Citations

Objectives: For locally advanced rectal adenocarcinoma (R-ACA), a nonoperative management (NOM) approach has emerged as a guideline-supported treatment option. However, the variables associated with NOM receipt are unknown. Methods: Utilizing the National Cancer Database, we performed a retrospective cohort study of adults with stage 1 to 3 R-ACA managed with curative intent from 2004 to 2018. The primary outcome was the proportion of patients receiving NOM versus surgery. The secondary outcome was survival among NOM patients. Results: A total of 128,297 patients were included. In all, 115,888 (90.3%) received surgery and 12,409 (9.7%) received NOM. Receipt of NOM was associated with age above 70, Charlson-Deyo score of 0, race (Black, Asian or Pacific Islander, or other vs. White), insurance status, geographical region, treatment in a community facility, year of diagnosis (2012-2018 vs. 2004-2011), tumor grade 1 versus ≥ 2, clinical T-stage ≥ 2, and clinical N1 or N2 versus N0. In the NOM cohort, poorer overall survival was associated with age 70 and above, male sex, Charlson-Deyo score ≥ 1, insurance status, geographical region, rural urban density versus metro/urban, treatment in a community facility, year of diagnosis (2004-2011 vs. 2012-2018), clinical T4 versus T1, clinical N1 or N2 versus N0, grade 3 versus 1, treatment with a radiotherapy dose <45 Gy versus 45 to 54 Gy, and omission of chemotherapy. Conclusions: Several demographic factors and social determinants of health were associated with receipt of NOM and overall survival. With the increasing utilization of NOM, it will be important to understand the drivers of treatment decisions and influences on access to the desired treatment approach.

3553 Background: Vilastobart (XTX101) is tumor-activated, high affinity, Fc-enhanced aCTLA-4 designed to focus activity toward the tumor and minimize systemic adverse events. Fc-enhancement augments FcγR co-engagement on antigen presenting cells and has been linked with efficacy of aCTLA-4 combinations in patients (pts) with microsatellite stable (MSS) colorectal cancer (CRC) and other tumors [Fakih ASCO GI 2025]. Vilastobart was generally well-tolerated and demonstrated evidence of anti-tumor activity in pts with immunologically “cold” advanced solid tumors, both as a monotherapy and in combination with atezolizumab [Davar SITC 2024]. Methods: Phase 2 of the NCT04896697 study evaluated the initial recommended Phase 2 dose of vilastobart 100 mg Q6W in combination with atezolizumab 1200 mg Q3W in pts with MSS CRC who had at least 1 prior chemotherapy regimen in the metastatic setting, excluding pts with prior immune checkpoint inhibitors. Pts with (LM) and without liver metastasis (NLM) were eligible. Tumor biopsies were obtained before and during treatment for translational analyses. Results: As of January 13, 2025, 40 pts were dosed in Phase 2. Median age was 55 (25-82) and 70% of pts had 3 or more prior lines of therapy. Of the 24 enrolled NLM pts, 11 were response-evaluable with an available on-treatment scan as of the data cut. In these 11 pts, two confirmed and one unconfirmed partial response (PR) were reported, all accompanied by significant decreases in ctDNA and serum tumor marker CEA and with each pt ongoing on therapy, for a preliminary ORR of 27%. One additional pt (with peritoneal metastasis) had a 24% reduction in target lesions (first scan) and was ongoing on therapy. Of the 16 enrolled LM pts, 7 were response evaluable, with one stable disease and another pt reporting a mixed response with significant serum tumor marker reductions, both ongoing on therapy. Of note, one LM pt in Phase 1C dose escalation treated with vilastobart (150 mg Q6W) combination had a confirmed PR with LM resolution. Six pts (15%) reported G3+ treatment-related adverse events (TRAEs), with two G4 laboratory TRAEs and no G5 TRAEs. Only three pts discontinued therapy for TRAEs. TRAEs occurring in ≥10% (all grade) or ≥5% (G3) of pts are summarized in the Table. Conclusions: The combination of vilastobart, a novel tumor-activated, Fc-enhanced a-CTLA-4, and atezolizumab demonstrated initial evidence of anti-tumor activity in late line, metastatic MSS CRC where immune checkpoint blockade has historically been relatively ineffective. Vilastobart was observed to have a differentiated safety profile distinct from systemically active a-CTLA-4, consistent with tumor-selective activation. Clinical trial information: NCT04896697 . AE term All Graden (%) Grade 3n (%) Fatigue 12 (30%) 0 Diarrhea 8 (20%) 0 Infusion related reactions 5 (13%) 0 Pyrexia 4 (10%) 0 ALT increased 4 (10%) 0 AST increased 4 (10%) 1 (3%) Colitis 2 (5%) 2 (5%)

