Background: EMD 521873 (Selectikine), an immunocytokine comprising a DNA-targeting antibody, aimed at tumour necrosis, fused with a genetically modified interleukin-2 (IL-2) moiety, was investigated in this first-in-human phase I study.
Methods: Patients had metastatic or locally advanced solid tumours failing previous standard therapy. Selectikine was administered as a 1-hour intravenous infusion on 3 consecutive days, every 3 weeks. A subgroup of patients also received 300 mg/m(2) cyclophosphamide on day 1 of each cycle. Escalating doses of Selectikine were investigated with the primary objective of determining the maximum tolerated dose (MTD).
Results: Thirty-nine patients were treated with Selectikine alone at dose levels from 0.075 to 0.9 mg/kg, and nine were treated at doses of 0.45 and 0.6 mg/kg in combination with cyclophosphamide. A dose-dependent linear increase of peak serum concentrations and area under curve was found. The dose-limiting toxicity was grade 3 skin rash at the 0.9 mg/kg dose-level; the MTD was 0.6 mg/kg. Rash and flu-like symptoms were the most frequent side-effects. No severe cardiovascular side-effects (hypotension or vascular leak) were observed. At all dose-levels, transient increases in total lymphocyte, eosinophil and monocyte counts were recorded. No objective tumour responses, but long periods of disease stabilisation were observed. Transient and non-neutralising Selectikine antibodies were detected in 69% of patients.
Conclusions: The MTD of Selectikine with or without cyclophosphamide administered under this schedule was 0.6 mg/kg. The recommended phase II dose was 0.45-0.6 mg/kg. Selectikine had a favourable safety profile and induced biological effects typical for IL-2.
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