ESI-09

ESI-09 is a specific inhibitor of EPAC with IC50 values of 1.4 and 3.2 µM for EPAC2 and EPAC1, respectively [1].

cAMP/cAMP regulated guanine nucleotide exchange factor (EPAC/cAMP-GEF) is a guanine nucleotide exchange factor for small GTPases Rap1 and Rap2 in response to intracellular cAMP [2].

ESI-09 is a specific EPAC inhibitor. ESI-09 (25 µM) reduced EPAC1 and EPAC2 GEF activity to basal levels in the presence of 25 µM cAMP. In the presence of 25 µM cAMP, ESI-09 inhibited cAMP-mediated EPAC2 and EPAC1 GEF activity with IC50 values of 1.4 and 3.2 µM respectively and exhibited 100 times selectivity than PKA. In the pancreatic cancer cell line AsPC-1, ESI-09 inhibited Akt phosphorylation at T308 and S473 stimulated by 007-AM in a dose dependent way. In pancreatic endocrine β cells, ESI-09 inhibited the increase of insulin secretion stimulated by 007-AM in a dose dependent way. In pancreatic cancer cell lines AsPC-1 and PANC-1, ESI-09 significantly reduced cell migration through the inhibition of EPAC1 [1]. In the presence of 20 µM cAMP, ESI-09 inhibited cAMP-mediated EPAC2 and EPAC1 GEF activity with IC50 values of 4.4 and 10.8 µM, respectively [2].

References:
[1].  Almahariq M, Tsalkova T, Mei FC, et al. A novel EPAC-specific inhibitor suppresses pancreatic cancer cell migration and invasion. Mol Pharmacol, 2013, 83(1): 122-128.
[2].  Zhu Y, Chen H, Boulton S, et al. Biochemical and pharmacological characterizations of ESI-09 based EPAC inhibitors: defining the ESI-09 ""therapeutic window"". Sci Rep, 2015, 5: 9344.

Biochemical and pharmacological characterizations of ESI-09 based EPAC inhibitors: defining the ESI-09 "therapeutic window".[Pubmed:25791905]

Sci Rep. 2015 Mar 20;5:9344.

The cAMP signaling cascade is one of the most frequently targeted pathways for the development of pharmaceutics. A plethora of recent genetic and pharmacological studies suggest that exchange proteins directly activated by cAMP (EPACs) are implicated in multiple pathologies. Selective EPAC inhibitors have been recently developed. One specific inhibitor, ESI-09, has been shown to block EPAC activity and functions, as well as to recapitulate genetic phenotypes of EPAC knockout mice when applied in vivo. However, a recent study raised concern that ESI-09 might act as a non-specific protein denaturant. Herein, we present a detailed biochemical and pharmacological characterization, as well as a structure-activity relationship (SAR) analysis of ESI-09. Our studies show that ESI-09 dose-dependently inhibits activity of both EPAC1 and EPAC2 with apparent IC50 values well below the concentrations shown to induce "protein denaturation". Moreover, the ESI-09's action towards EPAC proteins is highly sensitive to minor modifications of the 3-chlorophenyl moiety. Taken together, these results demonstrate that ESI-09 indeed acts as an EPAC specific antagonist and does not significantly destabilize/denature proteins at pharmacological effective concentrations. This conclusion is further supported by NMR data showing that ESI-09 induces residue-dependent chemical shift changes at low concentrations, while preserving well dispersed peaks.

Efficient Synthesis of ESI-09, A Novel Non-cyclic Nucleotide EPAC Antagonist.[Pubmed:23459418]

Tetrahedron Lett. 2013 Mar 20;54(12):1546-1549.

A concise and efficient synthetic approach to producing a novel non-cyclic nucleotide EPAC antagonist ESI-09 and its new analogs is reported. Key features of the synthesis include a mild and reliable one-pot procedure for an isoxazole synthon, as well as a modified one-pot protocol for the cyanomethyl ketone key intermediate. The synthesis requires inexpensive starting materials and only three linear steps for the completion in a total yield of 53%.

A novel EPAC-specific inhibitor suppresses pancreatic cancer cell migration and invasion.[Pubmed:23066090]

Mol Pharmacol. 2013 Jan;83(1):122-8.

Exchange protein directly activated by cAMP (EPAC) and cAMP-dependent protein kinase (PKA) are two intracellular receptors that mediate the effects of the prototypic second messenger cAMP. Identifying pharmacological probes for selectively modulating EPAC activity represents a significant unmet need within the research field. Herein, we report the identification and characterization of 3-(5-tert-butyl-isoxazol-3-yl)-2-[(3-chloro-phenyl)-hydrazono]-3-oxo-propionitril e (ESI-09), a novel noncyclic nucleotide EPAC antagonist that is capable of specifically blocking intracellular EPAC-mediated Rap1 activation and Akt phosphorylation, as well as EPAC-mediated insulin secretion in pancreatic beta cells. Using this novel EPAC-specific inhibitor, we have probed the functional roles of overexpression of EPAC1 in pancreatic cancer cells. Our studies show that EPAC1 plays an important role in pancreatic cancer cell migration and invasion, and thus represents a potential target for developing novel therapeutic strategies for pancreatic cancer.