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Immunotherapy for pancreatic cancer: A 2020 update

  • Author Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Dimitrios Schizas
    Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Affiliations
    First Department of Surgery, National and Kapodistrian University of Athens, Laikon General Hospital, Athens, Greece
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  • Author Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Nikolaos Charalampakis
    Correspondence
    Corresponding author at: 79, Psaron St, 15343, Agia Paraskevi, Athens, Greece.
    Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Affiliations
    Department of Medical Oncology, Metaxa Cancer Hospital, Athens, Greece
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  • Author Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Christo Kole
    Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
    Affiliations
    First Department of Surgery, National and Kapodistrian University of Athens, Laikon General Hospital, Athens, Greece
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  • Panagiota Economopoulou
    Affiliations
    Department of Internal Medicine, Section of Medical Oncology, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
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  • Evangelos Koustas
    Affiliations
    Molecular Oncology Unit, Department of Biological Chemistry, National and Kapodistrian University of Athens, Athens, Greece
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  • Efthymios Gkotsis
    Affiliations
    First Department of Surgery, National and Kapodistrian University of Athens, Laikon General Hospital, Athens, Greece
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  • Dimitrios Ziogas
    Affiliations
    First Department of Medicine, National and Kapodistrian University of Athens, Laikon General Hospital, Athens, Greece
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  • Amanda Psyrri
    Affiliations
    Department of Internal Medicine, Section of Medical Oncology, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
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  • Michalis V. Karamouzis
    Affiliations
    Molecular Oncology Unit, Department of Biological Chemistry, National and Kapodistrian University of Athens, Athens, Greece
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  • Author Footnotes
    1 The three first authors (DS, NC and CK) have contributed equally to this work and can be considered co-first authors.
Published:March 25, 2020DOI:https://doi.org/10.1016/j.ctrv.2020.102016

      Highlights

      • Pancreatic adenocarcinoma (PAC) is associated with dismal prognosis.
      • Immunotherapy alone in unresectable PAC confers poor responses.
      • A clinical benefit is observed by immunotherapy and cytotoxic drugs combination.
      • Overall survival is increased when immunotherapy and other treatment modalities are combined.
      • Optimal patient selection is mandatory for successful treatment.

      Abstract

      Pancreatic adenocarcinoma (PAC) is associated with extremely poor prognosis and remains a lethal malignancy. The main cure for PAC is surgical resection. Further treatment modalities, such as surgery, chemotherapy, radiotherapy and other locoregional therapies provide low survival rates. Currently, many clinical trials seek to assess the efficacy of immunotherapeutic strategies in PAC, including immune checkpoint inhibitors, cancer vaccines, adoptive cell transfer, combinations with other immunotherapeutic agents, chemoradiotherapy or other molecularly targeted agents; however, none of these studies have shown practice changing results. There seems to be a synergistic effect with increased response rates when a combinatorial approach of immunotherapy in conjunction with other modalities is being exploited. In this review, we illustrate the current role of immunotherapy in PAC.

      Keywords

      Introduction

      Pancreatic adenocarcinoma (PAC) is the seventh leading cause of cancer-related death in both sexes, causing more than 331,000 deaths per year globally [
      • Ilic M.
      • Ilic I.
      Epidemiology of pancreatic cancer.
      ]. An estimation of 174,650 new cases was expected to be diagnosed in the USA with 45,750 deaths expected to occur in 2019 []. PAC is associated with an extremely poor prognosis reaching a 5-year overall survival (OS) rate below 5% [

      Siegel R, Miller K, Jemal A. Cancer statistics, 2015. CA Cancer J Clin 2015; 65: 5e29.

      ] and 1-year OS rate at 24% based on standard treatments [
      • Reyes-Gibby C.C.
      • Chan W.
      • Abbruzzese J.L.
      • Xiong H.Q.
      • Ho L.
      • Evans D.B.
      • et al.
      Patterns of self-reported symptoms in pancreatic cancer patients receiving chemoradiation.
      ]. Even for patients with resectable disease, the prognosis is very poor, reflecting an OS rate of only 17% [
      • Reyes-Gibby C.C.
      • Chan W.
      • Abbruzzese J.L.
      • Xiong H.Q.
      • Ho L.
      • Evans D.B.
      • et al.
      Patterns of self-reported symptoms in pancreatic cancer patients receiving chemoradiation.
      ]. The poor prognosis is mainly due to lack of early symptoms, rapid tumor progression and limited efficacy of available drugs in locoregional/metastatic disease [
      • Löhr M.
      Is it possible to survive pancreatic cancer?.
      ]. Even though the cause of PAC is still not well understood, certain risk factors have been associated with PAC, such as advancing age, family history, smoking and alcohol use, male sex, diabetes mellitus and obesity [
      • Vincent A.
      • Herman J.
      • Schulick R.
      • Hruban R.H.
      • Goggins M.
      Pancreatic cancer.
      ].
      Surgical resection and combination with chemoradiotherapy, either preoperatively or postoperatively, may improve long-term survival in localized disease; however, the majority of patients are diagnosed at advanced stage [
      • Bliss L.A.
      • Witkowski E.R.
      • Yang C.J.
      • Tseng J.F.
      Outcomes in operative management of pancreatic cancer.
      ]. Even after surgical resection, the 5-year OS rate does not exceed 20–25% [
      • Vincent A.
      • Herman J.
      • Schulick R.
      • Hruban R.H.
      • Goggins M.
      Pancreatic cancer.
      ] and the administration of more intensified chemotherapy regimens as adjuvant therapy, such as modified FOLFIRINOX has only modestly improved survival rates [
      • Conroy T.
      • Hammel P.
      • Hebbar M.
      • Ben Abdelghani M.
      • Wei A.C.
      • Raoul J.-L.
      • et al.
      FOLFIRINOX or Gemcitabine as Adjuvant Therapy for Pancreatic Cancer.
      ]. Therefore, there is an urgent need for more effective therapeutic strategies.
      In recent years, the incorporation of immunotherapy in the treatment algorithm of many solid tumors has marked a therapeutic renaissance in oncology [
      • Herzberg B.
      • Campo M.J.
      • Gainor J.F.
      Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer.
      ]. Cancer immunotherapy has occupied marginal therapeutic options to activate the immune system against tumor. Targeting of immune checkpoint molecules through inhibition of Cytotoxic T-Lymphocyte–associated Antigen 4 (CTLA-4), Programmed cell Death protein-1 (PD-1) and Programmed cell Death protein Ligand-1 (PD-L1) using monoclonal antibodies, has led to a paradigm shift in the treatment of melanoma, lung cancer, renal cell carcinoma, urothelial cancer, head and neck cancer and other malignancies [
      • Brower V.
      Checkpoint blockade immunotherapy for cancer comes of age.
      ]. CTLA-4 is an inhibitory receptor that modulates the initial stages of T cell activation and prevents immune hyperactivation by competitively inhibiting binding of B7 ligands to the co-stimulatory receptor Cluster Differentiation 28 (CD-28) [
      • Disis M.L.
      Mechanism of Action of Immunotherapy.
      ]. PD-1 protein is another T cell co-inhibitory receptor with more distinct biologic function than CTLA-4; it binds to PD-L1 and PD-L2 ligands preventing T cell activity in peripheral tissues [
      • Disis M.L.
      Mechanism of Action of Immunotherapy.
      ]. PD-L1 is the primary PD-1 ligand overexpressed and detected in several solid human cancers, such as pancreatic, esophageal, gastric, colon, lung and breast cancers [
      • Patel S.P.
      • Kurzrock R.
      PD-L1 Expression as a Predictive Biomarker in Cancer Immunotherapy.
      ].
      Therapeutic cancer vaccines have been used so far to effectively induce activation of cytotoxic T-lymphocytes (CTLs) against immunogenic tumor-associated antigens (TAA) [
      • Vacchelli E.
      • Martins I.
      • Eggermont A.
      • Fridman W.H.
      • Galon J.
      • Sautes-Fridman C.
      • et al.
      Trial watch: Peptide vaccines in cancer therapy.
      ]. The TAA epitopes are either whole-cell tumor lysates, tumor peptides or full-length proteins or recombinant viruses encoding for TAAs that are transferred and then presented by major histocompatibility complex (MHC) class I molecules in antigen-presenting cells (APCs) [
      • Aranda F.
      • Vacchelli E.
      • Eggermont A.
      • Galon J.
      • Sautes- Fridman C.
      • Tartour E.
      • et al.
      Watch: Peptide vaccines in cancer therapy.
      ]; whereas adoptive cell transfer (ACT) is used as personalized cancer immunotherapy involving readministration of a patient’s own immune cells after ex-vivo modification to be redirected toward relevant tumor antigens via engineered T cell receptors (TCRs) or Chimeric Antigen Receptor s (CARs) [
      • Akce M.
      • Zaidi M.Y.
      • Waller E.K.
      • El-Rayes B.F.
      • Lesinski G.B.
      The Potential of CAR T Cell Therapy in Pancreatic Cancer.
      ]. In the present work, we review the latest advances in immunotherapy in PAC.

