Predictors and benefits of multiagent chemotherapy for pancreatic adenocarcinoma: Timing matters

INTRODUCTION

Adjuvant (A) multiagent chemotherapy (MC) is the standard of care for patients with pancreatic adenocarcinoma (PDAC). Tolerating MC following a morbid operation may be difficult, thus neoadjuvant (NA) treatment is preferable. This study examined how the timing of chemotherapy was related to the regimen given and ultimately the overall survival (OS).

METHODS

The National Cancer Database was queried from 2006 to 2017 for nonmetastatic PDAC patients who underwent surgical resection and received MC or single-agent chemotherapy (SC) pre- or postresection. Predictors of receiving MC were determined using multivariable logistic regression. Five-year OS was evaluated using the Kaplan-Meier and Cox proportional hazards model.

RESULTS

A total of 12,440 patients (NA SC, n = 663; NA MC, n = 2313; A SC, n = 6152; A MC, n = 3312) were included. MC utilization increased from 2006-2010 to 2011-2017 (33.1%-49.7%; odds ratio [OR]: 0.59; p < 0.001). Younger age, fewer comorbidities, higher clinical stage, and larger tumor size were all associated with receipt of MC (all p < 0.001), but NA treatment was the greatest predictor (OR 5.18; 95% confidence interval [CI]: 4.63-5.80; p < 0.001). MC was associated with increased median 5-year OS (26.0 vs. 23.9 months; hazard ratio [HR]: 0.92; 95% CI: 0.88-0.96) and NA MC was associated with the highest survival (28.2 months) compared to NA SC (23.3 months), A SC (24.0 months), and A MC (24.6 months; p < 0.001).

CONCLUSION

Use and timing of MC contribute to OS in PDAC with an improved 5-year OS compared to SC. The greatest predictor of receiving MC was being given as NA therapy and the greatest survival benefit was the NA MC subgroup. Randomized studies evaluating the timing of effective MC in PDAC are needed.

Prolonged Survival Following Intra-abdominal Mycobacterium abscessus Infection Without Antimicrobial Therapy or Surgical Intervention

Management of Mycobacterium abscessus infection involves prolonged multidrug antibiotic therapy with surgical resection indicated in extensive disease and abscesses. We report a case of post-surgical intra-abdominal M. abscessus infection with prolonged survival and radiographic resolution without intervention. A 51-year-old female who had a prolonged hospital stay with multiple surgeries following a complicated laparoscopic sleeve gastrectomy developed multiple M. abscessus intra-abdominal and abdominal wall abscesses with cutaneous fistulae. She was started on a multidrug antibiotic regimen. However, the patient terminated the regimen after 4 weeks due to intolerable side effects and was transitioned to hospice care. She showed steady clinical improvement with radiographic resolution of the abscesses over the next year. In the context of the limited understanding of these infections, our finding is notable, given that in this period, she avoided potential hospitalizations, life altering side effects of prolonged antimicrobial therapy, and complications from more surgeries.

Phase II Trial of Nelipepimut-S Peptide Vaccine in Women with Ductal Carcinoma In Situ

NeuVax is a vaccine comprised of the HER2-derived MHC class I peptide E75 (nelipepimut-S, NPS) combined with GM-CSF. We completed a randomized trial of preoperative vaccination with NeuVax versus GM-CSF alone in patients with ductal carcinoma in situ (DCIS). The primary objective was to evaluate for NPS-specific cytotoxic T lymphocyte (CTL) responses. Patients with human leukocyte antigen (HLA)-A2-positive DCIS were enrolled and randomized 2:1 to NeuVax versus GM-CSF alone and received two inoculations prior to surgery. The number of NPS-specific CTL was measured pre-vaccination, at surgery, and 1 and 3 to 6 months post-operation by dextramer assay. Differences in CTL responses between groups and between pre-vaccination and 1-month post-operation were analyzed using a two-sample t test or Wilcoxon rank sum test. The incidence and severity of adverse events were compared between groups. Overall, 45 patients were registered; 20 patients were HLA-A2 negative, 7 declined participation, 1 withdrew, and 4 failed screening for other reasons. The remaining 13 were randomized to NeuVax (n = 9) or GM-CSF alone (n = 4). Vaccination was well-tolerated with similar treatment-related toxicity between groups with the majority (>89%) of adverse events being grade 1. The percentage of NPS-specific CTLs increased in both arms between baseline (pre-vaccination) and 1-month post-operation. The increase was numerically greater in the NPS+GM-CSF arm, but the difference was not statistically significant. NPS+GM-CSF is safe and well-tolerated when given preoperatively to patients with DCIS. In patients with HLA-A2-positive DCIS, two inoculations with NPS+GM-CSF can induce in vivo immunity and a continued antigen-specific T-cell response 1-month postsurgery.

PREVENTION RELEVANCE

This trial showed that vaccination of patients with HLA-A2-positive DCIS with NeuVax in the preoperative setting can induce a sustained antigen-specific T-cell response. This provides proof of principle that vaccination in the preoperative or adjuvant setting may stimulate an adaptive immune response that could potentially prevent disease recurrence.

Tumor infiltrating lymphocytes as an endpoint in cancer vaccine trials

Checkpoint inhibitors have invigorated cancer immunotherapy research, including cancer vaccination. Classic early phase trial design and endpoints used in developing chemotherapy are not suited for evaluating all forms of cancer treatment. Peripheral T cell response dynamics have demonstrated inconsistency in assessing the efficacy of cancer vaccination. Tumor infiltrating lymphocytes (TILs), reflect the local tumor microenvironment and may prove a superior endpoint in cancer vaccination trials. Cancer vaccines may also promote success in combination immunotherapy treatment of weakly immunogenic tumors. This review explores the impact of TILs as an endpoint for cancer vaccination in multiple malignancies, summarizes the current literature regarding TILs analysis, and discusses the challenges of providing validity and a standardized implementation of this approach.

Divergent clinical outcomes in a phase 2B trial of the TLPLDC vaccine in preventing melanoma recurrence and the impact of dendritic cell collection methodology: a randomized clinical trial

BACKGROUND

A randomized, double-blind, placebo-controlled phase 2b trial of the tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine was conducted in patients with resected stage III/IV melanoma. Dendritic cells (DCs) were harvested with and without granulocyte-colony stimulating factor (G-CSF). This analysis investigates differences in clinical outcomes and RNA gene expression between DC harvest methods.

METHODS

The TLPLDC vaccine is created by loading autologous tumor lysate into yeast cell wall particles (YCWPs) and exposing them to phagocytosis by DCs. For DC harvest, patients had a direct blood draw or were pretreated with G-CSF before blood draw. Patients were randomized 2:1 to receive TLPLDC or placebo. Differences in disease-free survival (DFS) and overall survival (OS) were evaluated. RNA-seq analysis was performed on the total RNA of TLPLDC + G and TLPLDC vaccines to compare gene expression between groups.

RESULTS

144 patients were randomized: 103 TLPLDC (47 TLPLDC/56 TLPLDC + G) and 41 placebo (19 placebo/22 placebo + G). Median follow-up was 27.0 months. Both 36-month DFS (55.8% vs. 24.4% vs. 30.0%, p = 0.010) and OS (94.2% vs. 69.8% vs. 70.9%, p = 0.024) were improved in TLPLDC compared to TLPLDC + G or placebo, respectively. When compared to TLPLDC + G vaccine, RNA-seq from TLPLDC vaccine showed upregulation of genes associated with DC maturation and downregulation of genes associated with DC suppression or immaturity.

CONCLUSIONS

Patients receiving TLPLDC vaccine without G-CSF had improved OS and DFS. Outcomes remained similar between patients receiving TLPLDC + G and placebo. Direct DC harvest without G-CSF had higher expression of genes linked to DC maturation, likely improving clinical efficacy.

Meeting the New Commission on Cancer Operative Standards: Where Do We Stand Now?

INTRODUCTION

The 2020 Commission on Cancer accreditation standards 5.7 and 5.8 address total mesorectal excision for rectal cancer and lymph node sampling for lung cancer. The purpose of this review was to assess our institution's compliance with these operative standards, which will be required in 2022 and 2023, and provide recommendations to other military training facilities seeking to comply with these standards.

MATERIALS AND METHODS

A 2018-2020 single institution chart review was performed of operative and pathology reports. Identified deficits were addressed in meetings with colorectal and thoracic surgery leadership, and cases were followed to reassess compliance.

RESULTS

A total of 12 rectal and 48 lung cancer cases met the inclusion criteria and were examined. Pre-intervention compliance for standards 5.7 and 5.8 was 58% and 35%, respectively, because of inadequate synoptic reporting and lymph node sampling. After intervention, compliance was 100%.

CONCLUSIONS

Our institution requires changes to comply with new standards, including in areas of documentation and systematic pulmonary lymph node sampling. We provide lessons learned from our own institutional experience, including practical tips and recommendations to achieve compliance. All military training facilities performing lung and rectal oncologic resections should conduct an internal review of applicable cases in preparation for upcoming American College of Surgeons Commission on Cancer site visits.

Downstaging of Pancreatic Adenocarcinoma With Either Neoadjuvant Chemotherapy or Chemoradiotherapy Improves Survival

BACKGROUND

Neoadjuvant chemotherapy (NAC) or chemoradiation (NAC+XRT) is incorporated into the treatment of localized pancreatic adenocarcinoma (PDAC), often with the goal of downstaging before resection. However, the effect of downstaging on overall survival, particularly the differential effects of NAC and NAC+XRT, remains undefined. This study examined the impact of downstaging from NAC and NAC+XRT on overall survival.

METHODS

The National Cancer Data Base (NCDB) was queried from 2006 to 2015 for patients with non-metastatic PDAC who received NAC or NAC+XRT. Rates of overall and nodal downstaging, and pathologic complete response (pCR) were assessed. Predictors of downstaging were evaluated using multivariable logistic regression. Overall survival (OS) was assessed with Kaplan-Meier and Cox proportional hazards modeling.

