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Despite success in hematologic malignancies, the treatment landscape of chimeric antigen receptor (CAR) T cell therapy for solid tumors remains limited. Claudin18.2 (CLDN18.2)-redirected CAR T cells showed promising efficacy against gastric cancer (GC) in a preclinical study. Here we report the interim analysis results of an ongoing, open-label, single-arm, phase 1 clinical trial of CLDN18.2-targeted CAR T cells (CT041) in patients with previously treated, CLDN18.2-positive digestive system cancers (NCT03874897). The primary objective was safety after CT041 infusion; secondary objectives included CT041 efficacy, pharmacokinetics and immunogenicity. We treated 37 patients with one of three CT041 doses: 2.5 × 108, 3.75 × 108 or 5.0 × 108 cells. All patients experienced a grade 3 or higher hematologic toxicity. Grade 1 or 2 cytokine release syndrome (CRS) occurred in 94.6% of patients. No grade 3 or higher CRS or neurotoxicities, treatment-related deaths or dose-limiting toxicities were reported. The overall response rate (ORR) and disease control rate (DCR) reached 48.6% and 73.0%, respectively. The 6-month duration of response rate was 44.8%. In patients with GC, the ORR and DCR reached 57.1% and 75.0%, respectively, and the 6-month overall survival rate was 81.2%. These initial results suggest that CT041 has promising efficacy with an acceptable safety profile in patients with heavily pretreated, CLDN18.2-positive digestive system cancers, particularly in those with GC.

KRAS is the most frequently mutated oncogene in human malignancies, observed in approximately two in five colorectal cancers (CRC). KRAS mutations were historically considered “undruggable” ten years ago and associated with resistance to EGFR targeted therapy. The success of finding allele-specific covalent KRASG12C inhibitors recently has made markedly breakthrough in KRAS targeted therapy, and has accelerated the discovery of agents targeting other KRAS mutants, such as G12D and G12V. Evidence in preclinical and clinical settings has proved excellent efficacy of several inhibitors in KRAS mutant CRC. Sotorasib and Adagrasib are currently changing the treatment paradigm for patients with metastatic CRC harboring KRASG12C mutation. The phenomenon that KRASG12C inhibition shows inferior efficacy in patients with CRC compared with non-small cell lung cancer has been observed in clinic due to drug resistance, and combination strategies to overcome the resistance are now being investigated in clinical trials. Here, we review the development of KRAS targeted treatment in CRC, mechanisms of resistance and potential combination strategies to improve efficacy.

PURPOSE To investigate the efficacy of PD-1/PD-L1 inhibitors plus chemotherapy versus anti–PD-1/PD-L1 monotherapy in advanced microsatellite instability (MSI)/mismatch repair-deficient (dMMR) gastrointestinal cancers. METHODS We retrospectively recruited patients with MSI/dMMR gastrointestinal cancer who received anti–PD-1/PD-L1 with or without chemotherapy and compared objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) of PD-1/PD-L1 inhibitor plus chemotherapy (chemo-anti–PD-1/PD-L1 group) and PD-1/PD-L1 inhibitor alone (anti–PD-1/PD-L1 group). Propensity score–based overlap weighting analysis was conducted to adjust the baseline covariable imbalance. Sensitivity analysis was performed to confirm the stability of the results by propensity score matching and multivariable Cox and logistic regression models. RESULTS A total of 256 patients were eligible, with 68 and 188 receiving chemo-anti–PD-1/PD-L1 and anti–PD-1/PD-L1, respectively. The chemo-anti–PD-1/PD-L1 group showed significant improvements versus the anti–PD-1/PD-L1 group in ORR (61.8% v 38.8%; P = .001), DCR (92.6% v 74.5%; P = .002), PFS (median PFS [mPFS], not reached [NR] v 27.9 months; P = .004), and OS (median OS [mOS], NR v NR; P = .014). After overlap weighting, the improvements tended to be more significant with chemo-anti–PD-1/PD-L1 versus anti–PD-1/PD-L1 in ORR (62.5% v. 38.3%; P < .001), DCR (93.8% v 74.2%; P < .001), PFS (mPFS, NR v 26.0 months; P = .004), and OS (mOS, NR v NR; P = .010). These results were solidified through sensitivity analysis. CONCLUSION Chemo-anti–PD-1/PD-L1 is superior to anti–PD-1/PD-L1 in MSI/dMMR gastrointestinal cancers with improved efficacy.

