Citations

e21561 Background: Immune checkpoint inhibitors (ICIs) have become the standard first-line systemic therapy for metastatic Merkel cell carcinoma (MCC). Radiotherapy (RT) remains commonly used for local control and palliation, and growing biologic interest suggests that RT may enhance antitumor immune responses when combined with ICIs. However, population-level evidence regarding contemporary patterns of RT use and its association with survival in immunotherapy-treated patients with metastatic MCC is limited. Methods: We conducted a retrospective population-based cohort study using the National Cancer Database (NCDB), including adults diagnosed with metastatic MCC between 2011 and 2022. Temporal trends in treatment utilization were described across the study period. Among patients diagnosed in the immunotherapy era (2017–2022), factors associated with receipt of RT were examined using multivariable logistic regression. To evaluate survival, analyses were restricted to immunotherapy-treated patients, and overall survival was compared between those who received RT and those who did not using propensity score-matched Kaplan-Meier and Cox proportional hazards analyses, with a focus on 2-year overall survival. Results: A total of 1,736 patients with metastatic MCC were included. Following 2017, immunotherapy use increased substantially, while chemotherapy use declined; RT utilization remained relatively stable over time. In multivariable analyses restricted to the immunotherapy era, higher primary tumor stage and lymph node dissection were independently associated with RT receipt. Among immunotherapy-treated patients in the propensity score-matched cohort, RT was not associated with improved 2-year OS (aHR,1.09; 95% CI, 0.84-1.42), and Kaplan-Meier analyses demonstrated no significant survival difference. Conclusions: In the contemporary immunotherapy era, RT continues to be selectively incorporated into the management of metastatic MCC, particularly in patients with greater local or regional disease burden. However, among immunotherapy-treated patients, RT was not associated with improved short-term overall survival at the population level. These findings support a continued role for RT in local disease management while underscoring the need for prospective studies to better define its optimal integration with immunotherapy.

e21533 Background: Clinical decision-making in melanoma is challenged by heterogeneous disease biology, evolving treatment paradigms, and fragmented longitudinal data. Although EMRs contain real-world information, clinicians often lack tools that organize these data around clinically meaningful milestones to support pre-visit decision-making. We developed CODE-M, an AI–enabled framework designed to identify clinically similar patients (“patients like mine”) and surface outcome-relevant insights using real-world data. Methods: CODE-M was developed using data derived from EMRs at a large academic cancer center. Patient data were normalized and aligned to a clinically defined ordinal timeline spanning diagnosis, adjuvant therapy, recurrence, progression, systemic treatment, and outcomes. Similarity modeling incorporated demographics, disease stage, treatment history, longitudinal outcomes, and available molecular and genomic attributes, represented as contextual features within the timeline. AI-based similarity modeling generated retrospective cohorts reflecting shared clinical features of an index patient and supported iterative cohort generation for competing progression-free and overall survival analyses using automated Kaplan–Meier, Cox proportional hazards, and feature association models. A clinician-facing pre-visit summary presents cohort characteristics, outcomes, and relevant clinical trial options prior to patient encounters. Results: The framework reliably aligned heterogeneous longitudinal EMR data to a shared clinical timeline and generated reproducible, clinically coherent patient cohorts reflecting shared disease stage, treatment exposure, and melanoma care patterns. Iterative cohort generation enabled comparative analyses across competing cohorts, resulting in predictable shifts in observed progression-free and overall survival distributions. Pre-visit summaries and analytic outputs were reviewed by clinicians and demonstrated interpretability and relevance for visit preparation. The platform also identified clinical trials based on eligibility criteria, trial availability, and patient geographic proximity, integrating trial matching into the clinical decision workflow. Conclusions: An AI-enabled, ordinal timeline–based approach can structure real-world melanoma data to support pre-visit clinical context through patient similarity analysis and comparative outcome visualization. CODE-M summarizes observed outcomes among clinically similar patients and is intended to support contextual understanding of prior care experiences rather than generate treatment recommendations or patient-specific predictions. This framework supports clinical insight, hypothesis generation, and shared decision-making using longitudinal EMR-derived data, with applicability across oncology disease types.