RESULTS

The study enrolled 2475 patients (975 NAC and 1500 NAC+XRT patients). Compared with NAC, NAC+XRT was associated with higher rates of overall downstaging (38.3 % vs 23.6 %; p ≤ 0.001), nodal downstaging (16.0 % vs 7.8 %; p ≤ 0.001), and pCR (1.7 % vs 0.7 %; p = 0.041). Receipt of NAC+XRT was independently predictive of overall (odds ratio [OR] 2.28; p < 0.001) and nodal (OR 3.09; p < 0.001) downstaging. Downstaging by either method was associated with improved 5-year OS (30.5 vs 25.2 months; p ≤ 0.001). Downstaging with NAC was associated with an 8-month increase in median OS (33.7 vs 25.6 months; p = 0.005), and downstaging by NAC+XRT was associated with a 5-month increase in median OS (30.0 vs 25.0 months; p = 0.008). Cox regression showed an association of overall downstaging with an 18 % reduction in the risk of death (hazard ratio [HR] 0.82; 95 % confidence interval, 0.71-0.95; p = 0.01) CONCLUSION: Downstaging after neoadjuvant therapies improves survival. The addition of radiation therapy may increase the rate of downstaging without affecting overall oncologic outcomes.

Immunologic and dose dependent effects of rapamycin and its evolving role in chemoprevention

Rapamycin inhibits the mechanistic (formally mammalian) target of rapamycin (mTOR), an evolutionarily conserved intracellular kinase that influences activation of growth signaling pathways and immune responses to malignancy. Rapamycin has been found to have both immunosuppressant and immunostimulatory effects throughout the innate and adaptive responses based on the inhibition of mTOR signaling. While the immunosuppressant properties of rapamycin and mTOR inhibition explain rapamycin's success in the prevention of transplant rejection, the immunostimulatory characteristics are likely partially responsible for rapamycin's anti-neoplastic effects. The immunologic response to rapamycin is at least partially dependent on the dose and administration schedule, with lower doses inducing immunostimulation and intermittent dosing promoting immune function while limiting metabolic and immunosuppressant toxicities. In addition to its FDA-approved application in advanced malignancies, rapamycin may be effective as a chemopreventive agent, suspending progression of low-grade cancers, preventing invasive conversion of in situ malignancy, or delaying malignant transformation of established pre-malignant conditions.

Maximizing Benefit of Virtual Learning: Lessons from the COVID-19 Pandemic

Introduction

The coronavirus disease 2019 pandemic has profoundly impacted surgical education. We assessed resident perceptions of our virtual academic program, which consists of daily lectures or case conferences held via a videoconferencing platform.

Methods

A survey evaluating attitudes and practices for virtual academics was administered to general surgery residents. A focus group was conducted to identify benefits, barriers to engagement, and opportunities for improvement for virtual education. A total of 19 residents completed the education survey, and seven residents participated in the focus group.

Results

While expressing preference toward in-person academics (84.2%), residents felt the virtual academics were of good quality (median rating 4/5) and preferred virtual academics to no academic sessions (94.7%). Of respondents, 57.9% believe that the coronavirus pandemic negatively impacted their surgical education. They believe their American Board of Surgery In-Training Examination preparation was not impacted. Residents preferred using a computer over a phone for academics (79% versus 16%). The focus group identified the benefits of virtual academics, including the ability to participate while away and having recordings available. Areas for improvement included reinforcement of protected time for academics, requiring cameras be on, increasing in-lecture polls, and creation of an online repository of recordings for review. Residents hoped a virtual component of academics and recordings would continue past the pandemic.

Conclusions

Although virtual academics are not the preferred mode of learning in our residency, there are multiple unintended benefits. We recommend a hybrid academic model with in-person didactics and recorded video for later review.

Using the Flipped Classroom Model in Surgical Education: Efficacy and Trainee Perception

OBJECTIVE

To describe the feasibility, efficacy, and learner perception of the flipped classroom model for teaching conferences within surgical training programs.

DESIGN

For the flipped classroom conferences, video lectures were prepared by a faculty member, and sent to all attendees at least 2 days prior to lecture. The conference time was then spent going over cases and questions, rather than traditional lecture. We conducted a qualitative survey to assess learner's perceptions and pre-lecture quizzes to assess trainee preparedness.

SETTING

The comparison of pre-conference quizzes between flipped classroom and traditional models was carried out at Brooke Army Medical Center (BAMC) in San Antonio, TX, a tertiary care facility with a general surgery residency program. The survey was conducted at BAMC and within the Complex General Surgical Oncology fellowship program at University of Texas MD Anderson Cancer Center, where a flipped classroom model was similarly employed.

PARTICIPANTS

Surgical residents BAMC participated in pre-lecture quizzes. BAMC residents and MD Anderson fellows were invited to complete the online survey.

RESULTS

Lecture videos did not increase mean preparation time (1.53 vs. 1.46 hours without vs. with video, p = 0.858), but did increase mean quiz scores from 67% to 80% (p = 0.031) with 32/35 learners utilizing videos. Videos increased the proportion of learners who self-reported preparing at all from 42% to 95% (p = 0.28), and preparing for at least one hour for conference from 23% to 49% (p = 0.014). Of survey respondents, 90% said videos were very helpful, 90% would use them weekly if available, and 90% prefer this format to traditional lecture.

CONCLUSIONS

Utilization of a flipped classroom method was well received and preferred by surgical trainees, and it increased performance on pre-conference quizzes without increasing preparation time. Although creation of video lectures is work-intensive for lecturers, these results suggest it is more effective for learner preparation. These results could be generalizable to surgical residents nationwide as technology utilization increases in surgical education.

Safety and efficacy of autologous tumor lysate particle-loaded dendritic cell vaccination in combination with systemic therapies in patients with recurrent and metastatic melanoma

Immunotherapy has revolutionized the treatment of melanoma, yet survival remains poor for patients with metastatic disease. The autologous tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine has been shown to be safe adjuvant therapy for patients with resected stage III/IV melanoma who complete the primary vaccine series. Here, we describe an open-label trial of patients with metastatic melanoma treated with TLPLDC vaccine in addition to standard of care (SoC) therapies. The TLPLDC vaccine is created by loading autologous tumor lysate into yeast cell wall particles, which are phagocytosed by autologous dendritic cells ex vivo. Patients who recurred while enrolled in a phase IIb trial of adjuvant TLPLDC vaccine (crossover cohort) and patients with measurable metastatic melanoma cohort were offered TLPLDC vaccine along with SoC therapies. Tumor response was measured by RECIST 1.1 criteria. Overall survival (OS) and progression-free survival (PFS) were estimated by intention-to-treat analysis. Fifty-four patients were enrolled (28 in crossover cohort; 26 in metastatic melanoma cohort). The vaccine was well-tolerated with no grade ≥3 adverse events when given with SoC therapies to include checkpoint inhibitors, BRAF/MEK inhibitors, tyrosine kinase inhibitors, intralesional therapy and/or radiation. In the crossover arm, OS was 76.5% and PFS was 57.1% (median follow-up of 13.9 months). In the metastatic melanoma arm, OS was 85.7% and PFS was 52.2% (median follow-up 8.5 months). The TLPLDC vaccine is well-tolerated and safe in combination with SoC therapies. Future trials will determine the efficacy of TLPLDC in combination with SoC therapies in metastatic melanoma.

Near Complete Pathologic Response to PD-1 Inhibitor and Radiotherapy in a Patient with Locally Advanced Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains deadly despite advances in systemic therapies and surgical techniques. While there is increasing utilization of immune therapies across diverse cancer types, PDAC remains generally resistant to these treatments. We report a case of locally advanced PDAC treated with preoperative radiation and anti-PD-1 immunotherapy guided by preoperative PD-L1 tumor analysis. After 4 months of preoperative therapy, the patient was submitted to resection, demonstrating a near-complete pathologic response on final tumor analysis. We will discuss the relevant literature and current state of immunotherapeutics for PDAC.

Multi-institutional, prospective, randomized, double-blind, placebo-controlled phase IIb trial of the tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine to prevent recurrence in high-risk melanoma patients: A subgroup analysis

Background

Checkpoint inhibitors (CPI) in combination with cell‐based vaccines may produce synergistic antitumor immunity. The primary analysis of the randomized and blinded phase IIb trial in resected stage III/IV melanoma demonstrated TLPLDC is safe and improved 24‐month disease‐free survival (DFS) in the per treatment (PT) analysis. Here, we examine efficacy within pre‐specified and exploratory subgroups.

Methods

Stage III/IV patients rendered disease‐free by surgery were randomized 2:1 to TLPLDC vaccine versus placebo. The pre‐specified PT analysis included only patients completing the primary vaccine/placebo series at 6 months. Kaplan–Meier analysis was used to compare 24‐month DFS among subgroups.

Results

There were no clinicopathologic differences between subgroups except stage IV patients were more likely to receive CPI. In stage IV patients, 24‐month DFS was 43% for vaccine versus 0% for placebo (p = 0.098) in the ITT analysis and 73% versus 0% (p = 0.002) in the PT analysis. There was no significant difference in 24‐month DFS when stratified by use of immunotherapy or CPI. For patients with resected recurrent disease, 24‐month DFS was 88.9% versus 33.3% (p = 0.013) in the PT analysis. All benefit from vaccination was in the PT analysis; no benefit was found in patients receiving up to three doses.

Conclusion

The TLPLDC vaccine improved DFS in patients completing the primary vaccine series, particularly in the resected stage IV patients. The efficacy of the TLPLDC vaccine will be confirmed in a phase III study evaluating adjuvant TLPLDC + CPI versus Placebo + CPI in resected stage IV melanoma patients.

Immunotherapy as a partner for HER2-directed therapies

Introduction: Existing HER2-targeted therapies modulate the tumor microenvironment and the immunologic response cancer in a favorable way. While these therapies have made dramatic improvements in the treatment and prognosis of HER2-overexpressing malignancies, additional treatment options are still needed.Areas covered: This review covers the immunomodulatory effects of approved HER2-targeted therapies. We discuss the preclinical data that demonstrate an additive effect of the combination of trastuzumab or other HER2-targeting agents with immunomodulatory drugs. Finally, we report the initial studies on the combination of HER2-targeted agents together with immune checkpoint inhibitors or cancer vaccines in breast cancer.Expert opinion: Preclinical data suggest a synergistic effect of HER2-targeted therapy together with both checkpoint inhibitor and cancer vaccine immunotherapy. Results from initial trials with PD-1/PD-L1-blocking therapy together with HER2-targeted therapy have been negative, but responses were seen in patients with PD-L1+ breast cancer. Trastuzumab together with HER2-targeted cancer vaccination has shown benefits in triple negative breast cancer. Further trials are necessary and warranted to confirm the benefit of these combinations.

