Jones, Jeremy C

Abstract Background: Pancreatic ductal adenocarcinoma (PDA) is a disease with guarded prognosis with a 5-year overall survival (OS) of 3.1% in patients with metastatic disease. The need for innovative treatments for this lethal disease is paramount. TTFields is a novel treatment modality that employs low intensity, alternating, and intermediate frequency electrical fields that abrogates cancer cell proliferation through different mechanisms. These include inhibition of mitosis, disruption of cancer cell membranes, metabolomic dysregulation of cancer cells, and immunogenic activation of the tumor microenvironment (TME). TTFields are approved in glioblastoma multiforme, non-small cell lung cancer and malignant mesothelioma. The PANOVA trial demonstrated promising efficacy for TTFields plus chemotherapy in patients with PDA. A trial of GCN in patients with PDA demonstrated exceptional efficacy in patients with metastatic disease. Here in, we present our ongoing clinical trial investigating the safety and efficacy of TTFields plus GCN in patients with PDA (NCT04605913). Methods: This a phase I/II trial with an initial safety run-in phase followed by the phase II portion. The primary objective of the trial is to determine the safety (CTCAE v 5.0) of GCN plus TTFields. Secondary objectives include determining the 6-month progression free survival (PFS) rate, overall response rate (ORR, RECIST v1.1), 12-month survival rate, OS, and QOL (EORTC QLQ-C30, version 3.0.2.3). Inclusion criteria include PDA with liver metastasis (patients can have additional sites of metastasis), ECOG 0-1, measurable disease, and ability to operate the Novo TTF-100L (P)/Novo TTF-200T system. Treatment consisted of TTFields (150 kHz 18 hours/day) and GCN (G: 1000 mg/m2, C 30 mg/m2, and N: 150 mg/m2 every 2 weeks, 28 days cycle), followed by a maintenance phase after 6 months (G: 1000 mg/m2 every 2 weeks) plus TTFields until progression. Six patients were to be enrolled in the phase I portion and if ≤1/6 patients experienced a dose limiting toxicity (DLT, treatment emergent adverse event, or skin toxicity of Gr4), the plan would be to move to a phase II trial enrolling 34 more patients. If 2/6 patients experienced a DLT, 6 patients would be enrolled in dose level -1 (GCN plus TTFields for 9 hours/day followed by the maintenance treatment) and if tolerated the phase II portion would start with dose level -1 regimen. The phase I portion was completed without any DLTs and the trial is currently enrolling to the phase II portion. The total number of patients (40) was powered to the 6-months PFS rate and ORR (estimated using the lower bound of exact one-sided 90% confidence intervals). The goal is to "reject" a 6-month PFS rate of 66% and an ORR of 71% (based on previous GCN trial). Time-to-event endpoints will be assessed using the Kaplan-Meier method. Citation Format: Hani M. Babiker, Jason Starr, Jeremy Jones, Conor O’Donnell, Robert Jones, Jacqueline Boni, Lashundra Stewart, Josh Cameron, Oudom Kour, Kabir Mody, Robert R. McWilliams, Daniel H. Ahn, Tanios Bekaii-Saab, Mitesh J. Borad, Umair Majeed. A phase I/II pilot trial, single arm, open label, of gemcitabine, cisplatin, protein-bound paclitaxel (GCN) combined with Tumor Treatment Fields (TTFields) in patient with metastatic pancreatic adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr CT190.

