Abstract LB212: Allogeneic, IL-2-independent tumor-infiltrating lymphocytes expressing membrane-bound IL-15 (cytoTIL15࣪) eradicate tumors in a melanoma PDX model through recognition of shared tumor antigens

Standard tumor-infiltrating lymphocyte (TIL) therapy requires IL-2 administration to support TIL expansion and survival, but this cytokine is associated with T cell exhaustion and can result in severe toxicities that limit patient eligibility (1). To this end, we genetically engineered TIL to express membrane-bound IL-15 (mbIL15) under the control of Obsidian’s cytoDRIVE® technology (cytoTIL15࣪), which allows regulation of protein expression via a drug-responsive domain upon acetazolamide (ACZ) administration. IL-15 is a preferred cytokine over IL-2 to mediate TIL activation and expansion, because it does not result in CD8 T cell exhaustion or stimulate regulatory CD4 T cells, and enhances development of a memory T-cell phenotype. We have previously demonstrated IL-2-independent, 3-6-fold increased cytoTIL15 persistence in an antigen-independent setting relative to unengineered TIL therapy with IL-2 (uTIL) (2). Due to the challenge of generating autologous tumor/TIL-matched pairs and most importantly, to assess cytoTIL15 cell’s functional impact on anti-tumor growth across multiple donors, we developed an allogeneic patient-derived xenograft (PDX) model. To establish the model, different melanoma tumor digests were co-incubated in vitro with select HLA-A*02-matched, allogeneic melanoma TIL donors to assess their reactivity. Tumors were screened for expression of shared antigens, such as gp100 and MART1, and TIL donor TCRs were screened with tetramers. Once established, serially passaged tumor fragments were grown, measured, and randomized into groups to receive intravenous transfer of TIL (n=8/cohort). Mice receiving uTIL were treated with four saturating doses of recombinant IL-2, and mice receiving cytoTIL15 cells received either vehicle or oral 200 mg/kg ACZ daily for the entire study, without any IL-2. Three of four cytoTIL15 cell preparations from different donors dosed with ACZ achieved significant tumor growth inhibition compared to uTIL. Four mice developed complete responses as early as 17 days post cytoTIL15 cell transfer. The level of anti-tumor response was associated with increased frequency of MART1-reactive cytoTIL15 cells. On day 20 after TIL transfer, tumors and secondary lymphoid organs were collected (n=4/cohort). Tumors treated with cytoTIL15 cells + ACZ showed an 8-10-fold increased TIL infiltration compared to uTIL or cytoTIL15 cells + vehicle. Moreover, enhanced cytoTIL15 cell infiltration and anti-tumor activity was associated with increases in pro-inflammatory cytokines (e.g., IFNγ). Taken together, these data clearly demonstrate the superiority of cytoTIL15 cells over uTIL for controlling or eradicating melanoma tumor outgrowth and the utility of an allogeneic PDX model for comparative evaluation of tumor-antigen specific TIL reactivity.

References: 1. Yang JC. Toxicities associated with adoptive T-cell transfer for Cancer. Cancer J. 2015. 2. Burga R. et al Genetically engineered tumor-infiltrating lymphocytes (cytoTIL15) exhibit IL-2-independent persistence and anti-tumor efficacy against melanoma in vivo. SITC 36th annual meeting 2021.

Citation Format: Jeremy H. Tchaicha, Scott Lajoie, Rachel Burga, Theresa Ross, Benjamin Primack, Meghan Langley, Violet Young, Alonso Villasmil Ocando, Kyle Pedro, Jack Tremblay, Gauri Kulkarni, Mithun Khattar, Dhruv Sethi, Michelle Ols, Gabriel Helmlinger, Gary Vanasse, Shyam Subramanian, Jan ter Meulen. Allogeneic, IL-2-independent tumor-infiltrating lymphocytes expressing membrane-bound IL-15 (cytoTIL15࣪) eradicate tumors in a melanoma PDX model through recognition of shared tumor antigens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB212.

166 Genetically engineered tumor-infiltrating lymphocytes (cytoTIL15) exhibit IL-2-independent persistence and anti-tumor efficacy against melanoma in vivo

Background

Adoptive cell therapy with tumor-infiltrating lymphocytes (TILs) has demonstrated tremendous promise in clinical trials for patients with solid or metastatic tumors.1 However, current TIL therapy requires systemic administration of IL-2 to promote TIL survival, and IL-2-associated toxicities greatly limit patient eligibility and reduce the long-term clinical benefit of TIL therapy.2 3 Unlike IL-2, which promotes T cell exhaustion, IL-15 maintains antigen-independent TIL persistence through homeostatic proliferation and supports CD8+ T cell anti-tumor activity without stimulating regulatory T cells. We designed genetically engineered TILs to express a regulated form of membrane-bound IL-15 (mbIL15) for tunable long-term persistence, leading to enhanced efficacy and safety for the treatment of patients with solid tumors.

