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Updated: Apr 14, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Conformational isomerism in solid state of AMG 853--structure studies using solid-state nuclear magnetic resonance
Y-H Kiang1, Karthik Nagapudi1, Tian Wu1
1Process Development, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California, 91320.
Two coexisting conformational isomers of AMG 853, a dual DP and CRTH2 antagonist, were identified in the crystal lattice. Solid-state NMR and X-ray diffraction confirmed their presence and disorder in the fluorine atom's crystal structure.
Area of Science:
- Solid-state chemistry
- Crystallography
- Pharmaceutical analysis
Background:
- AMG 853 is a dual antagonist of DP and CRTH2, previously investigated for asthma treatment.
- Solid-state characterization is crucial for understanding drug behavior and stability.
Purpose of the Study:
- To investigate an additional resonance peak in the (19)F solid-state NMR spectrum of AMG 853.
- To identify and characterize conformational isomers present in the crystal lattice of AMG 853.
Main Methods:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, specifically (19)F NMR.
- Single-crystal and high-resolution powder X-ray diffraction (XRD).
Main Results:
- Two conformational isomers of AMG 853 were identified coexisting in the crystal lattice over a continuous composition range.
- The isomers differ by a 180° flip of the chloro-fluorophenyl moiety's aromatic ring.
- NMR data correlated well with crystal structure disorder, specifically the fluorine atom's position.
Conclusions:
- The coexistence of conformational isomers in AMG 853's crystal lattice was confirmed.
- Solid-state NMR is a valuable tool for quantifying isomer ratios and assessing crystal disorder.
- Understanding these structural details is important for pharmaceutical development.
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