Purpose: Treatment with KRASG12C inhibitors such as sotorasib can produce substantial regression of tumors in some patients with non–small cell lung cancer (NSCLC). These patients require alternative treatment after acquiring resistance to the inhibitor. The mechanisms underlying this acquired resistance are unclear. The purpose of this study was to identify the mechanisms underlying acquired sotorasib resistance, and to explore potential treatments for rescuing patients with sotorasib-resistant KRASG12C NSCLC cells. Experimental Design: Clones of sotorasib-sensitive KRASG12C NSCLC H23 cells exposed to different concentrations of sotorasib were examined using whole-genomic transcriptome analysis, multiple receptor kinase phosphorylation analysis, and gene copy-number evaluation. The underlying mechanisms of resistance were investigated using immunologic examination, and a treatment aimed at overcoming resistance was tested in vitro and in vivo. Results: Unbiased screening detected subclonal evolution of MET amplification in KRASG12C NSCLC cells that had developed resistance to sotorasib in vitro. MET knockdown using small interfering RNA (siRNA) restored susceptibility to sotorasib in these resistant cells. MET activation by its amplification reinforced RAS cycling from its inactive form to its active form. In addition to RAS-mediated MEK–ERK induction, MET induced AKT activation independently of RAS. Crizotinib, a MET inhibitor, restored sensitivity to sotorasib by eliminating RAS–MEK–ERK as well as AKT signaling. MET/KRASG12C dual inhibition led to tumor shrinkage in sotorasib-resistant xenograft mice. Conclusions: MET amplification leads to the development of resistance to KRASG12C inhibitors in NSCLC. Dual blockade of MET and KRASG12C could be a treatment option for MET-amplified, KRASG12C-mutated NSCLC.

Purpose: EGFR-tyrosine kinase inhibitor (TKI) is a standard first-line therapy for activated EGFR-mutated non–small cell lung cancer (NSCLC). Treatment options for patients with acquired EGFR-TKI resistance are limited. HER3 mediates EGFR-TKI resistance. Clinical trials of the HER3-targeting antibody–drug conjugate patritumab deruxtecan (HER3-DXd) demonstrated its anticancer activity in EGFR-mutated NSCLC; however, the mechanisms that regulate HER3 expression are unknown. This study was conducted with the aim to clarify the mechanisms underlying HER3 regulation in EGFR-mutated NSCLC tumors and explored the strategy for enhancing the anticancer activity of HER3-DXd in EGFR-mutated NSCLC. Experimental Design: Paired tumor samples were obtained from 48 patients with EGFR-mutated NSCLC treated with EGFR-TKI(s). HER3 expression was immunohistochemically quantified with H-score, and genomic alteration and transcriptomic signature were tested in tumors from pretreatment to post-EGFR-TKI resistance acquisition. The anticancer efficacy of HER3-DXd and osimertinib was evaluated in EGFR-mutated NSCLC cells. Results: We showed augmented HER3 expression in EGFR-mutated tumors with acquired EGFR-TKI resistance compared with paired pretreatment samples. RNA sequencing revealed that repressed PI3K/AKT/mTOR signaling was associated with HER3 augmentation, especially in tumors from patients who received continuous EGFR-TKI therapy. An in vitro study also showed that EGFR-TKI increased HER3 expression, repressed AKT phosphorylation in multiple EGFR-mutated cancers, and enhanced the anticancer activity of HER3-DXd. Conclusions: Our findings help clarify the mechanisms of HER3 regulation in EGFR-mutated NSCLC tumors and highlight a rationale for combination therapy with HER3-DXd and EGFR-TKI in EGFR-mutated NSCLC.

Purpose: Although the efficacy of programmed cell death–1 (PD-1) blockade is generally poor for non–small cell lung cancer (NSCLC) with activating mutations of the epidermal growth factor receptor (EGFR) gene, EGFR tyrosine kinase inhibitors (TKIs) may improve the tumor immune microenvironment. We performed a randomized study to assess whether nivolumab improves outcome compared with chemotherapy in such patients previously treated with EGFR-TKIs. Patients and Methods: Patients with EGFR-mutated NSCLC who acquired EGFR-TKI resistance not due to a secondary T790M mutation of EGFR were randomized 1:1 to nivolumab (n = 52) or carboplatin–pemetrexed (n = 50). The primary endpoint was progression-free survival (PFS). Results: Median PFS and 1-year PFS probability were 1.7 months and 9.6% for nivolumab versus 5.6 months and 14.0% for carboplatin–pemetrexed [log-rank P < 001; hazard ratio (HR) of 1.92, with a 60% confidence interval (CI) of 1.61–2.29]. Overall survival was 20.7 and 19.9 months [HR, 0.88 (95% CI, 0.53–1.47)], and response rate was 9.6% and 36.0% for nivolumab and carboplatin–pemetrexed, respectively. No subgroup including patients with a high tumor mutation burden showed a substantially longer PFS with nivolumab than with carboplatin-pemetrexed. The T-cell–inflamed gene expression profile score (0.11 vs. −0.17, P = 0.036) and expression of genes related to cytotoxic T lymphocytes or their recruitment were higher in tumors that showed a benefit from nivolumab. Conclusions: Nivolumab did not confer a longer PFS compared with carboplatin-pemetrexed in the study patients. Gene expression profiling identified some cases with a favorable tumor immune microenvironment that was associated with nivolumab efficacy.

