Abstract 2997: Longitudinal circulating tumor DNA (ctDNA) analysis predicts response and reveals the resistance mechanisms of ensartinib in ALK+ NSCLC patients (pts) progressed on crizotinib: Updated analysis of a phase II clinical trial
Authors: Yang Yunpeng , Huang Jie , Wang Tao , Zhou Jianya , Zheng Jing , Feng Jifeng , Zhuang Wu , Chen Jianhua , Zhao Jun , Zhong Wei , Zhao Yanqiu , Zhang Yiping , Song Yong , Hu Yi , Yu Zhuang , Gong Youling , Chen Yuan , Ye Feng , Zhang Shucai , Cao Lejie , Fan Yun , Wu Gang , Guo Yubiao , Zhou Chengzhi , Ma Kewei , Fang Jian , Feng Weineng , Liu Yunpeng , Zheng Zhendong , Li Gaofeng , Wu Ning , Song Wei , Liu Xiaoqing , Zhao Shijun , Ding Lieming , Mao Li , Selvaggi Giovanni , Zhu Larry , Xiao Shanshan , Zhang Li 
Published: September 2020

Abstract
Introduction: In the previous phase II clinical trial (NCT03215693), ensartinib, a next generation (NG) ALK TKI, showed comparable efficacy to other NG ALK TKIs in the post-crizotinib setting. In the preplanned biomarker analysis, we investigated the efficacy and the resistance mechanisms of ensartinib via longitudinal ctDNA analysis.
Methods: Pts with stage IIIB/IV ALK+ NSCLC, and had progressive disease (PD) after crizotinib were eligible. Plasma samples from this trial were prospectively collected for ctDNA analysis at baseline (BL), cycle 3 day 1 (C3D1) and the end of treatment (EOT). Plasma DNA was analyzed using a 212-gene sequencing panel. ctDNA amount was defined as the sum of variant allele fraction (VAF) of ALK fusions and mutations. Cox model was applied for multivariate analysis.
Results: Between 9/2017 and 7/2019, 182 pts were enrolled in the trial. In total, 178 were included in the full analysis set (FAS), with a median PFS (mPFS) of 9.8 months (95% CI, 7.5 to 11.7 months). 169 pts were evaluable by independent review committee (IRC), with an ORR of 57.7% (95% CI, 50.2% to 65.3%). A total of 431 ctDNA samples were analyzed, including 168 at BL, 165 at C3D1, and 106 at EOT (8 overlappings between C3D1 and EOT). 168 (99.4%) pts had evaluable ctDNA at BL. The median ctDNA amount was 0.00704. The higher ctDNA amount was associated with liver metastases, bone metastases, and TP53 mutations. Tumor burden, as measured by the sum of the target lesions' longest diameters, also positively correlated with ctDNA amount (Pearson correlation 0.261; p &lt; 0.001). Multivariable Cox regression revealed that high level of ctDNA amount and TP53 mutations at BL was significantly associated with poor PFS independently (p =0.020 and p &lt; 0.001) (Table). 106 (62.7%) pts had evaluable ctDNA at both BL and EOT. Compared to baseline, the frequency of certain ALK mutations significantly increased at EOT, such as G1269A (7.5% vs 21.7%), G1202R (3.8% vs 17.0%) and E1210K (0% vs 10.4%).
TP53 statusctDNA amountTP53 Wildtype TP53 Mutations Low amountHigh amount(n = 34)(n = 134)(n = 46)(n = 47)mPFS, months (95% CI) 11.7 (9.8, 14.0) 4.2 (3.0, 5.6)9.3 (5.6, 11.7) 4.2 (2.8, 5.5)HR (95% CI); p value2.50 (1.65, 3.79) ; p &lt; 0.0012.34 (1.52, 3.61) ; p &lt; 0.001
Consistent with the change in frequency, the abundance of G1269A, G1202R, and E1210K also trended to increase at EOT, while the abundance of C1156Y and I1171X had a downward trend in most pts.
Conclusions: Consistent with previous reports, ensartinib showed high clinical efficacy. Longitudinal ctDNA analysis could be a powerful tool in predicting treatment outcomes and revealing resistant mechanisms of ensartinib. We observed G1269A, G1202R and E1210K as the major resistant mutations to ensartinib. Additional analyses are ongoing and results will be updated and reported in the meeting.
Citation Format: Yunpeng Yang, Jie Huang, Tao Wang, Jianya Zhou, Jing Zheng, Jifeng Feng, Wu Zhuang, Jianhua Chen, Jun Zhao, Wei Zhong, Yanqiu Zhao, Yiping Zhang, Yong Song, Yi Hu, Zhuang Yu, Youling Gong, Yuan Chen, Feng Ye, Shucai Zhang, Lejie Cao, Yun Fan, Gang Wu, Yubiao Guo, Chengzhi Zhou, Kewei Ma, Jian Fang, Weineng Feng, Yunpeng Liu, Zhendong Zheng, Gaofeng Li, Ning Wu, Wei Song, Xiaoqing Liu, Shijun Zhao, Lieming Ding, Li Mao, Giovanni Selvaggi, Larry Zhu, Shanshan Xiao, Li Zhang. Longitudinal circulating tumor DNA (ctDNA) analysis predicts response and reveals the resistance mechanisms of ensartinib in ALK+ NSCLC patients (pts) progressed on crizotinib: Updated analysis of a phase II clinical trial [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2997.