P1, N=0, Withdrawn, Ikena Oncology | Phase classification: P1b --> P1 | N=54 --> 0 | Trial completion date: Jul 2025 --> Apr 2023 | Not yet recruiting --> Withdrawn | Trial primary completion date: Jul 2024 --> Apr 2023

P1, N=78, Completed, Ikena Oncology | Recruiting --> Completed | Trial completion date: Sep 2022 --> Jul 2023 | Trial primary completion date: Sep 2022 --> Jul 2023

P1/2, N=125, Not yet recruiting, Dong-A ST Co., Ltd.

PHGDH knockdown induced CRC cell sensitivity to stemregenin 1 via the autophagy pathway. Our findings suggest that PHGDH modulates AhR signaling and the redox-dependent autophagy pathway in CRC, and that the combination of inhibition of both PHGDH and AhR may be a novel therapeutic strategy for CRC.

The results indicate that correction of aberrant tryptophan catabolism in fibroids could be an effective treatment through its effect to reduce cell proliferation and ECM accumulation.

The aryl hydrocarbon receptor (AhR) antagonist CH223191 promoted, whereas the p38 inhibitor SB203580 suppressed the increase in TNFα mRNA and protein expression induced by skatole in intestinal epithelial Caco-2 cells. The c-Jun N-terminal kinase (JNK) inhibitor SP600125 repressed only the increased TNFα protein expression, whereas the extracellular signal-regulated kinase (ERK) pathway inhibitor U0126 did not affect increased TNFα expression at any level...Overall, these results suggested that TNFα expression is increased by the concerted actions of skatole-activated p38 and JNK, and that TNFα exerts autocrine/paracrine actions on IECs despite partial suppression by activated AhR. Therefore, skatole might play an important role in the development and progression of IBD and CRC via increased TNFα expression.

Here, we propose that a best-in-class AhR inhibitor, DA-4505, improves anti-tumor efficacy via modulation of tumor immune surveillance compared to BAY2416964, an AHR antagonist drug candidate being studied in the clinical phase. To evaluate anti-tumor effects of DA-4505 and BAY2416964, the two AhR inhibitors were dosed at 10 mg/kg once daily alone or in combination with aPD-1 (10 mg/kg) in surgical and chemotherapy models, and a PDX model (YHIM2004)...A tumor reduction was shown by treating DA-4505 alone or in combination with pembrolizumab compared to vehicle group (P<0.05)... The AhR inhibitor DA-4505 demonstrated an improvement in anti-tumor efficacy. In addition, it has shown a synergistic effect when combined with aPD-1. Discoveries from this study provide a preclinical rationale for future clinical implications in solid tumor.

Additionally, the AHR inhibitor (CH-223191) abrogated AHR activity and subsequent luminescence below control threshold...Future experiments will focus on using our reporter construct in the context of ICB treatment and assessing AHR activity overtime as well as sampling peripheral blood to assess the magnitude of tryptophan, kyn, and other polycyclic hydrocarbons including gut microbiome-derived indoles. The characterization of the IDO-Kyn-AhR modulation after therapeutic intervention will inform the rational design of treatment regimens to abrogate immune suppression associated with AHR activity in combination with ICB treatment.

P1, N=143, Recruiting, Bayer | Trial completion date: Jan 2024 --> Jun 2025 | Trial primary completion date: Nov 2023 --> Mar 2025

The pharmacological inhibition of AhR, by CH223191, suppressed cell death signs and increased cell viability...Fascinatingly, during CCoV infection, a novel co-expression of NP and AhR expression was found. Taken together, our preliminary findings show that infection with CCoV activates AhR, and pharmacologic AhR inhibition reduces CCoV replication, identifying AhR as a possible candidate target for CCoV antiviral therapy.

We ranked the highest and lowest 10% expression levels of AHR by RNA expression (RPKM) across all samples in the Beat AML dataset and evaluated their mutation profiles. Ranking the mutations based on frequency we found an enrichment of mutations in NPM1, IDH2, IDH1, PML-RARA and FLT3-ITD in the low AHR expression group compared to the high expression group (Figure1A). AHR high patients had higher frequencies of CBF-MYH11, DNMT3A, FLT3 point mutations, NRAS, KRAS and BCOR mutations, compared to AHR low expressors.

This is the first study to report crosstalk between AhR and BCL-2 in breast CSCs and provides the rationale for using a combined treatment of BCL-2 inhibitor and AhR antagonist for more effective cancer prevention and treatment.

Knocking down CYP1A1 or inactivating AKT signaling by LY294002 downregulated the p-AKT , inhibited cell proliferation, and compromised the proliferation effect induced by Fn in both in vitro and in vivo experiments. Inactivating the aryl hydrocarbon receptor(AHR)by CH-223191, reversed CYP1A1 expression induced by Fn, and inhibited the proliferation of ESCC cells. Taken together, our findings indicate that Fn may promote ESCC cell proliferation via AHR/CYP1A1/AKT signaling. Targeting Fn or AHR/ CYP1A1 signaling could yield approaches relevant to the treatment of ESCC.

