK-1 was administered intravenously at 2, 4 or 10 mg three times to three groups of patients with recurrent colon cancer. The clinical outcome and the induction of serum anti-idiotypic antibody (Ab2) were assessed periodically. RESULTS: The mean rate of serum CEA level increase declined significantly during the eight weeks following the treatment. In four patients, serum titer of anti-idiotypic IgG antibodies to SK-1 (Ab2) continued to increase following the treatment. CONCLUSION: HuMAb SK-1 was well-tolerated and can be safely administered. It was suggested that SK-1 natural antibody not only possessed direct cytostatic activity against colon carcinoma, but may also have induced carcinoma-related, anti-idiotypic antibody responses.