Abstract A079: Glutamine antagonist prodrug JHU083 reprograms immunosuppressive tumor-associated macrophages to drive tumor immunity in urologic cancers (2023)

Abstract Tumor metabolism is emerging as a regulator of immune mediated anti-tumor responses. Previously, we reported increased immunosuppressive tumor-associated macrophages (TAMs) infiltration with disease progression in prostate adenocarcinoma (PCa).1 Glutamine metabolism has been implicated in metastatic castration resistant prostate cancer (mCRPC)2. To harness the potent anti-tumor effects of 6-Diazo-5-oxo-L-norleucine (DON), which targets glutamine utilizing enzymes and to mitigate known significant toxicities, we here use a novel pro-drug moiety, i.e., JHU083. We hypothesize that JHU083 will enhance anti-tumor immunity by simultaneously targeting TAMs and cancer cells. Using scRNA-seq dataset from mCRPC patients, we investigated the importance of glutamine metabolism in TAMs in the tumors.3 Enriched expression of glutamine utilizing enzymes was observed in TAMs in the metastasized tumor tissue relative to benign. We used JHU083 to treat two urological syngeneic immunogenic mouse tumor models in vivo; B6CaP (PCa) and MB49 (bladder cancer). JHU083 showed significant tumor regression in both models. Using in vivo depletion of CD4 or CD8 T cells or adoptively transferring in-vivo JHU083 treated TAMs in TME, we established a direct anti-tumor role of TAMs. Moreover, to characterize the effect of JHU083 on TAMs transcriptional, translational signatures and metabolite flux in vivo, we used scRNA-sequencing and bulk RNA sequencing at two different time points, multi-parameter flow cytometry and targeted LC-MS/MS metabolic profiling. Clustering of the transcriptional signatures at both time points using UMAP dimensionality reduction classified 6 discreet differentially expressed clusters of TAMs. It elutes to an overall induction of TNF signaling and increased proliferation in the TAM sub-clusters. Strikingly, this was observed translationally as well. Moreover, translationally in the TME at a later timepoint, an increase of glycolytic transporter and enzyme, i.e., Glut1 and Hexokinase II was also observed. The overall impact of this on the metabolome, specifically glycolytic pathway changes in the sorted TAMs, remains to be elucidated. Lastly, we assessed in-vivo the functional phagocytosis of TAMs with flow cytometry and IF microscopy. JHU083-treated TAMs showed significantly increased phagocytic activity, providing direct evidence of functional reprogramming. Conclusions: We found that JHU083 reprograms TAMs from an immunosuppressive to an inflammatory state which we show has a direct anti-tumor effect. These macrophages convert to a highly proliferative and glycolytic state, have increased TNF production which might be resulting in improved phagocytic activity against tumor cells. As urologic cancers are heavily infiltrated with immunosuppressive TAMs, JHU083 is an excellent preclinical candidate. Citation Format: Monali Praharaj, Fan Shen, Alex J. Lee, Liang Zhao, Thomas R. Nirschl, Xiaoxu Wang, Debebe Theodros, Alok K. Singh, Raekwon A. Williams, Laura A. Sena, Elizabeth A. Thompson, Ada Tam, Srinivasan Yegnasubramanian, Edward J. Pearce, Robert D. Leone, Jesse Alt, Rana Rais, Barbara S. Slusher, Drew M. Pardoll, Jonathan D. Powell, Jelani C. Zarif. Glutamine antagonist prodrug JHU083 reprograms immunosuppressive tumor-associated macrophages to drive tumor immunity in urologic cancers [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A079.