BackgroundThe human leukocyte antigen class I (HLA-I) genotype has been linked with differential immune responses to infectious disease and cancer. However, the clinical relevance of germline HLA-mediated immunity in gastrointestinal (GI) cancer remains elusive.MethodsThis study retrospectively analyzed the genomic profiling data from 84 metastatic GI cancer patients treated with immune checkpoint blockade (ICB) recruited from Peking University Cancer Hospital (PUCH). A publicly available dataset from the Memorial Sloan Kettering (MSK) Cancer Center (MSK GI cohort) was employed as the validation cohort. For the PUCH cohort, we performed HLA genotyping by whole exome sequencing (WES) analysis on the peripheral blood samples from all patients. Tumor tissues from 76 patients were subjected to WES analysis and immune oncology-related RNA profiling. We studied the associations of two parameters of germline HLA as heterozygosity and evolutionary divergence (HED, a quantifiable measure of HLA-I evolution) with the clinical outcomes of patients in both cohorts.ResultsOur data showed that neither HLA heterozygosity nor HED at the HLA-A/HLA-C locus correlated with the overall survival (OS) in the PUCH cohort. Interestingly, in both the PUCH and MSK GI cohorts, patients with high HLA-B HED showed a better OS compared with low HLA-B HED subgroup. Of note, a combinatorial biomarker of HLA-B HED and tumor mutational burden (TMB) may better stratify potential responders. Furthermore, patients with high HLA-B HED were characterized with a decreased prevalence of multiple driver gene mutations and an immune-inflamed phenotype.ConclusionsOur results unveil how HLA-B evolutionary divergence influences the ICB response in patients with GI cancers, supporting its potential utility as a combinatorial biomarker together with TMB for patient stratification in the future.

Background: In microsatellite instability (MSI)/mismatch repair-deficient (dMMR) gastrointestinal cancers, the optimum therapy after the progression of immune checkpoint inhibitors (ICIs) is yet unknown. Here, we compared the efficacy of programmed death 1 (PD1)/programmed death ligand-1 (PD-L1) inhibitors plus other therapy and chemotherapy with or without targeted therapy in MSI/dMMR gastrointestinal cancer patients after progression on anti-PD1/PD-L1 monotherapy. Methods: We retrospectively recruited MSI/dMMR gastrointestinal cancer patients who had progressed on anti-PD1/PD-L1 monotherapy. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and PFS ratio (PFSr) were compared between patients who received anti-PD1/PD-L1 plus other therapy (ICI-plus group) and patients who received chemotherapy with or without targeted therapy (chemo-targeted group). Results: In total, 26 and 25 patients were recruited in the ICI-plus group and chemo-targeted group, respectively. Significantly better DCR (80.8% vs. 44.0%, p = 0.007), PFS (median PFS 6.9 months vs. 3.0 months, p = 0.001), OS (median OS NR vs. 14.1 months, p = 0.043), and PFSr (2.4 vs. 0.9, p = 0.021), along with a numerically higher ORR (23.1% vs. 12.0%, p = 0.503) were observed in the ICI-plus group compared with the chemo-targeted group. Multivariate analyses identified the therapy regimen as an important prognostic factor in gastrointestinal cancers. Conclusions: Compared to conventional chemotherapy with or without targeted therapy, continuing anti-PD1/PD-L1 in combination with other treatments showed better clinical outcomes in MSI/dMMR gastrointestinal cancer patients who progressed on PD1/PD-L1 blockade, which should be validated prospectively in clinical trials.

Purpose The human epidermal growth factor receptor 2 (HER2) is an established therapeutic target for various kinds of solid tumors. HER2 amplification occurs in approximately 1% to 6% of colorectal cancer. In this study, we aimed to assess the efficacy and safety of trastuzumab in combination with chemotherapy in HER2-positive metastatic colorectal cancer (mCRC).Materials and Methods An open-label, phase II trial (Clinicaltrials.gov: NCT03185988) was designed to evaluate the antitumor activity of trastuzumab and chemotherapy in HER2-positive digestive cancers excluding gastric cancer in 2017. Patients from this trial with HER2-positive, KRAS/BRAF wild-type, unresectable mCRC were analyzed in this manuscript. Eligible patients were treated with trastuzumab (8 mg/kg loading dose and then 6 mg/kg every 3 weeks) and irinotecan (120 mg/m2 days 1 and 8 every 3 weeks). The primary endpoint was the objective response rate.Results Twenty-one HER2-positive mCRC patients were enrolled in this study. Seven patients (33.3%) achieved an objective res-ponse, and 11 patients (52.4%) had stable disease as their best response. The median progression-free survival (PFS) was 4.3 months (95% confidence interval, 2.7 to 5.9). Four of the 21 patients (19.0%) had grade 3 adverse events, including leukopenia, neutropenia, urinary tract infection, and diarrhea. No treatment-related death was reported. Exploratory analyses revealed that high tumor tissue HER2 copy number was associated with better therapeutic response and PFS. Alterations in the mitogen-activated protein kinase pathway, HER2 gene, phosphoinositide 3-kinase/AKT pathway, and cell cycle control genes were potential drivers of trastuzumab resistance in mCRC.Conclusion Trastuzumab combined with chemotherapy is a potentially effective and well-tolerated therapeutic regimen in mCRC with a high HER2 copy number.

