MTA-cooperative PRMT5 inhibitors enhance T cell-mediated antitumor activity in MTAP-loss tumors

Si Chen, Jiakai Hou, Roshni Jaffery, Ashley Guerrero, Rongjie Fu, Leilei Shi, Ningbo Zheng, Ritu Bohat, Nicholas A. Egan, Chengtai Yu, Sana Sharif, Yue Lu, Wei He, Shuyue Wang, Donjeta Gjuka, Everett M. Stone, Pooja Anil Shah, Jordi Rodon Ahnert, Taiping Chen, Xinli LiuMark T. Bedford, Han Xu, Weiyi Peng

Research output: Contribution to journalArticlepeer-review

Abstract

BACKGROUND: Hyperactivated protein arginine methyltransferases (PRMTs) are implicated in human cancers. Inhibiting tumor intrinsic PRMT5 was reported to potentiate antitumor immune responses, highlighting the possibility of combining PRMT5 inhibitors (PRMT5i) with cancer immunotherapy. However, global suppression of PRMT5 activity impairs the effector functions of immune cells. Here, we sought to identify strategies to specifically inhibit PRMT5 activity in tumor tissues and develop effective PRMT5i-based immuno-oncology (IO) combinations for cancer treatment, particularly for methylthioadenosine phosphorylase (MTAP)-loss cancer. METHODS: Isogeneic tumor lines with and without MTAP loss were generated by CRISPR/Cas9 knockout. The effects of two PRMT5 inhibitors (GSK3326595 and MRTX1719) were evaluated in these isogenic tumor lines and T cells in vitro and in vivo. Transcriptomic and proteomic changes in tumors and T cells were characterized in response to PRMT5i treatment. Furthermore, the efficacy of MRTX1719 in combination with immune checkpoint blockade was assessed in two syngeneic murine models with MTAP-loss tumor. RESULTS: GSK3326595 significantly suppresses PRMT5 activity in tumors and T cells regardless of the MTAP status. However, MRTX1719, a methylthioadenosine-cooperative PRMT5 inhibitor, exhibits tumor-specific PRMT5 inhibition in MTAP-loss tumors with limited immunosuppressive effects. Mechanistically, transcriptomic and proteomic profiling analysis reveals that MRTX1719 successfully reduces the activation of the PI3K pathway, a well-documented immune-resistant pathway. It highlights the potential of MRTX1719 to overcome immune resistance in MTAP-loss tumors. In addition, MRTX1719 sensitizes MTAP-loss tumor cells to the killing of tumor-reactive T cells. Combining MRTX1719 and anti-PD-1 leads to superior antitumor activity in mice bearing MTAP-loss tumors. CONCLUSION: Collectively, our results provide a strong rationale and mechanistic insights for the clinical development of MRTX1719-based IO combinations in MTAP-loss tumors.

Original languageEnglish
JournalJournal for ImmunoTherapy of Cancer
Volume12
Issue number9
DOIs
StatePublished - 23 Sep 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Keywords

  • Combination therapy
  • Immunotherapy

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