Immunotherapy of MSI Cancer: Facts and Hopes

Microsatellite instability (MSI) is a tumor molecular phenotype that evolves from loss of function in the mismatch repair (MMR) proteins through deleterious germline mutations, epigenetic inactivation, or somatic biallelic mutations. This phenotype is characterized by genomic hyper-mutability, increased neoantigen expression, and a favorable, immune-rich tumor microenvironment. These features confer a greater likelihood of response to treatment with the class of agents known as immune checkpoint inhibitors (ICI) and, potentially, other immune-based therapeutics. MSI as a predictive biomarker for response to treatment with ICIs ultimately led to the first tissue-agnostic approval of pembrolizumab for advanced, previously treated MSI or deficient MMR (dMMR) tumors. Nevertheless, response to ICIs in dMMR/MSI tumors is not universal. Identifying predictors of response and elucidating mechanisms of immune escape will be crucial to continued successful treatment of this subset. In this review, we aim to describe the pathogenesis and key immunologic features of dMMR/MSI tumors, provide a brief overview of the currently approved treatments, and discuss promising novel immune-based therapeutics currently under investigation.

Final results of urelumab, an anti-CD137 agonist monoclonal antibody, in combination with cetuximab or nivolumab in patients with advanced solid tumors

BACKGROUND

Resistance to immune checkpoint inhibitors and targeted treatments for cancer is common; thus, novel immunotherapy agents are needed. Urelumab is a monoclonal antibody agonist that binds to CD137 receptors expressed on T cells. Here, we report two studies that evaluated urelumab in combination with cetuximab or nivolumab in patients with select, advanced solid tumors.

METHODS

CA186-018: Patients with metastatic colorectal cancer or metastatic squamous cell carcinoma of the head and neck (SCCHN) were treated in a dose-evaluation phase with urelumab 0.1 mg/kg (urelumab-0.1) every 3 weeks (Q3W)+cetuximab 250 mg/m2 (cetuximab-250) weekly; and in a dose-expansion phase with urelumab 8 mg flat dose (urelumab-8) Q3W+cetuximab-250 weekly. CA186-107: The dose-escalation phase included patients with previously treated advanced solid tumors (or treated or treatment-naive melanoma); patients received urelumab 3 mg flat dose (urelumab-3) or urelumab-8 every 4 weeks+nivolumab 3 mg/kg (nivolumab-3) or 240 mg (nivolumab-240) every 2 weeks. In the expansion phase, patients with melanoma, non-small cell lung cancer, or SCCHN were treated with urelumab-8+nivolumab-240. Primary endpoints were safety and tolerability, and the secondary endpoint included efficacy assessments.

RESULTS

CA186-018: 66 patients received study treatment. The most frequent treatment-related adverse events (TRAEs) were fatigue (75%; n=3) with urelumab-0.1+cetuximab-250 and dermatitis (45%; n=28) with urelumab-8+cetuximab-250. Three patients (5%) discontinued due to TRAE(s) (with urelumab-8+cetuximab-250). One patient with SCCHN had a partial response (objective response rate (ORR) 5%, with urelumab-8+cetuximab-250).CA186-107: 134 patients received study treatment. Fatigue was the most common TRAE (32%; n=2 with urelumab-3+nivolumab-3; n=1 with urelumab-8+nivolumab-3; n=40 with urelumab-8+nivolumab-240). Nine patients (7%) discontinued due to TRAE(s) (n=1 with urelumab-3+nivolumab-3; n=8 with urelumab-8+nivolumab-240). Patients with melanoma naive to anti-PD-1 therapy exhibited the highest ORR (49%; n=21 with urelumab-8+nivolumab-240). Intratumoral gene expression in immune-related pathways (CD3, CD8, CXCL9, GZMB) increased on treatment with urelumab+nivolumab.

CONCLUSIONS

Although the addition of urelumab at these doses was tolerable, preliminary response rates did not indicate an evident additive benefit. Nevertheless, the positive pharmacodynamics effects observed with urelumab and the high response rate in treatment-naive patients with melanoma warrant further investigation of other anti-CD137 agonist agents for treatment of cancer.

TRIAL REGISTRATION NUMBERS

NCT02110082; NCT02253992.

Nivolumab monotherapy or combination with ipilimumab with or without cobimetinib in previously treated patients with pancreatic adenocarcinoma (CheckMate 032)

BACKGROUND

Pancreatic cancer is one of the deadliest cancer types and represents a major unmet medical need. CheckMate 032 investigated safety and efficacy of nivolumab monotherapy and nivolumab plus ipilimumab with/without cobimetinib in advanced/metastatic solid tumors, including pancreatic cancer.

METHODS

In the original pancreatic cancer cohort, previously treated patients (≥1 prior regimen) with advanced/metastatic pancreatic adenocarcinoma were assigned to nivolumab 3 mg/kg every 2 weeks (monotherapy arm) or nivolumab 1 mg/kg and ipilimumab 1 mg/kg or 3 mg/kg every 3 weeks for four doses, followed by nivolumab 3 mg/kg every 2 weeks (combination arm). A subsequent modified pancreatic cohort (one or two prior regimens) received nivolumab 3 mg/kg every 2 weeks, ipilimumab 1 mg/kg every 6 weeks, and cobimetinib 60 mg orally once daily for 21 days on and 7 days off (triplet arm). The primary endpoint was investigator-assessed objective response rate (ORR). Secondary endpoints were investigator-assessed progression-free survival (PFS), PFS rate, overall survival (OS), OS rate, safety, and tolerability. Additionally, ORR, PFS, and duration of response were assessed by blinded independent central review (BICR) in the triplet arm.

RESULTS

18 patients received nivolumab monotherapy, 21 received nivolumab plus ipilimumab, and 30 received nivolumab plus ipilimumab plus cobimetinib. In the triplet arm, partial responses were observed in two patients per investigator (ORR 6.7% (95% CI 0.8% to 22.1%)) and in three patients per BICR (ORR 10% (95% CI 2.1% to 26.5%)); no responses were observed in the other arms. Median (95% CI) PFS per investigator was 1.4 (1.3 to 2.0), 1.4 (1.2 to 2.7), and 3.0 (1.5 to 4.1) months for the monotherapy, nivolumab plus ipilimumab, and triplet arms, respectively. Median (95% CI) OS was 5.1 (2.0 to 9.0) months, 4.0 (1.9 to 5.6) months, and 6.2 (3.9 to 11.4) months, respectively. Most treatment-related adverse events were grade 2 or less.

CONCLUSIONS

Nivolumab with or without ipilimumab did not elicit objective responses in previously treated patients with advanced pancreatic adenocarcinoma, although three confirmed partial responses and manageable safety were observed with cobimetinib-containing triplet therapy. The small sample size and differences in baseline disease-specific characteristics between arms limit interpretation of these results.

Gemcitabine, Docetaxel, Capecitabine, Cisplatin, Irinotecan as First-line Treatment for Metastatic Pancreatic Cancer

Purpose

Treatment of advanced pancreatic cancer with a single therapeutic at a maximal dose has been largely ineffective at increasing survival. Combination therapies are commonly studied but often limited by toxicity. We previously showed that low-dose multiagent therapy with gemcitabine, docetaxel (taxotere), capecitabine (xeloda), and cisplatin (GTX-C) was safe, well tolerated, and effective (NCT01459614). Here, we hypothesize that adding irinotecan to GTX-C may improve survival with minimal toxicity.

Experimental Design

Patients with treatment-naïve metastatic pancreatic adenocarcinoma were treated with gemcitabine, docetaxel (taxotere), capecitabine (xeloda), cisplatin, and irinotecan (GTX-CI). Treatment consisted of capecitabine 500 mg twice daily on days 1-14 and gemcitabine 300 to 500 mg/m2, docetaxel 20 mg/m2, cisplatin 15 to 20 mg/m2, and irinotecan 20 to 60 mg/m2 on days 4 and 11 of a 21-day cycle. The primary objective was 9-month overall survival (OS). Secondary objectives included response rate (RR), disease control rate (DCR), progression-free survival (PFS), and OS.

Results

The regimen was well tolerated. The recommended phase II dose was gemcitabine 500 mg/m2, docetaxel 20 mg/m2, capecitabine 500 mg po bid, cisplatin 20 mg/m2, and irinotecan 20 mg/m2. Median follow-up in phase II was 11.02 months (2.37-45.17). Nine-month OS rate was 57% [95% confidence interval (CI): (41-77)]. RR was 57% [95% CI: (37-75) 50% PR and 7% CR]. DCR was 87% [95% CI: (69-96)]. Median OS and PFS were 11.02 [95% CI: (8.54-21.09)] and 8.34 [95% CI: (6.34-NA)] months, respectively.

Conclusions

The addition of irinotecan to GTX-C was safe and well tolerated. While the study did not meet its primary objective, the responses were clinically meaningful using a well-tolerated regimen.

Significance

We aimed to optimize the previously reported efficacious regimen of low-dose multiagent therapy with GTX-C for the treatment of metastatic pancreatic ductal adenocarcinoma by adding irinotecan. The primary objective was not met, but GTX-CI was well tolerated. The RR of 57%, median PFS of 8.3 months, median OS of 11 months, and 36-month OS rate of 19% suggest clinical benefit. Further optimization of this regimen is warranted.

A platform trial of neoadjuvant and adjuvant antitumor vaccination alone or in combination with PD-1 antagonist and CD137 agonist antibodies in patients with resectable pancreatic adenocarcinoma

A neoadjuvant immunotherapy platform clinical trial allows for rapid evaluation of treatment-related changes in tumors and identifying targets to optimize treatment responses. We enrolled patients with resectable pancreatic adenocarcinoma into such a platform trial (NCT02451982) to receive pancreatic cancer GVAX vaccine with low-dose cyclophosphamide alone (Arm A; n = 16), with anti-PD-1 antibody nivolumab (Arm B; n = 14), and with both nivolumab and anti-CD137 agonist antibody urelumab (Arm C; n = 10), respectively. The primary endpoint for Arms A/B - treatment-related change in IL17A expression in vaccine-induced lymphoid aggregates - was previously published. Here, we report the primary endpoint for Arms B/C: treatment-related change in intratumoral CD8+ CD137+ cells and the secondary outcomes including safety, disease-free and overall survivals for all Arms. Treatment with GVAX+nivolumab+urelumab meets the primary endpoint by significantly increasing intratumoral CD8+ CD137+ cells (p = 0.003) compared to GVAX+Nivolumab. All treatments are well-tolerated. Median disease-free and overall survivals, respectively, are 13.90/14.98/33.51 and 23.59/27.01/35.55 months for Arms A/B/C. GVAX+nivolumab+urelumab demonstrates numerically-improved disease-free survival (HR = 0.55, p = 0.242; HR = 0.51, p = 0.173) and overall survival (HR = 0.59, p = 0.377; HR = 0.53, p = 0.279) compared to GVAX and GVAX+nivolumab, respectively, although not statistically significant due to small sample size. Therefore, neoadjuvant and adjuvant GVAX with PD-1 blockade and CD137 agonist antibody therapy is safe, increases intratumoral activated, cytotoxic T cells, and demonstrates a potentially promising efficacy signal in resectable pancreatic adenocarcinoma that warrants further study.

Colorectal cancer in patients of advanced age is associated with increased incidence of BRAF p.V600E mutation and mismatch repair deficiency

Introduction

The highest incidence of colorectal cancer (CRC) is in patients diagnosed at 80 years or older highlighting a need for understanding the clinical and molecular features of these tumors. Methods. In this retrospective cohort study, 544 CRCs underwent next generation sequencing and mismatch repair (MMR) evaluation. Molecular and clinical features were compared between 251 patients with traditional-onset CRC (50-69 years at diagnosis) and 60 with late-onset CRC (>80 years at diagnosis).

Results

Late-onset CRC showed a significantly higher rate of right-sided tumors (82% vs 35%), MMR deficiency (35% vs. 8%) and BRAF p.V600E mutations (35% vs. 8%) and a significantly lower rate of stage IV disease (15% vs 28%) and APC mutations (52% vs. 78%). Association of these features with advanced age was supported by stratifying patients into 6 age groups (<40, 40-49, 50-59, 60-69, 70-79 and >80 years). However, the age-related rise in MMR deficient (dMMR) CRC was only seen in the female patients with an incidence of 48% (vs. 10% in the male patient) in the >80y group. In addition, BRAF p.V600E was significantly enriched in MMR deficient CRC of advanced age (67% in late-onset CRC). Categorizing CRC by mutational profiling, late-onset CRC revealed a significantly higher rate of dMMR/BRAF ⁺ APC ^- (18% vs. 2.0%), dMMR/BRAF ^- APC ^- (8.3% vs. 1.2%) and MMR proficient (pMMR)/BRAF ⁺ APC ^- (12% vs. 4.0%) as compared to traditional-onset CRC.