      Immune checkpoint inhibitors in pancreatic adenocarcinoma

      Blockade of immune checkpoints by anti-CTLA-4 and/or anti-PD-1/anti-PD-L1 agents leads to T Cell activation and provides an effective approach for tumor immunotherapy [
      • Iwai Y.
      • Ishida M.
      • Tanaka Y.
      • Okazaki T.
      • Honjo T.
      • Minato N.
      Involvement of PD-L1 on tumor cells in the escape from host immune system and tumor immunotherapy by PD-L1 blockade.
      ]. However, despite demonstrating robust results in certain malignancies, most phase I and II clinical trials have failed to show any clinical efficacy in PAC (Table 1) [
      • Royal R.E.
      • Levy C.
      • Turner K.
      • Mathur A.
      • Hughes M.
      • Kammula U.S.
      • et al.
      Phase 2 trial of single agent Ipilimumab (anti-CTLA-4) for locally advanced or metastatic pancreatic adenocarcinoma.
      ,

      AstraZeneca. Study of Tremelimumab in Patients With Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT02527434; 2015.

      ]. Interestingly, combinations of therapeutic protocols using immune checkpoint inhibitors with radiotherapy and/or chemotherapy have shown encouraging results (Table 1).
      Table 1Immune Checkpoint inhibitors.
      InterventionStrategyCancer stageClinical phase/IdentifierOutcomes: Median Overall survival (Months)Bibliography
      IpilimumabCTLA-4 inhibitorUnresectable (stage IV) pancreatic cancerPhase II, NCT00112580No improvement in survival rate
      • Royal R.E.
      • Levy C.
      • Turner K.
      • Mathur A.
      • Hughes M.
      • Kammula U.S.
      • et al.
      Phase 2 trial of single agent Ipilimumab (anti-CTLA-4) for locally advanced or metastatic pancreatic adenocarcinoma.
      Ipilimumab, GemcitabineCTLA-4 inhibitor, Cytotoxic drugsLocally Advanced/unresectable (Stage III/ IV) or metastatic pancreatic cancerPhase Ib, NCT014739408.5 (95% CI 2.2–10.3)
      • Mohindra N.A.
      • Kircher S.M.
      • Nimeiri H.S.
      • Benson A.B.
      • Rademaker A.
      • Alonso E.
      • et al.
      Results of the phase Ib study of ipilimumab and gemcitabine for advanced pancreas cancer.
      ,
      • Kalyan A.
      • Kircher S.M.
      • Mohindra N.A.
      • Nimeiri H.S.
      • Maurer V.
      • Rademaker A.
      • et al.
      Ipilimumab and gemcitabine for advanced pancreas cancer: A phase Ib study.
      Ipilimumab, NivolumabCTLA-4 inhibitor, PD-1 inhibitorAdvanced/metastatic pancreatic cancerPhase I/II, NCT01928394Ongoing

      A Study of Nivolumab by Itself or Nivolumab Combined With Ipilimumab in Patients With Advanced or Metastatic Solid Tumors. https://clinicaltrials.gov/show/NCT01928394.

      TremelimumabCTLA-4 inhibitorAdvanced/metastatic pancreatic cancerPhase II, NCT025274344 (95% CI 2.83–5.42)

      AstraZeneca. Study of Tremelimumab in Patients With Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT02527434; 2015.

      Tremelimumab, DurvalumabCTLA-4 inhibitor, PD-1 inhibitorMetastatic pancreatic ductal adenocarcinomaPhase II, NCT025588943.1 (95% CI, 2.2–6.1), combination therapy

      3.6 (95% CI, 2.7–6.1), Durvalumab alone
      • O'Reilly E.M.
      • Oh D.Y.
      • Dhani N.
      • Renouf D.J.
      • Lee M.A.
      • Sun W.
      • et al.
      Durvalumab With or Without Tremelimumab for Patients With Metastatic Pancreatic Ductal Adenocarcinoma: A Phase 2 Randomized Clinical Trial.
      Tremelimumab, GemcitabineCTLA-4 inhibitor, Cytotoxic drugsAdvanced pancreatic cancerPhase I, NCT005560237.4 (95% CI, 5.8–9.4)
      • Aglietta M.
      • Barone C.
      • Sawyer M.B.
      • Moore M.J.
      • Miller W.H.
      • Bagalà C.
      • et al.
      A phase I dose escalation trial of tremelimumab (CP-675,206) in combination with gemcitabine in chemotherapy-naive patients with metastatic pancreatic cancer.
      Pembrolizumab, Gemcitabine, Nab-paclitaxelPD-1 inhibitor, Cytotoxic drugsAdvanced/metastatic pancreatic cancerPhase Ib/II, NCT0233125115.0 (95% CI, 6.8–22.6)
      • Weiss G.J.
      • Blaydorn L.
      • Beck J.
      • Bornemann-Kolatzki K.
      • Urnovitz H.
      • Schutz E.
      • et al.
      Correction to: Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.
      ,
      • Weiss G.J.
      • Blaydorn L.
      • Beck J.
      • Bornemann-Kolatzki K.
      • Urnovitz H.
      • Schutz E.
      • et al.
      Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.
      AtezolizumabPD-L1 inhibitorAdvanced pancreatic cancerPhase I/II, NCT03829501Ongoing

      Safety and Efficacy of KY1044 and Atezolizumab in Advanced Cancer. https://clinicaltrials.gov/show/NCT03829501.

      CTLA-4: Cytotoxic T-Lymphocyte–associated Antigen-4; PD-1: Programmed cell Death protein-1; PD-L1: Programmed cell Death protein Ligand-1.
      Ipilimumab is a fully humanized anti-CTLA-4 IgG1 monoclonal antibody (mAb) approved for clinical use in USA and Europe in 2011 [
      • Torphy R.J.
      • Zhu Y.
      • Schulick R.D.
      Immunotherapy for pancreatic cancer: Barriers and breakthroughs.
      ]; however, results have been disappointing in patients with locally advanced or metastatic PAC [
      • Royal R.E.
      • Levy C.
      • Turner K.
      • Mathur A.
      • Hughes M.
      • Kammula U.S.
      • et al.
      Phase 2 trial of single agent Ipilimumab (anti-CTLA-4) for locally advanced or metastatic pancreatic adenocarcinoma.
      ]. In addition, the administration of Ipilimumab in patients with PAC has been associated with increased toxicity [
      • Royal R.E.
      • Levy C.
      • Turner K.
      • Mathur A.
      • Hughes M.
      • Kammula U.S.
      • et al.
      Phase 2 trial of single agent Ipilimumab (anti-CTLA-4) for locally advanced or metastatic pancreatic adenocarcinoma.
      ]. Interestingly, combination with chemotherapy has provided more promising results. Indeed, gemcitabine, a standard treatment for advanced PAC [
      • Burris H.I.
      • Moore M.
      • Jea Andersen
      Improvements in survival and clinical benefit with gemcitabine as first-line therapy for patients with advanced pancreas cancer: a randomized trial.
      ] has demonstrated increased immune response by enhancing naïve T cells activation [
      • Plate J.M.
      • Plate A.E.
      • Shott S.
      • Bograd S.
      • Harris J.E.
      Effect of gemcitabine on immune cells in subjects with adenocarcinoma of the pancreas.
      ]. In a phase Ib clinical trial (NCT01473940) [
      • Mohindra N.A.
      • Kircher S.M.
      • Nimeiri H.S.
      • Benson A.B.
      • Rademaker A.
      • Alonso E.
      • et al.
      Results of the phase Ib study of ipilimumab and gemcitabine for advanced pancreas cancer.
      ,
      • Kalyan A.
      • Kircher S.M.
      • Mohindra N.A.
      • Nimeiri H.S.
      • Maurer V.
      • Rademaker A.
      • et al.
      Ipilimumab and gemcitabine for advanced pancreas cancer: A phase Ib study.
      ], preliminary results using Ipilimumab and gemcitabine showed a median progression-free survival (PFS) of 2.5 months (95% CI 0.8–4.8) and median OS of 8.5 months (95% CI 2.2–10.3). Two out of 11 evaluated patients had partial response (PR) and five patients had stable disease (SD), while the most common toxicities were hematologic [
      • Kalyan A.
      • Kircher S.M.
      • Mohindra N.A.
      • Nimeiri H.S.
      • Maurer V.
      • Rademaker A.
      • et al.
      Ipilimumab and gemcitabine for advanced pancreas cancer: A phase Ib study.
      ]. Another ongoing clinical study, NCT01928394, is also evaluating Ipilimumab in combination with the anti-PD-1 agent Nivolumab; however, results have not been presented so far [

      A Study of Nivolumab by Itself or Nivolumab Combined With Ipilimumab in Patients With Advanced or Metastatic Solid Tumors. https://clinicaltrials.gov/show/NCT01928394.

      ].
      Tremelimumab, another anti-CTLA-4 inhibitor is a human IgG2 mAb [

      Tremelimumab. Drugs R D. 2010; 10: 123–32.

