Block, Matthew S.

PURPOSE To compare mortality risk among long-term survivors of high-grade serous ovarian cancer (HGSOC) with that of the general US population and to examine how mortality and recurrence trends have evolved under changing treatment approaches. MATERIALS AND METHODS This is a retrospective cohort study including patients with histologically confirmed HGSOC treated at a single referral cancer center from 1991 to 2022. Mortality risk, expressed as standardized mortality ratios (SMRs, ratio of observed deaths in the study population to expected deaths in an age-matched US population), was assessed at diagnosis and yearly on patients without events (disease persistence, recurrence, or death from any cause). RESULTS A total of 2,074 consecutive patients were included. The median follow-up was 12.5 years (IQR, 11.7-13.8). Most patients were stage III (1,396, 69.2%), 1,299 (62.8%) underwent primary cytoreductive surgery, and 1,688 (87.4%) received platinum-taxane as first-line therapy. At diagnosis, the mortality rate was 7.40 times higher than that in the general population (95% CI, 7.04 to 7.77). By 7 event-free years, the 95% CI for the SMR included 1 for the first time, and at 10 years, the SMR was 1.05 (95% CI, 0.72 to 1.49), indicating no statistically significant excess mortality compared with the general population. In those event-free at 10 years, the 5-year cumulative incidence of ovarian cancer–related deaths (8.2% [95% CI, 4.2 to 16.0]) was comparable with that of non–ovarian cancer–related deaths (6.3% [95% CI, 2.9 to 13.8]). CONCLUSION In this cohort, mortality risk steadily declined for patients who remained event-free, approaching that of the general population by 7 years after diagnosis. These results emphasize the importance of individualized, long-term follow-up to address both recurrence risk and survivorship needs.

Background: Circulating tumor DNA (ctDNA) is predictive of recurrence in resected stage III melanoma, yet its role in the neoadjuvant setting for clinical stage III (cSIII) is unclear. Objective: Assess the association between ctDNA and outcomes following neoadjuvant immunotherapy (IO) + targeted therapy (TT) in cSIII melanoma. Design: Patients in the NeoACTIVATE study were treated with neoadjuvant IO + TT, underwent lymphadenectomy, and received adjuvant immunotherapy. Methods: Patients with ctDNA testing performed at baseline, pre- and post-operation were analyzed. Baseline positron emission tomography–computed tomography volumetrics and surgical, major pathological responses (MPR) were assessed. Results: Thirteen patients had serial ctDNA, 10 (77%) were detectable at baseline, and 9/10 (90%) had ctDNA clearance. Seven (54%) achieved MPR, all with undetectable preoperative ctDNA, yet 3/7 (43%) had disease recurrence. Conclusion: ctDNA and MPR are poor predictors of recurrence following neoadjuvant IO + TT for cSIII melanoma patients. Further studies are warranted to define the role of ctDNA in this setting.

Abstract Purpose: CD4 T-cell immunity is associated with improved survival in patients with breast cancer. We previously reported a phase I trial evaluating a folate receptor alpha (FRα) vaccine administered with cyclophosphamide (CP), demonstrating excellent safety and immunogenicity. To simplify the vaccine strategy for ease of use, we report here the results of a randomized phase II trial evaluating a lower vaccine dose alongside the original dose, administered with or without CP pretreatment. Patients and Methods: Patients with triple-negative breast cancer who completed all systemic and local therapies were assigned to receive either low-dose (825 μg) or high-dose (2.5 mg) vaccine peptides plus GM-CSF in six 4-week cycles, with or without CP prior to vaccination. Safety was monitored, and immunogenicity was evaluated before and after vaccination. Results: A total of 80 patients were dosed with vaccine, and 58 patients were evaluable for immunogenicity. Vaccination was well tolerated and elicited immunity in 83% of patients. Levels of FRα-specific T cells were high, persistent, and comparable with T-cell levels against tetanus toxoid. No differences in immunity were observed between the two doses. CP pretreatment also did not affect the immune responses. Recurrences occurred in eight evaluable patients and were unrelated to the treatment arm. No patients died during the study because of their disease. Conclusions: The reduced-dose FRα vaccine is as effective as the original dose and does not require CP to generate maximal immunity. These findings may inform the design of trials testing efficacy in triple-negative breast cancer or other cancers.

