Identification and Biosynthesis of an N-Glucuronide Metabolite of Camonsertib

Camonsertib is a novel ATR kinase inhibitor in clinical development for advanced cancers targeting sensitizing mutations. This article describes the identification and biosynthesis of an N-glucuronide metabolite of camonsertib. This metabolite was first observed in human hepatocyte incubations and was subsequently isolated to determine the structure, evaluate its stability as part of bioanalytical method development and for use as a standard for estimating its concentration in Phase I samples. The N-glucuronide was scaled-up using a purified bacterial culture preparation and was subsequently isolated using preparative chromatography. The bacterial culture generated sufficient material of the glucuronide to allow for one- and two-dimensional ¹H and ¹³C NMR structural elucidation and further bioanalytical characterization. The NOE data combined with the gradient HMBC experiment and molecular modeling, strongly suggests that the point of attachment of the glucuronide results in the formation of (2S,3S,4S,5R,6R)-3,4,5-trihydroxy-6-(5-(4-((1R,3r,5S)-3-hydroxy-8-oxabicyclo[3.2.1]octan-3-yl)-6-((R)-3-methylmorpholino)-1H-pyrazolo[3,4-b]pyridin-1-yl)-1H-pyrazol-1-yl)tetrahydro-2H-pyran-2-carboxylic acid. Significance Statement This is the first report of a glucuronide metabolite of camonsertib formed by human hepatocyte incubations. This study reveals the structure of an N-glucuronide metabolite of camonsertib using detailed elucidation by one- and two-dimensional NMR after scale-up using a novel bacterial culture approach yielding significant quantities of a purified metabolite.