BACKGROUND:ICOS (inducible T-cell co-stimulator) and ICOS ligand (ICOSL) are part of an important, complex pathway that can lead to both immune stimulation and suppression. ICOS and ICOSL have heterogeneous expression patterns between and within tumor types. METHODS:This review provides an overview of ICOS and ICOSL, their mechanisms of action, expression in cancer and other diseases, and clinical trials exploring therapies targeting ICOS. RESULTS:Because of the bidirectional immune impact of the ICOS/ICOSL signaling pathway, both ICOS agonists and antagonists are under development and evaluation in clinical trials. The majority of clinical trials have focused on the development of ICOS agonists, with only one study exploring an ICOS antagonist; there have been no clinical trials developing ICOSL agonists or antagonists in oncology. ICOS can be expressed on immune-activating effector T-cell and immunosuppressive regulatory T-cell (Tregs). Thus, it is critical to determine where and how ICOS is expressed in order to evaluate the role for agonists versus antagonists. To date, ICOS agonists have shown limited activity in patients with malignancies, perhaps because of the lack of biomarker-based trials. However, an ICOS antagonist demonstrated a 44% response rate in angioimmunoblastic T-cell lymphoma; ICOS is highly expressed on T-follicular helper cells (type of CD4 cell) and proliferation of these cells may be a pathogenic mechanism for these lymphomas. A role for the ICOS/ICOSL signaling pathway has also been implicated outside of oncology, including in viral infections such as COVID-19, and in autoimmune conditions such as asthma and systemic lupus erythematosus. CONCLUSION:Biomarker-driven approaches will be important to individualize therapy and ascertain which cancer patients will derive the greatest benefit from ICOS-directed combination therapy approaches.

Supplementary Table S6 shows co-occurrence of actionable RNA expressions and corresponding protein expressions, and vice versa.

e14534 Background: Serum tumor markers are routinely monitored in patients with advanced solid tumors, but their utility in the phase I immunotherapy setting is not well established. We investigated whether baseline and best overall response (BOR) levels of these markers, and their changes during treatment, correlate with response and survival outcomes in patients on phase I immunotherapy trials across multiple tumor types. Methods: We retrospectively analyzed patients enrolled on phase I immunotherapy trials at our center between April 2017 and May 2023, with paired tumor marker assessments at baseline (within 30 days cycle 1 day 1 [C1D1]) and at BOR (within 21 days of BOR date, during which time patients received only study treatment). Markers analyzed included CA15-3 (breast), CA125 (ovarian), CA19-9 (pancreatic, cholangiocarcinoma, gastric/gastroesophageal junction [GEJ]), and CEA (colorectal, pancreatic, gastric/GEJ). In pancreatic cancer, CA19-9 was the primary analysis and CEA was exploratory. Associations between marker levels and BOR were assessed using Fisher's exact and Kruskal-Wallis tests. Spearman correlation evaluated relationships between marker percent change and radiographic response. Univariate Cox regression assessed associations with overall survival (OS), time to progression (TTP), and progression-free survival (PFS). Results: 106 patients with paired baseline and BOR marker data were included: colorectal (n = 35), pancreatic (n = 30), breast (n = 15), ovarian (n = 15), cholangiocarcinoma (n = 6), and gastric/GEJ (n = 5). Median age was 59 years; 61.3% were female; 74.5% received combination immunotherapy. In pancreatic cancer, CA19-9 levels at BOR were significantly higher in patients with progressive disease (PD) compared to stable disease (SD) or partial response (PR) (median 9,500 vs 535.4 vs 173.5 U/mL; p = 0.026). CA19-9 percent change from baseline to BOR positively correlated with radiographic response change (ρ = 0.44, p = 0.02). On Cox regression, CA19-9 percent change was associated with worse OS (HR 1.02 per 10% increase, 95% CI 1.00-1.04; p = 0.014), TTP (HR 1.02, p = 0.029), and PFS (HR 1.02, p = 0.029). In colorectal cancer, elevated CEA at BOR ( > 3.8 ng/mL) was associated with worse OS (HR 4.65, 95% CI 1.10-19.71; p = 0.037). Greater radiographic tumor burden change was associated with worse OS (HR 1.23 per 10% increase, p = 0.038), TTP (HR 1.34, p = 0.003), and PFS (HR 1.33, p = 0.003). Conclusions: Changes in tumor marker levels—particularly CA19-9 in pancreatic cancer and CEA in colorectal cancer—provide prognostic information in phase I immunotherapy trials, though concordance with radiographic change was modest. Given the challenges of early response assessment with immunotherapy, tumor markers may serve as a practical adjunct to imaging for longitudinal monitoring. Prospective validation and longitudinal trajectory analysis are warranted.

