Abstract 586: Orthogonal IL-2/IL-2RB signaling in adoptively transferred T cells controls tumor growth without the need for lymphodepletion in a B16 tumor model

Multiple adoptive T-cell therapy modalities (ACT) have delivered promising clinical responses in cancer patients. However, challenges including poor T cell effector function, lack of proliferation, and limited persistence have prevented ACTs from reaching their full curative potential. In addition, ACTs typically require lymphodepletion to aid cell engraftment. Lymphodepletion has been shown to improve persistence and efficacy of ACTs by elevating T-cell common gamma-chain cytokines like IL-7 and IL-15. However, lymphodepletion regimens have been identified as a risk factor for cytokine release syndrome (CRS) and infectious complications from opportunistic pathogens. IL-2, another common gamma-chain cytokine, is a potent stimulator of T cells, making it an attractive cytokine to support ACT and potentially bypass the need for lymphodepletion. However, therapeutic use of IL-2 is limited by systemic toxicity due its promiscuous activation of immune cells.

To facilitate selective delivery of an IL-2 signal to engineered T cells and avoid signaling in bystander T cells and NK cells, we developed a mouse orthogonal receptor/ligand system consisting of a mutated IL-2 Receptor Beta (moRβ) and a pegylated, IL-2 mutein (moIL-2) that does not significantly activate the wild type IL-2β receptor but does activate moRβ. T cells from pmel-1 T cell receptor-transgenic mice, recognizing gp100 on B16 melanoma cells were transduced with moRβ (orthoPmel). A highly active moIL-2 was continuously dosed for four weeks in mice. Thy1.1+ orthoPmel T cells were tracked by FACS and IHC systemically and in the tumor.

During orthoPmel manufacturing, moIL-2 specifically enriched orthoPmel compared to mouse WT IL-2. OrthoPmel in combination with moIL-2 controlled tumor growth in lymphoreplete mice bearing established B16 tumors while neither component alone inhibited tumor growth. moIL-2 significantly expanded orthoPmel systemically and intratumorally, with orthoPmel ultimately accounting for greater than 80% or 40% of all peripheral and intratumoral T cells, respectively. Systemic orthoPmel maintained a consistent central memory and effector memory mix throughout the four-week moIL-2 treatment course. moIL-2 also induced the expression of activation markers, CD25 and Granzyme B, in intratumoral orthoPmel.

These findings validate than an orthogonal IL-2/IL-2Rβ platform can enhance efficacy of ACTs without peripheral expansion or activation of NK cells or non-tumor specific T cells and the toxicities typically associated with high dose IL-2 therapy. Importantly, these results demonstrate the potential of this platform overcome the requirement of lymphodepletion in adoptive cell therapies.

Citation Format: Christina Kochel, Meng Sun, Navneet Ratti, Sandro Vivona, Mahalaksmi Ramadass, Marie Semana, Michele Bauer, Mohammed Ali, Jan Emmerich, Rob Kastelein, Patrick J. Lupardus, Paul-Joseph Aspuria, Martin Oft. Orthogonal IL-2/IL-2RB signaling in adoptively transferred T cells controls tumor growth without the need for lymphodepletion in a B16 tumor model [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 586.

Conditional Deletion of Pdcd1 Identifies the Cell-Intrinsic Action of PD-1 on Functional CD8 T Cell Subsets for Antitumor Efficacy

Programmed cell death-1 (PD-1) blockade has a profound effect on the ability of the immune system to eliminate tumors, but many questions remain about the cell types involved and the underlying mechanisms of immune activation. To shed some light on this, the cellular and molecular events following inhibition of PD-1 signaling was investigated in the MC-38 colon carcinoma model using constitutive (PD-1 KO) and conditional (PD1cKO) mice and in wild-type mice treated with PD-1 antibody. The impact on both tumor growth and the development of tumor immunity was assessed. In the PD-1cKO mice, a complete deletion of Pdcd1 in tumor-infiltrating T cells (TILs) after tamoxifen treatment led to the inhibition of tumor growth of both small and large tumors. Extensive immune phenotypic analysis of the TILs by flow and mass cytometry identified 20-different T cell subsets of which specifically 5-CD8 positive ones expanded in all three models after PD-1 blockade. All five subsets expressed granzyme B and interferon gamma (IFNγ). Gene expression analysis of the tumor further supported the phenotypic analysis in both PD-1cKO- and PD-1 Ab-treated mice and showed an upregulation of pathways related to CD4 and CD8 T-cell activation, enhanced signaling through costimulatory molecules and IFNγ, and non-T-cell processes. Altogether, using PD-1cKO mice, we define the intrinsic nature of PD-1 suppression of CD8 T-cell responses in tumor immunity.

