Development of a chromatographic method for the analysis of risdiplam in serum extracts

Risdiplam has been used to treat spinal muscular atrophy for 3 years. There are limited number of papers devoted to its analytics. Until now, risdiplam and its metabolites have only been analyzed using a C18 column, while the sample preparation method involved protein precipitation. Risdiplam was analyzed using reversed-phase UHPLC. The experiment was designed to compare the retention of risdiplam on five columns using various mobile phases. The protein precipitation was used as the sample preparation method. Risdiplam shows greater retention on phenyl columns, where π-π interactions take part in retention. The increase of mobile phase pH caused increased risdiplam retention, while salt concentration had no significant effect. An octadecyl column with pentafluorophenyl groups was selected with a mobile phase containing 10 mM ammonium formate (pH 4) and acetonitrile. The method was characterized by good linearity, repeatability, and short analysis time. It was applied to risdiplam analysis in serum samples after protein precipitation with different solvents. Finally, proteins were effectively precipitated using 10% TFA solution, providing 90% recovery. The developed procedure of extraction and determination of risdiplam is simple, fast and reliable. It may find application for routine monitoring of risdiplam or for quality control.