KPT-9274, a potentially first-in-class, dual NAMPT/PAK4 inhibitor, has shown single-agent anticancer activity in hematologic and solid tumor cell lines and xenografts. KPT-9274 has shown anti-tumor activity in combination with nivolumab in nonclinical models. KCP-9274-901 was a first-in-human, multi-center, open-label clinical study to assess preliminary safety, tolerability, and efficacy of KPT-9274 in patients with advanced solid tumors. This study was conducted in three parts. A two-part (A, B) dose escalation phase to determine the recommended phase II dose and maximum tolerated dose (MTD) of KPT-9274 alone and with niacin. Part 3 (C) was a dose-finding and expansion phase in patients with melanoma treated with KPT-9274 plus nivolumab. A total of 60 patients were enrolled (part A and B n = 50; part C n = 10). Three dose-limiting toxicities (DLTs) were observed in the 40-mg (n = 1) and 80-mg plus niacin (n = 2) cohorts. MTD was not reached in parts A and B and was 60 mg plus nivolumab in part C. The most frequently reported TEAEs (≥30 www.clinicaltrials.gov , NCT02702492.

BACKGROUND:Immunosuppression mechanisms mediated by regulatory T cells (Tregs) can lead to poor clinical outcomes in patients undergoing immune-based therapies. Activation markers, such as inducible T-cell co-stimulator (ICOS), are highly expressed on the surface of tumor-infiltrating Tregs and present as relevant targets for targeted depletion of these cells. Here, we present clinical outcomes from a Phase 1 study (NCT03829501) of an anti-ICOS antibody of alomfilimab (SAR445256 or KY1044) as monotherapy and in combination with the anti-programmed death-ligand 1 (PD-L1) antibody, atezolizumab, in patients with advanced solid tumors. METHODS:Alomfilimab was administered intravenously once every 3 weeks (Q3W) ±3 days at six dose levels (DLs; 0.8 mg to 240 mg) as monotherapy and five DLs (0.8 mg to 80 mg) in combination with atezolizumab (1,200 mg Q3W ±3 days). Eligible patients must have had advanced metastatic disease as determined by Response Evaluation Criteria in Solid Tumors V.1.1 and no viable treatment options according to National Comprehensive Cancer Network guidelines. RESULTS:Overall 38 patients were enrolled in the monotherapy cohort, and 102 patients were enrolled in the combination therapy cohort. Alomfilimab had a manageable safety profile and showed a trend toward modest efficacy in tumor growth control when combined with anti-PD-L1 in selected malignancies. At least one treatment-emergent adverse event was reported in 35 patients (89.7%) in the monotherapy cohort, and in 99 (98%) patients in the combination cohort. Objective response was not observed in the monotherapy cohort. In the combination cohort, seven patients had an objective response. Median time to progression-free survival was 2 months for both cohorts. Furthermore, alomfilimab showed evidence of target engagement on T-cell subsets, specifically cluster of differentiation (CD)4+memory cells, in both single-agent and in combination treatment with atezolizumab. This was accompanied by transient elevation of granulocyte-macrophage colony-stimulating factor, interferon-γ, and tumor necrosis factor-α levels and dose-dependent reduction of ICOS+Tregs in the tumor microenvironment. CONCLUSIONS:Alomfilimab treatment was associated with an acceptable safety profile across both mono and combination approaches, accompanied by decreased ICOS+Tregs populations and enhanced CD4+ and CD8+ effector T cells cell activity. Limited clinical activity was observed despite evidence of biological activity. TRIAL REGISTRATION NUMBER:NCT03829501.

