A Dose-Escalation and Signal-Generating Study of the Immunocytokine L19-IL2 in Combination with Dacarbazine for the Therapy of Patients with Metastatic Melanoma

Purpose: L19-IL2 is an immunocytokine composed of an antibody fragment specific to the EDB domain of fibronectin, a tumor angiogenesis marker, and of human interleukin-2 (IL2). L19-IL2 delivers IL2 to the tumor site exploiting the selective expression of EDB on newly formed blood vessels. Previously, the recommended dose of L19-IL2 monotherapy was defined as 22.5 million international units (Mio IU) IL2 equivalents. In this study, safety and clinical activity of L19-IL2 in combination with dacarbazine were assessed in patients with metastatic melanoma. Experimental Design: The first 10 studied patients received escalating doses of L19-IL2 on days 1, 3, and 5 in combination with 1 g/m(2) of dacarbazine on day 1 of a 3-weekly therapy cycle. Subsequently, 22 patients received L19-IL2 at recommended dose plus dacarbazine. Up to six treatment cycles were given, followed by a maintenance regimen with biweekly L19-IL2. Results: The recommended dose of L19-IL2 in combination with dacarbazine was defined as 22.5 Mio IU. Toxicity was manageable and reversible, with no treatment-related deaths. Twenty-nine patients were evaluable for efficacy according to Response Evaluation Criteria in Solid Tumors (RECIST). In a centralized radiology analysis, eight of 29 (28%) patients achieved a RECIST-confirmed objective response, including a complete response still ongoing 21 months after treatment beginning. The 12-month survival rate and median overall survival of the recommended dose-treated patients (n = 26) were 61.5% and 14.1 months, respectively. Conclusions: The repeated administration of L19-IL2 in combination with dacarbazine is safe and shows encouraging signs of clinical activity in patients with metastatic melanoma. This combination therapy is currently evaluated in a randomized phase II trial with patients with metastatic melanoma.