Virtual Library
Start Your Search
V. Nguyen
Author of
-
+
ORAL 41 - Immune Biology, Microenvironment and Novel Targets (ID 159)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:S.K. Padda, R. Nemenoff
- Coordinates: 9/09/2015, 18:30 - 20:00, Four Seasons Ballroom F1+F2
-
+
ORAL41.05 - Targeting Phosphatidylserine-Mediated Immune Suppression Enhances the Efficacy of Immune Checkpoint Blockade in Pre-Clinical Tumor Models (ID 1011)
19:13 - 19:24 | Author(s): V. Nguyen
- Abstract
- Presentation
Background:
Despite substantial progress, only a subset of cancer patients benefit from blockade of the PD-1 immune checkpoint. Multifocal immune suppression in the tumor microenvironment is the underlying cause for the limited efficacy of immune checkpoint blockade. Persistent immune suppression prevents the development of a robust T cell response to tumor specific antigens that is required for effective downstream immune checkpoint blockade. An underappreciated but significant contributor to immune suppression in tumors is the expression of the membrane phospholipid phosphatidylserine (PS) on the surface of tumor cells and tumor-derived microvesicles. PS is recognized by receptors on immune cells where it triggers the secretion of immune suppressive cytokines, prevents the differentiation of myeloid-derived suppressor cells (MDSCs) and inhibits dendritic cell (DC) maturation; events that prevent a productive anti-tumor T cell response. Bavituximab, a chimeric monoclonal antibody that targets PS and inhibits PS-mediated immunosuppressive signaling, drives immune activation by reducing the levels of MDSCs, by polarizing tumor-associated macrophages towards an M1 phenotype and by promoting the maturation of dendritic cells (DCs).
Methods:
The efficacy of bavituximab, anti-PD-1 and combination therapy was evaluated in multiple syngeneic, pre-clinical tumor models. Treatment efficacy was determined by inhibition of tumor growth and by immunophenotyping of spleen and tumor infiltrating leukocytes.
Results:
The combination of antibody-mediated PS and PD-1 blockade was significantly more effective in reducing tumor burden and promoting immune activation than single agent therapy. Combination therapy increased tumor infiltration of effector T-cells (Teff), increased the Teff:T regulatory cell ratio in the tumor and enhanced Teff function as determined by IFN-γ, TNFα and granzyme B levels associated with Teff cells in the spleen and tumor. Furthermore combined blockade of PS and PD-1 signaling reduced the level of immune suppressive cells (e.g., MDSCs, M2 macrophages, and Treg) in the tumor microenvironment.
Conclusion:
These results raise the possibility that PS blockade with bavituximab can enhance the efficacy of anti-PD-1 therapy even in patients with tumors that are unresponsive to single agent immune checkpoint therapy.
Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