Methods

Obsidian’s cytoDRiVE™ platform includes small human protein sequences called drug responsive domains (DRD)s that enable regulated expression of a fused target protein under control of FDA-approved, bioavailable small molecule ligands. cytoTIL15 contains TILs engineered with mbIL15 under the control of a carbonic-anhydrase-2 DRD, controlled by the ligand acetazolamide (ACZ). After isolation from tumors, TILs were transduced and expanded in vitro through a proprietary TIL expansion process. cytoTIL15 were immunophenotyped and assessed for in vitro antigen-independent survival and co-cultured with tumor cells to assess polyfunctionality and cytotoxicity. In vivo TIL persistence and anti-tumor efficacy was evaluated through adoptive transfer of TILs into immunodeficient NSG mice, either naïve or implanted with subcutaneous patient-derived-xenograft (PDX) tumors.

Results cytoTIL15 and conventional IL2-dependent TILs isolated from melanoma tumor samples expanded to clinically relevant numbers over 14 days. Throughout expansion, cytoTIL15 were enriched for CD8+ T cells and acquired enhanced memory-like characteristics, while maintaining diverse TCRVβ sub-family representation. cytoTIL15 demonstrated enhanced potency over conventional TILs, as measured by increased polyfunctionality and cytotoxicity against tumor and PDX lines in vitro (figure 1A). In a 10-day antigen-independent in vitro assay, cytoTIL15 persisted at greater frequencies than conventional TILs in the absence of IL-2 (figure 1B; *p<0.05). cytoTIL15 adoptively transferred into naïve NSG mice demonstrated ACZ-dependent long-term persistence without antigen or exogenous IL-2, whereas conventional TILs were undetectable >30 days following adoptive cell transfer (figure 1C). Importantly, cytoTIL15 achieved significant tumor control in a human PDX model (figure 1D), which correlated with increased TIL accumulation in secondary lymphoid organs.

Abstract 166 Figure 1

cytoTIL15 demonstrate superior persistence. cytoTIL15 is an engineered TIL product expressing regulatable mbIL15. (A) cytoTIL15 demonstrate enhanced in vitro cytotoxicity after co-culture with melanoma tumor lines (representative data from 3 TIL donors). (B) cytoTIL15 have improved persistence in antigen- and IL2- independent culture conditions in vitro compared to conventional TILs cultured in the absence of IL-2 as well as (C) in vivo compared to conventional TILs supplemented with IL-2, when engrafted into NSG mice (in vitro: representative data from 1 TIL donor, performed in >3 replicate donors, in vivo: n=5/group, representative of 1 TIL donor, performed in >3 replicate donors). (D) cytoTIL15 (with 200mg/kg ACZ PO QD) demonstrate enhanced anti-tumor efficacy in a xenograft melanoma model as compared to conventional TILs (with 50000 IU IL-2 q8h BID, IP for 5 days) (n=8/group, representative of 1 TIL donor, performed in >2 replicate donors; ACT = adoptive cell transfer).

Conclusions

Taken together, the superior persistence and potency of cytoTIL15 in the complete absence of IL-2 highlights the clinical potential of cytoTIL15 as a novel TIL product with enhanced safety and efficacy for patients with melanomas, and other solid tumors.

Acknowledgements

The authors wish to acknowledge the Cooperative Human Tissue Network for the their supply of human tumor tissue, and the MD Anderson Cancer Center for technical support; schematic created with BioRender.com.

References

Chandran SS, Somerville RPT, Yang JC, Sherry RM, Klebanoff CA, Goff SL, Wunderlich JR, Danforth DN, Zlott D, Paria BC, Sabesan AC, Srivastava AK, Xi L, Pham TH, Raffeld M, White DE, Toomey MA, Rosenberg SA, Kammula US. Treatment of metastatic uveal melanoma with adoptive transfer of tumour-infiltrating lymphocytes: a single-centre, two-stage, single-arm, phase 2 study. Lancet Oncol 2017 Jun;18(6):792–802. doi: 10.1016/S1470-2045(17)30251-6. Epub 2017 Apr 7. PMID: 28395880; PMCID: PMC5490083.

Yang JC. Toxicities associated with adoptive T-cell transfer for Cancer. Cancer J 2015;21:506–9.

