Cell experiment:

NFAT-RE-luc2 Jurkat cells are collected, centrifuged at 300 g for 5 minutes and re-suspended in serum-free RPMI-1640 media, plus supplements without antibiotic. Cell suspension (15,000 cells/20 μL) is added to each well of a solid black 384 well plate and incubated in the presence of compound for 20 hours at 37 ℃. Alamar Blue is used and is added to each well at 2x concentration in media and reaction allowed to proceed for 4 hours at 37 ℃. Fluorescence (ex. 540 nm/em. 590 nm) is recorded using Pherastar FS[1].

ER-000444793 is a potent inhibitor of mitochondrial permeability transition pore (mPTP) opening. ER-000444793 inhibits mPTP with an IC50 of 2.8 μM.

ER-000444793 is a small molecule, non-toxic mPTP inhibitor with a mechanism of action independent of CypD inhibition. ER-000444793 potently and dose-dependently inhibits Ca2+-induced mPT. ER-000444793 binds CypD, a CsA/CypD homogenous time-resolved fluorescence (HTRF) assay is used to study compound binding. Both CsA and SfA dose-dependently decrease HTRF signal, suggesting displacement of labelled CsA from rhCypD protein (CsA IC50=23 nM and SfA IC50= 5 nM). In contrast, ER-000444793 has no effect up to a concentration of 50 μM, indicating lack of displacement of labelled-CsA from rhCypD protein. Together, these data suggest the mechanism of ER-000444793 in delaying mPT is independent of CypD functional inhibition[1].

[1]. Briston T, et al. Identification of ER-000444793, a Cyclophilin D-independent inhibitor of mitochondrial permeability transition, using a high-throughput screen in cryopreserved mitochondria. Sci Rep. 2016 Nov 25;6:37798.