In the largest series of EGFRex20ins NSCLC, diverse EGFRex20ins were detected in 12% of EGFR-mutant NSCLC, a higher frequency than previously reported in smaller single-institution studies. Clinical outcomes showed lack of response to EGFR TKIs. Tumor mutational burden was low, consistent with non-smoking associated NSCLC. Comprehensive sequencing revealed increased proportion and wide variety of EGFRex20ins, representing a population of patients significant enough for focused efforts on effective interventions.

Background Circulating cell‐free tumor DNA (ctDNA)‐based mutation profiling, if sufficiently sensitive and comprehensive, can efficiently identify genomic targets in advanced lung adenocarcinoma. Therefore, the authors investigated the accuracy and clinical utility of a commercially available digital next‐generation sequencing platform in a large series of patients with non–small cell lung cancer (NSCLC). Methods Plasma‐based comprehensive genomic profiling results from 8388 consecutively tested patients with advanced NSCLC were analyzed. Driver and resistance mutations were examined with regard to their distribution, frequency, co‐occurrence, and mutual exclusivity. Results Somatic alterations were detected in 86% of samples. The median variant allele fraction was 0.43% (range, 0.03%‐97.62%). Activating alterations in actionable oncogenes were identified in 48% of patients, including EGFR (26.4%), MET (6.1%), and BRAF (2.8%) alterations and fusions ( ALK , RET , and ROS1 ) in 2.3%. Treatment‐induced resistance mutations were common in this cohort, including driver‐dependent and driver‐independent alterations. In the subset of patients who had progressive disease during EGFR therapy, 64% had known or putative resistance alterations detected in plasma. Subset analysis revealed that ctDNA increased the identification of driver mutations by 65% over standard‐of‐care, tissue‐based testing at diagnosis. A pooled data analysis on this plasma‐based assay demonstrated that targeted therapy response rates were equivalent to those reported from tissue analysis. Conclusions Comprehensive ctDNA analysis detected the presence of therapeutically targetable driver and resistance mutations at the frequencies and distributions predicted for the study population. These findings add support for comprehensive ctDNA testing in patients who are incompletely tested at the time of diagnosis and as a primary option at the time of progression on targeted therapies.

Activating EGFR mutations detected in shed DNA in plasma are significantly associated with favorable outcomes in patients with advanced NSCLC receiving docetaxel plus intercalated erlotinib. The addition of docetaxel in this schedule did not diminish the efficacy of erlotinib against patients with EGFR activating mutations.

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 and demonstrate sustained tumor growth inhibition of EGFR-mutant tumor xenograft harboring the most prevalent Ex20Ins 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. .

Our results suggest that GCP mediates growth inhibition and apoptosis through multiple mechanisms including (1) molecular mimicry of androgen ablation (via AR downregulation) and (2) by providing an AR-independent, pro-apoptotic signal (mTOR inhibition).