Abstract Background: Leukocyte immunoglobulin-like receptor B2 (LILRB2) suppresses immune cell activation, particularly within myeloid cells in the tumor microenvironment (TME), while the PD-1/PD-L1 axis serves as a key immune checkpoint that inhibits T-cell function. SPX-303 is a novel bispecific antibody designed to simultaneously block LILRB2 and PD-L1, thereby revitalizing antitumor immune responses. Here, we present initial findings from the ongoing first-in-human Phase 1 trial of SPX-303 in patients with advanced solid tumors, including safety, pharmacokinetics (PK), and receptor occupancy (RO). Methods: This is an open-label, multicenter Phase 1 study for patients with advanced solid malignancies with 3+3 dose-escalation design, followed by an expansion cohort at the recommended Phase 2 dose (RP2D). SPX-303 is administered intravenously every three weeks and safety is assessed through CTCAE v5.0 criteria. Primary Objectives of this study are to determine the safety, tolerability, and RP2D of SPX-303. Secondary endpoints include antitumor activity as well as characterization of the PK and PD of SPX-303. This study is currently open and enrolling in escalation cohorts. Citation Format: Justin Moser, Hao Xie, Yujie Zhao, Yousef Zakharia, Dongdong Li, Brandon William, Dinh-Duc Nguyen, Jack Hovey, Tiffany Li, Robert Cai, Jichun Ma, Jingdong Qin, Martin Siekierzycki, Anthony Haight, Hua Jin, Weiwei Mao, Kevin Bin Li, Gui-Dong Zhu. A first-in-human phase 1 study on the safety, PK, receptor occupancy, and pharmacodynamic markers of SPX-303, a first-in-class LILRB2×PD-L1 bispecific antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr CT116.

ImportanceImmune checkpoint inhibitors (ICIs) have been approved for treatment of microsatellite instable (MSI-H) metastatic colorectal cancer (mCRC), but factors associated with receipt and efficacy of ICIs in routine clinical practice remain largely unknown.ObjectiveTo identify factors associated with receipt of ICIs and associated survival outcomes among patients with mCRC in routine clinical practice.Design, Setting, and ParticipantsThis population-based cohort study used deidentified data from a nationwide electronic health record–derived database to include 18 932 patients diagnosed with mCRC between January 2013 and June 2019. Population-based patients were diagnosed with de novo mCRC and had at least 2 documented clinical visits on or after the date of diagnosis. The study analyses were performed between September 2020 and April 2021.ExposurePatients received ICI therapy and/or chemotherapy as part of a systemic treatment for mCRC.Main Outcomes and MeasuresThe outcomes were receipt of ICI therapy, overall survival (OS), and time to treatment discontinuation (TTD).ResultsIn this cohort study of 18 932 patients diagnosed with mCRC (10 537 [55.7%] male; 546 [2.9%] Asian, 2005 [10.6%] Black or African American, 1674 [8.8%] Hispanic, 12 338 [65.2%] White, 4043 [21.4%] unknown race or ethnicity; median [IQR] age at metastatic diagnosis, 64.6 [55.0-73.3] years), patients with MSI-H tumors had a significantly higher probability of receiving ICIs than those with microsatellite stable (MSS) tumors (odds ratio [OR], 22.66 [95% CI, 17.30-29.73]; P &amp;lt; .001), whereas patients initially diagnosed with synchronous mCRC had significantly lower odds of receiving ICIs than patients with metachronous mCRC (OR, 0.57 [95% CI, 0.45-0.73]; P &amp;lt; .001). Patients with MSI-H tumors who received ICIs as first line of therapy had significantly longer OS than those receiving chemotherapy only (HR, 0.37 [95% CI, 0.25-0.56]; P &amp;lt; .001). Among patients with MSS tumors, ICI-based therapy was associated with significantly longer OS for patients with high albumin level (vs low: HR, 0.28 [95% CI, 0.18-0.45]; P &amp;lt; .001) and antibiotic use (vs nonuse: HR, 0.43 [95% CI, 0.27-0.67]; P &amp;lt; .001), but a significantly shorter OS for patients with synchronous mCRC (vs metachronous: HR, 1.90 [95% CI, 1.24-2.89]; P = .003). In addition, 29 out of 235 patients with MSS tumors (12.3%) experienced durable responses on ICI-based therapy. Similar patterns of associations with TTD were observed.Conclusions and RelevanceIn this cohort study of patients with mCRC, clinical characteristics were associated with different survival outcomes in patients treated with ICI-based therapy, with important clinical implications for patients with MSS tumors who are generally unresponsive to immunotherapy.