Background: Anti-programmed death-1 (PD-1)/cytotoxic T lymphocyte antigen-4 antibodies are efficacious in various malignancies. The potential role of dual checkpoint inhibitors in many rare solid tumors is not established. Objectives: This study presents the results of ipilimumab–nivolumab in salivary gland neoplasm cohorts of the SWOG S1609 dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) trial. Design: DART is a prospective, open-label, multicenter (1016 US sites), multi-cohort phase II trial of ipilimumab (1 mg/kg intravenously (IV) every 6 weeks) plus nivolumab (240 mg IV every 2 weeks). Methods: We performed a prospective, multicenter phase II clinical trial of ipilimumab (1 mg/kg IV every 6 weeks) plus nivolumab (240 mg IV every 2 weeks) in three salivary gland neoplasm cohorts: major and minor salivary gland and adenoid cystic cancers. Patients with adenoid cystic salivary gland tumors ( N = 26) and other salivary gland neoplasms ( N = 34) were evaluable. The most common site of origin was the parotid (31%, N = 8 adenoid cystic group; 68%, N = 23 remaining histologies). Results: In the adenoid cystic group, objective response rate (ORR), 4% (complete response (CR) 0%, N = 0; partial response (PR) 4%, N = 1); 6-month progression-free survival (PFS) and overall survival (OS), 32% (95% confidence interval (CI) 18%–57%) and 84% (95% CI 71%–100%), respectively. In the remaining histologic subtypes, the confirmed ORR was 9% (CR, 0%, N = 0; PR, 9%, N = 3); stable disease (SD) >6 months/PR/unconfirmed PR = 35%; 6-month PFS and OS, 34% (95% CI 21%–55%) and 88% (95% CI 78%–100%), respectively. The most common toxicities were fatigue (39%) and diarrhea (26%); diarrhea (8%) was the most common grade 3–4 immune-related adverse event. Conclusion: In salivary gland tumors, combined ipilimumab plus nivolumab resulted in only a 4% ORR in adenoid cystic carcinoma and 9% in all other histologies combined, though the latter showed clinical benefit (included SD >6 months) in 35% of patients. Trial registration: ClinicalTrials.gov registry: NCT02834013.

DNA repair deficiencies result in genomic instability. Data suggest that genomic instability is associated with response to immuno-oncology (IO) therapies. We analyzed outcomes of patients in the IMPACT2 study by the presence of DNA damage response (DDR) alterations and treatment type. Of 662 patients with ≥1 alterations: 109 (16.5%) had DDR alterations (treated, N = 85) and 553 (83.5%) were DDR wild-type (treated, N = 426). In patients with DDR alterations, absence of liver metastases (p = 0.029) and IO therapy (vs. chemotherapy, p = 0.020; vs. anti-DDR agents, p = 0.048) were independent factors predicting longer overall survival (OS). In the DDR-wild-type cohort, independent factors predicting longer OS were IO therapy (compared with each other treatment group: vs. IO+non-IO combinations, p = 0.003; vs. chemotherapy, p < 0.001; vs. anti-DDR agents, p < 0.001; vs. other targeted therapies, p = 0.006), absence of liver metastases (p < 0.001), and normal albumin (p < 0.001) and lactate dehydrogenase (p = 0.001) levels. Prospective studies are warranted to refine the role of DDR alterations as biomarkers of IO response.

Supplementary Figure S2 shows DNA alterations uniquely identified by CGTP. Panel A: Distribution of CGTP-unique DNA alterations Panel B: Number of CGTP-unique DNA alterations across patients Panel C: Actionable CGTP-unique fusion events

Supplementary Table S3 shows treatment status and the expression of ADC targets.

