Determination of the Enantiomeric Purity of a CNS Agent, Sumanirole, by Electrokinetic Chromatography

Abstract

A chiral procedure based on electrokinetic chromatography was developed and validated for sumanirole (PNU‐95666E), a drug candidate that was under development for treatment of Parkinson's disease. The method underwent various iterations over a several years’ period, first utilizing a neutral cyclodextrin as the chiral recognition agent, then later using a highly sulfated‐beta‐cyclodextrin (HS‐β‐CD). Separation is on a 61 cm×50 µm ID fused silica capillary at an applied potential of −25 kV with a background electrolyte of 5% HS‐β‐CD in pH 2.50, 22.5 mM lithium phosphate buffer. For a sample prepared at 5 mg/mL, the limit of detection (LOD) for the undesired enantiomer (distomer) is about 0.02%. In a similar method developed for a congener of sumanirole, the LOD is approximately 0.01%, but at a sample concentration of 10 mg/mL. The separation, in both cases, takes less than 20 min. Over the range of 0.05–0.4%, the average recovery for the distomer of sumanirole was 102.1% and the linear regression correlation coefficient (r²) 0.9999. For the congener over the range of 0.1–1.8%, a correlation coefficient of 0.9999 and an average recovery of 105.2% were obtained. The sumanirole method in its several iterations was used to collect four years of ICH stability data on the active pharmaceutical ingredient (API). No sample, either in the ICH study or any other lot manufactured over the years, yielded a value above 0.05% for the distomer. The method was additionally used to assess chiral inversion in API and in several formulations.

Keywords:

• Chiral analysis
• Chiral capillary electrophoresis
• Enantioseparation by capillary electrophoresis
• CD‐mediated electrokinetic chromatography
• Highly‐sulfated cyclodextrins
• Enantiomeric excess of active pharmaceutical ingredient

Acknowledgments

J.M. Vasas is recognized for having contributed lab work to this project. Also, we acknowledge T.R. Alcumbrack, P.A. Hartman, A.K. Bose, and P.A. Irish for the HPLC Section. The enantiomers were synthesized by P. Gm. Wuts.