Phase 1 study of DS-1205c combined with gefitinib for EGFR mutation-positive non-small cell lung cancer

Background: Tyrosine kinase inhibitors (TKIs) are effective for the treatment of non-small cell lung cancer (NSCLC) patients with activating mutations of the epidermal growth factor receptor (EGFR), but responses are not durable as tumors develop resistance. DS-1205c is a novel, specific, orally bioavailable, small-molecule AXL receptor TKI. In preclinical studies, DS-1205c restored TKI antitumor activity in a TKI acquired-resistance EGFR-mutant NSCLC tumor xenograft model.

Methods: This first-in-human, multicenter, open-label Phase 1 study (registered at ClinicalTrials.gov: NCT03599518) primarily evaluated the safety and tolerability of combination therapy with DS-1205c and gefitinib in Japanese patients with metastatic or unresectable EGFR-mutant NSCLC and tumor progression during treatment with EGFR-TKIs. Patients (n = 20) received DS-1205c monotherapy (200-1200 mg twice daily [BID]) in a 7-day safety monitoring period before combination DS-1205c/gefitinib (250 mg once daily) in 21-day cycles.

Results: The observed common treatment-emergent adverse events (TEAEs) were increased aspartate aminotransferase (35%), increased alanine aminotransferase (30%), rash maculo-papular (30%), and diarrhea (25%). No serious TEAEs were reported. Plasma concentrations and pharmacokinetic parameters of DS-1205a (free form of DS-1205c) were unaffected by concomitant administration of gefitinib. No patient achieved a complete or partial response and 5 patients (25%) had stable disease.

Conclusion: DS-1205c was generally safe and well tolerated at all dose levels, but the safety profile of ≤800 mg BID was more favorable than 1200 mg BID. The recommended dose for dose-expansion cohorts of DS-1205c in combination therapy with gefitinib was 800 mg BID.