Discussion

In summary, there was a higher rate of dMMR and BRAF p.V600E in late-onset CRC, independently or in combination. The higher incidence of dMMR in late-onset CRC in females is most likely predominantly driven by BRAF p.V600E induced hypermethylation. Prospective studies with treatment plans designed specifically for these older patients are warranted to improve their outcomes.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of gastrointestinal cancer

Gastrointestinal (GI) cancers, including esophageal, gastroesophageal junction, gastric, duodenal and distal small bowel, biliary tract, pancreatic, colon, rectal, and anal cancer, comprise a heterogeneous group of malignancies that impose a significant global burden. Immunotherapy has transformed the treatment landscape for several GI cancers, offering some patients durable responses and prolonged survival. Specifically, immune checkpoint inhibitors (ICIs) directed against programmed cell death protein 1 (PD-1), either as monotherapies or in combination regimens, have gained tissue site-specific regulatory approvals for the treatment of metastatic disease and in the resectable setting. Indications for ICIs in GI cancer, however, have differing biomarker and histology requirements depending on the anatomic site of origin. Furthermore, ICIs are associated with unique toxicity profiles compared with other systemic treatments that have long been the mainstay for GI cancer, such as chemotherapy. With the goal of improving patient care by providing guidance to the oncology community, the Society for Immunotherapy of Cancer (SITC) convened a panel of experts to develop this clinical practice guideline on immunotherapy for the treatment of GI cancer. Drawing from published data and clinical experience, the expert panel developed evidence- and consensus-based recommendations for healthcare professionals using ICIs to treat GI cancers, with topics including biomarker testing, therapy selection, and patient education and quality of life considerations, among others.

Converging on a Cure: The Roads to Predictive Immunotherapy

SUMMARY

Convergence science teams integrating clinical, biological, engineering, and computational expertise are inventing new forecast systems to monitor and predict evolutionary changes in tumor and immune interactions during early cancer progression and therapeutic response. The resulting methods should inform a new predictive medicine paradigm to select adaptive immunotherapeutic regimens personalized to patients' tumors at a given time during their cancer progression for durable patient response.

Abstract 2270: Combination of CXCR4 antagonist and anti-PD1 therapy results in significant mobilization and increased infiltration of myeloid cells into the metastatic liver microenvironment of PDAC

Pancreatic adenocarcinoma (PDAC) is extremely lethal and resistant to checkpoint immunotherapy, characterized by an immunosuppressive tumor microenvironment consisting of stromal and myeloid cells. Prior studies have demonstrated the utility of targeting the chemokine signaling axis CXCR4-CXCL12 (SDF-1), a highlighted feature in PDACs, to overcome the CXCL12-driven immobilization of T cells and thus facilitate their antitumor role within the tumor. Based on these findings, we have conducted a phase 2 trial evaluating the effects of plerixafor, a CXCR4 antagonist, and cemiplimab, a PD1 inhibitor antibody, in patients with metastatic PDAC who have progressed after one line of systemic chemotherapy (NCT04177810). To determine the immunological responses to therapy, blood samples and tissue biopsies were obtained at baseline and during treatment. Hematological assessment confirmed the activity of CXCR4 antagonist in mobilizing hematopoietic precursors (CD34+), immature myeloid cells, and lymphoid cells, as well as monocytic and granulocytic cell populations. Suspension mass cytometry analysis of peripheral blood mononuclear cells revealed that mobilized monocytic subpopulations had high expressions of chemokine receptors CCR2, CCR5, and CXCR2. Histopathologic evaluation of the serial tissue biopsies from the liver metastatic PDAC revealed increased levels of inflammation upon treatment. To further characterize the cellular constituents of the observed inflammation, multiplexed immunohistochemistry by imaging mass cytometry was performed, demonstrating strong trends toward increased infiltration of not only effector T cells but also macrophages and granulocytic cells into the tumor microenvironment. Taken together, these findings suggest that mobilization of myeloid cells by CXCR4 antagonism results in the recruitment of additional myeloid cells from circulation and that alternative chemokine signaling pathways are sufficient for doing so. This implicates a potential mode of resistance against CXCR4-targeted therapies. Furthermore, these observations reinforce the value of ongoing research efforts in the field to subvert the recruitment or immunosuppressive function of myeloid cells, which would be particularly relevant in the setting of CXCR4 antagonism.

Citation Format: Sarah M. Shin, Alexei Hernandez, Erin Coyne, Zhehao Zhang, Sarah Mitchell, Jennifer Durham, Xuan Yuan, Hongqui Yang, Elana J. Fertig, Elizabeth M. Jaffee, Katherine M. Bever, Dung T. Le, Won Jin Ho. Combination of CXCR4 antagonist and anti-PD1 therapy results in significant mobilization and increased infiltration of myeloid cells into the metastatic liver microenvironment of PDAC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2270.

Pembrolizumab in Asian patients with microsatellite-instability-high/mismatch-repair-deficient colorectal cancer

The phase 3 KEYNOTE-177 study evaluated pembrolizumab versus chemotherapy with or without bevacizumab or cetuximab in patients with newly diagnosed, microsatellite-instability-high (MSI-H)/mismatch-repair-deficient (dMMR) metastatic colorectal cancer (mCRC). Primary endpoints were progression-free survival (PFS) per RECIST v1.1 by blinded independent central review (BICR) and overall survival (OS). Secondary endpoints were overall response rate (ORR) per RECIST v1.1 by BICR and safety. Here, we report results from the post hoc analysis of patients who were enrolled in Asia from the final analysis (FA) of KEYNOTE-177. A total of 48 patients from Japan, Korea, Singapore, and Taiwan (pembrolizumab, n = 22; chemotherapy, n = 26) were included. At FA, median time from randomization to data cutoff (February 19, 2021) was 45.3 (range 38.1-57.8) months with pembrolizumab and 43.9 (range 36.6-55.1) months with chemotherapy. Median PFS was not reached (NR; 95% confidence interval [CI] 1.9 months-NR) with pembrolizumab versus 10.4 (95% CI 6.3-22.0) months with chemotherapy (hazard ratio [HR] 0.56, 95% CI 0.26-1.20). Median OS was NR (range 13.8 months-NR) versus 30.0 (14.7-NR) months (HR 0.65, 95% CI 0.27-1.55) and ORR was 50% (95% CI 28-72) versus 46% (95% CI 27-67). Grade 3/4 treatment-related adverse events (TRAEs) were reported by two patients (9%) in the pembrolizumab arm and 20 (80%) in the chemotherapy arm. Immune-mediated adverse events or infusion reactions were reported by six patients (27%) and 10 patients (40%), respectively. No deaths due to TRAEs occurred. These data support first-line pembrolizumab as a standard of care for patients from Asia with MSI-H/dMMR mCRC. ClinicalTrials.gov identifier: NCT02563002.

Nivolumab and a CCR2/CCR5 dual antagonist (BMS-813160) with or without GVAX for locally advanced pancreatic ductal adenocarcinomas: Results of phase I study

730

Background: Surgical resection is the only potentially curative treatment for pancreatic adenocarcinoma (PDAC) but involvement of adjacent vital structures in locally advanced pancreatic adenocarcinoma (LAPC) precludes upfront resection. Neoadjuvant chemotherapy and/or radiation allows some LAPC patients to undergo resection but outcomes remain dismal. In this trial, we investigate the benefit of combining chemotherapy, radiation, and immunotherapy to improve outcomes in LAPC by enhancing antitumor immunity. The use of GVAX, Nivolumab, and BMS-813160 is hypothesized to promote immune responses through enhanced effector T cell infiltration and activation by GVAX and nivolumab while inhibiting immunosuppressive tumor associated macrophages via CCR2/5 inhibition with BMS-813160. Testing this combination in LAPC will facilitate assessment of the changes this combination produces in the tumor microenvironment. Methods: This open-label, single center two-arm phase I/II trial uses neoadjuvant/adjuvant nivolumab and BMS-813160 +/- GVAX following 8 to 16 doses of FOLFIRINOX and SBRT in patients with newly diagnosed LAPC. The primary endpoint of the phase I portion is safety of nivolumab, BMS-813160, and GVAX in patients with LAPC following chemotherapy and SBRT. The phase II portion randomizes patients 1:1 to nivolumab and BMS-813160 +/- GVAX with primary endpoint of immune response defined as > 80% increase in CD8+CD137+ cell infiltration. For the phase I portion a 3+3 dose escalation was used: nivolumab 480mg IV and GVAX 5x108 cells intradermal were administered at a fixed dose every 4 weeks. BMS-813160 was administered at a dose of 150mg and 300mg PO BID in levels 1 and 2 respectively. DLTs were evaluated during the 1st cycle of treatment and study-related adverse events (AE) were graded according to NCI CTCAE v5.0. Results: In the phase I portion of this trial, 13 patients were enrolled. The patient characteristics of the enrolled patients were: median age (range), 67 (44, 78), Female/Male, (4/9), Race, (Asian: 2, Black: 3, White: 8), histological grade (moderately/poor/moderately poor), (10/2/1). Nine of the 13 patients proceeded to immunotherapy after neoadjuvant chemotherapy and radiation. Three patients received treatment at dose level 1 and 6 patients at dose level 2. No DLTs were observed with the only grade 3 or higher AE being maculo-papular rash (n = 1). The RP2D for BMS-813160 was determined to be 300mg PO BID. Conclusions: We determined that nivolumab 480mg IV q4 weeks, GVAX 5x108 cells intradermal q4 weeks, and BMS-813160 300mg PO BID were the RP2D for the phase 2 portion of this investigation which is ongoing. This combination appears safe and neoadjuvant use does not lead to delay in surgery. Clinical trial information: NCT03767582 .

Pembrolizumab for previously treated, microsatellite instability–high/mismatch repair–deficient advanced colorectal cancer: final analysis of KEYNOTE-164

BACKGROUND

Pembrolizumab demonstrated durable clinical benefit and manageable safety in previously treated advanced or metastatic microsatellite instability-high (MSI-H)/mismatch repair deficient (dMMR) colorectal cancer (CRC) in the phase 2 KEYNOTE-164 study. Results from the final analysis are presented.

METHODS

Eligible patients had unresectable or metastatic MSI-H/dMMR CRC and ≥2 prior systemic therapies (cohort A) or ≥1 prior systemic therapy (cohort B). Patients received pembrolizumab 200 mg intravenously every 3 weeks for ≤35 cycles. The primary end-point was objective response rate (ORR) assessed per Response Evaluation Criteria in Solid Tumors, version 1.1 by blinded independent central review. Secondary end-points included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety and tolerability.

RESULTS

Sixty-one patients in cohort A and 63 patients in cohort B were enroled; median follow-up was 62.2 months and 54.4 months, respectively. ORR was 32.8% (95% CI, 21.3%-46.0%) in cohort A and 34.9% (95% CI, 23.3%-48.0%) in cohort B. Median DOR was not reached (NR) in either cohort. Median PFS was 2.3 months (95% CI, 2.1-8.1) in cohort A and 4.1 months (95% CI, 2.1-18.9) in cohort B. Median OS was 31.4 months (95% CI, 21.4-58.0) in cohort A and 47.0 months (95% CI, 19.2-NR) in cohort B. No new safety signals were observed. Nine patients who initially responded experienced disease progression off therapy and received second-course pembrolizumab. Six patients (66.7%) completed an additional 17 cycles of pembrolizumab, and 2 patients achieved a partial response.

CONCLUSIONS

Pembrolizumab continued to show durable antitumor activity, prolonged OS, and manageable safety in patients with previously treated MSI-H/dMMR CRC.

CLINICAL TRIAL REGISTRY INFORMATION

ClinicalTrials.gov, NCT02460198.

Solid Organ Transplantation Is Associated with an Increased Rate of Mismatch Repair Deficiency and PIK3CA Mutations in Colorectal Cancer

Solid organ transplants are associated with a modestly increased risk of colorectal cancers (CRC). However, the molecular profile of these cancers has not been described. We hypothesized that transplant-related immunosuppression may promote development of more immunogenic tumors as suggested by a high tumor mutation burden or mismatch repair deficiency. We performed an electronic medical record search for patients seen in the Johns Hopkins University Health System (JHHS) between 2017 and 2022 who developed CRC following solid organ transplantation. A comparator cohort of patients treated for CRC at JHHS with molecular profiling data was also identified. In this case, 29 patients were identified that developed post-transplant CRC (renal transplant, n = 18; liver transplant, n = 8; kidney-liver transplantation, n = 3). Compared to the JHHS general population CRC cohort, patients who developed post-transplant CRC had a higher rate of mismatch repair deficiency (41% versus 12%, p-value = 0.0038), and elevated tumor mutation burden (median of 22 mut/Mb versus 3.5 mut/Mb, p-value = 0.033) (range 3.52-53.65). Post-transplant tumors were enriched for PIK3CA mutations (43% versus 24%, p-value = 0.042). Post-Transplant CRCs are associated with clinical and molecular features of immune sensitivity, supporting a potential role for impaired immune surveillance in shaping the landscape of CRCs. These results may help inform the management of patients with post-transplant CRC.

