Introduction: MDX-447 is a bispecific antibody directed against the epidermal growth factor receptor (EGFR) and the high affinity Fc receptor (FcgammaRI). Preclinical data suggest that co-administration of granulocyte-colony stimulating factor (G-CSF) may enhance the tumor cytotoxicity of bispecific antibodies.
Methods: In group 1, patients received MDX-447 intravenously (i.v.) weekly. Dose levels of MDX-447 evaluated in group 1 were 1, 3.5, 7, 10, 15, 20, 30, and 40 mg/m(2). In group 2, patients received MDX-447 IV weekly with G-CSF (3 mcg/kg/day) subcutaneously (days -3 to +2, 5-9, 12-16, etc.). Dose levels of MDX-447 evaluated in group 2 were 1, 3.5, 7, 10, and 15 mg/m(2).
Results: Sixty-four patients with advanced solid tumors were treated. Forty-one patients received MDX-447 alone (group 1); 23 patients received MDX-447 + G-CSF (group 2). Hypotension was the predominant dose-limiting toxicity (DLT) in both treatment groups, with seven patients experiencing >or= grade 3 events. MDX-447 half-life (T(1/2)) ranged from 1.9 to 8.4 h, with no obvious differences between the two treatment groups. MDX-447 binding to neutrophils and peak levels of circulating tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) were higher in group 2. The MTD for MDX-447 alone was 30 mg/m(2). When G-CSF was given with MDX-447, treatment was not well tolerated and group 2 was closed early because of safety concerns, with the last patient being treated at the 7 mg/m(2) dose level. There were no objective complete or partial responses in either group.
Conclusion: MDX-447 alone was generally well tolerated, but did not achieve objective tumor responses. The MTD for MDX-447 alone was 30 mg/m(2) weekly. Co-administration of G-CSF with MDX-447 precluded meaningful dose escalation.