Modification of the tumor microenvironment (TME) to promote immune-mediated tumor cell destruction is considered to be an essential step for effective immunotherapy. We are evaluating recombinant live-attenuated, double deleted Listeria monocytogenes (LADD) as an immunotherapy platform for the treatment of cancer in several clinical trials in diverse indications. One LADD strain, known as CRS-207, has been engineered to express the tumor-associated antigen mesothelin and is being tested in pancreatic, ovarian and mesothelioma malignancies. Using multi-dimensional immunohistochemistry of paired biopsies from three patients with mesothelioma, we demonstrate the recruitment and expansion of effector tumor-infiltrating lymphocytes, including CD8+ T cells, mature DCs, CD163 macrophages and NK cells, following two prime infusions of CRS-207. In several different syngeneic mouse tumor models, we demonstrate that treatment with LADD engineered to express endogenous tumor antigens also induced significant changes in the TME that were consistent with changes observed in cancer patients, including enhanced CD8+ T cell effector function, recruitment of critical antigen presenting cells and reduction of regulatory T cells, and these changes correlated with significant therapeutic benefit in the mouse. LADD-induced changes to the TME were required for synergistic therapeutic antitumor efficacy combined with immune checkpoint blockade, including targeting MC38 tumor-specific neoantigens. Together, these findings demonstrate that intravenous administration of recombinant LADD therapy induces favorable changes in the tumor microenvironment in mice and humans with promise for effective outcomes in human clinical trials.

Citation Format: Weiwen Deng, Takahiro Tsujikawa, Nitya Nair, Thomas Hudson, Weiqun Liu, Chris S. Rae, Edward E. Lemmens, Anthony W. Desbien, William Hanson, Peter Lauer, Lisa M. Coussens, Dirk G. Brockstedt, Thomas W. Dubensky, Jr., Meredith L. Leong. Favorable changes in tumor microenvironment following intravenous dosing with live attenuated Listeria monocytogenes-based immunotherapy [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A013.