Fused in silico and bioactivity evaluation method for drug discovery: T001-10027877 was identified as an antiproliferative agent that targets EGFRT790M/C797S/L858R and EGFRT790M/L858R.

BACKGROUND: Facing the significant challenge of overcoming drug resistance in cancer treatment, particularly resistance caused by mutations in epidermal growth factor receptor (EGFR), the aim of our study was to identify potent EGFR inhibitors effective against the T790M/C797S/L858R mutant, a key player in resistance mechanisms. METHODS: Our integrated in silico approach harnessed machine learning, virtual screening, and activity evaluation techniques to screen 5105 compounds from three libraries, aiming to find candidates capable of overcoming the resistance conferred by the T790M and C797S mutations within EGFR. This methodical process narrowed the search down to six promising compounds for further examination. RESULTS: Kinase assays identified three compounds to which the T790M/C797S/L858R mutant exhibited increased sensitivity compared to the T790M/L858R mutant, highlighting the potential efficacy of these compounds against resistance mechanisms. Among them, T001-10027877 exhibited dual inhibitory effects, with IC50 values of 4.34 µM against EGFRT790M/C797S/L858R and 1.27 µM against EGFRT790M/L858R. Further investigations into the antiproliferative effects in H1975, A549, H460 and Ba/F3-EGFRL858/T790M/C797S cancer cells revealed that T001-10027877 was the most potent anticancer agent among the tested compounds. Additionally, the induction of H1975 cell apoptosis and cell cycle arrest by T001-10027877 were confirmed, elucidating its mechanism of action. CONCLUSIONS: This study highlights the efficacy of combining computational techniques with bioactivity assessments in the quest for novel antiproliferative agents targeting complex EGFR mutations. In particular, T001-10027877 has great potential for overcoming EGFR-mediated resistance and merits further in vivo exploration. Our findings contribute valuable insights into the development of next-generation anticancer therapies, demonstrating the power of an integrated drug discovery approach.

Discovery of a potent, selective, and orally available EGFR C797S mutant inhibitor (DS06652923) with in vivo antitumor activity.

The C797S mutation is one of the major factors behind resistance to the third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). Herein, we describe the discovery of DS06652923, a novel, potent, and orally available EGFR-triple-mutant inhibitor. Through scaffold hopping from the previously reported nicotinamide derivative, a novel biaryl scaffold was obtained. The potency was successfully enhanced by the introduction of basic substituents based on analysis of the docking study results. In addition, the difluoromethoxy group on the pyrazole ring improved the kinase selectivity by inducing steric clash with the other kinases. The most optimized compound, DS06652923, achieved tumor regression in the Ba/F3 allograft model upon its oral administration.

Novel EGFR inhibitors against resistant L858R/T790M/C797S mutant for intervention of non-small cell lung cancer.

To overcome C797S mutation, the latest and most common resistance mechanism in the clinical treatment of third-generation EGFR inhibitor, a novel series of substituted 6-(2-aminopyrimidine)-indole derivatives were designed and synthesized. Through the structure-activity relationship (SAR) study, compound 11eg was identified as a novel and potent EGFR L858R/T790M/C797S inhibitor (IC50 = 0.053 µM) but had a weak effect on EGFRWT (IC50 = 1.05 µM). 11eg significantly inhibited the proliferation of the non-small cell lung cancer (NSCLC) cells harboring EGFRL858R/T790M/C797S with an IC50 of 0.052 µM. 11eg also showed potent inhibitory activity against other NSCLC cell lines harboring main EGFR mutants. Furthermore, 11eg exhibited much superior activity in arresting cell cycle and inducing apoptosis of NSCLC cells with mutant EGFRC797S. It blocked cellular EGFR signaling. Importantly, 11eg markedly suppressed the tumor growth in in vivo xenograft mouse model with good safety. Additionally, 11eg displayed good microsomal stability. These results demonstrated the potential of 11eg with novel scaffold as a promising lead compound targeting EGFRC797S to guide in-depth structural optimization.

BDTX-189, a novel tyrosine kinase inhibitor, inhibits cell activity via ERK and AKT pathways in the EGFR C797S triple mutant cells.