      ] that was evaluated as monotherapy in a phase II open label study (NCT02527434) [

      AstraZeneca. Study of Tremelimumab in Patients With Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT02527434; 2015.

      ]. In the cohort of patients with metastatic PAC, eligible patients had tumor progression following treatment with a 5-FU of gemcitabine regimen. Tremelimumab yielded disappointing results with 18 out of 20 patients demonstrating progressive disease and a poor median OS of 4 months (95% CI 2.83–5.42). On the other hand, Aglietta et al. evaluated the efficacy of Tremelimumab in combination with gemcitabine in a phase I trial (NCT00556023) [
      • Aglietta M.
      • Barone C.
      • Sawyer M.B.
      • Moore M.J.
      • Miller W.H.
      • Bagalà C.
      • et al.
      A phase I dose escalation trial of tremelimumab (CP-675,206) in combination with gemcitabine in chemotherapy-naive patients with metastatic pancreatic cancer.
      ]. Tumor response was evaluable in 28 out of 34 patients and median OS was 7.4 months (95% CI 5.8–9.4). Two patients achieved PR and 7 showed SD for more than 10 weeks [
      • Aglietta M.
      • Barone C.
      • Sawyer M.B.
      • Moore M.J.
      • Miller W.H.
      • Bagalà C.
      • et al.
      A phase I dose escalation trial of tremelimumab (CP-675,206) in combination with gemcitabine in chemotherapy-naive patients with metastatic pancreatic cancer.
      ] with tolerable toxicity.
      Combination of Tremelimumab with the anti–PD-L1 agent Durvalumab was evaluated in a phase II (part A) clinical trial as second line treatment after failure of 5-FU or gemcitabine-based chemotherapy. Efficacy analysis demonstrated an objective response rate (ORR) of 3.1% (95% CI 0.08–16.22) with the combination, while no patients responded to Durvalumab monotherapy [
      • O'Reilly E.M.
      • Oh D.Y.
      • Dhani N.
      • Renouf D.J.
      • Lee M.A.
      • Sun W.
      • et al.
      Durvalumab With or Without Tremelimumab for Patients With Metastatic Pancreatic Ductal Adenocarcinoma: A Phase 2 Randomized Clinical Trial.
      ]. The desired threshold efficacy (10%) was not met in part A of the study; thus, part B of the study, that was planned as a randomized or non-randomized clinical trial based on the results of part A was not conducted.
      Pembrolizumab; Immunohistochemical analysis in PAC has revealed that PD-L1 expression correlates with worse OS [
      • Nomi T.
      • Sho M.
      • Akahori T.
      • Hamada K.
      • Kubo A.
      • Kanehiro H.
      • et al.
      Clinical significance and therapeutic potential of the programmed death-1 ligand/programmed death-1 pathway in human pancreatic cancer.
      ]. Gemcitabine and paclitaxel, a standard first line chemotherapy regimen for metastatic PAC have been previously reported to dispose immunomodulatory properties [
      • Duffy A.G.
      • Greten T.F.
      Immunological off-target effects of standard treatments in gastrointestinal cancers.
      ]. A phase Ib/II study (NCT02331251) was performed to evaluate the safety and efficacy of PD-1 inhibitor, Pembrolizumab, in combination with gemcitabine and nab-paclitaxel chemotherapy [
      • Weiss G.J.
      • Blaydorn L.
      • Beck J.
      • Bornemann-Kolatzki K.
      • Urnovitz H.
      • Schutz E.
      • et al.
      Correction to: Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.
      ]. PFS and OS were evaluated at 9.1 and 15.0 months, respectively, showing a strong positive correlation with PFS and OS (r = 0.777), while grade 3 events occurred only in 53% of patients [
      • Weiss G.J.
      • Blaydorn L.
      • Beck J.
      • Bornemann-Kolatzki K.
      • Urnovitz H.
      • Schutz E.
      • et al.
      Correction to: Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.
      ,
      • Weiss G.J.
      • Blaydorn L.
      • Beck J.
      • Bornemann-Kolatzki K.
      • Urnovitz H.
      • Schutz E.
      • et al.
      Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.
      ].
      Atezolizumab; A phase I dose-escalating study of Atezolizumab, an engineered IgG1 mAb targeting PD-L1, showed tolerability at doses up to 20 mg/kg every 3 weeks [
      • Mizugaki H.
      • Yamamoto N.
      • Murakami H.
      • Kenmotsu H.
      • Fujiwara Y.
      • Ishida Y.
      • et al.
      Phase I dose-finding study of monotherapy with atezolizumab, an engineered immunoglobulin monoclonal antibody targeting PD-L1, in Japanese patients with advanced solid tumors.
      ]. A phase I/II trial (NCT03829501) is currently ongoing [

      Safety and Efficacy of KY1044 and Atezolizumab in Advanced Cancer. https://clinicaltrials.gov/show/NCT03829501.

      ].

      Vaccine therapy in pancreatic adenocarcinoma

      In addition to therapeutic protocols using checkpoint inhibitors, a number of vaccine-based studies have been also conducted in PAC [
      • Butterfield L.H.
      Cancer vaccines.
      ]. Therapeutic cancer vaccines (Table 2) include whole-cell vaccines, Dendritic Cell (DC), DNA and peptide vaccines that provoke the presentation of immunogenic cancer antigens to the immune system, resulting in activation of cancer antigen-specific CTLs in vivo [
      • Vacchelli E.
      • Martins I.
      • Eggermont A.
      • Fridman W.H.
      • Galon J.
      • Sautes-Fridman C.
      • et al.
      Trial watch: Peptide vaccines in cancer therapy.
      ] and subsequent anti-cancer immune response.
      Table 2Vaccine therapy.
      InterventionStrategyCancer stageClinical phase, IdentifierOutcomes: Median Overall survival (Months)Bibliography
      GVAX, ChemoradiationWhole-cell vaccine, Cytotoxic drugsStage I, II or III pancreatic cancerPhase IEffective anti-tumor immunity
      • Jaffee E.M.
      • Hruban R.H.
      • Biedrzycki B.
      • Laheru D.
      • Schepers K.
      • Sauter P.R.
      • et al.
      Novel allogeneic granulocyte-macrophage colony-stimulating factor-secreting tumor vaccine for pancreatic cancer: a phase I trial of safety and immune activation.
      GVAX, 5-FU, ChemoradiationWhole-cell vaccine, Cytotoxic drugsResected stage I or II pancreatic adenocarcinomaPhase II, NCT0008438324.8 (95% CI, 21.2–31.6), combination therapy 20.3 (95% CI, 18.0–23.9), 5-FU/chemoradiation
      • Lutz E.
      • Yeo C.J.
      • Lillemoe K.D.
      • Biedrzycki B.
      • Kobrin B.
      • Herman J.
      • et al.
      A lethally irradiated allogeneic granulocyte-macrophage colony stimulating factor-secreting tumor vaccine for pancreatic adenocarcinoma. A Phase II trial of safety, efficacy, and immune activation.
      GVAX, Cy, CRS-207Whole-cell vaccine, Cytotoxic drugs, Listeria vaccineMetastatic pancreatic adenocarcinomaPhase 2a, NCT014170006.28 (95% CI, 4.47–9.40), combination therapy

      4.07 (95% CI, 3.32–5.42), GVAX/Cy
      • Whiting C.
      • Lutz E.
      • Nair N.
      • Chang S.
      • Lemmens E.
      • Chen S.-Y.
      • et al.
      Phase II, randomized study of GVAX pancreas and CRS-207 immunotherapy in patients with metastatic pancreatic cancer: Clinical update on long term survival and biomarker correlates to overall survival.
      GVAX, Cy, CRS-207Whole-cell vaccine, Cytotoxic drugs, Listeria vaccinePreviously treated metastatic pancreatic adenocarcinomaPhase IIb, NCT020042623.7 (95% CI, 2.9–5.3), combination therapy

      5.4 (95% CI, 4.2–6.4), CRS-207 alone

      4.6 (95% CI, 4.2–5.7), chemotherapy
      • Le D.T.
      • Picozzi V.J.
      • Ko A.H.
      • Wainberg Z.A.
      • Kindler H.
      • Wang-Gillam A.
      • et al.
      Results from a Phase IIb, Randomized, Multicenter Study of GVAX Pancreas and CRS-207 Compared with Chemotherapy in Adults with Previously Treated Metastatic Pancreatic Adenocarcinoma (ECLIPSE Study).
      KIF20A-66Peptide vaccineMetastatic pancreatic adenocarcinomaPhase I/II, UMIN0000049194.7 ± 0.8, KIF20A-66 vaccine

