Abstract CT235: RNA-seq molecular subtypes and gene expression signatures in the phase 3 IMpower151 study of 1L bevacizumab + pemetrexed/paclitaxel ± atezolizumab in metastatic NSCLC
Authors: Zhou Caicun , Sun Charlie , Huang Stacey , Dong Xiaorong , Chen Gongyan , Wang Zhehai , Wu Xianghua , Yao Yu , Zhang Yiping , Cheng Ying , Pan Hongming , Zhang Xiaodong , Cui Jiuwei , Wang Lifeng , Chen Xi , Li Xiaoling , Wang Ziping , Wang Qiming , He Jianxing , Wang Mengzhao , Qian Li , Hamidi Habib , Li Shanshan , Ballinger Marcus , Shames David S. , Srivastava Minu 
Published: April 2024

Introduction IMpower151 (NCT04194203) was a phase 3 study to evaluate the efficacy and safety of atezolizumab, bevacizumab, carboplatin, plus paclitaxel or pemetrexed (ABCP) vs BCP, as 1L treatment for metastatic nsqNSCLC. IMpower151 did not meet its primary endpoint of INV-PFS. The objectives of this biomarker analysis were to characterize the molecular subtypes of metastatic nsqNSCLC and to explore the relationship between molecular subtype, predefined gene expression signatures, PD-L1 status and clinical outcomes with ABCP and BCP.

Methods RNA sequencing of 250 nsqNSCLC tumor samples from IMpower151 was analyzed in the ACBP (n=123) and BCP (n=127) treatment arms. Non-negative matrix factorization (NMF) was applied to variably expressed genes to define molecular subtypes. Gene expression signatures were defined based on previously published associations with their respective biology. Tumor PD-L1 levels were determined by SP263 immunohistochemistry (Ventana).

Results No PD-L1 dependent difference of survival benefit of ABCP compared to BCP was observed at the cutoff of TC 1% or TC 50%. Four molecular subtypes (NMF1-NMF4) were identified based on RNA sequencing. NMF1 (n=78) were immune-depleted and had low tumor proliferation. NMF2 (n=73) were characterized by low level of anti-tumor immune cells, increased expression of stromal signatures and high tumor proliferation. NMF3 (n=65) had the most inflamed transcriptomic profile with high enrichment of immune cells, and increased expression of stromal signatures as well. NMF4 (n=34) had the enrichment of granulocytes, a less inflamed immunophenotype and decreased expression of stromal signatures. The positive rate of PD-L1 expression with TC&gt;=1% was significantly lower in NMF1 compared to other subtypes. None of patients with the four NMF subtypes showed significantly longer PFS or OS with ABCP than BCP. Overall, patients with NMF2 showed numerically shorter PFS and patients with NMF3 showed numerically longer PFS than other subtypes. Gene expression signatures of antitumor cytokines are correlated with survival benefit of ABCP compared to BCP. Patients with high expression level of antitumor cytokines showed substantially improved PFS and OS benefit from ABCP than BCP in both ITT population and EGFR mutation population.

Conclusion Four molecular subtypes of nsqNSCLC with different immune-cell and tumor microenvironmental features were characterized. NMF2 may identify a fibrotic and immune-depleted subgroup correlated with worse prognosis. NMF3 may identify an immune-inflamed subgroup correlated with better prognosis. Neither NMF subtypes nor PD-L1 IHC level showed a correlation with survival benefit of ABCP controlled by BCP. The gene expression signature of antitumor cytokines could serve as a potential predictive biomarker for survival benefit of ABCP in metastatic nsqNSCLC including EGFR mutant patients. This finding is based on the exploratory analysis of a single clinical trial with limited sample size. It needs further investigation in other cohorts of tumor tissues and with larger clinical potential in blood samples as well.

Citation Format: Caicun Zhou, Charlie Sun, Stacey Huang, Xiaorong Dong, Gongyan Chen, Zhehai Wang, Xianghua Wu, Yu Yao, Yiping Zhang, Ying Cheng, Hongming Pan, Xiaodong Zhang, Jiuwei Cui, Lifeng Wang, Xi Chen, Xiaoling Li, Ziping Wang, Qiming Wang, Jianxing He, Mengzhao Wang, Li Qian, Habib Hamidi, Shanshan Li, Marcus Ballinger, David S. Shames, Minu Srivastava. RNA-seq molecular subtypes and gene expression signatures in the phase 3 IMpower151 study of 1L bevacizumab + pemetrexed/paclitaxel ± atezolizumab in metastatic NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT235.