The tertiary mutation C797S in the structural domain of the EGFR kinase is a common cause of resistance to third-generation EGFR tyrosine kinase inhibitors (TKIs). In this study, we used a potent, selective and irreversible inhibitor, BDTX-189, to target EGFR C797S triple mutant cells for cell activity. The study constructed the H1975-C797S (EGFR L858R/T790 M/C797S) cell line using the CRISPR/Cas9 method and investigated its potential as a fourth-generation tyrosine kinase inhibitor via chemosensitivity approach. The results demonstrated its ability to induce cytotoxic effects, and inhibit EGFR L858R/T790 M/C797S cell growth and proliferation in a dose-dependent manner. Meanwhile, BDTX-189 reduces the protein phosphorylation levels of EGFR, ERK, and AKT, promoting apoptosis. Furthermore, BDTX-189 not only inhibits common EGFR triple mutations but also effectively inhibits EGFR L858R mutation and EGFR L858R/T790 M mutation. These findings support the cytotoxic effect of BDTX-189 and its inhibitory effect on cell division and proliferation with the EGFR C797S triple mutation.

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.

Insights into the Overcoming EGFRDel19/T790M/C797S Mutation: A Perspective on the 2-Aryl-4-aminothienopyrimidine Backbone.

The epithelial growth factor receptor (EGFR) signaling pathway has been proposed to benefit non-small cell lung cancer (NSCLC) treatment. In this manuscript, we investigated the modification of 2-aryl-4-aminoquinazoline, the classical backbone of the fourth-generation EGFR inhibitors, in addition to obtaining a series of novel 2-aryl-4-aminothienopyrimidine derivatives (A1~A45), we also gained further understanding of the modification of this framework. Derivatives were tested for cytotoxicity against cancer cell lines (cervical cancer cell line Hela, lung cancer cell lines A549, H1975, and PC-9, Ba/F3-EGFRDel19/T790M/C797S cells, and human normal hepatocytes LO2) as well as for the derivative's inhibitory activity against EGFRWT, EGFRL858R/T790M, and EGFRDel19/T790M/C797S kinase inhibitory activities. The results showed that most of the target compounds showed moderate to excellent activity against one or more cancer cell lines. Among them, the antitumor activity (IC50) of the most promising A9 against A549 and H1975 cell lines was 0.77±0.08 µM, 6.90±0.83 µM, respectively. At concentration of 10 µM, A9 can be employed as the fourth-generation of EGFR inhibitors with the ability to overcome the C797S drug resistance since it can suppress EGFRDel19/T790M/C797S cells and kinase by 98.90 % and 85.88 %, respectively. Moreover, the tumor-bearing nude mice experiment further shows that A9 can significantly inhibit the growth of tumor in vivo, with the tumor inhibition rate (TIR) of 55.92 %, which was equivalent to the positive group. After that, from the result of HE staining experiment and blood biochemical analysis experiment, A9 show low toxicity and good safety, which is worthy of further research and development.

T6496 targeting EGFR mediated by T790M or C797S mutant: machine learning, virtual screening and bioactivity evaluation study.

Acquired resistance to EGFR is a major impediment in lung cancer treatment, highlighting the urgent need to discover novel compounds to overcome EGFR drug resistance. In this study, we utilized in silico methods and bioactivity evaluation for drug discovery to identify novel active anticancer agents targeting EGFRT790M/L858R and EGFRT790M/C797S/L858R. Firstly, we employed ROC-guided machine learning to retrieve nearly 7,765 compounds from a collection of three libraries (comprising over 220,000 compounds). Next, virtual screening, cluster analysis, and binding model analysis were employed to identify six potential compounds. Additionally, the kinase assay revealed that these six compounds demonstrated higher sensitivity to EGFR than c-Met. Among these compounds, T6496 inhibited both EGFRT790M/L858R and EGFRT790M/C797S/L858R kinases, with an IC50 of 3.30 and 8.72 µM. Furthermore, we evaluated the antitumor effects of the six selected compounds, and compound T6496 exhibited the strongest anticancer activity against H1975 cell lines, with an IC50 value of 2.7 µM. These results suggest that T6496 may mitigate EGFR resistance caused by T790M or C797S mutations. Moreover, the AO staining assay, JC-1 staining, ROS experiment and hemolytic toxicity evaluation revealed that T6496 could induce apoptosis in H1975 cell lines in a time-dependent and concentration-dependent manner, and is a potential compound for further structural optimization.Communicated by Ramaswamy H. Sarma.