Abstract Introduction: IGSF8 (Immunoglobulin superfamily member 8) is a novel immune checkpoint that regulates both natural killer (NK) cell cytotoxicity and dendritic cell (DC)-mediated antigen presentation. GV20-0251, an artificial intelligence-designed antibody targeting IGSF8, is being evaluated in a Phase 1/2a clinical trial (NCT05669430) for metastatic solid tumors. Here, we report pharmacodynamic evaluation and potential predictive biomarkers from the monotherapy dose-escalation cohort. Methods: Target engagement and modulation were measured by flow cytometry on circulating CD3+ T cells. Pre- and on-treatment tumor tissues were assessed for IGSF8 expression and immune regulation by immunohistochemistry (IHC) and RNA-seq. IGSF8 expression in human tumors was examined using RNA-seq data from The Cancer Genome Atlas (TCGA) and IHC on tumor microarrays. Clinical response was evaluated per RECIST v1.1. Results: Forty-two participants were enrolled in this first-in-human monotherapy dose-escalation study. Among 16 evaluable cutaneous melanoma patients who had relapsed following prior anti-PD-1 treatment, three confirmed partial responses were observed. Target occupancy analysis demonstrated saturated IGSF8 binding by GV20-0251 on circulating T cells at doses ≥3 mg/kg. Treatment resulted in rapid reduction of IGSF8 cell surface expression on both circulating T cells and malignant cells within tumor tissues. IHC analysis of five paired tumor biopsies showed increased intratumoral infiltration of CD56+ NK cells and CD8+ T cells following treatment. RNA-seq of four paired melanoma tissues revealed immune cell infiltration, antigen presentation, and NK cytotoxicity as the top upregulated pathways post-treatment. Analysis of pretreatment tumors (n=10) revealed that patients achieving clinical benefit (partial response or stable disease) had higher IGSF8 RNA and membrane protein expression. In contrast, no objective response was observed in tumors with low or absent IGSF8 expression. TCGA database analysis demonstrated significant IGSF8 upregulation across multiple tumor types, including melanoma, hepatocellular carcinoma, and lung cancer. IHC examination of tissue microarrays further confirmed high IGSF8 positivity in these tumor types, all of which present high unmet medical needs. Conclusion: Pharmacodynamic analyses confirmed complete target occupancy at pharmacologically active doses with robust target modulation, leading to enhanced antigen presentation coupled with NK and CD8+ T cell infiltration. Preliminary data suggest a relationship between IGSF8 expression on cancer cells and clinical benefit, warranting further investigation. Collectively, these results provide proof-of-mechanism for GV20-0251 as a novel cancer immunotherapy and establish a potential biomarker strategy for further clinical development. Citation Format: Xingfeng Bao, Caibin Sheng, Inderjit Mehmi, Julio A. Peguero, Shivaani Kummar, Patricia LoRusso, Janice M. Mehnert, Aung Naing, Alexander I. Spira, Justin F. Gainor, Omid Hamid, Justin T. Moyers, Jin Wang, Xihao Wu, Hong Xiao, X. Shirley Liu, Tengfei Xiao, Kristopher Wentzel. Evaluation of pharmacodynamic and potential predictive biomarkers for GV20-0251, an anti-IGSF8 antibody, as monotherapy from ongoing Phase 1/2a study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr CT001.

TPS9615 Background: Cutaneous squamous cell carcinoma (CSCC) is the second most common skin cancer. In the setting of unresectable locally advanced or metastatic disease, checkpoint inhibitors are standard of care and are associated with robust response rates and durable disease control. However, in those who do not respond or progress on immunotherapy, there are limited available standard therapies. Ivonescimab is a tetravalent bispecific antibody targeting programmed cell death protein 1 (PD-1) and vascular endothelial growth factor A (VEGF-A) that has shown promising activity in multiple tumor types. VEGF-mediated activities include driving angiogenesis creating a tortuous tumor vasculature and decreasing effector T-cells within the tumor microenvironment. Herein, we hypothesize that dual targeting of PD-1 and VEGF-A may overcome resistance to checkpoint inhibitors and extend the benefit of immunotherapy in CSCC. Methods: This phase 2, single-arm study will enroll up to 24 patients and will be conducted using a Bayesian optimal phase 2 (BOP2) design. Prespecified activity goal for the first stage of accrual was met; second stage accrual began in January 2026. Patients will receive Ivonescimab 20mg/kg intravenously every 3 weeks until progression, death, or intolerance. The main inclusion criteria include unresectable locally advanced or metastatic CSCC that is refractory to prior checkpoint inhibitors, Eastern Cooperative Oncology group performance score of 0-1, and measurable disease by RECIST version 1.1. Primary exclusion criteria comprise prior severe immunotherapy-associated toxicities, prior organ transplant, or major blood vessel invasion. There are no limits on lines of therapy. Primary objective and endpoint is objective response rate in CSCC. Key secondary endpoints include duration of response, disease control rate, progression free survival, and safety. Additional exploratory objectives include evaluating predictive biomarkers of treatment response or resistance utilizing a mandatory biopsy performed both pre-and on-treatment, with correlatives including whole exome sequencing, RNA sequencing, multiplex IHC. Active recruitment and enrollment are ongoing at The University of Texas MD Anderson Cancer Center, Houston, Texas. Copyright © 2026 AACR. Originally presented at AACR 2026. Reprinted with permission. Clinical trial information: NCT06567314 .

