RORγ Agonists Enhance the Sustained Antitumor Activity through Intrinsic Tc17 Cytotoxicity and Tc1 Recruitment

Activation of RORγ with synthetic small-molecule agonists has been shown to enhance type 17 effector (CD4⁺ Th17 and CD8⁺ Tc17 cells) cell functions and decrease immunosuppressive mechanisms, leading to improved antitumor efficacy in adoptive cell transfer and syngeneic murine tumor models. However, whether Tc17 cells possess intrinsic cytotoxicity and the mechanism they use to lyse target cells is controversial. We report here that Tc17 cells were lytic effectors dependent on perforin and granzyme A. In contrast to Tc1 cells, Tc17 cells resisted activation-induced cell death and maintained granzyme A levels, which conferred the ability to lyse target cells in serial encounters. Thus, although the acute lytic capacity of Tc17 cells could be inferior to Tc1 cells, comparable lysis was achieved over time. In addition to direct lytic activity, Tc17 cells infiltrated early into the tumor mass, recruited other CD8⁺ T cells to the tumor, and enhanced the survival and lytic capability of these cells during repeated target encounters. Synthetic RORγ agonists further augmented Tc17 survival and lytic activity in vitro and in vivo, controlling tumor growth not only through direct cytotoxicity, but also through recruitment and improved function of other effector cells in the tumor microenvironment, which suggests complementary and cooperate activities for effective immunotherapy.

Synthetic RORγ agonists regulate multiple pathways to enhance antitumor immunity

RORγt is the key transcription factor controlling the development and function of CD4⁺ Th17 and CD8⁺ Tc17 cells. Across a range of human tumors, about 15% of the CD4⁺ T cell fraction in tumor-infiltrating lymphocytes are RORγ+ cells. To evaluate the role of RORγ in antitumor immunity, we have identified synthetic, small molecule agonists that selectively activate RORγ to a greater extent than the endogenous agonist desmosterol. These RORγ agonists enhance effector function of Type 17 cells by increasing the production of cytokines/chemokines such as IL-17A and GM-CSF, augmenting expression of co-stimulatory receptors like CD137, CD226, and improving survival and cytotoxic activity. RORγ agonists also attenuate immunosuppressive mechanisms by curtailing Treg formation, diminishing CD39 and CD73 expression, and decreasing levels of co-inhibitory receptors including PD-1 and TIGIT on tumor-reactive lymphocytes. The effects of RORγ agonists were not observed in RORγ−/− T cells, underscoring the selective on-target activity of the compounds. In vitro treatment of tumor-specific T cells with RORγ agonists, followed by adoptive transfer to tumor-bearing mice is highly effective at controlling tumor growth while improving T cell survival and maintaining enhanced IL-17A and reduced PD-1 in vivo. The in vitro effects of RORγ agonists translate into single agent, immune system-dependent, antitumor efficacy when compounds are administered orally in syngeneic tumor models. RORγ agonists integrate multiple antitumor mechanisms into a single therapeutic that both increases immune activation and decreases immune suppression resulting in robust inhibition of tumor growth. Thus, RORγ agonists represent a novel immunotherapy approach for cancer.

Abstract 565: RORγ agonists regulate immune checkpoint receptors to enhance anti-tumor immunity

As the master transcription factor for Type 17 T cells, RORγt activates a program of gene expression associated with enhancing effector function and overcoming immune suppression. Lycera is developing synthetic, small molecule RORγ agonists for immunotherapy of cancer.

We have previously reported that RORγγ agonists increase type 17 cytokine and chemokine production, enhance cell survival and have single agent anti-tumor activity in syngeneic tumor models. Interestingly, transcriptional profiling and cytometry studies revealed that treatment of murine and human Th17 or Tc17 cells with RORγ agonists increases the expression of costimulatory receptors such as CD137 and decreased expression of coinhibitory receptors like PD-1.

Given the importance of PD-1 in anti-tumor immunity, we further characterized the effects of RORγ agonist on this pathway. In vitro treatment with RORγ agonists significantly decreases mean fluorescent intensity and percent PD-1+ cells after resting and repetitive restimulation of Type 17 T cells. RORγ agonists do not modulate PD-1 expression in RORγ-/- T cells. In co-cultures of wild type and RORγ-/- T cells in the presence of the agonist, RORγ-/- T cells have reduced PD-1 expression suggesting that RORγ agonists induce a transmissible effect on RORγ-/- T cells. However, ChIP-seq data indicates that RORγt does not directly bind to the promoter or enhancer element of PD-1. Transcriptional and epigenetic profiling experiments have identified several pathways modulated by RORγ agonists that may regulate PD-1 expression. Reduced PD-1 expression following RORγ agonist treatment has a functional impact as treated cells also resist PD-L1-mediated inhibition of cytokine production and proliferation.

Importantly, the decreased PD-1 expression observed after in vitro treatment with RORγ agonists is maintained following adoptive transfer of tumor specific T cells. These cells are highly effective at controlling tumor growth without further agonist treatment in vivo, suggesting that in vitro RORγ agonist treatment results in durable epigenetic changes.