Purpose RC48 contains the novel humanized anti-HER2 antibody hertuzumab conjugated to MMAE via a cleavable linker. A phase I study was initiated to evaluate the toxicity, MTD, PK, and antitumor activity of RC48 in patients with HER2-overexpressing locally advanced or metastatic solid carcinomas, particularly gastric cancer. Patients and methods This was a 2-part phase I study. Successive cohorts of patients received escalating doses of RC48 (0.1 mg/kg, 0.5 mg/kg, 1.0 mg/kg, 2.0 mg/kg, 2.5 mg/kg, and 3.0 mg/kg). Dose expansion proceeded at the dose of 2.0 mg/kg Q2W. The efficacy and safety set included all patients who received at least one dose of RC48. Results Fifty-seven patients were enrolled, the MTD was unavailable due to termination of 3.0 mg/kg cohort; 2.5 mg/kg Q2W was declared the RP2D. RC48 was well tolerated, the most frequent grade 3 or worse TRAEs included neutropenia (19.3%), leukopenia (17.5%), hypoesthesia (14.0%), and increased conjugated blood bilirubin (8.8%). Four deaths occurred during the whole study, three of which were believed to be related to RC48. Overall, ORR and DCR were 21.0% (12/57) and 49.1% (28/57). Notably, patients who were HER2 IHC2+/FISH- responded similarly to those who were IHC2+/FISH+ and IHC3+, with ORRs of 35.7% (5/14), 20% (2/10), and 13.6% (3/22), respectively. In patients who were pretreated with HER2-targeted drugs, RC48 also showed promising efficacy, with ORR of 15.0% (3/20) and DCR of 45.0% (9/20). Conclusion RC48 was well tolerated and showed promising antitumor activity in HER2-positive solid tumors, including gastric cancer with HER2 IHC 2+/FISH- status. Clinical trial information NCT02881190.

The association between genetic variations and immunotherapy benefit has been widely recognized, while such evidence in gastrointestinal cancer remains limited. We analyzed the genomic profile of 227 immunotherapeutic gastrointestinal cancer patients treated with immunotherapy, from the Memorial Sloan Kettering (MSK) Cancer Center cohort. A gastrointestinal immune prognostic signature (GIPS) was constructed using LASSO Cox regression. Based on this signature, patients were classified into two subgroups with distinctive prognoses (p N = 54) and Peking University Cancer Hospital cohort (N = 92). Multivariate analysis revealed that the GIPS was an independent prognostic biomarker. Notably, the GIPS-high tumor was indicative of a T-cell-inflamed phenotype and immune activation. The findings demonstrated that GIPS was a powerful predictor of immunotherapeutic survival in gastrointestinal cancer and may serve as a potential biomarker guiding immunotherapy treatment decisions.

Background Anti-HER2 antibodies combined with immune checkpoint inhibitors exert synergistic effects on innate and adaptive immunity. This phase Ib study assessed the safety and efficacy of KN026 plus KN046 in patients with HER2-positive gastrointestinal cancer. Methods Treatment naïve or pretreated locally advanced or metastasis, gastrointestinal cancer patients with HER2 alterations were enrolled. Four dose combinations of KN026 (20 mg/kg Q2W or 30 mg/kg Q3w) and KN046 (3 mg/kg Q2w or 5 mg/kg Q2w/Q3w) were designed. The primary objective was to assess dose-limiting toxicity (DLT) and preliminary efficacy. Results Overall, 47 patients were enrolled. No DLTs were observed. Any-grade treatment-related adverse events (TRAEs) were observed in 42 patients (89.4%). Anemia (40.4%), infusion-related reactions (36.2%), and elevated alanine transaminase (ALT) (27.7%) were the most common TRAEs. Grade 3 or worse TRAEs occurred in 17% of the patients. Twenty-four of the 47 patients suffered immune-related adverse events (irAEs). Rash (14.9%), hypothyroidism (6.4%) and interstitial lung disease (6.4%) were most commonly observed. Forty of 47 patients were included in efficacy assessment. The objective response rates (ORRs) in the patients with HER2-positive gastric cancer and gastroesophageal junction (GC/GEJ) adenocarcinoma in the first-line and late-line settings were 71.4% and 37.5%, respectively. No disease remission was observed in the patients with low HER2 expression or HER2 mutation. Notably, half of the patients (2/4) pretreated with trastuzumab and a programmed cell death-1 (PD-1) blockade achieved partial response (PR). Conclusions and Relevance : KN026 combined with KN046 exhibited acceptable safety profiles and encouraging efficacy in patients with HER2-positive gastrointestinal cancer. Trial registration: ClinicalTrials.gov, NCT NCT04040699, Registered August 1,2019.

