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484 Impact of Epichaperome Inhibitor PU-H71 on Anti-Tumor T Cell Responses and Its Implications for Immune and Cellular Therapy

Program: Oral and Poster Abstracts
Type: Oral
Session: 703. Cellular Immunotherapies: Basic and Translational IV
Hematology Disease Topics & Pathways:
Research, Lymphoid Leukemias, Translational Research, Combination therapy, Diseases, Therapies, Lymphoid Malignancies
Sunday, December 11, 2022: 10:15 AM

Jeremie Martinet1,2,3*, Mayumi Sugita, MD3, Mohammad Alhomoud, MD3, Catalina Abad4*, Gabriela Chiosis, PhD5*, Gail J. Roboz, MD6, Olivier Boyer, MD, PhD1,7 and Monica L. Guzman, PhD3

1University of Rouen Normandy, Inserm, U1234, F-76000, Rouen, France
2Rouen university hospital, Department of immunology and biotherapy, F-76000, Rouen, France
3Division of Hematology and Oncology, Department of Medicine, Weill Cornell Medicine/New York Presbyterian Hospital, New York, NY
4Inserm U1234, University of Rouen Normandy, Rouen, France
5Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY
6Division of Hematology and Oncology, Weill Cornell Medicine and The New York-Presbyterian Hospital, New York, NY
7Rouen university hospital, Department of immunology and biotherapy, F-76000, Rouen, Normandy, France

The epichaperome is a tightly integrated network of proteins supporting critical roles in the tumor-associated microenvironment and cancer cell survival. The epichaperome inhibitor PU-H71 is under development in clinical trials. A patient with an unclassified myeloproliferative neoplasm harboring a novel PML-SYK fusion, who progressed to acute myeloid leukemia despite allogeneic stem cell transplantation was successfully treated using PU-H71 (Sugita et al. 2021, NPJ Precis Oncol). We reported changes in donor immune cells after PU-H71 treatment, suggesting that epichaperome inhibition was modulating antitumor immune responses and improving the efficacy of cellular immunotherapy. To investigate this hypothesis, we analyzed the effects of PU-H71 on antitumor immune responses, GvHD and CAR-T cells.

We tested the effects of PU-H71 on C57BL/6 mice immune responses to ovalbumine (OVA) immunization. OVA-specific T- and B-cell responses were evaluated by ELISPOT and ELISA, respectively. When administered at the time of priming, PU-H71 significantly increased the number of IFNγ-secreting T cells as compared to controls (median 126 vs 42 per million of cells, p=0.0002; n=8), without an impact on T cell phenotype or anti-OVA antibody levels. In contrast, PU-H71 had no effect when administered once the OVA-specific T cell response was ongoing. Then, we tested the effect of PU-H71 on antitumor immune responses in OVA-primed mice challenged with E.G7 (OVA+) or parental EL4 lymphoma cell lines (OVAneg). PU-H71 improved in vivo anti-tumor immune responses in OVA-primed mice challenged with E.G7 but not EL4 cells (Mean survival 17.5 vs 14 days, p=0.0003, n=8 per group).

Since PU-H71 augmented early but not established T cell responses, we next evaluated whether it would have an effect on a GvHD murine model. Lethally-irradiated B6C3F1 mice received bone marrow and splenocytes from C57BL/6 mice and were treated with PU-H71 or vehicle at the first signs of GvHD (D11). GvHD clinical scores and histological analysis (colon, small intestine, liver and skin) were assessed. PU-H71 did not aggravate GvHD at both clinical and histological levels. Therefore, PU-H71 augments antigen-specific mouse T cell responses by acting during priming.

To better understand its effect on human T cells and its potential adjuvant effect during cellular therapy, we next evaluated in vitro and in vivo CAR-T cells phenotype and function in the presence of PU-H71. T cells were purified from healthy donor PBMCs and were transduced with a CD19.4-1Bb.3z lentiviral vector to obtain CART19 cells. First, we found that epichaperome indeed forms in CART19 cells upon activation with anti-CD3/CD28 beads vs control. In vitro cytotoxicity of CAR-T cells toward NALM6 B-ALL cells was significantly improved (55.39 vs 74.66%, p=0.0356) by PU-H71. Finally, the therapeutic effect of the combination of PU-H71 and CART19 was evaluated in a B-ALL NSG mouse model using NALM6-BLIV cells, with bioluminescence imaging and flow cytometry (CART19 and leukemic cells) monitoring. Results suggest that PU-H71 administration increases CART19 numbers in the bone marrow and improves their in vivo antitumor efficacy against NALM6.

Together, our results show that PU-H71 augments antigen-specific T cell responses during priming including CAR-T cell cytotoxicity, with little effect on ongoing immune responses including GvHD. Our data suggest that PU-H71 improves the in vivo efficiency of CAR-T cells in a B-ALL mouse model. In addition to its previously demonstrated direct anti-tumor effect, PU-H71 also had an adjuvant effect on anti-tumor T cell responses while not aggravating GvHD, which supports its clinical evaluation in the post-transplant setting or in combination with immune therapies like CAR-T cells.

Disclosures: Martinet: Grifols: Research Funding. Chiosis: Samus Therapeutics Inc: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Roboz: Genentech/Roche: Consultancy, Other: Travel and accommodation expenses; Sandoz: Consultancy, Other: Travel and accommodation expenses; Celltrion: Consultancy, Other: Travel and accommodation expenses; Janssen: Consultancy, Other: travel and accommodation expenses, Research Funding; Karyopharm Therapeutics: Research Funding; Helsinn Therapeutics: Consultancy; Pfizer: Consultancy, Honoraria, Other: Travel and accommodation expenses; Bristol Myers Squibb: Consultancy; Daiichi Sankyo: Consultancy; Mesoblast: Consultancy; Array BioPharma: Other: Travel and accommodation expenses; Agios: Other: travel, Research Funding; CTI: Research Funding; Amphivena Therapeutics: Other: Travel and accommodation expenses, Research Funding; Jasper Therapeutics: Consultancy; Eisai: Other: Travel and accommodation expenses; MedImmune: Consultancy, Research Funding; Astex Pharmaceuticals: Consultancy, Other: Travel and Accommodation expenses, Research Funding; Novartis: Consultancy, Other: Travel and accommodation expenses, Research Funding; Otsuka: Consultancy; MEI Pharma: Consultancy, Research Funding; Jazz: Consultancy, Other: travel; Roche: Consultancy; Takeda: Consultancy; GlaxoSmithKline: Consultancy; Amgen: Consultancy; Celgene: Consultancy, Other: travel and accommodation expenses, Research Funding; Astellas: Consultancy; Bristol Myers Squibb: Consultancy; Clovis Oncology: Other: Travel and accommodation expenses; Bayer: Consultancy, Other: Travel and accommodation expenses; Sunesis Pharmaceuticals: Other: Travel and accommodation expenses, Research Funding; Mofitt Cancer Center: Research Funding; Amgen: Consultancy, Other: travel; Agios: Consultancy, Research Funding; AbbVie: Consultancy, Other: travel and accommodations, Research Funding; Actinium: Consultancy; Onconova Therapeutics: Research Funding; Tensha Therapeutics: Research Funding. Boyer: Argenx: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; UCB: Consultancy, Honoraria, Patents & Royalties, Research Funding; OGD2: Consultancy, Honoraria; Egle Tx: Consultancy, Honoraria; BMS: Consultancy, Honoraria. Guzman: BridgeMedicines: Research Funding; SeqRX: Current equity holder in private company.

*signifies non-member of ASH