Cell-free DNA Predicts Prolonged Response to Multi-agent Chemotherapy in Pancreatic Ductal Adenocarcinoma

The treatment of metastatic pancreatic ductal adenocarcinoma (PDAC) is frequently characterized by significant toxicity and rapid development of resistance to current approved therapies. More reliable biomarkers of response are needed to guide clinical decision making. We evaluated cell-free DNA (cfDNA) using a tumor-agnostic platform and traditional biomarkers (CEA and CA19-9) levels in 12 patients treated at Johns Hopkins University on NCT02324543 "Study of Gemcitabine/Nab-Paclitaxel/Xeloda (GAX) in Combination With Cisplatin and Irinotecan in Subjects With Metastatic Pancreatic Cancer." The pretreatment values, levels after 2 months of treatment, and change in biomarker levels with treatment were compared with clinical outcomes to determine their predictive value. The variant allele frequency (VAF) of KRAS and TP53 mutations in cfDNA after 2 months of treatment was predictive of progression-free survival (PFS) and overall survival (OS). In particular, patients with a lower-than-average KRAS VAF after 2 months of treatment had a substantially longer PFS than patients with higher posttreatment KRAS VAF (20.96 vs. 4.39 months). Changes in CEA and CA19-9 after 2 months of treatment were also good predictors of PFS. Comparison via concordance index demonstrated KRAS or TP53 VAF after 2 months of treatment to be better predictors of PFS and OS than CA19-9 or CEA. This pilot study requires validation but suggests cfDNA measurement is a useful adjunct to traditional protein biomarkers and imaging evaluation and could distinguish between patients who are likely to achieve prolonged responses versus those that will have early progression and may benefit from a change in treatment approach.

Significance

We report on the association of cfDNA with response durability for patients undergoing treatment with a novel metronomic chemotherapy regimen (gemcitabine, nab-paclitaxel, capecitabine, cisplatin, irinotecan; GAX-CI) for metastatic PDAC. This investigation offers encouraging evidence that cfDNA may prove to be a valuable diagnostic tool to guide clinical management.

Multiagent Chemotherapy and Stereotactic Body Radiation Therapy in Patients with Unresectable Pancreatic Adenocarcinoma: A Prospective Nonrandomized Controlled Trial

PURPOSE

In a prospective multicenter study, gemcitabine monotherapy followed by stereotactic body radiation therapy (SBRT) was well tolerated with outcomes comparable to chemoradiation for locally advanced pancreatic cancer (LAPC). Recent trials have reported improved survival with multiagent chemotherapy (MA-CTX) alone. This prospective trial explored whether SBRT could be safely delivered after MA-CTX. Herein, we report the long-term outcomes of adding SBRT after MA-CTX in LAPC patients and evaluate whether genetic profiles of specimens obtained before SBRT influence outcomes.

METHODS AND MATERIALS

This prospective nonrandomized controlled phase 2 trial enrolled 44 LAPC and 4 locally recurrent patients after multidisciplinary evaluation between 2012 and 2015 at a high-volume pancreatic cancer center. For induction CTX, most received modified FOLFIRINOX (mFFX), or gemcitabine and nab-paclitaxel (GnP) followed by 5-fraction SBRT for all. During fiducial placement, biopsies were obtained with DNA extracted for targeted sequencing using the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets platform.

RESULTS

Median induction CTX duration was ≥4 months, and 31 patients received mFFX (65%). Among 44 LAPC patients, 17 (39%) were surgically explored, and 12 of 16 (75%) achieved a R0 resection. Median overall survival (mOS) was 20.2 and 14.6 months from diagnosis and SBRT, respectively. One- and 2-year OS from SBRT was 58% and 28%. The mOS after resection was 28.6 and 22.4 months from diagnosis and SBRT, respectively. Median local progression-free survival was 23.9 and 15.8 months from diagnosis and SBRT, respectively. The mOS for pre-SBRT CA 19-9 ≤180 U/mL versus >180 was 23.1 and 11.3 months, respectively (hazard ratio, 0.53; P = .04). Only 1 patient (2.1%) had late grade ≥2 gastrointestinal toxic effects attributable to SBRT. Despite significant pretreatment with chemotherapy, 88% of tumor specimens were effectively sequenced; survival outcomes were not significantly associated with specific mutational patterns. Quality of life was prospectively collected pre- and post-SBRT with the EORTC QLQ-C30 and PAN26 questionnaires showing no significant change.

CONCLUSIONS

SBRT was safely administered with MA-CTX with minimal toxicity. A high proportion of LAPC patients underwent R0 resection with favorable survival outcomes.

Adenoviral-based vaccine promotes neoantigen-specific CD8+ T cell stemness and tumor rejection

Upon chronic antigen exposure, CD8⁺ T cells become exhausted, acquiring a dysfunctional state correlated with the inability to control infection or tumor progression. In contrast, stem-like CD8⁺ T progenitors maintain the ability to promote and sustain effective immunity. Adenovirus (Ad)-vectored vaccines encoding tumor neoantigens have been shown to eradicate large tumors when combined with anti-programmed cell death protein 1 (αPD-1) in murine models; however, the mechanisms and translational potential have not yet been elucidated. Here, we show that gorilla Ad vaccine targeting tumor neoepitopes enhances responses to αPD-1 therapy by improving immunogenicity and antitumor efficacy. Single-cell RNA sequencing demonstrated that the combination of Ad vaccine and αPD-1 increased the number of murine polyfunctional neoantigen-specific CD8⁺ T cells over αPD-1 monotherapy, with an accumulation of Tcf1⁺ stem-like progenitors in draining lymph nodes and effector CD8⁺ T cells in tumors. Combined T cell receptor (TCR) sequencing analysis highlighted a broader spectrum of neoantigen-specific CD8⁺ T cells upon vaccination compared to αPD-1 monotherapy. The translational relevance of these data is supported by results obtained in the first 12 patients with metastatic deficient mismatch repair (dMMR) tumors vaccinated with an Ad vaccine encoding shared neoantigens. Expansion and diversification of TCRs were observed in post-treatment biopsies of patients with clinical response, as well as an increase in tumor-infiltrating T cells with an effector memory signature. These findings indicate a promising mechanism to overcome resistance to PD-1 blockade by promoting immunogenicity and broadening the spectrum and magnitude of neoantigen-specific T cells infiltrating tumors.

Abstract CT246: Phase 1b/2 study of giloralimab in combination with modified FOLFIRINOX with or without budigalimab in patients with untreated metastatic pancreatic cancer

Background: The 5-year survival rate for metastatic pancreatic cancer is ~3%, indicating an urgent need for novel therapies. Combination therapy with modified FOLFIRINOX (leucovorin, irinotecan, 5-fluorouracil, and oxaliplatin) and immunotherapy has been proposed for first-line metastatic pancreatic cancer to improve tolerability and clinical efficacy, respectively (NCCN, Pancreatic. 2021; Vonderheide, Annu. Rev. Med. 2020). The present study evaluates the safety, pharmacokinetics, and preliminary antitumor activity of modified FOLFIRINOX + giloralimab (CD40 agonist) with or without budigalimab (anti-PD-1) in patients with untreated metastatic pancreatic cancer.

Methods: Multicenter, randomized phase 1b/2 study (NCT04807972) in patients (18-75 years) with untreated metastatic pancreatic cancer. The phase 1b (dose escalation) examines the safety dose level of giloralimab in a triplet of modified FOLFIRINOX + giloralimab + budigalimab using a Bayesian optimal interval [BOIN] design. BOIN design is utilized to guide giloralimab escalation decisions. In phase 2 (dose expansion), patients are randomized 1:1:1 to receive treatment with modified FOLFIRINOX (cohort A), modified FOLFIRINOX + giloralimab (cohort B), or modified FOLFIRINOX + giloralimab + budigalimab (cohort C). Randomization is stratified according to Eastern Cooperative Oncology Group performance status. Primary objectives are to assess the safety and tolerability of modified FOLFIRINOX + giloralimab + budigalimab (phase 1b) and to evaluate overall survival in patients treated with modified FOLFIRINOX + giloralimab with or without budigalimab (versus those receiving modified FOLFIRINOX alone; phase 2). Secondary objectives include characterizing the pharmacokinetics of giloralimab and budigalimab in combination with modified FOLFIRINOX, assessing the efficacy of modified FOLFIRINOX + giloralimab with or without budigalimab, and evaluating the safety/tolerability of modified FOLFIRINOX + giloralimab with or without budigalimab. Patients will receive giloralimab and budigalimab intravenously in combination with modified FOLFIRINOX in a 28-day cycle. Dose-limiting toxicities are assessed during the first cycle of dosing. Adverse events are evaluated according to the National Cancer Institute Common Terminology Criteria for Adverse Events. Blood samples for pharmacokinetic analysis are collected at designated time points throughout the study. Responses are assessed by Response Evaluation Criteria in Solid Tumors version 1.1. Survival outcomes are described using the Kaplan-Meier method. Approximately 129 patients are planned to be included. Enrollment started in June 2021, with 7 patients enrolled as of November 2021.

Citation Format: Dung T. Le, Marcia Cruz-Correa, David L. Bajor, Rocio Garcia-Carbonero, Marion Harris, Roberto Pazo-Cid, Hedy Kindler, Nelson Yee, Suneel Kamath, Maulik Patel, Hua Fang, William Henner, Patrick Hardesty, Martha Blaney, Michael McDevitt, Talia Golan. Phase 1b/2 study of giloralimab in combination with modified FOLFIRINOX with or without budigalimab in patients with untreated metastatic pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT246.

RAD51B Harbors Germline Mutations Associated With Pancreatic Ductal Adenocarcinoma

PURPOSE

Genetic alterations in many components of the homologous recombination, DNA damage response, and repair (HR-DDR) pathway are involved in the hereditary cancer syndromes, including familial pancreatic cancer. HR-DDR genes beyond BRCA1, BRCA2, ATM, and PALB2 may also mutate and confer the HR-DDR deficiency in pancreatic ductal adenocarcinoma (PDAC).

METHODS

We conducted a study to examine the genetic alterations using a companion diagnostic 15-gene HR-DDR panel in PDACs. HR-DDR gene mutations were identified and characterized by whole-exome sequencing and whole-genome sequencing. Different HR-DDR gene mutations are associated with variable homologous recombination deficiency (HRD) scores.

RESULTS

Eight of 50 PDACs with at least one HR-DDR gene mutation were identified. One tumor with BRCA2 mutations is associated with a high HRD score. However, another tumor with a CHEK2 mutation is associated with a zero HRD score. Notably, four of eight PDACs in this study harbor a RAD51B gene mutation. All four RAD51B gene mutations were germline mutations. However, currently, RAD51B is not the gene panel for germline tests.

CONCLUSION

The finding in this study thus supports including RAD51B in the germline test of HR-DDR pathway genes.

First clinical and immunogenicity results including all subjects enrolled in a phase I study of Nous-209, an off-the-shelf immunotherapy, with pembrolizumab, for the treatment of tumors with a deficiency in mismatch repair/microsatellite instability (dMMR/MSI)

2515

Background: Defective DNA mismatch repair (dMMR) leads to high levels of microsatellite-instability (MSI-H) and insertions or deletions in coding regions, triggering the generation of tumor-specific frameshift peptides (FSPs). We selected 209 shared FSPs among subjects with dMMR/MSI-H cancers, to generate an off-the-shelf vaccine for the treatment of dMMR/MSI-H tumors. Those FSPs were cloned into four proprietary Great Apes Adenoviral (GAd) and four Modified Vaccinia Ankara (MVA) vectors to create a polyvalent viral vectored vaccine named Nous-209 [Leoni, G. et al. Cancer Res, 2020. 80(18): p. 3972-3982.]. Methods: This phase 1 first in human (FIH) study ( NCT04041310 ) evaluates safety and tolerability of two dose levels of the Nous-209 in combination with pembrolizumab, assesses immunogenicity and detects preliminary evidence of anti-tumor activity. Nous-209 is administered intramuscularly, concomitantly with pembrolizumab: one prime (GAd-209-FSP) at the 2nd pembrolizumab infusion and three boosters (MVA-209-FSP) at subsequent infusions each 3 weeks apart. The study is composed of two sequential cohorts i.e. dose escalation and dose expansion. Results: All evaluable subjects with 1st- or 2nd-line metastatic dMMR/MSI-H colorectal (CRC), gastric or gastroesophageal junction (GEJ) cancers enrolled in this phase I (n = 20) were evaluated as of February 03, 2022. Three subjects enrolled in dose level (DL) 1 (2 CRC and 1 GEJ cancer) showed durable confirmed partial responses (PRs). In DL 2 (12 CRC and 5 gastric cancers), 7 subjects had PRs, 6 had stable disease (SD) and 4 had progressive disease (PD) as best response. Most progressors progressed at the 1st CT and none of the responders have progressed. The median follow-up for subjects in DL1 is 24.7 months (22.3-26.7), and 7.6 months (0.9-19.4) in DL 2. The median progression free survival (PFS) and median duration of response (DoR) have not been reached. No dose limiting toxicities (DLTs) were observed. Vaccine immunogenicity was demonstrated in periphery by ex-vivo interferon-gamma ELISpot in 67% of subjects in DL 1, and 82% of subjects with evaluable samples in DL 2. The intratumoral TCR repertoire on pre/post tumor biopsies was analyzed in 3 evaluable subjects with PR and in 1 with PD: expansion and diversification of T cells post treatment with Nous-209 was noted only for the former. Vaccine-reactive TCR clones infiltrating the tumor biopsy post treatment were found in the only subject evaluated to date, with a long-term response. Conclusions: The combination of the Nous-209 and pembrolizumab is safe and well tolerated, and shows signs of clinical efficacy. Nous-209 elicits a neoantigen-specific T cell response expanding within the tumor, possibly contributing to the clinical outcome. Clinical trial information: NCT04041310.

