A comprehensive overview of the heterogeneity of EGFR exon 20 variants in NSCLC and (pre)clinical activity to currently available treatments

Activating EGFR mutations are commonly observed in non-small cell lung cancer (NSCLC). About 4-10 % of all activating epidermal growth factor receptor (EGFR) mutations are heterogenous in-frame deletion and/or insertion mutations clustering within exon 20 (EGFRex20+). NSCLC patients with EGFRex20+ mutations are treated as a single disease entity, irrespective of the type and location of the mutation. Here, we provide a comprehensive assessment of the literature reporting both in vitro and clinical drug sensitivity across different EGFRex20+ mutations. The activating A763_Y764insFQEA mutation has a better tumor response in comparison with mutations in the near- and far regions directly following the C-helix and should therefore be treated differently. For other EGFRex20+ mutations marked differences in treatment responses have been reported indicating the need for a classification beyond the exon-based classification. A further classification can be achieved using a structure-function modeling approach and experimental data using patient-derived cell lines. The detailed overview of TKI responses for each EGFRex20+ mutation can assist treating physicians to select the most optimal drug for individual NSCLC patients.</p

Crizotinib treatment for patients with EGFR mutation positive NSCLC that acquire cMET amplification after EGFR TKI therapy results in short-lived and heterogeneous responses

Purpose: Next to secondary epidermal growth factor receptor (EGFR) mutations, cMET amplification plays an important role in mediating acquired resistance to EGFR tyrosine kinase inhibitors (TKI) treatment. Crizotinib, a dual ALK and cMET inhibitor, can induce responses in patients with EGFR mutation positive non-small cell lung cancer (NSCLC) that acquire cMET amplification after EGFR TKI treatment. However, little is known about the duration of response and post-progression resistance mechanisms. Here, we report on the clinical outcome of a series of patients with cMET-driven resistance to EGFR TKIs, treated with crizotinib. Materials and methods: Eight patients with EGFR mutation positive NSCLC that acquired cMET amplification after EGFR TKI treatment were treated with crizotinib 250 mg twice daily, as monotherapy (n = 2) or in combination with an EGFR TKI (n = 6). Results: Four out of eight patients (50%) showed a partial response (PR) according to RECIST 1.1. Median progression-free survival (PFS) was 1.4 (95% CI 1.2–5.0) months. Responses were short-lasting with a median PFS of 3.5 (95% CI 1.4–5.2) months in patients with a PR. Median overall survival was 5.9 (95% CI 1.3–6.0) months and not statistically different between responders and non-responders (p = 0.37). All but one patient tolerated crizotinib treatment well. Heterogeneous responses were seen in patients with progressive disease as best response with a marked size decrease of the biopsied (cMET amplification positive) lesion and progression of other lesions. cMET amplification was not always mutually exclusive with other EGFR TKI resistance mechanisms. Post-progression biopsies were negative for cMET amplification. Conclusion: Crizotinib treatment for patients with EGFR mutation positive NSCLC that acquire cMET amplification after EGFR TKI treatment results in short-lived and often heterogeneous responses, possibly due to subclonality of cMET-driven resistance and co-occurrence of other EGFR TKI resistance mechanisms

Exposure–Response Analysis of Osimertinib in EGFR Mutation Positive Non-Small Cell Lung Cancer Patients in a Real-Life Setting

Background: Osimertinib, an irreversible inhibitor of the epidermal growth factor receptor (EGFR) is an important drug in the treatment of EGFR-mutation positive non-small cell lung cancer (NSCLC). Clinical trials with osimertinib could not demonstrate an exposure-efficacy relationship, while a relationship between exposure and toxicity has been found. In this study, we report the exposure–response relationships of osimertinib in a real-life setting. Methods: A retrospective observational cohort study was performed, including patients receiving 40 - 80 mg osimertinib as ≥ 2 line therapy and from whom pharmacokinetic samples were collected during routine care. Trough plasma concentrations (C min,pred) were estimated and used as a measure of osimertinib exposure. A previously defined exploratory pharmacokinetic threshold of 166 µg/L was taken to explore the exposure-efficacy relationship. Results: A total of 145 patients and 513 osimertinib plasma concentration samples were included. Median progression free survival (PFS) was 13.3 (95% confidence interval (CI):10.3 – 19.1) months and 9.3 (95% CI: 7.2 – 11.1) months for patients with C min,pred < 166 µg/L and C min,pred ≥ 166 µg/L, respectively (p = 0.03). In the multivariate analysis, a C min,pred < 166 µg/L resulted in a non-statistically significant hazard ratio of 1.10 (95% CI: 0.60 – 2.01; p = 77). Presence of a EGFR driver-mutation other than the exon 19 del or L858R mutations, led to a shorter PFS with a hazard ratio of 2.89 (95% CI: 1.18 – 7.08; p = 0.02). No relationship between exposure and toxicity was observed (p = 0.91). Conclusion: In our real-life cohort, no exposure–response relationship was observed for osimertinib in the current dosing scheme. The feasibility of a standard lower fixed dosing of osimertinib in clinical practice should be studied prospectively