Schwartz RN, Stover L, Dutcher JP. Managing toxicities of high-dose interleukin-2. Oncology (Williston Park) 2002 Nov;16(11 Suppl 13):11–20. PMID: 12469935.

Polyamines drive myeloid cell survival by buffering intracellular pH to promote immunosuppression in glioblastoma

Glioblastoma is characterized by the robust infiltration of immunosuppressive tumor-associated myeloid cells (TAMCs). It is not fully understood how TAMCs survive in the acidic tumor microenvironment to cause immunosuppression in glioblastoma. Metabolic and RNA-seq analysis of TAMCs revealed that the arginine-ornithine-polyamine axis is up-regulated in glioblastoma TAMCs but not in tumor-infiltrating CD8+ T cells. Active de novo synthesis of highly basic polyamines within TAMCs efficiently buffered low intracellular pH to support the survival of these immunosuppressive cells in the harsh acidic environment of solid tumors. Administration of difluoromethylornithine (DFMO), a clinically approved inhibitor of polyamine generation, enhanced animal survival in immunocompetent mice by causing a tumor-specific reduction of polyamines and decreased intracellular pH in TAMCs. DFMO combination with immunotherapy or radiotherapy further enhanced animal survival. These findings indicate that polyamines are used by glioblastoma TAMCs to maintain normal intracellular pH and cell survival and thus promote immunosuppression during tumor evolution.

EXTH-43. GENERATION OF A B-CELL-BASED VACCINE FOR THE TREATMENT OF GLIOBLASTOMA

Immunotherapy has revolutionized the treatment of many tumors. However, most glioblastoma (GBM) patients have not, so far, benefited from such successes. With the goal of exploring ways to boost anti-GBM immunity, we developed a B-cell-based vaccine (BVax) that consists of 4-1BBL+ B cells activated with CD40 agonism and IFNg stimulation. BVaxmigrate to key secondary lymphoid organs and are proficient at antigen cross-presentation, which promotes both the survival and functionality of CD8+ T cells. A combination of radiation, BVax, and PD-L1 blockade conferred tumor eradication in 80% of treated tumor-bearing animals. This treatment elicited immunologic memory that prevented the growth of new tumors upon subsequent re-injection in cured mice. GBM patient-derived BVax were successful in activating autologous CD8+ T cells; these T cells showed a strong ability to kill autologous glioma cells. In addition to the role in activating CD8+ T cells, BVax produce tumor-specific antibodies able to control tumor growth via antibody-mediated cell cytotoxicity. In conclusion, BVax tackles GBM immunosurveillance escape by using both cellular (CD8+ T-cell activation) and humoral (anti-tumor antibody production) immunity. Our study provides an efficient alternative to current immunotherapeutic approaches that can be readily translated to the clinic.

Cord blood natural killer cells expressing a dominant negative TGF-β receptor: Implications for adoptive immunotherapy for glioblastoma

Cord blood (CB) natural killer (NK) cells are promising effector cells for tumor immunotherapy but are currently limited by immune-suppressive cytokines in the tumor microenvironment, such as transforming growth factor (TGF-β). We observed that TGF-β inhibits expression of activating receptors such as NKG2D and DNAM1 and decreases killing activity against glioblastoma tumor cells through inhibition of perforin secretion. To overcome the detrimental effects of TGF-β, we engrafted a dominant negative TGF-β receptor II (DNRII) on CB-derived NK cells by retroviral transduction and evaluated their ability to kill glioblastoma cells in the presence of TGF-β. After manufacture using Good Manufacturing Practice-compliant methodologies and transduction with DNRII, CB-derived DNRII-transduced NK cells expanded to clinically relevant numbers and retained both their killing ability and their secretion of interferon-γ upon activation. More important, these cells maintained both perforin expression and NKG2D/DNMA1 expression in the presence of TGF-β allowing for recognition and killing of glioblastoma tumor cells. Hence, NK cells expressing a DNRII should have a functional advantage over unmodified NK cells in the presence of TGF-β-secreting tumors and may be an important therapeutic approach for patients with cancer.

