Immune checkpoint inhibitors (ICIs) can cause a variety of immune-related adverse events (irAEs). The coronavirus disease 2019 (COVID-19) is associated with increased amounts of pro-inflammatory cytokines, which may affect the outcome of irAEs. Data are limited regarding the impact of COVID-19 on irAEs in ICI-treated cancer patients. Hence, in this study, we retrospectively analyzed ICI-treated adult patients with malignant solid tumors at a single institution between August 2020 and August 2021. Patients who had the most recent ICI treatment over 1-month before or after the positive COVID-19 test were excluded from the study. For the COVID-19 positive group, only the irAEs that developed after COVID-19 infection were considered as events. A total of 579 patients were included in our study, with 46 (7.9%) in the COVID-19 positive group and 533 (92.1%) in the COVID-19 negative group. The baseline characteristics of patients in the 2 groups were similar. With a median follow-up of 331 days (range: 21–2226), we noticed a nonsignificant higher incidence of all-grade irAEs in the COVID-19 positive group (30.4% vs. 19.9%, P =0.18). The incidence of grade 3 and 4 irAEs was significantly higher in the COVID-19 positive group (10.9% vs. 3.2%, P =0.02). Multivariate analysis confirmed the association between COVID-19 infection and increased risk of severe irAE development (odds ratio: 1.08, 95% confidence interval: 1.02–1.14, P =0.01). Our study suggested that COVID-19 may pose a risk of severe irAEs in cancer patients receiving ICIs. Close monitoring and possibly delaying ICI administration could be considered when cancer patients are infected with COVID-19.

Background Immune checkpoint inhibitors (ICIs) have shown modest antitumor activity in unselected advanced sarcomas. Histology driven approach to patient selection is the current standard for off-label anti-programmed cell death 1 (PD1) immunotherapy use. Methods We retrospectively reviewed the clinical characteristics and outcomes of patients with advanced sarcoma who were treated with off label anti-PD1 immunotherapy at our center. Results A total of 84 patients with 25 histological subtypes were included. Nineteen patients (23%) had a cutaneous primary tumor site. Eighteen patients (21%) were classified as having clinical benefit, including 1 patient with complete response, 14 with partial response, and 3 with stable disease lasting over 6 months with previously progressive disease. Cutaneous primary site location was associated with higher clinical benefit rate (58% vs. 11%, p < 0.001), longer median PFS (8.6 vs. 2.5 months, p = 0.003) and OS (19.0 vs. 9.2 months, p = 0.011), compared to non-cutaneous primary. Patients with histological subtypes that pembrolizumab is indicated per current National Comprehensive Cancer Network guidelines had modestly higher rate of clinical benefit versus other histologies, however, the difference was statistically insignificant (29% vs. 15%, p = 0.182) and no statistically significant difference in PFS or OS was observed between these groups. Immune-related adverse events were more frequently seen among patients with clinical benefit (72% vs. 35%, p = 0.007). Conclusions Anti-PD1-based immunotherapy is highly efficacious in advanced sarcomas of cutaneous primary site. Cutaneous primary site location is a stronger predictor of ICI response than histologic subtype and should be accounted for in treatment guidelines and clinical trial design.