BACKGROUND: Precise stratification of patients with non–small cell lung cancer (NSCLC) is needed for appropriate application of PD-1/PD-L1 blockade therapy. METHODS: We measured soluble forms of the immune-checkpoint molecules PD-L1, PD-1, and CTLA-4 in plasma of patients with advanced NSCLC before PD-1/PD-L1 blockade. A prospective biomarker-finding trial (cohort A) included 50 previously treated patients who received nivolumab. A retrospective observational study was performed for patients treated with any PD-1/PD-L1 blockade therapy (cohorts B and C), cytotoxic chemotherapy (cohort D), or targeted therapy (cohort E). Plasma samples from all patients were assayed for soluble immune-checkpoint molecules with a highly sensitive chemiluminescence-based assay. RESULTS: Nonresponsiveness to PD-1/PD-L1 blockade therapy was associated with higher concentrations of these soluble immune factors among patients with immune-reactive (hot) tumors. Such an association was not apparent for patients treated with cytotoxic chemotherapy or targeted therapy. Integrative analysis of tumor size, PD-L1 expression in tumor tissue (tPD-L1), and gene expression in tumor tissue and peripheral CD8 ⁺ T cells revealed that high concentrations of the 3 soluble immune factors were associated with hyper or terminal exhaustion of antitumor immunity. The combination of soluble PD-L1 (sPD-L1) and sCTLA-4 efficiently discriminated responsiveness to PD-1/PD-L1 blockade among patients with immune-reactive tumors. CONCLUSION: Combinations of soluble immune factors might be able to identify patients unlikely to respond to PD-1/PD-L1 blockade as a result of terminal exhaustion of antitumor immunity. Our data suggest that such a combination better predicts, along with tPD-L1, for the response of patients with NSCLC. TRIAL REGISTRATION: UMIN000019674. FUNDING: This study was funded by Ono Pharmaceutical Co. Ltd. and Sysmex Corporation.

Background Immune checkpoint inhibitors (ICIs) confer a survival benefit in many cancer types. Given that the survival outcome for cancer of unknown primary site (CUP) remains poor, we investigated the potential of CUP for immunotherapy. Methods A total of 164 patients with CUP (favorable subset, 34 patients; unfavorable subset, 130 patients) who were treated between January 2009 and March 2017 was identified from a review of medical records at Kindai University Hospital. They included 92 patients for whom pretreatment tumor tissue was available both for determination of programmed cell death–ligand 1 expression and tumor-infiltrating lymphocyte (TIL) density by immunohistochemistry (IHC) and for immune-related gene expression profiling (irGEP). The results of irGEP for CUP were compared with published data for ICI-treated solid cancers classified into progressive disease (PD) and non-PD subsets according to their best response to ICIs. Results The median overall survival of all CUP patients was 29.3 months (95% confidence interval [CI], 15.7–not reached) and 7.1 months (95% CI, 5.0–9.4) for favorable and unfavorable subsets, respectively. IHC and irGEP revealed that pretreatment immune activity—including expression of immune checkpoint molecules—for CUP was similar to that for ICI-responsive malignancies (antitumor immune cell signatures: CUP versus PD, P = 0.002–0.067; CUP versus non-PD, P = 0.591–0.999), although VEGFA expression was associated with suppression of antitumor immunity in CUP (P = 0.008, false discovery rate = 0.010). In addition, one case of CUP in the unfavorable subset that was associated with prominent PD-L1 expression on TILs and showed a durable response to nivolumab is presented. Conclusions The survival outcome of CUP remains unsatisfactory. However, our clinical and immune profiling of CUP has revealed a potential to benefit from immunotherapy, with ICIs thus being a potential option for CUP treatment.