ROC guided machine learning, virtual screening and bioevaluation was applied to discover six hit compounds for overcoming EGFR resistance mediated by T790M or C797S.The promising compound T6496 could both inhibit EGFR^T790M/L858R and EGFR^{T790M/C797S/L858R}, with an IC₅₀ of 3.30 and 8.72 µM.In addition, T6496 and AO-365/43489452 show excellent anticancer activity even better than AZD9291.AO staining assay, JC-1 staining, and ROS experiment revealed that compounds T6496 could induce apoptosis in H1975 cell lines in a time-dependent and concentration-dependent manner.

The Impact of On-Target Resistance Mediated by EGFR-T790M or EGFR-C797S on EGFR Exon 20 Insertion Mutation Active Tyrosine Kinase Inhibitors.

Introduction: Mechanisms of resistance to EGFR exon 20 insertion mutation active inhibitors have not been extensively studied in either robust preclinical models or patient-derived rebiopsy specimens. We sought to characterize on-target resistance mutations identified in EGFR exon 20 insertion-mutated lung cancers treated with mobocertinib or poziotinib and evaluate whether these mutations would or would not have cross-resistance to next-generation inhibitors zipalertinib, furmonertinib, and sunvozertinib. Methods: We identified mechanisms of resistance to EGFR exon 20 insertion mutation active inhibitors and then used preclinical models of EGFR exon 20 insertion mutations (A767_V769dupASV, D770_N771insSVD, V773_C774insH) plus common EGFR mutants to probe inhibitors in the absence/presence of EGFR-T790M or EGFR-C797S. Results: Mobocertinib had a favorable therapeutic window in relation to EGFR wild type for EGFR exon 20 insertion mutants, but the addition of EGFR-T790M or EGFR-C797S negated the observed window. Zipalertinib had a favorable therapeutic window for cells driven by EGFR-A767_V769dupASV or EGFR-D770_N771insSVD in the presence or absence of EGFR-T790M. Furmonertinib and sunvozertinib had the most favorable therapeutic windows in the presence or absence of EGFR-T790M in all cells tested. EGFR-C797S in cis to all EGFR mutations evaluated generated dependent cells that were resistant to the covalent EGFR tyrosine kinase inhibitors mobocertinib, zipalertinib, furmonertinib, sunvozertinib, poziotinib, and osimertinib. Conclusions: This report highlights that poziotinib and mobocertinib are susceptible to on-target resistance mediated by EGFR-T790M or -C797S in the background of the most prevalent EGFR exon 20 insertion mutations. Furmonertinib, sunvozertinib, and to a less extent zipalertinib can overcome EGFR-T790M compound mutants, whereas EGFR-C797S leads to covalent inhibitor cross-resistance-robust data that support the limitations of mobocertinib and should further spawn the development of next-generation covalent and reversible EGFR exon 20 insertion mutation active inhibitors with favorable therapeutic windows that are less vulnerable to on-target resistance.

Real-World Genomic Profile of EGFR Second-Site Mutations and Other Osimertinib Resistance Mechanisms and Clinical Landscape of NSCLC Post-Osimertinib.

INTRODUCTION: The emergence of osimertinib as standard of care for EGFR-mutant NSCLC has renewed the need to understand and overcome drug resistance. We sought to understand the genomics and real-world treatment landscape of NSCLC with EGFR C797S and other on- and off-target resistance mechanisms. METHODS: Comprehensive genomic profiling (CGP) results from tissue or blood samples from 93,065 patients with NSCLC were queried for osimertinib EGFR second-site resistance mutations (ssEGFRms; C797, L718, G724, G796, L792). A real-world electronic health record-derived deidentified clinicogenomic database of patients with NSCLC undergoing CGP from approximately 280 U.S. cancer clinics was queried to assess post-osimertinib resistance and clinical treatment outcomes. RESULTS: A ssEGFRm was identified in 239 of 8845 (2.7%) EGFR-driven (L858R or exon 19 deletion) NSCLCs, most frequently C797 (71%), L718 (15%), and G724 (9.5%). ssEGFRms were not equally distributed across drivers; C797 and G724 changes strongly favored exon 19 deletion and L718, G796 and L792 favored L858R. Post-osimertinib CGP detected ssEGFRm in 19% of the cases (39 of 205); in paired pre-/post-osimertinib samples, on- and off-target resistance was largely mutually exclusive and observed in 24% and 27% of the cases, respectively. Of 391 patients with post-osimertinib treatment data, 62% received a chemotherapy-based regimen, whereas 25% received a targeted therapy or clinical study drug. Median real-world overall survival was 11.4 months from osimertinib progression. CONCLUSIONS: The osimertinib resistance landscape is diverse with on-target ssEGFRm and off-target resistance detected in tissue and liquid biopsy. Post-osimertinib, patients are receiving primarily chemotherapy-based regimens with poor outcomes, and CGP at resistance may offer an opportunity to inform therapeutic development and improve treatment selection.

