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.

Novel Piperidinyl-Azetidines as Potent and Selective CCR4 Antagonists Elicit Antitumor Response as a Single Agent and in Combination with Checkpoint Inhibitors

The C-C chemokine receptor 4 (CCR4) is broadly expressed on regulatory T cells (T_reg) as well as other circulating and tissue-resident T cells. T_reg can be recruited to the tumor microenvironment (TME) through the C-C chemokines CCL17 and CCL22. T_reg accumulation in the TME has been shown to dampen the antitumor immune response and is thought to be an important driver in tumor immune evasion. Preclinical and clinical data suggest that reducing the T_reg population in the TME can potentiate the antitumor immune response of checkpoint inhibitors. We have developed small-molecule antagonists of CCR4, featuring a novel piperidinyl-azetidine motif, that inhibit the recruitment of T_reg into the TME and elicit antitumor responses as a single agent or in combination with an immune checkpoint blockade. The discovery of these potent, selective, and orally bioavailable CCR4 antagonists, and their activity in in vitro and in vivo models, is described herein.

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.

Alcohol-related harm in emergency departments: a prospective, multi-centre study

BACKGROUND AND AIMS

Emergency department (ED) alcohol-related presentation data are not routinely collected in Australia and New Zealand. It is likely that previous research has underestimated the numbers of patients presenting with alcohol-related conditions. This study aimed to quantify the level of alcohol harm presenting to EDs in Australia and New Zealand [Correction added on 23 Jan 2018, after first online publication: The 'aims' section was missing and is updated in this version].

DESIGN

Multi-centre, prospective study. Patients were screened prospectively for alcohol-related presentations during a 7-day period in December 2014. Part 1 involved screening to determine alcohol-positive ED presentations and data collection of patient demographic and clinical information. Part 2 involved a consent-based survey conducted with patients aged ≥ 14 years to perform Alcohol Use Disorders Identification Test (AUDIT) scores.

SETTING

Eight EDs in Australia and New Zealand, representing differing hospital role delineations.

PARTICIPANTS

A total of 8652 patients aged ≥ 14 years attended and 8435 (97.5%) were screened.

MEASUREMENTS

The main outcome measure was the proportion of patients who had an alcohol-related presentation termed 'alcohol-positive', using pre-defined criteria. It included injuries, intoxication, medical conditions and injuries caused by an alcohol-affected third party. Secondary outcomes included demographic and clinical information, the type of alcohol-related presentations and AUDIT scores.

FINDINGS

A total of 801 [9.5%; 95% confidence interval (CI) = 8.9-10.1%] presentations were identified as alcohol-positive, ranging between 4.9 and 15.2% throughout sites. Compared with alcohol-negative patients, alcohol-positive patients were more likely to be male [odds ratio (OR) = 1.90, 95% CI = 1.63-2.21], younger (median age 37 versus 46 years, P < 0.0001), arrive by ambulance (OR = 1.94, 95% CI = 1.68-2.25) or police/correctional vehicle (OR = 4.56, 95% CI = 3.05-6.81) and require immediate treatment (OR = 3.20, 95% CI = 2.03-05.06). The median AUDIT score was 16 (interquartile range = 10-24).

CONCLUSIONS

Almost one in 10 presentations to emergency departments in Australia and New Zealand are alcohol related.

Abstract 4600: Potent and selective C-C chemokine receptor (CCR4) antagonists potentiate anti-tumor immune responses by inhibiting regulatory T cells (Treg)

Naturally suppressive CD4+ Foxp3+ Treg are essential for immune tolerance. Although Treg-mediated suppression of effector cells is important to control inflammation and prevent autoimmune diseases, the presence of Treg in the tumor microenvironment (TME) has been shown to dampen anti-tumor immune responses. Human Treg express CCR4, the receptor for the chemokines CCL17 and CCL22. These chemokines are produced by tumor cells, tumor-associated macrophages and dendritic cells, as well as by effector T cells (Teff). Preclinical and clinical data supports a role for CCR4-mediated recruitment and accumulation of Treg in the TME which can be associated with poor prognosis. Further, recent longitudinal studies in patients receiving IO agents demonstrate an influx of Treg in responding patients which may dampen optimal anti-tumor responses. Therefore, CCR4 is an ideal target to selectively block Treg recruitment into the TME.