We evaluated clinical outcomes and safety profiles in patients with non-small cell lung cancer (NSCLC) treated in early-phase trials. A retrospective review of 546 NSCLC cases treated from January 2016 to December 2024 at The University of Texas MD Anderson Cancer Center was performed using the MD Anderson CHIMERA database. Patients were categorized into seven groups based on treatment regimen. The overall objective response rate (ORR) was 19.9

OBJECTIVE:Hearing loss from immune checkpoint inhibitors (ICIs) has been documented in case reports and case series. We present the largest retrospective study investigating the rate of ICI-related ototoxicity in a monitored cohort of platinum-naïve patients. STUDY DESIGN:Retrospective cohort study. SETTING:Tertiary-care center. METHODS:Patients treated with ICI between January 1, 2017, and December 31, 2022, with baseline and post-treatment audiograms, were included. Patients with a history of platinum-based chemotherapy were excluded. Demographics, oncologic diagnosis, ICI treatment details, and temporal bone irradiation (TBRT) were recorded. Audiometric thresholds were compared before and after ICI therapy. The primary outcome measure was a change in hearing as defined by the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE). Secondary outcome measures included changes in hearing using the American Speech-Language-Hearing Association (ASHA) and TUNE criteria. RESULTS:Among 15,390 ICI recipients, 29 platinum-naïve patients met the inclusion criteria. Six of 29 patients (20.7%) experienced a CTCAE grade 1 or higher hearing loss. The proportions of hearing loss as defined by ASHA and TUNE criteria were 44.8% and 27.6%, respectively. The length of time between baseline and follow-up audiograms was significantly longer among patients with hearing loss (mean difference [days]: CTCAE: 590.3, P < .01; ASHA: 280.9, P = .05; and TUNE: 122.1, P = .46). No other potential covariates believed to be confounders were significantly associated with the outcome. CONCLUSION:A significant proportion of our monitored platinum-naïve ICI patients met hearing-loss criteria. Prospective studies with standardized audiologic surveillance are needed to further quantify the true incidence of ICI ototoxicity.

e15114 Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with limited treatment options. Phase I trials explore novel therapies, yet the investigational landscape and genomic characteristics of enrolled patients (pts) remain poorly defined. We analyzed therapeutic strategies and genomic profiles of pts in early-phase trials to better inform future precision oncology approaches. Methods: This retrospective study included pts with advanced PDAC at a single center. Demographic, clinical, molecular, and outcome data were extracted from electronic health records. Tumor genomic profiling was performed using next-generation sequencing. Investigational agents were classified by mechanism of action. Response was assessed per RECIST v1.1. Overall survival (OS) was calculated from trial consent to death or last follow-up. Responses were compared using chi-square tests, and associations of OS with mechanisms and responses were evaluated using Kaplan-Meier and log-rank analyses. Results: Between Jan 2015 and Apr 2025, 617 pts with advanced PDAC enrolled in phase 1 trials. Median age was 61 years (range 22–87), 44% were female. Median prior lines of therapy were 2 (range 1–6). Genomic profiling revealed alterations of KRAS in 42% (G12D 19%, G12V 11%, G12R 8%), TP53 in 37%, and CDKN2A/B in 19%. Other actionable alterations included BRCA 1/2 mutations (10%), MTAP deletions (3%), ERBB2 amplifications (2%), and BRAF V600E mutations (0.6%). Across 236 unique agents tested, targeted therapies (TT) were 61% and immunotherapies (IO) were 33%. Monotherapy and combinations were 64% and 36%, respectively. Leading mechanisms included RAS pathway inhibition (18%), immune checkpoint modulation (16%), tumor microenvironment targeting (14%), and DNA damage response inhibition (12%). Best responses included complete response (CR, 0.2%), partial response (PR, 7.6%), stable disease (SD, 31.8%), and progressive disease (PD, 60.4%). The objective response rates (CR + PR) were highest for TT (13.9%) followed by combinations (4%), and IO (1.3%) (p < 0.001). Median OS (mOS) for the entire cohort was 5.0 mo (95% CI, 4.5–5.4). Pts receiving TT had highest mOS (5.5 mo) vs. combinations (5.1 mo), and IO (2.8 mo) (p = 0.002). Response correlated significantly with OS (CR: 49.1 mo, PR: 18.0 mo, SD: 7.6 mo, PD: 3.7 mo) (p < 0.001). KRAS alteration status was not significantly associated with OS. Conclusions: This analysis highlights a shift in PDAC phase I trials from cytotoxic therapy toward precision oncology, with targeted therapies demonstrating superior efficacy. However, the low mOS underscores refractory nature of PDAC. Our findings emphasize that comprehensive genomic profiling is essential for precision therapeutic matching and biomarker-driven trial enrollment in PDAC.

