Effect of monoclonal antibody 17-1A and GM-CSF in patients with advanced colorectal carcinoma--long-lasting, complete remissions can be induced.

Antibody-dependent cellular cytotoxicity (ADCC) is considered to be one of the effector functions of unconjugated monoclonal antibodies (MAbs) in tumor therapy. The antitumor activity of MAbs might therefore be augmented if the cytotoxic capability of the effector cells could be increased. In an in vitro system, the killing capacity of MAb was significantly enhanced by pre-treatment of the effector cells with granulocyte-macrophage colony-stimulating factor (GM-CSF). Based on these findings, the therapeutic effect of the combination of mouse MAb 17-1A (IgG2a) and GM-CSF was evaluated in 20 patients with metastatic colorectal carcinoma (CRC). The patients received GM-CSF for 10 days and a single i.v. infusion of MAb 17-1A on day 3 of the cycle. Four cycles were given at 1-monthly intervals. There was a continuous increase in blood monocytes and lymphocytes during all 4 GM-CSF cycles. Neutrophils and eosinophils were also significantly augmented but in a biphasic manner and the cell counts on day 10 of cycle IV were significantly lower than in cycles I and II. GM-CSF-related side-effects were of no major clinical importance. During the third cycle, an immediate-type allergic reaction (ITAR) against MAb 17-1A occurred in most patients, necessitating reduction of the MAb dose as well as of the infusion rate. Two patients achieved complete remission. One patient had a minor response, and 3 other patients were considered to have stable disease > 3 months.