Citations

Abstract Malignant insulinomas are rare pancreatic neuroendocrine tumors characterized by excessive insulin secretion and a high propensity for metastasis, leading to challenging management. This study retrospectively analyzed 57 patients treated for malignant insulinoma at Mayo Clinic sites between 1992 and 2024, focusing on the efficacy of systemic therapies in improving hypoglycemic control and survival outcomes. The most commonly used therapies included somatostatin analogs (SSA), everolimus, capecitabine-temozolomide (CAPTEM), and peptide receptor radionuclide therapy (PRRT). PRRT demonstrated the highest efficacy in controlling hypoglycemia (93%), followed by CAPTEM (68%) and everolimus (62%). SSA, chemotherapy, and streptozocin were less effective, with hypoglycemic improvement seen in 37.5, 33.3, and 28.6% of patients, respectively. Overall survival (OS) was longest with SSA at 84.67 months, followed by CAPTEM at 81.67 months and everolimus at 74.07 months. PRRT demonstrated a median OS of 49.73 months. In contrast, chemotherapy and streptozocin-based therapies had significantly shorter OS times of 15.23 and 8.35 months, respectively. These findings highlight significant variability in systemic therapy efficacy for malignant insulinoma, with PRRT emerging as a promising treatment for refractory hypoglycemia and long survival. Cox regression analysis identified primary tumor resection and a history of benign insulinoma as associated with longer OS. Optimal sequencing of therapies remains unclear, and individualized treatment plans based on hypoglycemic burden and tumor characteristics are critical for improving survival and quality of life in these patients.

1114 Background: While treatment and management of TNBC has improved, there is a need for novel prognostic biomarkers to better inform outcomes and guide therapeutic options. ILF2 is a poorly characterized protein with pleiotropic functions that is highly expressed in TNBC. Here we evaluated the associations of ILF2 with 1) genomic and transcriptomic data, 2) tumor microenvironment (TME), and 3) clinical outcomes in TNBC. Methods: 15,544 breast cancer (BC) samples, including 3,038 TNBC, were tested by NGS (592, NextSeq; WES, NovaSeq) and WTS (NovaSeq; Caris Life Sciences, Phoenix, AZ). ILF2 -high (H) and ILF2 -low(L) TNBC were defined by respective quartiles. Immune cell fractions were estimated by WTS deconvolution (Quantiseq). Real world overall survival (OS) was obtained from insurance claims and calculated from tissue collection to last contact using Kaplan-Meier estimates. Statistical significance was determined by chi-square, Fisher’s exact, and Mann-Whitney U test with p-values adjustments (q < .05). Results: ILF2 expression (median Log2(TPM+1) was higher (all q < .05) in key subgroups: ductal compared to lobular carcinoma (6.4 vs 6.0); primary compared to metastatic BC (6.4 vs 6.3); African American compared to White (6.4 vs 6.3); basal compared to luminal A, luminal B, HER2 PAM50 subtypes (6.9 vs 5.8, 6.3, 6.3); and TNBC compared to HR+HER2+, HR-HER2+, HR+HER2- subtypes (6.7 vs 6.3, 6.4, 6.2). Biopsied tissues from primary TNBC (pTNBC) and metastatic TNBC (mTNBC) patients were stratified into ILF2- H and ILF2- L groups. In both mTNBC and pTNBC, ILF2- H groups had 1) higher percentage of young patients (age < 50) (pTNBC: 35.5% vs 19.8%; mTNBC: 28.1% vs 17.3%; all q < .05); 2) higher mutation frequency of TP53 (pTNBC: 94.5% vs 79.6%; mTNBC: 92.4% vs 74.4%), but lower frequencies for PIK3CA ( pTNBC: 5.1% vs 23.4% , mTNBC: 8.8% vs 27.4%), CDH1 ( pTNBC: 0.8% vs 6.1%; mTNBC: 2.8% vs 12.2%; all q < .05); 3) higher infiltration of NK cells (pTNBC: 3% vs 2.6%; mTNBC: 2.8% vs 2.6%), but lower infiltration of M2 Mφ (pTNBC: 2.5% vs 3.3%; mTNBC: 2.6% vs 3.2%) and Tregs (pTNBC: 1.5% vs 1.9%; mTNBC: 1.4% vs 1.7%; all q < .05); 4) higher expression levels of immune checkpoint ( CD274, PDCD1LG2, CTLA4, LAG3, HAVCR2, FOXP3, IDO1, CD276 , FC: 1.2-3.1; all q < .05), stem cell genes (C D44, NANOG, POU5F1, KLF4, ALDH1A1 , FC: 1.4-2.4; all q < .05), and drug efflux genes ( ABCC3, ABCC11, ABCC2, ABCB1, ABCG2, ABCC1 , FC: 1.1-4.5; all q < .05) compared to ILF2- L group. In pTNBC, ILF2- H had significantly shorter OS vs ILF2- L group (22.3 vs 28.9 months, HR 1.2 [95% CI 1-1.5], p = .03), but no significant differences were observed between mTNBC ILF2 groups (HR 1.1 [95% CI 0.93-1.3], p = .2). Conclusions: ILF2 -H TNBC patients showed differential genomic and transcriptomic alterations that relate to therapy resistance, immune suppressive TME, and shorter OS. Further studies are warranted to validate the effects of ILF2 upregulation on therapeutic efficacy.

