The combination of IDO1 and HDAC inhibitors represents a promising strategy for CRC treatment, and NP-I/P is a candidate for clinical trials.

Linrodostat + nivolumab ± ipilimumab demonstrated a manageable safety profile. Kynurenine changes supported IDO1 pathway inhibition but did not correlate with response. A composite biomarker of low TDO2 expression plus high IFN-γ gene expression may predict response to linrodostat + nivolumab.

P1, N=17, Completed, National Cancer Institute (NCI) | Active, not recruiting --> Completed

Response-adaptive surgical timing enhanced treatment response. IDO-inhibitor BMS986205 augmented pTR in patients with high IDO1-expression in baseline samples, indicating a need for identifying and targeting resistant nodes to immunotherapy. HPV-status-dependent signatures predicting response to immunotherapy in HNSCC warrant further study.

Combined with favorable in vitro potency, pharmacokinetic profile, and in vivo efficacy, the promising antitumor drug candidate 11u has subsequently advanced into preclinical research. These compounds provide valuable ideas and information for developing new cancer immunotherapy.

P1/2, N=53, Completed, National Cancer Institute (NCI) | Active, not recruiting --> Completed

These macrophages carry a cargo of the TLR7/TLR8 agonist R848 and INCB024360, a selective indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor, wrapped in C16-ceramide-fused outer membrane vesicles (OMV) of Escherichia coli origin (RILO)...RILO-loaded macrophages exert therapeutic efficacy in mice bearing H22 hepatocellular carcinomas, which express high levels of glypican-3. Overall, we lay down the proof of principle for a cytotherapeutic strategy to target solid tumours and could complement conventional treatment.

Furthermore, AT-0174 treatment or AhR inhibitor significantly decreased TNBC anchorage-independent survival, invasive capacity, and expression of mesenchymal genes and protein, while exogenous KYN increased invasion through AhR-mediated ZEB1 expression. Thus, dual inhibition of TDO2/IDO1 may prove efficacious against TNBC progression.

IDO-producing tumors show a high total IDO immunostaining score, and thus, using IDO inhibitors, such as Epacadostat, Navoximod, and L isomer of 1-methyl-tryptophan, seems an important modality for cancer treatment...Antitumor effects of imatinib are enhanced by increasing T-cell effector function in the presence of IDO inhibition. Combining IDO targeting with chemotherapy, radiotherapy and/or immunotherapy, may be an effective tool against a wide range of malignancies. However, there are some controversial results regarding the efficacy of IDO1 inhibitors in cancer treatment.

The combination of the IDO1 inhibitor with CXCL10 or its agonist axitinib had a synergistic inhibitory effect on the growth of colon cancer cells and transplanted CT26 tumors...One being the Kyn-aryl hydrocarbon receptor (AHR) pathway, the other is the general control nonderepressible 2(GCN2). Our study provides a new reference for combination regimens of IDO1 inhibitors.

P1/2, N=255, Active, not recruiting, Bristol-Myers Squibb | Trial primary completion date: Apr 2024 --> Nov 2026

P1, N=18, Active, not recruiting, Northwestern University | Trial completion date: Jun 2025 --> Jun 2027 | Trial primary completion date: Feb 2024 --> Feb 2025

After disappointing results of the epacadostat as a selective IDO inhibitor in phase III clinical trials, there is much interest in the development of the TDO selective inhibitors. In addition, furo[2,3-c]pyridine-2,3-diamine was found as a common fragment for inhibition of the both targets and can be used in the design of the dual target inhibitors of the IDO and TDO. The new fragments introduced here can be a useful building blocks for incorporation into the selective TDO or dual IDO/TDO inhibitors.

P2, N=45, Terminated, Thomas Jefferson University | Trial completion date: Dec 2025 --> Jun 2024 | Active, not recruiting --> Terminated | Trial primary completion date: Dec 2025 --> Jun 2024; toxicity - per sponsor

IDO1 inhibitor RY103 showed positive anti-tumor efficacy, including the anti-angiogenesis effect and upregulation of natural killer cells in GL261 glioma-bearing mice. As expected, the combination of RY103 and anti-angiogenesis agent sunitinib was proved to be a better therapeutic strategy than either monotherapy.

Pembrolizumab plus epacadostat and pembrolizumab monotherapy provided a similar response rate to EXTREME and demonstrated a manageable safety profile in patients with R/M HNSCC.

Addition of epacadostat 100 mg BID to pembrolizumab and platinum-based chemotherapy was generally well tolerated but did not improve ORR in patients with treatment-naïve metastatic NSCLC. Evaluating epacadostat doses that normalize circulating kynurenine in combination with CPIs may help determine the clinical potential of this combination.

Treatment with epacadostat plus pembrolizumab resulted in a similar ORR and safety profile as placebo plus pembrolizumab in cisplatin-ineligible patients with previously untreated locally advanced/unresectable or metastatic UC. At a dose of 100 mg twice daily, epacadostat did not appear to completely normalize circulating kynurenine levels when administered with pembrolizumab. Larger studies with longer follow-up and possibly testing higher doses of epacadostat, potentially in different therapy settings, may be warranted.

Epacadostat plus pembrolizumab demonstrated anti-tumor activity and was generally tolerable as second-line treatment of patients with unresectable locally advanced or recurrent/progressive metastatic UC. Epacadostat 100 mg BID, when administered with pembrolizumab, did not normalize circulating kynurenine in most patients. Further study of combined IDO1/PD-L1 inhibition in this patient population, particularly with epacadostat doses that result in durable normalization of circulating kynurenine, may be warranted.

Addition of epacadostat to pembrolizumab therapy for PD-L1-high metastatic NSCLC was generally well tolerated but did not demonstrate an improved therapeutic effect. Evaluating higher doses of epacadostat that normalize kynurenine levels when given in combination with checkpoint inhibitors may be warranted.

