Oleanolic acid derivative alleviates cardiac fibrosis through inhibiting PTP1B activity and regulating AMPK/TGF-ß/Smads pathway.

Cardiac fibrosis (CF) in response to persistent exogenous stimuli or myocardial injury results in cardiovascular diseases (CVDs). Protein tyrosine phosphatase 1B (PTP1B) can promote collagen deposition through regulating AMPK/TGF-ß/Smads signaling pathway, and PTP1B knockout improves cardiac dysfunction against overload-induced heart failure. Oleanolic acid (OA) has been proven to be an inhibitor of PTP1B, and its anti-cardiac remodeling effects have been validated in different mouse models. To improve the bioactivity of OA and to clarify whether OA derivatives with stronger inhibition of PTP1B activity have greater prevention of cardiac remodeling than OA, four new OA derivatives were synthesized and among them, we found that compound B had better effects than OA in inhibiting cardiac fibrosis both in vivo in the isoproterenol (ISO)-induced mouse cardiac fibrosis and in vitro in the TGF-ß/ISO-induced 3T3 cells. Combining with the results of molecular docking, surface plasmon resonance and PTP1B activity assay, we reported that OA and compound B directly bound to PTP1B and inhibited its activity, and that compound B showed comparable binding capability but stronger inhibitory effect on PTP1B activity than OA. Moreover, compound B presented much greater effects on AMPK activation and TGF-ß/Smads inhibition than OA. Taken together, OA derivative compound B more significantly alleviated cardiac fibrosis than OA through much greater inhibition of PTP1B activity and thus much stronger regulation of AMPK/TGF-ß/Smads signaling pathway.

Optimization of Brigatinib as New Wild-Type Sparing Inhibitors of EGFRT790M/C797S Mutants.

A series of brigatinib derivatives were designed and synthesized as new potent and selective EGFRT790M/C797S inhibitors. One of the most potent and selective compounds 18k strongly suppressed the EGFRL858R/T790M/C797S and EGFR19Del/T790M/C797S kinases with IC50 values of 0.7 and 3.6 nM, respectively, which were over 54-fold more potent than the lead compound. 18k also demonstrated promising EGFRT790M/C797S mutant selectivity, and was 94-fold less potent against the wild type EGFR. A cocrystal structure of EGFRT790M/C797S with a close derivative 18f was solved to provide insight on the inhibitor's binding mode. Moreover, compound 18k was orally bioavailable and demonstrated highly desirable PK properties, making it a promising lead compound for further structural optimization.

A new ALK inhibitor overcomes resistance to first- and second-generation inhibitors in NSCLC.

More than 60% of nonsmall cell lung cancer (NSCLC) patients show a positive response to the first ALK inhibitor, crizotinib, which has been used as the standard treatment for newly diagnosed patients with ALK rearrangement. However, most patients inevitably develop crizotinib resistance due to acquired secondary mutations in the ALK kinase domain, such as the gatekeeper mutation L1196M and the most refractory mutation, G1202R. Here, we develop XMU-MP-5 as a new-generation ALK inhibitor to overcome crizotinib resistance mutations, including L1196M and G1202R. XMU-MP-5 blocks ALK signaling pathways and inhibits the proliferation of cells harboring either wild-type or mutant EML4-ALK in vitro and suppresses tumor growth in xenograft mouse models in vivo. Structural analysis provides insights into the mode of action of XMU-MP-5. In addition, XMU-MP-5 induces significant regression of lung tumors in two genetically engineered mouse (GEM) models, further demonstrating its pharmacological efficacy and potential for clinical application. These preclinical data support XMU-MP-5 as a novel selective ALK inhibitor with high potency and selectivity. XMU-MP-5 holds great promise as a new therapeutic against clinically relevant secondary ALK mutations.

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. Simulation-generated structural models suggest that the binding pose of AZD9291 with T790M differs from its binding pose with the WT, and that AZD9291 interacts extensively with the gatekeeper residue (Met 790) in T790M but not with Thr 790 in the WT, which explains why AZD9291 binds T790M with higher affinity. The MD simulation-generated models were confirmed by experimentally determined EGFR/T790M complex crystal structures. This work may facilitate the rational design of drugs that can overcome resistance mutations to AZD9291, and more generally it suggests the potential of using unbiased MD simulation to elucidate small-molecule binding poses.

Structure-Based Design of 5-Methylpyrimidopyridone Derivatives as New Wild-Type Sparing Inhibitors of the Epidermal Growth Factor Receptor Triple Mutant (EGFRL858R/T790M/C797S).

Tertiary EGFRC797S mutation induced resistance against osimertinib (1) is an emerging "unmet clinical need" for non-small-cell lung cancer (NSCLC) patients. A series of 5-methylpyrimidopyridone derivatives were designed and synthesized as new selective EGFRL858R/T790M/C797S inhibitors. A representative compound, 8r-B, exhibited an IC50 of 27.5 nM against the EGFRL858R/T790M/C797S mutant, while being a significantly less potent for EGFRWT (IC50 > 1.0 µM). Cocrystallographic structure determination and computational investigation were conducted to elucidate its target selectivity.

Discovery of JND3229 as a New EGFRC797S Mutant Inhibitor with In Vivo Monodrug Efficacy.