Objectives: This trial served as a proof-of-concept for whether inhibition of protein kinase C iota (PKCι) with auranofin and sirolimus provide antineoplastic effects in patients with recurrent high-grade serous ovarian cancer. Methods: This drug combination was administered to patients with recurrent high-grade serous ovarian cancer. Dosing was based on unpublished phase 1 data and consisted of auranofin 6 mg and sirolimus 5 mg both orally per day of a 28-day cycle. The primary endpoint was tumor response. Available tumor tissue was assessed for PKCι protein expression by immunohistochemistry (IHC) and PRKCI copy number by fluorescence in-situ hybridization (FISH) after the start of cancer therapy. Results: Twenty-two patients were enrolled, and 21 were evaluable for all clinical trial endpoints. One patient was unevaluable because she did not receive a full chemotherapy cycle. No tumor responses were seen in the first 21 patients, resulting in early trial termination per a priori trial design. The median progression-free survival was 2.1 months (95% CI: 1.8-3.7). The median overall survival was 4.4 months (95% CI: 2.6-12.5). Fourteen (67%) patients had at least one grade 3 or worse adverse event. Nineteen of 21 evaluable patients had available tumor tissue, which showed the median PKCι copy number averaged per cell of 3 (range: 2 to 7), and PKCι expression (at least 1+) in all. Conclusions: As prescribed here, auranofin and sirolimus manifested no antineoplastic activity in patients with recurrent high-grade serous ovarian cancer that expressed PKCι.

6061 Background: PDS0101 is a T cell stimulating immunotherapy (therapeutic vaccine) targeting HPV16. The combination of PDS0101 + pembrolizumab (5 cycles) has shown durable clinical responses in HPV-positive recurrent/metastatic HNSCC. MC200710 is a window of opportunity study in patients with HPV-associated oropharyngeal squamous cell carcinoma (HPV+ OPSCC). This prospective phase II trial utilized 2 cycles of neoadjuvant PDS0101 aloneor in combination with pembrolizumab prior to surgical resection or chemoradiotherapy (CRT). Herein, we report the initial results, including primary endpoint of ctDNA response. Methods: Between June 2022 and September 2024, 20 patients (10 per Arm) with locally advanced HPV+ OPSCC were enrolled in a sequential alternating design. Arm A received 2 cycles of PDS0101 and Arm B received 2 cycles of PDS0101 and pembrolizumab with all patients undergoing subsequent surgery or CRT. Assessments were done at baseline, post cycle 1, and post cycle 2 (prior to surgery or CRT). The coprimary endpoint of ctDNA response was defined as a ≥50% decline in ctDNA post cycle 2 compared to baseline as quantified using NavDx (TTMV fragments/mL). Radiologic objective response rate (ORR) was assessed as per RECIST 1.1. Toxicity through the neoadjuvant period was assessed using CTCAE criteria and recurrence rates following surgery or CRT are reported. Results: Patients were similar between arms: male 90%, median age 61 years, cT1/T2 70%, cN1 65%, and no smoking history 65%. All patients completed both cycles of therapy with 13 (65%) undergoing primary operative management and 7 CRT (35%). The most common toxicity was injection site reaction 85% grade 1, 15% grade 2, 0% grade 3, consistent with prior studies. One patient experienced grade 2 pneumonitis during the neoadjuvant window (Arm B). There was one grade 3 toxicity (5%) possibly attributable to study intervention with one patient experiencing transient hepatitis requiring hospitalization (Arm A). Zero of 10 patients in Arm A had a ≥50% decline in ctDNA from baseline while 5 of 10 patients (50%) met this primary endpoint in ARM B (p=0.03). After Cycle 2, based on RECIST 1.1, no Arm A patients had a partial response (PR), with 7 having stable disease (SD); Arm B had 2 patients with PR and 8 with SD. With median follow up of 6 months, 2 patients in Arm A recurred and 0 patients in Arm B. Conclusions: The combination of PDS0101 and pembrolizumab met the trial’s primary endpoint of ctDNA response and shows promise for further evaluation. ctDNA can be used to assess early response and future studies could use ctDNA to adapt neoadjuvant therapy. Based on these findings, a neoadjuvant dose optimization study in HPV16+ oropharyngeal carcinoma is warranted and evaluation of PDS0101 and pembrolizumab in comparison to pembrolizumab alone. Clinical trial information: NCT05232851 .