A Phase IIb Randomized Controlled Trial of the TLPLDC Vaccine as Adjuvant Therapy After Surgical Resection of Stage III/IV Melanoma: A Primary Analysis

Background

Melanoma therapy has changed dramatically over the last decade with improvements in immunotherapy, yet many patients do not respond to current therapies. This novel vaccine strategy may prime a patient’s immune system against their tumor and work synergistically with immunotherapy against advanced-stage melanoma.

Methods

This was a prospective, randomized, double-blind, placebo-controlled, phase IIb trial of the tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine administered to prevent recurrence in patients with resected stage III/IV melanoma. Patients were enrolled and randomized 2:1 to the TLPLDC vaccine or placebo (empty yeast cell wall particles and autologous dendritic cells). Both intention-to-treat (ITT) and per treatment (PT) analyses were predefined, with PT analysis including patients who remained disease-free through the primary vaccine/placebo series (6 months).

Results

A total of 144 patients were randomized (103 vaccine, 41 control). Therapy was well-tolerated with similar toxicity between treatment arms; one patient in each group experienced related serious adverse events. While disease-free survival (DFS) was not different between groups in ITT analysis, in PT analysis the vaccine group showed improved 24-month DFS (62.9% vs. 34.8%, p = 0.041).

Conclusions

This phase IIb trial of TLPLDC vaccine administered to patients with resected stage III/IV melanoma shows TLPLDC is well-tolerated and improves DFS in patients who complete the primary vaccine series. This suggests patients who do not recur early benefit from TLPLDC in preventing future recurrence from melanoma. A phase III trial of TLPLDC + checkpoint inhibitor versus checkpoint inhibitor alone in patients with advanced, surgically resected melanoma is under development.

Trial Registration

NCT02301611.

Supplementary information

The online version contains supplementary material available at (10.1245/s10434-021-09709-1).

Abstract PD11-09: Vadis trial: Phase II trial of nelipepimut-s peptide vaccine in women with DCIS of the breast

Background: Peptide cancer vaccines may be most effective when used in earlier stage cancers or pre-cancers where systemic and tumor microenvironmental immune suppression are less profound. Nelipepimut-S (NPS) plus granulocyte-macrophage colony-stimulating factor (GM-CSF) is a vaccine comprised of a human leukocyte antigen (HLA) restricted peptide from the extracellular domain of the HER2 protein (E75) combined with GM-CSF. We have completed a randomized phase II trial of preoperative vaccination with NPS+GM-CSF vs. GM-CSF alone with the primary outcome being NPS-specific cytotoxic T lymphocyte (CTL) responses.

Methods: HLA-A2 positive, DCIS patients were enrolled and randomized to either NPS+GM-CSF vs GM-CSF alone. The patients received two vaccinations prior to surgery at 2-week intervals. The number of NPS-specific CTL was measured at specified intervals (pre-vaccination, time of surgery, 1 month (+/- 7 days) post-op, and 3 months (+/- 7 days) post-op) using a flow cytometry-based dextramer assay. Differences in NPS-specific CTL responses between the two groups and between baseline pre-vaccination and 1-month post-op were analyzed using either a two-sample t-test or Wilcoxon rank sum test, when appropriate. The incidence and severity of adverse events, graded according to Common Terminology Criteria for Adverse Events (CTCAE) version (v) 4.03, were recorded and compared between treatment groups.

Results: 45 patients were registered; 7 withdrew consent, 1 opted for surgery at an external facility, 20 were ineligible due to negative HLA-A2, and 4 failed screening for other reasons, leaving 13 patients enrolled. The 13 patients were randomized (2:1) into treatment groups, with nine patients receiving NPS+GM-CSF and four patients receiving GM-CSF alone. The two groups were well-matched for age; however, the GM-CSF alone group had higher percentages of African American (50% vs. 22%) and Hispanic (25% vs. 11%) patients as compared to the NPS+GM-CSF group. In general, vaccination was well-tolerated with similar treatment-related toxicity profiles in the NPS+GM-CSF vs GM-GSF groups (Grade 1 - 93.3% vs. 89.3%, Grade 2 - 6.7% vs. 10.7%, respectively). The mean NPS-specific CTL% in the NPS+GM-CSF group at 1-month post-op was double that of the GM-CSF alone group (0.10 +/- 0.12% vs. 0.05 +/- 0.08, p=0.70). In addition, between baseline pre-vaccination and 1-month post-op, the NPS+GM-CSF group experienced an 11-fold increase in percentage of NPS-specific CTL (0.01 +/- 0.02% vs. 0.11 +/- 0.12%) as compared to only a 2.25-fold increase of NPS-specific CTL in the GM-CSF alone group (0.04 +/- 0.07% vs. 0.09 +/- 0.15%).

Conclusions: NPS+GM-CSF is safe and well-tolerated when given preoperatively to patients with DCIS. In HLA-A2 positive patients with DCIS, a single inoculation with NPS+GM-CSF can induce in vivo immunity and a continued antigen-specific T-cell response one month post-surgery. This data provides support for further testing of NPS+GM-CSF in the neoadjuvant and adjuvant settings in an attempt to prevent invasive recurrence in DCIS.

Citation Format: Anne E O'Shea, Guy T Clifton, Na Qiao, Brandy Heckman-Stoddard, Malgorzata Wojtowicz, Eileen Dimond, Isabelle Bedrosian, Diane Weber, Alex Husband, Ricardo Pastorello, Lana Vornik, George Peoples, Elizabeth A Mittendorf. Vadis trial: Phase II trial of nelipepimut-s peptide vaccine in women with DCIS of the breast [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD11-09.

Phase I Trial of Encapsulated Rapamycin in Patients with Prostate Cancer Under Active Surveillance to Prevent Progression

No approved medical therapies prevent progression of low-grade prostate cancer. Rapamycin inhibits cell proliferation and augments immune responses, producing an antitumor effect. Encapsulated rapamycin (eRapa) incorporates rapamycin into a pH-sensitive polymer, ensuring consistent dosing. Here, we present results from a phase I trial evaluating the safety and tolerability of eRapa in patients with prostate cancer. Patients with Gleason ≤7 (3+4) disease (low and intermediate risk) under active surveillance were enrolled in a 3+3 study with three eRapa dosing cohorts (cohort 1, 0.5 mg/week; cohort 2, 1 mg/week; and cohort 3, 0.5 mg/day). Patients were treated for 3 months and followed for an additional 3 months to assess safety, pharmacokinetics, quality of life (QoL), immune response, and disease progression. Fourteen patients (cohort 1, n = 3; cohort 2, n = 3; and cohort 3, n = 8) were enrolled. In cohort 3, one dose-limiting toxicity (DLT; neutropenia) and two non-DLT grade 1-2 adverse events (AE) occurred that resulted in patient withdrawal. All AEs in cohorts 1 and 2 were grade 1. Peak serum rapamycin concentration was 7.1 ng/mL after a 1 mg dose. Stable trough levels (∼2 ng/mL) developed after 48-72 hours. Daily dosing mildly worsened QoL, although QoL recovered after treatment cessation in all categories, except fatigue. Weekly dosing increased naïve T-cell populations. Daily dosing increased central memory cell populations and exhaustion markers. No disease progression was observed. In conclusion, treatment with eRapa was safe and well-tolerated. Daily dosing produced higher frequencies of lower grade toxicities and transient worsening of QoL, while weekly dosing impacted immune response. Future studies will verify clinical benefit and long-term tolerability.Prevention Relevance: There is an unmet medical need for a well-tolerated treatment capable of delaying progression of newly diagnosed low-grade prostate cancer. This treatment would potentially obviate the need for future surgical intervention and improve the perception of active surveillance as a more acceptable option among this patient population.

Correlation of tumor microenvironment from biopsy and resection specimens in untreated colorectal cancer patients: a surprising lack of agreement

Background

Colorectal cancer (CRC) tumor microenvironment (TME) characteristics, such as tumor infiltrating lymphocyte (TIL) densities and PD-L1 status, are predictive of recurrence, disease-free survival, and overall survival. In many malignancies, TME characteristics are also predictive of response to immunotherapy. As window of opportunity studies using neoadjuvant immunotherapy become more common and treatment guidelines incorporate TME features, accurate assessment of the pre-treatment TME using the biopsy specimen is critical. However, no study has thoroughly evaluated the correlation between the TMEs of the biopsy and resection specimens.

Methods

We conducted a retrospective analysis of patients with stage I–III CRC with matched biopsy and resection specimens. CD3+, CD4+, CD8+, and FoxP3+ lymphocyte populations at the center of tumor (CT) and invasive margin (IM) and tumor PD-L1 status in the biopsy and resection specimens were evaluated. TIL populations were compared using Mann–Whitney U tests or Student’s t tests and correlated using Pearson r.

Results

CD3+ and CD4+ densities were significantly higher in the CT of the biopsy relative to the resection specimen Comparing biopsy and resection specimens, no TIL population at either the CT or IM had a correlation coefficient > 0.5. Determining PD-L1 status based on biopsy tissue resulted in a sensitivity of 37.1%, specificity of 81.4%, and accuracy of 61.5%.

Conclusions

These findings demonstrate significant discordance between the TME of the biopsy and resection specimens. Caution should be used when basing treatment decisions on pre-treatment endoscopic biopsy findings and when interpreting changes in the TME between pre-treatment biopsy and resection specimens after neoadjuvant therapy.

Electronic supplementary material

The online version of this article (10.1007/s00262-020-02784-5) contains supplementary material, which is available to authorized users.

Final analysis of a phase I/IIa trial of the folate-binding protein-derived E39 peptide vaccine to prevent recurrence in ovarian and endometrial cancer patients

BACKGROUND

E39, an HLA-A2-restricted, immunogenic peptide derived from the folate-binding protein (FBP), is overexpressed in multiple malignancies. We conducted a phase I/IIa trial of the E39 + GM-CSF vaccine with booster inoculations of either E39 or E39' (an attenuated version of E39) to prevent recurrences in disease-free endometrial and ovarian cancer patients(pts). Here, we present the final 24-month landmark analysis.

