A Dose-Escalation and Pharmacokinetic Study of Subcutaneously Administered Recombinant Human Interleukin 12 and Its Biological Effects in Japanese Patients with Advanced Malignancies

A pilot dose-escalation study of recombinant human interleukin 12 (rhIL-12) was conducted in Japanese patients with advanced malignancies. Cohorts of three patients received escalating doses of rhIL-12 that increased from 50 to 300 ng/kg/day s.c. three times a week for 2 weeks followed by 1-week rest. The same dosage and schedule was repeated for two additional courses. Sixteen previously treated patients were registered, and 15 were evaluated. Common toxicities were fever and leukopenia; the abnormality of laboratory tests included elevations in aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, C-reactive protein, and β2-microglobrin. Dose-limiting toxicity was the grade 3 elevation of aminotransferases, and was observed in two of six patients at the 300-ng/kg dose level after the first course in one patient and after the third course in the other. Leukopenia was observed at all of the dose levels; two of six patients at 300 ng/kg experienced grade 3 leukopenia. Thus, 300 ng/kg was determined to be the maximum acceptable dose. Peak plasma levels of rhIL-12 decreased in the second courses, but the areas under the curve were almost the same in the first and second courses. Biological effects included increases of plasma levels of IFN-γ, tumor necrosis factor-α, IL-6, IL-10, and neopterin. In two patients with renal cell carcinoma, complete response and partial response of metastatic tumors were observed with 50 and 300 ng/kg; the responses lasted for 5 and 3.5 months, respectively. Although immunological response to rhIL-12 varies depending on administration route and schedule and on patients’ physiological conditions, the recommended dose for Phase II studies is 300 ng/kg s.c. three times a week for 2 weeks followed by 1-week rest.