PFS and OS by detection of BRAF V600 alterations in ctDNA at (A and B) baseline and (C and D) on treatment. Only patients with BRAF V600 alteration detections at baseline are shown in C and D. Bini, binimetinib; D, detectable; Enco, encorafenib; ND, nondetectable; Vemu, vemurafenib.

PURPOSE:Treatment with encorafenib ± binimetinib is associated with improved survival versus vemurafenib in patients with BRAF V600E/K-mutant advanced melanoma. We retrospectively analyzed genomic and transcriptomic data from the phase III COLUMBUS trial to identify molecular correlates of benefit with encorafenib ± binimetinib. EXPERIMENTAL DESIGN:In COLUMBUS, patients with BRAF V600E/K-mutant locally advanced, unresectable, or metastatic melanoma (n = 921) were randomized to receive encorafenib plus binimetinib, encorafenib, or vemurafenib. We used whole-exome sequencing (n = 666), whole-transcriptome sequencing (RNA sequencing; n = 514), and assessment of circulating tumor DNA (ctDNA) at baseline (n = 336) and on treatment (cycle 2 day 1, n = 184) to evaluate biomarker associations with progression-free and overall survival. RESULTS:Survival benefits with encorafenib plus binimetinib versus vemurafenib were greatest in patients with higher tumor mutational burden (TMB) and those with evidence of tumor immune infiltration (i.e., higher cytolytic score, PD-L1 expression, or IFNγ gene signature scores). Clustering of gene expression profiles identified three tumor subgroups, including an "immune" subgroup associated with improved survival. Detection of BRAF V600 alterations in baseline ctDNA was associated with shorter survival; clearance of BRAF V600 alterations at cycle 2 day 1 was associated with improved survival across arms. CONCLUSIONS:The greatest benefits of encorafenib plus binimetinib were observed in patients with evidence of high TMB and/or tumor-immune infiltration, suggesting potential immune contributions to efficacy, which were not observed with vemurafenib. BRAF V600 detectability in ctDNA seems to have utility as a marker of prognosis and response in this population.

PFS and OS for encorafenib plus binimetinib or encorafenib vs. vemurafenib by (A and B) TMB and (C and D) cytolytic score. E, Volcano plots of univariable gene expression associations with OS in each arm based on z-scored gene expression values. F, Gene-set enrichment analysis of gene expression associations against hallmark gene signatures; signatures with greatest average NES across arms shown. Bini, binimetinib; BM, biomarker; CYT, cytotoxic score; Enco, encorafenib; NES, normalized enrichment scores; Vemu, vemurafenib.

