Jonas Lategahn

Targeting Drug Resistance in EGFR with Covalent Inhibitors: A Structure-Based Design Approach.

Receptor tyrosine kinases represent one of the prime targets in cancer therapy, as the dysregulation of these elementary transducers of extracellular signals, like the epidermal growth factor receptor (EGFR), contributes to the onset of cancer, such as non-small cell lung cancer (NSCLC). Strong efforts were directed to the development of irreversible inhibitors and led to compound CO-1686, which takes advantage of increased residence time at EGFR by alkylating Cys797 and thereby preventing toxic effects. Here, we present a structure-based approach, rationalized by subsequent computational analysis of conformational ligand ensembles in solution, to design novel and irreversible EGFR inhibitors based on a screening hit that was identified in a phenotype screen of 80 NSCLC cell lines against approximately 1500 compounds. Using protein X-ray crystallography, we deciphered the binding mode in engineered cSrc (T338M/S345C), a validated model system for EGFR-T790M, which constituted the basis for further rational design approaches. Chemical synthesis led to further compound collections that revealed increased biochemical potency and, in part, selectivity toward mutated (L858R and L858R/T790M) vs nonmutated EGFR. Further cell-based and kinetic studies were performed to substantiate our initial findings. Utilizing proteolytic digestion and nano-LC-MS/MS analysis, we confirmed the alkylation of Cys797.

Hope and Disappointment: Covalent Inhibitors to Overcome Drug Resistance in Non-Small Cell Lung Cancer

In the last five years, the detailed understanding of how to overcome T790M drug resistance in non-small cell lung cancer (NSCLC) has culminated in the development of a third-generation of covalent EGFR inhibitors with excellent clinical outcomes. However, the emergence of a newly discovered acquired drug resistance challenges the concept of small molecule targeted cancer therapy in NSCLC.

Insight into the Inhibition of Drug-Resistant Mutants of the Receptor Tyrosine Kinase EGFR.

Targeting acquired drug resistance represents the major challenge in the treatment of EGFR-driven non-small-cell lung cancer (NSCLC). Herein, we describe the structure-based design, synthesis, and biological evaluation of a novel class of covalent EGFR inhibitors that exhibit excellent inhibition of EGFR-mutant drug-resistant cells. Protein X-ray crystallography combined with detailed kinetic studies led to a deeper understanding of the mode of inhibition of EGFR-T790M and provided insight into the key principles for effective inhibition of the recently discovered tertiary mutation at EGFR-C797S.

Indazole-Based Covalent Inhibitors To Target Drug-Resistant Epidermal Growth Factor Receptor

The specific targeting of oncogenic mutant epidermal growth factor receptor (EGFR) is a breakthrough in targeted cancer therapy and marks a drastic change in the treatment of non-small cell lung cancer (NSCLC). The recurrent emergence of resistance to these targeted drugs requires the development of novel chemical entities that efficiently inhibit drug-resistant EGFR. Herein, we report the optimization process for a hit compound that has emerged from a phenotypic screen resulting in indazole-based compounds. These inhibitors are conformationally less flexible, target gatekeeper mutated drug-resistant EGFR-L858R/T790M, and covalently alkylate Cys797. Western blot analysis, as well as characterization of the binding kinetics and kinase selectivity profiling, substantiates our approach of targeting drug-resistant EGFR-L858R/T790M with inhibitors incorporating the indazole as hinge binder.

Trisubstituted Pyridinylimidazoles as Potent Inhibitors of the Clinically Resistant L858R/T790M/C797S EGFR Mutant: Targeting of Both Hydrophobic Regions and the Phosphate Binding Site

Inhibition of the epidermal growth factor receptor represents one of the most promising strategies in the treatment of lung cancer. Acquired resistance compromises the clinical efficacy of EGFR inhibitors during long-term treatment. The recently discovered EGFR-C797S mutation causes resistance against third-generation EGFR inhibitors. Here we present a rational approach based on extending the inhibition profile of a p38 MAP kinase inhibitor toward mutant EGFR inhibition. We used a privileged scaffold with proven cellular potency as well as in vivo efficacy and low toxicity. Guided by molecular modeling, we synthesized and studied the structure-activity relationship of 40 compounds against clinically relevant EGFR mutants. We successfully improved the cellular EGFR inhibition down to the low nanomolar range with covalently binding inhibitors against a gefitinib resistant T790M mutant cell line. We identified additional noncovalent interactions, which allowed us to develop metabolically stable inhibitors with high activities against the osimertinib resistant L858R/T790M/C797S mutant.