e15046 Background: BRAF V600 is the most common driver mutation in melanoma, seen in ≈50% of patients. Recently, the use of liquid biopsy assays that are based on circulating tumor DNA (ctDNA) has become widespread for diagnosis and residual disease monitoring. We have previously reported on our droplet digital PCR (ddPCR) test as a liquid biopsy for BRAF mutant (BRAFm) melanoma. Here we report the correlation between clinical and radiological parameters and ddPCR test results. Methods: Using the department of laboratory medicine archives, we have identified all biopsy proven BRAFm melanoma patients that were tested with the BRAF V600 ddPCR assay at our institution over the years 2018-2024. All patients had blood samples collected, and cell free DNA (cfDNA) was extracted from plasma using the Qiagen QIAamp Circulating Nucleic Acid Kit. cfDNA was evaluated with a BioRad QX200 droplet digital PCR platform assessing for BRAF V600E/K mutations. Clinical and demographic data were collected from medical records. Radiometabolic features including volumetric data and FDG PET SUV values were collected and analyzed using the MIM software (MIM Software Inc., Beachwood, OH, USA). Univariate and multivariate analyses were used to assess correlations between baseline variables and test results. Results: 71 patients were identified. The median age was 59 (26-85), 54% were males. 46 patients (65%) had a positive test result which was based on a cut-off of ≥4 mutant copies per ml. 65 patients (92%) had active disease on imaging studies, of which those with a positive test result were younger (p = 0.047), had a higher proportion of osseous metastases (p = 0.02) and had a higher number of lesions (p = 0.006). There was no difference in the median overall survival between the groups (11 months vs. 33 months for positive and negative result respectively, log-rank test; p = 0.15). Total tumor volume on PET-CT (in ml) was predictive of the quantitative ddPCR test result (in copies per ml), with every increase in 10 ml of tumor leading to an expected increase of 370 copies per ml (p < 0.001). Multivariate models have failed to show a correlation between baseline parameters and the quantitative ddPCR test result. When performing the analyses using logistic regression models with the binary ddPCR test result as the outcome, osseous metastases were predictive in a univariate model (OR = 4.3, 95% CI 1.4-15.4). The best fit multivariate model showed that higher burden of disease with ≥6 lesions (OR = 6.57, 95% CI 1.24-44.3) and elevated LDH (OR = 8.8, 95% CI 1.83-56.91) were associated with an increased risk for a positive result, while younger age was associated with decreased risk for a positive result (OR = 0.92, 95% CI 0.86-0.97). Conclusions: The results of ddPCR testing for BRAF mutation are correlated with the radiological and volumetric extent of the disease. This test could be useful in patients presenting with high-burden disease when a fast turnaround time is needed.

5555 Background: Platinum-resistant/refractory ovarian cancer presents a significant therapeutic challenge and despite several attempts, immunotherapies have not delivered satisfactory results to be approved. Identifying biomarkers of response to novel therapies is crucial for personalizing treatments and improving patient outcomes, especially since certain patients do experience long term benefit after the treatment with pembrolizumab and igrelimogene litadenorepvec (TILT-123; an oncolytic adenovirus coding for TNF and IL-2). Methods: Tumor biopsies (n=62), ascites (n=8) and blood (n=234) were collected from 15 patients treated in the PROTA trial (Phase I, NCT05271318). These patients received pembrolizumab intravenously plus igrelimogene litadenorepvec intravenously, followed by local administration intratumorally or intraperitoneally. Sampling took place prior to therapy, during therapy and after it. Tumor proteome (IHC, mIF) and transcriptome was analyzed to assess immune changes and virus presence. Ascites and blood samples were assayed to measure cell counts, phenotypes, cytokine and protein counts, as well as for the presence of antiviral neutralizing antibodies (NAbs). Biological parameters were correlated with overall survival (OS), RECIST 1.1 evaluations and tumor size changes. For analysis of OS, logrank test was used. For group comparisons two-tailed Mann-Whitney U-test was used. Pearson or Spearman tests were used for correlations. Results: Patients experiencing a drop in circulating lymphocytes 8-24 hours after treatment were more likely to experience longer OS (p=0.044). Additionally, patients with a higher lymphocyte count at baseline experienced similar OS benefit (p=0.018) plus a positive correlation with disease control (p=0.023). Most patients (11/15) showed antiviral immunity at baseline but eventually all patients developed neutralizing activity, and the same was observed in ascites. The presence of NAbs at baseline as well as development of highest titers were positively correlated with longer OS (p=0.004) and disease control (p=0.003). Conclusions: Igrelimogene litadenorepvec and pembrolizumab are therapies designed to attract, activate and/or protect lymphocyte-mediated antitumor activity. These findings suggest that having a fit immune system able to mobilize effector immune cells as well as responding to immunostimulant agents increases therapeutic success. As a disease with few therapeutic options, ovarian cancer patients often receive multiple lines of chemotherapy that might decrease the efficacy of immediate immunotherapies. The potential use of these biomarkers will be studied in larger studies to validate their utility in guiding the use of immunotherapy in this challenging patient population. Clinical trial information: NCT05271318 .

