Abstract 4076: Finding the optimal strategy of incorporating immune checkpoint inhibitor inALK-positive non-small-cell lung cancer usingEML4-ALKtransgenic mouse model
Authors: Pyo Kyoung-Ho , Lim Sun Min , Jo Ha Ni , Cho Jae Seok , Kim Jae Hwan , Lee Ji Min , Xin Chun-Feng , Kim Sung Eun , Park Chae Won , Lee Wongeun , Kim Hye Ryun , Cho Byoung Chul 
Published: August 2019

Abstract
Introduction: EML4-ALK is a distinct molecular entity that is highly sensitive to ALK tyrosine kinase inhibitors (TKIs). Although the role of oncogenic and native ALK in modulating the immune responses has been suggested, immune checkpoint inhibitors (ICIs) have not proved efficacy in ALK-positive non-small cell lung cancer (NSCLC) so far. In this study, we evaluated comprehensive immunomodulatory effect of ALK TKI and aimed to suggest optimal method of incorporating ICIs in ALK-positive NSCLC using an EML4-ALK transgenic mice model.
Methods: Ceritinib or anti-PD-1 was treated in EML4-ALK transgenic mice, and tumor response was evaluated using magnetic resonance imaging. Progression-free survival (PFS) and overall-survival (OS) were measured to compare the efficacy in mice. To examine the dynamics of immune response, flow cytometry of tumor region, cytokine-ELISA of bronchoalveolar lavage (BAL) fluid were performed at baseline and at the time of disease progression. Sequencing of ALK kinase domain was performed to identify acquired ALK mutations.
Results: Upfront ceritinib was clearly more efficacious than anti-PD-1 upfront, as shown by the median PFS was 139 days vs.13 days (P &lt; 0.05). Use of ceritinib in the first line resulted in a prolonged OS compared to the use in the second line (OS 203 days vs. 135 days, P&lt; 0.05). The efficacy of ceritinib and anti-PD-1 combination was not more effective than ceritinib alone in the first line. Of note, we identified 1 mouse which showed a complete response to anti-PD-1 after progression on 1st line ceritinib. Tumors which progressed on ceritinib showed increased proportion of CD8+ tumor infiltrating T cells among total CD3+ T cells, and increased expression of IFN-γ in BAL fluid, representing Th1-dominant immune phenotype. In tumors which acquired resistance to ceritinib, we identified known ALK kinase domain mutations such as G1202R with a concomitant increased tumor mutational burden compared to ceritinib-naïve tumors. Ceritinib-resistant tumors also had significantly increased memory cytotoxic T cells and PD-1-expressing helper T cells in total CD3+ population. On the contrary, we noted decreased expressions of central memory T cells, effector memory T cells, IFN-γ in tumors which progressed after ceritinib and anti-PD-1 combination therapy.
Conclusion: Our study confirmed that combination of ALK inhibitor and ICI is not efficacious, as evidenced by low infiltrating T cells and memory T cells. We concluded that tumor progressing on ceritinib could be sensitive to anti-PD-1 due to increased neoantigens derived from acquired ALK mutations, increased tumor mutational burden and increased number of memory T cells and PD-1-expressing helper T cells.
Citation Format: Kyoung-Ho Pyo, Sun Min Lim, Ha Ni Jo, Jae Seok Cho, Jae Hwan Kim, Ji Min Lee, Chun-Feng Xin, Sung Eun Kim, Chae Won Park, Wongeun Lee, Hye Ryun Kim, Byoung Chul Cho. Finding the optimal strategy of incorporating immune checkpoint inhibitor inALK-positive non-small-cell lung cancer usingEML4-ALKtransgenic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4076.