Thrombospondin-2 (THBS2) is a prevailing prognostic biomarker implicated in different cancer types, such as deadly colorectal, pancreas, and triple-negative breast cancers. While the current methods for cancer-relevant protein detection, such as enzyme-linked immunosorbent assay (ELISA), mass spectrometry, and immunohistochemistry, are feasible at advanced stages, they have shortcomings in sensitivity, specificity, and accessibility, particularly at low concentrations in complex biological fluids for early detection. Here, we propose and demonstrate a modular, in-solution assay design concept, Nanoparticle-Supported Rapid Electronic Detection (NasRED), as a versatile cancer screening and diagnostic platform. NasRED utilizes antibody-functionalized gold nanoparticles (AuNPs) to capture target proteins from a minute amount of sample (<10 µL) and achieve optimal performance with a short assay time by introducing active fluidic forces that act to promote biochemical reaction and accelerate signal transduction. This rapid (15 min) process serves to form AuNP clusters upon THBS2 binding and subsequently precipitate such clusters, resulting in color modulation of the test tubes that is dependent on the THBS2 concentration. Finally, a semiconductor-based, portable electronic device is used to digitize the optical signals for the sensitive detection of THBS2. High sensitivity (femtomolar level) and a large dynamic range (five orders of magnitude) are obtained to analyze THBS2 spiked in PBS, serum, whole blood, saliva, cerebrospinal fluids, and synovial fluids. High specificity is also preserved in differentiating THBS2 from other markers such as cancer antigen (CA) 19-9 and bovine serum albumin (BSA). This study highlights NasRED’s potential to enhance cancer prognosis and screening by offering a cost-effective, accessible, and minimally invasive solution.

Abstract Purpose: KRAS G12C inhibitors can treat KRASG12C-mutant advanced colorectal cancers and pancreatic ductal adenocarcinomas (PDAC), but alterations in Kirsten rat sarcoma (KRAS), EGFR, BRAF, MAP2K1, and other genes bypass KRAS inhibition and reduce therapy efficacy. Our study evaluates the genetic landscape of candidate primary resistance alterations relevant to KRAS targeting in KRASG12C-mutant colorectal cancer and PDAC. Experimental Design: We analyzed two cohorts (national database and Mayo) of patients with advanced colorectal cancer or PDAC tested with next-generation sequencing of ctDNA via Guardant360. Cohorts were divided into three groups: KRASG12C alone (KRASG12C without a resistance gene), KRASG12C with resistance (KRASG12C and ≥1 candidate resistance gene), and KRAS not detected. Candidate resistance mutations were inferred from the reported literature. Results: Among the national (13,603 colorectal cancer and 5,016 PDAC cases) and Mayo (741 colorectal cancer and 422 PDAC cases) cohorts, resistance alterations were identified in a considerable number of KRASG12C cases (46.5% of national colorectal cancer, 16.4% of national PDAC, 53.8% of Mayo colorectal cancer, and 36.4% of Mayo PDAC). The presence of resistance alterations was associated with a trend toward worse overall survival in KRASG12C colorectal cancer (P = 0.05). Conclusions: Putative resistance alterations are prevalent in PDAC and colorectal cancer and may limit monotherapy efficacy. Identifying these alterations has potential implications in optimal patient selection for targeted therapies and the development of combination therapy strategies to overcome primary resistance.