LBA9517 Background: PIVOTAL (NCT02938299) is an open-label, randomized, multicenter, phase 3 trial evaluating daromun as a neoadjuvant intralesional (IT) therapy for resectable, locally advanced stage III melanoma. The trial enrolled 256 efficacy-evaluable patients (pts) in the EU and met its primary endpoint, demonstrating a statistically significant improvement in recurrence-free survival (RFS; HR = 0.59; p = 0.005) for daromun versus upfront surgery, at a median follow-up (FU) of 21 months from randomization (Kähler et al, Ann Onc 2025, 36, 1166). Methods: Pts with skin and/or lymph node metastatic melanoma amenable to complete surgical resection were randomized (1:1) to receive 4 weekly IT injections of daromun (13 Mio IU of L19IL2 and 400 μg of L19TNF) followed by surgery or upfront surgery alone. Prior surgery, radiotherapy (RT) and/or systemic therapies (ST) were permitted, as well as any approved adjuvant treatment post-surgery.The primary endpoint was RFS, the secondary endpoints included DMFS, OS and safety. An event-free survival (EFS) sensitivity analysis was conducted, considering progression to unresectable melanoma before surgery, recurrence of the disease, or death due to melanoma or treatment as events. Results: An updated primary outcome analysis at a median FU of over 36 months from randomization (database cut-off Nov. 29, 2025) confirmed a clinically relevant improvement in RFS (HR = 0.60; p = 0.003) for daromun versus upfront surgery. The EFS sensitivity analysis carried out in the overall population was consistent with the RFS results (HR = 0.66; 95% CI = 0.47-0.92).The PIVOTAL trial included two clinically distinct subgroups: pts with newly diagnosed disease (n = 32; 12%) and pts with recurrence(s) after surgery and/or systemic (neo)adjuvant treatment (n = 224; 88%). Among the recurrent cohort, 86 pts (38.3%) had received and failed previous ST, while 138 pts (61.6%) had only received surgery/RT. Sensitivity EFS analyses were also performed in i) the recurrent cohort (HR = 0.59; 95% CI = 0.41-0.85), ii) the subgroup of pts in the recurrent cohort who had only received previous surgeries and/or RT (HR = 0.55; 95% CI = 0.34-0.89), and iii) the pts subgroup in the recurrent cohort who received prior ST (HR = 0.63; 95% CI = 0.36-1.08 ). The rate and type of treatment-related adverse events at a longer FU were consistent with previous reports, and no new safety risks were identified. Conclusions: With longer FU the highly significant reduction in the risk of recurrence or death with neoadjuvant daromun in pts with locally advanced stage III melanoma is confirmed. The sensitivity EFS analyses provide consistent, confirmatory evidence of daromun’s efficacy across the entire trial population and, more importantly, in the subgroup of pts with recurrent disease, regardless of any prior ST. No new safety signals were reported. Clinical trial information: NCT02938299 .