The cell migration was increased in a time- and concentration- dependent manner, and was blocked by AhR antagonist (CH223191)...Furthermore, two promigratory genes (CFL2 and NRP1) induced by TCDD was reversed by blockade of AhR. In conclusion, AhR-mediated mRNA-miR networks in the axon guidance pathway may represent a potential molecular mechanism of dioxin-induced directional migration of human neuroblastoma cells.

These studies provide rationale for targeting AHR in cancer patients. IK-175 is being evaluated in a Phase 1 clinical trial in patients with advanced solid tumors.

P1b, N=54, Not yet recruiting, Ikena Oncology

Urolithin A attenuated the pro-inflammatory factors production (IL-6, IL-1β, NOS2 and others) in vitro studies. Oral urolithin A treatment caused prominent anticancer and anti-inflammatory action in various in vivo studies, including colitis rat model, carrageenan-induced paw edema mice model, models of pancreatic cancer, and models of obesity. The main molecular mechanisms of these effects might be the modulation of aryl hydrocarbon receptors, which antagonism may lead to decreasing of chronic inflammation. Other primary targets of urolithin A might be the processes of protein phosphorylation (for instance, it decreases the phosphorylation of protein kinase B) and p53 stabilization. Anti-inflammatory effects of urolithin A can be reached in physiologically relevant concentrations. This might be of vital importance for preventing immune suppression, associated with chronic inflammation in cancer. Considering the favorable urolithin A safety profile, it is the promising compound for cancer treatment and prevention.

Our study indicates that this gene can be critical for attachment and activation of the Wnt pathway. Genes activated by AHR are crucial for multiple aspects of carcinogenesis and suggests that targeting AHR by using AHR antagonists could have therapeutic value by limiting cell growth.

Sorafenib's antagonistic action on AhR was comparable to that of the known AhR antagonist CH-223191 in human liver and ovarian cell lines. Moreover, sorafenib offers potential benefit for diseases treatable through AhR suppression strategies. Further investigation is warranted into sorafenib's AhR antagonistic behavior.

Interferon (IFN)-γ induces IDO1 expression through the Jak/STAT1 pathway and mediates Kyn production concomitantly with Trp consumption in CLL-conditioned media, while INCB018424 (ruxolitinib), a JAK1/2 inhibitor, impaired both effects...Moreover, Kyn-treated CLL cells are less affected by the pro-apoptotic effect of ABT-199 (venetoclax), while CH-223191 showed synergistic/additive cytotoxicity with this drug. Lastly, targeting directly MCL1 in CLL cells with AMG-176, we abrogate the pro-survival effect of Kyn. In conclusion, our data identify IDO1/Kyn/AHR signaling as a new therapeutic target for CLL, describing for the first time its role in CLL pathobiology.

The reduction was also prevented by pretreatment with the AhR antagonist CH-223191. Identification of clozapine as a ligand for the AhR opens new perspectives to explain common clozapine therapy-associated adverse effects at the molecular level.

P1, N=141, Recruiting, Bayer | Trial completion date: Jun 2023 --> Jan 2024 | Trial primary completion date: Apr 2023 --> Nov 2023

Rescue studies showed that the dedifferentiation activity of AhR was modulated by the circSH2B3/miR-4640-5p/IGF2BP2 axis. Our findings confirmed for the first time that AhR antagonists promote differentiation of PTC via inhibiting the circSH2B3/miR-4640-5p/IGF2BP2 axis, offering a novel therapeutic approach and a potential marker for differentiation of PTC.

Using the specific inhibitor CH223191, we showed that the induction of CYP1A was dependent on the AhR both in vitro using multiple CRC cell lines as in vivo using wild-type C57bl6 mice colonized with S. gallolyticus...This study shows that gut bacteria have the potential to modulate the expression of biotransformation pathways in colonic epithelial cells in an AhR-dependent manner. This offers a novel theory on the contribution of intestinal bacteria to the etiology of CRC by modifying the capacity of intestinal epithelial or (pre-)cancerous cells to (de)toxify dietary components, which could alter intestinal susceptibility to DNA damaging events.

The highest and lowest 10% expression levels of AHR in all samples in Beat AML were evaluated for mutation profiles. Ranking the top 18 mutations based on frequency we found an enrichment of FLT3 mutations in the high AHR expression group compared to the lower expression group (Figure 1A). ELN risk did not correlate with AHR expression however FAB classification M0/M1 and M4/M5 monocytic subtypes had higher AHR expression than M3 FAB subtype (Figure 2A).

IK-175 is being evaluated in an ongoing phase 1 clinical study as a single agent and in combination with nivolumab for bladder cancer patients (NCT04200963). Conclusions A novel and robust nuclear AHR IHC assay for bladder cancer was developed and analytically validated in a CLIA certified lab and showed ≥95% accuracy, specificity, sensitivity, and precision, enabling its implementation in an IK-175 Ph1b clinical study (NCT04200963) for prospective patient enrichment. Trial Registration NCT04200963

Furthermore, our findings indicate that AHR antagonism may represent an effective means to enhance the function of other drugs, such as anti-CD38 antibodies, in future clinical studies. Taken together, these data identify AHR as a novel target for MM therapy.