3078 Background: Q901 is a potent, covalently binding CDK7 inhibitor with excellent specificity for CDK7 against other protein kinases. Transcriptional regulation by CDK7 inhibition in cancer cells leads to DNA damage repair response inhibition and increased genomic instability. Q901 also regulates cell cycle checkpoints by inhibiting T-loop phosphorylation and transcriptionally downregulating CDK1, 2 and 4. In preclinical in vivo models, intravenous (iv) administration of Q901 once a week and once every three-week dosing regimen was well tolerated and showed significant antitumor activity. The safety profile, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy data for 18, 36 and 60 mg/m2 are presented. Methods: QRNT-009 (NCT05394103) is an ongoing Phase 1/2 multicenter, open-label, dose escalation and expansion study. Q901 is administered iv once weekly for four weeks, then once every two weeks thereafter in patients with advanced or metastatic ovarian cancer, castration-resistant prostate cancer (CRPC), breast cancer, endometrial cancer, colorectal cancer, small cell lung cancer (SCLC), or pancreatic cancers. Results: As of data cutoff (12Jan2024), 17 patients received Q901 across 3 dose levels: 5 patients at 18 mg/m2, 4 patients at 36 mg/m2, and 8 patients at 60 mg/m2. The median prior lines of systemic therapy were 4 (range 2 - 17). Of 17 patients who received Q901 across all doses, there were no treatment related SAEs, treatment discontinuations, or dose reductions. Most common TRAEs ≥ 15% were nausea (29.4%), anemia (23.6%) and fatigue (23.5%). As of data cutoff, no DLTs were observed. All plasma PK analyses across dose levels showed dose dependent increase of AUC0-last and Cmax. No major metabolite was observed. POLR2A, which is a CDK7 target engagement marker showed biologically effective change starting from 18 mg/m2. 1 patient with pancreatic cancer who received 18 mg/m2 had a partial response with CA19-9 reduction from 4,632 to 219. 2 patients at 18 mg/m2 and 2 patients at 36 mg/m2 had stable disease. Additional safety and efficacy data will be presented. Conclusions: Preliminary data from QRNT-009 study showed that selective CDK7 inhibitor Q901 is well tolerated. Preliminary antitumor activity and pharmacodynamic observations are encouraging. Dose escalation is ongoing to identify MTD or recommended dose for further studies. Clinical trial information: NCT05394103 .

3519 Background: KRAS G12D commonly occurs in pancreatic (PDAC) and colorectal (CRC) cancers. Though developing KRAS G12D inhibitors is pertinent, it is expected that primary and acquired resistance will limit efficacy, similar to those seen with KRAS G12C inhibitors. Here, we assessed the prevalence and outcomes of candidate mutations co-occurring with KRAS G12D in PDAC and CRC using liquid biopsy data. Methods: Patients with advanced CRC and PDAC tested with Guardant360 genomic profiling from 2020 to 2023 (~2500 & 3500 samples) were included. Candidate resistance mutations were determined based on mutations reported following KRAS G12C inhibition. Patients with advanced CRC and PDAC tested with Guardant360 at Mayo Clinic (2016-2023) (1158 & 904 samples) were assessed for overall survival (OS). Patients were divided into three groups: KRAS G12D alone, KRAS G12D with candidate resistance alterations, and KRAS G12D not detected (ND). OS was estimated using Kaplan-Meier method. Cox regression was used for multivariable survival analyses. Results: The Guardant360 database reported KRAS G12D in 16.5% of CRC and 40.2% of PDAC samples. The Table below summarizes the most frequent candidate resistance alterations co-occurring with KRAS G12Dincluding point mutations of KRASand PIK3CAand amplifications of EGFR, KRAS, BRAFand MYC. In the Mayo cohort, 8.9% of CRC and 23.5% of PDAC patients had KRAS G12D. In CRC, those with KRAS G12Dand ≥1 candidate resistance alteration had a significantly lower OS (mOS 18.7m) than KRAS G12D alone (30.9m), and ND (37.3m) ( p=0.004). The presence of concurrent candidate resistance alterations with KRAS G12D remained a poor prognostic factor with HR 2.1 (95% CI: 1.3 – 3.2, p=0.001) after adjusting for age and other patient characteristics. Similarly, in PDAC, those with KRAS G12D and ≥1 resistance mutation had significantly lower OS (mOS 8.1m) than KRAS G12D alone (10.5m) and ND (16.1m) (p<0.0001). In multivariable analyses, both KRAS G12D with candidate resistance alterations (HR 2.1, 95% CI: 1.4-3.3, p<0.001) and G12Dalone (HR 1.6; 1.3–2.0, p<0.001) were poor prognostic factors. Among patients with serial Guardant360, treatment response trended with KRAS G12D variant allele frequency. Conclusions: Circulating tumor DNA testing is a useful tool to reveal candidate molecular alterations linked to potential resistance to KRAS G12D targeting in patients with KRAS G12D gastrointestinal cancers. KRAS G12D with these concurrent molecular alterations is a poor prognostic factor in both PDAC and CRC. [Table: see text]