2597 Background: RPx is an investigational HSV-1-based oncolytic immunotherapy platform including RP1 (vusolimogene oderparepvec) and RP2. RP1 expresses GM-CSF and a fusogenic glycoprotein (GALV-GP-R – ); RP2 also expresses an anti–CTLA-4 antibody-like molecule. We report safety data from patients (pts) who received intratumoral (IT) injections of RP1/2 into visceral metastases (mets). Methods: Pts with advanced/metastatic solid tumors were enrolled into RP1/2 clinical trials (RP1: NCT03767348; RP2: NCT04336241). RP1/2 was injected into visceral tumors using CT or ultrasound guidance. The recommended needle gauges ranged from 17-27G. Pts received RP1/RP2 for up to 8 doses as monotherapy or in combination with nivolumab IV starting at cycle 2 or 4 for up to 2 years. Additional RP1/2 doses could be given if protocol-specified criteria were met. This analysis evaluated safety among pts receiving IT RP1/2 injections to visceral mets (defined as lung or liver mets). All safety data presented includes events occurring within 7 days after injection (except where noted). Results: As of data cutoff (RP1: 15OCT2024; RP2: 29AUG2025), there were a total of 665 RP1/2 injections into the lung (n = 125; median lung injections/pt/treatment course [c]: RP1 = 5.5 and RP2 = 8) and liver (n = 540; median liver injections/pt/c): RP1 and RP2 = 5) among 105 pts. The most common treatment-related adverse events (AEs) were pyrexia, chills, and fatigue (Table). A total of 9 pneumothorax (PTX) events occurred (within 3 days after injection) out of 125 lung injections (7.2%) in 19 pts receiving RP1/2; all cases were Grade (G) 1/2 and resolved. Only 1 pt required a chest tube for a G2 PTX event and the pt continued to receive RP1 after resolution. There were 3 bleeding events within 3 days after injection among 665 injections (0.5%) in the lung or liver in 105 pts receiving RP1/2. All bleeding events occurred in pts receiving RP2 liver injections and resolved (2/3 events resolved by the following day). Conclusions: RP1/2 injections into visceral mets were well tolerated, with a comparable safety profile to liver and lung biopsies performed in other clinical settings. The observed RPx safety profile supports the incorporation of IT injections into deep visceral tumors as part of cancer therapy. Clinical trial information: NCT03767348 ; NCT04336241 . All-grade treatment-related adverse events (>15%). RP1 RP2 Monotherapy Combination therapy Monotherapy Combination therapy n (%) Injected visc mets (n = 11) Total (n = 19) Injected visc mets (n = 46) Total (n = 151) Injected visc mets (n = 14) Total (n = 20) Injected visc mets (n = 34) Total (n = 47) Pyrexia 9 (82) 12 (63) 22 (48) 51 (34) 6 (43) 9 (45) 18 (53) 25 (53) Chills 6 (55) 6 (32) 20 (44) 43 (28) 3 (21) 5 (25) 13 (38) 19 (40) Fatigue 3 (27) 7 (37) 8 (17) 39 (26) 1 (7) 3 (15) 4 (12) 7 (15) Influenza-like illness 1 (9) 2 (11) 12 (26) 31 (21) 0 0 2 (6) 8 (17) Nausea 1 (9) 1 (5) 13 (28) 26 (17) 1 (7) 1 (5) 5 (15) 8 (17) mets, metastases; visc, visceral.