Antitumor efficacy of combined CTLA4/PD-1 blockade without intestinal inflammation is achieved by elimination of FcγR interactions

Background

Programmed cell death protein 1 (PD-1) and CTLA4 combination blockade enhances clinical efficacy in melanoma compared with targeting either checkpoint alone; however, clinical response improvement is coupled with increased risk of developing immune-related adverse events (irAE). Delineating the mechanisms of checkpoint blockade-mediated irAE has been hampered by the lack of animal models that replicate these clinical events.

Methods

We have developed a mouse model of checkpoint blockade-mediated enterocolitis via prolonged administration of an Fc-competent anti-CTLA4 antibody.

Results

Sustained treatment with Fc-effector, but not Fc-mutant or Fc-null, anti-CTLA4 antagonist for 7 weeks resulted in enterocolitis. Moreover, combining Fc-null or Fc-mutant CTLA4 antagonists with PD-1 blockade results in potent antitumor combination efficacy indicating that Fc-effector function is not required for combination benefit.

Conclusion

These data suggest that using CTLA4 antagonists with no Fc-effector function can mitigate gut inflammation associated with anti-CTLA4 antibody therapy yet retain potent antitumor activity in combination with PD-1 blockade.

Abstract 267: Combining androgen deprivation with immune checkpoint blockade delays the development of castration resistance in a murine model of prostate cancer

Androgen deprivation therapy induces immune cell infiltration in human prostate cancer. These findings suggest that immunotherapy may be most efficacious when administered concurrently with androgen deprivation, early in disease progression. We used a subcutaneous allograft model of murine prostate cancer (Myc-Cap), which mimics the development of human castration-resistant prostate cancer (CRPC) progression to study the anti-tumor effects of concurrent hormonal/immunotherapy. Implanted Myc-Cap tumors initially respond to androgen deprivation (degarelix acetate or bilateral orchiectomy), but mice eventually progress with CRPC. To test the hypothesis that the combination of androgen deprivation and immune checkpoint blockade could mediate pre-clinical benefit, we treated mice with either anti-PD-1, a depleting anti-CTLA-4 antibody (IgG2A), a non-depleting anti-CTLA-4 antibody (IgG1 D265A) or antibody combinations in the peri-castration period, then followed mice for the development of castration-resistant disease. Interestingly, the depleting anti-CTLA-4 antibody with/without anti-PD-1 antibody was strikingly effective in preventing the emergence of castration-resistant disease. The median castration-resistance free survival was 22 days in mice treated with androgen deprivation alone versus 32 days in mice treated with androgen deprivation and depleting anti-CTLA-4 antibody (P<0.05, compared to androgen deprivation alone) versus 30 days in mice treated with androgen deprivation, depleting anti-CTLA-4 and anti-PD-1 (P<0.05, compared to androgen deprivation alone; non-significant, compared to androgen deprivation and depleting anti-CTLA-4 antibody). Immunologically, we found that castration increases intratumoral infiltration of helper, cytotoxic and regulatory T cells (Tregs), natural killer cells, and macrophages, as well as effector cytokine production of T cells. We also found up-regulated expression of CTLA-4 and PD-1 as well as their respective ligands. Mechanistic studies showed that androgen deprivation combined with depleting anti-CTLA-4 /anti-PD-1 significantly reduces intratumoral Tregs and increases interferon-γ- or tumor necrosis factor-α- producing T cells in the tumor and its draining lymph node. In conclusion, while androgen deprivation renders the tumor microenvironment more immunogenic; the combination of androgen deprivation and depleting anti-CTLA-4 antibody with/without anti-PD-1 can significantly delay the development of CRPC.

Citation Format: Ying-Chun Shen, Christina Kochel, Brian J. Francica, Angela Alme, Christopher Nirschl, Thomas Nirschl, Zoila Areli Lopez Bujanda, Maria A. Carrera H, Mark Selby, Alan Korman, Charles G. Drake. Combining androgen deprivation with immune checkpoint blockade delays the development of castration resistance in a murine model of prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 267. doi:10.1158/1538-7445.AM2015-267