      2.7 ± 1.1, Best supportive care
      • Asahara S.
      • Takeda K.
      • Yamao K.
      • Maguchi H.
      • Yamaue H.
      Phase I/II clinical trial using HLA-A24-restricted peptide vaccine derived from KIF20A for patients with advanced pancreatic cancer.
      SVN-2B, IFA, IFNaPeptide vaccine, Immunopotentiator CytokinesSurvivin-positive, unresectable advanced tumorUMIN000000905greater than 50% of the patients had positive clinical and immunological responses
      • Kameshima H.
      • Tsuruma T.
      • Kutomi G.
      • Shima H.
      • Iwayama Y.
      • Kimura Y.
      • et al.
      Immunotherapeutic benefit of alpha-interferon (IFNalpha) in survivin2B-derived peptide vaccination for advanced pancreatic cancer patients.
      KIF20A, VEGFR1, VEGFR2, GemcitabinePeptide vaccine, Peptide vaccine, Peptide vaccine, Cytotoxic drugsAdvanced pancreatic cancerPhase II, UMIN0000080829.0 months, HLA‐matched

      10.0 months, HLA‐unmatched
      • Suzuki N.
      • Hazama S.
      • Iguchi H.
      • Uesugi K.
      • Tanaka H.
      • Hirakawa K.
      • et al.
      Phase II clinical trial of peptide cocktail therapy for patients with advanced pancreatic cancer: VENUS-PC study.
      Algenpantucel-LMulti-peptide vaccineSurgically Resected Pancreatic CancerPhase 2, NCT0056938712-month overall survival was 86%

      Hardacre JM, Mulcahy M, Small W, Talamonti M, Obel J, Krishnamurthi S, et al. Addition of algenpantucel-L immunotherapy to standard adjuvant therapy for pancreatic cancer: a phase 2 study. J Gastrointest Surg 2013; 17: 94–100; discussion p -1.

      Algenpantucel-L, Folfrinox, Gemcitabine, 5-FUMulti-peptide vaccine, Cytotoxic drugsUnresectable (stage III)Phase II, NCT02405585Study terminated

      No results posted
      • McCormick K.A.
      • Coveler A.L.
      • Rossi G.R.
      • Vahanian N.N.
      • Link C.
      • Chiorean E.G.
      Pancreatic cancer: Update on immunotherapies and algenpantucel-L.
      Algenpantucel-L, Gemcitabine, 5-FUMulti-peptide vaccine, Cytotoxic drugsSurgically resected pancreatic cancerPhase III, NCT01072981Completed

      No results posted
      • McCormick K.A.
      • Coveler A.L.
      • Rossi G.R.
      • Vahanian N.N.
      • Link C.
      • Chiorean E.G.
      Pancreatic cancer: Update on immunotherapies and algenpantucel-L.
      Algenpantucel-L

      Folfrinox, Gemcitabine, Nab-paclitaxel, Capecitabine, 5-FU
      Multi-peptide vaccine, Cytotoxic drugsResectable (stage II) and Unresectable (stage III)Phase III, NCT01836432Study terminated

      No results posted
      • McCormick K.A.
      • Coveler A.L.
      • Rossi G.R.
      • Vahanian N.N.
      • Link C.
      • Chiorean E.G.
      Pancreatic cancer: Update on immunotherapies and algenpantucel-L.
      MUC1, HLA-A2, ICAM-1, LFA-3, GM-CSFVaccinia virus-tumor antigens, Costimulatory moleculesAdvanced pancreatic cancerPhase I15.3 months, anti CEA/MUC-1 positive

      3.9 months, anti CEA/MUC-1 negative
      • Kaufman H.L.
      • Kim-Schulze S.
      • Manson K.
      • DeRaffele G.
      • Mitcham J.
      • Seo K.S.
      • et al.
      Poxvirus-based vaccine therapy for patients with advanced pancreatic cancer.
      MUC1 pulsed DC-CIKDC-CIK vaccinationSurgically resected pancreatic cancerPhase I /II26 (95% CI, 13–69)
      • Lepisto A.J.
      • Moser A.J.
      • Zeh H.
      • Lee K.
      • Bartlett D.
      • McKolanis J.R.
      • et al.
      A phase I/II study of a MUC1 peptide pulsed autologous dendritic cell vaccine as adjuvant therapy in patients with resected pancreatic and biliary tumors.
      w/ Poly-ICLC plus peptide- pulsed DC-CIKImmunostimulant

      DC-CIK vaccination
      Metastatic, unresectable pancreatic cancerPhase I

      NCT01410968
      7.7 months
      • Mehrotra S.
      • Britten C.D.
      • Chin S.
      • Garrett-Mayer E.
      • Cloud C.A.
      • Li M.
      • et al.
      Vaccination with poly(IC:LC) and peptide-pulsed autologous dendritic cells in patients with pancreatic cancer.
      DC-CIK, Chemotherapy S-1DC-CIK vaccination, Cytotoxic drugsMetastatic, unresectable pancreatic cancerPhase I /II, NCT017815207 months; DC-CIK, Chemotherapy S-1

      4.2 months; DC-CIK alone

      4.7 months; chemotherapy S-1 alone

      1.73 months; supportive care only
      • Jiang N.
      • Qiao G.
      • Wang X.
      • Morse M.A.
      • Gwin W.R.
      • Zhou L.
      • et al.
      Dendritic Cell/Cytokine-Induced Killer Cell Immunotherapy Combined with S-1 in Patients with Advanced Pancreatic Cancer: A Prospective Study.
      K-Ras vaccine, GM-CSFPeptide vaccine, Costimulatory moleculeSurgically resected and advanced disease patientsPhase I/II25.6 (95% CI, 10–39), resected 10.2 (95% CI, 3–28), unresectable
      • Gjertsen M.K.
      • Buanes T.
      • Rosseland A.R.
      • Bakka A.
      • Gladhaug I.
      • Soreide O.
      • et al.
      Intradermal ras peptide vaccination with granulocyte-macrophage colony-stimulating factor as adjuvant: Clinical and immunological responses in patients with pancreatic adenocarcinoma.
      Ras-peptide, GM-CSFPeptide vaccine, Costimulatory moleculesKRAS mutant pancreatic cancer20.3 (95% CI, 11.6–45.3)
      • Abou-Alfa G.K.
      • Chapman P.B.
      • Feilchenfeldt J.
      • Brennan M.F.
      • Capanu M.
      • Gansukh B.
      • et al.
      Targeting mutated K-ras in pancreatic adenocarcinoma using an adjuvant vaccine.
      GI-4000, GemcitabineMultipartite vaccine, Cytotoxic drugsKRAS mutant pancreatic cancerPhase II19.8 months; GI-4000, gemcitabine

      14.8 months; Placebo, gemcitabine
      • Muscarella P.
      • Wilfong L.S.
      • Ross S.B.
      • Richards D.A.
      • Raynov J.
      • Fisher W.E.
      • et al.
      A randomized, placebo-controlled, double blind, multicenter phase II adjuvant trial of the efficacy, immunogenicity, and safety of GI-4000 plus gem versus gem alone in patients with resected pancreas cancer with activating RAS mutations/survival and immunology analysis of the R1 subgroup.
      GV1001, GM-CSFPeptide vaccine, Costimulatory moleculesNon-Resectable pancreatic cancerPhase I/II7.2 months; Responders

      2.9 months; Non responders
      • Bernhardt S.L.
      • Gjertsen M.K.
      • Trachsel S.
      • Moller M.
      • Eriksen J.A.
      • Meo M.
      • et al.
      Telomerase peptide vaccination of patients with non-resectable pancreatic cancer: A dose escalating phase I/II study.
      GV1001, Gemcitabine, CapecitabinePeptide vaccine, Cytotoxic drugsMetastatic pancreatic cancerPhase III6,9 (95% CI, 6,4–7,6); treated group

