Structural study of bioisosteric derivatives of 5-(1H-indol-3-yl)-benzotriazole and their ability to form chalcogen bonds.

Recently, inter-est in the isosteric replacement of a nitro-gen atom to selenium, sulfur or oxygen atoms has been highlighted in the design of potential inhibitors for cancer research. In this context, the structures of 5-(1H-indol-3-yl)-2,1,3-benzotriazole derivatives [5-(1H-indol-3-yl)-2,1,3-benzo-thia-diazole (bS, C14H9N3S) and 5-(1H-indol-3-yl)-2,1,3-benzoxa-diazole (bO, C14H9N3O)], as well as a synthesis inter-mediate of the selenated bioisostere [5-[1-(benzensulfon-yl)-1H-indol-3-yl]-2,1,3-benzoselena-diazole (p-bSe, C20H13N3O2SSe)] were determined using single-crystal X-ray diffraction (SCXRD) analyses. Despite being analogues, different crystal packing, torsion angles and supra-molecular features were observed, depending on the substitution of the central atoms of the benzotriazole. In particular, chalcogen inter-actions were described in the case of p-bSe and not in the bS and bO derivatives. An investigation by ab initio computational methods was therefore conducted to understand the effect of the substitution on the ability to form chalcogen bonds and the flexibility of the compounds.

Investigation of chalcogen bioisosteric replacement in a series of heterocyclic inhibitors of tryptophan 2,3-dioxygenase.

Selenium is an underexplored element that can be used for bioisosteric replacement of lower molecular weight chalcogens such as oxygen and sulfur. More studies regarding the impact of selenium substitution in different chemical scaffolds are needed to fully grasp this element's potential. Herein, we decided to evaluate the impact of selenium incorporation in a series of tryptophan 2,3-dioxygenase (TDO2) inhibitors, a target of interest in cancer immunotherapy. First, we synthesized the different chalcogen isosteres through Suzuki-Miyaura type coupling. Next, we evaluated the isosteres' affinity and selectivity for TDO2, as well as their lipophilicity, microsomal stability and cellular toxicity on TDO2-expressing cell lines. Overall, chalcogen isosteric replacements did not disturb the on-target activity but allowed for a modulation of the compounds' lipophilicity, toxicity and stability profiles. The present work contributes to our understanding of oxygen/sulfur/selenium isostery towards increasing structural options in medicinal chemistry for the development of novel and distinctive drug candidates.

Rational Design of Original Fused-Cycle Selective Inhibitors of Tryptophan 2,3-Dioxygenase.

Tryptophan 2,3-dioxygenase (TDO2) is a heme-containing enzyme constitutively expressed at high concentrations in the liver and responsible for l-tryptophan (l-Trp) homeostasis. Expression of TDO2 in cancer cells results in the inhibition of immune-mediated tumor rejection due to an enhancement of l-Trp catabolism via the kynurenine pathway. In the study herein, we disclose a new 6-(1H-indol-3-yl)-benzotriazole scaffold of TDO2 inhibitors developed through rational design, starting from existing inhibitors. Rigidification of the initial scaffold led to the synthesis of stable compounds displaying a nanomolar cellular potency and a better understanding of the structural modulations that can be accommodated inside the active site of hTDO2.

Interrogating the Lactate Dehydrogenase Tetramerization Site Using (Stapled) Peptides.

Lactate dehydrogenases (LDHs) are tetrameric enzymes of major significance in cancer metabolism as well as promising targets for cancer therapy. However, their wide and polar catalytic sites make them a challenging target for orthosteric inhibition. In this work, we conceived to target LDH tetramerization sites with the ambition of disrupting their oligomeric state. To do so, we designed a protein model of a dimeric LDH-H. We exploited this model through WaterLOGSY nuclear magnetic resonance and microscale thermophoresis for the identification and characterization of a set of α-helical peptides and stapled derivatives that specifically targeted the LDH tetramerization sites. This strategy resulted in the design of a macrocyclic peptide that competes with the LDH tetramerization domain, thus disrupting and destabilizing LDH tetramers. These peptides and macrocycles, along with the dimeric model of LDH-H, constitute promising pharmacological tools for the de novo design and identification of LDH tetramerization disruptors. Overall, our study demonstrates that disrupting LDH oligomerization state by targeting their tetramerization sites is achievable and paves the way toward LDH inhibition through this novel molecular mechanism.

Current state on tryptophan 2,3-dioxygenase inhibitors: a patent review.

INTRODUCTION: Tryptophan-2, 3-dioxygenase (TDO2) is a tryptophan-degrading enzyme constitutively expressed in the liver and to a lesser extend in the brain. Before its link to cancer immunotherapy was discovered in 2011, the search for TDO2 inhibitors was initially driven by depression therapy. In the recent years, TDO2 has drawn an increasing attention as a promising target in both cancer and neuropsychiatric diseases. AREAS COVERED: Patent literature regarding Tryptophan-2, 3-dioxygenase inhibitors is reviewed. Compounds are categorized by chemical structure. Representative examples of each category are presented with their inhibitory activity and, when available, structure-activity relationships. Data from patent literature is deepened with relevant peer-reviewed literature. EXPERT OPINION: Very few selective and potent inhibitors were to this day reported and there are currently no TDO2 inhibitors in clinical trials. Despite the challenges in their discovery, the search for TDO2 inhibitors is a very active area of research, as such molecules may prove to be of great interest in not only cancer immunotherapy drug arsenal, but also in neurodegenerative diseases.