Immunization of cutaneous melanoma patients with the allogeneic cell vaccine CSF-470 enhances immune infiltration of metastatic lesions and would favor subsequent response to Vemurafenib

ARIS, MARIANA; PAMPENA, MARIA BETINA; LEVY, ESTRELLA MARIEL; BRAVO, ALICIA INES; MADORSKY ROWDO, FLORENCIA PAULA; MORDOH, ANA; KAPLAN, JULIO; BARON, ANTONELA; URRUTIA, MARIELA; BLANCO, PAULA ALEJANDRA; BARRIO, MARIA MARCELA; MORDOH, JOSE

Orlando

Congreso; Tumor Immunology and Immunotherapy: A New Chapter; 2014

Therapeutic cancer vaccines are aimed at promoting tumor-specific immunity with long-term memory. We have developed the CSF-470 therapeutic vaccine, a mini-allograft of four irradiated allogeneic cutaneous melanoma cell lines, combined with BCG and hrGM-CSF as adjuvants; that it is currently being assayed in adjuvancy against medium-dose IFN-alpha2b in the CASVAC-0401 phase II/III clinical trial(ClinicalTrials.gov identifier: NCT01729663). An update to September 2014 reveals that after inclusion of 31 patients, a significant benefit in the distant metastasis-free survival for the CSF-470 arm is obtained (p=0.034). Of the 20 patients asigned to the CSF-470 arm, with a mean follow-up of 26 months, six patients developed distant metastases, of whom two died, and fourteen patients are distant metastases-free (70%). Five patients of the vaccine arm were treated with Vemurafenib after progression; two of them achieved complete remission and two of them partial remission (>50%); only one developed severe dermatitis. Before Vemurafenib treatment, metastases biopsies from only three patients could be obtained; two of them later achieved complete responses. In this work, we present the analysis of the peripheral blood and in situ immune populations during CSF-470 immunization in the two patients that achieved complete responses with Vemurafenib treatment. To attain this task, histophatological characterization of tumor biopsies, along with immune populations determined by immunohistochemistry, was performed by microscopy and image analysis. Peripheral blood mononucleated cells were obtained from patients at different times during CSF-470 immunization and immune populations were assessed by flow cytometry. Patient #006 entered CASVAC-0401 study after a primary and lymph node tumor resection. By the end of CFS-470 immunization, she developed simultaneously subcutaneous and lung metastases. Following a 3-month cycle of Vemurafenib 960mg bid, patient #006 achieved complete remission of lung tumor nodules. Analysis of immune response evolution during protocol revealed a marked increase in in situ immune infiltration at the cutaneous metastasis relative to the primary tumor, especially in CD8+, CD4+ and CD20+ cells. Several dying tumor cells could be distinguished in the cutaneous metastasis, with attached and surrounding CD8+, CD4+ and CD45Ro+ T lymphocytes and CD68+ cells; and with granzyme B vesicles and DNA strand breaks. Patient #005 developed sequential in transit metastases; CD8+, CD4+ and CD20+ lymphocyte infiltration increased in situ in biopsies following CSF-470 immunization. Vemurafenib treatment allowed achieving a complete response characterized by brisk infiltration of CD68+ macrophages, CD11c+ dendritic cells, CD8+ and CD4+ lymphocytes. In both patients, analysis of peripheral immune populations revealed an increment in NK cells detected after 6-months treatment, followed by an increase in CD4+ and CD8+ cells by the end of the protocol (2 years). Also, serum reactivity to CSF-470 cutaneous melanoma cells increased during vaccination. We suggest that previous immunization of melanoma patients with CSF-470 vaccine increases tumor immune infiltration and subsequent response to Vemurafenib. These encouraging results may open new options for combined therapies in cutaneous melanoma.