PATIENTS AND METHODS

HLA-A2 + patients receiving E39 + GM-CSF were included in the vaccine group (VG), and HLA-A2- pts (or HLA-A2 + patients refusing vaccine) were followed as the control group (CG). VG group received 6 monthly inoculations as the primary vaccine series (PVS) and were randomized to receive either E39 or E39' booster inoculations. Demographic, safety, immunologic, and disease-free survival (DFS) data were collected and evaluated.

RESULTS

Fifty-one patients were enrolled; 29 in the VG and 22 in the CG. Fourteen patients received <1000 μg and 15 received 1000 μg of E39. There were no clinicopathologic differences between VG and CG or between dose groups. E39 was well tolerated. At the 24 months landmark, DFS was 55.5% (VG) vs 40.0% (CG), P = 0.339. Patients receiving 1000 μg and boosted patients also showed improved DFS (P < 0.03). DFS was improved in the 1000 μg group after treatment of primary disease (90.0% vs CG:42.9%, P = 0.007), but not in recurrent patients. In low-FBP expressing patients, DFS was 100.0% (1000 μg), 50.0% (<1000 μg), and 25.0% (CG), P = 0.029.

CONCLUSIONS

This phase I/IIa trial reveals that E39 + GM-CSF is safe and may be effective in preventing recurrence in high-risk ovarian and endometrial cancer when optimally dosed (1000 μg) to FBP low patients being treated for primary disease.

Abstract CT208: Prior vaccination with the autologous Tumor Lysate Particle Loaded Dendritic Cell (TLPLDC) Vaccine may impact clinical outcomes in melanoma patients treated with systemic therapies and re-vaccination

Background: Melanoma is an immunogenic cancer, yet only 50-60% of tumors respond to current immunotherapy. The autologous tumor lysate, particle loaded, dendritic cell (TLPLDC) vaccine may potentiate an immune response by stimulating T-cells. We are conducting a phase IIb double-blinded randomized trial of TLPLDC to prevent recurrence after resection. Patients who recurred were offered enrollment in an open-label TLPLDC vaccine trial along with standard therapy. Here, we describe characteristics and clinical outcomes of recurred patients that continued on open label TLPLDC vaccination.

Methods: Patients with resected no evidence of disease (NED) stage III/IV melanoma were randomized to TLPLDC vs. empty yeast cell wall particle (YCWP) loaded DC in a 2:1 fashion. TLPDC is created by loading autologous tumor lysate into YCWP. This is then introduced ex vivo to the patient’s DC for phagocytosis. 1-1.5x106TLPLDCs are given via intradermal injection monthly x4 followed by boosters at 6 and 9 months. Patients who recurred after receiving TLPLDC (vaccine group, VG) or after empty YCWP (control group, CG) on the trial (primary endpoint) were offered open label TLPLDC vaccination with same dosing schedule along with standard therapy as determined by the patient’s treatment team. Disease status is measured by RECIST criteria.

Results: To date, 23 (14 VG and 11 CG) patients have enrolled and been vaccinated, with median follow up (fu) of 7.86 months (mo). The patients received the following additional therapies: surgery, gamma-knife, check point inhibitor, radiation, TVEC, BRAF/MEK, and imantinib. No related toxicities &gt; grade 2 were observed. Of 14 VG patients, 5 were NED when re-enrolled, 9 had measurable disease (MD). Of these, 11 have followed up data, 9 (82%) show disease control (5/5 NED patients remain NED, 4/6 with MD show SD), while 2 (18%) have progressed. Of 9 CG patients, 4 were NED and 5 had measurable disease at time of re-enrollment. Of these, 8 have followed up, 5 (62%) show disease control (2/4 NED remain NED, 1/4 with MD shows regression, 2/4 SD), while 3 (38%) have progressed (2/4 NED, 1/3 with MD).

Conclusion: Open label administration of TLPLPDC vaccine after recurrence is demonstrated as a safe therapy and shows potential clinical benefit when combined SOC therapy. Further study is warranted to determine if prior exposure to TLPLDC may provide clinical benefit after the first episode of disease recurrence.

Citation Format: Annelies T. Hickerson, Guy T. Clifton, Tommy A. Brown, Jessica L. Cindass, John W. Myers, Timothy J. Vreeland, Diane F. Hale, Kaitlin M. Peace, Doreen O. Jackson, Garth Herbert, Xianzhong Yu, Thomas E. Wagner, George E. Peoples. Prior vaccination with the autologous Tumor Lysate Particle Loaded Dendritic Cell (TLPLDC) Vaccine may impact clinical outcomes in melanoma patients treated with systemic therapies and re-vaccination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT208.

Immunologic responses in triple-negative breast cancer patients in a randomized phase IIb trial of nelipepimut-S plus trastuzumab versus trastuzumab alone to prevent recurrence

556

Background: Breast cancer (BC) patients (pts) expressing low levels of HER2 by (immunohistochemistry (IHC) 1-2+) are not eligible for trastuzumab (Tz). However, in a randomized phase 2b trial, triple negative BC (TNBC) pts demonstrated a significantly better DFS with nelipepimut-S (NPS) + Tz vs Tz alone. Here, we assess the ex vivo and in vivo immune responses (IR) in both arms. Methods: Disease-free pts (n = 275) with HER2 IHC 1-2+, non-amplified BC who were node positive and/or had TNBC were randomized 1:1 to granulocyte-macrophage-colony stimulating factor (GM-CSF) or NPS+GM-CSF. ±NPS was given every 3 weeks x 6 followed by 4 boosters every 6 months (mo). All pts received Tz concurrently for 1 year per label regimen and were followed for recurrence. IR were evaluated ex vivo by clonal expansion of NPS-specific cytotoxic T lymphocytes (CTL) by dextramer-staining/flow cytometry at time points over 3 years. In vivo IR were assessed by delayed type hypersensitivity (DTH) reactions periodically. Results: The trial enrolled 97 TNBC pts; 60 had 4 timepoints available for analysis (37 NPS + Tz pts; 23 Tz pts). The NPS+Tz group exhibited increases in CTL frequencies vs baseline: 208%, 303%, 379% at 18, 24 and 30 mo, respectively. NPS+Tz pts’ mean CTL frequencies increased from 0.029 ±0.001% at baseline to 0.112±0.026% at 30 mo (p = 0.01) compared to Tz pts who were 0.027 ±0.001% at baseline and 0.057 ±0.016% at 30 mo (p = 0.71). Only 4 NPS+Tz pts recurred as compared to 13 in the Tz arm. While limited by low numbers, recurrent NPS + Tz pt did not mount an IR by ex vivo assessment (range: 0.0 - 0.026%) or by DTH (all measurements: 0 mm), while non-recurrent pts mounted both clonal CTL expansion (range: 0.000- 0.33%) and enhanced DTH (range: 0.0- 80.5mm). Conclusions: NPS+Tz combination is more efficacious in generating time-dependent antigen (NPS)-specific CTL by both ex vivo and in vivo measures vs Tz. Based on these preliminary data, it appears that both ex vivo and in vivo IR to NPS were attenuated in pts with TNBC recurrence. Further analysis of read-outs from these assays to validate the relationship of IRs to clinical effect seen with NPS+Tz in TNBC pts is underway. Clinical trial information: NCT02297698.

Clinical efficacy of vaccination with the autologous tumor lysate particle loaded dendritic cell (TLPLDC) vaccine in metastatic melanoma

e21025

Background: The treatment of melanoma has changed drastically with the advent of immunotherapy. The autologous tumor lysate, particle loaded, dendritic cell (TLPLDC) vaccine stimulates T-cells and may work synergistically with other immunotherapies. Here, we describe results in patients (pts) with metastatic melanoma (MM) treated with the TLPLDC vaccine together with other approved therapies. Methods: The TLPLDC vaccine is created using autologous tumor lysate loaded yeast cell wall particles to prime autologous dendritic cells ex-vivo. 1-1.5x106 TLPLDCs are given via intradermal injection monthly x 4 followed by boosters at six and nine months (mo). Pts who recurred while enrolled in our adjuvant phase IIb trial of the TLPLDC vaccine and pts with MM with measurable disease enrolled in a separate phase I/IIa trial were offered vaccination of TLPLDC vaccine in an open-label fashion in addition to other approved therapies as determined by their treating physician. Tumor response is measured by RECIST 1.1 criteria. Results: To date, 50 pts have been enrolled in the two trials (25 pts in each). Of the 42 pts with measureable disease, 30 pts received at least one dose of the vaccine, 11 progressed prior to vaccine administration, and 1 is pending. 2 pts withdrew at 2 and 7 mo. Of the remaining 28 evaluable pts, 13 pts had progressive disease with a median follow-up (f/u) of 3 (range 0-12) mo, 12 pts had stable disease with a median f/u of 7.5 (range 1-23) mo, 2 pts had a partial response with f/u of 7 and 13 mo, and one pt had a complete response with 18 mo of f/u. Overall, in pts with measureable disease, the disease control rate was 54% (15/28) and objective response rate was 11% (3/28). 8 pts were without measurable disease at enrollment, 3 recurred at a median f/u of 8 mo and 5 remain disease-free at a median of 26 mo f/u. No grade ≥ 3 toxicities were observed with combination TLPLDC vaccination and approved systemic therapies. Conclusions: Vaccination with the TLPLDC vaccine in combination with systemic approved therapies in MM pts is well tolerated and may provide clinical benefit in patients with and without measurable disease. Clinical trial information: NCT02678741.

