Tumors establish resistance to immunotherapy by regulating Treg recruitment via CCR4

BACKGROUND

Checkpoint inhibitors (CPIs) such as anti-PD(L)-1 and anti-CTLA-4 antibodies have resulted in unprecedented rates of antitumor responses and extension of survival of patients with a variety of cancers. But some patients fail to respond or initially respond but later relapse as they develop resistance to immune therapy. One of the tumor-extrinsic mechanisms for resistance to immune therapy is the accumulation of regulatory T cells (T_reg) in tumors. In preclinical and clinical studies, it has been suggested that tumor trafficking of T_reg is mediated by CC chemokine receptor 4 (CCR4). Over 90% of human T_reg express CCR4 and migrate toward CCL17 and CCL22, two major CCR4 ligands that are either high at baseline or upregulated in tumors on CPI treatment. Hence, CCR4 antagonism has the potential to be an effective antitumor treatment by reducing the accumulation of T_reg into the tumor microenvironment (TME).

METHODS

We developed in vitro and in vivo models to assess T_reg migration and antitumor efficacy using a potent and selective CCR4 antagonist, CCR4-351. We used two separate tumor models, Pan02 and CT26 mouse tumors, that have high and low CCR4 ligand expression, respectively. Tumor growth inhibition as well as the frequency of tumor-infiltrating T_reg and effector T cells was assessed following the treatment with CCR4 antagonist alone or in combination with CPI.

RESULTS

Using a selective and highly potent, novel small molecule inhibitor of CCR4, we demonstrate that migration of CCR4⁺ T_reg into the tumor drives tumor progression and resistance to CPI treatment. In tumor models with high baseline levels of CCR4 ligands, blockade of CCR4 reduced the number of T_reg and enhanced antitumor immune activity. Notably, in tumor models with low baseline level of CCR4 ligands, treatment with immune CPIs resulted in significant increases of CCR4 ligands and T_reg numbers. Inhibition of CCR4 reduced T_reg frequency and potentiated the antitumor effects of CPIs.

CONCLUSION

Taken together, we demonstrate that CCR4-dependent T_reg recruitment into the tumor is an important tumor-extrinsic mechanism for immune resistance. Blockade of CCR4 led to reduced frequency of T_reg and resulted in increased antitumor activity, supporting the clinical development of CCR4 inhibitors in combination with CPI for the treatment of cancer.

STATEMENT OF SIGNIFICANCE

CPI upregulates CCL17 and CCL22 expression in tumors and increases T_reg migration into the TME. Pharmacological antagonism of the CCR4 receptor effectively inhibits T_reg recruitment and results in enhanced antitumor efficacy either as single agent in CCR4 ligand^high tumors or in combination with CPIs in CCR4 ligand^low tumors.

Abstract 1646: Development of small-molecule HPK1 inhibitors to unleash tumor-specific T cell responses

Hematopoietic progenitor kinase 1 (HPK1) is an intracellular protein kinase that negatively regulates T cell signaling and proliferation. Upon T cell receptor (TCR) activation, active HPK1 phosphorylates the adaptor protein SLP76 in the TCR complex, recruiting the negative regulator 14-3-3 and targeting components of the TCR signaling complex for degradation. HPK1 thus limits the TCR signaling important for mounting an effective immune response against tumor cells. We are employing structure-guided drug design to develop potent small-molecule inhibitors of HPK1. Our compounds potently inhibit HPK1 in biochemical assays, reduce levels of phosphorylated SLP76 and concomitantly increase IL-2 production by Jurkat T cells. Importantly, our HPK1 inhibitors enhance cytokine production by human and mouse primary T cells above that observed with TCR activation alone. Treatment of mice with orally available HPK1 inhibitors results in increased activation of antigen-specific CD8+ T cells in vivo and decreased tumor growth as single agent and in combination with clinically relevant checkpoint inhibitor antibodies. Our work confirms the importance of HPK1 for T cell function and supports HPK1 as a promising next generation immuno-oncology target.

Citation Format: George Katibah, Yamini Ohol, Cyril Bucher, Lavanya Adusumilli, Deepika Kaveri, Omar Robles, Michael Sun, Cynthia Cho, Heather Milestone, Rachel Ames, Scott Jacobson, Dan Nebalasca, Justy Gomez- Guagua, Jerick Sanchez, Molly Grandcolas, Steve Wong, Martin Brovarney, Chandru Ramana, Thant Zaw, Lan Nguyen, Parcharee Tivitmahaisoon, Andrew Ng, Anqi Ma, Blanca Gomez, Michelle Ko, Paul Leger, Jeffrey Jackson, Grant Shibuya, Anton Shakhmin, Delia Bradford, Mengshu Xu, Mikhail Zibinsky, Daniel Poon, David Wustrow, Paul Kassner, Dirk Brockstedt. Development of small-molecule HPK1 inhibitors to unleash tumor-specific T cell responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1646.

