Comparison of serum IFN-γ concentrations in patients in the Phase 1 and Phase 2 studies. Serum IFN-γ concentrations were determined for 12 patients receiving 500 ng/kg rhIL-12 intravenously daily for 5 consecutive days in the Phase 1 study (▨) and for 10 patients who were scheduled to receive rhIL-12 at 500 ng/kg intravenously for 5 consecutive days in the Phase 2 study (▪). Serum samples were obtained immediately before the first dose and daily before subsequent rhIL-12 administration. The number of patients in the Phase 2 study receiving 2, 3, 4, or 5 days of rhIL-12 treatment were 1, 10, 2, and 4, respectively. BDL, below detectable levels.