Outcomes in non-small cell lung cancer with uncommon epidermal growth factor receptor L858 substitutions under first-line epidermal growth factor receptor tyrosine kinase inhibitors: A large real-world cohort study.

Atypical L858R or other L858X mutations in the epidermal growth factor receptor (EGFR) gene, beyond the classical EGFRL858R mutation caused by c.2573 T > G, have been identified in non-small cell lung cancer (NSCLC), yet their genomic features and survival benefits with EGFR tyrosine kinase inhibitor (TKI) treatment have not been fully explored. We retrospectively enrolled 489 NSCLC patients with baseline tumor tissue/plasma samples carrying uncommon EGFRL858R (N = 124), EGFRL858Q/M (N = 17), or classical EGFRL858R mutations (N = 348). The comparison of molecular features was performed using treatment-naïve tumor tissues. Survival benefits and resistance mechanisms of first-line EGFR TKI treatment were studied in an advanced disease subcohort. NSCLCs harboring uncommon EGFRL858R had lower TP53 mutation prevalence (p = 0.04) and chromosome instability scores (p = 0.02) than those with classical EGFRL858R. Concomitant EGFRL861Q mutations were enriched in NSCLCs with EGFRL858Q/M (p < 0.01), with cooccurrence in those carrying EGFRL858M. Patients with uncommon EGFRL858R experienced improved progression-free survival (PFS) compared to those with classical EGFRL858R (median: 13.0 vs. 10.0 months, hazard ratio [HR]: 0.57, 95% confidence interval [CI]: 0.41-0.80). The association remained significant when adjusting for sex, age, histological subtype, TKI category, and anti-vascular therapy (HR: 0.55, 95% CI: 0.39-0.77). Furthermore, EGFRL858Q/M patients showed enhanced first-line PFS (vs. classical EGFRL858R, HR: 0.26, 95% CI: 0.10-0.67), potentially benefiting more from afatinib. Additionally, NSCLCs with uncommon EGFRL858R and classical EGFRL858R had similar resistance profiles to EGFR TKIs. In conclusion, NSCLCs carrying atypical EGFR L858 aberrations, which had fewer TP53 mutations and higher chromosome stability, exhibited improved PFS under first-line EGFR TKIs than those with the classical EGFRL858R.

Exploring the structural activity relationship of the Osimertinib: A covalent inhibitor of double mutant EGFRL858R/T790M tyrosine kinase for the treatment of Non-Small Cell Lung Cancer (NSCLC).

The USFDA granted regular approval to Osimertinib (AZD9291) on March 2017, for treating individuals with metastatic Non-Small Cell Lung Cancer having EGFR T790M mutation. Clinically, Osimertinib stands at the forefront for the treatment of patients with Non-Small Cell Lung Cancer. Osimertinib forms a covalent bond with the Cys797 residue and predominantly spares binding to WT-EGFR, thereby reducing toxicity and enabling the administration of doses that effectively inhibit T790M. However, a high percentage of patients treated with Osimertinib (AZD9291) developed a tertiary cysteine797 to serine797 (C797S) mutation in the EGFR kinase domain, rendering resistance to it. This comprehensive review sheds light on the chemistry, computational aspects, structural features, and expansive spectrum of biological activities of Osimertinib and its analogues. The in-depth exploration of these facets serves as a valuable resource for medicinal chemists, empowering them to design better Osimertinib analogues. This exhaustive study not only provides insights into improving potency but also emphasizes considerations for mutant selectivity and optimizing pharmacokinetic properties. This review acts as a guiding beacon for the strategic design and development of next-generation Osimertinib analogues.

Design, synthesis and biological evaluation of potent epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors against resistance mutation for lung cancer treatment.

In this study, we identified a newly synthesized compound 7o with potent inhibition on EGFR primary mutants (L858R, Del19) and drug-resistant mutant T790M with nanomolar IC50 values. 7o showed strong antiproliferative effects against EGFR mutant-driven non-small cell lung cancer (NSCLC) cells such as H1975, PC-9 and HCC827, over cells expressing EGFRWT. Molecular docking was performed to investigate the possible binding modes of 7o inside the binding site of EGFRL858R/T790M and EGFRWT. Analysis of cell cycle evidenced that 7o induced cell cycle arrest in G1 phases in the EGFR mutant cells, H1975 and PC-9, which resulted in decreased S-phase populations. Moreover, compound 7o induced cancer cell apoptosis in in vitro assays. In addition, 7o inhibited cellular phosphorylation of EGFR. In vivo, oral administration of 7o caused rapid tumor regression in H1975 xenograft model. Therefore, 7o might deserve further optimization as cancer treatment agent for EGFR mutant-driven NSCLC.

