Safety, Pharmacokinetics, and Biological Pharmacodynamics of the Immunocytokine EMD 273066 (huKS-IL2)

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Abstract
This phase 1 clinical trial was conducted to evaluate the safety and to determine the maximum tolerated dose (MTD) of the immunocytokine EMD 273066 huKS-IL2 and, secondarily, to assess its pharmacokinetics, immunogenic potential, and immunologic activity in patients with androgen-independent prostate cancer (n = 22). EMD 273066 was administered in 3-day cycles (separated by 4 weeks) of once-daily, 4-hour intravenous infusions at a dose determined by an escalation protocol (0.4, 0.7, 1.4, 2.8, 4.3, 6.4, or 8.5 mg/m/d). Approximately 2/3 of patients received a second cycle of treatment. The results show that the MTD of EMD 273066 [ie, one dose level below that producing dose-limiting toxicity (DLT) in at least 33% of patients in a dosing group] was 6.4 mg/m/d. EMD 273066 was generally well tolerated up to a dose of 4.3 mg/m/d. No DLTs, defined as drug-related toxicities >OR= Grade 3 occurring during the first treatment cycle, were observed among patients in the 0.4-, 0.7-, 1.4-, or 4.3-mg/m/d dosing groups. Four patients treated with 2.8, 6.4, or 8.5 mg/m/d EMD 273066 experienced DLTs. Titers of both antiimmunocytokine and anti-FcIL-2 antibody responses were observed after the first dose cycle and either decreased or remained stable during a second course of treatment. No hypersensitivity reactions were observed. EMD 273066 exhibited immunologic activity as demonstrated by increases in lymphocyte counts, natural killer cell number and specific activity, and antibody-dependent cellular cytotoxicity activity. On average, Cmax, which was dose-dependent, was achieved within 1 hour after infusion. Mean t(1/2) which was independent of dose, ranged from 4.0 to 6.7 hours across doses. A zero-compartment body model with one-order kinetics best described the concentration-time profiles. These data demonstrate that the novel immunocytokine EMD 273066 is well tolerated at doses above a level of observed systemic biologic activity in patients with androgen-independent prostate cancer.