Synthesis, activity, and their relationships of 2,4-diaminonicotinamide derivatives as EGFR inhibitors targeting C797S mutation.

The C797S mutation is one of the major factors behind resistance to the third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. Herein, we describe the discovery of the 2,4-diaminonicotinamide derivative 5j, which shows potent inhibitory activity against EGFR del19/T790M/C797S and L858R/T790M/C797S. We also report the structure-activity relationship of the 2,4-diaminonicotinamide derivatives and the co-crystal structure of 5j and EGFR del19/T790M/C797S.

Allelic Context of EGFR C797X-Mutant Lung Cancer Defines Four Subtypes With Heterogeneous Genomic Landscape and Distinct Clinical Outcomes.

INTRODUCTION: EGFR C797X (C797S or C797G) mutation is the most frequent on-target mechanism of resistance to osimertinib. The hypothesis that the allelic context of C797X/T790M has implications for treatment is on the basis of sporadic reports and needs validation with larger cohorts. METHODS: We identified patients with EGFR C797X-mutant NSCLC from nine centers who progressed on osimertinib, all analyzed in a single laboratory through next-generation sequencing. We analyzed genomic profiles and assessed associations between clinical outcomes and C797X status. RESULTS: A total of 365 EGFR C797X-mutant cases were categorized into four subtypes on the basis of allelic context: in cis (75.3%), in trans (6.4%), cis&trans (10.4%), and C797X-only (7.9%). Genomically, the cis&trans subtype displayed the highest frequency of concurrent alterations at osimertinib resistance sites (21.1%), while the in cis subtype had the lowest (8.4%). Clinically, cis&trans patients exhibited the worst progression-free survival (PFS) on both previous (median 7.7 mo) and subsequent treatment (median 1.0 mo) and overall survival (median 3.9 mo). In subsequent treatments, in cis patients exhibited superior PFS with combined brigatinib and cetuximab (median 11.0 mo) compared with other regimens (p = 0.005), while in trans patients exhibited variable outcomes with combined first or second- and third-generation EGFR inhibitor (PFS range: 0.7-8.1 mo, median 2.6 mo). Notably, subtype switching was observed after subsequent treatments, predominantly toward the in cis subtype. CONCLUSIONS: Allelic context could define four EGFR C797X-mutant NSCLC subtypes with heterogeneous genetic landscapes and distinct clinical outcomes. Subsequent treatments further complicate the scenario through subtype switching.

Novel bioactive 2-phenyl-4-aminopyrimidine derivatives as EGFRDel19/T790M/C797S inhibitors for the treatment of non-small cell lung cancer.

Overexpression of the epidermal growth factor receptor (EGFR) has been implicated in the development of non-small-cell lung cancer (NSCLC). Thus, EGFR is an effective drug target for the treatment of NSCLC, and developing fourth-generation EGFR inhibitors to overcome the resistance mediated by T790M/C797S mutations are currently under investigation. In this study, based on the binding model between Angew2017-7634-1 and EGFRT790M/C797S , several series of 2-phenyl-4-aminopyrimidine derivatives were designed and synthesized. The bioactivity of these compounds was evaluated and it is suggested that compound A23 could effectively inhibit the proliferation of Ba/F3-EGFRDel19/T790M/C797S and H1975-EGFRL858R/T790M cells, with an IC50 of 0.22 ± 0.07 and 0.52 ± 0.03 µM, respectively. Meanwhile, the kinase activity of A23 against EGFRL858R/T790M and EGFRDel19/T790M/C797S was also evaluated, with an IC50 of 0.33 and 0.133 µM, respectively. Moreover, compound A23 was further evaluated in the H1975 xenograft models with significant in vivo tumor growth inhibitions of 25.5%, which means that A23 could effectively inhibit the growth of tumor cells and promote the death of tumor cells. As a result, A23 could be identified as a novel potential EGFRDel19/T790M/C797S inhibitor.