Abstract Ischemic cardiomyopathy (ICM) is a leading cause of heart failure characterized by extensive remodeling of the cardiac extracellular matrix (ECM). While initially adaptive, ECM deposition following ischemic injury eventually turns maladaptive, promoting adverse cardiac remodeling. The strong link between the extent of fibrosis and adverse clinical outcomes has led to growing interest in ECM targeted therapies to prevent or reverse maladaptive cardiac remodeling in ICM; yet, the precise composition of the ECM in ICM remains poorly defined. In this study, we employed a sequential protein extraction enabled by the photocleavable surfactant Azo to enrich ECM proteins from left ventricular tissues of patients with end-stage ICM (n=16) and nonfailing donor hearts (n=16). High-resolution mass spectrometry-based quantitative proteomics identified and quantified over 6,000 unique protein groups, including 315 ECM proteins. We discovered significant upregulation of key ECM components, particularly glycoproteins, proteoglycans, collagens, and ECM regulators. Notably, LOXL1, FBLN1, and VCAN were among the most differentially expressed. Functional enrichment analyses revealed enhanced TGFβ signaling, integrin-mediated adhesion, and complement activation in ICM tissues, suggesting a feedback loop driving continued ECM deposition in the end-stage failing heart. Together, our findings provide a comprehensive proteomic landscape of ECM alterations in the end-stage ICM myocardium and identify promising molecular targets for therapeutic intervention.

e19503 Background: The uptake of BCMA directed ADCs in MM has been hindered by ocular toxicity. Belantamab mafodotin (BM) and MEDI2228 (MEDI) are BCMA directed monoclonal antibodies conjugated to the microtubule inhibitor, monomethyl auristatin F and the alkylator, pyrrolobenzodiazepine, respectively. Differences in the ADCs payload, antibody specificity and linker stability influence ocular toxicity. We investigated the patterns of ocular toxicity and tolerability of BCMA directed ADC therapy. Methods: Retrospective study of MM patients who commenced treatment with a commercial or investigational BCMA directed ADC at the Mayo Clinic between 2019-22. Results: 111 patients were included, the median age was 69 and median follow up 40 months. The median number of prior treatments was 6, 87% of patients were triple class refractory, 50% penta class refractory, 14% had prior BCMA directed therapy and 24% had extraosseous disease. Treatments included BM (n=56, 50%), BM in combination with other MM therapy (n=12, 11%) and MEDI (n=43, 39%). The overall response rate was 30% for BM and 44% for MEDI. The median OS and PFS for BM was 8 and 2 months, the median OS and PFS for MEDI was 11 and 5 months. The median number of ADC cycles was 2.5. Ocular toxicity is summarized in the table 1. Keratopathy was more common with BM (p=0.004). Only 4 MEDI patients developed keratopathy, all grade 1 and associated with dry eyes and/or photophobia. In contrast, 60% of BM patients developed keratopathy (13% grade 3-4 keratopathy). The median time to keratopathy onset was 1 month with BM, and 2.8 with MEDI. The median time until keratopathy was 4.6 months for BM. Loss of best-corrected visual acuity (VA) was significantly more common with BM (p<0.001). The median time to any decline in VA was 1.5 months for BM and 2.3 for MEDI. The median time until VA returned to baseline was 2.4 months for BM and 2.3 for MEDI. The frequency of dose delays for ocular toxicity was comparable between ADCs, as was the number of dose reductions (16% BM vs. 12% MEDI, p=0.5). The most common reasons for treatment discontinuation were progression or death (BM=69%, MEDI=44%) and ocular toxicity (BM=18%, MEDI=30%). Conclusions: Treatment interruptions, dose reductions and drug discontinuation are common with BCMA directed ADC therapy. Further research to optimize the administration schedule of these agents is warranted. BM and MEDI produce distinct patterns of ocular side effects, namely keratopathy and reduced VA with the former, and photophobia and dry eyes with the latter. BM N = 68 MEDI N = 43 p-value 2 Prophylactic steroid eye drops 4 (6%) 28 (68%) <0.001 Prophylactic lubricant eye drops 42 (63%) 33 (80%) 0.051 Max grade keratopathy 0.004 1-2 29 (47%) 4 (19%) 3-4 8 (13%) 0 (0%) VA equal or worse than 20/40 26 (68%) 6 (20%) <0.001 Days of ADC treatment 59 (33, 167) 68 (41, 105) 0.9 Dose delay for ocular toxicity 19 (28%) 8 (19%) 0.2 n (%); Median (IQR); 2 Chisq test; Wilcoxon rank sum.

