RESUMO
BACKGROUND: Arginases play essential roles in metabolic pathways, determining the fitness of both immune and tumour cells. Along with the previously validated role of ARG1 in cancer, the particular significance of ARG2 as a therapeutic target has emerged as its levels correlate with malignant phenotype and poor prognosis. These observations unveil arginases, and specifically ARG2, as well-validated and promising therapeutic targets. OATD-02, a new boronic acid derivative, is the only dual inhibitor, which can address the benefits of pharmacological inhibition of arginase 1 and 2 in cancer. METHODS: The inhibitory activity of OATD-02 was determined using recombinant ARG1 and ARG2, as well as in a cellular system using primary hepatocytes and macrophages. In vivo antitumor activity was determined in syngeneic models of colorectal and kidney carcinomas (CT26 and Renca, respectively), as well as in an ARG2-dependent xenograft model of leukaemia (K562). RESULTS: OATD-02 was shown to be a potent dual (ARG1/ARG2) arginase inhibitor with a cellular activity necessary for targeting ARG2. Compared to a reference inhibitor with predominant extracellular activity towards ARG1, we have shown improved and statistically significant antitumor efficacy in the CT26 model and an immunomodulatory effect reflected by Treg inhibition in the Renca model. Importantly, OATD-02 had a superior activity when combined with other immunotherapeutics. Finally, OATD-02 effectively inhibited the proliferation of human K562 leukemic cells both in vitro and in vivo. CONCLUSIONS: OATD-02 is a potent small-molecule arginase inhibitor with optimal drug-like properties, including PK/PD profile. Excellent activity against intracellular ARG2 significantly distinguishes OATD-02 from other arginase inhibitors. OATD-02 represents a very promising drug candidate for the combined treatment of tumours, and is the only pharmacological tool that can effectively address the benefits of ARG1/ARG2 inhibition. OATD-02 will enter clinical trials in cancer patients in 2022.
RESUMO
BACKGROUND: Searching for new effective drugs against human and animal toxoplasmosis we decided to test the anti-Toxoplasma potential of phytoecdysteroids (α-ecdysone and 20-hydroxyecdysone) characterized by the pleiotropic activity on mammalian organisms including the enhancement of host's anti-parasitic defence. This objective was accomplished by the in vitro evaluation of T. gondii growth in phytoecdysteroid-treated immunocompetent cells of selected hosts: humans and two strains of inbred mice with genetically determined different susceptibility to toxoplasmosis. METHODS: Peripheral mononuclear blood cells were isolated from Toxoplasma-positive and Toxoplasma-negative women (N = 43) and men (N = 21). Non-infected mice (C57BL/6, N = 10 and BALB/c, N = 14) and mice (BALB/c, N = 10) challenged intraperitoneally with 5 tissue cysts of the T. gondii DX strain were also used in this study as a source of splenocytes. The effects of phytoecdysteroids on the viability of human PBMC and mouse splenocytes were evaluated using the MTT assay. The influence of phytoecdysteroids on PBMCs, splenocytes and T. gondii proliferation was measured using radioactivity tests (the level of 3[H] uracil incorporation by toxoplasms or 3[H] thymidine by PBMCs and splenocytes), which was confirmed by quantitative Real-Time PCR. Statistical analysis was performed using SigmaStat 3.5 (Systat Software GmbH). The best-fit IC50 curves were plotted using GraphPad Prism 6.0 (GraphPad Software, Inc.). RESULTS: Our results showed that phytoecdysteroids promote the multiplication of Toxoplasma in cultures of human or murine immune cells, in contrast to another apicomplexan parasite, Babesia gibsoni. Additionally, the tested phytoecdysteroids did not stimulate the in vitro secretion of the essential protective cytokines (IFN-γ, IL-2 and IL-10), neither by human nor by murine immune cells involved in an effective intracellular killing of the parasite. CONCLUSIONS: Judging by the effect of phytoecdysteroids on the T. gondii proliferation, demonstrated for the first time in this study, it seems that these compounds should not be taken into consideration as potential medications to treat toxoplasmosis. Phytoecdysteroids included in the food are most likely not harmful for human or animal health but certain nutrients containing ecdysteroids at high concentrations could promote T. gondii proliferation in chronically infected and immunocompromised individuals. In order to assess the real impact of ecdysteroids on the course of natural T. gondii invasion, in vivo research should be undertaken because it cannot be ruled out that the in vivo effect will be different than the in vitro one. However, taking into account the possible stimulating effect of ecdysteroids on some opportunistic parasites (such as Toxoplasma or Strongyloides) further studies are necessary and should focus on the mechanisms of their action, which directly or indirectly enhance the parasite growth. Since ecdysteroids are considered as potential drugs, it is essential to determine their effect on various parasitic pathogens, which may infect the host at the same time, especially in immunocompromised individuals.