228 Background: We previously conducted a phase I/Ib study with regorafenib and nivolumab in patients with refractory metastatic mismatch repair proficient (pMMR) colorectal cancer (CRC). This study aimed to investigate the biomarkers that predict the treatment response. Methods: Out of the 51 patients who received regorafenib and nivolumab, 22 archival pretreatment tumor samples were subjected to the Xerna TME Panel, a machine learning-based RNA-sequencing biomarker assay and were classified into one of four TME biomarker subtypes: Angiogenesis (A), Immune Active (IA), Immune Desert (ID), or Immune Suppressed (IS). Potential predictive biomarkers including the TME subtypes, KRAS (wild type vs mutant), PD-L1 (negative vs. positive, samples with > 1% tumor cells for PD-L1 were considered positive), CD8 expression (low vs. high), and Treg cells (low vs. high) in tumor microenvironment were evaluated for correlation with overall survival (OS), progression free survival (PFS) and disease control rate (DCR, defined as complete response + partial response + stable disease). Results: Among the 22 patients, 16 (72.7%) had liver metastasis and 15 (68.2%) had lung metastasis. KRAS mutation was found in 16 (68.2%) patients. 11/21 (52.4%) were positive for PD-L1. 12 (54.5%) had high CD8 expression, whereas 9/21 (42.9%) had high Treg cells in tumor microenvironment. Ten (45.5%) patients were classified as biomarker-positive (IA + IS subtypes) and 12 (54.5%) were biomarker-negative (A + ID) based on Xerna TME panel. Two (9.1%) patients achieved partial response, 12 (54.5%) had stable disease, and five (22.7%) developed progressive disease. The median PFS was 5.6 months and median OS was 13.1 months. No significant correlation was observed between RAS mutation (p = 0.664, p = 0.609), PD-L1 expression (p = 0.287, p = 0.173), CD8 (p = 0.152, p = 0.456) and PFS or OS. Low Treg was found to be associated with prolonged PFS (median: 9.8 vs. 1.9 months, p = 0.011) but not OS (p = 0.280). Similarly, only low Treg level was related with DCR (83.3% vs. 33.3%, p = 0.032). While not reaching statistical significance, Xerna TME biomarker-positive patients showed trends for higher median PFS (7.9 months vs. 4.1 months, p = 0.254), median OS (15.75 months vs. 11.9 months, p = 0.378), and higher DCR (70% vs. 58%, p = 0.675) compared to biomarker-negative patients. Additionally, the two patients with partial responses were Xerna TME biomarker-positive. Conclusions: Our study demonstrated that low Treg in tumor microenvironment is correlated with better prognosis in patients with refractory metastatic pMMR CRC who were treated with regorafenib plus nivolumab. Xerna TME panel analysis of these patients also showed trends for predictive clinical benefit. Prospective and larger cohort studies are needed to better define predictive biomarkers for this combination in the future.

188 Background: Our previous phase I/Ib study revealed modest clinical efficacy of rego/nivo in refractory MSS-CRC, implying benefits in selected populations. This has prompted us to investigate predictive biomarkers. Methods: Pre-treatment tumor samples from the previous phase Ib rego/nivo study were obtained and assessed for mRNA sequencing (RNAseq). Response-associated transcripts were identified using DESeq2 method and annotated using gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis. Results: A total of 19 pretreatment tumor samples were analyzed including 14 patients (pts) with disease control (DC) (2 partial response and 12 stable disease) and 5 pts with progression disease (PD). We observed significant upregulation of 89 genes including SFTPB ( P<0.001), SFTPA1 ( P<0.001), ERICH6B ( P<0.001) , XIST ( P<0.001), IGHV2-26 ( P<0.001), RETNLB ( P=0.005), VWA5B1 ( P=0.033), IGHV3-53 ( P<0.001), POTEH ( P=0.015), IGHV1-3 ( P=0.001) and downregulation of 70 genes including AFAP1-AS1 ( P=0.022), PRSS21( P<0.001), NTSR1 ( P<0.001), CALB1 ( P=0.033), FAM83A ( P=0.013), TBL1Y ( P=0.045), WNT7A ( P=0.022), PADI1 ( P<0.001), KRT6A ( P=0.030), KRT17 ( P=0.002) on RNA sequencing in the DC compared to PD. GO pathway enrichment analyses revealed 44 significantly upregulated pathways including positive regulation of B cell activation ( P<0.001), B cell receptor signaling pathway ( P<0.001), Phagocytosis engulfment ( P<0.001), Fc-gamma receptor signaling pathway involved in phagocytosis ( P<0.001), endocytosis ( P<0.001), immunoglobulin receptor binding ( P<0.001), serine-type endopeptidase activity ( P<0.001) in the DC compared with PD group. Nine downregulated pathways including cell-substrate junction assembly ( P<0.001), extracellular matrix (ECM) organization ( P=0.030), and ephrin receptor activity ( P=0.046) were observed in the DC compared with PD. KEGG pathway enrichment analysis revealed 8 significantly downregulated pathways including PI3K-Akt signaling ( P=0.009), ECM-receptor interaction ( P=0.006), Focal adhesion ( P=0.028), and Glycine, serine and threonine metabolism ( P=0.007) pathways in the DC compared with PD. Conclusions: RNAseq and following gene set enrichment analysis between pts with DC and PD revealed several dysregulated pathways involving immune regulation including macrophage and B cell activation, and also PI3-Akt signaling, ECM organization/receptor interaction, and adhesion, which are consistent with previous translational studies in other solid tumors. These dysregulated genes and pathways related to differentially expressed genes may need to be further evaluated as potential predictive biomarkers for rego/nivo or other tyrosine kinase inhibitor plus PD-1 blockade in MSS-CRC.