A variety of substituted benzotriazoles have been prepared by the [3 + 2] cycloaddition of azides to benzynes. The reaction scope is quite general, affording a rapid and easy entry to substituted, functionalized benzotriazoles under mild conditions.

The relative reactivity of various functional groups towards alkyne electrophilic cyclization reactions has been studied. The required diarylalkynes have been prepared by consecutive Sonogashira reactions of appropriately substituted aryl halides and competitive cyclizations have been performed using I 2 , ICl, NBS and PhSeCl as electrophiles. The results indicate that the nucleophilicity of the competing functional groups, polarization of the alkyne triple bond, and the cationic nature of the intermediate are the most important factors in determining the outcome of these reactions.

A large number of functionally-substituted 2-alkyn-1-one O-methyl oximes have been cyclized under mild reaction conditions in the presence of ICl to give the corresponding 4-iodoisoxazoles in moderate to excellent yields. The resulting 4-iodoisoxazoles undergo various palladium-catalyzed reactions to yield 3,4,5-trisubstituted isoxazoles, including valdecoxib.

The IDO pathway mediates immunosuppressive effects through the metabolization of tryptophan (Trp) to kynurenine (Kyn), triggering downstream signaling through GCN2, mTOR and AHR that can affect differentiation and proliferation of T cells. Expression of the IDO1 gene by tumor cells or host APCs can inhibit tumor-specific effector CD8+ T cells and enhance the suppressor activity of Tregs, and high expression of IDO correlates with worse clinical prognosis in patients with a variety of malignancies. Therefore, targeting the IDO pathway via inhibition of the IDO enzyme or blocking its downstream signaling effects is a prime target for small-molecule immunomodulatory drugs in cancer. Here we describe the pharmacological and biological properties of NLG919, a novel small-molecule IDO-pathway inhibitor. NLG919 potently inhibits this pathway in vitro and in cell based assays (Ki=7 nM; EC50 =75 nM). It is orally bioavailable (F>70%); and has a favorable pharmacokinetic and toxicity profile. In mice, a single oral administration of NLG919 reduces the concentration of plasma and tissue Kyn by ∼ 50%. Using IDO-expressing human monocyte-derived DCs in allogeneic MLR reactions, NLG919 potently blocked IDO-induced T cell suppression and restored robust T cell responses with an ED50=80 nM. Similarly, using IDO-expressing mouse DCs from tumor-draining lymph nodes, NLG919 abrogated IDO-induced suppression of antigen-specific T cells (OT-I) in vitro, with ED50=120 nM. In vivo, in mice bearing large established B16F10 tumors, administration of NLG919 markedly enhanced the anti-tumor responses of naïve, resting pmel-1 cells to vaccination with cognate hgp100 peptide plus CpG-1826 in IFA. In this stringent established-tumor model, NLG919 plus pmel 1/vaccine produced a dramatic collapse of tumor size within 4 days of vaccination (∼95% reduction in tumor volume compared to control animals receiving pmel-1/vaccine alone without NLG919). In conclusion, NLG919 is a potent IDO pathway inhibitor with desirable pharmacological properties, suitable for the treatment of immunosuppression associated with cancer. Citation Format: Mario R. Mautino, Firoz A. Jaipuri, Jesse Waldo, Sanjeev Kumar, James Adams, Clarissa Van Allen, Agnieszka Marcinowicz-Flick, David Munn, Nicholas Vahanian, Charles J. Link. NLG919, a novel indoleamine-2,3-dioxygenase (IDO)-pathway inhibitor drug candidate for cancer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 491. doi:10.1158/1538-7445.AM2013-491

A novel class of 5-substituted 5H-imidazo[5,1-a]isoindoles are described as potent inhibitors of indoleamine 2,3dioxygenase 1 (IDO1). A structure-based drug design approach was used to elaborate the 5H-imidazo[5,1-a]isoindole core and to improve potency and pharmacological properties. Suitably placed hydrophobic and polar functional groups in the lead molecule allowed improvement of IDO1 inhibitory activity while minimizing off-target liabilities. Structure−activity relationship studies focused on optimizing IDO1 inhibition potency and a pharmacokinetic profile amenable to oral dosing while controlling CYP450 and hERG inhibitory properties.