Pembrolizumab versus chemotherapy for microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer (KEYNOTE-177): final analysis of a randomised, open-label, phase 3 study

BACKGROUND

Pembrolizumab has shown improved progression-free survival versus chemotherapy in patients with newly diagnosed microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. However, the treatment's effect on overall survival in this cohort of patients was unknown. Here, we present the final overall survival analysis of the KEYNOTE-177 study.

METHODS

This randomised, open-label, phase 3 study was done in 193 academic medical centres and hospitals in 23 countries. We recruited patients aged at least 18 years, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. Patients were randomly assigned (1:1) in blocks of four using an interactive voice response system or integrated web response system to intravenous pembrolizumab 200 mg every 3 weeks or to the investigator's choice of intravenous mFOLFOX6 (oxaliplatin 85 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1-2) or intravenous FOLFIRI (irinotecan 180 mg/m2 on day 1, leucovorin 400 mg/m2 on day 1, and fluorouracil 400 mg/m2 bolus on day 1 followed by a continuous infusion of 1200 mg/m2 per day for 2 days on days 1-2), every 2 weeks with or without intravenous bevacizumab 5 mg/kg every 2 weeks or intravenous weekly cetuximab (first dose 400 mg/m2, then 250 mg/m2 for every subsequent dose). Patients receiving chemotherapy could cross over to pembrolizumab for up to 35 treatment cycles after progression. The co-primary endpoints were overall survival and progression-free survival in the intention-to-treat population. KEYNOTE-177 is registered at ClinicalTrials.gov, NCT02563002, and is no longer enrolling patients.

FINDINGS

Between Feb 11, 2016, and Feb 19, 2018, 852 patients were screened, of whom 307 (36%) were randomly assigned to pembrolizumab (n=153) or chemotherapy (n=154). 93 (60%) patients crossed over from chemotherapy to anti-PD-1 or anti-PD-L1 therapy (56 patients to on-study pembrolizumab and 37 patients to off-study therapy). At final analysis (median follow-up of 44·5 months [IQR 39·7-49·8]), median overall survival was not reached (NR; 95% CI 49·2-NR) with pembrolizumab vs 36·7 months (27·6-NR) with chemotherapy (hazard ratio [HR] 0·74; 95% CI 0·53-1·03; p=0·036). Superiority of pembrolizumab versus chemotherapy for overall survival was not demonstrated because the prespecified α of 0·025 needed for statistical significance was not achieved. At this updated analysis, median progression-free survival was 16·5 months (95% CI 5·4-38·1) with pembrolizumab versus 8·2 months (6·1-10·2) with chemotherapy (HR 0·59, 95% CI 0·45-0·79). Treatment-related adverse events of grade 3 or worse occurred in 33 (22%) of 153 patients in the pembrolizumab group versus 95 (66%) of 143 patients in the chemotherapy group. Common adverse events of grade 3 or worse that were attributed to pembrolizumab were increased alanine aminotransferase, colitis, diarrhoea, and fatigue in three (2%) patients each, and those attributed to chemotherapy were decreased neutrophil count (in 24 [17%] patients), neutropenia (22 [15%]), diarrhoea (14 [10%]), and fatigue (13 [9%]). Serious adverse events attributed to study treatment occurred in 25 (16%) patients in the pembrolizumab group and in 41 (29%) patients in the chemotherapy group. No deaths attributed to pembrolizumab occurred; one death due to intestinal perforation was attributed to chemotherapy.

INTERPRETATION

In this updated analysis, although pembrolizumab continued to show durable antitumour activity and fewer treatment-related adverse events compared with chemotherapy, there was no significant difference in overall survival between the two treatment groups. These findings support pembrolizumab as an efficacious first-line therapy in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer.

FUNDING

MSD.

Neoadjuvant Stereotactic Body Radiotherapy After Upfront Chemotherapy Improves Pathologic Outcomes Compared With Chemotherapy Alone for Patients With Borderline Resectable or Locally Advanced Pancreatic Adenocarcinoma Without Increasing Perioperative Toxicity

BACKGROUND

Patients with borderline resectable pancreatic cancer (BRPC) or locally advanced pancreatic cancer (LAPC) are at high risk of margin-positive resection. Neoadjuvant stereotactic body radiation therapy (SBRT) may help sterilize margins, but its additive benefit beyond neoadjuvant chemotherapy (nCT) is unclear. The authors report long-term outcomes for BRPC/LAPC patients explored after treatment with either nCT alone or nCT followed by five-fraction SBRT (nCT-SBRT).

METHODS

Patients with BRPC or LAPC from 2011 to 2016 who underwent resection after nCT alone or nCT-SBRT were retrospectively reviewed. Baseline characteristics were compared, and the propensity score with inverse probability weighting (IPW) was used to compare pathologic/survival outcomes.

RESULTS

Of 198 patients, 76 received nCT, and 122 received nCT-SBRT. The nCT-SBRT cohort had a higher proportion of LAPC (53% vs 22%; p < 0.001). The duration of nCT was longer for nCT-SBRT (4.6 vs 2.9 months; p = 0.03), but adjuvant chemotherapy was less frequently administered (53% vs 67.1%; p < 0.001). Adjuvant radiation was administered to 30% of the nCT patients. The nCT-SBRT regimen more frequently achieved negative margins (92% vs 70%; p < 0.001), negative nodes (59% vs 42%; p < 0.001), and pathologic complete response (7% vs 0%; p = 0.02). In the multivariate analysis, nCT-SBRT remained associated with R0 resection (p < 0.001). The nCT-SBRT cohort experienced no significant difference in median overall survival (OS) (22.1 vs 24.5 months), local progression-free survival (LPFS) (13.5 vs. 15.4 months), or distant metastasis-free survival (DMFS) (11.7 vs 16.3 months) after surgery. After SBRT, 1-year OS was 77.0% and 2-year OS was 50.4%. Perioperative Claven-Dindo grade 3 or greater morbidity did not differ significantly between the nCT and nCT-SBRT cohorts (p = 0.81).

CONCLUSIONS

Despite having more advanced disease, the nCT-SBRT cohort was still more likely to undergo an R0 resection and experienced similar survival outcomes compared with the nCT alone cohort.

Significant Vision Recovery from Filler-Induced Complete Blindness with Combined Intra-Arterial Injection of Hyaluronidase and Thrombolytic Agents

With the increase of cosmetic injectable hyaluronic acid (HA), there have been more cases with serious complications, including skin necrosis, blindness, and cerebral embolism. Patients who have recovered from HA filler-induced total vision loss are extremely rare. We report a case of a 27-year-old female who developed severe ocular pain on the right side and total vision loss following a 1.0 ml HA filler injection in the nasal dorsum. She arrived at our hospital 4 hours later. Her visual acuity was no light perception (NLP), and she exhibited eyelid ptosis, ophthalmoplegia, and frontal and nasal ecchymosis. She was promptly treated with subcutaneous and retrobulbar hyaluronidase injections, as well as intra-arterial 1500 IU hyaluronidase injections into the right ophthalmic artery with DSA assistance. Her vision improved from NLP to counting fingers at 1.0 meters. Unfortunately, 13 hours later, she felt an intense headache, and her vision again decreased to NLP. We immediately performed an injection of 1500 IU hyaluronidase combined with 8 mg alteplase for intra-arterial thrombolysis (IAT) into the right ophthalmic artery. Her vision improved immediately afterward. After 3 months, her visual acuity had significantly recovered from NLP (admission vision status) to 20/50 (Snellen chart with glasses). Similarly, skin, conjunctival, eye movement, and ptosis symptoms completely recovered. This case demonstrates that reversal of complete blindness due to embolism of the ophthalmic and central retinal arteries could be accomplished through multidisciplinary therapies, especially IAT using fibrinolytic agents combined with hyaluronidase followed by an anticoagulant regimen.Level of evidence VThis journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine Ratings, please refer to Table of Contents or online Instructions to Authors www.springer.com/00266 .

Neoadjuvant and adjuvant antitumor vaccination alone or combination with PD1 blockade and CD137 agonism in patients with resectable pancreatic adenocarcinoma

558

Background: Utilizing a vaccine that induces and activates host effector T cells and co-administering it with immune modulating agents that enhance anti-tumor T cell activity is a potential strategy for overcoming pancreatic adenocarcinoma’s (PDA) resistance to immunotherapy. Our prior clinical trial demonstrated a GM-CSF-secreting, allogeneic tumor cell vaccine (GVAX) increases infiltrating CD8+ T cells in PDA. Follow up preclinical work demonstrated therapeutic synergy between GVAX and PD-1inhibition (PD1) with efficacy further enhanced by CD137 agonism (CD137). Methods: This was a 3-arm trial of neoadjuvant & adjuvant GVAX-based therapy in resectable (r) PDA patients (pts). Adults with clinically resectable, untreated PDA were enrolled in 1 of 3 study treatments: Arm A (GVAX alone), Arm B (GVAX + PD1 [Nivolumab]), or arm C (GVAX + PD1 + CD137 [Urelumab]). Treatment was given as follows: Day 1 - Cyclophosphamide 200mg/m2 IV (All Arms), Nivolumab 480mg IV (Arms B, C), Urelumab 8mg IV (Arm C); Day 2 – GVAX ID (All Arms). Pts were treated at 3 timepoints: 1) once 2 weeks prior to surgery; 2) once post-surgical recovery prior to standard of care adjuvant chemotherapy (SOC); 3) every month (up to 4 mo) following completion of SOC (if disease-free). SOC regimes included (m)FOLFIRINOX, Gem +/- Cap/NAB-Paclitaxel. The study was powered for a primary biologic endpoint: treatment-related change in intratumoral CD8+CD137+ T cells. Clinical endpoints included disease-free survival (DFS: time from surgery to recurrence), overall survival (OS: time from surgery to death), and safety. Results: 38 pts (N = 15 [Arm A], N = 13 [Arm B], N = 10 [Arm C]) were eligible for efficacy analysis (had R0/R1 resection) and 45 pts (N = 17 [A], N = 17 [B], N = 11 [C]) were eligible for safety analysis (had ≥1 dose of study treatment). Demographics, surgical pathology features, and SOC durations were similar in all Arms. At median follow up of 23 mo [A], 26 mo [B], and 22 mo [C], median DFS (95% CI) was 14.82 mo (6.0, NA), 16.23 mo (7.49, NA) and not reached (16.33, NA) for Arms A, B, C, respectively. There was no DFS benefit to adding PD1 compared to GVAX alone (HR 0.98 [95% CI 0.42, 2.27], p = 0.96). Combination CD137 + PD1 + GVAX was associated with marginally significant improved DFS compared to GVAX alone (HR 0.38 [95%CI 0.12, 1.19], p = 0.097) and GVAX + PD1 (HR 0.38 [95%CI 0.12, 1.21], p = 0.103). Median OS (95% CI) was 25.0 mo (18.8, NA), 26.4 mo (20.3, NA), and not yet reached for Arms A, B, C, respectively. There were no serious adverse events. In Arm C, 1 pt had grade 3 rash that delayed treatment and there was 1 instance of grade 2 AST/ALT elevation. The biologic endpoint will be reported at the meeting. Conclusions: Despite a small sample size, combining GVAX with dual immune-targeting of PD-1 blockade and CD137 agonism was safe and may enhance DFS in rPDA pts treated in the perioperative and post-adjuvant settings. Clinical trial information: NCT02451982.

