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Osimertinib is a potent, third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). The multi-arm phase Ib TATTON study (NCT02143466) was designed to assess the safety and tolerability of osimertinib in combination with other targeted therapies: selumetinib (MEK1/2 inhibitor), savolitinib (MET-TKI), or durvalumab [anti-programmed cell death ligand 1 (anti-PD-L1) monoclonal antibody]. Patients with advanced EGFR -mutant non-small-cell lung cancer and disease progression on a prior EGFR-TKI were enrolled and allocated to dose-escalating cohorts combining osimertinib 80 mg orally (p.o.) once a day with selumetinib (25–75 mg p.o. twice a day; continuous or intermittent), savolitinib (600–800 mg p.o. once a day), or durvalumab (3–10 mg/kg intravenous every 2 weeks). At data cut-off (28 February 2018), 77 patients were enrolled and received osimertinib plus selumetinib (n = 36), savolitinib (n = 18), or durvalumab (n = 23). Most common adverse events (any grade), occurring in ≥20% of patients across dose groups, were: selumetinib arm—diarrhea (75%), rash (58%), nausea (47%); savolitinib arm—nausea (67%), rash (56%), vomiting (50%); durvalumab arm—rash (48%), vomiting (43%), diarrhea (39%). Dose-limiting toxicities were reported in the selumetinib 25 mg (n = 1), 50 mg (n = 1), and 75 mg (n = 4) continuous-dose groups, savolitinib 600 mg (n = 1) and 800 mg dose groups (n = 2), and durvalumab 10 mg/kg (n = 1) dose group. The objective response rate was 42% (95% confidence interval 26% to 59%), 44% (22% to 69%), and 43% (23% to 66%) in the selumetinib, savolitinib, and durvalumab arms, respectively. Our results demonstrate the feasibility of combining osimertinib 80 mg with selumetinib or savolitinib at identified tolerable, active doses. A combination of osimertinib with durvalumab was not feasible due to increased reporting of interstitial lung disease. Osimertinib-based combination therapies represent a compelling approach now being further investigated. NCT02143466. • Patients with advanced EGFR -mutant NSCLC received osimertinib 80 mg combined with selumetinib, savolitinib or durvalumab. • Feasible dosing strategies were identified for osimertinib plus selumetinib or savolitinib. • Osimertinib plus durvalumab was not feasible due to increased reporting of interstitial lung disease. • Responses were seen in all treatment arms, warranting further analysis of the feasible combinations identified. • Osimertinib-based combinations represent a compelling approach now being investigated broadly to further improve outcomes. [ABSTRACT FROM AUTHOR]

Human epidermal growth factor receptor 3 (HER3) is broadly expressed in non-small-cell lung cancer (NSCLC) and is the target of patritumab deruxtecan (HER3-DXd), an antibody–drug conjugate consisting of a HER3 antibody attached to a topoisomerase I inhibitor payload via a tetrapeptide-based cleavable linker. U31402-A-U102 is an ongoing phase I study of HER3-DXd in patients with advanced NSCLC. Patients with epidermal growth factor receptor (EGFR)-mutated NSCLC that progressed after EGFR tyrosine kinase inhibitor (TKI) and platinum-based chemotherapy (PBC) who received HER3-DXd 5.6 mg/kg intravenously once every 3 weeks had a confirmed objective response rate (cORR) of 39%. We present median overall survival (OS) with extended follow-up in a larger population of patients with EGFR -mutated NSCLC and an exploratory analysis in those with acquired genomic alterations potentially associated with resistance to HER3-DXd. Safety was assessed in patients with EGFR -mutated NSCLC previously treated with EGFR TKI who received HER3-DXd 5.6 mg/kg; efficacy was assessed in those who also had prior PBC. In the safety population (N = 102), median treatment duration was 5.5 (range 0.7-27.5) months. Grade ≥3 adverse events occurred in 76.5% of patients; the overall safety profile was consistent with previous reports. In 78/102 patients who had prior third-generation EGFR TKI and PBC, cORR by blinded independent central review (as per RECIST v1.1) was 41.0% [95% confidence interval (CI) 30.0% to 52.7%], median progression-free survival was 6.4 (95% CI 4.4-10.8) months, and median OS was 16.2 (95% CI 11.2-21.9) months. Patients had diverse mechanisms of EGFR TKI resistance at baseline. At tumor progression, acquired mutations in ERBB3 and TOP1 that might confer resistance to HER3-DXd were identified. In patients with EGFR -mutated NSCLC after EGFR TKI and PBC, HER3-DXd treatment was associated with a clinically meaningful OS. The tumor biomarker characterization comprised the first description of potential mechanisms of resistance to HER3-DXd therapy. • The phase I U31402-A-U102 study evaluated HER3-DXd in heavily pretreated patients with EGFR -mutated NSCLC. • Ninety-seven patients previously treated with EGFR TKI and PBC received HER3-DXd 5.6 mg/kg intravenously every 3 weeks. • Responses were seen across the range of HER3 expression and across diverse mechanisms of resistance to EGFR TKI therapy. • Acquired mutations in ERBB3 were characterized. • OS was 15.8 months (95% CI 10.8-21.5 months). [ABSTRACT FROM AUTHOR]