In summary, RORγ agonists have been shown to decrease checkpoint receptor expression while enhancing cytokine production and promoting long term survival and self-renewal of T cells. These results provide rationales for combining an RORγ agonist with checkpoint inhibitor such as anti-CTLA4 or anti-PD-1. By integrating effects on different effector pathways, RORγ agonists represent a promising immunotherapy approach for the treatment of cancer.

Citation Format: Xiao Hu, Xikui Liu, Jacques Moisan, Chrystal Paulos, Yahong Wang, Chauncey Spooner, Charles Lesch, Rodney Morgan, David Mertz, Dick Bousley, Clarke Taylor, Chad Van Huis, Don Skalitzky, Thomas Aicher, Peter Toogood, Laura Carter. RORγ agonists regulate immune checkpoint receptors to enhance anti-tumor immunity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 565.

Abstract 4273: RORγ agonists as a novel immunotherapy approach for cancer

Agents that enhance activation or release suppression of the immune system could form the basis of new treatments for cancer. RORγt is the key transcription factor controlling the development and function of CD4+ Th17, CD8+ Tc17 and IL-17+ innate immune cells. RORγγmodulates expression of genes involved in multiple anti-tumor mechanisms and in some cancers Th17/Tc17 cells are reported to mediate potent and durable anti-cancer efficacy. To further enhance these responses, we designed small molecule RORγ agonists and characterized their activities on immune cells and utility in murine tumor models.

Synthetic agonists activate an RORγ-dependent reporter construct and when present during activation of murine or human T cells in vitro, increase production of IL-17A, IL-17F, IL-22 and GM-CSF without negatively impacting IFNγ production. Th17 and Tc17 cells differentiated in the presence of RORγ agonists exhibit decreased expression of inhibitory molecules such as PD-1, TIGIT, CD160, CD73 and increased expression of costimulatory molecules including CD137 (4-1BB) and CD226 (DNAM-1). Stimulation of CD4+ T cells with cytokine cocktails including TGFβ in vitro can generate Th17 and Treg cells; addition of RORγ agonists improves the Teff/Treg ratio via decreased FOXP3 and increased IL-17 expression. Functionally, RORγ agonist treatment reprograms cells to resist PD-1:PD-L1 mediated inhibition of proliferation and cytokine production. In vitro activation of OT-1 Tc17 cells with RORγ agonists generates potent effector cells that control the growth of large EG7 tumors when transferred into non-irradiated mice. The tumor-infiltrating lymphocytes from this model have enhanced survival, increased IL-17 production and decreased PD-1 expression. Oral administration of RORγ agonists to C57BL/6 mice significantly inhibits the growth of established, subcutaneous MC38 colon carcinoma tumors. The anti-tumor activity of RORγ agonists is dependent on T cells, as growth of MC38 cells implanted into scid mice is not affected by agonist treatment. RORγ agonists also inhibit growth of established, subcutaneous 4T1 mammary carcinoma tumors in Balb/c mice. In the tumors from agonist-treated animals there is significantly elevated expression of RORγ and IL-17 as well as decreased CD73 expression with evidence of decreased metastases.

As a transcription modulator, RORγ agonists increase immune activation and decrease immune suppression. These activities translate into robust anti-tumor effects in syngeneic tumor models and represent a promising approach for the treatment of cancer.

Citation Format: Xiao Hu, Jacques Moisan, Charles Lesch, Yahong Wang, Xikui Liu, Rodney Morgan, David Mertz, Brian Sanchez, Dick Bousley, Clark Taylor, Chad Van Huis, Thomas Aicher, Peter Toogood, Weiping Zou, Gary Glick, Laura L. Carter. RORγ agonists as a novel immunotherapy approach for 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 4273. doi:10.1158/1538-7445.AM2015-4273

Novel RORgamma agonists enhance anti-tumor activity of adoptive T cell therapy (TUM2P.1010)

Adoptive cell transfer (ACT) therapy using tumor infiltrating lymphocytes (TILs) or T cells modified to express chimeric antigen receptors is a promising anti-cancer approach. Evidence suggests that Th17 or Tc17 cells display superior anti-tumor activity over unpolarized T cells commonly used in ACT clinical trials. As an approach to improve the potency and persistence of ACT, synthetic RORɣ agonists were designed to bolster the generation of type 17 cells. In vitro stimulation in the presence of RORɣ agonists modulates expression of costimulatory and coinhibitory molecules and increases IL-17A, IL-22 and GM-CSF production while maintaining IFNɣ production. Additional investigation revealed that treating tumor-specific Th0, Th17, Tc0 or Tc17 T cells with a RORɣt agonist in vitro significantly enhanced their ability to regress large and established EG.7 lymphoma and B16F10 melanoma tumors in vivo. Animals receiving RORɣ agonist-treated T cells had increased frequency of transferred cells, elevated IL-17A levels and decreased PD-1 expression in tumors and spleen compared to control animals. Previous studies have also shown that systemic delivery of an RORɣ agonist can also enhance anti-tumor immune response in syngeneic pre-clinical tumor models. By enhancing cytokine/chemokine production, promoting survival as well as decreasing PD-1 expression, RORɣ agonist molecules provide an effective means to enhance the potency of adoptively transferred T cell products.