Abstract CT219: Phase I trial of in situ vaccination with autologous CCL21 gene-modified dendritic cells (CCL21-DC) combined with pembrolizumab for advanced non-small cell lung cancer (NSCLC)

Abstract Background: Although immune checkpoint blockade (ICB) targeting Programmed Death-1/Programmed Death-Ligand 1 (PD-1/PD-L1) alone or in combination with chemotherapy is now a first-line option for patients with advanced NSCLC, the majority of patients do not benefit from anti-PD-1/PD-L1 monotherapy, and the combination with chemotherapy is often associated with toxicity. For patients who initially respond to PD-1/PD-L1 inhibition, many relapse after an initial response and are in need for innovative strategies to overcome the resistance to ICB. One possible approach is to utilize in situ vaccination with functional chemokine gene-modified antigen presenting cells (APCs) that take advantage of the full repertoire of tumor antigens in the tumor microenvironment (TME) in order to restore tumor antigen presentation, promote tumor infiltration of immune cells driven by chemokine gradient, and facilitate tumor-specific T cell activation, both locally and systemically. The chemokine CCL21 is a therapeutic candidate due to its ability to promote infiltration and co-localization of naïve T cells and antigen-experienced dendritic cells (DCs) and facilitate T cell activation. In preclinical studies as well as a phase I clinical trial, we observed that intratumoral (IT) injection of CCL21-DC induces the infiltration of autologous DC and T cells into the TME, and generates systemic tumor-specific immune responses against multiple tumor antigens. We also observed tumoral PD-L1 upregulation following CCL21-DC injection, which may hinder T cell function. Similarly, the lack of efficacy of PD-1/PD-L1 inhibitors could potentially be combated by enhanced T cell infiltration and augmented APC function in the TME following in situ vaccination with CCL21-DC. Therefore, we are currently evaluating the safety and efficacy of combining IT CCL21-DC and intravenous (IV) pembrolizumab in advanced NSCLC patients following progression on ICB or tyrosine kinase inhibitor (TKI) therapy in a phase I trial (NCT03546361). Methods: Phase I, dose-escalating, multi-cohort trial followed by dose expansion. Maximum of 24 patients (9-12 escalation + 12 expansion) with stage IV NSCLC will be evaluated who have tumors accessible for IT injection and are either EGFR/ALK wild-type after progression on a PD-(L)1 inhibitor or EGFR/ALK mutant after progression on TKI. Three IT injections of autologous CCL21-DC (days 0, 21, 42) will be concurrently administered with pembrolizumab, followed by q3wk pembrolizumab up to 1 year. Primary objective of dose escalation is safety and determination of maximum tolerated dose (MTD) of IT CCL21-DC when combined with pembrolizumab. Primary objective of dose expansion is objective response rate at MTD. Secondary objectives include adverse event profiling and immune monitoring studies. [B.L. and A.L. contributed equally to this work as first authors.] Citation Format: Bin Liu, Aaron Lisberg, Ramin Salehi-Rad, Jay Lee, Linh M. Tran, Kostyantyn Krysan, Raymond Lim, Camelia Dumitras, Zhe Jing, Michael Oh, Fereidoun Abtin, Robert Suh, Scott Genshaft, Scott Oh, Gregory Fishbein, Ciara M. O'Higgins, Anita Kaul, Kanwarpal Kahlon, Shahryar Ashouri, Jonathan Goldman, David Elashoff, Edward Garon, Steven Dubinett. Phase I trial of in situ vaccination with autologous CCL21 gene-modified dendritic cells (CCL21-DC) combined with pembrolizumab for advanced non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT219.