6037 Background: The incidence of HPV-associated head and neck squamous cell carcinoma (HNSCC) continues to rise with over 90% of cases being driven by HPV16. Median overall survival (OS) with pembrolizumab in first-line recurrent/metastatic (R/M) HNSCC is 12.3 months in subjects with CPS ≥1, 10.8 months for CPS ≥1-19, and 14.9 months for CPS ≥20. There is an urgent need to improve survival rates in the growing population of HPV16-positive R/M HNSCC. PDS0101 (Versamune HPV) is an investigational T cell stimulating immunotherapy that unleashes a potent, durable attack against HPV16-positive cancers and is being studied in combination with pembrolizumab. Preliminary results were presented at ASCO 2023. (Price KAR, et al. ASCO 2023. Abstract 6012). Methods: VERSATILE-002 is a single-arm phase 2 study evaluating PDS0101 and pembrolizumab for first-line HPV16-positive R/M HNSCC with CPS ≥1. Subjects received pembrolizumab 200 mg IV Q3W with PDS0101 1 mL SC administered concurrently during Cycles 1, 2, 3, 4, and 12 and pembrolizumab alone for all other Cycles up to Cycle 35 (approx. 2 years). The primary study endpoint is confirmed objective response rate (ORR) per RECIST 1.1. Secondary endpoints include progression-free survival (PFS), OS, and safety. Results: The median follow-up is 18.4 months (range 0.2-42.7 months). The efficacy population consists of 53 subjects: 32 (60%) with CPS ≥1-19 and 21 (40%) with CPS ≥20. The median OS for subjects with CPS ≥1 is 30 months (95% CI 23.9, NE). For the CPS ≥1-19 subgroup, the median OS is 29.5 months (95% CI 15.3, NE). For the CPS ≥20 subgroup, the median OS is 39.3 months (95% CI 18.4, NE). Confirmed response rates by investigator assessment are shown in the Table. Twenty-three subjects are still on study: 3 on treatment and 20 in long-term follow-up. No new safety signals have emerged. The most common TRAEs are injection site reactions, fatigue, headache, and pruritus. Only 19% of subjects experienced Grade ≥3 TRAEs. No subject had a Grade 5 TRAE. Conclusions: These data represent one of the most extended follow-up periods to date of subjects receiving an HPV16-targeted therapy for HPV16-positive R/M HNSCC. The PDS0101 and pembrolizumab combination is well tolerated and has demonstrated deep and durable clinical responses. Median OS is promising in light of historic expectations, both overall and relative to PD-L1 subgroup, and remains durable with continued follow up. The results support further evaluation in a randomized phase 3 study with OS as the primary endpoint. Clinical trial information: NCT04260126 . Summary of results. CPS ≥1-19 (N=32) CPS ≥20 (N=21) CPS ≥1 (N=53) ORR, % 28.1 47.6 35.8 DCR, % 75.0 81.0 77.4 Median DOR, months (95 % CI) 21.8 (4.2, NE) NE (5.6, NE) 21.8 (11.5, NE) Median PFS, months (95% CI) 5.1 (2.4, 8.1) 14.1 (2.1, NE) 6.3 (3.5, 9.0) Median OS, months (95% CI) 29.5 (15.3, NE) 39.3 (18.4, NE) 30.0 (23.9, NE)

