19F NMR viewed through two different lenses: ligand-observed and protein-observed 19F NMR applications for fragment-based drug discovery.

Caroline R Buchholz,William C K Pomerantz

doi:10.1039/d1cb00085c

Abstract

19F NMR has emerged as a powerful tool in drug discovery, particularly in fragment-based screens. The favorable magnetic resonance properties of the fluorine-19 nucleus, the general absence of fluorine in biological settings, and its ready incorporation into both small molecules and biopolymers, has enabled multiple applications of 19F NMR using labeled small molecules and proteins in biophysical, biochemical, and cellular experiments. This review will cover developments in ligand-observed and protein-observed 19F NMR experiments tailored towards drug discovery with a focus on fragment screening. We also cover the key advances that have furthered the field in recent years, including quantitative, structural, and in-cell methodologies. Several case studies are described for each application to highlight areas for innovation and to further catalyze new NMR developments for using this versatile nucleus.

Highlights

The influence of fluorine at the chemistry and biology interfaceIn 2007 a comprehensive analysis by Muller et al showed that B20% of all pharmaceuticals contained at least one fluorine atom.[5]
This review will cover developments in ligand-observed and protein-observed 19F nuclear magnetic resonance spectroscopy (NMR) experiments tailored towards drug discovery with a focus on fragment screening
While 29% in 2011,10 percentages of fluorinated small molecule drugs increased to 47% in 2018,11 41% in 2019,12 and 33% in 2020.13 † This rise can in part be attributed to both an increased knowledge of new strategies for using fluorine in biomedicine,[14] new biomedical applications for organofluorine molecules,[3] and a significant increase in synthetic methods for fluorination.[15]

Summary

Introduction

In 2007 a comprehensive analysis by Muller et al showed that B20% of all pharmaceuticals contained at least one fluorine atom.[5]. NMR, was largely limited to the study of protein folding and molecular recognition of native substrates.[32] Concerns over the significant chemical shift anisotropy (CSA) leading to significantly broader resonances than fluorinated small molecules was one potential limitation for applying this approach to small molecule screening.[30,33] Despite this concern, the first analysis of small molecule agonists and antagonists with the b-adrenergic receptor was reported by Wuthrich and co-workers in 2012.34 The same year, the fluorinated KIX domain of coactivator CBP, was used in a preliminary demonstration of small molecule screening to discover inhibitors of protein– protein interactions.[35] The significant CSA challenge is beginning to be addressed through 19F–13C transverse relaxationoptimized spectroscopy (TROSY)-based NMR methods.[36] Improved cryo-probe designs for increasing both the sizerange of fluorinated proteins, the sensitivity of the NMR experiment, and the lack of a biological background offer exciting opportunities for in-cell NMR.[37,38] To date, both ligand-observed and protein-observed 19F NMR methods have become increasingly adopted in drug discovery applications with many opportunities for innovation. Readers are referred to several prior reviews on this subject.[19,60,61]

Ligand-observed 19F NMR

Protein-observed 19F NMR

Findings

Outlook and future directions