e21521 Background: Outcomes following tumor-infiltrating lymphocyte (TIL) therapy vary in real-world practice, and accessible predictors are needed to inform patient selection and timing of referral. We evaluated whether baseline disease burden, metastatic distribution, and treatment delivery factors are associated with outcomes following TIL therapy. Methods: We retrospectively analyzed patients with metastatic melanoma treated with TIL therapy across Mayo Clinic sites (N = 27 infused). Baseline disease burden was characterized using AJCC metastatic stage and organ-specific involvement. A composite high visceral burden variable was defined as the presence of M1d disease and/or liver metastases. Bridging therapy use prior to infusion was recorded. Post-infusion IL-2 exposure was categorized as low (0-2 doses) vs. high (3-6 doses). Best overall response (BOR) was summarized using RECIST-based standard criteria. Overall survival (OS) and progression-free survival (PFS) were measured from TIL infusion and estimated using Kaplan–Meier methods with univariable Cox regression. Results: Median age at infusion was 62.0 years; 59.3% were male. Melanoma subtypes included cutaneous (81.5%) and mucosal (18.5%). Bridging therapy was used in 48.1%. Baseline metastatic stage was M1a/M1b in 18.5%, M1c in 63.0%, and M1d in 18.5%. Median follow up was 8.3 months. BOR included complete response (18.5%), partial response (37.0%), stable disease (22.2%), and progressive disease (22.2%), yielding an objective response rate of 55.6% and disease control rate of 77.8%. Patients with high visceral disease burden experienced inferior OS vs. those without high visceral burden (median 5.2 vs 13.4 months; HR 4.77, 95% CI 1.22–18.63; p = 0.014). Bridging therapy was not associated with OS or PFS. Higher post-infusion IL-2 exposure (seen in 77.8% of patients) was associated with improved OS (median 9.0 vs 3.7 months; HR 0.16, 95% CI 0.04–0.67, p = 0.005), likely reflecting early post-infusion clinical tolerance rather than a causal treatment effect. Median PFS for the cohort was 3.6 months and did not differ by IL-2 exposure ( p = 0.3), metastatic stage ( p = 0.8), bridging therapy ( p = 0.7), liver metastases ( p = 0.2), or LDH above upper limit of normal ( p = 0.1). Conclusions: The above findings are hypothesis generating and will support evaluation in larger cohort. In this real-world cohort of patients treated with TIL therapy, baseline visceral disease burden was strongly associated with survival outcomes, while bridging therapy did not compromise post-infusion efficacy among patients proceeding to infusion. Post-infusion IL-2 exposure correlated with OS and likely reflects early treatment tolerance. These readily available clinical features may inform patient counseling, referral timing, and sequencing decisions as TIL therapy enters broader clinical use.

9557 Background: High-dose interleukin-2 (IL-2) is administered following tumor-infiltrating lymphocyte (TIL) therapy, yet cardiotoxicity frequently limits dose delivery. The clinical significance of peri-dose troponin elevations during IL-2 remains poorly defined. We evaluated troponin kinetics during IL-2 dosing and their association with significant cardiac events and IL-2 interruption. Methods: We retrospectively analyzed patients with metastatic melanoma treated with TIL therapy followed by inpatient high-dose IL-2 at Mayo Clinic Rochester (N = 24; 87 IL-2 doses). High-sensitivity troponin and ECGs were obtained before and after each IL-2 dose. Clinically significant cardiac events were defined as QTc prolongation > 480 ms, arrhythmias (excluding isolated sinus tachycardia), new ECG abnormalities, vasopressor requirement, or cardiology consultation. Dose-level outcomes included cardiac events and subsequent IL-2 dose interruption. Paired troponin changes were assessed using Wilcoxon signed-rank testing. Dose-level associations were evaluated using clustered logistic regression to account for repeated IL-2 doses within patients. Results: 24 patients received 87 IL-2 doses (median 3 [IQR 2 - 5]). Median age was 63 years (IQR 54 - 70), and 58% were male. Baseline troponin median was 11 ng/L (IQR 6 - 21); 38% had baseline troponin > 14 ng/L. Post-dose troponin exceeded 14 ng/L in 16/24 patients (67%) and 48/87 doses (52%). Median delta troponin was 0 ng/L (IQR −1 to 6; range −24 to 133), with post-dose levels higher than pre-dose values ( p = 0.02). Clinically significant cardiac events occurred in 33% of patients; no post-IL-2 reductions in left ventricular ejection fraction were observed. At the dose level, cardiac events occurred only when post-dose troponin exceeded 14 ng/L (15/48 [31%] vs 0/39 doses; p < 0.001). In clustered logistic regression, post-dose troponin ≥15 ng/L was independently associated with cardiac events (OR 9.6, 95% CI 1.5 - 60.6; p = 0.02) and subsequent IL-2 dose interruption (OR 3.4, 95% CI 1.1 - 10.7; p = 0.04). When modeled continuously, each 1-unit increase in log-transformed post-dose troponin was associated with higher odds of cardiac events (OR 3.3, 95% CI 1.6 - 6.7; p = 0.001) and IL-2 interruption (OR 2.8, 95% CI 1.6 - 4.9; p < 0.001). Baseline troponin correlated with peak post-dose troponin (ρ = 0.44, p = 0.04). Conclusions: Peri-dose troponin elevations are common during post-TIL high-dose IL-2; however, higher post-dose troponin independently identifies clinically significant cardiac toxicity and predicts IL-2 interruption after accounting for repeated dosing within patients. Baseline troponin modestly predicts peak elevations, supporting standardized, risk-stratified troponin monitoring and prospective evaluation of toxicity-adaptive IL-2 delivery strategies in TIL therapy.

