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PURPOSE Immune checkpoint inhibitors (ICIs) have significantly improved outcomes in various malignancies. However, the high cost of these therapies limits access for much of the global population. This systematic review aims to evaluate the efficacy of low-dose ICIs compared with standard doses in different malignancies, addressing financial and access barriers in global cancer care. METHODS We conducted a systematic review of studies comparing the efficacy of low-dose versus standard-dose ICI regimens in advanced solid tumors. A comprehensive search was performed across multiple electronic databases, including retrospective and prospective studies. Excluded were animal studies, editorials, conference papers, book chapters, and other immunotherapy modalities. Outcomes assessed included overall survival (OS), progression-free survival, and objective response rate. Results were summarized descriptively due to study heterogeneity. RESULTS From 1,010 screened articles, four studies with 435 Asian patients were included, covering a variety of solid tumors. All included studies were with a low quality of evidence and a high risk of bias due to retrospective design. Two studies used weight-based dosing (pembrolizumab <2 mg/kg and nivolumab <2.15 mg/kg), showing similar OS to standard dosing in non–small cell lung cancer (NSCLC) and renal cell carcinoma, respectively. Flat dose regimens in two studies (nivolumab 20 mg or 100 mg once every 3 weeks and pembrolizumab 100 mg once every 3 weeks) also demonstrated comparable OS in NSCLC. CONCLUSION Low-dose ICIs may offer equivalent clinical benefits to standard dosing, potentially reducing costs and expanding access in developing countries. Although awaiting more representative randomized clinical trials, weight-based ICI regimens could be a viable alternative in low- and middle-income countries.

Abstract Biliary tract cancer (BTC) remains among the most challenging malignancies with a poor prognosis and limited treatment options, particularly in pretreated patients. As most patients experience disease progression after first-line treatment, effective second-line and subsequent treatments are required. Although the addition of modified FOLFOX (fluorouracil, leucovorin, and oxaliplatin) to active symptom control improved the overall survival of patients with progressing advanced BTC despite gemcitabine plus cisplatin treatment, its efficacy was modest. Moreover, most clinical trials demonstrated modest efficacy of molecular-targeted agents for molecularly unselected pretreated advanced BTC. Patients with advanced BTC carry a relatively high druggable genetic alteration rate and have shown promising responses to molecular-matched therapies targeting gene alterations such as FGFR2 fusions/rearrangements, IDH1 mutation, and HER2 overexpression/amplification. Additionally, tumor-agnostic approaches, including BRAF V600E, NTRK fusion, and RET fusion, have expanded the treatment options for some patients. Immune checkpoint inhibitors have shown limited efficacy as mono- or combination therapy in patients with pretreated advanced BTC. Therefore, developmental efforts have shifted to immune checkpoint inhibitor and other combinations such as vascular endothelial growth factor receptor inhibitors or radiation. In addition to refining combination strategies to enhance the therapeutic potential of immune checkpoint inhibitor, future research should focus on elucidating the tumor microenvironment. This review delineates the evolution of systemic therapies in patients with pretreated advanced BTC. By examining past developments and recent advances through prospective trials, it highlights novel approaches that may improve outcomes in this challenging disease.

Background: Regorafenib (R) and Trifluridine/Tipiracil ± bevacizumab (T) are approved for treating refractory metastatic colorectal cancer (mCRC) but their optimal sequence is unclear. This study describes the characteristics/clinical outcomes of patients with mCRC in U.S. clinical practice treated sequentially with R-T or T-R. Methods: A retrospective cohort study of 818 patients treated with R-T or T-R between January 2015 and November 2022 was conducted using an electronic health record-derived database. The primary objective was to describe the demographic/clinical characteristics and biomarker status of patients treated with R-T or T-R, stratified by treatment line/age. Secondary objectives were to evaluate/estimate the frequency of neutropenia and myelosuppression-related treatments, the number/type of subsequent therapies, time to treatment discontinuation (TTD), and overall survival (OS). Results: Baseline characteristics were similar among patients who received R-T (n = 393) or T-R (n = 425). Lower rates of moderate/severe neutropenia (26%/12% vs. 32%/16%) and granulocyte colony-stimulating factor/erythropoietin use (22% vs. 24%) were observed with R-T versus T-R. The median TTD was 8.7 months and 8.5 months with R-T versus 8.1 months and 7.9 months with T-R as third- and fourth-line treatment, respectively. The median OS was 13.1 months and 11.6 months with R-T versus 11.5 months and 10.3 months with T-R as third- and fourth-line treatment, respectively. Conclusions: This study did not show a statistically significant difference in OS with R-T versus T-R. Although limited by its retrospective nature, the study suggested R-T may be preferable to T-R given the observed reduction in neutropenia/myelosuppression-related treatments.

In a retrospective study of patients with Lynch syndrome vs non‐Lynch syndrome and microsatellite instability high colorectal cancer, there were no observed differences with immune checkpoint inhibitors toward progression‐free survival or overall survival. Univariate analysis of Stage IV patients showed BRAF V600E mutations were associated with decreased survival.