EGFRC797S mutation inducing resistance against third generation EGFR inhibitor drugs is an emerging "unmet clinical need" for nonsmall cell lung cancer patients. The pyrimidopyrimidinone derivative JND3229 was identified as a new highly potent EGFRC797S inhibitor with single digit nM potency. It also exhibited good in vitro and in vivo monodrug anticancer efficacy in a xenograft mouse model of BaF3/EGFR19D/T790M/C797S cells. A high-resolution X-ray crystallographic structure was also determined to elucidate the interactions between JND3229 and EGFRT790M/C797S. Our study provides an important structural and chemical basis for future development of new generation EGFRC797S inhibitors as anticancer drugs.

Crystal structure of EGFR T790M/C797S/V948R in complex with EAI045.

Lung cancer is the leading cause of cancer deaths. Epidermal growth factor receptor (EGFR) kinase domain mutations are a common cause of non-small cell lung cancers (NSCLCs), a major subtype of lung cancers. Patients harboring most of these mutations respond well to the anti-EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib initially, but soon develop resistance to them in about half of the cases due to the emergence of the gatekeeper mutation T790M. The third-generation TKIs such as AZD9291, HM61713, CO-1686 and WZ4002 can overcome T790M through covalent binding to the EGFR kinase through Cys 797, but ultimately lose their efficacy upon emergence of the C797S mutation that abolishes the covalent bonding. Therefore to develop new TKIs to overcome EGFR drug-resistant mutants harboring T790M/C797S is urgently demanded. EAI001 and EAI045 are a new type of EGFR TKIs that bind to EGFR reversibly and not relying on Cys 797. EAI045 in combination with cetuximab is effective in mouse models of lung cancer driven by EGFR L858R/T790M and L858R/T790M/C797S. Here we report the crystal structure of EGFR T790M/C797S/V948R in complex with EAI045, and compare it to EGFR T790M/V948R in complex with EAI001. The complex structure reveals why EAI045 binds tighter to EGFR than does EAI001, and why EAI001 and EAI045 prefer binding to EGFR T790M. The knowledge may facilitate future drug development studies targeting this very important cancer target.

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. We presented here crystal structures of EGFR activating/drug-resistant mutants in complex with a panel of reversible inhibitors along with mutagenesis and enzyme kinetic data. These data revealed a previously un-described hydrophobic clamp structure in the EGFR kinase which may be exploited to facilitate development of next generation drugs targeting EGFR T790M with or without concomitant C797S. Interestingly, mutations in the hydrophobic clamp that hinder drug binding often also weaken ATP binding and/or abolish kinase activity, thus do not readily result in resistance to the drugs.

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. Despite the remarkable success, the experimentally determined structure of this agent in complex with EGFR T790M remains unknown. In this study, we determined crystal structures of EGFR T790M or L858R mutants covalently bound by CO-1686. Based on these structural data, we can explain why CO-1686 irreversibly inhibits EGFR and selectively prefers T790M, which may help improving this or similar compounds, and explain why EGFR L718Q and L844V mutations incur resistance to this agent.

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. Gö6976 is a staurosporine-like reversible inhibitor targeting T790M while sparing the wild-type EGFR. In the present work, we reported the complex crystal structures of EGFR T790M/C797S + Gö6976 and T790M + Gö6976, along with enzyme kinetic data of EGFR wild-type, T790M and T790M/C797S. These data showed that the C797S mutation does not significantly alter the structure and function of the EGFR kinase, but increases the local hydrophilicity around residue 797. The complex crystal structures also elucidated the detailed binding mode of Gö6976 to EGFR and explained why this compound prefers binding to T790M mutant. These structural pharmacological data would facilitate future drug development studies.

Development of covalent inhibitors that can overcome resistance to first-generation FGFR kinase inhibitors.

The human FGF receptors (FGFRs) play critical roles in various human cancers, and several FGFR inhibitors are currently under clinical investigation. Resistance usually results from selection for mutant kinases that are impervious to the action of the drug or from up-regulation of compensatory signaling pathways. Preclinical studies have demonstrated that resistance to FGFR inhibitors can be acquired through mutations in the FGFR gatekeeper residue, as clinically observed for FGFR4 in embryonal rhabdomyosarcoma and neuroendocrine breast carcinomas. Here we report on the use of a structure-based drug design to develop two selective, next-generation covalent FGFR inhibitors, the FGFR irreversible inhibitors 2 (FIIN-2) and 3 (FIIN-3). To our knowledge, FIIN-2 and FIIN-3 are the first inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2, which confer resistance to first-generation clinical FGFR inhibitors such as NVP-BGJ398 and AZD4547. Because of the conformational flexibility of the reactive acrylamide substituent, FIIN-3 has the unprecedented ability to inhibit both the EGF receptor (EGFR) and FGFR covalently by targeting two distinct cysteine residues. We report the cocrystal structure of FGFR4 with FIIN-2, which unexpectedly exhibits a "DFG-out" covalent binding mode. The structural basis for dual FGFR and EGFR targeting by FIIN3 also is illustrated by crystal structures of FIIN-3 bound with FGFR4 V550L and EGFR L858R. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance and provide the first example, to our knowledge, of a kinase inhibitor that covalently targets cysteines located in different positions within the ATP-binding pocket.