Analysis of BNP7787 thiol-disulfide exchange reactions in phosphate buffer and human plasma using microscale electrochemical high performance liquid chromatography.

BNP7787 (disodium 2,2'-dithio-bis ethane sulfonate; Tavocept) is a novel water-soluble investigational agent that is undergoing clinical development for prevention and mitigation of cisplatin-induced nephrotoxicity. BNP7787 is a disulfide that undergoes thiol-disulfide exchange reactions in vivo with physiological thiols. Mesna-disulfide heteroconjugates that form as a result of these exchange reactions may play a key role in the protection against cisplatin-induced nephrotoxicity. Although several analytical methods have been used to detect thiols and disulfides, they have notable limitations including (i) low sensitivity, (ii) interference by chemical modification by derivatization reagents, and (iii) cumbersome sample preparation. In this paper, a sensitive micro-HPLC-EC method is described that identifies BNP7787 and mesna in plasma and phosphate buffer across a broad concentration range from 500nM to 100microM. This method utilizes a dual electrochemical detector equipped with a wall-jet gold electrode. The approach described here facilitates the identification of BNP7787 and mesna down to nanomolar levels. Although we did not focus on optimizing the approach for other thiol and disulfide compounds, we believe this approach could be optimized and used in the identification of other thiols and disulfides in plasma. The assay requires significantly less sample preparation and does not involve the use of derivatizing agents (i.e., the thiol and disulfide species can be detected directly) and represents an important advance over previous methods. This method was used to detect and quantitate BNP7787 and to monitor and kinetically characterize the interactions of BNP7787 with glutathione, cysteine, cysteinyl-glycine, cysteinyl-glutamate and homocysteine.