Association of intratumoral FoxP3 T-regulatory lymphocytes and perineural invasion in colorectal adenocarcinoma

51

Background: In colorectal cancer, higher densities of lymphocytes in the tumor microenvironment (TME) have been associated with better clinical outcomes. FoxP3+ regulatory T-cells (Tregs) are a subset of lymphocytes that play an immunosuppressive role in the TME. However, the impact of Tregs in the TME in colon cancer prognosis is more controversial. We evaluated the densities of FoxP3+ Tregs at multiple locations in matched endoscopic biopsies and resection specimens from patients with colonic adenocarcinoma to assess concordance of Treg densities between locations, and the association with prognostic factors. Methods: Patients with banked, matched endoscopic biopsies and surgically resected colon adenocarcinoma specimens from a single institution from 2006-2016 were selected for evaluation. Paraffin embedded tissue samples were cut and stained with FoxP3 immunohistochemical stain. The densities of FoxP3 positive cells were counted within a 1 mm2 area at the center of the tumor and at the invasive margin. The densities of FoxP3 positive lymphocytes were compared between the center and invasive margin, and to prognostic factors. Results: 107 matched endoscopic biopsies and surgical resection specimens were evaluated. A moderate-strong correlation was noted in levels of FoxP3+ cells between endoscopic biopsies and resected specimens at the center of the tumor (r= 0.68) and invasive margin (r=0.69). Higher FoxP3 densities were associated with a decreased rate of perineural invasion (P= 0.040). Levels of Tregs in endoscopic biopsies were correlated with the levels in the larger tumor of resected colon adenocarcinoma specimens. There was a weak correlation between increased density of Tregs and lower anatomic stage (R2 = 0.05). Conclusions: Tregs are a potential biomarker that can be evaluated in neoadjuvant immunomodulatory therapies in clinical trials to assess for response. Moreover, Treg levels are associated with perineural invasion, a predictive factor for decreased response to chemotherapy, underscoring the potential for immunomodulatory therapies in colorectal adenocarcinoma.

Paradoxical effect of regulatory T-cell density in the invasive margin on colon cancer disease-free survival

47

Background: Increased numbers of FoxP3+ regulatory T cells (Treg), an immunosuppressive T cell subpopulation, in the tumor microenvironment (TME) has been associated with decreased recurrence risk in colon cancer. We assessed the association of Treg levels and disease-free survival (DFS) to confirm correlation with recurrence risk and to evaluate the impact on DFS in patients with colon cancer. Methods: Cases of colonic adenocarcinoma with endoscopic biopsies who had curative resection were collected from 2006-2016. The tissue sections were stained with FoxP3 immunohistochemical stain. FoxP3+ cells (Tregs) were counted with a digital imager software program and reported as cells per square mm. DFS from time of surgery was determined with a retrospective chart review. FoxP3 levels were compared with a Man-Whitney U test and DFS was compared with a Spearman’s test and regression. Results: 109 matched endoscopic biopsy colonic adenocarcinoma specimens were gathered. 94 cases had at least 4 months of follow up and were analyzed. The recurrence rate was 21.3% (20/94) with a median recurrence time of 13.5 months. The median time to follow up in patients with no recurrence was 39 (range 4-116) months. Tregs in those that recurred had a mean density of 152 (range 9-1267) at the invasive margin compared to 251 (range 15-485) in the cases that did not yet recur (p = 0.005). The same association was observed with Treg density in the center of the tumor (p = 0.03). In the cases that had a recurrence, there was a moderate, inverse correlation between Tregs at the invasive margin and time to recurrence (Spearman’s correlation coefficient = -0.46, p = 0.04.) A logarithmic inverse relationship between Tregs at the invasive margin and time to recurrence was observed (Correlation coefficient -0.63, p = 0.003). Conclusions: Treg density in endoscopic biopsies in colon adenocarcinoma is associated with recurrence risk, consistent with previously reported observations. Paradoxically, in patients who did recur, higher Treg density was associated with shorter time to recurrence. This discordant relationship of Treg density and colon cancer prognosis warrants further investigation.

Abstract P2-09-09: Initial safety and efficacy of a phase I/IIa trial of a modified whole tumor cell targeted immunotherapy in patients with advanced breast cancer

Background: SV-BR-1-GM is a GM-CSF transfected breast cancer cell line which expresses HLA class I & II antigens. In a previous clinical trial, a partial response of widely metastatic breast cancer was seen in a patient who matched SV-BR-1-GM at HLA-DRB3*02:02. Here we report the safety and efficacy analysis with immunologic correlates of response in the initial patients in a phase I/IIa trial of SV-BR-1-GM in patients with advanced breast cancer

Methods: This phase I/IIa trial enrolled patients with recurrent and/or metastatic breast cancer refractory to standard chemotherapy/targeted-therapy. Patients received low-dose cyclophosphamide 2-3d prior to intradermal injection of SV-BR-1-GM (20x106 cells divided into 4 sites) and interferon-α into the inoculation sites (10,000 IU/site) ˜2 & 4 days subsequently. Cycles were 2 weeks x3 then q mo x 3. Adverse events (AE) were evaluated after each inoculation and graded via CTCAE v4.03. Immunologic response was measured by delayed type hypersensitivity (DTH) after each inoculation. Disease response was evaluated radiographically q3 mo and as clinically indicated (clinical trial NCT03066947).

Results: To date, twenty-two patients have been enrolled and 17 have been inoculated for a total of 39 SV-BR-1-GM inoculations given. Per inoculation, the maximum related AE was grade 1 in 64%, grade 2 in 7.7%, and grade 3 in 7.7%. There were no related grade &gt;3 or unexpected AE. Efficacy data is available on the first six (Table). Tumor regression was seen in 2 patients. 01-002 presented with liver, bone and 20 classic miliary lung metastases (up to 9mm). This subject previously received 7 chemotherapy regimens. She matched SV-BR-1-GM at Class I & II HLA loci. Imaging at 3 mo showed virtually complete regression of all 20 identifiable lesions in the lungs. This response was maintained at 6 mo but the subject was taken off protocol because of disease progression (liver and bone). 01-005, matching HLA-A*24:02, had notable regression of cutaneous lesions, but progressed in pleural and pericardial effusions, had irreversible cardiac arrest (unlikely related). DTH increased in 01-002 from 4mm (first dose) to 47mm (8th dose). Three of 3 patients evaluated developed antibodies responses (as measured by flow cytometry with SV-BR-1) including 01-002. Interleukin 8 also increased in 01-002.

Conclusions: SV-BR-1-GM in this regimen appears to be safe and well-tolerated. In this initial exploratory analysis, SV-BR-1-GM can produce regression of pre-treated metastatic breast cancer correlating with an immunologic response. HLA matching is being evaluated as a predictor of response.

PatientAgeMetastatic Sites# Prior RegimensHLA Matches# of CyclesTumor Regression?01-00146Pleura, Lymph Nodes7 chemo/bio, 5 hormonalDRB3*02:021No01-00273Lung, Liver, Bone6 chemo, 1 hormonalA*24:02, DRB3*02:028Lungs01-00554Lymph nodes, Pleura, Skin3 chemo/bioA*24:022Skin02-00170Lymph nodes1 chemo/bioNone1No02-00361Bone, Brain3 chemoNone6No02-00474Lymph nodes, Cutaneous3 chemo/bio, 1 hormonalDRB3*02:022Lost to Follow-up

Citation Format: Bhattacharya S, Holmes JP, Calfa C, Lukas J, Tan-Chiu E, Clifton GT, Peoples GE, Lacher M, Wiseman CL, Williams WV. Initial safety and efficacy of a phase I/IIa trial of a modified whole tumor cell targeted immunotherapy in patients with advanced breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-09.

Abstract P2-09-01: Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients

Background:HER2 low-expressing (LE) (IHC 1-2+, FISH non-amplified) breast cancer (BC) patients (pts) have not benefited from HER2-directed therapy despite HER2 antigen availability. Triple negative BC (TNBC), in particular, is immunogenic and in need of additional therapeutic options. We have previously shown the HER2-derived nelipeptimut-S (E75) + GM-CSF (NeuVax) to be synergistic with trastuzumab (Tz) in pre-clinical and pilot clinical studies. In a planned interim analysis of a multi-center, prospective, randomized, single-blinded, placebo-controlled phase 2b trial of Tz + NeuVax vs Tz to reduce recurrence in HER2 LE, node-positive (NP) and/or triple negative BC (TNBC) pts, we previously reported that the NeuVax + Tz was safe without added cardiac toxicity and demonstrated a significant reduction of recurrences in TNBC pts. This analysis examines additional subsets in this trial.

Methods:HER2 LE, NP and/or TNBC pts who were clinically disease-free after standard therapy were randomized to receive Tz+NeuVax (vaccine group; VG) or Tz+GM-CSF (control group; CG). All pts received 1 yr of Tz per label. NeuVax or GM-CSF was given every 3 weeks x 6 starting with the 3rdTz dose, and then boosted every 6 months x 4. This pre-specified interim analysis was triggered 6 months after last enrollment. The primary endpoint is intention-to-treat 24 month disease-free survival (DFS) evaluated by log rank.

Results: Of 275 pts randomized in the study (VG n=136, CG n=139), 98 had TNBC (VG=53, CG=45). In the interim analysis, estimated disease-free survival (DFS) was assessed with a median follow up of 18.8 months. No significant clinicopathologic differences were seen between treatment groups. In the TNBC group, estimated DFS was higher overall in VG vs CG (91.9% v 69.9%, p=0.023; hazard ratio [HR] 0.29, 95% confidence interval [CI] 0.09-0.90). On TNBC subgroup analysis, estimated DFS was higher in VG vs CG among pts who received neoadjuvant chemotherapy (VG n=35, CG n=31; HR 0.26, CI 0.07-0.93; p=0.03), HER2 IHC 1+ BC (VG n=34, CG n=28; HR 0.20, CI 0.04-0.96; p=0.03), pts who were AJCC 7thedition stage I/II (VG n=37, CG n=27; HR incalculable, no recurrences in the VG, p=0.008), and pts 351yr of age (VG n=32 & CG n = 26; HR 0.26 CI 0.07,0.94; p=0.009). HRs did not appreciably vary based on the histologic grade or presence of lymphovascular invasion.

Conclusion:Examining the subgroups from the pre-specified interim analysis demonstrates a highly significant clinical benefit in TNBC pts overall. Within the TNBC cohort, specific benefit was seen in pts who received chemotherapy neoadjuvantly, expressed lower HER2, were earlier stage, and were older in age. These factors may help enrich the TNBC population targeted in a definitive Phase 3 study in TNBC patients with residual disease after neoadjuvant chemotherapy.

Citation Format: Clifton GT, Kemp Bohan PM, Hale DF, Myers JW, Brown TA, Holmes JP, Vreeland TJ, Litton JK, Murthy RK, Mittendorf EA, Peoples GE. Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-01.