727 Background: PARP inhibition (PARPi) is a standard maintenance therapy for patients (pts) with germline BRCA1/2 mutations in pancreatic cancer. Combination of PARPi therapy and immunotherapy has potential to increase efficacy and may offer benefit beyond germline BRCA1/2 . Methods: We performed a multisite single-arm phase 2 study using the highly potent PARPi niraparib with anti-PD1 drug dostarlimab in pts with germline or somatic HRD mutations in BRCA1/2, PALB2, RAD51C/D, or BARD1 . Pts were required to have metastasis, progressed on ≥1 regimen, and prior platinum-exposure unless refused/intolerant. Pts were treated with niraparib 200 mg orally once daily continuously. Dostarlimab 500 mg was administered IV every 3 weeks for 4 cycles, then 1000 mg IV every 6 weeks. The primary endpoint was disease control rate (DCR) at 12 weeks (DCR12) using iRECIST criteria. At least 8 pts with DCR12 in the first 19 eligible pts (41%) would be considered promising for further trials. Results: 22 pts were enrolled from Dec 2020 to Oct 2023. Two pts withdrew prior to receiving therapy, and 2 were later found to be ineligible, leaving 18 eligible pts for final analyses. Median age was 63.0 yrs, 39% male, 94% non-Hispanic white, 1 black (6%). 17 pts were platinum exposed, 7 were platinum-refractory, and 5 had previously progressed on PARPi maintenance. Mutation distribution was: BRCA2 13/18 (72%), BRCA1 4/18 (22%), BARD1 2/18 (11%). One pt had both BRCA1 (somatic) and BRCA2 (germline) mutations. Germline mutations were identified in 14/18 (78%). DCR12 was achieved in 5/18 (27.8%), so the primary endpoint (>41%) was not met. Pts received a median 2 cycles (range 1-8) of niraparib + dostarlimab. No clinical factors were significantly associated with improved DCR12 (all p > 0.05) in subgroup analyses, but we did observe the following statistically nonsignificant associations. Pts who were platinum-refractory had a lower DCR12 compared to those not (14.3% vs. 36.4%). Counterintuitively, PARPi exposed/refractory pts had a higher DCR12 than non-exposed/non-refractory (50 vs 17% exposed/nonexposed and 40% vs 23% refractory/nonrefractory). Pts with germline mutations had a higher DCR12 compared to those without (38.5% vs. 0%). Non- BRCA2 mutations had a higher DCR12 than those with BRCA2 mutations (50% vs.17%), with highest DCR12 rates among BRCA1 patients (67%). Tolerability was in line with similar combinations, with 60% non-hematologic Gr3 or higher, including fatigue (15%), AST increase (10%), nausea/vomiting (10%), sepsis (10%). Two grade 5 events were not attributed to treatment. Conclusions: PARPi plus anti-PD1 checkpoint inhibition was not sufficiently active as later line therapy in metastatic pancreatic cancer for the majority of patients with HRD mutations. Additional molecular analyses to elucidate predictive markers of sensitivity/resistance are ongoing. Clinical trial information: NCT04493060 .

10 Background: Cell-free circulating tumor tissue modified viral DNA (ctDNA) has been used as a biomarker to detect recurrence for anal squamous cell carcinoma (ASCC). However, its value in informing treatment modification during definitive chemoradiation (CRT) has yet to be explored. We evaluated ctDNA response during and at completion of definitive CRT to establish patterns of disease response and inform future studies to personalize treatment. Methods: From 11/2022 to 6/2024, 13 consecutive patients with biopsy proven, non-metastatic ASCC received definitive CRT and had ctDNA testing using a commercially available droplet digital quantitative PCR assay. ctDNA testing was done at baseline (pre-CRT), week 4 of CRT, and/or end of CRT, 1-3 months post-CRT, and every 6 months thereafter. CRT included concurrent 5FU/MMC (or capecitabine/MMC) and radiotherapy according to RTOG 0529. Treatment response assessment included: physical exam, anoscopy, and imaging with PET/CT, CT C/A/P +/- MRI abdomen and pelvis. Results: 13 patients had ctDNA testing and 11 patients had HPV-positive ASCC and tested positive for ctDNA. The 11 patients with detectable baseline ctDNA were included in this analysis. The median age at diagnosis was 63 years old. Staging included: 1- Stage IIA, 7- Stage IIB, 1- Stage IIIA, 2- Stage IIIC. 1 patient was cN0, while 11 were cN1. With a median follow-up from completion of CRT of 13 months, 4 patients have persistent or recurrent disease: 2 with distant metastases, 1 with persistent local disease (1 month post-CRT), and 1 with local and distant recurrence. Baseline value of ctDNA did not correlate to stage at diagnosis, rate of clearance during CRT, or likelihood of recurrence. 