206 Background: XTX101 is an investigational tumor-activated, Fc-enhanced, high affinity binding aCTLA-4 designed to block CTLA-4 and deplete regulatory T cells upon activation in the tumor by proteases. XTX101 also contains mutations designed to enhance Fcγ receptor binding. Fc enhancement augments FcγR co-engagement on antigen presenting cells and has been linked with efficacy of aCTLA-4 combinations in patients (pts) with “cold tumors”, including microsatellite stable (MSS) colorectal cancer (CRC). Parts 1A/1B of the study evaluated XTX101 monotherapy in pts with advanced solid tumors. XTX101 was generally well tolerated with limited peripheral XTX101 activation (~13%) compared to evidence of XTX101 activation in the tumor microenvironment (73-96%, in n=2 on-treatment tumor biopsies). A durable partial response (PR) and resolution of hepatic metastases was observed in a pt with PD-L1 negative NSCLC at the monotherapy recommended phase 2 dose (RP2D) of 150 mg once every six weeks (Q6W) [1]. Methods: Part 1C evaluated the safety and feasibility of XTX101 in combination with atezolizumab in pts with advanced solid tumors using 3+3 dose escalation to establish the RP2D. Phase 2 is enrolling pts with MSS CRC with at least 1 prior regimen for metastatic CRC. Initial safety and anti-tumor activity data from Phase 2 in ~20 pts will be presented. Results: As of July 15, 2024, 15 pts were enrolled in Part 1C: MSS CRC (n=12), esophageal cancer, NSCLC, and ampullary carcinoma (n=1 each). Median age 69 and 3 prior lines of therapy (1-12). Across all XTX101 dose levels (75 mg to 150 mg), treatment-related adverse events (TRAEs) of any grade with >10% incidence included infusion reactions (n=4), fatigue and diarrhea (n=2 each), no G4 or G5 TRAEs were reported. In Part 1C, 2 pts experienced a dose limiting toxicity: 1 pt had G3 colitis, and 1 pt had G3 liver enzyme elevation (both were at the XTX101 150 mg dose level and resolved with immunosuppression). Two unconfirmed PRs were reported: in a pt with MSS CRC, including resolution of a liver target lesion, and in a pt with ampullary carcinoma (accompanied by a Ca 19-9 decrease from 700 to 41). In addition, a decrease in intra-tumoral Tregs was observed in paired tumor biopsies from a pt. The combination RP2D was established as XTX101 100 mg Q6W and atezolizumab 1200 mg once every three weeks (Q3W), and enrollment in the Phase 2 part of the study for pts with MSS CRC is ongoing at the RP2D. Conclusions: In Part 1C dose escalation, the combination of XTX101, a tumor-activated, Fc-enhanced aCTLA-4, and atezolizumab was generally well tolerated in pts with advanced solid tumors and demonstrated initial evidence of anti-tumor activity in cold tumors. These data support the initiation of an ongoing Phase 2 study evaluating the combination in pts with MSS CRC with and without liver metastases. 1. Davar ESMO IO 2023. Clinical trial information: NCT04896697 .

243 Background: HER2-amplified aCRC is associated with poor prognosis despite new anti-HER2 regimens. Insight on biomarkers that predict response to these therapies is limited. This study aims to evaluate whether baseline alterations in oncogenic drivers along the HER2 pathway predict response to anti-HER2 therapy in HER2-amplified aCRC. Methods: In this international multi-center study involving Mayo Clinic, Duke Cancer Institute and National Cancer Center Hospital East (Japan), we collected baseline genomic alterations from tissue or blood samples using next-generation sequencing (NGS) prior to anti-HER2 therapy initiation. We defined PIK3CA, RAS, RAF, MAP2K, and MET as oncogenic drivers of resistance within the HER2 pathway. Overall survival (OS) was evaluated with the Kaplan-Meier method and a log-rank test was used to compare median OS (mOS) between pts with and without alterations in the above genes. A chi-square test (significance level 0.05) was performed to compare overall response rate (ORR) and disease control rate (DCR). Results: We identified 39 pts with HER2-amplified aCRC and baseline NGS. Median age was 57 (range 30-77), 54% were male. Baseline alterations in HER2 pathway oncogenic drivers were identified in 17 pts (43.5%). 18 (46%) received monoclonal antibodies (mAbs) plus tyrosine kinase inhibitors, 12 (30%) received dual mAbs and 7 (18%) received trastuzumab deruxtecan. The mOS was 41.9 months (mos) (95%CI 23.7-60.1) for other alterations vs 24.2 mos (95%CI 14.1-34.3) in pts with HER2 pathway alterations (p = 0.1). ORR was 47% vs 41% (p = 0.7) and DCR 82% vs 73% (p = 0.4), for pts with HER2 pathway alterations and without HER2 pathway alterations, respectively. 4 pts receiving trastuzumab/tucatinib had complete response, none of which had HER2 pathway alterations. Conclusions: Pts with baseline alterations in oncogenic drivers of the HER2 pathway had clinically worse outcomes compared to pts without such alterations despite receiving HER2-targeted therapy, though results lacked statistical significance. Larger studies are needed to confirm the lack of benefit from anti-HER2 therapy in this subgroup.