9558 Background: Ipilimumab 3 mg/kg plus nivolumab 1 mg/kg (Ipi3+Nivo1) is the standard immunotherapy regimen for metastatic melanoma with brain metastases (MBM) but is associated with significant immune-related toxicity, particularly neurologic toxicity. Ipilimumab 1 mg/kg plus nivolumab 3 mg/kg (Ipi1+Nivo3) has demonstrated improved tolerability in extracranial melanoma, though comparative data in MBM are limited. We compared efficacy and toxicity of these dosing strategies in a multisite real-world cohort. Methods: We retrospectively identified patients with MBM treated with ipilimumab plus nivolumab across three Mayo Clinic sites between 2016 and 2024. Patients were classified by induction dosing as Ipi1+Nivo3 or Ipi3+Nivo1. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan–Meier method and compared using log-rank tests. Best overall response (BOR) and toxicity outcomes were summarized descriptively. Results: Among 147 patients (Ipi1+Nivo3 n=32; Ipi3+Nivo1 n=115), 144 were evaluable for survival. Median age was higher in the Ipi1+Nivo3 group (69.5 vs 66.0 years); males predominated in both groups (71.9% vs 61.7%), and the cohort was predominantly White (>96%). Most patients had ECOG 0–1 in both groups (84.4% in Ipi1+ Nivo3 and 90.4% in Ipi3+Nivo1). BRAF mutation status was balanced between regimens, with approximately half of patients harboring BRAF-mutant disease (51.6% vs 53.2%). Median OS was 18.5 months (95% CI, 5.7–54.7) with Ipi1+Nivo3 versus 10.6 months (95% CI, 6.5–19.1) with Ipi3+Nivo1 (log-rank p=0.25). Two-year OS was 45.9% and 35.0%, and five-year OS was 24.5% and 19.2%, respectively. Median PFS was 7.3 months (95% CI, 1.8–10.9) versus 2.8 months (95% CI, 2.1–4.4) (log-rank p=0.16). BOR was available for 138 patients; objective response rates were 35.5% and 31.8%, respectively. 3–5 adverse events occurred in 24.1% of Ipi1+Nivo3 versus 30.5% of Ipi3+Nivo1 patients. Hospitalizations were less frequent (16.7% vs 36.1%), and neurologic adverse events occurred only with Ipi3+Nivo1 (11.9% vs 0%). Conclusions: In this multisite real-world MBM cohort, Ipi1+Nivo3 demonstrated comparable efficacy, numerically longer survival, and a more favorable toxicity profile compared with standard Ipi3+Nivo1. Notably, no neurologic toxicity was observed with the Ipi1+Nivo3 regimen. These findings support further prospective evaluation of lower dose ipilimumab strategies. Response and survival outcomes. Outcome Ipi1 + Nivo3 Ipi3 + Nivo1 Complete response (CR) 2 / 31 (6.5%) 8 / 107 (7.5%) Partial response (PR) 9 / 31 (29.0%) 26 / 107 (24.3%) Objective response rate (ORR = CR+PR) 11 / 31 (35.5%) 34 / 107 (31.8%) Disease control rate (DCR = CR+PR+SD) 18 / 31 (58.1%) 51 / 107 (47.7%) Median PFS, months (95% CI) 7.3 (1.8–10.9) 2.8 (2.1–4.4) 2-year PFS 27.6% 22.3% Median OS, months (95% CI) 18.5 (5.7–54.7) 10.6 (6.5–19.1) 2-year OS 45.9% 35.0% 5-year OS 24.5% 19.2%

9523 Background: Primary Central Nervous System (CNS) Melanoma is a rare and aggressive malignancy, comprising 1% of melanoma cases and 0.07% of brain tumors. Due to its rarity, its natural history, molecular features and optimal management remain poorly defined. Methods: We retrospectively reviewed patients at our institution between January 1998 and October 2025 with primary CNS melanoma or melanocytoma with melanoma transformation. Clinical characteristics, molecular profiling, treatments and survival outcomes were collected. Overall survival (OS) and progression free survival (PFS) were estimated using Kaplan-Meier curves. Results: Nineteen patients were identified, including eight (42%) with melanocytoma to melanoma transformation. Median time of transformation was 34.4 months. Thirteen (68%) patients were female with a