Initial phase I/IIa trial results of an autologous tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine in patients with solid tumors

INTRODUCTION

Tumor vaccines use various strategies to generate immune responses, commonly targeting generic tumor-associated antigens. The tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine is produced from DC loaded with autologous tumor antigens, creating a patient-specific vaccine. Here, we describe initial phase I/IIa trial results.

METHODS

This trial includes patients with any stage solid tumors, ECOG ≤1, and >4 months life-expectancy. A personalized vaccine is created using 1 mg of tumor and 120 ml blood (to isolate DC). Primary vaccination series (PVS) is four monthly inoculations. Patients are followed per standard of care (SOC). Endpoints include safety and tumor response (RECIST v1.1).

RESULTS

44 patients were enrolled and vaccinated consisting of 31 late stage patients with residual/measurable disease, and 13 disease-free patients after SOC therapies. While 4 patients progressed before completing the PVS, 12/31 (39%) demonstrated clinical benefit (2 complete responses, 4 partial responses, 6 stable disease). In the adjuvant setting, 46% of late stage patients remain disease free at a median of 22.5 months.

CONCLUSIONS

The TLPLDC vaccine is scalable, generates a personalized DC vaccine, and requires little autologous tumor tissue and few DC. The vaccine is safe, with primarily grade 0-2 toxicities, and nearly 40% clinical benefit rate in varied tumors, warranting further study.

TRIAL REGISTRATION

ISRCTN81339386, Registered 2/17/2016.

Tumor lysate particle loaded dendritic cell vaccine: preclinical testing of a novel personalized cancer vaccine

Aim: We developed a novel approach to efficiently deliver autologous tumor antigens to the cytoplasm of dendritic cells (DC) using yeast cell wall particles (YCWP). Materials and Methods: Loading of YCWP, leakage of protein from loaded YCWP and cytoplasmic delivery of YCWP content was assessed using fluorescent-tagged experiments. Spectrophotometric analysis compared the epitope-specific T-cell responses following antigen presentation via YCWP versus exogenous loading. The in vivo effectiveness of tumor lysate (TL) particle loaded DC (TLPLDC) vaccine was assessed using murine melanoma models. Results: In fluorescence-tagged experiments, YCWP efficiently delivered antigen to the cytoplasm of DC. TLPLDC loading was more effective than conventional exogenous loading of DC. Finally, in murine melanoma models, TLPLDC outperformed an analogous dendritoma vaccine. Conclusion: The TLPLDC vaccine is commercially scalable and holds the potential of producing personalized vaccines.

Phase Ib trial of folate binding protein (FBP)-derived peptide vaccines, E39 and an attenuated version, E39': An analysis of safety and immune response

In this randomized phase Ib trial, we tested combining the E39 peptide vaccine with a vaccine created from E39', an attenuated version of E39. Patients with breast or ovarian cancer, who were disease-free after standard of care therapy, were enrolled and randomized to one of three arms. Arm EE received six E39 inoculations; arm EE' received three E39 inoculations followed by three E39'; and arm E'E received three E39' inoculations, followed by three E39. Within each arm, the first five patients received 500 μg of peptide and the remainder received 1000 μg. Patients were followed for toxicity, and immune responses were measured. This initial analysis after completion of the primary vaccination series has confirmed the safety of both vaccines. Immune analyses suggest incorporating the attenuated version of the peptide improves immune responses and that sequencing of E39 followed by E39' might produce the optimal immune response.

TRIAL REGISTRATION

NCT02019524.

A prospective, randomized, blinded, placebo-controlled, phase IIb trial of an autologous tumor lysate + yeast cell wall particles (YCWP) + dendritic cells (DC) vaccine vs unloaded YCWP + DC and embedded phase I/IIa trial with tumor lysate particle only (TLPO) vaccine in stage III and stage IV (resected) melanoma to prevent recurrence

TPS201

Background: Melanoma is a potentially lethal skin malignancy; patients with stage III/IV resected disease have a recurrence rate of 50-90%. Adjuvant checkpoint inhibitor immunotherapy decreases the risk of recurrence but also causes significant immune-related toxicity. Vaccines are a promising strategy for patients with high risk melanoma. The optimal time to intervene may be in the adjuvant setting after attaining a disease-free state through standard of care therapies. Our strategy uses autologous tumor lysate (TL) in a yeast cell wall particle (YCWP) to load dendritic cells (DC) ex vivo. The tumor lysate particle loaded dendritic cell (TLPLDC) vaccine is then given to prevent melanoma recurrences. An alternate vaccine delivery method that we are evaluating utilizes the tumor lysate particle-only (TLPO) technique, in which tumor lysate is loaded into capped YCWP and injected intradermally, allowing an in vivo uptake by the patient’s dendritic cells. Methods: We are performing a prospective, randomized, blinded, placebo-controlled phase IIb trial in patients with resected stage III/IV melanoma who have been rendered disease-free but remain at high risk of recurrence. The study will utilize the TLPLDC strategy vs placebo (2:1) in 120 patients, followed by a bridging study of TLPO vs TLPLDC (2:1) in 60 patients. Both TLPLDC and TLPO inoculations will be monthly x3, followed by boosters at 6, 12, and 18 months. Primary endpoints will be disease free survival (DFS) at 24 months in the TLPLDC arm, and overall safety in the TLPO arm. We have completed enrollment in the phase IIb portion of the study. Clinical trial information: NCT02301611.

Immunologic efficacy of E39 & E39' vaccination in a phase I/IIa trial in ovarian and endometrial cancer patients

75

Background: The treatment options for cancer are ever-evolving & now include vaccines targeting tumor-specific immunogenic peptides to induce tumor cytolysis. Folate binding protein (FBP) is a tumor-associated antigen (TAA) highly expressed in most endometrial & ovarian cancers (Ca), shielded from the normal immune system. The most promising FBP peptides are E39 & an attenuated form, E39' (aka J65). In our most recent phase I/IIa trial we evaluated an E39+GM-CSF inoculation series at 3 doses (VG) vs controls (CG) as well as booster vaccination with E39 or E39' after the initial inoculation series. Here we present the immunologic data from this phase I/IIa trial. Methods: Patients (pts) with ovarian or endometrial Ca who were disease-free after standard of care therapy but at risk for recurrence were enrolled. HLA-A2+ pts were vaccinated in a 3+3 dose escalation of 100mcg, 500mcg, & 1000mcg. The remaining pts received 1000mcg inoculations. Vaccine was given every 3-4 weeks for a total of 6 inoculums. Pts were then offered to participate in booster vaccination with 9 pts randomized to receive E39 & 9 pts E39'. FBP expression level was measured on the resected disease. Overall immunologic response & by subgroups was measured by delayed type hypersensitivity (DTH) & ELISPOT in the VG. Results: A total of 29 pts were vaccinated. Mean DTH prior to the initial dose of E39 was 5.74mm & after final dose was 10.33mm (p = 0.018). Mean overall ELISPOT change over time through 18 months was +69.1 when compared to baseline (p = 0.675). At 18 months, mean ELISPOT increased by 97.1 in 1000mcg vs -57.0 in < 1000mcg dosed pts (p = 0.047) & by +255.33 in pts with > average initial DTH vs -0.75 in < average initial DTH (p = 0.004) when compared to baseline. Immunological analyses were not significantly different between FBP hi/lo expression or E39 vs E39’ booster (p > 0.05). Conclusions: E39 demonstrated significant overall immunogenicity on in vivo testing as measured by DTH. Ex vivo analysis (ELISPOT) suggests that E39 is more immunogenically efficacious in pts with > average initial DTH & those who are optimally dosed (1000mcg). FBP expression level & E39 vs E39’ use in booster inoculations did not significantly impact in vivo or ex vivo immunogenicity. Clinical trial information: NCT01580696.

Interim analysis of a phase I/IIa trial assessing E39+GM-CSF, a folate binding protein vaccine, to prevent recurrence in ovarian and endometrial cancer patients

BACKGROUND

Folate binding protein(FBP) is an immunogenic protein over-expressed in endometrial(EC) and ovarian cancer(OC). We are conducting a phase I/IIa trial of E39 (GALE 301)+GM-CSF, an HLA-A2-restricted, FBP-derived peptide vaccine to prevent recurrences in disease-free EC and OC patients. This interim analysis summarizes toxicity, immunologic responses, and clinical outcomes to date.

METHODS

HLA-A2+ patients were vaccinated(VG), and HLA-A2- or -A2+ patients were followed as controls(CG). Six monthly intradermal inoculations of E39+250mcg GM-CSF were administered to VG. Demographic, safety, immunologic, and recurrence rate(RR) data were collected and evaluated.

RESULTS

This trial enrolled 51 patients; 29 in the VG and 22 in the CG. Fifteen patients received 1000mcg E39, and 14 received <1000mcg. There were no clinicopathologic differences between groups(all p ≥ 0.1). E39 was well-tolerated regardless of dose. DTH increased pre- to post-vaccination (5.7±1.5 mm vs 10.3±3.0 mm, p = 0.06) in the VG, and increased more in the 1000mcg group (3.8±2.0 mm vs 9.5±3.5 mm, p = 0.03). With 12 months median follow-up, the RR was 41% (VG) vs 55% (CG), p = 0.41. Among the 1000mcg patients, the RR was 13.3% vs 55% CG, p = 0.01. Estimated 2-year DFS was 85.7% in the 1000mcg group vs 33.6% in the CG (p = 0.021).

CONCLUSIONS

This phase I/IIa trial reveals that E39+GM-CSF is well-tolerated and elicits a strong, dose-dependent in vivo immune response. Early efficacy results are promising in the 1000 mcg dose cohort. This study proves the safety and establishes the dose of E39 for a larger prospective, randomized, controlled trial in HLA-A2+ EC and OC patients to prevent recurrence.