Regorafenib and fruquintinib are tyrosine kinase inhibitors that are recommended for refractory colorectal cancer (CRC) in China. However, to date, no head-to-head trials have been conducted to guide clinical practice.An ambispective observational cohort study was conducted in Beijing Cancer Hospital. Patients with metastatic CRC who received regorafenib or fruquintinib were retrospectively collected between January 2018 and April 2020, and prospectively enrolled between May 2020 and February 2021. The primary outcome was time-to-treatment failure (TTF), and secondary outcomes were overall survival (OS) and adverse events. An additional goal of the study was to explore the appropriate sequence of regorafenib and fruquintinib treatment.A total of 366 patients with metastatic CRC were enrolled to receive regorafenib (n = 260) or fruquintinib (n = 106) between January 2018 and February 2021. No difference was observed for median TTF (regorafenib 2.7 months vs. fruquintinib 3.1 months, P = .200) or median OS (regorafenib 13.8 months vs. fruquintinib 11.3 months, P = .527). The propensity score analysis showed similar results for median TTF and median OS between the 2 groups, as did the results of subgroup analysis for prospective set (n = 146). For sequence analysis, patients with regorafenib followed by fruquintinib (n = 84) showed longer OS than that with the reverse (n = 29) (28.1 months vs. 18.4 months, P = .024). Most patients tolerated regorafenib at a reduced dose (93.1%), and most patients tolerated fruquintinib at a standard dose (68.9%). The incidences of most adverse events were similar between the two groups, while any grade of hand-foot skin reaction and hyperbilirubinemia were more frequently observed in the regorafenib group and ≥grade 3 hypertension was more common in the fruquintinib group.Regorafenib and fruquintinib had similar efficacy and toxicity profiles with various frequency. Regorafenib followed by fruquintinib showed longer OS than the reverse, but the sequence needs to be further confirmed.

Background A significant subset of mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) gastric adenocarcinomas (GAC) are resistant to immune checkpoint inhibitors (ICIs), yet the underlying mechanism remains largely unknown. We sought to investigate the genomic correlates of the density of tumor-infiltrating immune cells (DTICs) and primary resistance to ICI treatment. Methods Four independent cohorts of MSI-H GAC were included: (i) the surgery cohort (n = 175) with genomic and DTIC data, (ii) the 3DMed cohort (n = 32) with genomic and PD-L1 data, (iii) the Cancer Genome Atlas (TCGA) cohort (n = 73) with genomic, transcriptomic, and survival data, and (iv) the ICI treatment cohort (n = 36) with pre-treatment genomic profile and ICI efficacy data. Results In the dMMR/MSI-H GAC, the number of mutated genes in the PI3K-AKT-mTOR pathway (NMP) was positively correlated with tumor mutational burden (P + (P + (P = 0.065), CD8+ (P = 0.004), and FOXP3+ cells (P = 0.033) in the central-tumor rather than invasive-margin area, and the transcription of immune-related genes. Compared to the NMP-low (NMP = 0/1) patients, the NMP-high (NMP ≥ 2) patients exhibited a poorer objective response rate (29.4% vs. 85.7%, P P = 0.019), and overall survival (HR = 3.59, P = 0.048) upon ICI treatment. Conclusions Higher NMP was identified as a potential predictor of lower DTICs and primary resistance to ICIs in the dMMR/MSI-H GAC. Our results highlight the possibility of using mutational data to estimate DTICs and administering the PI3K-AKT-mTOR inhibitor as an immunotherapeutic adjuvant in NMP-high subpopulation to overcome the resistance to ICIs.

