Advancing stereoisomeric separation of an atropisomeric Bruton's tyrosine kinase inhibitor by using sub-2 µm immobilized polysaccharide-based chiral columns in supercritical fluid chromatography.

BMS-986142 is a Bruton's tyrosine kinase inhibitor under development to treat several disease types. The compound contains three chiral elements: one chiral center and two chiral axes, resulting in three potential atropisomeric impurities in its drug substance and drug products. Separation of BMS-986142 atropisomers has been successfully achieved on an achiral polar-embedded C18 column in reversed-phase liquid chromatography (RPLC) and on polysaccharide-based chiral columns in RPLC and supercritical fluid chromatography (SFC). Compared to the RPLC chiral separation, the SFC atropisomeric separation on a sub-2 μm immobilized cellulose-based column is much more efficient and environmentally friendly. The analysis time in SFC was reduced by 8-fold compared to that in RPLC, and the method sensitivity in SFC on the sub-2 μm chiral column in 3.0 mm I.D. was 2 to 4-fold better than that on 3 μm chiral columns in 4.6 mm I.D.. Furthermore, our study suggests that the contribution to band broadening from the extra column volume (ECV) of modern commercial SFC instrument was not negligible for a 3.0 mm I.D. × 100 mm column packed with 1.6 μm particles. This result reaffirms that there is a great need for further improvement of SFC instrument design in order to realize the full theoretical efficiency of both sub-2 μm achiral and chiral columns.