DNA profiling is an established method for cancer treatment selection, while RNA profiling remains investigational. We explored associations between DNA and RNA alterations and between the number of genes with altered expression and overall survival (OS) using patient data from IMPACT2 (NCT02152254), a randomized study evaluating molecular profiling for guiding cancer therapy across tumor types. Molecular profiling, including DNA next-generation sequencing, was performed on all 829 patients in the IMPACT2 study. RNA profiling was performed by Tempus for 253 of 829 patients. We evaluated the concordance between DNA and RNA profiling, analyzed OS in 217 treated patients with RNA profiling, and assessed PD-L1 status and number of genes with altered expression. Fifty patients exhibited 58 concordant events, i.e., genomic and expression alteration(s) in the same gene, including 38 copy number events, and 41 patients had statistically significant concordance. We identified 123 gene pairs with significant associations between genomic and expression alterations (p < 0.05), including TP53 alterations with VEGFA overexpression. The median OS for patients with 0–2, 3–5, and ≥6 genes with altered expression was 9.8, 11.9, and 6.7 months, respectively (p = 0.03). These results underscore RNA profiling’s potential actionability, and altered expression in ≥6 genes was associated with shorter OS. Significant concordance of TP53 alterations with VEGFA overexpression may partially explain tumor response to bevacizumab in TP53-mutant patients.

Background:The use of immune checkpoint inhibitors (ICIs) has led to a paradigm change in cancer management. Many patients may have inherent primary resistance to ICIs or develop secondary resistance after initial response. The impact of using novel therapeutic combinations of checkpoint blockade (avelumab) with immune stimulating agonists such as anti-OX40 and/or anti-4-1BB on the tumor microenvironment and modulation of the immune response is an intriguing strategy to evaluate how these agents interact and whether the hypothetical rationale for combinations can be translated into augmentation of anti-tumor immunity in solid tumors. Methods:We performed whole exome sequencing (WES), bulk RNAseq, multiplex immunofluorescence (mIF) and chromogenic immunohistochemistry (IHC) on tumor tissue and flow cytometry of the peripheral blood to study longitudinal changes following the combination of avelumab with utomilumab (a 4-1BB agonist) (arm A), PF-04518600 (an OX40 agonist) (arm B), utomilumab and PF-04518600 (arm C) and utomilumab and radiotherapy (arm D) in phase I/II study (NCT03217747). Results:We observed low tumor mutation burden (TMB < 6) (median: 1.88), alteration of RTK-RAS, TP53, PI3K and WNT pathways across the cohorts. Mutations in TP53, TTN and KRAS (mostly p.G12C, p.G12D) genes and copy number variations (CNV) were found in PIK3CA, CCNE1 and KRAS. Interferon gamma signaling pathway was enriched early on-treatment in tumors from patients with colorectal and pancreatic cancers in arm C. Patients deriving clinical benefit (CR/PR/SD ≥ 4 months) displayed higher T-cell frequencies at baseline (p = 0.0157), C1D15 (p = 0.0086), and C3D15 (p = 0.0070) than patients without clinical benefit. Conclusions:Our findings, though limited, highlight genomic differences between histologic subsets and outcome as well as the need for combination strategies that drive the recruitment and/or priming of anti-tumor T cells and address low immune permissive tumor states in patients with advanced solid tumors. Clinical trial registration:This clinical trial was registered on clinicaltrials.gov NCT03217747.