Objective: Immune checkpoint inhibitors (ICIs) have achieved remarkable results in cancer treatments. However, there is no effectivepredictive biomarker for gastrointestinal (GI) cancer. Methods: We conducted integrative analyses of the genomic and survival data of ICI-treated GI cancer patients from the MemorialSloan Kettering Cancer Center cohort (MSK-GI, n = 227), the Janjigian cohort (n = 40), and the Peking University Cancer Hospital& Institute cohort (PUCH, n = 80) to determine the possible associations between DNA damage response and repair (DDR) genemutations and clinical outcomes. Data from The Cancer Genome Atlas database were analyzed to determine the possible correlationsbetween DDR gene mutations and the tumor microenvironment. Results: In the MSK cohort, the presence of ≥ 2 DDR gene mutations was correlated with prolonged overall survival (OS). TheJanjigian and PUCH cohorts further confirmed that subgroups with ≥ 2 DDR gene mutations displayed a prolonged OS and ahigher durable clinical benefit. Furthermore, the DDR gene mutation load could be considered as an independent prognostic factor,and exhibited a potential predictive value for survival in GI cancer patients treated with ICIs. Mechanistically, we showed that thepresence of ≥ 2 DDR gene mutations was correlated with higher levels of tumor mutation burden, neoantigen, and T cell infiltration. Conclusions: The DDR gene mutation status was correlated with favorable clinical outcomes in GI cancer patients receiving ICIs,which could serve as a potential biomarker to guide patient selection for immunotherapy.

Background: Combinatorial inhibition of epidermal growth factor receptor (EGFR) and BRAF shows remarkable clinical benefits in patients with BRAF V600E-mutant metastatic colorectal cancer (mCRC). However, the tumor may inevitably develop resistance to the targeted therapy, thereby limiting the response rate and durability. This study aimed to determine the genetic alterations associated with intrinsic and acquired resistance to EGFR/BRAF inhibitors in BRAF V600E-mutant mCRC. Methods: Targeted sequencing of 520 cancer-related genes was performed in tumor tissues and in plasma samples collected from patients with BRAF V600E-mutant mCRC, who were treated with EGFR/BRAF ± MEK inhibitors, before and after the targeted treatment. Clinical benefit was defined as an objective response or a stable disease lasting longer than the median progression-free survival (PFS). Results: In all, 25 patients with BRAF V600E-mutant mCRC were included in this study. Those with RNF43 mutations ( n = 8) were more likely to achieve clinical benefit from EGFR/BRAF inhibitors than those with wild-type RNF43 (87.5% versus 37.5%, p = 0.034). Genetic alterations in receptor tyrosine kinase genes ( n = 6) were associated with worse PFS ( p = 0.005). Among the 23 patients whose disease progressed after the EGFR/BRAF-targeted therapy, at least one acquired resistance-related mutation was detected in 12 patients. Acquired mutations were most frequently observed in the mitogen-activated protein kinase pathway-related genes ( n = 9), including KRAS (G12D and Q61H/R), NRAS (Q61L/R/K and amplification), BRAF (amplification), and MEK1 (K57T). MET amplification and PIK3R1 Q579fs mutation emerged in three patients and one patient, respectively, after disease progression. Conclusion: Multiple genetic alterations are associated with clinical benefits and resistance to EGFR/BRAF inhibitors in BRAF V600E-mutant mCRC. Our findings provide novel insights into strategies for overcoming resistance to EGFR/BRAF inhibitors in patients with BRAF V600E-mutant mCRC.

e15504 Background: Microsatellite stable (MSS) metastatic colorectal cancer (CRC) lacks effective treatments and has a poor prognosis. The aim of this study was to identify patients who could benefit from immunotherapy combined with anti-angiogenic therapy. Exploration of predictive biomarkers could help to maximize the clinical benefits. Methods: In total, FFPE tissues samples before immunotherapy combined with anti-angiogenic therapy of 21 patients were successfully tested for tumor microenvironments (TMEs) by multiple immunofluorescence, of which 11 of them were successfully detected by 733-gene NGS panel in a CLIA-certified laboratory. The correlation between gene variations and clinical durable benefit (DCB: PR, or SD≥6 months), PFS and TMEs were analyzed by Fisher's test, K-M survival curve analysis and Mann Whitney analysis respectively. Results: Significant difference was detected between FAT4 mutation (FAT4-MUT) and FAT4 wildtype (FAT4-WT) regarding DCB (100%, 4/4 vs 17%, 1/7, P = 0.0152) and progress-free survival (median PFS, 13.8 months vs 2.8 months, LogRank P = 0.003). There was no significant difference in TMB level between DCB and NDB (SD＜6 months, or PD) groups (12 mut/Mb vs 6 mut/Mb, P = 0.0823) or between FAT4-MUT and FAT4-WT (11 mut/Mb vs 6 mut/Mb, P = 0.3697). TMEs analyses revealed that the CD3+CD4+ T cell proportion was tended to be higher in FAT4-MUT (0.7% vs 0.3%, P = 0.054). Further TIMER2.0 data showed FAT4-MUT was significantly associated with higher Immune infiltration of four immune cells, including CD4+ T cell in both colon and rectal adenocarcinoma, CD8+ central memory T cell, B cell, and Macrophage in colon adenocarcinoma. Conclusions: Our findings indicated that FAT4 mutation serves as a potential novel biomarker correlated with a better response to immunotherapy combined with anti-angiogenic therapy in MSS metastatic CRC, which may be related to the activation of CD4 T cell infiltration. However, these need to be validated by further cohort expansion.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article was retracted at the request of the authors. The authors of this abstract have advised that full agreement between authors and sponsors on publication of the abstract has not been reached and they are therefore unable to publish this data at present.