The new N2, N4-diphenylpyridine-2,4-diamine deuterated derivatives as EGFR inhibitors to overcome C797S-mediated resistance.

A series of new deuterated and non-deuterated N2, N4-diphenylpyridine - 2,4-diamine derivatives were synthesized and evaluated as EGFR C797S-mediated resistance inhibitors. Most of these compounds exhibited potent antiproliferative activity against Baf3-EGFR L858R/T790M/C797S and Baf3-EGFR Del19/T790M/C797S cancel cell lines, with IC50 values in the nanomolar concentration range. Among them, compound 14l represented the most active compound with IC50 values of 8-11 nM. Interestingly, metabolic stability assay with rat liver microsomes indicated that the half-life of the deuterated derivative 14o was significantly increased compared to that of 14l. In xenograft mice models, 14o inhibited tumor growth with excellent inhibitory rate of 75.1 % at the dosage of 40 mg/kg, comparing 73.2 % of the TGI with its non-deuterated compound 14l, at a dosage of 80 mg/kg. Mechanism studies revealed that 14o was a potent EGFR L858R/T790M/C797S and EGFR Del19/T790M/C797S kinase inhibitor, which could downregulate the protein phosphorylation of EGFR and m-TOR signaling pathways, arrest cell cycle at G2/M phase by affecting the expression of CDC25C, and promote cell apoptosis by regulating the expression of cleaved caspase-3. In summary, 14o could serve as a promising deuterated compound for the development of highly efficient anticancer agents.

Rational design and synthesis of 2,4-dichloro-6-methyl pyrimidine derivatives as potential selective EGFRT790M/L858R inhibitors for the treatment of non-small cell lung cancer.

Many patients with non-small cell lung cancer (NSCLC) initially benefit from epidermal growth factor receptor (EGFR) targeted therapy. Unfortunately, varying degrees of resistance or side effects eventually develop. Overcoming and preventing the resistance and side effects of EGFR inhibitors has become a hot topic of research today. Based on the previous studies on AZD-9291, we designed and synthesized two series of 2,4-dichloro-6-methylpyrimidine derivatives, 19 compounds in total, as potential inhibitors of the EGFR kinase. The most promising compound, L-18, showed better inhibitory activity (81.9%) and selectivity against EGFRT790M/L858R kinase. In addition, L-18 showed strong antiproliferative activity against H1975 cells with an IC50 value of 0.65 ± 0.06 µM and no toxicity to normal cells (LO-2). L-18 was able to dose-dependently induce the apoptosis of H1975 cells and produced a cell-cycle-blocking effect, and it can also dose-dependently inhibit the migration and invasion of H1975 cells. L-18 also showed in vivo anticancer efficacy in H1975 cells xenograft mice. We also performed a series of in vivo and in vitro toxicological evaluations of compound L-18, which did not cause obvious injury in mice during administration. These results suggest that L-18 may be a promising drug candidate that warrants further investigation.

Almonertinib Combined with Anlotinib and Temozolomide in a Patient with Recurrent Glioblastoma with EGFR L858R Mutation.

Glioblastoma (GBM) is the most common primary brain tumor, and patients with GBM have a universally poor prognosis. Genomic profiling has detected epidermal growth factor receptor (EGFR) gene alterations in more than half of GBMs. Major genetic events include amplification and mutation of EGFR. Interestingly, we identified an EGFR p.L858R mutation in a patient with recurrent GBM for the first time. Based on the genetic testing results, almonertinib combined with anlotinib and temozolomide was administered and obtained 12 months of progression-free survival after the diagnosis of recurrence as the fourth-line treatment. This is the first report that an EGFR p.L858R mutation was identified in a patient with recurrent GBM. Furthermore, this case report represents the first study applying the third-generation TKI inhibitor almonertinib in the treatment of recurrent GBM. The results of this study indicate that EGFR might be a new marker for the treatment of GBM with almonertinib.

Gefitinib, an effective treatment option for patients with pulmonary enteric adenocarcinoma harboring compound EGFR L858R and A871G mutation.

