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1446 Inhibiting Free Fatty Acid Transport to Improve CAR-T Cell Therapy of Relapsed B-Cell Acute Lymphoblastic Leukemia

Program: Oral and Poster Abstracts
Session: 613. Acute Lymphoblastic Leukemias: Therapies Excluding Allogeneic Transplantation: Poster I
Hematology Disease Topics & Pathways:
Research, Fundamental Science, Translational Research, Metabolism, Biological Processes
Saturday, December 7, 2024, 5:30 PM-7:30 PM

Clarissa Garcia1, Kaylyn Lyons, MD1*, Tian Liu2*, Ilaria Iacobucci, PhD3, Amanda Novak, BS1*, Amy Argabright4*, Alexis Donnelly1*, Julian Grandvallet Contreras, BS2*, Huimin Geng, PhD5*, Sabrina Smith6, Xin Zhou, PhD7*, Markus Müschen, MD8, John Edgar Dick6, Julie R Haines, PhD4*, Angelo D'Alessandro, PhD9, Charles G. Mullighan, MBBS, MSc, MD10, Tzu Phang, PhD1*, M. Eric Kohler, MD, Ph.D11 and Matthew Witkowski, PhD1

1Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO
2Department of Pediatrics, Section of Hematology/Oncology/BMT, University of Colorado Anschutz Medical Campus, Aurora, CO
3St. Jude Children's Research Hospital, Memphis, TN
4Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO
5Department of Laboratory Medicine, University of California San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, CA
6Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
7Department of Computational Biology, St Jude Childrens Research Hospital, Memphis, TN
8Center of Molecular and Cellular Oncology, Yale University, New Haven, CT
9Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO
10Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN
11Department of Pediatrics- Hematology, Oncology, and Bone Marrow Transplant, University of Colorado Anschutz Medical Campus, Aurora, CO

Introduction: B-cell acute lymphoblastic leukemia (B-ALL) resistant to conventional chemotherapy is a leading cause of cancer-related mortality in children and young adults. Although CD19-directed Chimeric Antigen Receptor T-cell (CAR-T) therapy shows promise for relapsed/refractory B-ALL, its effectiveness is often compromised by leukemia-intrinsic resistance mechanisms that remain unclear. Recent evidence suggests that TP53 mutations negatively affect the long-term efficacy of CD19 CAR-T therapy in B-ALL, despite initial trials not identifying high-risk genetic features impacting early clinical responses. TP53 loss-of-function mutations, although rare at diagnosis, are enriched in relapsed B-ALL and associated with chemotherapy resistance and poor survival.

Methods and Results: To dissect the B-ALL-intrinsic role of p53 during CAR-T therapy, we found that TP53 loss-of-function mutations in a subset of human B-ALL cell lines conferred resistance to CAR-T cell killing in vitro and in vivo. To elucidate the pathways driving CAR-T resistance in TP53-mutated (mut) B-ALL cells, we performed genome-wide CRISPR/Cas9 screening on isogenic TP53-wildtype (wt) and TP53-mut CD19+ B-ALL cell lines treated with CD19-CAR-T cells ex vivo. This screening approach identified the free fatty acid transporter FATP2 (encoded by SLC27A2) as a critical factor; as its genetic ablation enhanced CAR-T efficacy against TP53-mut B-ALL lines. Analysis of RNA-seq data from 1104 pediatric B-ALL patients revealed that high SLC27A2 mRNA expression at B-ALL diagnosis correlated with poor overall survival and increased free fatty acid metabolism. To understand the mechanism of FATP2 activity in B-ALL survival, we found FATP2-expressing B-ALL lines internalize long-chain free fatty acids more efficiently than non-FATP2-expressing human B-ALL cell lines. Additionally, FATP2-mediated CAR-T resistance in TP53-mut B-ALL cells was reversible by depleting exogenous fatty acids. Stable isotope free fatty acid uptake tracing revealed a role for FATP2 in promoting succinate accumulation in TP53-mutated B-ALL cells, thus significantly altering cellular metabolism that may have contributed to CAR-T resistance. Ongoing experiments aim to identify the precise mechanisms contributing to leukemia-intrinsic, FATP2-dependent CAR-T resistance.

Conclusions: Our studies suggest that FATP2 expression drives TP53-mutant B-ALL CAR-T resistance by facilitating the uptake of exogenous free fatty acids. Collectively, we propose targeting free fatty acid transport as a specific metabolic vulnerability in B-ALL that might improve CAR-T therapy outcomes.

Disclosures: Iacobucci: Mission Bio: Other: Travel expenses ; Arima Genomics: Consultancy. Dick: Bristol-Myers Squibb/Celgene: Research Funding; Pfizer/Trillium Therapeutics: Patents & Royalties: IP interest in SIRP-a therapeutics. Witkowski: Walter and Eliza Hall Institute: Patents & Royalties: Royalties - venetoclax.

*signifies non-member of ASH