3149 Background: Cell cycle pathway alterations are a hallmark of cancer. Disruption of cell cycle checkpoints results in genomic instability, uncontrolled proliferation and tumor progression to aggressive and treatment-resistant phenotypes. We report the clinical outcomes of patients with cell cycle pathway alterations treated in the IMPACT 2 study (2014-2023; NCT02152254). Methods: Patients with advanced cancer underwent tumor biopsy and molecular profiling (CLIA-certified lab). Pathway analysis was conducted using the maftools R package. Cell cycle pathway alterations were defined as those involving the CCND1 , CCND2 , CCNE1 , CDK4 , CDK6 , CDKN2A , CDKN2B , and RB1 genes. Cases were discussed at Molecular Tumor Board meetings. Patients were treated on clinical trials with investigational agents that included matched targeted therapies (MTTs) when available. We analyzed the following outcomes by treatment type (MTT vs. non-matched targeted therapy [NTT] and immunotherapy [IO] vs. non-IO): objective response rate (complete response + partial response), clinical benefit rate (CBR; ORR + stable disease≥4 months), progression-free survival (PFS), and overall survival (OS). Results: Of 491 treated patients with targetable alterations, 157 (32.0%) had cell cycle pathway alterations (median age, 61 years [range, 21-82]; female, 46.5%; ECOG performance status 1, 85.4%; median number of prior therapies, 3 [range, 0-9]; liver metastases, 40.8%; >2 metastatic sites, 36.3%; high LDH, 33.1%; low albumin, 10.8%). The most common cancers were sarcoma (19.7%), other gastrointestinal (17.2%), head and neck (14.0%), lung (9.6%), and breast (8.3%). Other tumor characteristics included PD-L1 ≥1%, 45.6% (41/90); MSI-H, 2.0% (2/102); and TMB-H, 13.0% (13/100). Concomitant pathway alterations were TP53 (67.5%), PI3K (29.9%), and RTK-RAS (47.1%). MTT targeted CDK4/6, n=9; BET, n=2; ATR, n=1; PKMYT1, n=1; and ACAT, n=1. Clinical outcomes are shown in the Table. Conclusions: Very few investigational therapies that target the cell cycle pathway were available. No differences were noted in tumor response, PFS, or OS by type of therapy, likely owing to the limited antitumor activity of the MTTs and the complexity of targeting this pathway. Novel and effective MTTs are needed for tumors with cell cycle dysregulation. Clinical trial information: NCT02152254 . All patients MTT NTT P IO Non-IO P N=157 N=14 N=143 N=40 N=117 ORR (%) 7/135 (5.2) 0/12 (0) 7/123 (5.7) 1.00 4/33 (12.1) 3/102 (2.9) 0.14 CBR (%) 76/135 (56.3) 6/12 (50.0) 70/123 (56.9) 0.76 19/33 (57.6) 57/102 (55.9) 1.00 Median PFS, months(95% CI) 3.75(2.66, 5.49) 3.75(1.81, NA) 3.58(2.66, 5.52) 0.81 2.96(1.81, 8.98) 3.75(2.66, 5.59) 0.98 Median OS, months(95% CI) 8.48(7.1, 11.21) 6.66(5.56, NA) 8.61(7.17, 11.57) 0.40 7.46(5.19, 17.42) 8.48(7.1, 11.57) 0.72

e20531 Background: Interstitial lung abnormalities (ILAs) are established risk factors for immune checkpoint inhibitor–related pneumonitis (ICI-P), but qualitative ILA assessment is subjective. We evaluated whether quantitative lung fibrosis (QLF) metrics from pretreatment computed tomography (CT) are associated with ICI-P in patients with non–small cell lung cancer (NSCLC) receiving immune checkpoint inhibitors (ICIs). Methods: We retrospectively analyzed 241 patients with metastatic NSCLC treated with ICIs. Pretreatment CT scans underwent quantitative analysis using commercial software (VIDA) to extract QLFs representing consolidation, ground-glass opacity (GGO), emphysema, reticulation, and honeycombing. QLFs were quantified by percentage, volume, and estimated mass at total lung, lobar (upper vs lower), and subregional (core [central] vs peel [peripheral]) levels. Associations between QLFs and ICI-P were evaluated using univariate logistic regression. Results: Regional QLFs demonstrated differential associations with ICI-P. Upper-lobe QLFs were not associated with pneumonitis (all p≥0.13). In contrast, lower-lobe mass-based fibrosis metrics were associated with increased ICI-P risk, including GGO mass (OR 1.005, 95% CI 1.001–1.010; p=0.030), quantitative ILD (QILD) mass (OR 1.004, 95% CI 1.000–1.008; p=0.031), and quantitative ILA (QILA) mass (OR 1.004, 95% CI 1.001–1.007; p=0.024). Total-lung QILA mass showed a trend toward association (OR 1.002, 95% CI 1.000–1.004; p=0.086). Subregional analysis demonstrated stronger associations in peripheral (peel) regions; peel consolidation volume was associated with ICI-P (OR 1.102, 95% CI 1.013–1.198; p=0.023), whereas no core metric reached significance. Conclusions: Quantitative fibrosis metrics from pretreatment CT, particularly lower-lobe and peripheral mass-based QLFs, are associated with immune checkpoint inhibitor–related pneumonitis in NSCLC. Incorporation of regional quantitative fibrosis measures into baseline imaging assessment may help identify patients at elevated pneumonitis risk and inform surveillance strategies. These findings support further multivariable validation of quantitative CT fibrosis metrics as imaging biomarkers for immunotherapy-related pneumonitis. Associations between quantitative lung fibrosis metrics and immune checkpoint inhibitor–related pneumonitis in NSCLC. Region Metric (Mass-based QLF) (gm) OR 95% CI p-value Lower lobe GGO Mass 1.005 1.001–1.010 0.030 Lower lobe QILD Mass 1.004 1.000–1.008 0.031 Lower lobe QILA Mass 1.004 1.001–1.007 0.024 Upper lobe No significant predictors — — ≥0.13 Total lung QILA Mass 1.002 1.000–1.004 0.086

