The generation and analyses of a novel combination of recombinant adenovirus vaccines targeting three tumor antigens as an immunotherapeutic

// Elizabeth S. Gabitzsch 1 , Kwong Yok Tsang 2 , Claudia Palena 2 , Justin M. David 2 , Massimo Fantini 2 , Anna Kwilas 2 , Adrian E. Rice 1 , Yvette Latchman 1 , James W. Hodge 2 , James L. Gulley 3 , Ravi A. Madan 3 , Christopher R. Heery 2 , Joseph P. Balint Jr. 1 , Frank R. Jones 1, * , Jeffrey Schlom 2, * 1 Etubics Corporation, Seattle, WA, USA 2 Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA 3 Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA * These authors have contributed equally to this work Correspondence to: Jeffrey Schlom, e-mail: js141c@nih.gov Keywords: cancer vaccines, adenovirus vaccines, tumor antigens, immunotherapy, brachyury Received: June 18, 2015      Accepted: August 24, 2015      Published: September 07, 2015 ABSTRACT Phenotypic heterogeneity of human carcinoma lesions, including heterogeneity in expression of tumor-associated antigens (TAAs), is a well-established phenomenon. Carcinoembryonic antigen (CEA), MUC1, and brachyury are diverse TAAs, each of which is expressed on a wide range of human tumors. We have previously reported on a novel adenovirus serotype 5 (Ad5) vector gene delivery platform (Ad5 [E1-, E2b-]) in which regions of the early 1 (E1), early 2 (E2b), and early 3 (E3) genes have been deleted. The unique deletions in this platform result in a dramatic decrease in late gene expression, leading to a marked reduction in host immune response to the vector. Ad5 [E1-, E2b-]-CEA vaccine (ETBX-011) has been employed in clinical studies as an active vaccine to induce immune responses to CEA in metastatic colorectal cancer patients. We report here the development of novel recombinant Ad5 [E1-, E2b-]-brachyury and-MUC1 vaccine constructs, each capable of activating antigen-specific human T cells in vitro and inducing antigen-specific CD4 + and CD8 + T cells in vaccinated mice. We also describe the use of a combination of the three vaccines (designated Tri-Ad5) of Ad5 [E1-, E2b-]-CEA, Ad5 [E1-, E2b-]-brachyury and Ad5 [E1-, E2b-]-MUC1, and demonstrate that there is minimal to no “antigenic competition” in in vitro studies of human dendritic cells, or in murine vaccination studies. The studies reported herein support the rationale for the application of Tri-Ad5 as a therapeutic modality to induce immune responses to a diverse range of human TAAs for potential clinical studies.