Osimertinib, an Irreversible Next-Generation EGFR Tyrosine Kinase Inhibitor, Exerts Antitumor Activity in Various Preclinical NSCLC Models Harboring the Uncommon EGFR Mutations G719X or L861Q or S768I.

Osimertinib is an oral, third-generation, irreversible epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) that selectively inhibits both EGFR-TKI-sensitizing and EGFR T790M-resistance mutations with lower activity against wild-type EGFR and has demonstrated efficacy in non-small cell lung cancer (NSCLC) CNS metastases. The sensitizing mutations, the in-frame deletions in exon 19 and the L858R point mutation in exon 21, represent between 80% and 90% of all EGFR mutations. The remaining 10% to 20% are referred to as uncommon activating mutations and are a diverse group of mutations in exons 18 to 21 within the kinase domain of the EGFR gene. Excluding those found as insertion mutations in exon 20, the uncommon mutations involving codons G719, S768, and L861 are the most prevalent.Although the efficacy of EGFR-TKIs for the common EGFR mutations is well established, much less is known about rare EGFR mutations, such as exon 20 insertions, G719X, L861Q, S768I, as most of the data consist of single case reports or small case series.Using available patient-derived xenografts (PDX) and cell lines derived from two of these PDXs that harbor the G719X mutation, we have evaluated in vitro and in vivo the preclinical activity of osimertinib. We report osimertinib inhibits signaling pathways and cellular growth in G719X-mutant cell lines in vitro and demonstrate sustained tumor growth inhibition of PDX harboring the G719X mutation alone or in combination with L861Q and S768I.Together, these data support clinical testing of osimertinib in patients with uncommon EGFR NSCLC.

Floc'h N ，Lim S ，Bickerton S ，Ahmed A ，Orme J ，Urosevic J ，Martin MJ ，Cross DAE ，Cho BC ，Smith PD ... -  《-》

Sensitivities to various epidermal growth factor receptor-tyrosine kinase inhibitors of uncommon epidermal growth factor receptor mutations L861Q and S768I: What is the optimal epidermal growth factor receptor-tyrosine kinase inhibitor?

Most patients with non-small cell lung cancer (NSCLC) harboring common epidermal growth factor receptor (EGFR) mutations, such as deletions in exon 19 or the L858R mutation in exon 21, respond dramatically to EGFR tyrosine kinase inhibitors (EGFR-TKI), and their sensitivities to various EGFR-TKI have been well characterized. Our previous article showed the in vitro sensitivities of EGFR exon 18 mutations to EGFR-TKI, but little information regarding the sensitivities of other uncommon EGFR mutations is available. First, stable transfectant Ba/F3 cell lines harboring EGFR L858R (Ba/F3-L858R), L861Q (Ba/F3-L861Q) or S768I (Ba/F3-S768I) mutations were created and their drug sensitivities to various EGFR-TKI were examined. Both the Ba/F3-L861Q and Ba/F3-S768I cell lines were less sensitive to erlotinib, compared with the Ba/F3-L858R cell line, but their sensitivities to afatinib were similar to that of the Ba/F3-L858R cell line. The Ba/F3-L861Q cell line was similarly sensitive and the Ba/F3-S768I cell line was less sensitive to osimertinib, compared with the Ba/F3-L858R cell line. The results of western blot analyses were consistent with these sensitivities. Next, similar experiments were also performed using the KYSE270 (L861Q) and KYSE 450 (S768I) cell lines, and their results were compatible with those of the transfectant Ba/F3 cell lines. Our findings suggest that NSCLC harboring the EGFR L861Q mutation might be sensitive to afatinib or osimertinib and that NSCLC harboring the EGFR S768I mutation might be sensitive to afatinib. Overall, afatinib might be the optimal EGFR-TKI against these uncommon EGFR mutations.

Banno E ，Togashi Y ，Nakamura Y ，Chiba M ，Kobayashi Y ，Hayashi H ，Terashima M ，de Velasco MA ，Sakai K ，Fujita Y ，Mitsudomi T ，Nishio K ... -  《-》

Antitumor Activity of Osimertinib, an Irreversible Mutant-Selective EGFR Tyrosine Kinase Inhibitor, in NSCLC Harboring EGFR Exon 20 Insertions.

EGFR exon 20 insertions (Ex20Ins) account for 4% to 10% of EGFR activating mutations in non-small cell lung cancer (NSCLC). EGFR Ex20Ins tumors are generally unresponsive to first- and second-generation EGFR inhibitors, and current standard of care for NSCLC patients with EGFR Ex20Ins is conventional cytotoxic chemotherapy. Therefore, the development of an EGFR TKI that can more effectively target NSCLC with EGFR Ex20Ins mutations represents a major advance for this patient subset. Osimertinib is a third-generation EGFR TKI approved for the treatment of advanced NSCLC harboring EGFR T790M; however, the activity of osimertinib in EGFR Ex20Ins NSCLC has yet to be fully assessed. Using CRISPR-Cas 9 engineered cell lines carrying the most prevalent Ex20Ins mutations, namely Ex20Ins D770_N771InsSVD (22%) or Ex20Ins V769_D770InsASV (17%), and a series of patient-derived xenografts, we have characterized osimertinib and AZ5104 (a circulating metabolite of osimertinib) activities against NSCLC harboring Ex20Ins. We report that osimertinib and AZ5104 inhibit signaling pathways and cellular growth in Ex20Ins mutant cell lines in vitro and demonstrate sustained tumor growth inhibition of EGFR-mutant tumor xenograft harboring the most prevalent Ex20Ins in vivo The antitumor activity of osimertinib and AZ5104 in NSCLC harboring EGFR Ex20Ins is further described herein using a series of patient-derived xenograft models. Together these data support clinical testing of osimertinib in patients with EGFR Ex20Ins NSCLC. Mol Cancer Ther; 17(5); 885-96. ©2018 AACR.