AT-0174 exhibited an ideal profile for adjunct treatment of glioblastomas with the first-line chemotherapeutic drug temozolomide to prevent development of CD4+ Treg-mediated chemoresistance.

P2, N=14, Completed, National Cancer Institute (NCI) | Active, not recruiting --> Completed | Trial completion date: Sep 2024 --> Mar 2024

P2, N=24, Active, not recruiting, Memorial Sloan Kettering Cancer Center | Trial completion date: Sep 2024 --> Sep 2025 | Trial primary completion date: Sep 2024 --> Sep 2025

Histopathology analysis revealed a remarkable increase in the Trp concentration following combination treatment, while Kyn levels significantly decreased. Results showed that the nano-liposomal form of IDO1 inhibitor in combination with chemotherapy could significantly improve the imunity response and dominate the tumor immuno-suppressive micro-environment, which merits further investigations.

P2, N=1, Terminated, Columbia University | Completed --> Terminated; Study ended prematurely at the request of the funding sponsor.

P2, N=51, Active, not recruiting, Washington University School of Medicine | Trial primary completion date: Apr 2024 --> Jul 2024

P1/2, N=53, Active, not recruiting, National Cancer Institute (NCI) | Recruiting --> Active, not recruiting | N=113 --> 53

The combination of epacadostat plus pembrolizumab and chemotherapy was found to be tolerable in Japanese patients with advanced NSCLC.

P1, N=17, Active, not recruiting, National Cancer Institute (NCI)

The orally available dual IDO1/TDO2 inhibitor, AT-0174, significantly inhibited tumor progression, reduced tumor-associated macrophages, and reduced expression of immune-suppressive proteins on immune and tumor cells. These studies demonstrate the importance of TDO2 and the therapeutic potential of AT-0174 to overcome an immune-suppressed TME.

P2, N=30, Active, not recruiting, Memorial Sloan Kettering Cancer Center | Trial completion date: Jan 2024 --> Jan 2025 | Trial primary completion date: Jan 2024 --> Jan 2025

Consequently, this activation enables tumor cells to survive even in the face of heightened immune activity. These findings underscore the unforeseen adverse effects of apo-IDO1 inhibitors on tumor cells and highlight the potential of combining IL-6/JAK2/STAT3 inhibitors with apo-IDO1 inhibitors to improve their clinical efficacy.

Overall, our findings unveiled a new mechanism of action of epacadostat on IDO1 target, repositioning the catalytic inhibitor as a stabilizer of the apo-form of IDO1, still capable of transducing a pro-tumorigenic pathway in SKOV-3 tumor. This mechanism could contribute to clarify the lack of effectiveness of epacadostat in clinical trials and shed light on innovative immunotherapeutic strategies to tackle IDO1 target.

P3, N=861, Active, not recruiting, Bristol-Myers Squibb | Trial primary completion date: Nov 2023 --> Apr 2025

P3, N=89, Active, not recruiting, Incyte Corporation | Trial completion date: Dec 2023 --> Dec 2024

P1/2, N=113, Recruiting, National Cancer Institute (NCI) | Trial completion date: Dec 2023 --> Dec 2024 | Trial primary completion date: Dec 2023 --> Dec 2024

Efforts are underway to identify the proteome-wide direct target of BMS in CLL cells. In conclusion, our limited and preliminary data suggest that BMS could be considered as a potential therapeutic strategy to target CLL cells with a double hit: by blocking the pro-survival effect of BCR signaling, one of the driving forces for CLL cell survival and proliferation, and by inhibiting IDO1/kynurenine action to restore sensitivity to key leukemia treatments.

By co-encapsulating immunogenic dacarbazine, Epacasome further enhances anti-tumor effects and immune responses through the upregulation of NKG2D-mediated CTLs and natural killer cells responses particularly when combined with the PD-1 inhibitor in the late-stage metastatic B16-F10-Luc2 model in female mice. Furthermore, this combination prevents tumour recurrence and prolongs mouse survival in a clinically relevant, post-surgical melanoma model in female mice. Epacasome demonstrates potential to synergize with PD-1 blockade for improved response to melanoma immunotherapy.

The quantitative method was validated according to FDA, ICH and EMA guidelines, later applied: i) to assess the impact of selective inhibition of hIDO1 or hTDO (human tryptophan 2,3-dioxygenase) on the kynurenine pathway in A375 (melanoma), MDA-MB-231 (breast cancer), and U87 (glioblastoma) cell lines using multivariate analysis (MVA); ii) to determine the IC values of both well-known (i.e., epacadostat, linrodostat) and the novel hIDO1 inhibitor (i.e., BL5) in the aforementioned cell lines. The proposed LC-MS/MS method is reliable and robust. Furthermore, it is highly versatile and suitable for applications in the preclinical drug research and in vitro assays.

This study aims to investigate the regulatory effects of Astragalus polysaccharide(APS) and APS combined with 5-fluorouracil(5-FU) on indoleamine-2,3-dioxygenase(IDO1) in the colon tumor microenvironment...The APS + 5-FU group showed significantly reduced infiltration of CD4~+ T lymphocytes and increased infiltration of CD8~+ T lymphocytes. APS inhibited the expression of IDO1 in the colon tumor microenvironment to increase CD8~+ T lymphocyte infiltration, and the combination of APS with 5-FU demonstrated better effect.

P2, N=14, Active, not recruiting, National Cancer Institute (NCI) | Trial completion date: Mar 2024 --> Sep 2024

Our pre-clinical study suggests that epacadostat is a candidate HCC immuno-preventive agent to be considered for early clinical testing in NAFLD patients at risk of developing HCC.