Background Anti-programmed cell death protein 1 (PD-1) immunotherapy has revolutionized the treatment of stage III and IV melanoma. Real-world data on its resistance is needed to facilitate the development of combinatorial approaches to overcome anti-PD-1 resistance.Objectives To characterize anti-PD-1 resistance and assess whether progressive disease assigned by clinicians is concordant with scan data assessed by independent central reviewers (ICR).Methods A retrospective chart review was conducted in adult patients with stage III/IV melanoma who initiated anti-PD-1 therapy from January 2018 until 12 months before the start of data collection at 22 sites across six countries. Primary resistance and late relapse in the adjuvant setting, and primary, secondary resistance, and late progression in the advanced setting were assigned using Society for Immunotherapy of Cancer definitions. Demographic and clinical characteristics by type of resistance were compared with appropriate univariate tests. Time to resistance (TTR) and overall survival were analyzed using Kaplan-Meier. To compare the concordance of progression assigned by clinicians and ICR, the positive predictive value (PPV) was calculated in a subset of patients.Results Of 981 eligible patients, 738 were included. In the adjuvant setting (n=240), 53 (22.1%) patients developed primary resistance and 60 (25.0%) experienced late relapse. In the advanced setting (n=498), 222 (44.6%), 50 (10.0%), and 64 (12.9%) patients developed primary, secondary resistance, and late progression. Type of resistance significantly differed by country, race, type of BRAF mutation, and PD-L1 expression in both settings; and by sex, disease stage and tumor thickness in the adjuvant setting only (p<0.05). Mean (SD) TTR was 47.7 (1.3) and 24.2 (1.0) months in the adjuvant and advanced setting, respectively. Patients with primary resistance had the poorest overall survival. The PPV of progression assigned by clinicians was 87.2% (95% CI 72.6% to 95.7%).Conclusions This study showed that a substantial proportion of patients with melanoma receiving anti-PD-1 therapy in the adjuvant (47.1%) and advanced (67.5%) settings developed resistance or late relapse/progression, highlighting an unmet medical need. Real-world clinical practice provided a reliable assessment of progression. Factors associated with different types of resistance were identified. Further study is warranted to evaluate their impact on patient risk stratification. (Graphical abstract)

Characterization of tumor samples to identify candidate molecular subtypes by K-means clustering and distribution of subtypes by biopsy site. A, Heatmap showing K-means cluster and the expression of key marker genes (AXL and MITF) and cell type scores generated by xCell. B, Distribution of K-means subgroups across biopsy sites. C, OS by K-means subgroup and treatment arm. Bini, binimetinib; Vemu, vemurafenib.