Biomarkers for immune checkpoint inhibitors (ICIs) are limited in gastrointestinal cancer. Peripheral blood lymphocyte subset and associated dynamic changes were retrospectively analyzed in patients with gastrointestinal cancer treated with ICIs. Cox regression and Kaplan-Meier analyses were conducted for survival. A total of 80 patients were enrolled. Baseline CD4

BackgroundMicrosatellite instability (MSI) represents the first pan-cancer biomarker approved to guide immune checkpoint blockade (ICB) treatment. However its widespread testing, especially outside of gastrointestinal cancer, is hampered by tissue availability.MethodsAn algorithm for detecting MSI from peripheral blood was established and validated using clinical plasma samples. Its value for predicting ICB efficacy was evaluated among 60 patients with advanced gastrointestinal cancer. The landscape of MSI in blood was also explored among 5138 advanced solid tumors.ResultsThe algorithm included 100 microsatellite markers with high capture efficiency, sensitivity, and specificity. In comparison with orthogonal tissue PCR results, the method displayed a sensitivity of 82.5% (33/40) and a specificity of 96.2% (201/209), for an overall accuracy of 94.0% (234/249). When the clinical validation cohort was dichotomized by pretreatment blood MSI (bMSI), bMSI-high (bMSI-H) predicted both improved progression-free survival and overall survival than the blood microsatellite stable (bMSS) patients (HRs: 0.431 and 0.489, p=0.005 and 0.034, respectively). Four patients with bMSS were identified to have high blood tumor mutational burden (bTMB-H) and trended towards a better survival than the bMSS-bTMB-low (bTMB-L) subset (HR 0.026, 95% CI 0 to 2.635, p=0.011). These four patients with bMSS-bTMB-H plus the bMSI-H group collectively displayed significantly improved survival over the bMSS-bTMB-L patients (HR 0.317, 95% CI 0.157 to 0.640, pConclusionsWe have developed a reliable and robust next generation sequencing-based bMSI detection strategy which, in combination with a panel enabling concurrent profiling of bTMB from a single blood draw, may better inform ICB treatment.

Tumor-associated macrophages (TAMs) can dampen the antitumor activity of T cells, yet the underlying mechanism remains incompletely understood. Here, we show that C1q

Circulating tumor DNA (ctDNA) is considered an ideal sample type for genotyping patients with advanced unresectable cancer to inform treatment decision. It may better capture tumor heterogeneity, especially in gastric adenocarcinoma (GAC). However, there exists little evidence regarding genomic profiling of Chinese advanced GAC patients from ctDNA. Blood samples were obtained from 200 advanced GAC patients. Next-generation sequencing (NGS) was performed on ctDNA using a validated 150-gene panel. Blood tumor mutation burden (bTMB) was calculated according to the NGS results. Blood microsatellite instability (bMSI) status was determined by targeted sequencing of 100 microsatellite loci. One hundred sixty-nine (84.5%) patients carried at least one genomic alteration and 138 (69%) patients had at least one deleterious or likely deleterious alteration (del-alteration). The clonal fraction of del-alterations was higher than that of non-del-alterations (80.1% vs 54.5%, P < 0.0001). The most frequently altered genes were TP53 (38%), LRP1B (20%), MYC (13.5%), ERBB2 (12.5%), and KRAS (11.5%). The alterations were most enriched in the TP53/cell cycle (52%) and the RTK-Ras-MAPK pathway (51.5%). The median bTMB was two (range 0 to 42). Eight patients were identified to be high bMSI, with higher median bTMB than the blood microsatellite stable (bMSS) patients (15 vs 2, P = 0.0062). Patients harboring del-alterations of the DDR pathway had significantly higher percentages of high bTMB and bMSI-H patients than the wild-type subgroup (61.1% vs 6.5%, P < 0.0001; 33.3% vs 1.7%, P = 0.0002). A total of 45.5% cases harbored at least one potentially actionable alteration and one patient achieved complete response after receiving matched targeted therapy. Our study uncovered the molecular characterization of Chinese patients with advanced GAC from ctDNA, including genomic alteration, bTMB, and bMSI status. The findings suggested that targeted NGS-based ctDNA analysis may help inform the clinical decision in advanced GAC. KEY MESSAGES: We report the molecular profiling of the largest Chinese advance stage GACs cohort using a CLIA-certified ctDNA assay. Potentially actionable genomic alterations were identified in 45.5% of patients, suggesting clinical utility for ctDNA NGS in advance stage GACs. There was evidence of clinical benefit in one GAC patient with MET amplification treated with MET inhibitor.