Pulmonary enteric adenocarcinoma (PEAC) is a rare lung adenocarcinoma with morphological and immunohistochemical similarities to colorectal adenocarcinoma and intestinal differentiation. PEAC belongs to the group of non-small-cell lung carcinoma (NSCLC) and is defined as having a more than 50% intestinal differentiation component. We report a postoperative (T4N2M0 stage IIIb) PEAC patient with EGFR L858R + A871G combined mutation. Following surgery, the patient underwent treatment with the first-generation EGFR-TKI, gefitinib, and achieved an impressive 5-year progression-free survival (PFS). This suggests that gefitinib may serve as an effective treatment option for PEAC patients with EGFR L858R + A871G compound mutations.

Biological Difference between L858R and Exon 19 Deletion Contributes to Recurrence-Free Survival of Resected Non-Small Cell Lung Cancer.

INTRODUCTION: The differences in biological characteristics among different genotypes of classical EGFR mutations have not been clarified. This study aimed to clarify the clinical and biological differences between L858R and 19 deletion in NSCLC. METHODS: We analyzed a cohort of 191 consecutive cases of surgically resected NSCLC harboring EGFR driver mutations (L858R or 19 deletion) in which curative resection was performed in Aichi Cancer Center Hospital, Nagoya, Japan, from January 2006 to September 2021 and in which recurrence subsequently developed. We also subjected 61 surgically resected NSCLC specimens harboring EGFR driver mutations (L858R or 19 deletion) to an RNA sequencing analysis. RESULTS: In patients with stage I disease, the median time to recurrence did not differ to a statistically significant extent between the types of EGFR mutations; however, among those with stage II and III disease, the median time to recurrence in patients with the L858R genotype tended to be shorter in comparison to those with 19 deletion (log-rank test, p = 0.47 and 0.46, respectively). In comparison to 19 deletion tumors, L858R tumors had higher cytological malignancy (e.g., mitotic ability) and showed stronger immunogenicity. CONCLUSION: L858R and 19 deletion tumors are likely to have a slight difference in the time to recurrence. They suggest that even in EGFR driver tumors, which are treated as the same disease category, the biological characteristics of the tumors are different, which may leave room for innovations in postoperative treatment and treatment at recurrence.

Exploration of novel dihydroquinoxalinone derivatives as EGFRL858R/T790M tyrosine kinase inhibitors for the treatment of non-small-cell lung cancer.

To overcome or delay the drug-resistance of first-generation epidermal growth factor receptor (EGFR) kinase inhibitors and non-selectivity toxicity mediated by second-generation inhibitors, splicing principle was employed to design and synthesize a series of Osimertinib derivatives containing dihydroquinoxalinone (8-30) as the novel third-generation inhibitors against double mutant L858R/T790M in EGFR. Among them, compound 29 showed excellent kinase inhibitory activity against EGFRL858R/T790M with an IC50 value of 0.55 ± 0.02 nM and potent anti-proliferative activity against H1975 cells with an IC50 value of 5.88 ± 0.07 nM. Moreover, the strong down-regulation effect of EGFR-mediated signaling pathways and the promotion of apoptosis in H1975 cells confirmed its potent antitumor activities. Compound 29 was also demonstrated with good ADME profile in various in vitro assays. Further in vivo studies confirmed that compound 29 could suppress the growth of xenograft tumors. These results verified that compound 29 would be a promising lead compound for targeting drug-resistant EGFR mutations.

Synthesis and Evaluation of 2-Amine-4-oxyphosaniline Pyrimidine Derivatives as EGFR L858R/T790M/C797S Mutant Inhibitors.

Epidermal growth factor receptor (EGFR) C797S mutation leads to Osimertinib drug resistance by disturbing the covalent biding of Michael acceptor group to the Cys797 residue in the ATP biding cleft. In this manuscript, a class of 2-amine-4-oxyphosaniline pyrimidine derivatives were designed, synthesized and evaluated as new noncovalent reversible EGFR inhibitors against L858R/T790M/C797S (CTL) triple mutant. The kinases inhibitiory activity evaluation showed that four compounds exhibited significant inhibitory activities against CTL (IC50 < 30 nM). In particularly, the most promising compound 7a showed excellent enzymatic inhibitory activity against CTL with IC50 value of 9.9 nM, which was more potent than control compound Osimertinib. Moreover, cell proliferation assays indicated that 7a effectively inhibited H1975-EGFR L858R/T790M/C797S with IC50 value of 0.33 µM. Furthermore, compound 7a displayed good metabolic stabilities in human, rat and mouse liver microsomes, and the putative biding mode of compound 7a with ATP was revealed by molecular docking study. These findings strongly indicated that compound 7a was a promising L858R/T790M/C797S mutant EGFR inhibitor.

