LAUSR

9066 Background: Taletrectinib (AB-106; DS-6051b) is a potent, selective ROS1/NTRK inhibitor. In two phase I trials, NSCLC patients (pts) with ROS1 fusion who received taletrectinib as first line ROS1 TKI had an objective response rate (ORR) of 66.7% (6/9) and median progression-free survival (PFS) of 29.1 mo (Sai-Hong Ignatius Ou et al., JTO Clinical and Research Reports, 2020). TRUST (NCT04395677) is an ongoing, multicenter, phase II study of taletrectinib in Chinese NSCLC pts with ROS1 fusion. Methods: The ROS1 TKI naïve or crizotinib pre-treated NSCLC patients with ROS1 fusion were treated with taletrectinib 400 or 600 mg QD. ROS1 testing was performed in each center and confirmed by central lab using RT-PCR. The primary endpoint was ORR (complete response [CR] + partial response [PR]) by IRC assessment. Secondary endpoints were disease control rate (DCR; CR + PR + stable disease), PFS and safety, etc. The pharmacokinetics (PK) of taletrectinib following 400 or 600 mg QD regimen was also evaluated. Results: As of the data cutoff (15 Jan 2021), 22 pts had received taletrectinib treatment. Median age was 54.5 years (range, 32-77 years;); 18.2% (4/22) had central nervous system metastases; ECOG performance status was 0 in 13.6% (3/22) of pts and 1 in 86.4% (19/22) of pts. Most pts (54.5%, 12/22) had prior systematic chemotherapy; 31.8% (7/22) of pts had prior crizotinib treatment. ORR by investigator among the crizotinib naïve pts with tumor assessment (N = 11) was 100% (95% CI, 72%-100%); 81.8% (18/22) of pts had treatment-emergent adverse events (TEAEs), including nausea, vomiting, diarrhea, transaminase elevation, white blood cell count decrease/neutrophil count decrease, etc. 13.6% (3/22) were grade ≥ 3, including fatigue (4.5%, 1/22), white blood cell decrease (4.5%, 1/22) and transaminase elevation (4.5%, 1/22).TEAEs led to dose interruption in 3 pts (13.6%), including dose reduction in 2 pts (9.1%). Taletrectinib in plasma approximately reached steady state on Cycle 1 Day 8 with 2- to 3- fold accumulations of exposure, which was consistent with results observed in the phase I trials. Conclusions: Taletrectinib demonstrated promising clinical activity with high ORR and good tolerability in ROS1 fusion positive NSCLC patients. The safety and PK profiles following taletrectinib treatment was generally consistent with the phase I trials. Clinical trial information: NCT04395677. Clinical trial information: NCT04395677.