Abstract 5553: A novel immunocytokine for the treatment of cancer

Interleukin-12 (IL12) is an immunomodulatory cytokine, which offers unique opportunities for cancer therapy due to its stimulatory function on cell-mediated immunity and its anti-angiogenic activity. IL12 was shown to polarize CD4+ T cells into a TH1 type and to be a key activator of NK cells and CD8+ T cells. It also induces the production of interferon-gamma by T cells and NK cells and subsequently of the anti-angiogenic chemokines CXCL10/IP-10, and CXCL9/Mig. However the potent anti-tumor IL12 activity, which has been reported in mice, has not yet been successfully translated into clinical development, mainly because of early reports of severe toxicity and low response rates in human. Following our pioneering work which started in 2002 with the first description of an IL12 based antibody-cytokine fusion protein (i.e. Immunocytokine), we have extensively explored and perfected alternative molecular formats, with the aim to further improve biodistribution properties and therapeutic activity of IL12-based immunocytokines. Here we describe the development and evaluation of new targeted variants of both murine and human IL-12 with enhanced therapeutic efficacy and improved safety profile. To this end we combined the immunomodulatory properties of the IL12 payload with the tumor-homing activity of the L19 antibody. L19 is a clinical grade fully human antibody, which recognizes with identical affinity in both mouse and human, the alternatively spliced EDB domain of fibronectin. EDB represent an optimal target for anti-cancer pharmacodelivery, due to its pan-tumoral over-expression nature combined with very low expression levels in normal tissues. This has also been confirmed by extensive Nuclear Medicine work in which radiolabeled L19 has been administered to more than 150 patients, making L19 one of the best validated tumor-targeting agent. Our novel immunocytokine, termed IL12-L19-L19, relies on the L19 antibody in tandem diabody format, with a monomeric IL12 moiety expressed as single-chain polypeptide at the N-terminal extremity. Recombinant IL12-L19-L19 proteins based either on human or murine IL12, were efficiently expressed in CHO cells and purified to high quality. The tumor-targeting properties of both variants were validated in tumor-bearing mice, using radioiodinated protein preparations. In preclinical therapy studies IL12-L19-L19 showed potent anti-cancer activity when used either as single agent or in combination with other anticancer agents. PK studies in Cynomolgus Monkey using the fully human IL12-L19-IL19 product, revealed a favorable profile, which is compatible with other clinical-stage immunocytokines based on antibody-fragments. These results strongly support the further development of the fully human IL12-L19-L19 product for future clinical investigations. Citation Format: Mattia Matasci, Emanuele Puca, Tiziano Ongaro, Sarah Wulhfard, Alessandra Villa, Dario Neri. A novel immunocytokine for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5553.