FLX193: A Potent, Selective CCR4 Antagonist for Allergic Disorders

Type 2 helper T cells (Th2)cells have been shown to express CCR4 receptor, and play a critical role in driving the pathogenesis of asthma and atopic dermatitis. FLX193 is a best-in-class, highly-potent and selective small molecule CCR4 antagonist under investigation for the treatment of allergic disorders. FLX193 blocked migration of CCR4+ Th2 cells (human and mouse) towards CCL17 and CCL22 in an in vitro chemotaxis assay. FLX193 is well-tolerated in animals at efficacious doses. In an Ovalbumin (OVA)-induced asthma model, FLX193 significantly reduced lymphocyte and eosinophil counts in the Bronchoalveolar lavage (BAL) fluid and showed a reduction of the effector Th2-relevant cytokines IL-5 and IL-13. FLX193 treatment also reduced the levels of CCL17 and CCL22 in the BAL fluid, indicating an overall reduction of inflammation. In addition, we used an atopic dermatitis mouse model to demonstrate that treatment with FLX193 decreased CCR4+ T-cell mediated inflammation. Hence, FLX193 shows promise in the treatment of atopic dermatitis.

Abstract 2915: Discovery and optimization of potent and selective inhibitors of USP7 to enhance anti-tumor immunity and target tumor growth

USP7 is a deubiquitinase (DUB) that has attracted much attention recently due to its multiple roles in promoting cancer progression. By removal of ubiquitin from protein substrates, USP7 stabilizes oncogenes such as MDM2 and Myc, destabilizes and inactivates the key tumor suppressors p53 and PTEN, and imparts resistance to DNA-damaging chemotherapy by enhancing DNA repair responses. USP7 plays an important role in suppression of immune responses in the tumor microenvironment by stabilizing the transcription factor FOXP3 and thereby enhancing the suppressive function of regulatory T cells. Thus, inhibition of USP7 is an appealing therapeutic strategy because it has the potential to impact important oncology targets such as transcription factors that have been widely viewed as undruggable. We employed structure-based and other medicinal chemistry techniques to enable the design of potent and selective USP7 inhibitors. Using a high-throughput assay of DUB activity employing rhodamine-labeled ubiquitin, we optimized several series of reversible USP7 inhibitors to sub-100 pM potency and selectivity of >10,000-fold over all other DUBs. Cellular activity was demonstrated using a luciferase reporter gene assay of p53 activation, revealing compounds with EC50 values ranging down to 20 nM. To assess the role of USP7 inhibition in enhancement of immune responses, we determined relief of suppression of effector T cells in vitro. Effector T cells (CD8+) were co-cultured with regulatory T cells (CD4+ FOXP3+) and antigen-presenting cells for 4 days, after which CD8+ cell proliferation was determined by flow cytometry. Treatment with USP7 inhibitors during co-culture resulted in relief of regulatory T cell suppression of CD8+ cell proliferation. In vivo enhancement of immune responses was assessed in rodent models of inflammation and tumor growth. Direct effects on tumor cell growth and viability were explored by profiling cytotoxicity of USP7 inhibitors as single agents and in combination with chemotherapeutic agents in a broad range of cancer cell lines. In preparation for future clinical development, compounds were modified to obtain desirable in vitro and in vivo ADME and toxicity profiles. Following extensive pre-clinical optimization, we have in hand orally bioavailable compounds with high permeability, low clearance, and minimal off-target activity.

Citation Format: Betty Abraham, Lavanya Adusumilli, Berenger Biannic, Delia Bradford, Martin Brovarney, David Chian, Gene Cutler, Xinping Han, Dennis Hu, Scott Jacobson, Sherra Johnson, Paul Kassner, Deepika Kaveri, John Ketcham, Andrea Kim, Paul Leger, Lisa Marshall, Sachie Marubayashi, Jack Maung, Jenny McKinnell, Cesar Meleza, Yamini Ohol, Akinori Okano, Leanne Peiser, Deepa Pookot, Payal Rana, Jacob Schwarz, Nick Shah, Grant Shibuya, Michael Sun, Silpa Suthram, Oezcan Talay, Angela Wadsworth, David Wustrow, Kyle Young, Andrew Napper. Discovery and optimization of potent and selective inhibitors of USP7 to enhance anti-tumor immunity and target tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2915.

Effects of LTB4 receptor antagonism on pulmonary inflammation in rodents and non-human primates

Asthma, chronic obstructive pulmonary disease (COPD) and acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are characterized by neutrophilic inflammation and elevated levels of leukotriene B4 (LTB4). However, the exact role of LTB4 pathways in mediating pulmonary neutrophilia and the potential therapeutic application of LTB4 receptor antagonists in these diseases remains controversial. Here we show that a novel dual BLT1 and BLT2 receptor antagonist, RO5101576, potently inhibited LTB4-evoked calcium mobilization in HL-60 cells and chemotaxis of human neutrophils. RO5101576 significantly attenuated LTB4-evoked pulmonary eosinophilia in guinea pigs. In non-human primates, RO5101576 inhibited allergen and ozone-evoked pulmonary neutrophilia, with comparable efficacy to budesonide (allergic responses). RO5101576 had no effects on LPS-evoked neutrophilia in guinea pigs and cigarette smoke-evoked neutrophilia in mice and rats. In toxicology studies RO5101576 was well-tolerated. Theses studies show differential effects of LTB4 receptor antagonism on neutrophil responses in vivo and suggest RO5101576 may represent a potential new treatment for pulmonary neutrophilia in asthma.