BACKGROUND:Immune-Checkpoint-Inhibitors (ICIs) have significantly improved the course of advanced/metastatic melanoma and the concept of ICIs curative potential began to appear. To use statistical approaches to determine whether advanced/metastatic melanoma patients treated with nivolumab alone or in combination with ipilimumab may be considered as functionally cured. METHODS:Individual patient data were reconstructed from published Kaplan-Meier curves of the anti-PD1 arms of the Checkmate-067. The assumption of functional cure was assessed using three approaches based on a flexible-parametric survival model. Once the hypothesis of functional cure was confirmed, the time to functional cure (TTFC) was determined using an intuitive approach based on flexible survival model. RESULTS:The three complementary approaches were consistent and confirmed the functional cure assumption. The TTFC (the shortest time defined by fewer than 1% of patients progressing or dying) was estimated to be 61 (95%CI,50.7;79.4) and 63 m (95%CI,51.1;71.4) for nivolumab alone or in combination, respectively. CONCLUSIONS:We showed that metastatic melanoma patients, treated with the combination or nivolumab alone who were alive and had not progressed by the five-year time-point, can be considered as functionally cured. The robust statistical approach proposed could be applied to other clinical settings when the plausibility of cure is to be validated.

PFS and OS for encorafenib plus binimetinib or encorafenib vs. vemurafenib by (A and B) ERBB2 expression level and (C and D) PI3K pathway mutation status. Bini, binimetinib; BM, biomarker; Enco, encorafenib; Vemu, vemurafenib.

Daromun (L19IL2/L19TNF) was investigated as a neoadjuvant, intralesional therapy for patients with fully resectable stage III melanoma in the phase III PIVOTAL trial (ClinicalTrials.gov identifier: NCT02938299). The trial enrolled 256 patients in the European Union and met its primary end point, demonstrating a statistically significant improvement in recurrence-free survival (RFS; hazard ratio, 0.59; P = .005) for daromun followed by surgery versus up-front surgery, at a median follow-up (FU) of 21 months from random assignment. PIVOTAL included two clinically distinct subgroups, namely, patients with de novo diagnosed metastatic disease (n = 34; 13%) and patients with recurrence(s) after surgery with or without radiotherapy and/or adjuvant systemic therapies (n = 222; 87%). Here, we present an updated analysis of the primary and secondary end points, including safety data, at a median FU of 36.8 months from random assignment (database cutoff: November 28, 2025), alongside new sensitivity analyses of event-free survival (EFS). The updated analysis confirms the clinically and statistically meaningful improvements in RFS and distant metastasis-free survival recorded in the neoadjuvant daromun versus control arm. The EFS post hoc analysis, conducted in both the overall population and the recurrent patient subgroups (with or without prior systemic therapies), provides consistency and robustness to the benefit of neoadjuvant daromun observed for the primary efficacy end point. No new safety signals of concern were recorded.

Background Circulating tumor DNA (ctDNA) is a promising biomarker in melanoma, with higher sensitivity for tumor burden detection than conventional diagnostics. While well established in research, clinical routine implementation remains pending. Key global questions concern optimal clinical applications and barriers to adoption. Methods A web-based survey of 116 members of the Melanoma World Society Study Group assessed international expert opinions on ctDNA utility across predefined clinical scenarios. The questionnaire included 18 general questions on ctDNA use and 5 clinical vignettes with de-identified patient data and retrospectively obtained ctDNA results. Results ctDNA was rated most valuable for detecting minimal residual disease (mean score 3.63), surveillance of recurrent disease (3.85), and stage IV melanoma (3.82), with limited utility in early stages. Experts considered ctDNA superior to S100 and LDH for early relapse detection and identifying progressive disease. Most participants (80%) agreed that ctDNA correlates with radiographic response, and 82% favored its integration into routine follow-ups. In urgent high-tumor-burden settings, 82.8% would initiate BRAFi/MEKi therapy based on ctDNA if tissue analysis was pending, and 93.9% if unavailable. For central nervous system lesions, 62% did not support blood ctDNA, while 66% considered cerebrospinal fluid valuable. Pragmatic approaches with small to mid-size targeted panels and short turnaround times were preferred. Major barriers included the need for prospective trials (85%), standardized guidelines (83%), and reimbursement policies (82%). Conclusion Key opinion leaders regarded ctDNA as a valuable adjunct selected melanoma scenarios. Validation through prospective studies, guideline development, and reimbursement frameworks are essential for broader clinical implementation.

