Isolation, structural characterization and quality control strategy of an unknown process-related impurity in...

Sugammadex sodium is the first selective relaxant binding agent (SRBA) indicated for reversal of neuromuscular blockade induced by rocuronium or vecuronium during surgery. The chemical synthesis of sugammadex involved the nucleophilic substitution reaction between 6-per-deoxy-6-per-halo-γ-cyclodextrin and 3-mercaptopropionic acid under basic conditions. During the manufacture of sugammadex sodium, an unknown process-related impurity was observed in pilot batches in the range of 0.21-1.9 % based upon HPLC analysis. The same impurity was also detected in commercial Bridion® samples at the levels of more than 0.1 %. Thus this unknown impurity was enriched from the mother liquor of reaction by preparative HPLC and characterized by LC-MS/QTOF, 1D-NMR (¹H, ¹³C, DEPTQ) and 2D-NMR (¹H-¹H COSY, TOCSY, HSQC, HMBC, NOESY) techniques. Based on spectroscopic analysis and the synthetic route of sugammadex sodium, this new impurity was identified as monocyanoethyl sugammadex (impurity-I). The prospects to the formation mechanism and control strategy of impurity-I were discussed in detail. Moreover, the toxicological properties of impurity-I were evaluated using ADMET Predictor® software.