YH29407 with anti-PD-1 ameliorates anti-tumor effects via increased T cell functionality and antigen presenting machinery in the tumor microenvironment.

Among cancer cells, indoleamine 2, 3-dioxygenase1 (IDO1) activity has been implicated in improving the proliferation and growth of cancer cells and suppressing immune cell activity. IDO1 is also responsible for the catabolism of tryptophan to kynurenine. Depletion of tryptophan and an increase in kynurenine exert important immunosuppressive functions by activating regulatory T cells and suppressing CD8+ T and natural killer (NK) cells. In this study, we compared the anti-tumor effects of YH29407, the best-in-class IDO1 inhibitor with improved pharmacodynamics and pharmacokinetics, with first and second-generation IDO1 inhibitors (epacadostat and BMS-986205, respectively). YH29407 treatment alone and anti-PD-1 (aPD-1) combination treatment induced significant tumor suppression compared with competing drugs. In particular, combination treatment showed the best anti-tumor effects, with most tumors reduced and complete responses. Our observations suggest that improved anti-tumor effects were caused by an increase in T cell infiltration and activity after YH29407 treatment. Notably, an immune depletion assay confirmed that YH29407 is closely related to CD8+ T cells. RNA-seq results showed that treatment with YH29407 increased the expression of genes involved in T cell function and antigen presentation in tumors expressing ZAP70, LCK, NFATC2, B2M, and MYD88 genes. Our results suggest that an IDO1 inhibitor, YH29407, has enhanced PK/PD compared to previous IDO1 inhibitors by causing a change in the population of CD8+ T cells including infiltrating T cells into the tumor. Ultimately, YH29407 overcame the limitations of the competing drugs and displayed potential as an immunotherapy strategy in combination with aPD-1.

Chemical inhibition of prometastatic lysyl-tRNA synthetase-laminin receptor interaction.

Lysyl-tRNA synthetase (KRS), a protein synthesis enzyme in the cytosol, relocates to the plasma membrane after a laminin signal and stabilizes a 67-kDa laminin receptor (67LR) that is implicated in cancer metastasis; however, its potential as an antimetastatic therapeutic target has not been explored. We found that the small compound BC-K-YH16899, which binds KRS, impinged on the interaction of KRS with 67LR and suppressed metastasis in three different mouse models. The compound inhibited the KRS-67LR interaction in two ways. First, it directly blocked the association between KRS and 67LR. Second, it suppressed the dynamic movement of the N-terminal extension of KRS and reduced membrane localization of KRS. However, it did not affect the catalytic activity of KRS. Our results suggest that specific modulation of a cancer-related KRS-67LR interaction may offer a way to control metastasis while avoiding the toxicities associated with inhibition of the normal functions of KRS.

NKT ligand-loaded, antigen-expressing B cells function as long-lasting antigen presenting cells in vivo.

We had previously shown that activated NKT cells licensed B cells to be immunogenic antigen-presenting cells and helped to elicit a wide spectrum of cancer targeted immune responses. In the current study, we sought to verify the safety of αGalCer-loaded, and adenovirus-transduced B cell-based vaccines, together with mechanism of action. Intravenously injected αGalCer-loaded, antigen-expressing B cells rapidly localized in the spleen and directly primed CD8(+) T cells in an antigen-specific manner. The transferred antigen was sustained for at least 30 days. While some injected B cells produced nonspecific IgG, the antigen-specific IgG response was completely dependent on endogenous B cells. The liver was one of the main tissues where injected B cells were retained; however, we could not find the signs of liver toxicity. Our results demonstrate that αGalCer-loaded, antigen-expressing B cells behave as "antigen-presenting" cells that stimulate endogenous antigen-specific T cells and B cells in vivo without significant toxicity.