Abstract Background: It is a common practice to monitor trastuzumab-related cardiac toxicity (TRCT) using left ventricular ejection fraction (LVEF) in patients who receive trastuzumab-containing therapy for human epidermal growth factor receptor 2 (HER2)-positive cancers. However, this monitoring approach does not appear cost effective in patients with HER2-positive gastrointestinal (GI) cancers given poor overall survival (OS). Here, we aim to examine the incidence of clinically significant TRCT in this target population. Methods: This is a retrospective cohort study of patients with advanced HER2-positive GI cancers who received trastuzumab-containing therapies (trastuzumab +/- pertuzumab, chemotherapy +/- immunotherapy + trastuzumab, trastuzumab deruxtecan) between 2011 and 2023. HER2 status was determined by immunohistochemistry, fluorescent in situ hybridization, and/or next generation sequencing. LVEF was estimated by serial transthoracic echocardiograms (TTE). Continuous variables were summarized as median and interquartile range (IQR). Paired Wilcoxon signed rank test was used to compare serial LVEF. OS was estimated using Kaplan-Meier method. Results: A total of 243 patients were included in this study with a median age of 64 (IQR: 55-70) years. 139 (57%) patients had esophageal or GEJ adenocarcinoma; 45 (19%) patients had gastric cancer; 37 (15%) patients had colorectal cancer; and the rest had other GI cancers. Median follow-up time was 18.6 (IQR: 9.2-36) months. Median OS from cancer diagnosis and the first dose of trastuzumab-containing therapy were 24.1 (95%CI: 20.2-30.2) and 11.7 (95%CI: 10.4-15.6) months, respectively. Patients received a median of 13 cycles of trastuzumab-containing therapy for a median duration of 4.1 (IQR: 1.4-10.1) months. The median number of TTE each patient had throughout therapy was 2 (IQR: 1-4). Median baseline LVEF was 61% (IQR: 56-65%) which was significantly higher (p&lt;0.001) than the median lowest LVEF of 58% (IQR: 53-62%) during therapy, but not different (p=0.14) from the most recent median LVEF of 60% (IQR: 56-64%) after discontinuation of trastuzumab. Among 176 patients with serial LVEF data, 16 (9%) had &gt; 10% LVEF drop; 7 (44%) of these 16 patients had LVEF recovery. None of the cardiovascular risk factors prior to trastuzumab treatment including hypertension, diabetes, hyperlipidemia, peripheral arterial disease, coronary artery disease, and stroke were significantly associated with the development of TRCT. Conclusion: The incidence of clinically significant LVEF drop appears low in patients with advanced GI cancers as post-treatment LVEF recovery to baseline was observed at the population level. The value of using TTE to monitor TRCT in these patients with short OS should be further assessed in the perspective of cost effectiveness. Citation Format: Samual R. Kosydar, Matteo Castrichini, Mojun Zhu, Hao Xie. The value of routine trastuzumab-related cardiac toxicity monitoring in gastrointestinal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6298.