5 of 11 patients cleared ctDNA by week 4 of CRT. Of 5 patients who cleared ctDNA by week 4 of CRT, 4 remain NED and 1 developed distant metastases. Of 6 patients with persistent ctDNA at week 4 of CRT, 3 have persistent or recurrent disease- 1 local persistence 1 month post-CRT, 1 local and distant recurrence 6 months post-CRT, and 1 with distant recurrence 12 months post- CRT. Among 6 patients who cleared ctDNA by the final week of CRT, 1 patient developed recurrent disease. Among the 4 patients in the series with residual/recurrent disease, 3 of them had not cleared ctDNA by the end of CRT. Of 10 patients with ctDNA testing at 1 month post-CRT, 8 had no detectable ctDNA. 2 patients with persistent (1) or recurrent (1) ctDNA at 1 month post-CRT developed disease recurrence- 1 with distant recurrence and 1 with local and distant recurrence. Conclusions: ctDNA assessment during CRT may provide insight into disease response that can predict patterns of failure and facilitate personalized therapy- treatment intensification, deintensification, or additional testing to detect early metastatic disease. Larger studies and clinical validation are needed.

163 Background: CRC with PM has a poor prognosis and limited treatment options. Immunotherapy has shown promise in improving outcomes for patients with microsatellite instability-high (MSI-H), mismatch repair-deficient (dMMR), and high tumor mutational burden (TMB-H) tumors. However the peritoneal niche has a unique microenvironment, which can influence the effectiveness of immune check point inhibitors (ICIs). We assessed the impact of ICI on progression-free survival (PFS) and overall survival (OS) in CRC patients (pts) and PM, considering key clinical and molecular characteristics. Methods: A retrospective review aiming to identify CRC pts with MSI-H/dMMR and PM treated with immunotherapy between 2015 and 2023 was performed. Data collected included pt demographics, tumor characteristics, and treatment details. Responses were evaluated using RECIST v1.1 criteria. Results: 37 pts were included, 9 (24%) had Lynch syndrome. The median age of diagnosis was 61 years and most pts were females (65%). Most pts had MSI-H/dMMR tumors, while one pt was treated based on ultra-hypermutated phenotype (TMB 202) and POLE mutation. Among those with available TMB data, the median TMB was 52 mutations/Mb (0-202). Common mutations were PMS2 (51%), MLH1 (38%), MSH6 (16.2%), and MSH2 (16.2%). Right-sided tumors were in 54%, mucinous histology in 62%, and ascites in 54%. Pts received a median of 11 cycles of ICI (2-52). Pembrolizumab was the most frequently used ICI (78%), while Nivolumab was used either alone (11%) or in combination with Ipilimumab (11%). Median PFS in our cohort was 7.8 months and median OS was 29.9 months. The disease control rate (DCR) was 81%, with an objective response rate (ORR) of 51.3% (9 complete responses, 12 partial responses). At the time of data collection, 30% of pts were off systemic therapy and 5-FU-based chemotherapy combined with a biologic agent was the most common subsequent treatment in 32% who had PD. Univariate analysis showed no significant differences in PFS or OS based on tumor sidedness, isolated PM, liver metastases, mucinous vs. non mucinous histology or BRAF / RAS status (WT vs mutant). Malignant ascites was associated with worse OS(HR 0.3; p= 0.03). Conclusions: Treatment with ICIs in pts with MSI-H/dMMR and/or TMB-H CRC and PM improved disease control in CRC pts with PM, however, as compared to historical controls for patients with MSI-H/d-MMR disease treated with ICI, this group showed less favorable outcomes. Malignant ascites was associated with poorer overall survival. Further research of the immune response and tumor microenvironment in the peritoneal cavity is warranted.