Tim-4+ cavity-resident macrophages impair anti-tumor CD8+ T cell immunity

Immune checkpoint blockade (ICB) has been a remarkable clinical advance for cancer; however, the majority of patients do not respond to ICB therapy. We show that metastatic disease in the pleural and peritoneal cavities is associated with poor clinical outcomes after ICB therapy. Cavity-resident macrophages express high levels of Tim-4, a receptor for phosphatidylserine (PS), and this is associated with reduced numbers of CD8+ T cells with tumor-reactive features in pleural effusions and peritoneal ascites from patients with cancer. We mechanistically demonstrate that viable and cytotoxic anti-tumor CD8+ T cells upregulate PS and this renders them susceptible to sequestration away from tumor targets and proliferation suppression by Tim-4+ macrophages. Tim-4 blockade abrogates this sequestration and proliferation suppression and enhances anti-tumor efficacy in models of anti-PD-1 therapy and adoptive T cell therapy in mice. Thus, Tim-4+ cavity-resident macrophages limit the efficacy of immunotherapies in these microenvironments.

Immunotherapy in colorectal cancer

The immune tumor microenvironment (TME) of colorectal cancer (CRC) is a crucial contributor to disease biology, making it an important target for therapeutic intervention. The diversity of immune cell populations within various subsets of CRC has led to the discovery that immune characterization of the TME has both prognostic and predictive value for patients. The convergence of improved molecular and cellular characterization of CRC along with the widespread use of immunotherapy in solid tumors has led to a revolution in the approach to clinical care. Monoclonal antibodies (mAbs) which target key immune checkpoints, such as programmed death-1 (PD-1) and cytotoxic T-lymphocyte antigen 4 (CTLA-4), have demonstrated remarkable clinical activity in microsatellite instability-high (MSI-H) CRCs and are now used in routine practice. The observation that MSI-H cancers are highly infiltrated with immune cells and carry a high neoantigen load led to the successful targeting of these cancers with immunotherapy. More recently, the Food and Drug Administration (FDA) approved a PD-1 inhibitor for microsatellite stable (MSS) cancers with high tumor mutation burden. However, the anti-tumor activity of immunotherapy is rare in the majority of CRC. While immune cell characterization does provide prognostic value in these patients, these observations have not yet led to therapeutic interventions. By delineating factors that predict efficacy, resistance, and therapeutic targets, ongoing research will inform the development of effective combination strategies for the vast majority of MSS CRC and immunotherapy-resistant MSI-H cancers.

Anti-PD-1 elicits regression of undifferentiated pleomorphic sarcomas with UV-mutation signatures

Undifferentiated pleomorphic sarcoma (UPS), an aggressive soft-tissue sarcoma of adults, has been characterized by low tumor mutational burden (TMB) and high copy number alterations. Clinical trials of programmed death-1 (PD-1) blockade in UPS have reported widely varying efficacy. We describe two patients with recurrent scalp UPS that experienced clinical benefit from PD-1 blockade. These tumors had high TMB with a UV-induced mutational pattern. Analysis of additional head and neck UPS cases identified five out of seven tumors with high TMB and an ultraviolet (UV) mutational signature. Head and neck UPS tumors also had increased programmed death-ligand 1 (PD-L1) expression and CD8+ T cell infiltration as compared with UPS tumors arising from other sites. In summary, we found that UPS tumors of the head and neck, but not elsewhere, have a PD-L1+, T-cell-inflamed tumor microenvironment and high TMB, suggesting that these tumors represent a distinct genetic subgroup of UPS for which immune checkpoint inhibitor therapy might be effective.

Final overall survival for the phase III KN177 study: Pembrolizumab versus chemotherapy in microsatellite instability-high/mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC)

3500

Background: In the phase III, randomized open-label KEYNOTE-177 (NCT02563002) study 1L pembrolizumab (pembro) versus chemotherapy (chemo) provided superior progression-free survival (PFS) at second interim analysis (IA2) in patients (pts) with MSI-H/dMMR mCRC. The study continued to final analysis of overall survival (OS), planned after 190 OS events or 12 months after IA2, whichever occurred first. We present results of the final analysis of OS, 12 months after IA2. Methods: A total of 307 pts with MSI-H/dMMR mCRC and ECOG PS 0 or 1 were randomized 1:1 to 1L pembro 200 mg Q3W for up to 2y or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab. Treatment continued until PD, unacceptable toxicity, pt/investigator decision to withdraw, or completion of 35 cycles (pembro only). Pts receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were OS and PFS (RECIST v1.1, central review). Secondary end points included ORR, duration of response (DOR) (RECIST v1.1, central review), and safety. For OS significance, the p-value had to meet a prespecified α of 0.0246 (one-sided). Sensitivity analyses to adjust for crossover effect were performed. Data cut-off for final analysis was Feb 19, 2021. Results: Median (range) study follow-up was 44.5 mo (36.0-60.3) with pembro vs 44.4 mo (36.2-58.6) with chemo. 56 (36%) pts crossed over from chemo to pembro, with 37 more receiving anti-PD-1/PD-L1 therapies off study (60% effective crossover rate in the ITT). The HR for OS favored pembro vs chemo with a trend toward reduction in the risk of death (HR 0.74; 95% CI, 0.53-1.03; P=0.0359; median not reached [NR] vs 36.7 mo); this difference did not reach statistical significance. Sensitivity analysis by the rank-preserving structure failure time model and inverse probability of censoring weighting showed OS HRs of 0.66 (95% CI 0.42-1.04) and 0.77 (95% CI 0.44-1.38), respectively. Pembro vs chemo met the prespecified criteria for PFS superiority at IA2. At final analysis, median PFS was 16.5 mo vs 8.2 mo (HR 0.59; 95% CI, 0.45-0.79), but was not formally tested per analysis plan. Confirmed ORR was 45.1% (20 CR, 49 PR) vs 33.1% (6 CR, 45 PR). Median (range) DOR was NR (2.3+ to 53.5+) vs 10.6 mo (2.8 to 48.3+), respectively. Treatment-related adverse events (TRAEs) occurred in 79.7% vs 98.6% of pts; 21.6% vs 66.4%, respectively, had grade ≥3 TRAEs. Conclusions: As 1L therapy for pts with MSI-H/dMMR mCRC, pembro vs chemo provides statistically superior PFS with fewer TRAEs, and is associated with a trend toward reduced mortality that did not meet statistical significance likely due to the high crossover rate from chemo to anti-PD1/PD-L1 therapies. Together these data confirm pembro as a new standard-of-care in the 1L for pts with MSI-H/dMMR mCRC. Clinical trial information: NCT02563002.

A phase 2 study of cyclophosphamide (CY), GVAX, pembrolizumab (Pembro), and stereotactic body radiation (SBRT) in patients (pts) with locally advanced pancreas cancer (LAPC)

4134

Background: Management of locally advanced pancreas cancer (LAPC) standardly involves chemotherapy with consolidative radiation and surgery in selected pts. Checkpoint inhibitors have shown limited benefit alone in pancreas cancer but may be primed by radiation and GM-CSF secreting allogeneic pancreatic cancer vaccine (GVAX). We present data from a phase 2 study for LAPC pts who have not developed metastases after standard of care chemotherapy treated with combination cyclophosphamide (CY), GVAX, pembrolizumab (pembro), and stereotactic body radiation therapy (SBRT). Methods: This is a single-arm, single institution, open-label study for pts with LAPC at diagnosis (as per NCCN guidelines, arterial involvement > 180°, or unreconstructible SMV/PV) who remained without metastatic disease after 4-8 28-day cycles FOLFIRINOX or gemcitabine/abraxane based therapy. Pts received CY (200mg/m2 IV) and pembro (200mg IV) on day 1, followed by GVAX (6 intradermal inj) on day 2 q3 wk x 2 cycles, with cycle 2 initiating concurrently with 5 days SBRT. Pts were restaged 4-6 weeks after SBRT, and if non-metastatic, pts underwent surgical resection, irreversible electroporation (IRE), or biopsy (if not undergoing surgical resection). Pts received two cycles of chemotherapy, and if metastasis free, received q3 wk CY/pembro/GVAX x 6 cycles with restaging scans q3 mos. In 5/2017, the protocol was addended to include an extended phase with q3 wk pembro x 9 cycles and q6 mo CY/GVAX x 4. Primary endpoint was distant metastasis free survival (DMFS) defined as C1D1 to distant metastases or death. Results: From Jul 2016-Jan 2021, 58 pts with LAPC were enrolled at the Johns Hopkins Hospital, 54 completed 2 cycles CY/pembro/GVAX and SBRT and were evaluable for response (2 dropouts due to thrombocytopenia, 2 due to irAE (DKA and hepatitis)), median followup was 15.8 mos. Demographics: median age 66 (range 42-84), 53% male, 84% White, 12% African American. At first restaging (N = 54), 8 (15%) had metastatic disease, 9 (17%) were unresectable, 37 (69%) were eligible for surgical resection. 35 pts proceeded to the OR (1 died of cholangitis prior to surgery and 1 declined surgery), 24 had tumors resected (44% of evaluable pts, 10 (42%) had grade 1 (marked) pathologic response), 1 IRE, 2 were unresectable, 8 were metastatic. Common related AEs were vaccine site reactions; grade 3 irAE included 1 case each of dermatitis, colitis, DKA, nephritis, and pneumonitis. DMFS was 9.7 mos [95% CI 6.3-19.3 mos]. Conclusions: We present data from a ph II study of 54 pts w LAPC treated w CY/GVAX/pembro and SBRT. Primary endpoint of DMFS > 13.6 mos not reached, however 44% of pts underwent surgical resection of whom 42% had grade 1 path response rate. Additional correlative studies are underway. Clinical trial information: NCT02648282.

Health-related quality of life in patients with microsatellite instability-high or mismatch repair deficient metastatic colorectal cancer treated with first-line pembrolizumab versus chemotherapy (KEYNOTE-177): an open-label, randomised, phase 3 trial

BACKGROUND

In the KEYNOTE-177 study, pembrolizumab monotherapy provided statistically significant and clinically meaningful improvements in progression-free survival versus chemotherapy as first-line treatment in patients with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. To further support the efficacy and safety findings of the KEYNOTE-177 study, results of the health-related quality of life (HRQOL) analyses are reported here.

METHODS

KEYNOTE-177 is an open-label, randomised, phase 3 trial being done at 192 cancer centres in 23 countries, in patients aged 18 years and older with microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer, with an Eastern Cooperative Oncology Group performance status of 0 or 1, and who had not received previous systemic therapy for metastatic disease. Eligible patients were randomly assigned (1:1) centrally by use of interactive voice response or integrated web response technology to receive pembrolizumab 200 mg intravenously every 3 weeks or investigator's choice chemotherapy (mFOLFOX6 [leucovorin, fluorouracil, and oxaliplatin] or FOLFIRI [leucovorin, fluorouracil, and irinotecan] intravenously every 2 weeks with or without intravenous bevacizumab or cetuximab). Patients and investigators were not masked to treatment assignment. The primary endpoints were progression-free survival (previously reported) and overall survival (data to be reported at the time of the final analysis). HRQOL outcomes were evaluated as prespecified exploratory endpoints. The analysis population comprised all randomly assigned patients who received at least one dose of study treatment and completed at least one HRQOL assessment. HRQOL outcomes were mean change from baseline to prespecified week 18 in European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and EORTC Quality of Life Questionnaire-Colorectal 29 (EORTC QLQ-CR29) scale and item scores, and in the EuroQoL 5 Dimensions 3 Levels (EQ-5D-3L) visual analogue scale and health utility scores; the proportion of patients with improved, stable, or deteriorated scores from baseline to prespecified week 18 in EORTC QLQ-C30 scales and items; and time to deterioration in EORTC QLQ-C30 global health status/quality of life (GHS/QOL), physical functioning, social functioning, and fatigue scores and EORTC QLQ-CR29 urinary incontinence scores. The threshold for a small and clinically meaningful mean difference in EORTC QLQ-C30 score was 5-8 points. This study is registered with ClinicalTrials.gov, NCT02563002 and is ongoing; recruitment is closed.