3099 Background: Immune checkpoint inhibitors (ICI) are effective in melanoma, but many patients experience progression on or after approved ICI +/- MAPK inhibitor therapy. Melanocortin-1 receptor (MC1R) is a novel target for radiopharmaceutical therapy (RPT) and is highly expressed on melanoma tumor cells. VMT01 is an MC1R-targeted RPT that can be radiolabeled with either 203 Pb (patient selection and dosimetry assessments) or 212 Pb (alpha particle therapy). Here, we present data on the first in-human evaluation of [ 203 Pb/ 212 Pb]VMT01 in patients with metastatic melanoma. FDA granted Fast Track Designation to the product on the bases of preclinical experiments combining [ 212 Pb]VMT01 with immunotherapy. Methods: This is a first-in-human dose-finding study to determine the safety, pharmacokinetics, dosimetry and preliminary efficacy of [ 212 Pb]VMT01 in subjects with MC1R-positive metastatic melanoma who progressed on at least 1 approved first-line therapy (NCT05655312). Phase 1 of the trial includes escalating dose cohorts. The first two cohorts incorporate dosimetry evaluations (reported separately) with the imaging surrogate [ 203 Pb]VMT01 prior to receiving up to 3 treatment cycles of [ 212 Pb]VMT01 therapy (injected activity of 111 MBq (3 mCi) or 185 MBq (5 mCi) for Cohort 1 and 2, respectively). Participants are evaluated for any DLT for the first 6 weeks after cycle one. Efficacy is assessed by RECIST 1.1 criteria by the investigator. Following the start of the study the anticipated combination arm with nivolumab was opened as an amendment. Results: Cohort 1 (DCO 04Sep24) was completed with 3 enrolled participants who received 3 treatment cycles without any DLTs or SAEs. Cohort 1 participants showed prolonged stabilization of disease from start of treatment (mean: 11.1 months); one participant developed a confirmed objective response (PR) after completion of all three [ 212 Pb]VMT01 administrations and is still on trial after 13.1 months from start of treatment. Cohort 2 has completed with 7 enrolled participants. No DLTs or related SAEs have been observed. All participants in this Cohort progressed after either the first cycle (3 participants) or the second cycle (4 participants).Based on these preliminary results showing anti-tumor effect at the lower dose, additional cohorts for both monotherapy and in combination with nivolumab were introduced at a de-escalated dose of 55.5 MBq (1.5 mCi). Both cohorts are now open for enrollment. Updated safety and efficacy data will be analyzed and presented at ASCO. Conclusions: At 111 MBq and 185 MBq activity levels, [ 212 Pb]VMT01 was safe and well-tolerated. An objective response and prolonged stabilization of disease were observed at the 111 MBq activity level while no effect was seen at 185 MBq. The study will continue to explore potentially immunostimulating lower doses of administered activity of [ 212 Pb]VMT01 either as a monotherapy or in combination with nivolumab. Clinical trial information: NCT05655312 .

