Structural Basis of AZD9291 Selectivity for EGFR T790M.

AZD9291 (Osimertinib) is highly effective in treating EGFR-mutated non-small-cell lung cancers (NSCLCs) with T790M-mediated drug resistance. Despite the remarkable success of AZD9291, its binding pose with EGFR T790M remains unclear. Here, we report unbiased, atomic-level molecular dynamics (MD) simulations in which spontaneous association of AZD9291 with EGFR kinases having WT and T790M mutant gatekeepers was observed.

Structural insights into drug development strategy targeting EGFR T790M/C797S.

Treatment of non-small-cell lung cancers (NSCLCs) harboring primary EGFR oncogenic mutations such as L858R and exon 19 deletion delE746_A750 (Del-19) using gefitinib/erlotinib ultimately fails due to the emergence of T790M mutation. Though WZ4002/CO-1686/AZD9291 are effective in overcoming EGFR T790M by targeting Cys797 via covalent bonding, their efficacy is again limited due to the emergence of C797S mutation. New agents effectively inhibiting EGFR T790M without covalent linkage through Cys 797 may solve this problem.

Discovery of 4-((N-(2-(dimethylamino)ethyl)acrylamido)methyl)-N-(4-methyl-3-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)phenyl)benzamide (CHMFL-PDGFR-159) as a highly selective type II PDGFRα kinase inhibitor for PDGFRα driving chronic eosinophilic leukemia.

Through exploration of the non-highly conserved allosteric hydrophobic pocket generated by DFG-out shifting in the inactive conformation, we discovered a highly selective type II PDGFRα kinase inhibitor 15i (CHMFL-PDGFRα-159), which exhibited strong potency against purified PDGFRα (IC: 132 nM) but not structurally similar PDGFRβ, ABL, c-KIT and VEGFR2 kinases. In addition, it displayed a high selectivity profile (S score (10) = 0.02) at the concentration of 1 μM among 468 kinases/mutants in the KINOMEscan profiling.

Structural basis of mutant-selectivity and drug-resistance related to CO-1686.

Non-small-cell lung cancers (NSCLCs) caused by activating mutations in the kinase domain of epidermal growth factor receptor (EGFR) initially respond to first-generation reversible drugs gefitinib and erlotinib. However, clinical efficacy is limited due to the development of drug-resistance that in more than half of the cases are driven by the secondary T790M mutation. CO-1686 is one of the third generation irreversible inhibitors that inhibits EGFR activating mutants, including those with concurrent T790M, while avoiding the off-target toxicity owing to inhibition of wild-type EGFR in treating EGFR mutation-positive NSCLCs.

Structural pharmacological studies on EGFR T790M/C797S.

Drug-resistance is a major challenge in targeted therapy of EGFR mutated non-small cell lung cancers (NSCLCs). The third-generation irreversible inhibitors such as AZD9291, CO-1686 and WZ4002 can overcome EGFR T790M drug-resistance mutant through covalent binding through Cys 797, but ultimately lose their efficacy upon emergence of the new mutation C797S. To develop new reversible inhibitors not relying on covalent binding through Cys 797 is therefore urgently demanded.

Discovery and characterization of a novel irreversible EGFR mutants selective and potent kinase inhibitor CHMFL-EGFR-26 with a distinct binding mode.

EGFR T790M mutation accounts for about 40-55% drug resistance for the first generation EGFR kinase inhibitors in the NSCLC. Starting from ibrutinib, a highly potent irreversible BTK kinase inhibitor, which was also found to be moderately active to EGFR T790M mutant, we discovered a highly potent irreversible EGFR inhibitor CHMFL-EGFR-26, which is selectively potent against EGFR mutants including L858R, del19, and L858R/T790M. It displayed proper selectivity window between the EGFR mutants and the wide-type.

Discovery of (R)-1-(3-(4-Amino-3-(3-chloro-4-(pyridin-2-ylmethoxy)phenyl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)piperidin-1-yl)prop-2-en-1-one (CHMFL-EGFR-202) as a Novel Irreversible EGFR Mutant Kinase Inhibitor with a Distinct Binding Mode.

On the basis of Ibrutinib's core pharmacophore, which was moderately active to EGFR T790M mutant, we discovered novel epidermal growth factor receptor (EGFR) inhibitor compound 19 (CHMFL-EGFR-202), which potently inhibited EGFR primary mutants (L858R, del19) and drug-resistant mutant L858R/T790M. Compound 19 displayed a good selectivity profile among 468 kinases/mutants tested in the KINOMEscan assay (S score (1) = 0.02).

A structure-guided optimization of pyrido[2,3-d]pyrimidin-7-ones as selective inhibitors of EGFR mutant with improved pharmacokinetic properties.

Structural optimization of pyrido[2,3-d]pyrimidin-7-ones was conducted to yield a series of new selective EGFR inhibitors with improved pharmacokinetic properties. One of the most promising compound 9s potently suppressed EGFR kinase and inhibited the proliferation of H1975 cells with IC values of 2.0 nM and 40 nM, respectively.

Ibrutinib targets mutant-EGFR kinase with a distinct binding conformation.

Ibrutinib, a clinically approved irreversible BTK kinase inhibitor for Mantle Cell Lymphoma (MCL) and Chronic Lymphocytic Leukemia (CLL) etc, has been reported to be potent against EGFR mutant kinase and currently being evaluated in clinic for Non Small Cell Lung Cancer (NSCLC). Through EGFR wt/mutant engineered isogenic BaF3 cell lines we confirmed the irreversible binding mode of Ibrutinib with EGFR wt/mutant kinase via Cys797. However, comparing to typical irreversible EGFR inhibitor, such as WZ4002, the washing-out experiments revealed a much less efficient covalent binding for Ibrutinib.

Structural and biochemical studies of the PDGFRA kinase domain.

Platelet-derived growth factor receptor α (PDGFRA) is a Type III receptor tyrosine kinase, and this kinase is a target for treatment of gastrointestinal stromal tumors (GIST) as it is frequently mutated in these cancers. Most of the mutations that cause constitutive activation of PDGFRA occur in either the activation loop (A-loop) or in the juxtamembrane (JM) domain, such as the mutations D842V or V561D respectively. Treatment of PDGFRA-mutated GIST with imatinib is successful in some cases, but the D842V mutation is imatinib-resistant.

Ibrutinib selectively and irreversibly targets EGFR (L858R, Del19) mutant but is moderately resistant to EGFR (T790M) mutant NSCLC Cells.

Through comprehensive comparison study, we found that ibrutinib, a clinically approved covalent BTK kinase inhibitor, was highly active against EGFR (L858R, del19) mutant driven NSCLC cells, but moderately active to the T790M 'gatekeeper' mutant cells and not active to wild-type EGFR NSCLC cells. Ibrutinib strongly affected EGFR mediated signaling pathways and induced apoptosis and cell cycle arrest (G0/G1) in mutant EGFR but not wt EGFR cells. However, ibrutinib only slowed down tumor progression in PC-9 and H1975 xenograft models.