Cell based functional assays for IDO1 inhibitor screening and characterization

• Published in: Oncotarget Vol. 9; no. 56; pp. 30814 - 30820
• Main Authors: Richards, Thomas, Brin, Elena
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 20.07.2018
• Subjects: Research Paper; epacadostat; BMS-986205; cell-based assay; IDO1
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.25720

Indoleamine 2,3-dioxygenase 1 (IDO1) is a new immune-oncology target and its inhibitors have shown promise in the clinic especially in combination with other immune-stimulating agents. Here we describe two robust cell-based assays for screening IDO1 inhibitors. Both assays can be easily adopted by most laboratories and utilized for screening of IDO1 inhibitors. Endogenous IDO1 expression is induced in a cancer cell line with interferon gamma and its activity is assessed by measuring kynurenine secreted into the media. The effect of cancer cell IDO1 induction and inhibition on T cell activation is evaluated in a co-culture assay using Jurkat T cell line. Additional readouts assessing cell viability are employed for early detection of false positive IDO1 inhibitors and toxic compounds. Clinical candidates epacadostat and BMS-986205 were evaluated in the assays as control compounds, the former can completely inhibit IDO1 activity while the maximum effect of the later is limited (to about 80% in our system) consistent with the differences in their interaction with IDO1. Nanomolar concentrations of both compounds rescued IDO1 mediated inhibition of T cell activation. However, treatment with micromolar concentrations of BMS-986205 blocked Jurkat T cell activation and after prolonged incubation induced cell death.