Floc'h N ，Martin MJ ，Riess JW ，Orme JP ，Staniszewska AD ，Ménard L ，Cuomo ME ，O'Neill DJ ，Ward RA ，Finlay MRV ，McKerrecher D ，Cheng M ，Vang DP ，Burich RA ，Keck JG ，Gandara DR ，Mack PC ，Cross DAE ... -  《-》

TAS-121, A Selective Mutant EGFR Inhibitor, Shows Activity Against Tumors Expressing Various EGFR Mutations Including T790M and Uncommon Mutations G719X.

TAS-121 is a novel orally active selective covalent inhibitor of the mutant EGFR. We performed preclinical characterization of TAS-121 and compared its efficacy and selectivity for common EGFR mutations (Ex19del and L858R), first- and second- generation EGFR-tyrosine kinase inhibitor (EGFR-TKI) resistance mutation (T790M), and uncommon mutations (G719X and L861Q) with those of other EGFR-TKIs. We also commenced investigation of the clinical benefits of TAS-121. The IC50 for intracellular EGFR phosphorylation was determined by using Jump-In GripTite HEK293 cells transiently transfected with EGFR expression vectors. Mouse xenograft models were used to evaluate the antitumor activity of TAS-121. TAS-121 potently inhibited common activating and resistance EGFR mutations to the same extent as another third-generation EGFR-TKI (osimertinib). In addition, TAS-121 showed equivalent inhibitory activity against some uncommon mutations such as G719X and L861Q. Furthermore, TAS-121 demonstrated greater selectivity for mutant EGFRs versus the wild-type EGFR compared with other EGFR-TKIs. Moreover, TAS-121 displayed antitumor activity in SW48 (EGFR G719S) and NCI-H1975 (EGFR L858R/T790M) xenograft models, and achieved an objective response in patients with NSCLC with EGFR mutations including G719A mutation. In conclusion, TAS-121 is a novel third-generation EGFR-TKI and demonstrates antitumor activities in patients with NSCLC expressing either common or uncommon EGFR mutations.

Ito K ，Nishio M ，Kato M ，Murakami H ，Aoyagi Y ，Ohe Y ，Okayama T ，Hashimoto A ，Ohsawa H ，Tanaka G ，Nonoshita K ，Ito S ，Matsuo K ，Miyadera K ... -  《-》

TAS6417/CLN-081 Is a Pan-Mutation-Selective EGFR Tyrosine Kinase Inhibitor with a Broad Spectrum of Preclinical Activity against Clinically Relevant EGFR Mutations.

Despite the worldwide approval of three generations of EGFR tyrosine kinase inhibitors (TKI) for advanced non-small cell lung cancers with EGFR mutations, no TKI with a broad spectrum of activity against all clinically relevant mutations is currently available. In this study, we sought to evaluate a covalent mutation-specific EGFR TKI, TAS6417 (also named CLN-081), with the broadest level of activity against EGFR mutations with a prevalence of ≥1%. Lung cancer and genetically engineered cell lines, as well as murine xenograft models were used to evaluate the efficacy of TAS6417 and other approved/in-development EGFR TKIs (erlotinib, afatinib, osimertinib, and poziotinib). We demonstrate that TAS6417 is a robust inhibitor against the most common EGFR mutations (exon 19 deletions and L858R) and the most potent against cells harboring EGFR-T790M (first/second-generation TKI resistance mutation). In addition, TAS6417 has activity in cells driven by less common EGFR-G719X, L861Q, and S768I mutations. For recalcitrant EGFR exon 20 insertion mutations, selectivity indexes (wild-type EGFR/mutant EGFR ratio of inhibition) favored TAS6417 in comparison with poziotinib and osimertinib, indicating a wider therapeutic window. Taken together, we demonstrate that TAS6417 is a potent EGFR TKI with a broad spectrum of activity and a wider therapeutic window than most approved/in-development generations of EGFR inhibitors. IMPLICATIONS: TAS6417/CLN-081 is a potent EGFR TKI with a wide therapeutic window and may be effective in lung cancer patients with clinically relevant EGFR mutations.

Udagawa H ，Hasako S ，Ohashi A ，Fujioka R ，Hakozaki Y ，Shibuya M ，Abe N ，Komori T ，Haruma T ，Terasaka M ，Fujita R ，Hashimoto A ，Funabashi K ，Yasuda H ，Miyadera K ，Goto K ，Costa DB ，Kobayashi SS ... -  《-》