Abstract B056: DLL3 CAR-T and CAR-NK cell combination therapy promotes synergistic antitumor activity in small cell lung cancer
TL;DR
The results suggest that DLL3-targeting CAR therapies represent a promising approach for treating SCLC, particularly given their ability to function independently of MHC-I, and a combination of CAR-T and CAR-NKs could be an efficacious approach to overcoming current limitations of CAR therapies in solid tumors.
Abstract
Small cell lung cancer (SCLC) is an aggressive form of lung cancer, with most patients showing poor response rates to immunotherapies, resulting in limited treatment options. Profiling of the SCLC TIME shows immunologic heterogeneity, with the majority of SCLC being neuroendocrine (NE) subtype and exhibiting low MHC-I expression, and a minority being non-neuroendocrine (non-NE) subtype, with higher MHC-I expression. Recent incorporation of T cell engagers targeting DLL3 and CD3 have shown promising results, however, MHC-I downregulation can potentially limit endogenous T cell activity and therapeutic responses. Chimeric antigen receptor (CAR) based therapies enable the genetic engineering of T or NK cells to target tumor-specific antigens independently of MHC-I, representing a promising therapeutic strategy for SCLC. However, CAR-NK cells’ proliferation and lifespan is limited compared to CAR-T cells. CAR-T might benefit from a combination with CAR-NK providing a rapid antitumor response to promote infiltration and expansion. In this study we aimed to use 3D micro-physiological systems to test whether a combination of CAR-T and CAR-NK could overcome CAR therapy limitations in solid tumors. DLL3 surface protein expression was characterized in SCLC cell lines by flow cytometry. Then, DLL3-targeting CAR-T and CAR-NK cells were generated through viral transduction and validated in both 2D and 3D tumor models. The combination of the CAR-T and CAR-NK was tested using a co-culture spheroids model in a 3D microfluidic device. Finally, infiltration of the CARs across a blood vessel barrier into the TME was investigated by creating a microphysiological system of SCLC TME. We found that DLL3 expression was heterogenous across SCLC cell lines, with NE SCLC exhibiting higher DLL3 expression than non-NE SCLC. Both DLL3 CAR-T and CAR-NK cells demonstrated potent antitumor activity in 2D and 3D culture, with CAR-NK cells showing more rapid cytotoxic activity compared to CAR-T cells, killing via antigen recognition but also recognizing the absence of MHC-I expression. We then sought to combine both therapies to investigate cooperative activity between the two effector-cell platforms. At a 6-day timepoint, without exogenous IL-2 stimulation, we found that the DLL3 CAR-T and CAR-NK cell combination showed the greatest anti-tumor activity in the DLL3+ NE cell lines, compared to either therapy alone when tested in the 3D microfluidic model, suggesting synergistic and bystander effector function. These results correlated with higher IL-2 and IFN-g production detected in conditioned media only in the CAR-T and CAR-NK cell combination treatment. These results suggest that DLL3-targeting CAR therapies represent a promising approach for treating SCLC, particularly given their ability to function independently of MHC-I. In addition, a combination of CAR-T and CAR-NKs could be an efficacious approach to overcoming current limitations of CAR therapies in solid tumors, including immune cell exclusion, persistence, and exhaustion. Alan E. Bers, Ian Gillanders, Eden Bobilev, Carla Stornante, Mubin Tarannum, Navin R. Mahadevan, Rizwan Romee, Marco Campisi, David A. Barbie. DLL3 CAR-T and CAR-NK cell combination therapy promotes synergistic antitumor activity in small cell lung cancer [abstract]. In: Proceedings of AACR Drug Discovery and Development (AACR D3) Conference; 2026 Jul 21-24; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(14_Suppl):Abstract nr B056.