Modification of osimertinib to discover new potent EGFRC797S-TK inhibitors.

The EGFRC797S mutation is a dominant mechanism of acquired resistance after the treatment of non-small cell lung cancer (NSCLC) with osimertinib in clinic. To date, there is no inhibitor approved to overcome the resistance caused by osimertinib. In this study, a series of compounds with phenylamino-pyrimidine scaffold deriving from osimertinib were designed, synthesized and evaluated as fourth-generation EGFRC797S-TK inhibitors. Consequently, compound Os30 exhibited potent inhibitory activities against both EGFRDel19/T790M/C797S TK and EGFRL858R/T790M/C797S TK with IC50 values of 18 nM and 113 nM, respectively. Moreover, Os30 can powerfully inhibit the proliferation of KC-0116 (BaF3-EGFRDel19/T790M/C797S) and KC-0122 (BaF3-EGFRL858R/T790M/C797S) cells. In addition, Os30 can suppress EGFR phosphorylation in a concentration-dependent manner in KC-0116 cells, arrest KC-0116 cells at G1 phase and induce the apoptosis of KC-0116 cells. More importantly, Os30 showed potent antitumor efficacy in the KC-0116 cells xenograft nude mice tumor model with the tumor growth inhibitory rate of 77.6% at a dosage of 40 mg/kg. These findings demonstrate that modification of osimertinib can discover new potent EGFRC797S-TK inhibitors, and compound Os30 is a potent fourth-generation EGFR inhibitor to treat NSCLC with EGFmRC797S mutation.

Design and synthesis of 4th generation EGFR inhibitors against human triple (Del19/T790M/C797S) mutation.

Epidermal growth factor receptor (EGFR)-targeted therapy is used to treat EGFR mutation-induced non-small cell lung cancer (NSCLC). However, its efficacy does not last beyond a certain period due to the development of primary and secondary resistance. First and second-generation inhibitors (e.g., gefitinib, erlotinib, and afatinib) induce EGFR T790M mutations, while third-generation inhibitors (e.g., osimertinib) induce C797S as a major target resistance mutation. Therefore, the C797S mutation is being actively researched. In this study, we investigated the structure-activity relationship of several synthesized compounds as fourth-generation inhibitors against the C797S mutation. We identified a compound 13k that displayed nanomolar potency and high selectivity. Moreover, we used a triple mutant xenograft mouse model to evaluate the in vivo efficacy of 13k in inhibiting EGFR C797S, which demonstrated exceptional profiles and satisfactory EGFR C797S inhibition efficacy. Based on its excellent in vitro and in vivo profiles, compound 13k can be considered a promising candidate for treating EGFR C797S mutations.

Design, synthesis and evaluation of new pyrimidine derivatives as EGFRC797S tyrosine kinase inhibitors.

The clinical use of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in the treatment of non-small cell lung cancer was limited by the drug resistance caused by EGFRC797S mutation. Therefore, in order to overcome the drug resistance, we designed and synthesized a series of 2-aminopyrimidine derivatives as EGFRC797S-TKIs. Among these compounds, compounds A5 and A13 showed significant anti-proliferative activity against the KC-0116 (EGFRdel19/T790M/C797S) cell line with high selectivity. A5 inhibited EGFR phosphorylation and induced apoptosis of KC-0116 cell, arrested KC-0116 cell at G2/M phase. Molecular docking results showed that A5 and brigatinib bind to EGFR in a similar pattern. In addition to forming two important hydrogen bonds with Met793 residue, A5 also formed a hydrogen bond with Lys745 residues, which may play an important role for the potent inhibitory activity against EGFRdel19/T790M/C797S. Based on these results, A5 turned out to be effective reversible EGFRC797S-TKIs which can be further developed.

Alternating Therapy With Osimertinib and Afatinib Blockades EGFR Secondary Mutation in EGFR-Mutant Lung Cancer: A Single-Arm Phase II Trial.