      7,9 (95% CI, 7,1–8,8); chemotherapy alone
      • Middleton G.
      • Silcocks P.
      • Cox T.
      • Valle J.
      • Wadsley J.
      • Propper D.
      • et al.
      Gemcitabine and capecitabine with or without telomerase peptide vaccine GV1001 in patients with locally advanced or metastatic pancreatic cancer (TeloVac): an open-label, randomised, phase 3 trial.
      Cy: Cyclophosphamide; 5-FU: Fluorouracil; CRS-207: Live, attenuated Listeria monocytogenes expressing mesothelin; IFA: Freund’s adjuvant; IFNa: a-interferon; VEGFR: vascular endothelial growth factor; MUC1: Mucin 1; ICAM: Intercellular Adhesion Molecule; LFA-3: lymphocyte function-associated antigen; GM-CSF: granulocyte-macrophage colony–stimulating factor; DC-CIK: dendritic and cytokine-induced killer cells.
      GVAX is an irradiated allogeneic whole tumor cell vaccine in which PAC cells are engineered to express granulocyte-macrophage colony-stimulating factor (GM-CSF) [
      • Rosenberg A.
      • Mahalingam D.
      Immunotherapy in pancreatic adenocarcinoma-overcoming barriers to response.
      ]. This procedure leads to stimulation of APC antigen uptake and T cell priming [
      • Laheru D.
      • Biedrzycki B.
      • Jaffee E.M.
      Development of a cytokine-modified allogeneic whole cell pancreatic cancer vaccine.
      ]. A phase I study evaluated GVAX after resection and prior to adjuvant chemoradiotherapy in patients with localized PAC. It was shown that GVAX was tolerable and when administered at high doses, it was effective in promoting the development of anti-tumor immunity, as measured by increased delayed-type hypersensitivity responses against autologous tumors after vaccination [
      • Jaffee E.M.
      • Hruban R.H.
      • Biedrzycki B.
      • Laheru D.
      • Schepers K.
      • Sauter P.R.
      • et al.
      Novel allogeneic granulocyte-macrophage colony-stimulating factor-secreting tumor vaccine for pancreatic cancer: a phase I trial of safety and immune activation.
      ]. In addition, in a phase II study (NCT00084383) [
      • Lutz E.
      • Yeo C.J.
      • Lillemoe K.D.
      • Biedrzycki B.
      • Kobrin B.
      • Herman J.
      • et al.
      A lethally irradiated allogeneic granulocyte-macrophage colony stimulating factor-secreting tumor vaccine for pancreatic adenocarcinoma. A Phase II trial of safety, efficacy, and immune activation.
      ] that included 60 patients treated with adjuvant 5-FU based chemoradiotherapy, GVAX was administered after surgery and following adjuvant treatment in patients who remained disease free. Median DFS was 17.3 months and median OS was 24.8 months (95% CI 21.2–31.6) that compares favorably with historical controls for resected PAC [
      • Lutz E.
      • Yeo C.J.
      • Lillemoe K.D.
      • Biedrzycki B.
      • Kobrin B.
      • Herman J.
      • et al.
      A lethally irradiated allogeneic granulocyte-macrophage colony stimulating factor-secreting tumor vaccine for pancreatic adenocarcinoma. A Phase II trial of safety, efficacy, and immune activation.
      ].
      A phase IIa randomized study (NCT01417000) assessed the efficacy of CRS-207, a live-attenuated mesothelin-expressing Listeria monocytogenes vaccine that stimulates innate and adaptive immunity in combination with low dose cyclophosphamide (Cy) and GVAX as compared to Cy and GVAX alone in patients with previously treated PAC. Low dose Cy was used to inhibit T regulatory cells (Tregs). Triple combination therapy demonstrated longer OS (6.1 months vs. 3.9 months, HR 0.54, one-sided P = 0.02) with minimal toxicity and enhanced mesothelin-specific CD8 cytotoxic cells correlated with improved OS irrespective of treatment arm [
      • Whiting C.
      • Lutz E.
      • Nair N.
      • Chang S.
      • Lemmens E.
      • Chen S.-Y.
      • et al.
      Phase II, randomized study of GVAX pancreas and CRS-207 immunotherapy in patients with metastatic pancreatic cancer: Clinical update on long term survival and biomarker correlates to overall survival.
      ]. However, Cy/GVAX and CRS-207 combination failed to improve survival over chemotherapy in patients with previously treated PAC in a phase IIb trial [
      • Le D.T.
      • Picozzi V.J.
      • Ko A.H.
      • Wainberg Z.A.
      • Kindler H.
      • Wang-Gillam A.
      • et al.
      Results from a Phase IIb, Randomized, Multicenter Study of GVAX Pancreas and CRS-207 Compared with Chemotherapy in Adults with Previously Treated Metastatic Pancreatic Adenocarcinoma (ECLIPSE Study).
      ].
      KIF20A-66 and survivin-2B 8088 (SVN-2B) peptides. These are Human Leukocyte Antigen (HLA)-A24-restricted cytotoxic T cell epitopes derived from the TAAs kinesin family member 20A (KIF20A) and survivin respectively [
      • Osawa R.
      • Tsunoda T.
      • Yoshimura S.
      • Watanabe T.
      • Miyazawa M.
      • Tani M.
      • et al.
      Identification of HLA-A24-restricted novel T Cell epitope peptides derived from P-cadherin and kinesin family member 20A.
      ,
      • Kobayashi J.
      • Torigoe T.
      • Hirohashi Y.
      • Idenoue S.
      • Miyazaki A.
      • Yamaguchi A.
      • et al.
      Comparative study on the immunogenicity between an HLA-A24-restricted cytotoxic T-cell epitope derived from survivin and that from its splice variant survivin-2B in oral cancer patients.
      ], which are up-regulated in PAC [
      • Asahara S.
      • Takeda K.
      • Yamao K.
      • Maguchi H.
      • Yamaue H.
      Phase I/II clinical trial using HLA-A24-restricted peptide vaccine derived from KIF20A for patients with advanced pancreatic cancer.
      ]. KIF20A-66 is an epitope peptide developed as a cancer vaccine [
      • Asahara S.
      • Takeda K.
      • Yamao K.
      • Maguchi H.
      • Yamaue H.
      Phase I/II clinical trial using HLA-A24-restricted peptide vaccine derived from KIF20A for patients with advanced pancreatic cancer.
      ]. A phase I/II clinical trial [
      • Asahara S.
      • Takeda K.
      • Yamao K.
      • Maguchi H.
      • Yamaue H.
      Phase I/II clinical trial using HLA-A24-restricted peptide vaccine derived from KIF20A for patients with advanced pancreatic cancer.
      ] showed that patients with metastatic PAC and an HLA-A*2402-positive status receiving KIF20A-66 peptide as second line treatment, following failure of gemcitabine chemotherapy, had better prognosis compared to control group receiving best supportive care. Objective tumor shrinkage was observed in 8 out of 29 patients in the study, while the median OS was fairly improved 4.7 ± 0.8 compared to 2.7 ± 1.1 months (P = 0.0468) for vaccine and best supportive care arm respectively (Table 2). PFS of the patients with peptide vaccine was 1.8 months [
      • Asahara S.
      • Takeda K.
      • Yamao K.
      • Maguchi H.
      • Yamaue H.
      Phase I/II clinical trial using HLA-A24-restricted peptide vaccine derived from KIF20A for patients with advanced pancreatic cancer.
      ]. On the other hand, SVN-2B is an HLA‐A24‐restricted peptide that has been investigated since 2003 in many cancers with modest results. Subsequently, it was evaluated as a part of a vaccination protocol in combination with incomplete Freund’s adjuvant (IFA), a solution of antigen emulsified (usually M. tuberculosis) and interferon-a (IFN-a) that were both used as immunopotentiators. In a study that included 6 patients with PAC that were HLA-A*2402 positive, it was demonstrated that 50% of patients demonstrated positive clinical and immunological responses following treatment with the combination [
      • Kameshima H.
      • Tsuruma T.
      • Kutomi G.
      • Shima H.
      • Iwayama Y.
      • Kimura Y.
      • et al.
      Immunotherapeutic benefit of alpha-interferon (IFNalpha) in survivin2B-derived peptide vaccination for advanced pancreatic cancer patients.
      ].
      KIF20A-derived peptide has been also investigated in combination with two anti-angiogenic cancer vaccines targeting vascular endothelial growth factor receptor 1 (VEGFR1) and VEGFR2 and gemcitabine in a phase II clinical trial in patients with chemotherapy naïve PAC. It was found that patients in the HLA‐A*2402‐matched group that showed peptide‐specific CTL induction had better prognosis and better OS rate (P = 0.017) [
      • Suzuki N.
      • Hazama S.
      • Iguchi H.
      • Uesugi K.
      • Tanaka H.
      • Hirakawa K.
      • et al.
      Phase II clinical trial of peptide cocktail therapy for patients with advanced pancreatic cancer: VENUS-PC study.
      ]. The median DFS was 15.8 months (95% CI 11.1–20.6) compared to 12.0 months (95% CI 5.29–22.3) for the control arm; however, no statistically significant difference was observed (P = 0.504) [
      • Miyazawa M.
      • Katsuda M.
      • Maguchi H.
      • Katanuma A.
      • Ishii H.
      • Ozaka M.
      • et al.
      Phase II clinical trial using novel peptide cocktail vaccine as a postoperative adjuvant treatment for surgically resected pancreatic cancer patients.
      ].
      Algenpantucel-L is a whole-cell vaccine that consists of 2 irradiated allogeneic pancreatic cell lines (HAPa-1 and HAPa-2) genetically engineered by retrovirus transduction to express the murine enzyme (1,3)-galactosyltransferase (αGT), which is responsible for hyperacute rejection, the primary barrier to xenotransplantation [

      Hardacre JM, Mulcahy M, Small W, Talamonti M, Obel J, Krishnamurthi S, et al. Addition of algenpantucel-L immunotherapy to standard adjuvant therapy for pancreatic cancer: a phase 2 study. J Gastrointest Surg 2013; 17: 94–100; discussion p -1.

      ]. A multi-institutional, open-label, dose-escalating, phase II trial evaluating the use of algenpantucel-L immunotherapy in addition to gemcitabine and 5-FU chemoradiotherapy (RTOG 9704 protocol) in the adjuvant setting of patients with resected PAC, achieved 1-year DFS of 63% and 86% OS compared to ~45% and 65%, respectively in historical controls [

      Hardacre JM, Mulcahy M, Small W, Talamonti M, Obel J, Krishnamurthi S, et al. Addition of algenpantucel-L immunotherapy to standard adjuvant therapy for pancreatic cancer: a phase 2 study. J Gastrointest Surg 2013; 17: 94–100; discussion p -1.

