A phase 1, dose escalation study of oral ASP8273 in patients with non-small cell lung cancers with epidermal growth factor receptor mutations

PURPOSE: Acquired EGFR T790M mutations are the most frequently identified resistance mechanism to EGFR tyrosine kinase inhibitors (TKIs) in patients with EGFR-mutant lung cancers. ASP8273 is a third-generation EGFR TKI with antitumor activity in preclinical models of EGFR-mutant lung cancer that targets mutant EGFR, including EGFR T790M. EXPERIMENTAL DESIGN: In this multi-cohort, phase 1 study (NCT02113813), escalating doses of ASP8273 (25-500mg) were administered once daily to non-small cell lung cancer (NSCLC) patients with disease progression after prior treatment with an EGFR TKI. EGFR T790M was required for all cohorts, except the dose-escalation cohort. Primary endpoints were safety/tolerability; secondary endpoints were determination of the RP2D, pharmacokinetic profile, and preliminary antitumor activity of ASP8273. Evaluation of the use of EGFR mutations in circulating-free DNA (cfDNA) as a biomarker of ASP8273 treatment effects was an exploratory endpoint. RESULTS: A total of 110 patients were treated with ASP8273 across dose-escalation (n=36), response-expansion (n=36), RP2D (300mg; n=19) and food-effect (n=19) cohorts. The most common treatment-emergent adverse events included diarrhea, nausea, fatigue, constipation, vomiting, and hyponatremia. Across all doses, in patients with EGFR T790M, the response rate was 30.7% (n=27/88, 95% CI 19.5-44.5%), and median progression-free survival was 6.8 months (95% CI 5.5-10.1 months). EGFR mutations in cfDNA, both the activating mutation and EGFR T790M, became undetectable in most patients in the setting of clinical response and reemerged upon disease progression. CONCLUSIONS: ASP8273 was well-tolerated and promoted antitumor activity in patients with EGFR-mutant lung cancer with disease progression on prior EGFR TKI therapy.

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