Abstract 606: Pkm2 activation modulates the tumor-immune microenvironment and enhances response to checkpoint inhibitors in preclinical solid tumor models
Authors: Sommakia Salah , Pathi Satya , Matsumura Yuta , Allred Curtis , Tyagi Ethika , Lalonde Matthew , Foulks Jason , Siddiqui Adam , Whatcott Clifford , Bearss David , Warner Steven 
Published: July 2021

Abstract
Pyruvate kinase is a crucial enzyme responsible for the last step of glycolysis. Cancer cells can use the M2 isoform of pyruvate kinase (PKM2), to better balance respiration and biosynthesis due to allosteric switching between the less active dimeric and fully active tetrameric forms. Additionally, the dimeric form of PKM2 can translocate to the nucleus, altering transcription to enhance cancer cells' ability to grow and evade immune detection. Inducing tetramerization presents an opportunity to target PKM2 resulting in the metabolic reprogramming of tumor-immune microenvironment (TME). TP-1454 is a potent PKM2 activator with low nanomolar PKM2 activation in biochemical assays (AC50 = 10 nM) and multiple cell types (AC &lt; 50 nM), tolerated in mice, rats and dogs after repeat doses as high as 1000 mg/kg/day and has recently entered a Phase I clinical trial (NCT04328740).
We hypothesize that PKM2 activation may reverse the immune-suppressive TME. To test this hypothesis, we examined the activity of TP-1454 combination with immunotherapy (I/O) in multiple mouse syngeneic tumor models. TP-1454 and anti-PD-1 combination therapy in colorectal cancer models resulted in tumor growth inhibition versus vehicle (53% in CT26; 99% in MC38, P &lt; 0.001). We observed decreases in multiple glycolytic intermediates in TP-1454-treated tumors versus vehicle. We conducted immunophenotyping of the TME in multiple models to identify targets of PKM2 activation. TP-1454 treatment reduced the CD4+ Foxp3+ T-regulatory (Treg) population in MC38, 4T1, RENCA models. Further, we assayed TP-1454 induced PKM2 activation in different immune cell types. To confirm the effect of PKM2 activation on Treg cells we conducted an in vitro assay to explore TP-1454 treatment response on polarization of Tregs and/or toxicity and proliferation. We further utilized LCMS to explore metabolic intermediates that play a critical role in Treg regulation, including regulation of the O-linked β-N-acetylglucosamine (O-GlcNac) post-translational modification, which is reported to stabilize Foxp3 in CD4+ cells. We are currently exploring the effect of TP-1454 treatment on O-GlcNac of Foxp3 and its stability in HEK293 cells, to support the link between PKM2 activation and stabilization of Foxp3.
TP-1454 effects on tumor-specific immunity were validated using tumor rechallenge studies. The results of a tumor rechallenge study will be presented using murine MC38 or RENCA xenograft models that are treated with TP-1454 and I/O combination therapies that exhibited a complete response (CR) and were re-implanted.
These preclinical studies indicate a unique mechanism modulating tumor metabolism and the TME to improve the response of cancer patients to immunotherapy.
Citation Format: Salah Sommakia, Satya Pathi, Yuta Matsumura, Curtis Allred, Ethika Tyagi, Matthew Lalonde, Jason Foulks, Adam Siddiqui, Clifford Whatcott, David Bearss, Steven Warner. Pkm2 activation modulates the tumor-immune microenvironment and enhances response to checkpoint inhibitors in preclinical solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 606.