median age at diagnosis of 59.3 years. Common presenting symptoms were sensory disturbances (58%), pain (53%), motor deficits (37%) and nausea or vomiting (32%). At diagnosis, location of disease was spinal (n=12), intracranial (n=6) and multifocal (n=1). Thirteen patients had leptomeningeal involvement. Molecular profiling was performed in 15 patients, revealing mutations in GNAQ (n=7), GNA11 (n=3), CKIT (n=2), BAP1 (n=1), EIF1AX (n=1), and BRAF v600 (n=1). Thirteen (68%) patients underwent subtotal resection (STR), five (26%) gross total resection (GTR) and one radiation only. Median resected tumor size was 1.7 cm. Seventeen (94%) patients had recurrence at a median of 9.1 months, and four patients underwent repeat surgery. Fourteen (74%) patients received adjuvant radiation and 14 (74%) received immunotherapy, most commonly ipilimumab with nivolumab (71%). Nine patients received chemotherapy: temozolomide (n=5), bevacizumab (n=2) and one each of intrathecal IL-2, tebentafusp, imatinib and encorafenib with binimetininb. Four patients received chemotherapy before immunotherapy. Median OS from diagnosis of CNS melanocytoma or melanoma was 50.9 months (13.4 – 80). Median OS from time of transformation to melanoma or CNS melanoma diagnosis was 24.0 months (11.9 – NA). One-, three- and five-year OS rates were 73%, 53% and 40% respectively. GTR was associated with increased median OS compared to STR (80.0 vs 19.7 months, p= 0.02). Age at diagnosis, immunotherapy, chemotherapy, adjuvant radiation, STR with or without radiation, disease location, leptomeningeal involvement, tumor size >3cm and presence of GNAQ mutation were not associated with survival. Median PFS was 3 months with chemotherapy and 5.7 months with immunotherapy. Conclusions: To our knowledge, this is the largest single center study of primary CNS melanoma. Outcomes remain poor, with survival primarily associated with GTR. The predominance of GNAQ and GNA11 alterations with rare BRAF v600 mutations highlight the distinct biology of primary CNS melanoma and need for novel targeted therapies.

ABSTRACT Circulating tumor DNA (ctDNA) as a liquid biopsy is an emerging tool used for diagnosis and disease monitoring, yet not all tumors shed DNA equally, thus currently limiting the clinical applicability of this tool. Our institution has developed and validated a droplet digital Polymerase Chain Reaction (ddPCR) ctDNA test for BRAF V600 mutation. We collected data on all BRAF mutated melanoma patients tested with the ddPCR BRAF assay at our institution over the years 2018–2024 and correlated the test results with clinical and radiological baseline parameters, with a focus on Positron Emission Tomography‐Computed Tomography (PET‐CT) data, incorporating both location of lesions and volume of disease. Linear and logistic regression modelling was used to assess possible associations between the baseline parameters and the ctDNA results. We identified 71 BRAF mutated melanoma patients, of which 65 had active disease on imaging studies and 43 had PET‐CT data available for analysis. Multivariate modelling has shown that patients were more likely to have a positive ctDNA result if they had elevated serum lactate dehydrogenase (LDH) (OR = 9.9), had a higher number of lesions on imaging studies (> 10 lesions: OR = 11.3), and if they were younger than 65 (OR = 11.8), with an AUC of 0.84. The PET‐CT calculated total metabolic tumor volume correlated with the quantitative ctDNA result with a Pearson r factor of 0.49. In conclusion, ctDNA ddPCR BRAF testing is easily obtained and might be especially beneficial for patients diagnosed with a clinically aggressive disease, based on elevated LDH, higher PET‐CT metabolic tumor volume, and younger age.

