Discovery of LYC-55716: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ) Agonist for Use in Treating Cancer.

Retinoic acid receptor-related orphan receptor γ (RORc, RORγ, or NR1F3) is the nuclear receptor master transcription factor that drives the function and development of IL-17-producing T helper cells (Th17), cytotoxic T cells (Tc17), and subsets of innate lymphoid cells. Activation of RORγ+ T cells in the tumor microenvironment is hypothesized to render immune infiltrates more effective at countering tumor growth. To test this hypothesis, a family of benzoxazines was optimized to provide LYC-55716 (37c), a potent, selective, and orally bioavailable small-molecule RORγ agonist. LYC-55716 decreases tumor growth and enhances survival in preclinical tumor models and was nominated as a clinical development candidate for evaluation in patients with solid tumors.

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.

Junctional adhesion molecule-C is a soluble mediator of angiogenesis.

Junctional adhesion molecule-C (JAM-C) is an adhesion molecule expressed by endothelial cells (ECs) that plays a role in tight junction formation, leukocyte adhesion, and transendothelial migration. In the current study, we investigated whether JAM-C is found in soluble form and whether soluble JAM-C (sJAM-C) mediates angiogenesis. We found that JAM-C is present in soluble form in normal serum and elevated in rheumatoid arthritis (RA) serum. The concentration of sJAM-C is also elevated locally in RA synovial fluid compared with RA serum or osteoarthritis synovial fluid. sJAM-C was also present in the culture supernatant of human microvascular ECs (HMVECs) and immortalized human dermal microvascular ECs, and its concentration was increased following cytokine stimulation. In addition, sJAM-C cleavage from the cell surface was mediated in part by a disintegrin and metalloproteinases 10 and 17. In functional assays, sJAM-C was both chemotactic and chemokinetic for HMVECs and induced HMVEC tube formation on Matrigel in vitro. Neutralizing anti-JAM-C Abs inhibited RA synovial fluid-induced HMVEC chemotaxis and sJAM-C-induced HMVEC tube formation on Matrigel. sJAM-C also induced angiogenesis in vivo in the Matrigel plug and sponge granuloma models. Moreover, sJAM-C-mediated HMVEC chemotaxis was dependent on Src, p38, and PI3K. Our results show that JAM-C exists in soluble form and suggest that modulation of sJAM-C may provide a novel route for controlling pathological angiogenesis.

Phenotypic and functional analysis of murine resident and induced peritoneal macrophages.

Primary macrophages from the peritoneal cavities of mice are commonly used ex vivo to produce inflammatory cytokines and test anti-inflammatory agents. Although approximately 1 million peritoneal macrophages can be obtained from an untreated mouse, more than twice that number can be collected 48 to 72 h after intraperitoneal injection of sterile inducing agents such as Brewer thioglycollate broth, casein, and proteose peptone. However, whether 'induced' macrophages are functionally equivalent to 'resident' peritoneal macrophages has been unclear. Flow cytometric analysis revealed significant phenotypic differences between these 2 macrophage types. Resident and induced peritoneal macrophages also demonstrated markedly different capacities to produce the inflammatory cytokines interleukins 6 and 1beta in response to lipopolysaccharide stimulation in vitro. Increased understanding of the differences between resident and induced peritoneal macrophages likely will help investigators decide which macrophage type is appropriate for their in vitro assay needs.