We have developed structurally unique series of small molecule antagonists of CCR4. These antagonists have cellular potencies in multiple assays (e.g. chemotaxis of primary human Treg in 100% serum) in the low double-digit nM range. Representative compounds are selective against other chemokine receptors, GPCRs and ion channels, including the hERG channel, and lack inhibition of common human CYP450 enzymes. Moreover, compounds have excellent in vitro and in vivo ADME properties, consistent with convenient oral dosing. In preclinical syngeneic tumor models, these CCR4 antagonists block Treg migration and support expansion of activated Teff. In contrast to the non-selective approach of depleting anti-CCR4 antibodies, our compounds reduce Treg in the tumor, but not in peripheral tissues such as blood, spleen or skin. In preclinical efficacy studies, CCR4 antagonists potentiate the anti-tumor effects of various checkpoint inhibitors and immune stimulators such as anti-PD-L1 and anti-CD137 antibodies. We observe enhanced tumor growth inhibition and increased tumor regressions when these agents are combined with CCR4 antagonists, without any gross toxicity. Further characterization of these CCR4 antagonists and their anti-tumor effects will be described.

Citation Format: Oezcan Talay, Lisa Marshall, Cesar Meleza, Maureen K. Reilly, Omar Robles, Mikhail Zibisky, Abood Okal, Lisa Seitz, Jenny McKinnell, Scott Jacobson, Erin Riegler, Emily Karbaz, David Chian, Angela Wadsworth, Paul Kassner, David Wustrow, Jordan S. Fridman. Potent and selective C-C chemokine receptor (CCR4) antagonists potentiate anti-tumor immune responses by inhibiting regulatory T cells (Treg) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4600. doi:10.1158/1538-7445.AM2017-4600

Reduced voltage losses yield 10% efficient fullerene free organic solar cells with >1 V open circuit voltages

Optimization of the energy levels at the donor-acceptor interface of organic solar cells has driven their efficiencies to above 10%. However, further improvements towards efficiencies comparable with inorganic solar cells remain challenging because of high recombination losses, which empirically limit the open-circuit voltage (V_oc) to typically less than 1 V. Here we show that this empirical limit can be overcome using non-fullerene acceptors blended with the low band gap polymer PffBT4T-2DT leading to efficiencies approaching 10% (9.95%). We achieve V_oc up to 1.12 V, which corresponds to a loss of only E_g/q - V_oc = 0.5 ± 0.01 V between the optical bandgap E_g of the polymer and V_oc. This high V_oc is shown to be associated with the achievement of remarkably low non-geminate and non-radiative recombination losses in these devices. Suppression of non-radiative recombination implies high external electroluminescence quantum efficiencies which are orders of magnitude higher than those of equivalent devices employing fullerene acceptors. Using the balance between reduced recombination losses and good photocurrent generation efficiencies achieved experimentally as a baseline for simulations of the efficiency potential of organic solar cells, we estimate that efficiencies of up to 20% are achievable if band gaps and fill factors are further optimized.

Survey of alcohol-related presentations to Australasian emergency departments

OBJECTIVE

To determine the proportion of alcohol-related presentations to emergency departments (EDs) in Australia and New Zealand, at a single time point on a weekend night shift.

DESIGN, SETTING AND PARTICIPANTS

A point prevalence survey of ED patients either waiting to be seen or currently being seen conducted at 02:00 local time on 14 December 2013 in 106 EDs in Australia and New Zealand.

MAIN OUTCOME MEASURES

The number of ED presentations that were alcohol-related, defined using World Health Organization ICD-10 codes.

RESULTS

At the 106 hospitals (92 Australia, 14 New Zealand) that provided data, 395 (14.3%; 95% CI, 13.0%-15.6%) of 2766 patients in EDs at the study time were presenting for alcohol-related reasons; 13.8% (95% CI, 12.5%-15.2%) in Australia and 17.9% (95% CI, 13.9%-22.8%) in New Zealand. The distribution was skewed left, with proportions ranging from 0 to 50% and a median of 12.5%. Nine Australian hospitals and one New Zealand hospital reported that more than a third of their ED patients had alcohol-related presentations; the Northern Territory (38.1%) and Western Australia (21.1%) reported the highest proportions of alcohol-related presentations.

