Pharmacokinetics and pharmacodynamics of orally administered acetylenic tricyclic bis (cyanoenone), a highly potent Nrf2 activator with a reversible covalent mode of action

Abstract

The acetylenic tricyclic bis(cyanoenone) TBE-31 is a highly potent cysteine targeting compound with a reversible covalent mode of action; its best-characterized target being Kelch-like ECH-associated protein-1 (Keap1), the cellular sensor for oxidants and electrophiles. TBE-31 reacts with cysteines of Keap1, impairing its ability to target nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) for degradation. Consequently, Nrf2 accumulates and orchestrates cytoprotective gene expression. In this study we investigated the pharmacokinetic and pharmacodynamic properties of TBE-31 in C57BL/6 mice. After a single oral dose of 10 μmol/kg (∼200 nmol/animal), the concentration of TBE-31 in blood exhibited two peaks, at 22.3 nM and at 15.5 nM, 40 min and 4 h after dosing, respectively, as determined by a quantitative stable isotope dilution LC-MS/MS method. The AUC0–24h was 195.5 h/nmol/l, the terminal elimination half-life was 10.2 h, and the kel was 0.068 h−1. To assess the pharmacodynamics of Nrf2 activation by TBE-31, we determined the enzyme activity of its prototypic target, NAD(P)H:quinone oxidoreductase 1 (NQO1) and found it elevated by 2.4- and 1.5-fold in liver and heart, respectively. Continuous feeding for 18 days with diet delivering the same daily doses of TBE-31 under conditions of concurrent treatment with the immunosuppressive agent azathioprine had a similar effect on Nrf2 activation without any indications of toxicity. Together with previous reports showing the cytoprotective effects of TBE-31 in animal models of carcinogenesis, our results demonstrate the high potency, efficacy and suitability for chronic administration of cysteine targeting reversible covalent drugs.

Downregulation of Keap1 Confers Features of a Fasted Metabolic State

“…Ces1g-KO mice are protected against development of atherosclerosis ( Xu et al., 2017 ), as are Nrf2-KO mice ( Polonen et al., 2019 ; Sussan et al., 2008 ). In addition, knockout of Ces1g decreases levels of cholesterol in plasma ( Xu et al., 2017 ), as does Nrf2 deficiency ( Meakin et al., 2014 ; Polonen et al., 2019 ), whereas plasma low-density lipoprotein levels are increased following chronic pharmacologic activation of Nrf2 by TBE-31 ( Kostov et al., 2015 ). Taken together, these findings suggest that one mechanism by which Nrf2 activation affects lipid metabolism involves Ces1.…”

Therapeutic targeting of the NRF2 and KEAP1 partnership in chronic diseases

“…Thus, the NRF2 activator TBE-31, a tricyclic cyanoenone closely related to the triterpenoids described above, has a half-life of 10 h in murine skin and plasma 51,270 ,…”

C151 in KEAP1 is the main cysteine sensor for the cyanoenone class of NRF2 activators, irrespective of molecular size or shape

“…TBE-31 binds to KEAP1 covalently and reversibly 23 , and is suitable for chronic in vivo administration 31 . TBE-31, MCE-23 and MCE-1 are all highly reactive with sulfhydryl groups as they contain activated Michael acceptors within their structures.…”