Assistant Professor Univ. of Texas Southwestern Med. Ctr., Texas, United States
Disclosure(s):
Chen Yao, PhD: No financial relationships to disclose
Introduction/Rationale: Self-renewing stem-like T cells promote the efficacy of cancer immunotherapy and are a heterogeneous population with sub-lineages demonstrating different degrees of stemness. At the apex of this hierarchy are long-term (LT) stem-like T cells with the highest capacity of persistence, repopulation and response to immune checkpoint inhibitors (ICI). However, the pathway that establishes the hierarchy of stemness in chimeric antigen receptor (CAR) T cells and its role in anti-tumor efficacy of CAR T cells are unclear.
Methods: We analyzed CAR T cell infusion products from both humans and mice, examining epigenetic, transcriptional, and functional correlates of stem-like subsets. We deleted BACH2 to assess its role in LT stem-like differentiation and antitumor potency. In a GD2 CAR T model prone to exhaustion, we used small-molecule modulation to fine-tune BACH2 protein levels and temporally activate BACH2 during CAR T manufacture, followed by in vivo efficacy testing in solid tumor models.
Results: We demonstrate that BACH2 regulates LT stem-like CAR T cell differentiation and antitumor immunity in a dose-dependent manner. Pre-infusion LT stem-like CAR T cells displayed epigenetic activation of BACH2 and correlated with more robust antitumor responses in both mice and humans. After tumor clearance in vivo, LT stem-like cells emerged that transcriptionally and epigenetically upregulated BACH2 and downregulated TOX. Loss of BACH2 impaired antitumor efficacy and disrupted the LT stem-like transcriptional program. In GD2 CAR T cells, quantitative control of BACH2 via a small molecule adjusted the balance between stemness and exhaustion. Temporal induction of BACH2 during CAR T manufacturing enhanced antitumor immunity in solid tumor models compared to unmodified cells.
Conclusion: Together, we show that BACH2 dosage establishes the hierarchy of stem-like CAR T cells and can be temporally and tunably controlled in CAR T cells to optimize differentiation and antitumor immunity.