Background/Objectives: Multi-gene, multi-cancer, hereditary cancer risk screenings may be useful in cancer prevention and treatment, not only for cancer patients but also for patients’ family members. If genetic cancer screening is to have the widest possible benefit, it must be extended into diverse cancer care settings that serve diverse patient communities, providing cancer patients and their relatives with individualized cancer risk evaluations. Little research, to date, has examined the impact of extending multigenic cancer screening into diverse settings. Without empirical data characterizing the support needs of cancer patients and their family members, we may not adequately satisfy the needs of all patients and risk exacerbating existing disparities in cancer care and outcomes. Methods: We examined patient perspectives on the sharing of genetic results with at-risk family members by surveying a racially diverse sample of cancer patients receiving a multi-gene, multi-cancer risk screen in a community hospital setting. Results: In a survey of 230 cancer patients, we found that intent to share results with family members was high but varied across family member types. More respondents planned to disclose results to at least one sister (82.5%) compared to at least one brother (73.1%). Over one-fourth of participants (27.4%) were either uncertain about sharing or intended to withhold their genomic screening results from at least one at-risk family member eligible for cascade testing. Participants were more likely to withhold their results from a sibling than from a child. Furthermore, intent to share across all family member types was lower if probands failed to identify at least one benefit to sharing. Conclusions: Understanding factors associated with decisions to share results with at-risk relatives in diverse patient populations can help clinicians support cascade genetic cancer screenings in diverse communities and settings.

3594 Background: The efficacy of checkpoint inhibitor immunotherapy in MSI-H mCRC has not been replicated in MSS mCRC. Therefore, additional interventions are needed to convert immunologically “cold” MSS CRC to “hot” tumors resembling MSI-H tumors. PolyPEPI1018 is an off-the-shelf, multi-peptide vaccine containing 12 immunogenic epitopes derived from 7 shared tumor antigens which demonstrated early evidence of clinical activity in first-line MSS mCRC. Methods: Patients with MSS mCRC who have progressed on 2-3 lines of prior chemotherapy regimen received PolyPEPI1018 (1.2 mg, sc) and atezolizumab (1,200 mg, iv) Q3W until disease progression or unacceptable toxicity. The primary endpoint was safety. A Simon 2-stage design was applied. Data on objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and correlation studies will be presented. Results: 18 patients (66 % female) were enrolled for stage 1 of the study. Median age was 54 years (range 38–79), 50% had liver metastases and 67% received at least 3 lines of prior therapies. PD-L1 expression was <1% for 85% of patients. The combination was well-tolerated; most common side effect related to treatment was Grade (Gr) 1-2 local skin reaction (n=22). Gr 2 events (n=2) at least possibly related to treatment were nausea, pyrexia and increased blood alkaline phosphatase. There were no Gr 3-5 events or study discontinuation due to treatment AE. The ORR was 0% and the DCR was 61%. The mPFS was 2.7 months (95%CI 1.4-4.0) and the mOS was not reached (95%CI 8.75 – NE months) at the data cut-off date. Ex-vivo FluoroSpot identified 13/16 subjects with robust, vaccine-specific CD8+ and/or CD4+ T cell responses detected against multiple vaccine antigens. For patients with available biopsy pairs (n=8), both the average PD-L1 expression (IC%, p=0.029) and the density of CD8+ tumor-infiltrating lymphocytes (TILs, p=0.019) were significantly increased, post-treatment. Patients with increased PFS (> 12 weeks) had both higher levels of post-treatment PD-L1 (p=0.007) and TILs (p=0.016) than patients with PFS ≤ 12 weeks. Conclusions: PolyPEPI1018 in combination with atezolizumab was well-tolerated with no Grade 3 AEs observed. Despite no objective tumor responses could be detected, correlative data suggest contribution of PolyPEPI1018-induced immune responses to the modulation of tumor microenvironment and to improved disease control. The study did not proceed to stage 2; it is on-going for the collection of survival data. Clinical trial information: NCT05243862 .