Abstract Background: High-dose interleukin-2 (IL-2) is administered after tumor-infiltrating lymphocyte (TIL) infusion to promote in-vivo expansion and persistence, yet optimal dosing and the clinical significance of out-of-specification (OOS) TIL products remain unclear. We investigated the impact of number of infused IL-2 doses and manufacturing OOS status on outcomes in metastatic melanoma treated with commercial TIL therapy. Methods: We retrospectively analyzed 31 patients treated across three Mayo Clinic sites. Planned IL-2 was 600,000 IU/kg every 12 hours for ≤6 doses; actual dosing varied based on clinical tolerance. Patients were grouped as low (0-2) vs high (≥3) IL-2 doses. TIL products were classified as within-specification or OOS per commercial release criteria. Survival associations were evaluated using Kaplan-Meier and multivariable Cox regression. Results: In our 31-patient cohort, the median age was 59 years (range 17-77), 58% were male, and 84% had ECOG 0. At TIL infusion, M-stage distribution was M1a 6%, M1b 10%, M1c 61%, and M1d 23%. LDH was elevated above the upper limit of normal in 42%. The median number of IL-2 infusions was 4 (range 0-6); 58% of patients received ≥3 doses, while 2 patients (6%) received none. Out-of-specification (OOS) TIL products occurred in 6 patients (19%). Best responses included complete response (26%) and partial response (23%), for an overall response rate of 48% and a disease-control rate of 61% (CR + PR + SD). Among responders, the median duration of response was 84 days (95% CI 73-95). At data cutoff, the median follow-up was 253 days (95% CI 137-370). The most common grade 3/4 toxicities occurring &gt;14 days after TIL infusion were lymphopenia (39%), anemia (16%), and thrombocytopenia (10%). Median progression-free survival (PFS) was 99 days (95% CI 73-125) with 20 progression events, and median overall survival (OS) was 193 days (95% CI 32-354) with 13 deaths. Number of infused IL-2 doses was dependent on patients tolerability. Receiving ≥3 IL-2 doses was associated with improved overall survival (394 vs 101 days; p &lt; 0.001) and a trend toward longer progression-free survival (110 vs 59 days; p = 0.055). OOS products predicted inferior PFS (30 vs 110 days; p = 0.003) and showed a trend toward worse OS (120 vs 394 days; p = 0.079). In multivariate analysis, ≥3 IL-2 doses independently improved PFS (HR 0.20, 95% CI 0.06-0.69; p = 0.011) and OS (HR 0.09, 0.02-0.36; p = 0.001), while OOS status increased risk of progression (HR 8.10, 2.24-29.25; p = 0.001) and death (HR 6.16, 1.35-28.20; p = 0.019). Conclusions: Higher number of infused doses IL-2 and meeting commercial TIL release criteria were independently associated with improved outcomes. Citation Format: Mohamed A. Aboelatta, Jeffrey E. Johnson, Jabra G. Zarka, Matyáš Benada, James W. Jakub, Roxana S. Dronca, Ruqin Chen, Mahesh Seetharam, Deepti Behl, Svetomir N. Markovic, Lisa A. Kottschade, Heather N. Montane, Matthew S. Block, Anastasios Dimou, Robert R. McWilliams, Paula Gill, Yi Lin, Arkadiusz Z. Dudek. Impact of number of IL-2 infusions and product out of specification status on outcomes of tumor infiltrating lymphocyte therapy for melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3706.