Detection of EGFR gene with a droplet digital PCR chip integrating a double-layer glass reservoir.

The lack of reliable and practical method for detecting rare hot mutation of epidermal growth factor receptor (EGFR) in circulating tumor DNA (ctDNA) for lung cancer has remained a challenge for general clinical application due to excess wild type DNA in clinical samples. In this study, we developed a droplet digital PCR (ddPCR) platform, integrating a PDMS chip and double-layer glass reservoir. The duplex T-junction droplet generators in PDMS chip can produce about one million uniform droplets of 4.187 pL within ∼10 min, which were then stored in the glass reservoir. The double-layer glass reservoir can protect droplets from evaporation and breaking, solving the problem of instability during thermal-cycling. The quantitative capabilities of the ddPCR chip were evaluated by testing EGFR exon gene 21, with a good linear correlation in the wide range of 101 to 106 copies/µL (R2 = 0.9998). We then demonstrated that the proposed ddPCR device can recognize rare EGFR L858R mutation under a background of 106 copies/µL wild-type DNA at a sensitivity of 0.0001%. Finally, we demonstrated this ddPCR platform could identify low amount of EGFR L858R mutation in ctDNA and CTCs of patients with lung cancer.

Highly sensitive detection of EGFR L858R mutation at the mRNA level.

The missense mutation EGFR L858R implies increased sensitivity to EGFR tyrosine kinase inhibitor (TKIs) therapy, despite a significant non-response rate. Currently, detection of EGFR L858R mutation is mostly DNA based, therefore, the allele-specific expression level of the mutated gene and its clinical relevance is hidden. Based on the extendable blocking probes and hot-start protocol for reverse transcription, we have developed and validated a novel one-step realtime RT-PCR assay that enables detection of EGFR L858R mutation at the mRNA level. This RNA-based assay was able to detect the EGFR L858R mutation in a 10,000-fold excess of its wildtype counterpart, indicating an analytical sensitivity of 0.01%. In comparison to the reference DNA-based assay, the RNA-based assay further detected the EGFR L858R mutation in significantly additional formalin-fixed paraffin-embedded (FFPE) samples (19.2% vs 15.0%). Interestingly, our data showed that the relative mRNA levels of EGFR L858R mutation varied greatly in tumor tissues (∼4 logs); and the circulating mRNA of EGFR L858R mutation was detectable in plasma of NSCLC patients. This novel RNA-based PCR assay provides a simple and ultrasensitive tool for detection of EGFR L858R mutation at the mRNA level as a new class of biomarkers.

Design, synthesis, and biological evaluation of 2-arylamino-4-(piperidin-4-yloxy)pyrimidines as potent EGFRT790M/L858R inhibitors to treat non-small cell lung cancer.

Three types of 2-arylamino-4-(piperidin-4-yloxy)pyrimidines (I-III) were designed and synthesized as covalent EGFR(epidermal growth factor receptor)T790M/L858R inhibitors by replacement of the common reported 4-(3-amino)phenoxyl moiety with 4-(4-hydroxy)piperidine-4-oxyl, and the introduction of fused-thiophene or -pyrrole on the pyrimidine core to strategically achieve conformational restriction. According to our biological evaluation, it was found that compound 9i could potently suppress EGFRT790M/L858R kinase and H1975 cell proliferation, with IC50 values of 4.902 nM and 0.6210 µM, respectively. Further study showed that 9i not only demonstrated highly selective inhibitory effects toward EGFRT790M/L858R over wild-type EGFR (EGFRWT), but it also had low cytotoxicity against normal HBE(human bronchial epithelial) and L-02 cells. Action mechanism studies showed that 9i effectively hindered cell migration and promoted apoptosis by AO(Acridine Orange)/EB(Ethidium Bromide) staining. These data would provide important clues for the screening of novel covalent EGFRT790M/L858R inhibitors for non-small cell lung cancer (NSCLC) treatment.

Discovery of novel 4-arylamino-quinazoline derivatives as EGFRL858R/T790M inhibitors with the potential to inhibit the non-small cell lung cancers.

