By studying the turnover of IDO1 protein in human tumor cells exposed to various IDO1 catalytic inhibitors, such as epacadostat, linrodostat, and navoximod, we show here that these molecules stabilize a non-enzymatic protein conformation of IDO1, independently of their mechanism of inhibition. In the thyroid carcinoma cell line FTC-133, the stabilized and non-enzymatic IDO1 protein promotes the proliferation and migration of the tumor, resulting in an adverse pro-tumorigenic effect. These results uncover an unexpected adverse effect of IDO1 inhibitors in the tumor microenvironment that overcomes the enzymatic inhibition of IDO1, and suggest protein degradation, rather than enzymatic inhibition, as a more effective approach to target IDO1 in the tumor microenvironment.

P2, N=43, Active, not recruiting, Memorial Sloan Kettering Cancer Center | Recruiting --> Active, not recruiting

These findings suggest a potential inhibitory mechanism for PF-06840003 and offer valuable structural insights for the rational design of potent IDO1 inhibitors. It should be noted that the inhibitory activity of the designed lead compounds is based solely on computational predictions; experimental validation through in vitro and in vivo studies is still required to confirm their actual inhibitory effects and pharmacokinetic properties.

P1/2, N=361, Recruiting, ModernaTX, Inc. | N=194 --> 361 | Trial completion date: Dec 2027 --> Feb 2032 | Trial primary completion date: Dec 2027 --> Feb 2032

A few IDO1 inhibitors have reached the clinical stage, including navoximod, epacadostat and linrodostat. Using second harmonic generation analysis (SHG) and molecular dynamics simulations, here we show that these clinical inhibitors can induce distinct allosteric motions in the enzyme that affect the stability of the transient signaling complex between IDO1 and Src tyrosine kinase. Next generation sequencing demonstrates that, despite sharing a similar ability to inhibit the enzyme's catalytic function, all three catalytic inhibitors modulate the IDO1's signaling function in different ways, regulating distinct transcriptomes in SKOV3 cells.

To address these challenges, we developed a novel photosensitizer (PS), TTVBO-1MT, by conjugating the indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor 1-methyl-d-tryptophan (1-MT) to the aggregation-induced emission (AIE) PS TTVBO via a glutathione (GSH)-responsive linker...This combined effect promoted T-cell infiltration and triggered a systemic antitumor immune response. Overall, the results suggest that TTVBO-1MT enables autophagy-assisted immuno-photodynamic modulation of the tumor microenvironment (TME), offering significant therapeutic potential.

The wound healing and colony assays also prove that these complexes significantly inhibit the metastasis of 4T1 cells. Furthermore, while inducing apoptosis, these complexes can also promote the release of damage-related molecular patterns (calreticulin (CRT), high mobility group protein b1 (HMGB1) and adenosine triphosphate (ATP)), thereby inducing immunogenic cell death (ICD).

Prior to these findings, clinical management centered around surgical excision. The use of molecular compounds such as indoximob, epacadostat, BMS-986205 and navoximod, that directly target IDO1 opens new possibilities for targeting these tumors, improving clinical outcomes, and minimizing the morbidities often associated with surgery.

However, PAF levels remained elevated despite treatment, indicating limited efficacy in PAF-associated pathways. Indoximod exhibited anti-inflammatory effects in this acute colitis model, likely by downregulating key proinflammatory mediators.

In this study, a multi-bioactive nanocomposite consisting of hyaluronic acid-block-poly(1-methyl-d-tryptophan-co-l-glutamic acid) (HA-PMTG) and tetracarboxyl porphyrin-trivalent Fe(III) metal-organic framework (MOFTCPP-Fe) was developed for enhanced cascading PDIT...Furthermore, treatment with HA-PMTG@MOFTCPP-Fe on the primary tumor inhibited distant tumor growth through a bystander effect and prevented tumor recurrence by activating immune memory. Thus, the multi-bioactive HA-PMTG@MOFTCPP-Fe offers an effective cascading strategy to enhance the PDIT of cancer.

Also, by the elevated secretion of IL-12 cytokine, T cells release high levels of IFNγ, which is a central role in IL-12-mediated immunotherapy. This co-delivery system presents a promising strategy to overcome the limitations of single IL-12-mediated therapy by simultaneously promoting antitumor immune responses and inhibiting immunosuppressive mechanisms, thereby enhancing the overall efficacy of cancer immunotherapy.