Efficacy of Taletrectinib (AB-106/DS-6051b) in ROS1+ NSCLC: An Updated Pooled Analysis of U.S. and Japan Phase 1 Studies

INTRODUCTION: Taletrectinib (AB-106/DS-6051b) is an oral, potent selective ROS1 and pan-NTRK tyrosine kinase inhibitor (TKI). Preclinically, taletrectinib has activity against ROS1 G2032R solvent-front mutation. METHODS: Patients with ROS1+ NSCLC enrolled into two phase 1 studies conducted in United States (U101, NCT02279433) and Japan (J102, NCT02675491) were analyzed for objective response rate (ORR) by the Response Evaluation Criteria in Solid Tumors version 1.1, progression-free survival, and safety. RESULTS: A total of 22 patients with ROS1+ NSCLC out of the total 61 patients enrolled were analyzed. Taletrectinib was given at the oral dose of 400 mg, 600 mg, 800 mg, and 1200 mg once daily and 400 mg twice daily as part of the dose-escalation schema. Data cutoff was August 19, 2020. Median follow-up time for all 22 patients was 14.9 months (95% confidence interval [CI]: 4.1–33.8). A total of 18 patients with ROS1+ were assessable for response. The confirmed ORR for ROS1 TKI-naive patients (N = 9) was 66.7% (95% CI: 35.4–87.9) with a disease control rate of 100% (70.1–100). The confirmed ORR for crizotinib pretreated patients (N = 6) was 33.3% (95% CI: 9.7–70.0) with a disease control rate of 88.3% (95% CI: 443.6–97.0). The median progression-free survival for ROS1 TKI-naive patients (N = 11) was 29.1 months (95% CI: 2.6–not reached) and 14.2 months (95% CI: 1.5–not reached) for crizotinib-refractory only patients (N = 8). The most common treatment-related adverse events were alanine transaminase elevations (72.7%), aspartate transaminase elevations (72.7%), nausea (50.0%), and diarrhea (50.0%). Grade 3 or higher adverse events were alanine transaminase elevations (18.2%), aspartate transaminase (9.1%), and diarrhea (4.5%). CONCLUSIONS: Taletrectinib (AB106/DS6051b) has a meaningful clinical activity in patients with advanced ROS1+ NSCLC who are ROS1 TKI-naive or crizotinib-refractory and a manageable safety profile.