529 Background: Neoadjuvant chemotherapy (NAC) is commonly administered to patients (pts) with estrogen receptor alpha (ER) negative (immunohistochemistry [IHC] 0%) and ER-low (IHC 1-10%) breast cancer (BC). For pts without pathological complete response (pCR), ER expression may differ between baseline and residual BC following NAC. We previously demonstrated adjuvant endocrine therapy (ET) omission in ER-low early-stage BC was associated with significantly worse overall survival (OS); however, this effect was restricted to pts with residual BC following NAC and those with higher baseline ER levels (IHC 6-10%) (Choong et al., ASCO 2024). Here, we assessed how often ER was expressed in residual invasive BC for pts treated with NAC for ER-negative and ER-low BC. Methods: Weidentified pts with pre-treatment (tx) ER-negative and ER-low (regardless of HER2 expression) stage I-III BC treated with NAC who underwent BC surgery at Mayo Clinic Rochester between 2009 and 2023. ER IHC was performed in a CAP/CLIA laboratory. We evaluated ER expression in residual invasive BC for pts without pCR. The percent of pts with a post-tx change in ER status was estimated and reported with 95% Wilson confidence intervals. Results: 955 pts (838 [88%] pre-tx ER-negative; 117 [12%] pre-tx ER-low) met inclusion criteria, of whom 69% had HER2-negative and 31% HER2-positive BC. The median age at diagnosis was 52 (range: 24-86). 496 (52%) had residual BC. Residual BC was more common in HER2-negative versus (vs) positive tumors (56% vs 42%, p < 0.001) but did not differ significantly by ER status (ER-negative 51% vs ER-low 57%, p = 0.22). Of those with residual BC, 277/496 (56%) had ER re-testing. Rates of ER re-testing did not vary for pre-tx ER-negative vs -low (57% vs 51%, p = 0.37) but were significantly lower for HER2-positive vs HER2-negative tumors (39% vs 62%, p < 0.001). Among those with post-tx testing, 31/277 (11%, 95% CI: 8-15%) had an increase in ER expression from pretreatment levels (defined as ER IHC < 1% to either 1-10% or > 10%; or ER IHC 1-10% to > 10%). In these 31 pts, the original NAC was for either TNBC (21/31; 68%) or HER2+ BC (10/31; 32%). In pts with pre-tx ER-negative BC, 27/243 (11%, 95% CI: 8-16%) had ER expression in the residual BC including 14/243 (6%, 95% CI: 3-9%) with ER > 10% and 13/243 (5%, 95% CI: 3-9%) with ER 1-10%. For pts with baseline ER-low BC, 4/34 (12%, 95% CI: 5-27%) had ER > 10% in the residual BC. Among the 31 pts where ER increased following NAC, 21/31 (68%) received adjuvant ET, including 17/18 if ER was > 10% in the residual disease and 4/13 in those with ER 1-10%. Conclusions: In pts treated with NAC for ER-negative or ER-low BC not achieving pCR, we identified higher ER expression in the residual breast cancer in > 10% of pts. Given that omission of ET in ER-low BC with residual cancer following NAC is associated with worse survival, repeat biomarker testing should be considered in those without pCR, and ET individualized according to ER expression.