FINDINGS

Between Feb 11, 2016, and Feb 19, 2018, 307 patients were enrolled and randomly assigned to receive pembrolizumab (n=153) or chemotherapy (n=154). The HRQOL analysis population comprised 294 patients (152 receiving pembrolizumab and 142 receiving chemotherapy). As of Feb 19, 2020, median time from randomisation to data cutoff was 32·4 months (IQR 27·7-37·8). Least squares mean (LSM) change from baseline to prespecified week 18 showed a clinically meaningful improvement in EORTC QLQ-C30 GHS/QOL scores with pembrolizumab versus chemotherapy (between-group LSM difference 8·96 [95% CI 4·24-13·69]; two-sided nominal p=0·0002). Median time to deterioration was longer with pembrolizumab versus chemotherapy for GHS/QOL (hazard ratio 0·61 [95% CI 0·38-0·98]; one-sided nominal p=0·019), physical functioning (0·50 [95% CI 0·32-0·81]; one-sided nominal p=0·0016), social functioning (0·53 [95% CI 0·32-0·87]; one-sided nominal p=0·0050), and fatigue scores (0·48 [95% CI 0·33-0·69]; one-sided nominal p<0·0001).

INTERPRETATION

Pembrolizumab monotherapy led to clinically meaningful improvements in HRQOL compared with chemotherapy in patients with previously untreated microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer. These data, along with the previously reported clinical benefits, support pembrolizumab as a first-line treatment option for this population.

FUNDING

Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ, USA.

CD4 T Cell-Dependent Rejection of Beta-2 Microglobulin Null Mismatch Repair-Deficient Tumors

Inactivation of beta-2 microglobulin (B2M) is considered a determinant of resistance to immune checkpoint inhibitors (ICPi) in melanoma and lung cancers. In contrast, B2M loss does not appear to affect response to ICPis in mismatch repair-deficient (MMRd) colorectal tumors where biallelic inactivation of B2M is frequently observed. We inactivated B2m in multiple murine MMRd cancer models. Although MMRd cells would not readily grow in immunocompetent mice, MMRd B2m null cells were tumorigenic and regressed when treated with anti-PD-1 and anti-CTLA4. The efficacy of ICPis against MMRd B2m null tumors did not require CD8⁺ T cells but relied on the presence of CD4⁺ T cells. Human tumors expressing low levels of B2M display increased intratumoral CD4⁺ T cells. We conclude that B2M inactivation does not blunt the efficacy of ICPi in MMRd tumors, and we identify a unique role for CD4⁺ T cells in tumor rejection. SIGNIFICANCE: B2M alterations, which impair antigen presentation, occur frequently in microsatellite-unstable colorectal cancers. Although in melanoma and lung cancers B2M loss is a mechanism of resistance to immune checkpoint blockade, we show that MMRd tumors respond to ICPis through CD4⁺ T-cell activation.This article is highlighted in the In This Issue feature, p. 1601.

Challenges of the current precision medicine approach for pancreatic cancer: A single institution experience between 2013 and 2017

Recent research on genomic profiling of pancreatic ductal adenocarcinoma (PDAC) has identified many potentially actionable alterations. However, the feasibility of using genomic profiling to guide routine clinical decision making for PDAC patients remains unclear. We retrospectively reviewed PDAC patients between October 2013 and December 2017, who underwent treatment at the Johns Hopkins Hospital and had clinical tumor next-generation sequencing (NGS) through commercial resources. Ninety-two patients with 93 tumors tested were included. Forty-eight (52%) patients had potentially curative surgeries. The median time from the tissue available to the NGS testing ordered was 229 days (interquartile range 62-415). A total of three (3%) patients had matched targeted therapies based on genomic profiling results. Genomic profiling guided personalized treatment for PDAC patients is feasible, but the percentage of patients who receive targeted therapy is low. The main challenges are ordering NGS testing early in the clinical course of the disease and the limited evidence of using a targeted approach in these patients. A real-time department level genomic testing ordering system in combination with an evidence-based flagging system for potentially actionable alterations could help address these shortcomings.

Long-term outcomes with neoadjuvant chemotherapy with or without stereotactic body radiation therapy in patients with borderline resectable and locally advanced pancreatic adenocarcinoma

443

Background: Patients (pts) withborderline resectable pancreatic cancer (BRPC) or locally advanced pancreatic cancer (LAPC) are at high risk of margin positive resection with upfront surgery. Pre-operative stereotactic body radiation therapy (SBRT) may help sterilize vascular margins, but its additive benefit beyond multi-agent chemotherapy (CTX) is unclear. We report on long-term outcomes from a high-volume institution of BRPC/LAPC pts who were reviewed by a multidisciplinary team and explored after either multi-agent CTX alone or multi-agent CTX followed by SBRT. Methods: Consecutive BRPC/LAPC pts diagnosed 2011-2016 who underwent resection following CTX alone or CTX followed by 5-fraction SBRT (CTX-SBRT) were retrospectively reviewed. Baseline demographic, clinical, and treatment factors were compared between cohorts, and survival analysis was conducted to compare pathologic and survival outcomes. Results: Of 199 pts, 77 received CTX alone and 122 received CTX-SBRT. There was no significant difference between cohorts in age, gender, performance status, tumor location, CA19-9 at diagnosis, or post-CTX CA19-9 values (all p > 0.05). The CTX-SBRT cohort had a higher proportion of pts with LAPC as compared to the CTX cohort (53% vs 22%, p< 0.001). Modified FOLFIRINOX (mFFX) was administered to 55% of pts, while 70% of pts received either mFFX or gemcitabine/abraxane, with no difference between cohorts. Duration of CTX was longer in the CTX-SBRT cohort as compared to the CTX cohort (median 4.6 vs. 2.9 mos, p= 0.03), but adjuvant CTX was not given as often in the CTX-SBRT arm (60.4% vs. 86.4%, p= < 0.001). Notably, 30% of the CTX cohort also received adjuvant chemoradiation. Pathologic response was significantly improved in the CTX-SBRT cohort vs the CTX cohort, specifically negative margins (92% vs 70%, p< 0.001), node negative (59% vs. 42%, p< 0.001), and pathologic complete response (7% vs. 0%, p= 0.02). On multivariable analysis, after controlling for prognostic factors, CTX-SBRT remained significantly associated with margin negative resection ( p< 0.001). Despite having more advanced stage and less adjuvant therapy administration in the CTX-SBRT cohort, there was no significant difference in overall survival after surgery (median OS: 24.6 vs. 22.2 mo, p= 0.79), local progression free survival (14.0 vs. 13.6 mo, p= 0.33), or distant metastasis free survival (16.4 vs. 11.8 mo, p= 0.33). Conclusions: Despite more advanced disease at presentation, BRPC/LAPC pts treated with CTX-SBRT were more likely to undergo margin negative resection and experienced similar survival outcomes, as compared to CTX alone. More data are needed to refine which patients benefit from neoadjuvant SBRT and how RT administration can be optimized to impact survival outcomes.

Long-term outcomes of a prospective single institution study with multiagent chemotherapy and stereotactic body radiation therapy in locally advanced or recurrent pancreatic adenocarcinoma

440

Background: We previously reported a multi-center study in which gemcitabine and stereotactic body radiation therapy (SBRT) were shown to be safe with outcomes comparable to chemoradiation in locally advanced pancreatic cancer (LAPC). This prospective clinical trial was developed to evaluate the efficacy of adding SBRT to multi-agent chemotherapy in LAPC. Herein, we report on the long-term survival outcomes. Methods: From 2012 to 2015, 48 patients (pts) were prospectively enrolled after multidisciplinary evaluation at a single high-volume pancreatic center. Pts received multi-agent chemotherapy (CTX) with modified mFOLFIRINOX (mFFX) or gemcitabine/abraxane followed by 5 fractions of SBRT (median 33 Gy; range, 25-33 Gy). At the time of fiducial placement, biopsies were obtained and DNA extracted for targeted sequencing using MSK-IMPACT. Kaplan-Meier curves were generated to compare survival outcomes by sub-group. Multivariate analysis (MVA) was performed to identify factors prognostic for survival. Results: 44 pts (91.7%) had LAPC disease and 4 (8.3%) had locally recurrent disease. The median follow-up interval was 21.5 months (mo) from diagnosis. CTX consisted of mFFX in 25 pts (52.1%) with 24 pts (50.0%) receiving therapy for a duration ≥4 mo. Of 44 pts with LAPC, 15 (34.1%) were surgically explored, and 11 (73.3%) achieved a margin-negative resection. From diagnosis and after completion of SBRT, respectively, the median overall survival (OS) was 21.6 (95% CI 16-29.7 mo) and 14.6 mo (95% CI: 11.6-23.0 mo); median progression free survival (PFS) was 13.2 (95% CI 11.9-18.1mo) and 6.4 mo (95% CI: 5-12.7 mo); median local PFS (LPFS) was 23.9 (95% CI 18.9-56.9 mo) and 15.8 mo (95% CI: 12.9-27.6 mo); and median distant metastasis free survival (DMFS) was 18.4 (95% CI 12.6-29.3 mo) and 8.5 mo (95% CI: 6.3-17.2 mo). Resected pts experienced better DMFS at 1-year (78% vs. 34%, p= 0.004) with an improved trend for 1-year OS (73% vs. 52%, p= 0.331). If CTX duration was ≥4 mo, 1-year OS (75% vs. 42%, p= 0.018), PFS (50% vs. 21%, p= 0.022), and DMFS (72% vs. 29%, p= 0.031) were significantly improved. In 44 LAPC pts, MVA confirmed ≥4 mo duration of CTX was associated with OS, PFS, and DMFS. Surgical resection was associated with improved DMFS, and CA19-9 level prior to SBRT was associated with PFS and LPFS. The most common mutations detected from biopsy specimens were KRAS (64.3%) , TP53 (50%), and SMAD4 (16.7%). Conclusions: In a prospective trial of pts with LAPC receiving multiagent CTX and SBRT, clinical outcomes were improved with longer durations of CT ( > 4 mo). A high proportion of LAPC pts underwent margin negative resection with favorable outcomes. Future studies should focus on which pts are most likely to benefit from SBRT and surgery following multiagent CTX. In pts who cannot undergo resection, escalated doses of SBRT may be indicated. Clinical trial information: NCT01781728.

KEYNOTE-177: Phase III randomized study of pembrolizumab versus chemotherapy for microsatellite instability-high advanced colorectal cancer

6

Background: KEYNOTE-177 (NCT02563002) evaluated the antitumor activity of pembrolizumab (pembro) vs chemotherapy ± bevacizumab or cetuximab (chemo) as first-line therapy for patients with microsatellite-instability high/mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC). We present results of the final PFS analysis and analysis of PFS2. Methods: Patients with locally-determined MSI-H/dMMR mCRC and ECOG PS 0 or 1 were randomized 1:1 to first-line pembro 200 mg Q3W for up to 2 years or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab (chosen before randomization). Treatment continued until progression, unacceptable toxicity, patient/investigator decision to withdraw, or completion of 35 cycles (pembro only). Patients receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were PFS (RECIST v1.1, central review) and OS. Secondary end points included ORR (RECIST v1.1, central review) and safety. Exploratory endpoints included duration of response (DOR), PFS2 (time from randomization to progression on next line of therapy or any cause death), and health-related quality of life (HRQoL). Data cutoff was Feb 19, 2020. Results: At data cutoff a total of 307 patients were randomized (153 to pembro, 154 to chemo). Median (range) study follow-up was 32.4 mo (24.0-48.3). Pembro was superior to chemo for PFS (median 16.5 mo vs 8.2 mo; HR 0.60; 95% CI, 0.45-0.80; P= 0.0002). The 12- and 24-mo PFS rates were 55.3% and 48.3% with pembro vs 37.3% and 18.6% with chemo. Confirmed ORR was 43.8% vs 33.1%; median (range) DOR was not reached (2.3+ to 41.4+) with pembro vs 10.6 mo (2.8 to 37.5+) with chemo. PFS2 was longer with pembro vs chemo (median not reached vs 23.5 mo [HR 0.63; 95% CI, 0.45-0.88]). OS analysis is ongoing. Grade ≥3 treatment related adverse event (TRAE) rates were 22% vs 66% for pembro vs chemo. There were no grade 5 TRAEs in the pembro arm and 1 grade 5 intestinal perforation in the chemo arm. HRQoL scores were improved with pembro vs chemo. Conclusions: Pembro provided a statistically significant improvement in PFS vs chemo as first-line therapy for patients with MSI-H/dMMR mCRC, with fewer TRAEs observed. Furthermore, pembro provided a clinically meaningful improvement in PFS2 for patients with MSI-H/dMMR mCRC. Clinical trial information: NCT02563002.

Survival Outcomes of Adjuvant Chemotherapy Combined With Radiation Versus Chemotherapy Alone After Pancreatectomy for Distal Pancreatic Adenocarcinoma: A Single-Institution Experience

OBJECTIVE

We evaluated survival outcomes in patients with distal pancreatic ductal adenocarcinoma (D-PDAC) after distal pancreatectomy (DP) and adjuvant chemotherapy or chemoradiation.

