Low-dose monoclonal antibody CC49 administered sequentially with granulocyte-macrophage colony-stimulating factor in...

The clinical and immunologic effects of murine monoclonal antibody (mAb) CC49 administered at a low dose sequentially with granulocyte-macrophage colony-stimulating factor (GM-CSF) were examined. Fourteen patients with metastatic colorectal cancer received 1 mg of unconjugated CC49 on day 1; on day 15 they began 125 micrograms/m2 GM-CSF by subcutaneous injection daily for 14 days, followed by 7 days of rest. Another 14 days of GM-CSF were then administered, followed by 7 days of rest. This 56-day cycle was repeated in patients whose cancer did not progress. Therapy was well tolerated; adverse allergic reactions were not observed. Objective tumor responses were not observed. Increases in antiidiotypic (T2) and anti-antiidiotypic (T3) cellular responses were observed, as were increases in human antimouse antibody levels. In contrast, the expression of Fc receptors on CD14+ peripheral blood monocytes decreased. This pilot study demonstrates idiotypic cellular immunologic effects of antitumor murine mAb, even at the doses used for imaging, and supports the sequential administration of GM-CSF as an adjuvant to mAb-based immunogens.