We determined that activation of the aryl hydrocarbon receptor (AHR) by kynurenine induced PD-1 expression, and this effect was significantly abrogated by the AHR antagonist CH223191. Mechanistically, kynurenine alters chromatin accessibility in regulatory regions of T cell inhibitory receptors, allowing AHR to bind to consensus XRE motifs in the promoter region of PD-1. These results enable the design of strategies to target the IDO1 and AHR pathways for enhancing anti-tumor immunity in ovarian cancer.

Analyzing the anti-apoptotic proteins of the Bcl2 family after Kyn treatment, we found the induction of Mcl1, that was affected by adding CH-223191, an antagonist of AhR. Conclusion Our data demonstrated that IDO-Kyn-AhR axis is active in CLL cells and promotes Mcl1 expression,sustaining the survival of leukemic cells. Our results indicated the KP as a new potential therapeutic target in the CLL microenvironment.

This study helps us to understand why CPA induces acute hepatitis, gene mutation, and many other side effects. In addition, it may trigger further studies investigating the relationships between CPA, glucocorticoid receptor and castration-resistant prostate cancer in the future.

LNCaP cells were treated with AST alone and in combination with CH223191 and flutamide (Flu) in the presence and absence of testosterone. So that, AST could prevent the growth of testosterone-dependent PCa cells, downregulate downstream genes in testosterone pathways, and enhance the metabolism of testosterone via AhR pathway. Collectively, AST could be considered as a potential candidate for the treatment of PCa.

Interestingly, the effects of HCA on the growth and death of HepG2 cells were inhibited by culturing with CH223191, an antagonist of aryl hydrocarbon receptor (AHR), suggesting that the flavonoid effects are, at least partly, mediated by activation of AHR signaling...Thus, our study demonstrates that HCA suppresses the growth and stimulates the death of human liver cancer HepG2 cells in vitro. The botanical molecule HCA may therefore be a useful tool in the treatment of HCC, providing a novel strategy for the therapy of human liver cancers.

We also examined therapeutic strategies targeting the AhR signalling pathway and their possible adverse effects. Since the end of 2019, two phase I clinical trials have investigated the ability of the AhR antagonist to 'reset' the immune system and re-sensitize the cancer cells to therapies by preventing their dedifferentiation.

Significant reductions in cell survival, mutagenic activity, Cyclin D1, CDK4, Snail, and JAK2/STAT3 expression were found after inhibitor AG490, ANF and CHJ223191 treatment. These findings reveal that BaP enhances the proliferative and mutagenic activity via JAK2-STAT3 pathway in PC-3 cells, and provide the additional evidence to understand the crucial role of BaP in prostate cancer carcinogenesis.

P1, N=174, Recruiting, Bayer | N=114 --> 174

Finally, AHR inhibition with a nanoparticle-delivered AHR antagonist or an inhibitor developed for human use limited ZIKV replication and ameliorated newborn microcephaly in a murine model. In summary, we identified AHR as a host factor for ZIKV replication and PML protein as a driver of anti-ZIKV intrinsic immunity.

Using ruxolitinib, an inhibitor of JAK-STAT pathway, we found that IFNγ induced IDO through STAT1 signaling...Analyzing the anti-apoptotic proteins of the Bcl2 family after Kyn treatment, we found the induction of Mcl1, that was affected by adding CH-223191, an antagonist of AHR... Our data demonstrate the constitutive expression of IDO and AHR in CLL cells. Furthermore, the tumor microenvironment promotes the induction of IDO and AHR through a complex signaling crosstalk with leukemic cells. Our findings underline that IDO-Kyn-AHR axis is active in CLL cells and promotes Mcl1 expression, sustaining the survival of CLL cells.

Pharmacological inhibition of the pregnane-X receptor using CH223191 and the aryl-hydrocarbon receptor using ketoconazole diminished the IS-elicited effects, suggesting that these receptors were the major receptors of IS in these models. Finally, we showed that increased expression of the human enzymes that form IS (Cyp2E1, Sult1A1, and Sult1A2) is associated with better survival in breast cancer, an effect that is lost in triple negative cases. Taken together, IS, similar to indolepropionic acid (another tryptophan metabolite), has cytostatic properties and higher expression of the metabolic machinery responsible for the formation of IS supports survival in breast cancer.

The antagonizing effect of coexposure led to the inhibition of the epithelial-mesenchymal transition (EMT) in MCF7 cells. Our study provides new evidence for the potential mechanisms involved in EDCs exposure and their interactions in EMT.

These results partially indicated that VPA may augment the PAH-mediated induction of CYP1B1 and CYP1A1 through the activation of transcription by HDAC inhibition.