Supplementary Figure S4 the correlation between treatment status and expression of ADC targets.

3151 Background: The receptor tyrosine kinase (RTK)-RAS signaling axis comprises distinct membrane receptors and downstream effectors that regulate cell proliferation and survival. Alterations in this pathway drive carcinogenesis and are associated with poor prognosis. We analyzed the outcomes of patients with RTK-RAS pathway alterations enrolled in the IMPACT 2 study (2014-2023; NCT02152254). Methods: Patients with advanced cancer underwent tumor biopsy and molecular profiling (CLIA-certified lab). Pathway analysis was conducted using the maftools R package. RTK-RAS pathway alterations were defined as those involving EGFR, ERBB2, ALK, MET, KRAS, NRAS, BRAF , and MAP2K1/2 genes. Cases were discussed at Molecular Tumor Board meetings. Patients were treated in clinical trials with investigational agents, including matched targeted therapies (MTTs) when available. We analyzed the following outcomes by treatment type (MTT vs. non-matched targeted therapy [NTT] and immunotherapy [IO] vs. non-IO): objective response rate (ORR; complete response + partial response), clinical benefit rate (CBR; ORR + stable disease≥4 months), progression-free survival (PFS), and overall survival (OS). Results: Of 491 treated patients with targetable alterations, 216 (44%) had RTK-RAS pathway alterations (median age, 62.3 years [range, 21-80]; female, 54.1%; ECOG performance status 1, 90.3%; median number of prior therapies, 3 [range, 0-10]; liver metastases, 46.3%; > 2 metastatic sites, 34.7%; high LDH, 37.0%; low albumin level, 11.1%). The most common cancers were gastrointestinal (40.3%), head/neck (10.2%), and lung (10.2%). Other tumor characteristics included PD-L1≥1%, 43.6% (58/133); MSI-H, 1.3% (2/153); and TMB-H, 10.7% (16/150). Concomitant pathway alterations were TP53 (62.5%), PI3K (26.9%), and cell cycle (34.3%) pathways. MTT targeted EGFR, n = 8; FGFR, n = 10; HER2, n = 6; BRAF+MEK, n = 3; ALK, n = 1; and MEK, n = 4 among others (n = 24). Clinical outcomes are shown in the Table. Conclusions: The ORR was 14.6% in IO-treated patients vs. 5% in the non-IO-treated group (p = 0.049), although the difference was not significant. No differences in PFS or OS were observed by therapy type in patients with RTK-RAS pathway alterations. Novel MTTs (i.e., KRAS inhibitors) that were unavailable during the study period may improve the outcomes of these patients. Identification of molecular subsets benefiting from MTT is needed. Clinical trial information: NCT02152254 . All patients MTT NTT P value IO Non-IO P value N=216 N=56 N=160 N=57 N=159 ORR (%) 14/189 (7.4) 5/50 (10) 9/139 (6.5) 0.53 7/48 (14.6) 7/141 (5) 0.049 CBR (%) 110/189 (58.2) 31/50 (62) 79/139 (56.8) 0.62 27/48 (56.3) 83/141 (58.9) 0.87 Median PFS, months(95% CI) 2.96(2.3, 3.81) 3.09(2.66, 8.02) 2.89(1.97, 4.08) 0.5 2.3(1.61, 5.42) 3.19(2.66, 4.08) 0.72 Median OS, months(95% CI) 7.36 (5.69, 9.21) 5.88(4.7, 18.28) 7.79(5.69, 9.44) 0.10 6.61(4.6, 12.76) 7.46(5.69, 9.21) 0.85