PURPOSE:Homologous recombination deficiency (HRD) results in DNA instability in tumor cells and contributes to tumor pathogenesis. Although HRD-directed therapies are established in other cancers, their role in skin cancers remains unclear. Given the poor response to standard therapies in skin cancer subtypes like acral and mucosal melanoma, we aimed to characterize the prevalence of HRD across skin cancer subtypes, evaluate its correlation with immune checkpoint inhibitor (ICI) response biomarkers, and assess its prognostic relevance in patients treated with immunotherapy (IO). METHODS:A total of 2,508 patients with skin cancer underwent molecular profiling including whole-exome sequencing, whole-transcriptome sequencing, and immunohistochemistry. HRD status was defined by a high loss of heterozygosity (LOH-high) or mutations in homologous recombination repair (HRR) genes. Associations between HRD and established ICI biomarkers (tumor mutational burden, PD-L1, deficient mismatch repair/microsatellite instability-high, immune cell fractions, and transcriptomic signatures) were assessed. Survival outcomes on ICI therapy were assessed in cutaneous melanoma using insurance claims data. RESULTS:Overall, among the melanoma subtypes, mucosal and acral melanoma had a greater prevalence of LOH-high than cutaneous (30.9% v 13.1% v 8.3%, P < .001). Generally, LOH-high in skin cancer did not correlate with mutations in HRR genes. Additionally, there was no significant association in ICI response biomarkers and HRD among patients with skin cancers. Furthermore, HRD was not associated with a prognostic advantage following IO (hazard ratio, 0.981 [CI, 0.80 to 1.20]; P = .854). CONCLUSION:HRD defines a biologically distinct subset of skin cancers and is not predictive of ICI response or improved outcomes. The high prevalence of HRD in acral and mucosal melanoma highlights the need to investigate HRD-directed therapies strategies in this distinct cohort, such as poly (ADP-ribose) polymerase inhibitors or platinum-based therapies.

9518 Background: Advanced melanoma has a high mortality rate; however, survival for patients (pts) treated with anti–PD-1–based therapy tends to plateau at 3–4 years, suggesting that pts alive at 3 years are likely to have prolonged benefit. This highlights the need for novel therapies that offer increased survival beyond 3-4 years. RP1 (vusolimogene oderparepvec) is an HSV-1–based oncolytic immunotherapy expressing GM-CSF and a fusogenic glycoprotein (GALV-GP-R − ). In the IGNYTE trial (data cutoff [DCO]: 15OCT2024), pts with advanced melanoma that had confirmed progression on anti–PD-1 therapy who received RP1 + nivolumab (nivo) had an objective response rate by RECIST 1.1 of 33.6% (16.4% complete response); median duration of response was 24.8 months. Here, we present a 3-year survival analysis of pts treated with RP1 + nivo from IGNYTE (last pt in: 9MAR2023; DCO: 11JUN2025). Methods: Pts ≥18 years with advanced melanoma and confirmed progression while being treated for ≥8 weeks with anti–PD-1 ± anti–CTLA-4 as the last prior therapy were enrolled (NCT03767348). An initial dose of RP1 was administered intratumorally (1 × 10 6 PFU/mL), followed by up to 7 doses every 2 weeks (Q2W; 1 × 10 7 PFU/mL) in combination with intravenous nivo 240 mg Q2W/480 mg Q4W for up to 2 years; additional RP1 was allowed if protocol-specified criteria were met. This updated analysis evaluated overall survival (OS) using the Kaplan-Meier (KM) method. Results: Of 140 enrolled pts, 49.3% had stage IVM1b–d disease, 55.7% had PD-L1–negative tumors, 46.4% had prior anti–PD-1 + anti–CTLA-4 therapy, and 65.0% had primary resistance to prior anti–PD-1 (ie, progression within 6 months of starting the immediate prior course of anti–PD-1). The median (95% CI) OS was 32.2 (25.8, 39.2) months (the median OS follow-up was 3 years by reverse KM method). OS rates (95% CI) at 1, 2, and 3 years were 75.3% (66.9%, 81.9%), 61.6% (52.5%, 69.4%), and 45.5% (35.8%, 54.7%), respectively. Importantly, among responders (n=47), the 3-year OS rate (95% CI) was 81.8% (65.2%, 91.0%) vs 22.5% (12.6%, 34.2%) for non-responders (n=93). The 3-year OS rates were 41.8% in pts with stage IVM1b–d disease (n=69), 37.2% for those with PD-L1–negative tumors (n=78), 37.4% in pts with prior anti–PD-1 + anti–CTLA-4 therapy (n=65), and 44.8% in pts with primary resistance to anti–PD-1 (n=91). The safety profile for RP1 + nivo remained consistent with prior reports; no new safety signals were seen. Conclusions: The 3-year landmark OS rate of 45.5% in the overall population and 81.8% among responders provides further evidence that the deep and durable responses provided by RP1 + nivo translate into long term clinical benefit, including extended OS in pts with melanoma post-confirmed progression on prior anti–PD-1–based therapy. Clinical trial information: NCT03767348 .

