Novel screening assay for Arginase-1 inhibitors published in SLAS Discovery

Oss – May, 18th, 2020 – Arginase-1 is a promising new drug target for cancer immunotherapy. A novel assay technology for high-throughput screening (HTS) of Arginase-1 has been published in SLAS Discovery [1] by researchers from NTRC in collaboration with Pivot Park Screening Centre (PPSC). The assay technology is known as Arginase Gold™.

The enzyme Arginase-1 has a regulatory role in T cell and natural killer cell-mediated immunity in the tumor microenvironment by decreasing levels of the amino acid L-arginine, which is critical for an effective anti-tumor immune response. Preclinical studies have shown that inhibition of Arginase-1 increases tumor immune cell infiltration and decreases tumor growth in model systems for cancer [2-4]. The first small molecule Arginase-1 inhibitor CB-1158 (INCB001158) is currently being investigated in clinical trials for the treatment of advanced and metastatic tumors as a single agent, and in combination with chemotherapy, immune checkpoint therapy and the IDO1 inhibitor epacadostat [5].

Arginase Gold™ is a homogenous (mix-and-measure) enzyme activity assay for Arginase-1, making use of a fluorescent probe developed at NTRC. The assay measures the conversion of L-arginine into its substrate L-ornithine by a decrease in fluorescent signal, thus generating a gain of signal in the presence of inhibitors. In the article, which appeared online today in SLAS Discovery [1], the Arginase Gold™ assay was validated by side-by-side profiling of reference inhibitors in a traditional colorimetric, multi-step urea assay and in the Arginase Gold™ assay. The application in automated HTS was demonstrated by screening a library of small synthetic chemicals at PPSC and deconvolution of active hit compounds. Besides its robustness, easiness to use, and scalability, an appealing characteristic of the Arginase Gold™ assay is that it can be used in a kinetic mode, thus enabling the study of slow-on/slow-off inhibitors, that is, compounds with a long target residence time [6].


The figure shows dose-response curves of three reference inhibitors in the Arginase Gold™ assay (left) and inhibitory constant (Ki) measured as function of reaction time (right). Adapted from Grobben et al. [1].


[1] Grobben et al. (2020) High-throughput fluorescence-based activity assay for Arginase-1. SLAS Discovery, published online first, 15 May 2020.

[2] Steggerda et al. (2017) Inhibition of arginase by CB-1158 blocks myeloid cell-mediated immune suppression in the tumor microenvironment. Journal for Immunotherapy of Cancer 5, 101.

[3] Czystowska-Kuzmicz et al. (2019) Small extracellular vesicles containing arginase-1 suppress T-cell

responses and promote tumor growth in ovarian carcinoma. Nature Communications 10, 3000.

[4] Miret et al. (2019) Suppression of myeloid cell arginase activity leads to therapeutic response in a NSCLC mouse model by activating anti-tumor immunity. Journal for Immunotherapy of Cancer 7, 32.

[5] see for NCT02903914, NCT03314935 and NCT03361228

[6] Grobben et al. (2020) Structural insights into human Arginase-1 pH dependence and its inhibition by the small molecule inhibitor CB-1158. Journal of Structural Biology X 4, 100014.

NTRC is a precision medicine company dedicated to discovering new anti-cancer drug candidates. It is our mission to help you finding a mechanistic hypothesis before entering the clinic. We provide cell-based profiling services, target residence time measurements and biochemical profiling. We can study a wide range of cancer cells, primary patient material and immune cells in vitro, in isolation and in co-culture, after exposure to monotherapy and combination therapy. Keywords are: Quality. Flexibility. Short Turnaround Time.

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