Safety and Antitumor Activity of Farletuzumab Ecteribulin in Patients With NSCLC: Phase I Expansion Results

Introduction: Farletuzumab ecteribulin (FZEC), an antibody-drug conjugate targeting folate receptor-alpha (FRα), was well tolerated with preliminary antitumor activity in the dose-escalation part of Study 101. We explored the safety and antitumor activity of FZEC in patients with NSCLC from the Study 101 expansion part. Methods: Eligible patients aged above or equal to 20 years with advanced NSCLC adenocarcinoma after previous treatment or no available alternate standard therapy received FZEC 0.9 mg/kg intravenously every 3 weeks. Safety, objective response rate (ORR), duration of response, progression-free survival, and overall survival were assessed. Adverse event (AE) severity was graded per the Common Terminology Criteria for Adverse Events version 4.03. Tumor response was assessed by investigators per Response Evaluation Criteria in Solid Tumors version 1.1. Results: A total of 15 patients were enrolled (July-November 2020). Median age was 68.0 years, and 53.3% had an Eastern Cooperative Oncology Group performance status of 0. Furthermore, 73.3% (n = 11) had FRα expression in more than or equal to 5% of neoplastic cells (FRα positive); 46.7% had FRα expression in more than or equal to 75% of neoplastic cells. All patients received more than or equal to two previous anticancer regimens. The most common treatment-emergent AEs were alanine aminotransferase increased, aspartate aminotransferase increased, interstitial lung disease/pneumonitis, and pyrexia. Two patients experienced a grade more than or equal to 3 treatment-emergent AE. One patient discontinued study treatment because of interstitial lung disease/pneumonitis. One patient had a partial response (duration: 2.3 mo), for an ORR of 6.7%. The disease control rate was 53.3%, median progression-free survival was 2.7 months, and median overall survival was not estimable. ORR among FRα-positive patients was 9.1%. Conclusions: FZEC demonstrated modest antitumor activity, and observed AEs were generally manageable in patients with heavily pretreated NSCLC. Clinical Trial registration: NCT03386942.