Trastuzumab Increases HER2 Uptake and Cross-Presentation by Dendritic Cells

Early-phase clinical trials evaluating CD8⁺ T cell-eliciting, HER2-derived peptide vaccines administered to HER2⁺ breast cancer patients in the adjuvant setting suggest synergy between the vaccines and trastuzumab, the mAb targeting the HER2 protein. Among 60 patients enrolled in clinical trials evaluating the E75 + GM-CSF and GP2 + GM-CSF vaccines, there have been no recurrences in patients vaccinated after receiving trastuzumab as part of standard therapy in the per treatment analyses conducted after a median follow-up of greater than 34 months. Here, we describe a mechanism by which this synergy may occur. Flow cytometry showed that trastuzumab facilitated uptake of HER2 by dendritic cells (DC), which was mediated by the Fc receptor and was specific to trastuzumab. In vitro, increased HER2 uptake by DC increased cross-presentation of E75, the immunodominant epitope derived from the HER2 protein, an observation confirmed in two in vivo mouse models. This increased E75 cross-presentation, mediated by trastuzumab treatment, enabled more efficient expansion of E75-specific cytotoxic T cells (E75-CTL). These results demonstrate a mechanism by which trastuzumab links innate and adaptive immunity by facilitating activation of antigen-specific T cells. On the basis of these data, we conclude that HER2-positive breast cancer patients that have been treated with trastuzumab may experience a more robust antitumor immune response by restimulation of T cells with the E75 peptide vaccine, thereby accounting for the improved disease-free survival observed with combination therapy. Cancer Res; 77(19); 5374-83. ©2017 AACR.

Routine Pre-Treatment MRI for Breast Cancer in a Single-Payer Medical Center: Effects on Surgical Choices, Timing and Outcomes

Introduction: Pre-operative MRI is being used with increasing frequency to evaluate breast cancer patients, but the debate surrounding risks and benefits of this use continues. At our institution, we instituted a standardized protocol for pre-operative MRI. Here, we compare patients seen prior to routine use of MRI to those seen after and examine effects on surgical choices, timing and outcomes.

Methods: This is a retrospective review of a prospectively collected database of all new invasive breast cancers seen from January 2007 to December 2012. The control group (CG) did not receive MRI, while the MRI group (MRG) underwent MRI according to our pretreatment protocol. Groups were compared with regards to basic demographics, initial surgical choices, need for re-excision, and surgical timing. The electronic medical records of patients in the MRG who underwent mastectomy as their initial surgery were examined closely to determine the main factors leading to their choice of surgery. Finally, correlation between findings on MRI and final surgical pathology was analyzed.

Results: Of 282 patients included, 38 were in the CG and 244 in the MRG; the groups were well matched. The MRG had a significantly higher percentage of patients choosing initial mastectomy (MRG: 47.1% vs CG 21.1%, p=0.003). Patients seen in the first 2 years of the study were less likely to choose mastectomy than those enrolled in the latter years (29.2%vs 48.6%, p=0.004). The MRG had a lower chance of return to the operating room for re-excision (15.2% vs 28.9%, p=0.035). The average time from initial imaging to initial surgery was approximately the same between groups (MRG: 39.7 days vs CG 42.1 days, p=0.45) and the MRG actually had shorter time to definitive (margin-negative) surgical management (MRG: 43.5 days vs CG: 50.3 days, p=0.079). One hundred-fifteen patients in the MRG underwent mastectomy as initial surgery. Of these, 64 (55.7%) had no additional findings on MRI and chose mastectomy based on patient preference; 30 patients (26.1%) (29 unilateral, 1 bilateral) had mastectomy because of MRI findings. Of the 31 breasts removed (29 unilateral and 1 bilateral mastectomies) because of MRI findings, 26 (83.9%) had histologic findings that correlated with the MRI findings, while 5 (16.1%) did not.

Conclusion: Patients receiving routine pre-treatment MRI had an increased mastectomy rate, but had a lower re-excision rate. We found no delay to initial surgical therapy and, perhaps more importantly, a slight decrease in time to margin-negative surgical therapy in the MRI group. Women choosing mastectomy after MRI did so because of personal preference over half of the time, while MRI findings influenced this choice in 26% of these women. When MRI findings did lead to mastectomy, these findings were confirmed by pathology results in the vast majority of cases.

Abstract CT162: Pre-specified interim analysis in a prospective, randomized phase II trial of trastuzumab vs trastuzumab + NeuVax to prevent breast cancer recurrence in HER2+ breast cancer patients

Introduction: The HER2-targeted monoclonal antibody, trastuzumab (Tz), is standard of care (SOC) for HER2-positive (HER2+) breast cancer (BCa) and has been shown to reduce recurrence. We have previously shown that NeuVax (E75 peptide + GM-CSF), a HER2-targeted peptide vaccine, is safe, immunogenic, and may have synergistic clinical efficacy when combined with Tz. Given the known cardiac toxicity of Tz, there is concern that adding a HER2-directed vaccine to Tz therapy may exacerbate this effect. We are currently enrolling patients (pts) in a multi-center, prospective, randomized, single-blinded, placebo-controlled phase II trial combining Tz and Neuvax in the adjuvant setting to prevent recurrence in HER2+ BCa pts. Here, we present the initial safety data.

Methods: HLA-A2/A3+ BCa pts with stage I-III HER2+ disease at high risk for recurrence (pts not achieving complete response after Tz-containing neoadjuvant therapy or those undergoing up-front surgery with any node-positive disease if ER/PR- or ≥4 positive nodes if ER/PR+) were enrolled after SOC surgery, radiation and neo-adjuvant/adjuvant chemotherapy with approved Tz-containing regimen. Pts were randomized to receive Tz and NeuVax in the vaccine group (VG) or Tz and GM-CSF only in the control group (CG). Pts received vaccinations of NeuVax or GM-CSF intradermally every 3 weeks for 6 total vaccinations (primary vaccine series, PVS) starting with the third dose of Tz maintenance therapy. Starting 6 months after the completion of the PVS, pts received four booster inoculations, one every 6 months. Cardiac ejection fraction (EF) was assessed by either echo or MUGA at baseline and serially during treatment. Demographic and safety data were collected and analyzed. Safety analysis was initiated after enrollment of the 50th patient.

Results: To date, we have enrolled 50 pts (VG n=22, CG n=28). There were no significant clinicopathologic differences between groups. There were no related grade 4 or 5 toxicities and no differences in related toxicities between the VG and CG (Grade 1: 96% vs 98.5%; Grade 2: 3.2% vs 1.5%; Grade 3: 0.8% vs 0%, p=0.14). There was no significant reduction in EF pre- to post-treatment in either group (VG: 61.1±5.4% vs 60.1±4.8%, p=0.55; CG: 62.3±5.7% vs 61.9±4.0%, p=0.74) and there was no difference in change between groups (p=0.54).

Conclusion: The combination of Tz and Neuvax in HER2+ BCa pts is well tolerated and the cardiac effects from Tz are not worsened by the addition of NeuVax. We will continue to enroll up to our goal of 100 pts in this ongoing trial, and will report immunologic and clinical outcomes in the planned primary analysis after 24-months follow-up.

Citation Format: Kaitlin M. Peace, Jennifer K. Litton, Rashmi Murthy, Timothy J. Vreeland, Diane F. Hale, Doreen O. Jackson, John S. Berry, Alfred F. Trappey, Garth S. Herbert, Guy T. Clifton, Mark O. Hardin, George E. Peoples, Elizabeth A. Mittendorf. Pre-specified interim analysis in a prospective, randomized phase II trial of trastuzumab vs trastuzumab + NeuVax to prevent breast cancer recurrence in HER2+ breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT162. doi:10.1158/1538-7445.AM2017-CT162

Abstract CT036: Early trial results of an autologous tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine in ovarian cancer patients

Introduction: Late-stage ovarian cancer remains difficult to treat with 1-year disease free survival rates of roughly 55% and 40% in patients (pts) with stage III and IV disease, respectively1. To date, the majority of ovarian cancer vaccines have targeted specific tumor-associated antigens with little benefit. Our vaccine approach harnesses the most potent antigen presenting cell in the body, the dendritic cell (DC), and exposes these cells to the full repertoire of tumor antigens from an individual’s cancer. Autologous tumor lysate (TL) is loaded into yeast cell wall particles (YCWP) that are naturally and efficiently taken up into the pt’s DC ex vivo. This process uses a small amount of blood and tumor and can be completed in 48 hours. The autologous TL, particle-loaded, DC (TLPLDC) vaccine is then injected intradermally (ID). This vaccine is being tested in multiple tumor types, and here we present the results in ovarian cancer.

Methods: Pts with stage III or IV ovarian cancer were identified prior to surgical intervention for enrollment and tumor acquisition. Pts were treated with standard of care therapy, then enrolled in the per protocol (PP) phase I/IIa trial if disease-free or in an open label treatment registry (OTR) if they had measureable residual disease. A tumor sample (&gt;1mg) was collected at the time of surgery, and 120mL of blood (or 50mL after a single dose of Neupogen) was drawn to isolate the pt’s DC. TL was produced through freeze/thaw cycling and loaded into YCWP, which were introduced to DC for phagocytosis; thus creating an individualized TLPLDC vaccine for each pt. Each vaccine dose contained 1x106 TLPLDC, which was injected ID in the thigh. In the PP group, the primary vaccine series (PVS) consisted of monthly vaccination x3 followed by boosters at 6 and 12 months. In the OTR, the PVS consisted of monthly vaccination x4 followed by boosters every 3 months. Pts were monitored for toxicity and recurrence or progression of disease, respectively.

Results: A total of 15 pts have been treated to date, (PP: 8, OTR: 7 with 1 pt vaccinated on compassionate use). 100% of pts had successful creation of vaccine. Minimal toxicities (all ≤ grade 2) were reported. To date, in the OTR, 1 pt has shown a complete response, 1 has stable disease, and 4 have had progressive disease (PD; only 1 pt with PD completed the PVS). In the PP group, after a median follow up of 10.8 months, 3 pts (37%) have recurred (only 1 of these pts completed PVS), while 5 pts (63%) remain disease free.

Conclusions: We have shown that the TLPLDC vaccine can be made efficiently (requiring only a small amount of blood, tumor and time) and is safe and well-tolerated. Our results suggest that the vaccine is better suited for the adjuvant setting rather than pts with residual disease. This data provides justification for a larger clinical trial in stage III/IV ovarian cancer pts in the adjuvant setting.

1 Kurta M, et al. Prognosis and conditional disease-free survival among pts with ovarian cancer. J Clin Oncol. 2014;32(36):4102-12.

