Early clinical drug product shelf-life setting using accelerated predictive stability and metabolite data for impurity qualification: A case study.

This case study demonstrates how knowledge of degradation products together with predictions can establish a lean stability strategy using the accelerated predictive stability (APS) principles. Applying all available data for AZD4831, (R)-1-(2-(1-aminoethyl)-4-chlorobenzyl)-2-thioxo-2,3-dihydro-1H-pyrrolo[3,2-d]pyrimidin-4(5H)-one, a reliable predictive model was developed despite minor differences in technical batch tablet compositions. Early forced degradation studies were performed to map potential degradation pathways. The insights from these studies guided the design of an APS study, which in turn inform on a suitable clinical stability program, initial specification and shelf-life. The use of APS predictions of degradants as well as total impurities highlighted at an early stage, when designing the clinical stability program, the opportunity to identify which degradation product that would be shelf-life limiting. Hence, it was possible to guide the development stability activities and set an initial shelf-life of a tablet formulation. The presented study displays the importance of combining several sources of information in drug development, e.g., potential degradation pathways, accelerated stability, stability program design, metabolite data, and specification limits.

Characterization and demonstration of drug compound ring-chain tautomer formation and its impacts on quality control.

Unknown chromatographic peaks, potential impurities, were observed in a series of related compounds. This led to the identification and characterization of tautomeric equilibria. Structural elucidation was required to understand the potential impurity profile, thus impacting method development for quality control. In this work, characterization of the chemical structures, AZ13581258 and AZD5718, and equilibria of the tautomeric forms was performed using a range of advanced analytical techniques such as preparative chromatography, nuclear magnetic resonance (NMR), chromatographic detection by mass spectrometry (MS), MSMS, and ultraviolet spectroscopy (UV). Predictions using density functional theory (DFT) further explains and confirms the tautomer equilibria through predictions of reaction barrier energies, UV-spectra and NMR data. These investigations led to fully understand the impurity profile and to the development of a quality control method for AZD5718 drug substance and drug product. In conclusion, ring-chain tautomeric structures are predominately formed under acidic conditions, and the additional peaks observed in LC during organic impurity determination were found to originate from ring-chain closed tautomers in equilibria with the parent open form compound. Hence, the closed and open tautomer forms should all be considered as the same compound.