      ]. Ongoing clinical trials evaluate algenpantucel-L in patients with borderline resectable and locally advanced unresectable PAC in combination with chemotherapy and chemoradiotherapy (NCT01836432, NCT02405585 and NCT01072981) [
      • McCormick K.A.
      • Coveler A.L.
      • Rossi G.R.
      • Vahanian N.N.
      • Link C.
      • Chiorean E.G.
      Pancreatic cancer: Update on immunotherapies and algenpantucel-L.
      ].
      Mucin 1 (MUC-1) is a type I transmembrane protein with extensive O-linked glycosylation that plays a pivotal role in normal cell signal transduction and oncogenic signaling to increase invasion, angiogenesis and metastasis [
      • Behrens M.E.
      • Grandgenett P.M.
      • Bailey J.M.
      • Singh P.K.
      • Yi C.H.
      • Yu F.
      • et al.
      The reactive tumor microenvironment: MUC1 signaling directly reprograms transcription of CTGF.
      ]. It is overexpressed in cancer cells of solid tumors, including PAC [
      • Qu C.F.
      • Li Y.
      • Song Y.J.
      • Rizvi S.M.
      • Raja C.
      • Zhang D.
      • et al.
      MUC1 expression in primary and metastatic pancreatic cancer cells for in vitro treatment by (213)Bi-C595 radioimmunoconjugate.
      ]. A phase I study using MUC-1 peptide in PAC has shown that mucin vaccination is safe and might enhance responses to tumor antigens [
      • Ramanathan R.K.
      • Lee K.M.
      • McKolanis J.
      • Hitbold E.
      • Schraut W.
      • Moser A.J.
      • et al.
      Phase I study of a MUC1 vaccine composed of different doses of MUC1 peptide with SB-AS2 adjuvant in resected and locally advanced pancreatic cancer.
      ]. Moreover, in a phase I study, patients with advanced PAC were treated with a vaccination regimen consisting of vaccinia virus expressing carcinoembryonic antigen (CEA) and mucin-1 (MUC-1) with three costimulatory molecules B7.1, ICAM-1 and LFA-3 and poxvirus, expressing the same antigens and costimulatory molecules, combined with GM-CSF [
      • Kaufman H.L.
      • Kim-Schulze S.
      • Manson K.
      • DeRaffele G.
      • Mitcham J.
      • Seo K.S.
      • et al.
      Poxvirus-based vaccine therapy for patients with advanced pancreatic cancer.
      ]. It was demonstrated that patients who developed a vaccine-specific T cell response had a significantly improved OS than non-responders (15.3 months vs. 3.9 months, respectively) [
      • Kaufman H.L.
      • Kim-Schulze S.
      • Manson K.
      • DeRaffele G.
      • Mitcham J.
      • Seo K.S.
      • et al.
      Poxvirus-based vaccine therapy for patients with advanced pancreatic cancer.
      ]. On the other hand, a phase I/II study of a MUC1 peptide-loaded DC vaccine as adjuvant therapy reported that the vaccine was well tolerated and no toxicity was observed. Vaccinated patients have been followed for over four years and four out of twelve patients are alive, all without evidence of recurrence [
      • Lepisto A.J.
      • Moser A.J.
      • Zeh H.
      • Lee K.
      • Bartlett D.
      • McKolanis J.R.
      • et al.
      A phase I/II study of a MUC1 peptide pulsed autologous dendritic cell vaccine as adjuvant therapy in patients with resected pancreatic and biliary tumors.
      ].
      Dendritic cell vaccine; DCs are APCs that have the capacity to stimulate naïve T cells and enhance anti-tumor immune response [
      • Palucka K.
      • Ueno H.
      • Fay J.
      • Banchereau J.
      Dendritic cells and immunity against cancer.
      ]. DC vaccines are produced by culturing ex vivo DCs that have been derived from patients with a specific antigen; after maturation and activation, DCs cells are injected back into the patient. In a recent study, researchers re-administered isolated autologous DCs from the peripheral blood of HLA-A2 positive patients. DCs were pulsed with three distinct A2-restricted peptides: 1) human telomerase reverse transcriptase (hTERT, TERT572Y), 2) carcinoembryonic antigen (CEA; Cap1-6D), and 3) survivin (SRV.A2). Patients also received intramuscular administration of Poly-ICLC [
      • Mehrotra S.
      • Britten C.D.
      • Chin S.
      • Garrett-Mayer E.
      • Cloud C.A.
      • Li M.
      • et al.
      Vaccination with poly(IC:LC) and peptide-pulsed autologous dendritic cells in patients with pancreatic cancer.
      ]. Treatment was well tolerated with the most common side effects being fatigue and/or flu-like symptoms; MHC class I–tetramer analysis revealed effective generation of antigen-specific T cells in 3 patients having SD [
      • Mehrotra S.
      • Britten C.D.
      • Chin S.
      • Garrett-Mayer E.
      • Cloud C.A.
      • Li M.
      • et al.
      Vaccination with poly(IC:LC) and peptide-pulsed autologous dendritic cells in patients with pancreatic cancer.
      ]. DCs can also be pulsed with other synthetic peptides derived from PAC-associated antigens, such as WT1, showing promising results in early studies [
      • Kimura Y.
      • Tsukada J.
      • Tomoda T.
      • Takahashi H.
      • Imai K.
      • Shimamura K.
      • et al.
      Clinical and immunologic evaluation of dendritic cell-based immunotherapy in combination with gemcitabine and/or S-1 in patients with advanced pancreatic carcinoma.
      ].
      K-Ras vaccine; Mutations in KRASoncogene are found in ~ 95% of patients with PAC [

      Zeitouni D, Pylayeva-Gupta Y, Der CJ, Bryant KL. KRAS Mutant Pancreatic Cancer: No Lone Path to an Effective Treatment. Cancers (Basel). 2016; 8.