Three series of quinazoline derivatives (7a-j, 8a-o, 9a-l) were designed and synthesized as EGFRL858R/T790M inhibitors. Series 7a-j and 8a-o are urea and thiourea derivatives while category 9a-l contain the Michael receptor active warhead. Most of the compounds exhibited excellent anti-proliferative activity in vitro against several cancer cell lines, including non-small cell lung cancer (NSCLC) cell lines A549 and H1975, among which 14 compounds had strong antiproliferative activity against A549 and H1975 cancer cells. What's more, they also showed moderate to excellent kinase inhibitory activity against EGFRWT and EGFRL858R/T790M. 8o exhibited the best kinase inhibitory activity with IC50 values of 0.8, 2.7 nM against EGFRWT and EGFRL858R/T790M, respectively. Moreover, AO single staining and Annexin V-FITC/PI staining results also indicated that both 8o and 9b significantly induced apoptosis in A549 cells. 8o arrested the cell cycle at S phase and 9b arrested the cell cycle at G1 phase.

Design, synthesis and biological evaluation of novel tumor hypoxia-activated EGFR tyrosine kinase inhibitors.

Hypoxia is widespread in solid tumors, such as NSCLC, and has become a very attractive target. On the basis of AZD9291 scaffold, novel hypoxia-targeted EGFR inhibitors without the acrylamide warhead but containing hypoxic reductive activation groups were described. Among them, compound JT21 exhibited impressive inhibitory activity (IC50 = 23 nM) against EGFRL858R/T790M and displayed about 21-fold inhibitory activity decrease against EGFRwt. Under hypoxia, JT21 exhibited more significant proliferation inhibitory activities against H1975 cells (IC50 = 7.39 ± 2.20 nM) and HCC827 cells (IC50 = 5.88 ± 0.85 nM) than that of AZD9291, which was about 5 times more effective than normoxia activities. Meanwhile, the weak inhibition effects on A549 and BEAS-2B cells suggested JT21 might be a selective inhibitor for EGFR mutations with low toxicity. Furthermore, JT21 could induce apoptosis of H1975 cells under hypoxia and showed good bio-reductive property.

Building 2D classification models and 3D CoMSIA models on small-molecule inhibitors of both wild-type and T790M/L858R double-mutant EGFR.

Epidermal growth factor receptor (EGFR) has received widespread attention because it is an important target for anticancer drug design. Mutations in the EGFR, especially the T790M/L858R double mutation, have made cancer treatment more difficult. We herein built the structure-activity relationship models of small-molecule inhibitors on wild-type and T790M/L858R double-mutant EGFR with a whole dataset of 379 compounds. For 2D classification models, we used ECFP4 fingerprints to build support vector machine and random forest models and used SMILES to build self-attention recurrent neural network models. Each of all six models resulted in an accuracy of above 0.87 and the Matthews correlation coefficient value of above 0.76 on the test set, respectively. We concluded that inhibitors containing anilinoquinoline and methoxy or fluoro phenyl are highly active against wild EGFR. Substructures such as anilinopyrimidine, acrylamide, amino phenyl, methoxy phenyl, and thienopyrimidinyl amide appeared more in highly active inhibitors against double-mutant EGFR. We also used self-organizing map to cluster the inhibitors into six subsets based on ECFP4 fingerprints and analyzed the activity characteristics of different scaffolds in each subset. Among them, three datasets, which are based on pteridin, anilinopyrimidine, and anilinoquinoline scaffold, were selected to build 3D comparative molecular similarity analysis models individually. Models with the leave-one-out coefficient of determination (q2) above 0.65 were selected, and five descriptor types (steric, electrostatic, hydrophobic, donor, and acceptor) were used to study the effects of side chains of inhibitors on the activity against wild-type and mutant-type EGFR.

Quinoxalinones as A Novel Inhibitor Scaffold for EGFR (L858R/T790M/C797S) Tyrosine Kinase: Molecular Docking, Biological Evaluations, and Computational Insights.