METHODS

A retrospective analysis of patients who underwent DP for D-PDAC from 2000 to 2015 at the Johns Hopkins Hospital was performed. Demographics, baseline risk factors, and type of adjuvant treatment were assessed for associations with overall survival (OS) and disease-free survival (DFS). Comparisons were made with log-rank tests and Cox proportional hazards regression models.

RESULTS

A total of 294 patients underwent DP for D-PDAC. Of these, 105 patients were followed at the Johns Hopkins Hospital. Forty-five patients received chemotherapy only and 60 patients received chemoradiation. The median OS with chemoradiation was 33.6 months and 27.9 months (P = 0.54) with chemotherapy only. The median DFS was 15.3 months with chemoradiation and 19.8 months with chemotherapy only (P = 0.89). Elevated carbohydrate antigen 19-9, stage II to III disease, splenic vein involvement, and vascular invasion were significant risk factors in multivariate analyses.

CONCLUSIONS

In this retrospective analysis, there were no significant differences in OS or DFS with chemoradiation compared with chemotherapy alone after DP in patients with D-PDAC.

Vaccine-Induced Intratumoral Lymphoid Aggregates Correlate with Survival Following Treatment with a Neoadjuvant and Adjuvant Vaccine in Patients with Resectable Pancreatic Adenocarcinoma

PURPOSE

Immunotherapy is currently ineffective for nearly all pancreatic ductal adenocarcinomas (PDAC), largely due to its tumor microenvironment (TME) that lacks antigen-experienced T effector cells (Teff). Vaccine-based immunotherapies are known to activate antigen-specific Teffs in the peripheral blood. To evaluate the effect of vaccine therapy on the PDAC TME, we designed a neoadjuvant and adjuvant clinical trial of an irradiated, GM-CSF-secreting, allogeneic PDAC vaccine (GVAX).

PATIENTS AND METHODS

Eighty-seven eligible patients with resectable PDAC were randomly assigned (1:1:1) to receive GVAX alone or in combination with two forms of low-dose cyclophosphamide. Resected tumors following neoadjuvant immunotherapy were assessed for the formation of tertiary lymphoid aggregates (TLA) in response to treatment. The clinical endpoints are disease-free survival (DFS) and overall survival (OS).

RESULTS

The neoadjuvant treatment with GVAX either alone or with two forms of low-dose cyclophosphamide is safe and feasible without adversely increasing the surgical complication rate. Patients in Arm A who received neoadjuvant and adjuvant GVAX alone had a trend toward longer median OS (35.0 months) than that (24.8 months) in the historical controls who received adjuvant GVAX alone. However, Arm C, who received low-dose oral cyclophosphamide in addition to GVAX, had a significantly shorter DFS than Arm A. When comparing patients with OS > 24 months to those with OS < 15 months, longer OS was found to be associated with higher density of intratumoral TLA.

CONCLUSIONS

It is safe and feasible to use a neoadjuvant immunotherapy approach for PDACs to evaluate early biologic responses. In-depth analysis of TLAs is warranted in future neoadjuvant immunotherapy clinical trials.

Pembrolizumab in Microsatellite-Instability-High Advanced Colorectal Cancer

BACKGROUND

Programmed death 1 (PD-1) blockade has clinical benefit in microsatellite-instability-high (MSI-H) or mismatch-repair-deficient (dMMR) tumors after previous therapy. The efficacy of PD-1 blockade as compared with chemotherapy as first-line therapy for MSI-H-dMMR advanced or metastatic colorectal cancer is unknown.

METHODS

In this phase 3, open-label trial, 307 patients with metastatic MSI-H-dMMR colorectal cancer who had not previously received treatment were randomly assigned, in a 1:1 ratio, to receive pembrolizumab at a dose of 200 mg every 3 weeks or chemotherapy (5-fluorouracil-based therapy with or without bevacizumab or cetuximab) every 2 weeks. Patients receiving chemotherapy could cross over to pembrolizumab therapy after disease progression. The two primary end points were progression-free survival and overall survival.

RESULTS

At the second interim analysis, after a median follow-up (from randomization to data cutoff) of 32.4 months (range, 24.0 to 48.3), pembrolizumab was superior to chemotherapy with respect to progression-free survival (median, 16.5 vs. 8.2 months; hazard ratio, 0.60; 95% confidence interval [CI], 0.45 to 0.80; P = 0.0002). The estimated restricted mean survival after 24 months of follow-up was 13.7 months (range, 12.0 to 15.4) as compared with 10.8 months (range, 9.4 to 12.2). As of the data cutoff date, 56 patients in the pembrolizumab group and 69 in the chemotherapy group had died. Data on overall survival were still evolving (66% of required events had occurred) and remain blinded until the final analysis. An overall response (complete or partial response), as evaluated with Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1, was observed in 43.8% of the patients in the pembrolizumab group and 33.1% in the chemotherapy group. Among patients with an overall response, 83% in the pembrolizumab group, as compared with 35% of patients in the chemotherapy group, had ongoing responses at 24 months. Treatment-related adverse events of grade 3 or higher occurred in 22% of the patients in the pembrolizumab group, as compared with 66% (including one patient who died) in the chemotherapy group.

CONCLUSIONS

Pembrolizumab led to significantly longer progression-free survival than chemotherapy when received as first-line therapy for MSI-H-dMMR metastatic colorectal cancer, with fewer treatment-related adverse events. (Funded by Merck Sharp and Dohme and by Stand Up to Cancer; KEYNOTE-177 ClinicalTrials.gov number, NCT02563002.).

Abstract PR-004: Systemic and intratumoral immune profiling in metastatic pancreatic cancer patients who received front-line FOLFIRINOX and were treated with combination immunotherapy with CTLA-4 blockade in the maintenance setting

Background: Metastatic pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis with a 5-year survival rate of 10%. For patients with metastatic PDA who respond to but cannot tolerate multi-agent chemotherapy, such as FOLFIRINOX, beyond 4-6 months, the optimal approach is unknown. Few studies have evaluated immunotherapy in the maintenance setting for PDA. Previously, a phase 2 trial in advanced PDA showed the promise of a GM-CSF-secreting allogeneic pancreatic tumor cell-based vaccine (GVAX) with CTLA-4 inhibitor, ipilimumab (IPI) [1]. Here we describe the first clinical testing of GVAX + IPI in the maintenance setting for patients with metastatic PDA who had ongoing response or stable disease after front-line FOLFIRINOX and evaluation of immune cell changes within the peripheral blood and tumor. Methods: From 40 vaccinated patients, we obtained paired peripheral blood lymphocytes (PBLs) from 20 patients and metastatic PDA biopsies from 6 of these 20 patients at baseline and week 7 (after at least two doses of GVAX + IPI). Samples were stratified into “stable” or “progressive” cohorts based on disease status on first restaging scan. To profile peripheral immune responses to treatment, we performed mass cytometry (CyTOF) analysis using a T cell-focused panel on PBLs. To profile intratumoral immune responses, biopsies containing &gt;30% tumor cellularity were chosen for 10-plex multiplex immunohistochemistry with T cell and myeloid cell-focused panels allowing us to examine changes in immune cell subsets after GVAX + IPI. Results. GVAX + IPI led to noticeable changes in PBLs including increases in T helper and cytotoxic effector memory cells and decrease in naïve cytotoxic T cells, regardless of disease status. Among co-inhibitory markers assayed on PBLs, GVAX + IPI upregulated TIM3 and PD-1 in most helper and cytotoxic T cells, while CTLA-4 was largely maintained. Interrogation of the metastatic tumor microenvironment at baseline and on-treatment revealed significant increases in CD8+ T cells and pro-inflammatory M1 macrophages and decrease in pro-tumor M2 macrophages. Based on the CD8+ T cell functional status, there were increases in late effector (EOMES-PD-1+) and memory (EOMES-PD-1-) CD8+ T cells in the metastatic tumor after immunotherapy. Conclusions: In summary, we have proposed a mechanism for our immunotherapy in the maintenance setting. GVAX may be inducing systemic and intratumoral activation of naïve T cells to antigen-specific T cells and promoting a decrease in immunosuppressive cells in the metastatic PDA microenvironment. Meanwhile, IPI may be blocking CTLA-4, which improves priming of T cells, but also may be leading to upregulation of regulatory markers TIM3 and PD-1 on T cell subsets as a compensatory mechanism. This trial highlights the challenge to inducing effective anti-tumor immune responses in metastatic PDA with inducible counterregulatory mechanisms. These compensatory increases could provide targets for the next generation of studies. 1Le DT, et al. J Immunother. 2013

Citation Format: Annie A. Wu, Katherine M. Bever, Won Jin Ho, Elana J. Fertig, Nan Niu, Lei Zheng, Rose M. Parkinson, Jennifer N. Durham, Beth Onners, Anna K. Ferguson, Cara Wilt, Andrew H. Ko, Andrea Wang-Gillam, Daniel A. Laheru, Robert A. Anders, Elizabeth D. Thompson, Elizabeth A. Sugar, Elizabeth M. Jaffee, Dung T. Le. Systemic and intratumoral immune profiling in metastatic pancreatic cancer patients who received front-line FOLFIRINOX and were treated with combination immunotherapy with CTLA-4 blockade in the maintenance setting [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PR-004.

Evaluation of Cyclophosphamide/GVAX Pancreas Followed by Listeria-Mesothelin (CRS-207) with or without Nivolumab in Patients with Pancreatic Cancer

PURPOSE

Two studies in previously treated metastatic pancreatic cancer have been completed combining GVAX pancreas vaccine (GM-CSF-secreting allogeneic pancreatic tumor cells) with cyclophosphamide (Cy) and CRS-207 (live, attenuated Listeria monocytogenes-expressing mesothelin). In the current study, we compared Cy/GVAX followed by CRS-207 with (Arm A) or without nivolumab (Arm B).

PATIENTS AND METHODS

Patients with pancreatic adenocarcinoma who received one prior therapy for metastatic disease and RECIST measurable disease were randomized 1:1 to receive treatment on Arm A or Arm B. The primary objective was to compare overall survival (OS) between the arms. Additional objectives included assessment of progression-free survival, safety, tumor responses, CA19-9 responses, and immunologic correlates.

RESULTS

Ninety-three patients were treated (Arm A, 51; Arm B, 42). The median OS in Arms A and B were 5.9 [95% confidence interval (CI), 4.7-8.6] and 6.1 (95% CI, 3.5-7.0) months, respectively, with an HR of 0.86 (95% CI, 0.55-1.34). Objective responses were seen in 3 patients using immune-related response criteria (4%, 2/51, Arm A; 2%, 1/42, Arm B). The grade ≥3 related adverse event rate, whereas higher in Arm A (35.3% vs. 11.9%) was manageable. Changes in the microenvironment, including increase in CD8+ T cells and a decrease in CD68+ myeloid cells, were observed in long-term survivors in Arm A only.

CONCLUSIONS

Although the study did not meet its primary endpoint of improvement in OS of Arm A over Arm B, the OS was comparable with standard therapy. Objective responses and immunologic changes in the tumor microenvironment were evident.

Inactivation of human norovirus and its surrogate by the disinfectant consisting of calcium hydrogen carbonate mesoscopic crystals

Human norovirus is one of the major causes of foodborne gastroenteritis, and it can be easily transmitted from infected person, virus-contaminated foods and environmental surfaces. Effective disinfection method is needed to stop the transmission of human norovirus. CAC-717 is a new disinfectant consisting of calcium hydrogen carbonate mesoscopic crystals. We aimed to evaluate the efficacy of CAC-717 against human norovirus. This study used human norovirus derived from fecal specimens and cultured murine norovirus, which is one of the surrogate viruses for human norovirus. The disinfection effect against murine norovirus was estimated by infectivity assay and transmission electron microscopy. The inactivation effect against human norovirus was assessed by reverse transcription polymerase chain reaction. Disinfection effect of CAC-717 against the infectivity of murine norovirus was shown within 100 s after the CAC-717 treatment, presenting the destruction of viral capsids. The treatment of CAC-717 significantly reduced human norovirus genomic RNA (3.25-log reduction) by the presence of the mesoscopic structure of calcium hydrogen carbonate. CAC-717 stably inactivated human norovirus in stool suspensions. The inactivation effect of CAC-717 against human norovirus was less susceptible to organic substances than sodium hypochlorite. CAC-717 would be a useful alternative for disinfecting human norovirus in contaminated environmental surfaces.

A Phase II Study of Allogeneic GM-CSF-Transfected Pancreatic Tumor Vaccine (GVAX) with Ipilimumab as Maintenance Treatment for Metastatic Pancreatic Cancer

PURPOSE

This phase II study tested granulocyte-macrophage colony-stimulating factor (GM-CSF)-allogeneic pancreatic tumor cells (GVAX) and ipilimumab in metastatic pancreatic ductal adenocarcinoma (PDA) in the maintenance setting.