Lessons To Be Learned: The Molecular Basis of Kinase-Targeted Therapies and Drug Resistance in Non-Small Cell Lung Cancer

The treatment of non-small cell lung cancer (NSCLC) is currently experiencing a revolution. Over the last decade, the knowledge gained about the biochemical features of biomarkers and their predictive abilities has led to the development of targeted small-molecule inhibitors that present an alternative to harsh chemotherapy. The use of these new therapies has improved the quality of life and increased the survival of patients. The occurrence of inevitable drug resistance requires the constant development of precision medicine. The detailed understanding of the target biology and the search for innovative chemical approaches has encouraged investigations in this field. Herein, we review selected aspects of the molecular targets and present an overview of current topics and challenges in the rational development of small molecules to target NSCLC.

Structure-Guided Development of Covalent and Mutant-Selective Pyrazolopyrimidines to Target T790M Drug Resistance in Epidermal Growth Factor Receptor

Reversible epidermal growth factor receptor (EGFR) inhibitors prompt a beneficial clinical response in non-small cell lung cancer patients who harbor activating mutations in EGFR. However, resistance mutations, particularly the gatekeeper mutation T790M, limit this efficacy. Here, we describe a structure-guided development of a series of covalent and mutant-selective EGFR inhibitors that effectively target the T790M mutant. The pyrazolopyrimidine-based core differs structurally from that of aminopyrimidine-based third-generation EGFR inhibitors and therefore constitutes a new set of inhibitors that target this mechanism of drug resistance. These inhibitors exhibited strong inhibitory effects toward EGFR kinase activity and excellent inhibition of cell growth in the drug-resistant cell line H1975, without significantly affecting EGFR wild-type cell lines. Additionally, we present the in vitro ADME/DMPK parameters for a subset of the inhibitors as well as in vivo pharmacokinetics in mice for a candidate with promising activity profile.

RASPELD to Perform High-End Screening in an Academic Environment toward the Development of Cancer Therapeutics

The identification of compounds for dissecting biological functions and the development of novel drug molecules are central tasks that often require screening campaigns. However, the required architecture is cost‐ and time‐intensive. Herein we describe the devices and technologies that comprise a Robotics‐Assisted Screening Platform for Efficient Ligand Discovery (RASPELD), which we set up in an academic laboratory. RASPELD provides semi‐automated high‐end screening, and it can be maintained by graduate students. We demonstrate its successful application in biochemical and cellular screens for the identification and validation of bioactive chemical entities as candidate cancer‐relevant inhibitors. Specifically, we examined the interaction between a transcription factor, Nrf2, and its key regulator, Keap1. We also examined drug‐resistant mutants of the epidermal growth factor receptor (EGFR). Screening campaigns with more than 30 000 compounds were performed in a reasonable period of time. We identified the molecule RSL6586 as a starting point for hit optimization, which is currently ongoing.

An Unusual Intramolecular Halogen Bond Guides Conformational Selection.

PIK-75 is a phosphoinositide-3-kinase (PI3K) α-isoform-selective inhibitor with high potency. Although published structure-activity relationship data show the importance of the NO2 and the Br substituents in PIK-75, none of the published studies could correctly determine the underlying reason for their importance. In this publication, we report the first X-ray crystal structure of PIK-75 in complex with the kinase GSK-3β. The structure shows an unusual U-shaped conformation of PIK-75 within the active site of GSK-3β that is likely stabilized by an atypical intramolecular Br⋅⋅⋅NO2 halogen bond. NMR and MD simulations show that this conformation presumably also exists in solution and leads to a binding-competent preorganization of the PIK-75 molecule, thus explaining its high potency. We therefore suggest that the site-specific incorporation of halogen bonds could be generally used to design conformationally restricted bioactive substances with increased potencies.

C797S Resistance: The Undruggable EGFR Mutation in Non-Small Cell Lung Cancer?

The first evidence of osimertinib resistance mediated by the epidermal growth factor receptor (EGFR) mutation C797S was reported three years ago. Since then, no major breakthroughs have been achieved to target the clinically relevant mutant variant that impedes covalent bond formation with irreversible EGFR inhibitors. Although several biochemically active compounds have been described, only a few inhibitors that potently act on the cellular level or in vivo have been introduced so far. Herein, we give an overview of current approaches in the field and highlight the challenges that need to be addressed in future research projects to overcome the C797S-mediated drug resistance.