Addressing the Osimertinib Resistance Mutation EGFR-L858R/C797S with Reversible Aminopyrimidines.

Drug resistance mutations emerging during the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) inhibitors represent a major challenge in personalized cancer treatment and require constant development of new inhibitors. For the covalent irreversible EGFR inhibitor osimertinib, the predominant resistance mechanism is the acquired C797S mutation, which abolishes the covalent anchor point and thus results in a dramatic loss in potency. In this study, we present next-generation reversible EGFR inhibitors with the potential to overcome this EGFR-C797S resistance mutation. For this, we combined the reversible methylindole-aminopyrimidine scaffold known from osimertinib with the affinity driving isopropyl ester of mobocertinib. By occupying the hydrophobic back pocket, we were able to generate reversible inhibitors with subnanomolar activity against EGFR-L858R/C797S and EGFR-L858R/T790M/C797S with cellular activity on EGFR-L858R/C797S dependent Ba/F3 cells. Additionally, we were able to resolve cocrystal structures of these reversible aminopyrimidines, which will guide further inhibitor design toward C797S-mutated EGFR.

Insight into Targeting Exon20 Insertion Mutations of the Epidermal Growth Factor Receptor with Wild Type-Sparing Inhibitors.

Despite the clinical efficacy of epidermal growth factor receptor (EGFR) inhibitors, a subset of patients with non-small cell lung cancer displays insertion mutations in exon20 in EGFR and Her2 with limited treatment options. Here, we present the development and characterization of the novel covalent inhibitors LDC8201 and LDC0496 based on a 1H-pyrrolo[2,3-b]pyridine scaffold. They exhibited intense inhibitory potency toward EGFR and Her2 exon20 insertion mutations as well as selectivity over wild type EGFR and within the kinome. Complex crystal structures with the inhibitors and biochemical and cellular on-target activity document their favorable binding characteristics. Ultimately, we observed tumor shrinkage in mice engrafted with patient-derived EGFR-H773_V774insNPH mutant cells during treatment with LDC8201. Together, these results highlight the potential of covalent pyrrolopyridines as inhibitors to target exon20 insertion mutations.

Structure Defines Function: Clinically Relevant Mutations in ErbB Kinases.

The ErbB receptor tyrosine kinase family members EGFR (epidermal growth factor receptor) and Her2 are among the prominent mutated oncogenic drivers of non-small cell lung cancer (NSCLC). Their importance in proliferation, apoptosis, and cell death ultimately renders them hot targets in cancer therapy. Small-molecule tyrosine kinase inhibitors seem well suited to be tailor-made therapeutics for EGFR mutant NSCLC; however, drug resistance mutations limit their success. Against this background, the elucidation and visualization of the three-dimensional structure of cancer-related kinases provide valuable insights into their molecular functions. This field has undergone a revolution because X-ray crystal structure determinations aided structure-based drug design approaches and clarified the effect of activating and resistance-conferring mutations. Here, we present an overview of important mutations affecting EGFR and Her2 and highlight their influence on the kinase domain conformations and active site accessibility.

Complex Crystal Structures of EGFR with Third-Generation Kinase Inhibitors and Simultaneously Bound Allosteric Ligands.

Osimertinib is a third-generation tyrosine kinase inhibitor (TKI) and currently the gold-standard for the treatment of patients suffering from non-small cell lung cancer (NSCLC) harboring T790M-mutated epidermal growth factor receptor (EGFR). The outcome of the treatment, however, is limited by the emergence of the C797S resistance mutation. Allosteric inhibitors have a different mode of action and were developed to overcome this limitation. However, most of these innovative molecules are not effective as a single agent. Recently, mutated EGFR was successfully addressed with osimertinib combined with the allosteric inhibitor JBJ-04-125-02, but surprisingly, structural insights into their binding mode were lacking. Here, we present the first complex crystal structures of mutant EGFR in complex with third-generation inhibitors such as osimertinib and mavelertinib in the presence of simultaneously bound allosteric inhibitors. These structures highlight the possibility of further combinations targeting EGFR and lay the foundation for hybrid inhibitors as next-generation TKIs.

Targeting Her2-insYVMA with Covalent Inhibitors-A Focused Compound Screening and Structure-Based Design Approach.

Mutated or amplified Her2 serves as a driver of non-small cell lung cancer or mediates resistance toward the inhibition of its family member epidermal growth factor receptor with small-molecule inhibitors. To date, small-molecule inhibitors targeting Her2 which can be used in clinical routine are lacking, and therefore, the development of novel inhibitors was undertaken. In this study, the well-established pyrrolopyrimidine scaffold was modified with structural motifs identified from a screening campaign with more than 1600 compounds, which were applied against wild-type Her2 and its mutant variant Her2-A775_G776insYVMA. The resulting inhibitors were designed to covalently target a reactive cysteine in the binding site of Her2 and were further optimized by means of structure-based drug design utilizing a set of obtained complex crystal structures. In addition, the analysis of binding kinetics and absorption, distribution, metabolism, and excretion parameters as well as mass spectrometry experiments and western blot analysis substantiated our approach.

Inhibition of osimertinib-resistant epidermal growth factor receptor EGFR-T790M/C797S.

Precision medicine has revolutionized the treatment of patients in EGFR driven non-small cell lung cancer (NSCLC). Targeted drugs show high response rates in genetically defined subsets of cancer patients and markedly increase their progression-free survival as compared to conventional chemotherapy. However, recurrent acquired drug resistance limits the success of targeted drugs in long-term treatment and requires the constant development of novel efficient inhibitors of drug resistant cancer subtypes. Herein, we present covalent inhibitors of the drug resistant gatekeeper mutant EGFR-L858R/T790M based on the pyrrolopyrimidine scaffold. Biochemical and cellular characterization, as well as kinase selectivity profiling and western blot analysis, substantiate our approach. Moreover, the developed compounds possess high activity against multi drug resistant EGFR-L858R/T790M/C797S in biochemical assays due to their highly reversible binding character, that was revealed by characterization of the binding kinetics. In addition, we present the first X-ray crystal structures of covalent inhibitors in complex with C797S-mutated EGFR which provide detailed insight into their binding mode.