Dual TDO/IDO Inhibitor

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.

Furthermore, the binding and dissociation processes of the C1 inhibitor (NLG919) were simulated by the adaptive steering molecular dynamics (ASMD) method, which not only addressed the possible stable, metastable, and transition states for C1 inhibitor-IDO/TDO interactions, but also accurately predicted kinetic data for C1 inhibitor binding and dissociation. In conclusion, we have constructed a complete process from enzyme (IDO/TDO) conformational activation to inhibitor binding/dissociation and used the thermodynamic and kinetic data of each link as clues to verify the control mechanism of IDO/TDO on inhibitor selectivity. This is of great significance for us to understand the design principles of tumor immunotherapy drugs and to avoid drug resistance of immunotherapy drugs.

However, studies using IDO/TDO inhibitors against cancer have not yet shown that this type of treatment can be successful...This strategy may be beneficial in the treatment of aggressive breast cancer, particularly in patients with triple-negative breast cancer. A major challenge to this strategy, when searching for an effective treatment for tumors, especially tumors like breast carcinoma that often metastasize to the brain, is finding KMO inhibitors that adequately cross the blood-brain barrier.

Next, we used a syngeneic mouse model of LLC (Lewis lung cancer) vs cisplatin resistant LLC-CR, to examine the effects of AT-0174 (170 mg/kg; P.O. once daily) in combination with anti-PD1 antibody (10 mg/ml; I.P. once every 3 days)...Treatment with AT-0174 resulted in higher tumor infiltrating lymphocytes of Teffs and NK and lower Treg frequency in LLC-CR tumors than treatment with a selective IDO1 inhibitor (epacadostat)...Support by the Dept. of Veterans Affairs.

To investigate the generalizability of our results, we also performed metabolomics and serum specimens from a large randomized Phase 3 trial (CheckMate 025) with 743 RCC patients, among which 394 received nivolumab and 349 received everolimus. We identified increased tryptophan to kynurenine conversion in response to PD1 blockade in a subset of melanoma and RCC patients. By using independent cohorts, we showed that Kyn/Trp temporal alterations robustly correlated with overall survival of patients receiving nivolumab. Our findings illustrate that checkpoint blockade in combination with IDO/TDO inhibitors might only benefit a selected group of patients with checkpoint-inhibition-triggered kynurenine pathway activation.

To investigate the generalizability of our results, we also performed metabolomics and serum specimens from a large randomized Phase 3 trial (CheckMate 025) with 743 RCC patients, among which 394 received nivolumab and 349 received everolimus. We identified increased tryptophan to kynurenine conversion in response to PD1 blockade in a subset of melanoma and RCC patients. By using independent cohorts, we showed that Kyn/Trp temporal alterations robustly correlated with overall survival of patients receiving nivolumab. Our findings illustrate that checkpoint blockade in combination with IDO/TDO inhibitors might only benefit a selected group of patients with checkpoint-inhibition-triggered kynurenine pathway activation.