PATIENTS AND METHODS

Patients with PDA who were treated with front-line chemotherapy consisting of 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX) in the metastatic setting and had ongoing response or stable disease after 8-12 doses were eligible. Patients were randomized 1:1 to treatment with GVAX and ipilimumab given every 3 weeks for four doses then every 8 weeks (Arm A) or to FOLFIRINOX continuation (Arm B). The primary objective was to compare overall survival (OS) between the two arms.

RESULTS

Eighty-two patients were included in the final analysis (Arm A: 40; Arm B: 42). The study was stopped for futility after interim analysis. Median OS was 9.38 months [95% confidence interval (CI), 5.0-12.2] for Arm A and 14.7 months (95% CI, 11.6-20.0) for Arm B (HR, 1.75; P = 0.019). Using immune-related response criteria, two partial responses (5.7%) were observed in Arm A and four (13.8%) in Arm B. GVAX + ipilimumab promoted T-cell differentiation into effector memory phenotypes both in the periphery and in the tumor microenvironment and increased M1 macrophages in the tumor.

CONCLUSIONS

GVAX and ipilimumab maintenance therapy did not improve OS over continuation of chemotherapy and resulted in a numerically inferior survival in metastatic PDA. However, clinical responses and biological effects on immune cells were observed. Further study of novel combinations in the maintenance treatment of metastatic PDA is feasible.

Pembrolizumab versus chemotherapy for microsatellite instability-high/mismatch repair deficient metastatic colorectal cancer: The phase 3 KEYNOTE-177 Study

LBA4

Background: KEYNOTE-177 (NCT02563002) is a phase 3, randomized open-label study evaluating the efficacy and safety of pembrolizumab (pembro) versus standard of care chemotherapy ± bevacizumab or cetuximab (chemo) as first-line therapy for patients (pts) with microsatellite-instability high/mismatch repair deficient (MSI-H/dMMR) metastatic colorectal cancer (mCRC). We present results of the final PFS analysis. Methods: A total of 307 pts with MSI-H/dMMR mCRC as determined locally and ECOG PS 0 or 1 were randomly assigned 1:1 to first-line pembro 200 mg Q3W for up to 2 years or investigator’s choice of mFOLFOX6 or FOLFIRI Q2W ± bevacizumab or cetuximab (chemo chosen prior to randomization). Treatment continued until PD, unacceptable toxicity, pt/investigator decision to withdraw, or completion of 35 cycles (pembro only). Patients receiving chemo could crossover to pembro for up to 35 cycles after confirmed PD. Primary end points were PFS (RECIST v1.1, central review) and OS. Key secondary end points included ORR (RECIST v1.1, central review), and safety. The data cutoff date for this interim analysis was Feb 19, 2020. The study will continue without changes to evaluate OS. Results: At data cutoff, 153 pts were randomized to pembro and 154 to chemo. Median (range) study follow-up was 28.4 mo (0.2-48.3) with pembro vs 27.2 mo (0.8-46.6) with chemo. Pembro was superior to chemo for PFS (median 16.5 mo vs 8.2 mo; HR 0.60; 95% CI, 0.45-0.80; P=0.0002). The 12- and 24-mo PFS rates were 55.3% and 48.3% with pembro vs 37.3% and 18.6% with chemo. Confirmed ORR was 43.8% vs 33.1%; median (range) duration of response was not reached (2.3+ to 41.4+) with pembro vs 10.6 mo (2.8 to 37.5+) with chemo. Grade 3-5 treatment related adverse event (AE) rates were 22% vs 66% for pembro vs chemo. One pt in the chemo arm died due to a treatment-related AE. Conclusions: Pembro provided a clinically meaningful and statistically significant improvement in PFS versus chemo as first-line therapy for pts with MSI-H/dMMR mCRC, with fewer treatment-related AEs observed and should be the new standard of care for these pts. Clinical trial information: NCT02563002 .

An exploratory study of metformin with or without rapamycin as maintenance therapy after induction chemotherapy in patients with metastatic pancreatic adenocarcinoma

Purpose: Metformin combined with the mTOR inhibitor rapamycin showed potential synergistic anti-tumor activity in preclinical studies in pancreatic ductal adenocarcinoma (PDA). This phase 1b study (NCT02048384) was conducted to evaluate the feasibility and activity of metformin +/– rapamycin in the maintenance setting for unselected patients with metastatic PDA (mPDA) treated with chemotherapy.

Materials and Methods: Eligible patients with stable or responding mPDA after ≥ 6 months on chemotherapy were randomized 1:1 to metformin alone (Arm A) or with rapamycin (Arm B), stratified by prior treatment with FOLFIRINOX. Fluorodeoxyglucose (FDG) PET scans and peripheral blood mononuclear cells were obtained for exploratory analyses.

Results: 22 subjects (11 per arm) received treatment per protocol. Median PFS/OS were 3.5 and 13.2 months respectively, with 2 year OS rate of 37%; there were no differences between arms. No responses were observed by RECIST; however, decreases in FDG avidity and/or CA19-9 were observed in several long-term survivors. Treatment related adverse events of Grade ≥ 3 occurred in 0% vs 27% of patients in Arm A vs B and were asymptomatic hematologic or electrolyte abnormalities that were not clinically significant. Improved survival was associated with low baseline neutrophil: lymphocyte ratio, baseline lack of assessable disease by PET, and greater expansion of dendritic cells following treatment.

Conclusions: Metformin +/– rapamycin maintenance for mPDA was well-tolerated and several patients achieved stable disease associated with exceptionally long survival. Further prospective studies are needed to clarify the role of these agents in the maintenance setting and to enhance patient selection for such approaches.

Pembrolizumab monotherapy for patients with advanced MSI-H colorectal cancer: Longer-term follow-up of the phase II, KEYNOTE-164 study

4032

Background: Pembrolizumab provides effective antitumor immunity and durable responses in patients (pts) with advanced, colorectal cancer (CRC) with microsatellite instability-high (MSI-H) tumors. We present data on antitumor immunity with pembrolizumab in pts from the phase 2, KEYNOTE-164 study who had approximately 3 years of follow-up, and in pts re-treated after disease progression. Methods: KEYNOTE-164 enrolled pts with metastatic MSI-H CRC, MSI-H status confirmed locally by IHC or PCR, and ≥2 (cohort A) or ≥1 (cohort B) prior lines of therapy (fluoropyrimidine, oxaliplatin, irinotecan, or anti VEGF/EGFR). Eligible pts received pembrolizumab 200 mg Q3W for 2y (35 administrations) or until progression, unacceptable toxicity, or withdrawal. Pts who stopped pembro due to a confirmed CR or after completing 2y of treatment and who progressed after stopping were eligible for re-treatment with up to 17 administrations in the second-course phase, at investigator discretion. Tumor response was assessed Q9W per RECIST v1.1 by independent review. The primary endpoint was ORR. Secondary endpoints included DOR, PFS, OS, and safety. The data cutoff date was Sep 9, 2019. Results: At data cutoff, the median follow-up was 31.4 mo (range, 0.2-47.8) for 61 pts in cohort A and 36.1 mo (0.1-39.3) for 63 pts in cohort B. ORR was 32.8% (3CR, 17PR; 95% CI% 21.3-46.0) for cohort A and 34.9% (8CR, 14PR; 95% CI 23.3-48.0) in cohort B. Median DOR was not reached (NR [range, 6.2-41.3+]) and not reached (range, 3.9+ to 37.1+), respectively. Fifteen pts in cohort A and 17 in cohort B had ongoing responses at data cutoff. Median PFS was 2.3 mo (95% CI 2.1-8.1) with 3-yr PFS rate of 31% in cohort A and was 4.1 mo (2.1-18.9) with 3-yr PFS rate of 34% in cohort B. Median OS was 31.4 mo (21.4-NR) with 3-yr OS rate of 49% in cohort A and was not reached (19.2-NR) with 3-yr OS rate of 52% in cohort B. Nine pts (6 in cohort A, 3 in cohort B) had a second course of treatment. The best response in second course was PR in 1 patient each in cohort A and B. Grade 3-4 drug-related adverse events occurred in 10 (16%) pts in cohort A and 8 (13%) pts in cohort B. No grade 5 drug-related events occurred. Conclusions: After approximately 3 y of follow-up, pembrolizumab continues to provide effective long-term antitumor immunity with durable responses, with small numbers of drug-related adverse events and no drug-related deaths in pts with advanced, MSI-H CRC. Clinical trial information: NCT02460198 .

Abstract B13: Development of a low-cost method for collecting fecal samples in clinical trials

Although immune checkpoint inhibitors (ICIs) have shown promise in treating various cancers, fewer than half of patients with most tumor types experience a durable response. Thus, there is a need for biomarkers to better predict outcomes. Recent studies suggest that the presence of a handful of microbial species and greater alpha-diversity in the gut may serve as a biomarker for and might facilitate ICI responses. However, the specific bacteria, or bacterial communities, that associate with improved ICI responses vary across study populations, and the factors that contribute to these discrepant findings remain elusive. Thus, a standardized method by which biospecimens may be collected, transported, and stored for gut microbiome studies in the context of ICI therapy is needed. In this study, we evaluated a method for shipping fecal samples using a low-cost (&lt;$3.00) ThinPrep Pap Test® methanol-based preservative kit. Under an IRB-approved protocol, we recruited patients with melanoma, Merkel cell carcinoma, endometrial cancer, and non-small cell lung cancer who had experienced &gt;1 year of durable tumor response after ICI therapy. Patients were provided with stool collection kits and either asked to collect fecal samples at home within 48 hours of their clinic visit and store at 4°C (fresh) or asked to place stool in preservative and ship at ambient temperature to our laboratory (fixed). For fresh samples, a portion of each sample was frozen and another portion placed into preservative as a paired control. DNA was extracted using Zymo Quick-DNA™ Fecal/Soil Microbe kit. For fixed samples, methanol was removed by evaporation prior to DNA extraction. Microbial composition was analyzed with 16S rRNA amplicon sequencing with V1-V2 primers with 150bp paired-end sequencing using an Illumina platform. Among n=10 samples collected in clinic, fixed portions demonstrated decreased alpha-diversity and a uniform shift in beta-diversity compared to the paired frozen portions. In all fixed samples, Faecalibacterium and Roseburia relative abundance decreased with a corresponding increase in Bacteroides. Among a second set of n=11 samples that were placed in preservative by patients and then shipped to our laboratory, we analyzed the effects of shipping by comparing fresh stool samples and shipped fixed samples collected by the same patient within one month. The data revealed similar trends, suggesting that fixation, rather than shipping, drives the overall effect. We are currently verifying the relative abundance of specific bacterial species in both sets of samples using quantitative RT-PCR. Our data show that methanol-based preservation must be optimized prior to clinical utilization for accurate assessment. If optimized, we have identified a low-cost method to collect fecal samples that could be adopted in community practices and low-income areas. Ongoing work from our group includes optimization of processing procedures, ratio of fecal matter to preservative, and storage conditions.

Citation Format: Kimberly E. Peloza, Joell J. Gills, Fyza Y. Shaikh, James R. White, Sara Glass, Carisse Lansiquot, Courtney Stevens, William Assan, William H. Sharfman, Dung T. Le, Jarushka Naidoo, Evan J. Lipson, Drew M. Pardoll, Cynthia L. Sears. Development of a low-cost method for collecting fecal samples in clinical trials [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr B13.

Single-Cell Immune Competency Signatures Associate with Survival in Phase II GVAX and CRS-207 Randomized Studies in Patients with Metastatic Pancreatic Cancer

The identification of biomarkers for patient stratification is fundamental to precision medicine efforts in oncology. Here, we identified two baseline, circulating immune cell subsets associated with overall survival in patients with metastatic pancreatic cancer who were enrolled in two phase II randomized studies of GVAX pancreas and CRS-207 immunotherapy. Single-cell mass cytometry was used to simultaneously measure 38 cell surface or intracellular markers in peripheral blood mononuclear cells obtained from a phase IIa patient subcohort (N = 38). CITRUS, an algorithm for identification of stratifying subpopulations in multidimensional cytometry datasets, was used to identify single-cell signatures associated with clinical outcome. Patients with a higher abundance of CD8⁺CD45RO^-CCR7^-CD57⁺ cells and a lower abundance of CD14⁺CD33⁺CD85j⁺ cells had improved overall survival [median overall survival, range (days) 271, 43-1,247] compared with patients with a lower abundance of CD8⁺CD45RO^-CCR7^-CD57⁺ cells and higher abundance of CD14⁺CD33⁺CD85j⁺ cells (77, 24-1,247 days; P = 0.0442). The results from this prospective-retrospective biomarker analysis were validated by flow cytometry in 200 patients with pancreatic cancer enrolled in a phase IIb study (P = 0.0047). The identified immune correlates provide potential prognostic or predictive signatures that could be employed for patient stratification.