Combating acquired drug resistance of EGFR tyrosine kinase (TK) is a great challenge and an urgent necessity in the management of non-small cell lung cancers. The advanced EGFR (L858R/T790M/C797S) triple mutation has been recently reported, and there have been no specific drugs approved for this strain. Therefore, our research aimed to search for effective agents that could impede the function of EGFR (L858R/T790M/C797S) TK by the integration of in silico and in vitro approaches. Our in-house quinoxalinone-containing compounds were screened through molecular docking and their biological activity was then verified by enzyme- and cell-based assay. We found that the four quinoxalinone-containing compounds including CPD4, CPD15, CPD16, and CPD21 were promising to be novel EGFR (L858R/T790M/C797S) TK inhibitors. The IC50 values measured by the enzyme-based assay were 3.04 ± 1.24 nM; 6.50 ± 3.02 nM,10.50 ± 1.10 nM; and 3.81 ± 1.80 nM, respectively, which are at a similar level to a reference drug; osimertinib (8.93 ± 3.01 nM). Besides that, they displayed cytotoxic effects on a lung cancer cell line (H1975) with IC50 values in the range of 3.47 to 79.43 µM. In this proposed study, we found that all screened compounds could interact with M793 at the hinge regions and two mutated residues including M790 and S797; which may be the main reason supporting the inhibitory activity in vitro. The structural dynamics revealed that the screened compounds have sufficient non-native contacts with surrounding amino acids and could be well-buried in the binding site's cleft. In addition, all predicted physicochemical parameters were favorable to be drug-like based on Lipinski's rule of five, and no extreme violation of toxicity features was found. Altogether, this study proposes a novel EGFR (L858R/T790M/C797S) TK inhibitor scaffold and provides a detailed understanding of compounds' recognition and susceptibility at the molecular level.

Icotinib, an effective treatment option for patients with lung adenocarcinoma harboring compound EGFR L858R and A871G mutation.

Compound epidermal growth factor receptor (EGFR) mutations are defined as double or multiple independent mutations of the EGFR tyrosine kinase domain (TKD), in which an EGFR-tyrosine kinase inhibitor (TKI)-sensitizing mutation is identified together with a mutation of unclarified clinical significance. Lung adenocarcinoma with compound EGFR mutation shows poor clinical response to EGFR-TKIs. Kobayashi et al. reported a non-small-cell lung cancer (NSCLC) patient whose tumor had EGFR exon21 L858R/A871G mutation presented rapid disease progression to erlotinib. However, in this case, we present an EGFR exon21 L858R/A871G mutation patient exerted significant benefit to icotinib, another first-generation EGFR-TKI, indicating that different EGFR-TKIs have diversiform sensitive sites and therapeutic effects, consistent mutation sites might achieve heterogeneous benefits from different EGFR-TKIs. Our case report provides promising EGFR-TKI for clinical treatment with EGFR exon21 L858R/A871G mutation in NSCLC. More dedicated efforts are needed to clarify their biologic effects on disease course and drug responsiveness.

Discovery and optimization of covalent EGFR T790M/L858R mutant inhibitors.

Epidermal growth factor receptor (EGFR) inhibitors have clinical utility in the treatment of non-small cell lung cancer (NSCLC) patients. Despite encouraging clinical efficacy with these agents, many patients develop resistance due to sensitizing (or activating) mutations ultimately leading to disease progression. In the majority of the cases, this resistance is due to the T790M mutation and frequently coexisting L858R. In addition, EGFR wild type receptor inhibition can lead to on target related dose limiting toxicities such as rash and diarrhea. We describe herein the identification of a mutant selective lead compound 12, an irreversible covalent inhibitor of EGFR T790M/L858R resistance mutations with selectivity over the wild type form. Significant tumor growth inhibition in preclinical models was observed with this lead.

Synthesis and evaluation of azalamellarin N and its A-ring-modified analogues as non-covalent inhibitors of the EGFR T790M/L858R mutant.

Azalamellarin N, a synthetic lactam congener of the marine natural product lamellarin N, and its A-ring-modified analogues were synthesized and evaluated as potent and non-covalent inhibitors of the drug-resistant epidermal growth factor receptor T790M/L858R mutant. An in vitro tyrosine kinase assay indicated that the inhibitory activities of the synthetic azalamellarin analogues were higher than those of the corresponding lamellarins. The azalamellarin analogue bearing two 3-(dimethylamino)propoxy groups at C20- and C21-positions exhibited the highest activity and selectivity against the mutant kinase [IC50 (T790M/L858R) = 1.7 nM; IC50 (WT) = 4.6 nM]. The inhibitory activity was attributed to the hydrogen bonding interaction between the lactam NH group of the B-ring and carbonyl group of a methionine residue.