Citation Format: Kaitlin M. Peace, Timothy J. Vreeland, Guy T. Clifton, Diane F. Hale, Doreen O. Jackson, John S. Berry, Alfred F. Trappey, Garth S. Herbert, Mark O. Hardin, Pauline T. Nichol, Sook L. Yin, Xianzhong Yu, Thomas E. Wagner, George E. Peoples. Early trial results of an autologous tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine in ovarian cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT036. doi:10.1158/1538-7445.AM2017-CT036

Subgroup efficacy evaluation of the AE37 HER2 vaccine in breast cancer patients in the adjuvant setting

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Background: AE37 is a Ii-Key hybrid of the HER2 peptide AE36 (HER2776-790), which stimulates peptide-specific T cells. We have completed the active phase of a prospective, randomized, multi-center, phase II trial of the AE37 vaccine in the adjuvant setting. The primary analysis, performed after a median follow up (f/u) of 25 months (mo), did not show a significant difference in disease free survival (DFS) between vaccinated and control patients (pts). However, demonstrating the efficacy of cancer vaccines may require more time than other therapies, especially in malignancies with relatively late recurrences like breast cancer. Here, we present updated efficacy data after extended f/u in subgroups of pts stratified by clinicopathologic characteristics. Methods: Clinically disease-free, node positive or high-risk node negative pts with any level of HER2 expression were randomized to receive AE37 + GM-CSF (VG) or GM-CSF alone (CG) following standard of care therapy. Pts received 6 monthly intradermal inoculations during the primary vaccine series (PVS) followed by 4 boosters administered every 6 mo. Kaplan Meier and log rank analyses were performed from the time of the first inoculation in pts who completed at least the PVS, according to stage, node status, tumor size, HER2 expression and ER/PR status. Results: There were no clinicopathologic differences between groups in the 298 enrolled pts (VG = 153, CG = 145). The vaccine is safe and well tolerated. After a median f/u of 55 mo, there was a trend toward improved DFS in the VG among stage IIB/III pts (VG, n = 73, DFS 82% vs CG, n = 61, 67%, HR = 0.48, p = 0.06) and those with low HER2 expression (HER2 LE, VG, n = 68, 89% vs CG, n = 66, 51%, HR = 0.47, p = 0.1). Improved DFS in the VG was documented in patients with both stage IIB/III disease and HER2 LE (VG, n = 39, 90% vs CG, n = 38, 32%, HR 0.3, p = 0.02) and triple negative (TNBC) pts (VG, n = 21, 89% vs CG, n = 21, 0%, HR 0.26, p = 0.05). Conclusions: The AE37 vaccine is safe and well tolerated and has statistically significant efficacy in stage IIB/III pts with HER2 LE and in TNBC pts. This justifies further evaluation in a phase III study enrolling stage IIb/III pts not eligible for trastuzumab treatment and the very high risk TNBC group. Clinical trial information: NCT00524277.

Evaluation of Attenuated Tumor Antigens and the Implications for Peptide-Based Cancer Vaccine Development

INTRODUCTION: Peptide vaccines offer anti-tumor efficacy with very low toxicity. However, repeat stimulation with an immunogenic peptide leads to activation induced cell death (AICD), decreasing efficacy. We engineered variants of an immunogenic peptide (E39) and tested their ability to induce a robust, sustainable immune response.

METHODS: Multiple variants of E39 were created by exchanging 1 or 2 amino acids. We tested the PBMC proliferation, cytokine production and cytolytic activity induced by each variant peptide. RESULTS: Repeated stimulation with E39 likely led to in vitro AICD, while stimulation with E39' led to T-cell proliferation with less evidence of AICD, modest cytokine production and high CTL activity. CONCLUSIONS: E39' appears to be the optimal variant of E39 for inducing effective long-term immunity.

A novel cancer vaccine platform utilizing autologous tumor lysate loaded into capped yeast cell wall particles

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Background: Our current tumor lysate, particle-loaded, dendritic cell (TLPLDC) vaccine employs yeast cell wall particles (YCWP) to deliver antigen to DC ex vivo and is being tested in a randomized phase IIb trial. This strategy may be improved by injecting TL-loaded YCWP as an intradermal vaccine, with in vivo DC uptake. Silicate capping should allow YCWP to retain TL longer and stimulate DC uptake. Here, we present preclinical data on the tumor lysate, particle only (TLPO) vaccine concept vs. TLPLDC. Methods: To test the TLPO concept, YCWP were loaded with fluorescence (flr) labeled albumin and capped (cp) vs. uncapped (ucp) particles were compared for flr leak. Next, YCWP were added to cultured macrophages to evaluate DC uptake. Cells were then lysed, centrifuged, and flr in the cytoplasm vs. organelles measured. 3 C57B mice were then injected with 100ml NaCl, 106empty cp YCWP, or 1mcg GM-CSF. 5 hours (hr) post-injection, 100ml NaCl was injected into the same site, withdrawn, and examined via microscope to count monocytes. TLPO was compared to TLPLDC in a B16 murine melanoma survival model. Finally, 4 grey horses with equine melanoma were treated with autologous TLPO, injected biweekly for 4 vaccinations. Target lesions were assessed over 6 months. Results: Compared to ucp YCWP, cp had decreased flr leak at 1 (15.8% vs. 24.7%) and 2 hr (6.7% vs. 16.6%), increased uptake by DC (2hr flr readings 11065 vs. 3928) and higher delivery to DC cytoplasm (68.9% vs. 48.8%). Empty cp YCWP showed increased recruitment of monocytes (276/hpf) vs. GM-CSF (55/hpf) or NaCl alone (18/hpf). In the B16 murine melanoma model, the median survival time in days was 21 for controls (n=5), 42 for TLPLDC (n=10), and 56 for TLPO (n=20). At 6 months, the equine model revealed 1 complete and 3 partial responses (50%, 68%, and 45% tumor reduction). Conclusions: Silicate capping of the YCWP effectively limits leakage of contents, improves uptake by DC and delivery to the cytoplasm without the need for GM-CSF. In early animal studies, TLPO appears to have equivalent efficacy to TLPLDC, but eliminates the need for in vitro DC loading. We plan to perform a bridging study comparing TLPO to TLPLDC after enrollment is complete in our phase IIb TLPLDC melanoma trial.

Abstract P6-10-04: Determining the optimal vaccination strategy using a combination of the folate binding protein (FBP) peptide vaccine (E39+GM-CSF) and an attenuated version (E39') to maximize the immunologic response in breast cancer patients

BACKGROUND FBP is overexpressed in 20-50% of breast(B) cancers(Ca) and roughly 90% of endometrial(E) and ovarian (Ov) Ca. E39 (FBP191-199, EIWTHSYKV)+GM-CSF is an HLA-A2 restricted FBP peptide vaccine, which has been shown to generate significant in vivo immunologic response(IR) in a phase I/IIa trial in E Ca and Ov Ca patients (pts). There is a risk of inducing immunologic tolerance after multiple inoculations with a highly immunogenic vaccine. Thus, we are investigating a novel vaccination series using combinations of E39 and E39' (EIWTFSTKV, an attenuated version of E39) in a phase Ib, randomized, single-center trial. We are assessing short and long-term IR. Here, we present the initial IR analysis to the primary vaccination series (PVS) within B Ca pts.

METHODS HLA-A2 positive B or Ov Ca pts were enrolled after completion of standard of care therapy and randomized into three arms: EE (6 inoculations of E39); EE'(3 inoculations of E39, then 3 of E39'); or E'E(3 of E39', then 3 of E39). Theoretically, due to lower FBP expression and less aggressive chemotherapy regimens, B Ca pts are more antigen naïve and have a less suppressed immune system. Thus, only B Ca pts were included in this analysis. The PVS includes 6 inoculations total (R1-R6), one every 3-4 weeks, and containing 250mcg GM-CSF+500mcg peptide in the first 5 pts per arm and 1000mcg of peptide in second 5 pts. To assess the in vivo IR, local reaction(LR) was measured 48 hours after each inoculation (R1-R6), and delayed type hypersensitivity(DTH) was measured pre-PVS (R0), 1, and 6-months post-PVS (RC1, RC6). Ex vivo IR was measured via dextramer assay for E39-specific CD8+ T-cells at R0, RC1, and RC6. Statistical analyses were completed using appropriate tests.

RESULTS Thirty-five B Ca pts were enrolled, with 27 completing the PVS (EE n=10, EE' n=8, E'E n=9). No clinicopathologic differences between groups or significant toxicities &gt; grade 2 were appreciated. LR increased from R1 to R6 in all groups (ΔEE= 24.80mm, p=0.14; ΔEE'=38.13mm, p=0.07; ΔE'E=8.05mm, p=0.38), the greatest increase approaching statistical significance in the EE' arm. The only arm with a statistically significant increase for in vivo DTH from R0-RC1-RC6 was in the EE' arm (ΔEE=-6.17mm, p=0.27; ΔEE'= 44.58mm, p&lt;0.05; ΔE'E=-1.42, p=0.37). Ex vivo analysis of IR revealed no significant difference between groups at R0(p=0.45) or RC6(p=0.72), nor within groups over time (EE p=0.32, EE' p=0.47, E'E p=0.30).

CONCLUSION In this phase Ib trial analyzing the IR of B Ca pts receiving a different vaccination strategy, both peptides were noted to be safe and immunogenic. While no difference was seen in E39-specific CD8+ T cells between groups, the in vivo response was enhanced with the use of E39' after E39; this may indicate expansion of more effective clonal populations of CD8+ T cells with this strategy. These results may be specific to B Ca pts who are relatively antigen-naïve with relatively intact immune systems. Further analysis of these pts as this trial continues will determine the optimal vaccination strategy capable of stimulating and maintaining an IR to prevent B Ca recurrence.

Citation Format: Jackson DO, Qiao N, Peace KM, Hale DF, Vreeland TJ, Greene JM, Berry JS, Trappey AF, Clifton GT, Ibrahim N, Toms A, Peoples GE, Mittendorf EA. Determining the optimal vaccination strategy using a combination of the folate binding protein (FBP) peptide vaccine (E39+GM-CSF) and an attenuated version (E39') to maximize the immunologic response in breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-10-04.