BACKGROUND: Resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) has limited treatment options for patients with EGFR-mutated non-small-cell lung cancer (NSCLC). Although osimertinib or afatinib alone induced drug-resistant clones with EGFR secondary mutation in a preclinical model, its combination prevented the appearance of these mutations. We investigated alternating-dose therapy of osimertinib and afatinib in patients with EGFR-mutant NSCLC in a single-arm Phase II trial. METHODS: Treatment-naïve patients with stage IV NSCLC harboring an activating EGFR mutation were enrolled. Alternating cycles of osimertinib (80 mg/day) followed by afatinib (20 mg/day) were administered every 8 weeks. Genomic analysis was performed using circulating tumor DNA obtained before and after the treatment. RESULTS: Among the 46 enrolled patients, the median progression-free survival was 20.2 months. The overall response rate was 69.6%. The median overall survival was not reached. Among the 26 plasma samples obtained after the acquisition of resistance, 3 showed an increased MET gene copy number, and 1 showed BRAF mutation. Meanwhile, no EGFR secondary mutation was detected. CONCLUSION: The efficacy of our treatment was not significantly different from osimertinib alone, as reported previously in untreated advanced NSCLC patients with EGFR mutations. Although the sample size was limited, this treatment may prevent the emergence of EGFR secondary mutations that trigger drug resistance. Further studies are warranted to establish the significance of this treatment. CLINICAL TRIAL REGISTRATION: jRCTs051180009.

The EGFR C797S Mutation Confers Resistance to a Novel EGFR Inhibitor CLN-081 to EGFR Exon 20 Insertion Mutations.

Introduction: EGFR exon 20 insertion mutations account for 5% to 10% of EGFR-mutated NSCLC. CLN-081 (formerly known as TAS6417), a novel covalent EGFR tyrosine kinase inhibitor, exhibits pan-mutation selective efficacy, including exon 20 insertions, in the clinical setting. Nevertheless, some patients may not respond to CLN-081 and resistance to CLN-081 may emerge over time in others. Methods: We exposed Ba/F3 cells transduced with EGFR exon 20 insertions (Y764_V765 insHH or A767_S768insSVD) to increasing concentrations of CLN-081 to generate resistant cells and then subjected their complementary DNA to sequencing to identify acquired mutations. We then evaluated effects of small molecules on engineered Ba/F3 cells on the basis of proliferation assays, Western blotting, and xenograft models. Results: All CLN-081 resistant clones harbored the EGFR C797S mutation. Ba/F3 cells with C797S (Ba/F3-C797S) were resistant to EGFR tyrosine kinase inhibitors targeting EGFR exon 20 insertion mutations, including CLN-081. Pimitespib, a selective heat shock protein 90 inhibitor, induced apoptosis in Ba/F3-C797S cells in vitro and inhibited growth of Ba/F3-C797S tumors in vivo. Ba/F3 cells with A763_Y764insFQEA-C797S remained sensitive to erlotinib. Conclusions: We conclude that the EGFR C797S mutation confers resistance to CLN-081. Our preclinical data suggest a potential small molecule to overcome CLN-081 resistance, which may benefit patients with lung cancer with EGFR exon 20 insertions.

Overcoming Resistance to Osimertinib by T790M Loss and C797S Acquisition Using Gefitinib in a Patient With EGFR-Mutant NSCLC: A Case Report.

Limited strategies are available at disease progression on osimertinib for patients with EGFR-mutant NSCLC. The emergence of the on-target EGFR C797S mutation has been described as one of the most common mechanisms of resistance. In addition, loss of the EGFR T790M mutation has been mainly investigated as a resistance phenomenon to second-line osimertinib exposure. Remarkably, by studying the molecular profile at progression, it has been reported that the presence of the EGFR-sensitizing mutation, concurrently with the T790M, and C797S resulted in resistance to the current available EGFR tyrosine kinase inhibitors. Here, we report the first clinical evidence of gefitinib efficacy at EGFR exon 19 deletion/C797S mutation/T790M loss-mediated resistance to first-line osimertinib. Our findings highlight that dynamic genetic monitoring is a crucial approach in the evolution of EGFR-mutant NSCLC to understand the acquired molecular mechanisms for driving the best treatment strategy.