Efficacy and safety of osimertinib in a Japanese compassionate use program.

Background: Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that targets the T790M mutation of EGFR. In 2016, AstraZeneca conducted a compassionate use program for osimertinib in Japan.

Methods: Eighteen consecutive patients with histologically proven non-small-cell lung cancer (NSCLC) and harboring the T790M EGFR mutation participated in the compassionate use program between 1 April and 25 May 2016, at the National Cancer Center Hospital. We examined the efficacy and safety of osimertinib in a compassionate use program.

Results: All patients had been previously treated with both cytotoxic chemotherapy and EGFR TKIs. Overall response rate was 62.5% (95% confidence interval (CI): 35.9-89.1%). Among the six patients pretreated with a third-generation EGFR TKI, two (33%) responded to osimertinib. On administration with osimertinib, median progression-free and overall survival rates at six months were 66.7% (95% CI: 44.9-88.5) and 88.9% (95% CI: 74.4-100), respectively. Although the toxicity of osimertinib was mild in most patients, three patients had severe adverse events: two developed interstitial lung disease (ILD) and one developed Grade 3 hepatotoxicity. Among these, two (33%) of the six patients who received osimertinib following nivolumab treatment developed severe adverse events, with one each developing Grade 3 hepatotoxicity and Grade 3 ILD. Only one patient visited our hospital seeking to participate in the compassionate program from another hospital.

Conclusion: Osimertinib demonstrated efficacy even in patients with heavily pretreated NSCLC harboring the T790M mutation. Some patients pretreated with another third-generation EGFR TKI also responded to osimertinib.