Gastrointestinal (GI) cancers represent a major public health problem worldwide. Due to the late detection and high heterogeneity of GI cancers, traditional treatments, including surgery, radiotherapy, chemotherapy, and targeted therapy, have shown limited effects, and the overall prognosis of these patients remains poor. Recently, immunotherapy, involving programmed cell death-1 (PD-1) and its ligand (PD-L1), has shown promising efficacy in several solid cancers and seems to have become a potential treatment option for GI cancers This review focuses on data on the development of immunotherapy-based clinical trials in esophageal cancer, gastric cancer, and colorectal cancer. The predictive biomarkers and combination strategies in clinical trials and translational medicine are also discussed. Finally, prospects for immunotherapy in the treatment of GI cancers are described. Although only a small proportion of patients with GI cancers respond to PD-1/PD-L1 blockade, we strongly believe that precision immunotherapy might improve the overall survival of many more GI cancer patients in the future., Graphical Abstract, Public Summary • Immunotherapy has revolutionized the therapeutic landscape of gastrointestinal cancer, based on a series of clinical trials conducted in recent years. • The next level of predictive biomarker of the response to immune checkpoint inhibitors (ICIs) should address the integration of current multi-omics biomarkers with an interdisciplinary approach. • The emerging combination strategies based on ICIs should be more defined in the specific population. • It is imperative to understand mechanism of acquired resistance to ICIs and explore therapeutic strategies to reverse it.

BackgroundDespite the great achievements made in immune-checkpoint-blockade (ICB) in cancer therapy, there are no effective predictive biomarkers in gastrointestinal (GI) cancer.MethodsThis study included 93 metastatic GI patients treated with ICBs. The first cohort comprising 73 GI cancer patients were randomly assigned into discovery (n=44) and validation (n=29) cohorts. Comprehensive genomic profiling was performed on all samples to determine tumor mutational burden (TMB) and copy-number alterations (CNAs). A subset of samples was collected for RNA immune oncology (IO) panel sequencing, microsatellite instability (MSI)/mismatch repair and program death ligand 1 (PD-L1) expression evaluation. In addition, 20 gastric cancer (GC) patients were recruited as the second validation cohort.ResultsIn the first cohort of 73 GI cancer patients, a lower burden of CNA was observed in patients with durable clinical benefit (DCB). In both the discovery (n=44) and validation (n=29) subsets, lower burden of CNA was associated with an improved clinical benefit and better overall survival (OS). Efficacy also correlated with a higher TMB. Of note, a combinatorial biomarker of TMB and CNA may better stratify DCB patients from ICB treatment, which was further confirmed in the second validation cohort of 20 GC patients. Finally, patients with lower burden of CNA revealed increased immune signatures in our cohort and The Cancer Genome Atlas data sets as well.ConclusionsOur results suggest that the burden of CNA may have superior predictive value compared with other signatures, including PD-L1, MSI and TMB. The joint biomarker of CNA burden and TMB may better stratify DCB patients, thereby providing a rational choice for GI patients treated with ICBs.

Immunotherapy has emerged as an effective therapeutic strategy for various cancers, including colorectal cancer (CRC), but only a subset of MSI-H patients can benefit from such therapy. Patched1 (PTCH1) is a frequently altered gene in CRCs and its mutations contribute to unregulated Hedgehog (Hh) signaling. In the study, we evaluated the association of PTCH1 mutations with CRC immunity based on our single-center cohort and multiple cancer genomic datasets. Among 21 enrolled patients, six (28.6%) harbored a PTCH1 mutation based on WES analyses. In CRC patients, the PTCH1 mutation subgroup experienced a higher durable clinical benefit rate than the PTCH1 wild-type subgroup (100% vs. 40%, P = 0.017). In addition, patients with the PTCH1 mutation experienced greater progression-free survival (PFS, P = 0.037; HR, 0.208) and overall survival (OS, P = 0.045; HR, 0.185). A validation cohort from the MSKCC also confirmed the correlation between PTCH1 mutation and better prognosis (P = 0.022; HR, 0.290). Mechanically, diverse antitumor immune signatures were more highly enriched in PTCH1-mutated tumors than in PTCH1 wild-type tumors. Furthermore, PTCH1-mutated tumors had higher proportions of CD8 + T cells, activated NK cells, and M1 type macrophage infiltration, as well as elevated gene signatures of several steps in the cancer-immunity cycle. Notably, the PTCH1 mutation was correlated with tumor mutational burden (TMB), loss of heterozygosity score, and copy number variation burden. Our results show that the mutation of PTCH1 is a potential biomarker for predicting the response of CRC patients to immunotherapy.