Abstract The sentinel lymph node (SLN) is often the first site of melanoma spread and a critical immune checkpoint that determines local tumor dissemination to systemic metastasis. Although lymph nodes are central to antitumor immunity, the mechanisms that render them permissive to metastasis remain poorly understood. This study used spatial imaging to characterize immune and stromal phenotypic alteration in tumor-negative SLNs (SLN-) and tumor-positive SLNs (SLN+) from patients with cutaneous melanoma, compared to non-melanoma-associated normal lymph nodes (NLN). We performed multiplex immunofluorescence (MxIF) analysis of formalin-fixed, paraffin-embedded lymph node tissues from patients with cutaneous melanoma and control subjects, including two subjects per group (NLN, SLN-, and SLN+). Furthermore, quantitative single-cell segmentation and classification using QuPath generated median fluorescence intensities for immune, stromal, and tumor markers across LN, SLN- and SLN+ regions of interest. In addition to the initial analysis, we employed spatial neighborhood analysis to characterize markers expression profiles surrounding target immune population. This approach quantified local microenvironment based on marker normalized intensity-based co-expression pattern and stromal remodeling signatures. We grouped these markers based on the functional panels representing T-cell activation and exhaustion, myeloid polarization, tumor interaction, stromal remodeling, and apoptosis pathways providing insights into how prometastatic niche evolve within SLN. Normalized data, via centered log ratio (CLR) transformation and Gaussian Mixture Model (GMM) gating was analyzed using principal component analysis, UMAP/tSNE embedding, and hierarchical clustering in in python. Progressive immune remodeling was observed from normal NLN to SLN+, including expansion of regulatory T cells, enrichment of exhausted T cells as well as myeloid-derived suppressor cells (MDSC), and transition toward an M2-like macrophage phenotype. The spatial data from SLN- samples showed an early sign of immune suppression, with reduced cytotoxic capacity. These results show that SLN gets features of peripheral immune tolerance for melanoma early, prior to pathological dissection of metastatic spread supporting the existence of a pre-metastatic niche that facilitates lymphatic colonization of tumor cells. This work provides insights into early immune escape and may inform strategies for immunotherapy and early intervention in melanoma. Citation Format: Shankar Suman, Wendy K. Nevala, Noah A. Stueven, Raymond M. Moore, Chathu L. Atherton, Jeffrey E. Johnson, Ray Guo, James W. Jakub, Svetomir N. Markovic. Spatial remodeling of immune and stromal microenvironments in sentinel lymph nodes during melanoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6193.

Abstract Introduction: Placental cell-free DNA (cfDNA) activates maternal monocytes to a proinflammatory phenotype through cGAS-STING signaling during pregnancy, thereby stimulating T cells. We sought to engineer DNA nanocarriers that reproduce this mechanism in human monocytes using clinically translatable materials as a strategy for tumor-associated macrophage (TAM) reprogramming. Methods: A synthetic mimic of fetal cfDNA (scfDNA) was designed, commercially synthesized, and complexed with polyethylenimine (PEI) to form scfDNA-PEI nanoparticles (scfDNA-PEI-NPs) for cytosolic delivery. THP-1 Dual reporter monocytes expressing interferon regulatory factor (IRF)-inducible luciferase were treated with scfDNA-PEI-NPs or human cytotrophoblast derived cfDNA (CTB-DNA) to quantify cGAS-STING-IRF activation. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release to define a non-toxic therapeutic window. Results: scfDNA-PEI-NPs triggered robust cGAS-STING-IRF activation in THP-1 monocytes, exceeding CTB-DNA responses. This response was abolished in cGAS-knockout cells and rescued by a cGAS-independent stimulator of the IRF pathway, confirming cGAS specificity of scfDNA-PEI-NPs. Dose-response analysis showed a &gt; 10-fold separation between cGAS-activating and cytotoxic concentrations, establishing a therapeutic window for myeloid-selective cGAS activation. Conclusions: These findings provide proof-of-concept that pregnancy-inspired DNA nanocarriers can reproduce fetal cfDNA-driven activation of a proinflammatory monocyte phenotype in vitro. This platform lays the groundwork for future work on macrophage-targeted cGAS activation and proinflammatory reprogramming for tumor immunotherapy development. Citation Format: Mathew R. Schnorenberg, Elizabeth Ann L. Enninga, Wendy K. Nevala, Noah A. Stueven, Svetomir N. Markovic, . Pregnancy-inspired DNA nanocarriers reproduce a cGAS-driven pro-inflammatory monocyte phenotype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4307.