TPS2689 Background: Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. However, existing FDA approved companion diagnostic biomarkers like PD-L1, dMMR/MSI-H and TMB have low accuracy in predicting response. Ex vivo cytokine profiling of live tumor samples has shown promise as an improved means of predicting response to PD-1 blockade (Voabil, et al. Nat Med. 2021), but this approach has been limited to tumor resections given the need for large amounts of tissue. Here we present three clinical trials that leverage a novel approach using limited tissue from a single core needle biopsy (CNB) (20 gauge or larger). A sequential ex vivo treatment strategy is used, eliminating the need for a separate control arm and addressing challenges with tumor heterogeneity, particularly in CNBs where tissue is limiting. Using a specialized instrument, CNBs are cut into live tumor fragments (LTFs) which are viable in culture and retain the native tumor microenvironment, enabling cytokine profiling in response to ICI treatment ex vivo. Methods: ELEPHAS-01 (NCT05478538), ELEPHAS-02 (NCT05520099) and ELEPHAS-04 (NCT06349642) are observational prospective clinical trials initiated to characterize the accuracy of this approach for predicting ICI response. Over 750 patients that are being considered for standard of care (SOC) ICI therapy in the metastatic/relapse or neoadjuvant setting will be enrolled (Table). Fresh live CNBs are collected prior to treatment start and processed within 24 hrs enabling prediction of results within 72 hrs of receipt. LTFs are treated using a strategy where control (IgG) and SOC ICI treatments are performed sequentially on the same tissue in a single well. Changes in the cytokine secretion rates are then compared between ICI and control to characterize immunotherapy response. Additionally, tissue viability and tumor content measurements are used to assess tissue quality. Clinical response is measured using pathologic response in patients receiving neoadjuvant ICI therapy, while RECIST v1.1 is used in all other patients. The primary objective of these trials is to determine the platform’s ex vivo accuracy (e.g., sensitivity, specificity) for predicting clinical response to ICIs and comparing it to the accuracy of PD-L1, dMMR/MSI-H and TMB. Clinical trial information: NCT06349642 , NCT05478538 , NCT05520099 . ELEPHAS-01 (Lung) ELEPHAS-02 (Hoosier) ELEPHAS-04 (Mayo) Setting Metastatic & recurrent Metastatic & recurrent Metastatic, recurrent & neoadjuvant Tumor type Lung Bladder, kidney, colorectal, head and neck, lung, melanoma, endometrial Metastatic/recurrent: lung, skin, esophageal, cervical, endometrial, colon, liver, kidney, bladder Neoadjuvant: breast–TNBC, lung Enrollment as of 1/27/2025 26 44 20 Est. total enrollment 216 216 324 Clinical endpoints RECIST v1.1 RECIST v1.1 RECIST v1.1 & Pathologic response at surgery

10512 Background: Polygenic risk scores (PRSs) combine information from single-nucleotide polymorphisms (SNPs) across the genome to explain substantial genetic breast cancer (BC) susceptibility. Previous studies have demonstrated that a multiple-ancestry PRS (MA-385) based on 56 ancestry-informative and 329 BC-associated SNPs is accurate for diverse populations and ranks among the most important known factors affecting the risk of BC development. However, medical guidelines call for more evidence before endorsing the clinical use of PRS, including studies to evaluate possible interactions of SNPs with environmental and hormonal risk factors. Here, we use longitudinal outcomes from the UK Biobank (UKB) to explore interactions of MA-385 and the five most informative individual BC-associated SNPs with the widely used Tyrer-Cuzick (TC) risk model and individual TC risk factors. Methods: The study cohort included 197,509 female UKB participants with no history of cancer at the time of study enrollment. We used Cox proportional hazards models to test associations of MA-385, individual BC SNPs, TC, and individual TC risk factors with BC outcomes. Effect modification of MA-385 and individual SNPs by clinical risk factors was evaluated by including interaction terms in the models. All models were adjusted for age at UKB enrollment and 10 principal components. Hazard ratios (HRs) and 95% confidence intervals (CIs) are reported per standard deviation, and significance tests were performed using two-sided p-values based on likelihood-ratio test statistics. Results: After a median follow-up of 11.8 years, 7,419 (3.8%) participants were diagnosed with BC.In a model including both MA-385 and TC, MA-385 was a significantly better predictor of BC development (HR = 1.56; 95% CI 1.53-1.60, p = 3.2 x 10 -329 ) over the TC model (HR = 1.21; 95% CI 1.18-1.23; p = 5.4 x 10 -69 ). We found no evidence of interaction between MA-385 and TC ( p = 0.31) , nor between individual SNPs and TC. After Bonferroni adjustment for multiple testing (102 tests), we found no evidence of interaction between MA-385 or individual SNPs with clinical TC factors. The strongest evidence for interaction was found between a BC SNP on chromosome 2 (rs13387042) and age at UKB enrollment (unadjusted p = 0.002; Bonferroni adjusted p = 0.23). Conclusions: In a longitudinal analysis of UKB, MA-385 was a highly significant predictor of BC risk and substantially improved prediction over TC. In contrast, interactions of MA-385, and individual BC SNPs, with TC and individual clinical factors in the TC model were not statistically significant. Clinical TC factors have minimal, if any, impact on the strength of the association between MA-385 and BC. These results may help to alleviate concerns expressed in guidelines that SNPs interact with environmental or hormonal risk factors.