Abstract During their inevitable evolution towards acquired resistance to anti-cancer targeted therapies, cancer cells adopt distinct gene expression profiles that allow them to transiently adapt to and tolerate the treatment. Cancer cells surviving therapy can increase their mutation rate, enhancing the likelihood of acquiring resistance-conferring mutations and evolving into resistant cells. Here we show that translational control mediates the adaptive mutability of melanoma drug-tolerant cells by regulating the translation of the error-prone non-homologous end joining (NHEJ) component 53BP1 . The specific inhibition of 5’UTR-driven 53BP1 mRNA translation was sufficient to impair NHEJ and mutability. We found that the eIF4A RNA helicase, regulates 53BP1 mRNA translation. Consequently, targeting the eIF4A with two small molecule inhibitors significantly delays the acquisition of resistance to combination of BRAF and MEK inhibitors in BRAF V600 -mutant melanoma xenograft models and cell lines by reducing the mutability of drug-tolerant cells. Our results demonstrate that a standard-of-care therapy for melanoma, by engaging non-genetic adaptation driven at the translational level, contributes to the evolution of drug-tolerant melanoma cells toward acquired resistance.

9539 Background: Predictive biomarkers for immune checkpoint blockade (ICB) in advanced cutaneous melanoma (CM) remain limited. Imaging mass cytometry (IMC) enables spatially resolved profiling of the tumor microenvironment (TME) and can capture immune–tumor architecture beyond cell density. Methods: Patients with advanced CM treated with first-line ICB and available pretreatment FFPE tissue were analyzed using IMC (40-marker panel). The primary endpoint was durable 1-year clinical benefit (1y-CB: metabolic CR/PR or stable metabolic disease ≥12 months by PERCIST on FDG-PET/CT); the secondary endpoint was 1-year progression-free survival (1y-PFS). Cell densities, tumor marker expression, and spatial neighborhood metrics were evaluated. Reproducibility was assessed by re-analyzing an independent published IMC melanoma cohort (PMC8026677). Results: Twenty-nine patients (anti–PD-1 n=27; ipilimumab+nivolumab n=2); 15 achieved 1y-CB. 1y-CB was associated with higher leukocyte infiltration and increased densities of B cells, conventional CD4⁺ T cells (Tconv), CD8⁺ T cells, and plasma cells, whereas higher tumor density was associated with lack of benefit and inferior 1y-PFS (HR 10.57; p<0.001). Higher CD8⁺ and B-cell densities were associated with improved 1y-PFS (HR 0.26, p=0.013; and HR 0.26, p=0.047). Tumor PD-L1 and HLA-DR expression correlated with 1y-CB (p=0.022 and p=0.040). Spatial metrics further stratified outcomes: increased tumor–tumor proximity was associated with poor 1y-CB (p=0.0016), while increased B–Tconv proximity was associated with 1y-CB and longer 1y-PFS (HR 0.20; p=0.037). The strongest spatial association was macrophage proximity to HLA-DR⁺ tumor cells (p≤0.0001). In the external cohort (n=60), responder enrichment for Tconv/CD8⁺ T cells and macrophage proximity to HLA-DR⁺ tumor cells were reproduced. Conclusions: Pretreatment IMC identifies both compositional and spatial TME features associated with durable benefit from first-line ICB in advanced CM. T-cell enrichment and macrophage proximity to HLA-DR⁺ tumor cells emerged as reproducible candidate spatial biomarkers warranting prospective validation. Main predictors of 1y-CB and 1y-PFS. Parameters 1y-CB events/N 1y-CB p-value 1y-PFS HR (95% CI) 1y-PFS p-value B cells ≥9.5 5/15 vs 9/14 0.026 0.26 (0.00–0.99) 0.047 CD8⁺ T cells ≥36 7/20 vs 7/9 0.023 0.26 (0.00–0.76) 0.013 Plasma cells ≥1 3/12 vs 11/17 0.017 0.28 (0.08–1.00) 0.050 Tumor density ≥4194 5/5 vs 9/24 0.006 10.57 (3.08–36.23) <0.001 B–Tconv proximity ≥13.3% 2/10 vs 10/16 0.018 0.20 (0.00–0.91) 0.037 HLA-DR ≥58.4% 1/7 vs 13/22 0.040 0.17 (0.02–1.28) 0.085 PD-L1 ≥3.3% 8/20 vs 6/9 0.022 0.48 (0.16–1.38) 0.171

Baseline patient characteristics by biomarker status.

BACKGROUND:Cemiplimab an anti-programmed cell death receptor-1 antibody, was approved by the FDA and EMA for patients with locally advanced cutaneous squamous cell carcinoma (laCSCC) ineligible for curative surgery/radiotherapy or with metastatic (m) CSCC. TOSCA study evaluated the real-world effectiveness and safety of cemiplimab compared to historical systemic therapies (HSTs). METHODS:TOSCA (NCT05302297) was a large French retrospective, multicenter study comparing patient with la/mCSCC treated with cemiplimab via the early access program (EAP, 2018-2019) or HST (2013-2018). The primary endpoint was overall survival (OS); secondary endpoints were progression-free survival (PFS), duration of response (DoR), overall response rate (ORR), and safety. Effectiveness analysis using inverse probability weighting included a trial-like cohort of only immunocompetent patients meeting the EAP criteria to emulate a randomized clinical trial; safety analysis included all real-life patients. FINDINGS:The study included 280 real-life patients (cemiplimab: n = 147; HST: n = 133). The primary effectiveness analysis included a trial-like cohort (cemiplimab: n = 129; HST: n = 70; median age: 81 and 78 years, respectively). Median follow-up was 20 and 10 months in the cemiplimab and HST arms, respectively; median OS was 21.2 and 9.8 months, respectively (HR 95% CI: 0.57 [0.45-0.73]; P < 0.0001); median PFS was 13.7 and 5.3 months, respectively (HR [95% CI]: 0.57 [0.43-0.76]; P = 0.0001). Adverse drug reactions occurred in 27% of cemiplimab patients and 33% of HST patients. INTERPRETATION:TOSCA demonstrated better survival and response outcomes for cemiplimab versus HST in la/mCSCC; emphasizing, the importance of this retrospective studie in the absence of standard comparative trials.

