Abstract 4081: Efficacy of MERTK inhibitor in combination with pembrolizumab in lung cancer

Abstract

Abstract Introduction: MERTK is thought to play a role in cancer immune evasion mechanism based on M2 type macrophage-driven immunosuppression in tumor microenvironment (TME). Thus, MERTK is a highly promising target for anti-cancer therapy under high tumor associated macrophages (TAMs) condition. We evaluated the anti-tumor effects and immune reaction of combination or single MERTK inhibitor in two lung squamous patients derived xenograft (PDX) tumor engrafted Hu-CD34-NSG models. Methods: The aPD-1 sensitive (YHIM2004) and aPD-1 non-sensitive (YHIM2009) squamous cell carcinoma PDX models were selected from pre-test with pembrolizumab. The selected two models were composed four groups; control, pembrolizumab, MERTK inhibitor, and combination. We applied pembrolizumab as aPD-1 blockade (10 mpk, q2w, i.p. inj.). The dose of MERTK inhibitor was 50 mpk, q1d by orally. The treatment was started when tumor size reached 100 mm3. Whole exome sequencing (WES), microarray (mRNA), flow cytometry, and multispectral image analysis were performed on the tumors. To elucidate the involvement of MERTK inhibitor in tumor, the tumor mutation burden, tumor microenvironment and immune cell phenotype were deconvoluted. Results: The TMB of YHIM2004 and YHIM2009 was 3.23 and 2.64 (mutations/Mb) respectively. The PD-L1 and TIL level of YHIM2004 were relatively higher than YHIM2009. Both two models were observed high macrophage in tumor. The two PDX-models, YHIM2004 (aPD-1 sensitive), YHIM2009 (aPD-1 non-sensitive) were observed anti-tumor effects in MERTK inhibitor single treatment groups (TGI = 44.23%, 67.40% respectively, p < 0.05, t-test). Especially, YHIM2004 tumor was reduced after combination therapy more than single treatment. Of note, the NOG-PDX model demonstrated no anti-tumor effect in MERTK inhibitor monotherapy, suggesting that this drug involves anti-cancer immune responses. Flow cytometry data showed increased PD-1+ and granzyme B+ T cells (p <0.05, t-test) in the combined group (YHIM2004) and MERTK inhibitor monotherapy group (YHIM2009) as much as the tumor suppressive effect. Conclusion: We concluded that MERTK signaling involves regulation of anti-cancer immune responses. Our results suggest an anti-cancer therapeutics of MERTK selective inhibitor on aPD-1 sensitive or non-sensitive tumors under high TAM tumor microenvironment. Citation Format: Kyoung-Ho Pyo, Ha-Ni Cho, Chun-Feng Xin, Jae Seok Cho, Han Na Kang, Jiyeon Yun, Hye Ryun Kim, Byoung Chul Cho. Efficacy of MERTK inhibitor in combination with pembrolizumab in lung cancer [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 4081.