Lactate Dehydrogenase Inhibition to Alter the Tumor Microenvironment and Improve Immune Response in Glioblastoma

Introduction: New treatments for GBM, particularly those that improve response to immunotherapy, are direly needed. Considerable evidence indicates that the tumor microenvironment supports immunosuppression, and lactate dehydrogenase and its product lactate have been identified as important contributors to this process. This study seeks to alter the tumor microenvironment with NCI-006, a novel LDH inhibitor that is both potent and selective and is active against both LDHA and LDHB. Validation of this hypothesis will create opportunities to develop drug combinations (e.g. with existing therapies or immunotherapy) and create a pathway for development of NCI-006 as a drug candidate.

Methods: NCI-006 is studied in vitro and in vivo to assess effect on tumor growth, changes in tumor cell metabolism, and changes the number and type of infiltrating immune cells. In vitro analysis includes cell viability studies, Seahorse analysis of metabolic profile, lactate secretion, T cell activation and migration, quantification of LDH expression via Western blot, and changes in RNA expression after treatment with drug. These studies are done on a syngeneic mouse line (SB28) and human GBM cell lines from our institute. In vivo evaluation is done by implanting SB28 into the brains of C57BL/6 mice, and drug is administered by direct intratumoral infusion. Tumors are harvested for flow cytometry, immunofluorescence, and RNA sequencing.

Results: NCI-006 demonstrates modest inhibition of cell growth in both human and murine cell lines. More importantly, the drug inhibits lactate and acid secretion at physiologically relevant concentrations. Results from RNA sequencing from in vitro culture with and without drug are pending. The syngeneic mouse model has been established and mice are tolerating treatment with drug.

Conclusion : NCI-006 demonstrates potent remodeling of GBM cell metabolism in vitro and supports the in vivo studies which are ongoing. Results are pending from these studies are pending. Combination studies are planned.