Abstract Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment, but their efficacy has now reached a plateau. ICIs are the first class of treatment targeting the crosstalk between immune and tumor cells, making it crucial to understand the complex interactions within the tumor microenvironment (TME) to enhance therapeutic responses. The elevated consumption of resources by cancer cells, coupled with limited vascularization, often results in a TME that is deficient in nutrients, leading to competition for resources between cancer and stromal cells. Consequently, targeting tumor metabolism has emerged as a promising strategy to improve the efficacy of ICIs. Through metabolomic analysis, we have identified metabolic alterations in melanoma cells that are resistant to ICIs, specifically an increase in arginine synthesis and upregulation of ASS1, the rate-limiting enzyme in this pathway. By using gain and loss of function models, as well as a pharmacological inhibitor specific for ASS1, we demonstrated that modulations in the expression or activity of ASS1 is associated with translational reprogramming, characterized by an inhibition of the cap-dependent mRNA translation mediated through mTORC1/4EBP1 axis. We also demonstrated that targeting ASS1 in vivo , resensitize tumors initially resistant to ICI. Taken together, our results highlight the interaction between modulations of arginine synthesis pathway, mRNA translation reprogramming, antitumor immunity, and restauration of sensitivity to anti-PD-1. Our work also demonstrates the therapeutic potential of targeting arginine synthesis pathway, and especially ASS1, to offer new treatments to patients suffering from cutaneous melanoma resistant to ICIs.

9578 Background: In early-stage cutaneous melanoma (CM), AJCC staging demonstrates limited ability to identify patients at elevated recurrence risk who may benefit from adjuvant therapy or intensified surveillance. We evaluated DiaSurv, an AI-based prognostic assay analyzing standard H&E whole-slide images (WSI) to refine risk stratification in stage I-II melanoma. Methods: DiaSurv was validated on a retrospective cohort of 456 stage I-II primary CM patients with 5-year follow-up at Gustave Roussy. The algorithm assigns high- or low-risk scores based solely on primary tumor WSI analysis. Kaplan-Meier analysis estimated 5-year recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and overall survival (OS). Log-rank tests compared survival between risk groups. Multivariable Cox regression assessed independent prognostic value after adjusting for clinicopathological factors (Breslow thickness, ulceration, age, sex, tumor location, histological subtype, mitotic count). Results: Among 456 stage I-II patients (109 recurrences, 67 distant metastases, 57 deaths), DiaSurv classified 285 (62.5%) as low-risk and 171 (37.5%) as high-risk. Low-risk patients had significantly better 5-year outcomes compared to high-risk patients: RFS 92% vs 38% (HR = 7.71, 95%CI 4.86-12.23, p < 0.001), DMFS 94% vs 55% (HR = 10.39, 95%CI 5.31-20.36, p < 0.001), and OS 96% vs 71% (HR = 8.12, 95%CI 4.10-16.07, p < 0.001). In multivariable analysis, DiaSurv was independently associated with all endpoints (RFS: HR = 2.43, p = 0.006; DMFS: HR = 3.71, p = 0.002; OS: HR = 3.78, p = 0.003). In the clinically relevant stage I-IIA subgroup (n = 368), DiaSurv identified 86 patients (23.4%) with high-risk profiles despite favorable AJCC staging. These patients had markedly inferior outcomes compared to the 282 low-risk patients: 5-year RFS 71% vs 92% (HR = 4.85, p < 0.001), DMFS 77% vs 96% (HR = 5.48, p < 0.001), and OS 84% vs 96% (HR = 4.39, p < 0.001). The NPV of low-risk classification at 5 years in stage I-IIA was 92.2% for RFS, 96.5% for DMFS, and 96.5% for OS which is in line or superior to some commercially available gene-expression profiling assays. Conclusions: In early-stage melanoma (I-IIA), where adjuvant therapy is not currently standard, DiaSurv identifies nearly one-quarter of patients with a high-risk profile and significantly elevated recurrence rates. This AI-based assay provides actionable prognostic information beyond AJCC staging to guide decisions regarding adjuvant therapy consideration, sentinel lymph node biopsy, and surveillance intensity.