TPS228 Background: Colorectal cancer (CRC) is the third most frequently diagnosed cancer and the second leading cause of cancer-related mortality worldwide. PD-1/PD-L1 inhibition, in combination with other modalities, has demonstrated significant benefit in patients (pts) with microsatellite instability-high or mismatch repair–deficient CRC. However, these agents have limited, if any, clinical benefit in pts with microsatellite stable (MSS) or mismatch repair–proficient (pMMR) CRC. RP2 is an enhanced potency oncolytic herpes simplex virus type 1 which expresses the fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R–), granulocyte-macrophage colony-stimulating factor (GM-CSF), and an anti–CTLA-4 antibody-like molecule; RP3 additionally expresses 4-1BB and CD40 activating ligands but does not express GM-CSF. Both agents have demonstrated preliminary safety and antitumor activity in pts with solid tumors. This study will evaluate the safety and activity of RP2 and RP3 in combination with atezolizumab (Atezo) plus bevacizumab (Bev) in pts with advanced MSS/pMMR CRC (NCT05733611). Methods: Pts with a histologic diagnosis of unresectable and/or metastatic CRC, with documented MSS or pMMR status, and previously treated with up to 3 standard-of-care systemic regimens will be enrolled in the RP2 + Atezo + Bev or RP3 + Atezo + Bev treatment groups (30 pts per group). Further key inclusion criteria include Eastern Cooperative Oncology Group performance status 0 to 1 and adequate hepatic, renal, and hematologic function. RP2/RP3 will be injected into tumors by direct or image-guided injection. Pts will receive 8 total doses of up to 10 mL of RP2 or RP3, with a first dose concentration of 1 × 106 plaque-forming units (PFU)/mL, followed by 3 doses of 1 × 107 PFU/mL every 2 weeks, and then 4 doses of 1 × 107 PFU/mL every 3 weeks. Pts may receive a second course of up to 8 injections of RP2/RP3 if study criteria are met. Bev will be administered starting on week 1; Atezo will be administered starting week 7. The primary endpoint is objective response rate; secondary endpoints are safety, overall survival, progression-free survival, duration of response, and complete response rate. Antitumor activity will be evaluated using Response Evaluation Criteria in Solid Tumors version 1.1 as modified for this study. Safety will be assessed by physical examination, clinical laboratory evaluations, vital signs, and monitoring for adverse events (AEs; including serious AEs). Clinical trial information: NCT05733611 .

55 Background: Nearly one-half of deficient mismatch repair (d-MMR) metastatic colorectal cancers (mCRC) demonstrate durable responses to immune checkpoint inhibitors (ICIs). Given preclinical data indicating that liver metastases sequester activated CD8+ T cells from systemic circulation, we examined clinical outcome by metastatic site. Methods: In a retrospective cohort of patients with d-MMR mCRCs treated at multiple centers in France (n=66), we sought to validate data from a U.S. cohort, and then performed pooled analysis (n=104). All patients received first-line ICI monotherapy. Metastatic site was analyzed in relationship to tumor response (RECIST version 1.1), and progression-free survival (PFS) by multivariable stratified Cox regression after adjustment for covariates. Results: Objective responses were achieved in 38/66 (58%) patients in the validation cohort. Best tumor response included 13 (20%) complete responses (CR), 25 (38%) partial responses (PR), 16 (25%) stable disease, and 11 (17%) progressive disease (PD). One-year and 5-year PFS rates were 73% and 67%, respectively; 18 (27%) patients progressed during immunotherapy. Best tumor response was attenuated in patients with liver metastasis ( P=0.03). Presence of liver metastasis, but not other sites, was associated with significantly poorer PFS after adjustment for covariates (HRadj 2.82; 95%CI, 1.08-7.39; Padj=0.03). In a pooled analysis, liver metastasis remained significantly and independently associated with poorer PFS (HRadj 3.18; 95%CI, 1.52-6.67; Padj=0.002) and with attenuated tumor best response (P=0.01). Conclusions: Metastasis to the liver, but not other sites, was validated as an independent factor associated with poorer response and survival after ICI treatment in d-MMR mCRCs. These data underscore the need for novel therapeutic strategies in these patients. [Table: see text]