      ]. An early study published in 1995 showed that in two out of five patients with PAC and a KRAS mutation that were vaccinated with a synthetic Ras peptide corresponding to the K-RAS mutation in the tumor tissue, a transient Ras-specific T cell response was induced [
      • Gjertsen M.K.
      • Bakka A.
      • Breivik J.
      • Saeterdal I.
      • Solheim B.G.
      • Soreide O.
      • et al.
      Vaccination with mutant ras peptides and induction of T-cell responsiveness in pancreatic carcinoma patients carrying the corresponding RAS mutation.
      ]. In an attempt to enhance the immune response, a phase I/II trial evaluated the efficacy of the combination of synthetic mutant Ras peptides with GM-CSF in patients with resected and advanced PAC [
      • Gjertsen M.K.
      • Buanes T.
      • Rosseland A.R.
      • Bakka A.
      • Gladhaug I.
      • Soreide O.
      • et al.
      Intradermal ras peptide vaccination with granulocyte-macrophage colony-stimulating factor as adjuvant: Clinical and immunological responses in patients with pancreatic adenocarcinoma.
      ]. Peptide-specific immunity was induced in 58% of patients; interestingly, patients with advanced disease that responded to the peptide vaccine showed an improved OS of 4.9 months compared with 2 months for non-responders. Regarding patients with localized disease, patients with advanced disease have dismal prognosis [
      • Gjertsen M.K.
      • Buanes T.
      • Rosseland A.R.
      • Bakka A.
      • Gladhaug I.
      • Soreide O.
      • et al.
      Intradermal ras peptide vaccination with granulocyte-macrophage colony-stimulating factor as adjuvant: Clinical and immunological responses in patients with pancreatic adenocarcinoma.
      ]. Long-term follow-up of patients with resected PAC reported a median OS of 27.5 months for all patients and 28 months for immune responders [
      • Weden S.
      • Klemp M.
      • Gladhaug I.P.
      • Moller M.
      • Eriksen J.A.
      • Gaudernack G.
      • et al.
      Long-term follow-up of patients with resected pancreatic cancer following vaccination against mutant K-ras.
      ]. Similarly, in a pilot study, the vaccine against mutant KRAS was found to be safe, induced specific immune responses and produced an OS of 44.4 months [
      • Toubaji A.
      • Achtar M.
      • Provenzano M.
      • Herrin V.E.
      • Behrens R.
      • Hamilton M.
      • et al.
      Pilot study of mutant ras peptide-based vaccine as an adjuvant treatment in pancreatic and colorectal cancers.
      ]. However, in a more recent study that included patients with localized PAC that also received adjuvant chemotherapy, a combination of Ras-peptide vaccine with GM-CSF yielded disappointing results, with only 1 out of 9 patients showing immune response, and a median OS of 20.3 months [
      • Abou-Alfa G.K.
      • Chapman P.B.
      • Feilchenfeldt J.
      • Brennan M.F.
      • Capanu M.
      • Gansukh B.
      • et al.
      Targeting mutated K-ras in pancreatic adenocarcinoma using an adjuvant vaccine.
      ]. Nevertheless, administration of adjuvant therapy that offers survival benefit does not allow to evaluate the specific contribution of KRAS vaccine.
      GI-4000 is a whole heat-killed recombinant Saccharomyces cerevisiae yeast vaccine that expresses mutated human Ras proteins [
      • Cohn A.
      • Morse M.A.
      • O'Neil B.
      • Whiting S.
      • Coeshott C.
      • Ferraro J.
      • et al.
      Whole Recombinant Saccharomyces cerevisiae Yeast Expressing Ras Mutations as Treatment for Patients With Solid Tumors Bearing Ras Mutations: Results From a Phase 1 Trial.
      ]. In a randomized phase II study, the combination of GI-4000 and gemcitabine was evaluated as adjuvant therapy in patients with RAS mutant PAC. In a preliminary report, data from patients with R1 disease were analyzed. It was shown that combination therapy offered a 3-month advantage in median OS compared to gemcitabine monotherapy [
      • Muscarella P.
      • Wilfong L.S.
      • Ross S.B.
      • Richards D.A.
      • Raynov J.
      • Fisher W.E.
      • et al.
      A randomized, placebo-controlled, double blind, multicenter phase II adjuvant trial of the efficacy, immunogenicity, and safety of GI-4000 plus gem versus gem alone in patients with resected pancreas cancer with activating RAS mutations/survival and immunology analysis of the R1 subgroup.
      ]. Moreover, the GI-4000 group showed a significantly higher rate of mutation specific T cell response; 47% compared to 8% for the control group [
      • Muscarella P.
      • Wilfong L.S.
      • Ross S.B.
      • Richards D.A.
      • Raynov J.
      • Fisher W.E.
      • et al.
      A randomized, placebo-controlled, double blind, multicenter phase II adjuvant trial of the efficacy, immunogenicity, and safety of GI-4000 plus gem versus gem alone in patients with resected pancreas cancer with activating RAS mutations/survival and immunology analysis of the R1 subgroup.
      ].
      GV1001 vaccine; consists of 16 amino acids, fragments of the hTERT protein found in a large proportion of PAC cells [
      • Suehara N.
      • Mizumoto K.
      • Muta T.
      • Tominaga Y.
      • Shimura H.
      • Kitajima S.
      • et al.
      Telomerase elevation in pancreatic ductal carcinoma compared to nonmalignant pathological states.
      ]. In a phase I/II trial conducted in patients with unresectable disease, GV1001 in combination with GM-CSF was tolerable and elicited an immune response in 63% of the patients, with a median OS of 7.2 months for immune responders compared to 2.9 months for non-immune responders [
      • Bernhardt S.L.
      • Gjertsen M.K.
      • Trachsel S.
      • Moller M.
      • Eriksen J.A.
      • Meo M.
      • et al.
      Telomerase peptide vaccination of patients with non-resectable pancreatic cancer: A dose escalating phase I/II study.
      ]. However, a randomized phase III study that included patients with locally advanced or metastatic disease, the combination of GV1001 plus gemcitabine and capecitabine chemotherapy did not improve OS compared to chemotherapy alone [6.9 months (95% CI 6.4–7.6) vs. 7.9 months (95% CI 7.1–8.8), respectively] [
      • Middleton G.
      • Silcocks P.
      • Cox T.
      • Valle J.
      • Wadsley J.
      • Propper D.
      • et al.
      Gemcitabine and capecitabine with or without telomerase peptide vaccine GV1001 in patients with locally advanced or metastatic pancreatic cancer (TeloVac): an open-label, randomised, phase 3 trial.
      ]. Further clinical trials using GV1001 with GM-CSF in patients with locally advanced PAC given in combination with gemcitabine chemotherapy and tadalafil and radiation therapy (NCT01342224) are ongoing; however, no results have been announced yet.
      There are several disadvantages associated with the aforementioned vaccine studies: First, the number of patients included is small. Moreover, there is a long period of recruitment. Additional drawbacks include high drop-out rate because of tumor progression, difficulties in vaccine synthesis and, most importantly, limitations of immune response identification and measurement. Nevertheless, larger studies are needed for further assessment of vaccine efficacy, possibly in combination with chemotherapy.

      Adoptive cell transfer

      ACT refers to harvesting and ex vivo expansion of the patient’s own tumor antigen specific T cells. Following expansion, T cells are re-infused to the patient, aiming at immunity enhancement and improvement of immune response. CAR T cell therapy is the most clinically developed type of ACT. T cells are collected from the patient and are genetically engineered to express CARs on their surface. In preclinical studies on murine models of PAC tumors that expressed CEA transgene, T cells that expressed a CAR specific for CEA were able to reduce PAC tumors [
      • Chmielewski M.
      • Hahn O.
      • Rappl G.
      • Nowak M.
      • Schmidt-Wolf I.H.
      • Hombach A.A.
      • et al.
      T cells that target carcinoembryonic antigen eradicate orthotopic pancreatic carcinomas without inducing autoimmune colitis in mice.
      ] in mice. Adoptive immunotherapy with T cells stimulated by the MUC1-expressing human PAC cell line YPK-1 (MUC1-CTLs) combined with gemcitabine (Table 3) was used as treatment in a total of 43 patients who underwent radical pancreatectomy [
      • Matsui H.
      • Hazama S.
      • Sakamoto K.
      • Shindo Y.
      • Kanekiyo S.
      • Nakashima M.
      • et al.
      Postoperative Adjuvant Therapy for Resectable Pancreatic Cancer With Gemcitabine and Adoptive Immunotherapy.
      ]. Matsui et al. reported a median OS of 14.7 months. During the entire treatment period, no adverse events were observed while the most common grade 3/4 adverse event was leukocytopenia (35%) [
      • Matsui H.
      • Hazama S.
      • Sakamoto K.
      • Shindo Y.
      • Kanekiyo S.
      • Nakashima M.
      • et al.
      Postoperative Adjuvant Therapy for Resectable Pancreatic Cancer With Gemcitabine and Adoptive Immunotherapy.
      ]. Further preclinical studies demonstrate efficacy of CAR T cell immunotherapy in preclinical models of PAC [
      • Watanabe K.
      • Luo Y.
      • Da T.
      • Guedan S.
      • Ruella M.
      • Scholler J.
      • et al.
      Pancreatic cancer therapy with combined mesothelin-redirected chimeric antigen receptor T cells and cytokine-armed oncolytic adenoviruses. JCI.
      ], although few clinical trials using CARs have been performed in PAC (NCT02465983, NCT01583686, NCT02706782, NCT01935843, NCT01897415) with moderate clinical responses [
      • Li J.
      • Li W.
      • Huang K.
      • Zhang Y.
      • Kupfer G.
      • Zhao Q.
      Chimeric antigen receptor T cell (CAR-T) immunotherapy for solid tumors: lessons learned and strategies for moving forward.
      ].
      Table 3Adoptive cell transfer.
      InterventionStrategyCancer stageClinical phase, IdentifierOutcomes: Median Overall survival (Months)Bibliography
      MORAb-009, GemcitabineMonoclonal antibody, Cytotoxic drugsUnresectable (stage III or IV)Phase II, NCT005707136.5 (95% CI, 4.5–8.10), combination therapy

      6.9 (95% CI, 5.4–8.8), Pacebo plus Gemcitabine

      Morphotek. An Efficacy Study of MORAb-009 in Subjects With Pancreatic Cancer. https://clinicaltrials.gov/show/NCT00570713; 2007.

      HER2-specific CAR-T cellsAutologous T cellsPatients with HER-2 positive advanced pancreas cancerPhase I/II, NCT019358434.8 (95% CI, 1.5–8.3 months)
      • Feng K.
      • Liu Y.
      • Guo Y.
      • Qiu J.
      • Wu Z.
      • Dai H.
      • et al.
      Phase I study of chimeric antigen receptor modified T cells in treating HER2-positive advanced biliary tract cancers and pancreatic cancers.
      DC-CIK, Chemotherapy S-1DC-CIK vaccination, Cytotoxic drugsMetastatic, unresectable pancreatic cancerPhase I/II, NCT017815207 months; DC-CIK, Chemotherapy S-1

      4.2 months; DC-CIK alone

      4.7 months; chemotherapy S-1 alone

      1.73 months; supportive care only
      • Jiang N.
      • Qiao G.
      • Wang X.
      • Morse M.A.
      • Gwin W.R.
      • Zhou L.
      • et al.
      Dendritic Cell/Cytokine-Induced Killer Cell Immunotherapy Combined with S-1 in Patients with Advanced Pancreatic Cancer: A Prospective Study.
      CAR-T: chimeric antigen receptor T cells; HER2: human epidermal growth factor receptor 2; DC-CIK: dendritic and cytokine-induced killer cells.
      In a recent report, a non-engineered multiantigen specific T cell therapy was evaluated in patients with PAC. T cells were collected from patients’ blood and infused back to patients after stimulation with single T cell lines that targeted several TAAs, such as PRAME, SSX2, MAGEA4, NY-ESO-1, and Survivin. The study included three cohorts of patients; patients with unresectable metastatic disease that responded to first line chemotherapy (cohort A), patients with chemoresistant disease (cohort B) and patients with potentially resectable disease (cohort C). In 5 out of 9 patients in cohort A, response or disease control was achieved, including one CR. In cohort B, 50% of patients had disease control. Patients in cohort C were all subjected to surgical treatment. Most importantly, response was correlated with detection of tumor-reactive T cells in patients’ peripheral blood and within tumor biopsy samples (cohort C) postinfusion. T cell immunotherapy was well tolerated [

      Smaglo B, Wang T, Musher B, Lulla P, Van Buren IG, Fisher W, et al. PR01 Targeting pancreatic cancer using non-engineered, multi-antigen specific T cells (TACTOPS). Immune Cell Therapies for Cancer. San Francisco, California: American Association for Cancer Research (AACR); July 19–22, 2019.