STAT3 is necessary for liver myeloid-derived suppressor cell PDL-1-dependent inhibition of genetically modified T cell function. (IRC5P.466)

Introduction: Liver myeloid-derived suppressor cells (L-MDSC) can suppress genetically-modified T cells (GMT). STAT3 is a regulator of myeloid progenitors and promotes MDSC expansion. We hypothesized an increase in L-MDSC STAT3 activity in the setting of liver metastases (LM), contributing to suppression of GMT. Methods: LM were established in C57BL/6 mice by splenic injection of CEA+ MC38 tumor cells. L-MDSC were isolated with anti-CD11b immunomagnetic beads and flow cytometry used for phenotypic analysis. Ex vivo blockade of STAT3 was performed with cucurbitacin I (JSI-124) and Celastrol. Serum STAT3 and phospohorylated STAT3 (pSTAT3) levels were quantified by ELISA. Results: Both STAT3 and pSTAT3 levels were elevated (1.9-fold, p=0.005 and 1.6-fold, p=0.019) in serum of mice with established LM. L-MDSC isolated from LM-mice contained more pSTAT3 than normal mice (4.9% vs. 1.1%, p=0.007). Having previously demonstrated PDL-1-dependent suppression of anti-CEA GMT by L-MDSC, we asked if increased STAT3 activity contributed to immunosuppression. Blockade of STAT3 led to decreased PDL-1 expression on L-MDSC [52.7% vs. 9.9% (JSI-124 p=0.002) vs. 15.4% (Celastrol p=0.002)], likely hampering PDL-1 dependent immunosuppression. Conclusion: We demonstrated increased STAT3 and pSTAT3 in L-MDSC of mice with LM, and STAT3-dependent PDL-1 expression. Blockade of STAT3 is a potential clinical strategy for preventing L-MDSC PDL-1 expression and suppression of GMT via the PD-1/PDL-1 axis.

Liver myeloid-derived suppressor cells inhibit genetically modified T cells in an IDO-dependent manner. (IRC5P.464)

Introduction: The immunosuppressive environment in the liver limits the potency of immunotherapy for liver metastases (LM). Myeloid-derived suppressor cells (MDSC) expand in response to LM and mediate T cell suppression via indoleamine 2,3-dioxygenase (IDO). We hypothesized that IDO inhibition rescues genetically modified T cell (GMT) performance through blockade of MDSC-mediated suppression. Methods: Anti-CEA GMT were produced from activated murine splenocytes. C57BL/6 mice were injected via spleen with CEA+ MC38 tumor cells, and MDSC isolated by CD11b+ immunomagnetic beads. MDSC were evaluated by flow cytometry and ex vivo co-culture with CFSE-labeled GMT stimulated by CEA+ tumor, with and without IDO-blockade. Results: IDO expression was demonstrated in MDSC isolated from tumor-bearing (15.7-46.2%) and control livers (15.1%-37.7%). Increased IDO expression was dependent on STAT3 activity in the setting of LM, as blockade with cucurbitacin I (JSI-124) led to downregulated IDO expression on MDSC (48% vs. 21.5%, p=0.005). Liver MDSC suppressed GMT proliferation two-fold (p=0.004). IDO blockade with competitive inhibitor 1-methyltryptophan (1-MT) reversed GMT suppression, resulting in a five-fold increase in GMT division (p=0.016). Conclusions: Liver MDSC express IDO, and IDO represents a mechanism through which MDSC suppress anti-CEA GMT. Our results indicate that blockade of IDO activity may be a viable strategy for enhancing GMT targeted immunotherapy for liver metastases.

Effects of colorectal cancer liver metastases on intrahepatic B cells (P2093)

Background: We and others have found that liver metastases (LM) mediate tolerogenic effects. B cells make up a significant proportion of liver lymphocytes but their function in the normal liver and in the setting of LM is poorly defined. Therefore, we attempted to define the features of HBC in the setting of LM. Methods: We have used a murine model of CEA+ colorectal LM to study the effects of malignancy on HBC. Tumor cells were injected into the portal circulation of C57Bl/6 mice to induce LM, and HBC were analyzed after two weeks. Results: 50% of mice with LM secreted anti-CEA antibodies, suggesting that the tumor is recognized by B cells in our model. HBC comprised 45±10% of lymphocytes in normal livers, and their frequency was reduced in mice with LM (25±3%, p=0.03). A significant reduction in the frequency of IgM+IgDlo transitional B cells, precursors of mature B cells, was observed in mice with LM (23±2% and 8±4% in normal and metastatic livers respectively, p=0.02). HBC exhibited significant down-regulation of two molecules associated with T cell activation: MHCII (7.5±3.5%, down from 31±5% in normal livers, p=0.03) and CD80 (0.9±0.4%, down from 9.6±1.4% in normal livers, p=0.02). Conclusion: The ability of HBC to mount an immune response may be compromised in the setting of LM as evidenced by reduction of HBC number and diminished HBC expression of MHCII and CD80. Further research is needed to elucidate the function of hepatic B cells during liver metastasis.