CONCLUSIONS

One in seven ED presentations in Australian and New Zealand at this 02:00 snapshot were alcohol-related, with some EDs seeing more than one in three alcohol-related presentations. This confirms that alcohol-related presentations to EDs are currently underreported and makes a strong case for public health initiatives.

THE NEUTRALIZATION OR DESTRUCTION OF DIPHTHERIA TOXIN BY TISSUE

As determined by the intracutaneous test in guinea pigs, diphtheria toxin is not altered in the presence of cardiac tissue obtained from the fetal or from the adult heart of the guinea pig. Tissue cultures were apparently uninjured by the presence of the toxin in the dilutions used in these experiments, and, when washed with embryo extract after removal of the diluted toxin, continued to grow. Embryonic guinea pig cardiac muscle tissue growing in cultures in vitro possesses the power of neutralizing, binding, or destroying diphtheria toxin so that it is no longer toxic for normal guinea pigs. Such neutralization takes place through the intervention of growing tissue and is a property which is lacking in similar surviving tissue not in a state of cultivation. Thus, it appears that the living, growing cells of the tissues neutralize or destroy limited quantities of toxin; only when the quantity of toxin exceeds a certain limit is its action injurious.

THE PURIFICATION AND CONCENTRATION OF DIPHTHERIA TOXOID

By precipitation with acetone at 4 degrees C. a refined diphtheria toxoid was obtained as a dry powder, readily soluble in aqueous solutions. The powder itself appears to be stable. When dissolved in half the original volume of physiological salt solution, the toxoid remained stable, in the cold room, for a period of 7 months. Only toxoids should be used which have been completely detoxified by the treatment with formalin. The formalin is immediately and completely removed by precipitation with acetone. Filtration through a Mandler filter or the addition of a preservative did not appear to have any deleterious effect. Incubating at 39 degrees C. and freezing for 20 hours did not impair its activities. The flocculating value of the purified toxoid containing phenol was almost completely destroyed by freezing, while when merthiolate was the preservative, it was unchanged. Approximately 62 per cent of the nitrogen was eliminated in the process with approximately 15 per cent loss in flocculating value. The flocculating values were nearly double those of the original material and thus corresponded with the concentration, which was onehalf the volume. By this method, the antigenic activity of a toxoid below standard may be increased to a satisfactory standard. The antigenic activity of the refined product in the immunization of guinea pigs may in general parallel its flocculating values but the relation between the results of these tests may not be proportional nor constant. As an immunizing agent in the guinea pig, the refined toxoid possesses an antigenic activity that is equal to, or greater than, that of the unconcentrated toxoid.

Decarboxylation of alpha-ketoisovaleric acid after oral administration in man

The keto analogues of essential amino acids represent a promising therapeutic modality in hereditary and acquired disorders of nitrogen metabolism. The utilization of these substances in humans has been assayed primarily by nitrogen balance studies. A simple and accurate breath excretion test for 14CO2 enabled us to measure the decarboxylation of 1-14C-alpha-ketoisovaleric acid (KIV, the keto analogue of valine) in two normal and six diseased subjects. Normal volunteers as well as patients with gastrectomy, hepatic failure, renal failure, and myotonic dystrophy were tested in 5-g protein diets supplemented with essential amino acids and KIV (in place of valine). The normal volunteers and the gastrectomy patient were then restudied on 120 g protein/day. With low protein intake, 13 to 32% of ingeted KIV underwent rapid decarboxylation, and this proportion appeared to correlate inversely with damage to organ systems containing the branched-chain keto acid dehydrogenase. With high protein intake, the proportion decarboxylated rose to 44 to 53%. Thse results confirm that the decarboxylation of KIV in man varies under different conditions of dietary intake and metabolic disease. The 14CO2 brewth excretion test is applicable to other related analyses of carboxylic acid metabolism in human subjects.

The Lipid Content of Livers of Non-Immunized and Immunized Horsse

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