For most colorectal cancer patients with initial lung metastasis (LM), the only suitable treatments are palliative, including palliative local therapy and pharmacotherapy. We investigated the role of palliative local treatments in prolonging survival and the efficacy of different pharmacotherapies.After performing a medical record review of 2233 patients with metastatic colorectal cancer, 684 were identified as having LM. Their clinicopathologic characteristics, treatment patterns, and outcomes were analyzed retrospectively.For nonresectable initial LM, patients receiving palliative local therapy had significantly longer median progression-free survival (PFS) and overall survival (OS) than those treated with pharmacotherapy alone: PFS 16.1 months versus 7.4 months (P .001) and OS 51.8 months versus 23.8 months (P .001), respectively. Cox multivariate analysis confirmed the survival benefit induced by palliative local therapy. Chemonaive patients receiving single-agent fluoropyrimidine had shorter PFS and longer OS compared to oxaliplatin- or irinotecan-based doublets when used as first-line treatment (PFS 4.8, 7.4, and 7.3 months; and OS 28.7, 21.2, and 20.1 months, respectively); however, these differences were not statistically significant. The addition of targeted agents to cytotoxic drugs prolonged PFS (10.5 vs. 7.2 months, P = .005) but not OS (27.8 vs. 21.2 months, P = .454). Carcinoembryonic antigen level, LM-associated symptoms, extrapulmonary disease, and histopathologic type were independent pretreatment prognostic factors.Local treatments of LM may confer a survival benefit in the palliative setting. First-line single-agent fluoropyrimidine may be used in patients with good prognosis.

301 Background: HER2 overexpression has proven to be an effective treatment target in several malignancies. Trastuzumab plus chemotherapy showed favorable clinical efficacy and safety in HER2-positive gastric cancer and breast cancers. In this study, we aimed to evaluate the antitumor activity of trastuzumab plus irinotecan in pretreated patients with HER2-postive unresectable metastatic CRC and explore biomarkers for response and resistance to this treatment. Methods: mCRC patients with confirmed HER2 positivity (defined as IHC3+ or IHC2+/FISH+ on archival tissue) and wild-type RAS gene that progressed after ≥ 1 prior systemic treatment were enrolled in this phase II clinical trial. Patients received trastuzumab (6mg/kg q3w) plus irinotecan (120mg/m2, d1,8 q3w) for the first six cycles and trastuzumab (6mg/kg q3w) as maintenance treatment sequentially. Primary end point is objective response rate (ORR) and secondary endpoints are progression-free survival (PFS) and safety. Pretreatment tumor tissue, plasma at baseline and after disease progression were collected and analysed using a customized NGS panel covering 733 cancer-related genes in a CAP/CLIA-approved laboratory (3DMed). Results: Between June 2019 and December 2020, 21 HER2 positive patients were enrolled, with median age 55(30-67). At data cutoff (August 1, 2021), six (28.6%) of 21 patients achieved a partial response, and 12 (57.1%) patients had stable disease. The median progression-free survival was 4.3 months (95% CI, 2.65 to 5.95 months). Treatment-related adverse events of grade 3 or 4 occurred in 9.5% of patients, with the most common being neutropenia. No treatment-related death was reported. HER2 3+ expression and higher tumor tissue HER2 copy number were associated with durable response (p for PFS = 0.09 and 0.019, respectively). Two patients with KRAS amplification and one patient with BRAF amplification and fusion mutation at baseline all experienced primary resistance. In the after-progression plasma samples, heterogeneous and complicated genomic alterations potentially contribute to the acquired resistance were observed, with RAS/MAPK pathway (n = 4), cyclin/CDK-RB-E2F pathway (n = 4), PI3K/AKT/mTOR pathway (n = 3), and HER2 gene (n = 1) involved. Intriguingly, except for the SNV, copy number variation and gene fusion may represent an important resistance mechanism of HER2 targeted therapy. Conclusions: Trastuzumab plus irinotecan showed promising efficacy and well tolerated safety profile in HER2-positive mCRC. This combination therapy might present a feasible option for patients with HER2-positive unresectable metastatic colorectal adenocarcinoma. ctDNA sequencing provides novel insights into genomic alteration underlying HER2 targeted therapy in HER2-positive mCRC. Clinical trial information: NCT03185988.