Abstract 4744: Soluble, high affinity TCRs fused to anti-CD3 redirect T cells to kill cancer cells presenting MAGE-A3 and NY-ESO antigens

Abstract

Abstract In the last decade, major efforts in the fight against cancer have focused on galvanizing the adaptive immune system to kill tumors. Many of these endeavors are based on the development and clinical use of monoclonal antibodies (mAb) which are the most successful class of immune modulating agent identified to date. While mAbs show promise against certain cancers, their specificity is limited to integral membrane proteins; this hinders their extensive development for the purposes of targeting cancer cells. In contrast to mAbs, T cell receptors (TCRs) recognize peptides bound to major histocompatibility complex class I (MHC I) molecules. These peptides are derived from endogenously processed proteins, and therefore represent a different repertoire of targets to those recognized by mAbs. This alternate spectrum of antigens provides the potential to target cancers using an untapped source of well-validated epitopes. Naturally occurring TCRs, however, have relatively low affinities for their antigen compared to antibody binding. Advances in engineering techniques have allowed the generation of high affinity monoclonal TCRs (mTCRs) with picomolar affinities for their antigen. Using targeted mutagenesis and phage display, we have generated a number of soluble, high affinity mTCRs specific for several reported tumor-associated antigens. Through mTCR fusion to an anti-CD3 single chain variable fragment (scfv), we produced bifunctional proteins that redirect T cell immune specificity. These novel proteins are termed ImmTACs (Immune-mobilizing mTCRs Against Cancer). We present data showing the potential of two such ImmTACs, NY-ESO-ImmTAC and MAGE-A3-ImmTAC, to treat certain cancers. NY-ESO1 and MAGE-A3 are cancer testes antigens and therefore represent potentially very clean molecular targets. We demonstrate that both NY-ESO- and MAGE-A3-ImmTACs are capable of potently redirecting unstimulated CD8+ T cells against multiple myeloma, colorectal carcinoma and non-small cell lung cancer cell lines despite the presentation of extremely low antigen numbers (<100 epitopes/cell) on the cell surface. ImmTAC-redirected T cells respond with multiple effector functions including production of granzyme B, IFNγ and IL-2. Using the NY-ESO-ImmTAC we observed significant redirected degranulation of T cells against a primary lung tumor sample which was shown to express NY-ESO. We also present data from an established tumor model using the OV-79 cell line derived from an ovarian tumor which is shown to express MAGE. Administration of MAGE-A3-ImmTAC to animals with established tumors resulted in inhibition of tumor growth in all ImmTAC treated animals with regression or cure in some. Thus both MAGE-A3 and NY-ESO-ImmTACs possess the potential to be highly specific, potent cancer immunotherapies offering a targeting and therapeutic approach distinct from any other biologic in development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4744. doi:10.1158/1538-7445.AM2011-4744