3040 Background: EVEREST-2 is a first-in-human, phase 1/2 trial to assess the safety and efficacy of A2B694, an autologous, logic-gated Tmod CAR T therapy targeted to MSLN, which is normally expressed in the mesothelium and can be upregulated in many solid tumors. A2B694 is designed to overcome challenges of on-target, off-tumor toxicity that have limited other MSLN-targeted approaches by combining a CAR-activating receptor targeting MSLN with a blocker CAR that recognizes HLA-A*02, to distinguish between normal and tumor cells (Tokatlian, et al. J Immunother Cancer. 2022). Methods: Adults with recurrent unresectable, locally advanced, or metastatic cancers with MSLN expression who have progressed after standard-of-care therapy are eligible for EVEREST-2. Enrollment to EVEREST-2 and collection of T-cells occurs through the ongoing prescreening study BASECAMP-1 (NCT04981119). When clinically appropriate, A2B694 is manufactured from cryopreserved T cells, and patients undergo lymphodepletion before A2B694 infusion. The dose-escalation phase is evaluating the safety and tolerability of A2B694 to identify the recommended phase 2 dose (RP2D). Dose escalation was started at 1x10 8 Tmod positive cells (dose level [DL] 1) and will increase up to 14x10 8 in combination with low-dose IL-2 (DL 5). The dose-expansion phase will confirm RP2D and collect biomarker data to further characterize A2B694. Results: As of January 15, 2025, 5 participants (median age: 60 years; range, 50-84) have enrolled on EVEREST-2 and received A2B694 at DLs 1-2; participants had ovarian cancer (n = 3), pancreatic cancer (n = 1), and non-small cell lung cancer (n = 1) and had received a median of 4 prior lines of therapy (range, 1-7). Lymphodepleting chemotherapy was well tolerated with no significant cytopenias observed. The most common adverse events were lymphopenia (7 [14.6%]) and decreased appetite (6 [12.5%]). There were no dose-limiting toxicities, cytokine release syndrome, nor related neurotoxicity. One participant was admitted to the hospital for decreased appetite. No long-term toxicities have been noted up to 7.5 months post-infusion. Of the participants who have received A2B694, 5 were efficacy evaluable at DLs 1-2. A2B694 was detected post-infusion in the peripheral blood in all patients. Additionally, A2B694 was detected in an abdominal tumor biopsy from a patient with pancreatic cancer 42 days post-infusion. Conclusions: The logic-gated approach was successful at reducing toxicity seen with prior MSLN-targeted CAR T therapies, and A2B694 showed successful CAR T expansion and tumor infiltration. The maximum tolerated dose has not been reached, and results from the dose-escalation phase continue to determine the RP2D. Clinical trial information: NCT06051695 .

9578 Background: Anti-PD1 immunotherapy has shown improved clinical outcomes in patients (pts) with advanced cSCC, and recently, in the neoadjuvant setting for resectable disease. Pathological (path) response is predictive of recurrence in melanoma and recent NeoIT trials suggests the same in cSCC; however, an analysis of clinical outcomes in pts with resectable cSCC treated with intended anti-PD1-based NeoIT in larger datasets remains unknown. Methods: Pts with resectable cSCC treated with intended anti-PD1-based NeoIT from 17 cancer centres globally were included. Baseline patient and disease characteristics, treatment regimen, path response and recurrence-free survival (RFS) or progression-free survival (PFS) were collected and examined. Results: 134 pts with resectable cSCC were treated with intended anti-PD1-based NeoIT. Median age was 75 years old (range, 39-97), 72% (n=97) were male. One fifth (22%, n=29) were immunocompromised and 43% (n=58) had ECOG PS of ≥1. Of 125 (93%) pts with known primary cSCC, 82% (n=102) were from the head & neck. Most pts (79%, n=106) were stage III/IV. The majority had anti-PD1 monotherapy (91%, n=122) and 9% (n=12) had anti-PD1+/-investigational agent. Median follow-up from commencement of NeoIT was 10 months (95% CI, 9 - 12). Nearly half of the pts (49%, n=66) underwent surgery; 37 (56%) pts had major pathological response (MPR; ≤10% viable tumour cells at the surgical specimen; 31 [47%] had complete path response [0% of viable tumour cells] and 6 [9%] had near complete path response [1-10% of viable tumour cells]), 6 (9%) had partial path response (pPR; >10% and ≤50% of viable tumour cells), and 23 (35%) had path non-response (pNR; >50% of viable tumour cells). Of the 66 pts who underwent surgery, 11% (n=7) had recurrence (5 loco-regional and 2 distant recurrence), all non-MPR pts (1 pPR and 6 pNR). 12-months RFS was improved with MPR vs non-MPR (100% vs 79%, p=0.004). 52% (n=34) pts had adjuvant treatment (23 anti-PD1 alone, 7 anti-PD1+/-investigational agent, 2 platinum and 2 cetuximab). Within non-MPR pts, 12 had adjuvant treatment (3 recurred; 25%), while 17 did not have adjuvant treatment (4 recurred; 24%). Fifty-one percent (n=68) of pts did not have surgery; 9 (13%) due to progressive disease (PD) and 53 (78%) due to clinical response. Of the 53 pts with a clinical response, 5 (9%) subsequently progressed. Fourteen (10%) pts have died, 6 (4%) related to cSCC; 2 had surgery (non-MPR) and 4 did not have surgery (all due to PD). Conclusions: Anti-PD1-based NeoIT is an active regimen in resectable stage II-IV cSCC and is associated with high clinical response and MPR rates. No pts with MPR from NeoIT has recurred to date, however, 9% of pts who did not have surgery due to clinical response eventually progressed. These findings highlight the importance of further research to investigate the role of surgery in this subgroup of patients.