      ].
      Chen et al. demonstrated that levels of mesothelin [
      • Argani P.
      • Iacobuzio-Donahue C.
      • Ryu B.
      • Rosty C.
      • Goggins M.
      • Wilentz R.E.
      • et al.
      Mesothelin is overexpressed in the vast majority of ductal adenocarcinomas of the pancreas: identification of a new pancreatic cancer marker by serial analysis of gene expression (SAGE).
      ] and IL-10 are significantly increased in patients with PAC, and mesothelin-specific T cell responses are significantly expanded in cancer patients [
      • Chen Y.
      • Ayaru L.
      • Mathew S.
      • Morris E.
      • Pereira S.P.
      • Behboudi S.
      Expansion of anti-mesothelin specific CD4+ and CD8+ T cell responses in patients with pancreatic carcinoma.
      ]. Preclinical evaluation of MORAb-009 (Amatuximab), a mouse-human chimeric IgG1κ mAb with an affinity for human mesothelin led to a marked reduction in tumor growth of mesothelin-expressing tumors in nude mice compared to chemotherapy or to MORAb-009 treatment alone [
      • Hassan R.
      • Ebel W.
      • Routhier E.L.
      • Patel R.
      • Kline J.B.
      • Zhang J.
      • et al.
      Preclinical evaluation of MORAb-009, a chimeric antibody targeting tumor-associated mesothelin.
      ]. In a phase I clinical trial that included patients with several solid tumors including 7 patients with PAC, MORAb-009 was well tolerated with maximum tolerated dose at 200 mg/m2. One patient with PAC had disease control for more than 6 months [
      • Hassan R.
      • Cohen S.J.
      • Phillips M.
      • Pastan I.
      • Sharon E.
      • Kelly R.J.
      • et al.
      Phase I clinical trial of the chimeric anti-mesothelin monoclonal antibody MORAb-009 in patients with mesothelin-expressing cancers.
      ]. However, in a randomized placebo-controlled phase II clinical trial that evaluated MORAb-009 in combination with gemcitabine, no significant differences were observed between the two treatment arms, with a median OS of 6.5 months (4.5–8.10) vs. 6.9 months (5.4–8.8) for the placebo arm [

      Morphotek. An Efficacy Study of MORAb-009 in Subjects With Pancreatic Cancer. https://clinicaltrials.gov/show/NCT00570713; 2007.

      ].
      Interestingly, a small phase I study evaluated the efficacy of T cells that were engineered to transiently express an mRNA encoding a CAR specific for mesothelin in 6 patients with chemo-refractory PAC. This type of ADT provided a potential antitumor activity [
      • Beatty G.L.
      • O'Hara M.H.
      • Lacey S.F.
      • Torigian D.A.
      • Nazimuddin F.
      • Chen F.
      • et al.
      Activity of Mesothelin-Specific Chimeric Antigen Receptor T Cells Against Pancreatic Carcinoma Metastases in a Phase 1 Trial.
      ]. Using an FDG PET/CT scan, it was observed that the metabolic active volume remained stable in 3 out of 6 patients and decreased by 69.2% in 1 patient with biopsy-proven mesothelin expression; however, in this patient, even though all liver lesions had a complete response, there was no effect on the primary tumor [
      • Beatty G.L.
      • O'Hara M.H.
      • Lacey S.F.
      • Torigian D.A.
      • Nazimuddin F.
      • Chen F.
      • et al.
      Activity of Mesothelin-Specific Chimeric Antigen Receptor T Cells Against Pancreatic Carcinoma Metastases in a Phase 1 Trial.
      ]. Additionally, Feng et al. performed a phase I trial of HER2-specific CAR T cells in patients with PAC showing encouraging signals of clinical activity, with 5 out of the 11 treated patients achieving SD and 2 achieving PR with median PFS at 4.8 months (95%CI 1.5–8.3 months) [
      • Feng K.
      • Liu Y.
      • Guo Y.
      • Qiu J.
      • Wu Z.
      • Dai H.
      • et al.
      Phase I study of chimeric antigen receptor modified T cells in treating HER2-positive advanced biliary tract cancers and pancreatic cancers.
      ].
      Furthermore, a prospective study [
      • Jiang N.
      • Qiao G.
      • Wang X.
      • Morse M.A.
      • Gwin W.R.
      • Zhou L.
      • et al.
      Dendritic Cell/Cytokine-Induced Killer Cell Immunotherapy Combined with S-1 in Patients with Advanced Pancreatic Cancer: A Prospective Study.
      ] using DCs and cytokine-induced killer cell (CIK) immunotherapy was performed using S-1 chemotherapy in patients with advanced PAC that produced significantly longer median OS and PFS (7 and 4.5 months, respectively) compared to DC-CIK (4.2 and 2.8 months), chemotherapy (4.7 and 3 months), or supportive care alone (1.73 and 1.4 months; P less than 0.001) [
      • Jiang N.
      • Qiao G.
      • Wang X.
      • Morse M.A.
      • Gwin W.R.
      • Zhou L.
      • et al.
      Dendritic Cell/Cytokine-Induced Killer Cell Immunotherapy Combined with S-1 in Patients with Advanced Pancreatic Cancer: A Prospective Study.
      ].

      Combination of immune checkpoint blockade and vaccine therapy in pancreatic adenocarcinoma

      Combination of immunotherapy drugs aims at inducing a durable anti-tumor T cell response [
      • Chung V.
      • Kos F.J.
      • Hardwick N.
      • Yuan Y.
      • Chao J.
      • Li D.
      • et al.
      Evaluation of safety and efficacy of p53MVA vaccine combined with pembrolizumab in patients with advanced solid cancers.
      ,
      • Le D.T.
      • Lutz E.
      • Uram J.N.
      • Sugar E.A.
      • Onners B.
      • Solt S.
      • et al.
      Evaluation of ipilimumab in combination with allogeneic pancreatic tumor cells transfected with a GM-CSF gene in previously treated pancreatic cancer.
      ,
      • Hopkins A.C.
      • Yarchoan M.
      • Durham J.N.
      • Yusko E.C.
      • Rytlewski J.A.
      • Robins H.S.
      • et al.
      T cell receptor repertoire features associated with survival in immunotherapy-treated pancreatic ductal adenocarcinoma.
      ,
      • Le D.T.
      • Crocenzi T.S.
      • Uram J.N.
      • Lutz E.R.
      • Laheru D.A.
      • Sugar E.A.
      • et al.
      Randomized phase II study of the safety, efficacy, and immune response of GVAX pancreas vaccine (with cyclophosphamide) and CRS-207 with or without nivolumab in patients with previously treated metastatic pancreatic adenocarcinoma (STELLAR).
      ]. In a small study that included 30 patients with previously treated PAC, patients were randomized to either high dose Ipilimumab (10 mg/kg) (arm 1) or Ipilimumab in combination with allogeneic PAC tumor cells transfected with GM-CSF cell-based vaccines (GVAX) (arm 2) [
      • Le D.T.
      • Lutz E.
      • Uram J.N.
      • Sugar E.A.
      • Onners B.
      • Solt S.
      • et al.
      Evaluation of ipilimumab in combination with allogeneic pancreatic tumor cells transfected with a GM-CSF gene in previously treated pancreatic cancer.
      ]. It was shown that combination immunotherapy resulted in disease control in 5 patients in total; two of them had initially a period of disease progression. Moreover, the median OS was 3.6 months for arm 1 compared to 5.7 months for arm 2 (HR 0.51, P = 0.072) and 1-year OS (7 vs. 27%) favored arm 2 [
      • Le D.T.
      • Lutz E.
      • Uram J.N.
      • Sugar E.A.
      • Onners B.
      • Solt S.
      • et al.
      Evaluation of ipilimumab in combination with allogeneic pancreatic tumor cells transfected with a GM-CSF gene in previously treated pancreatic cancer.
      ]. In patients with longer OS greater than 4.3 months, an increase of mesothelin-specific T cells was observed. In a more recent study, Hopkins et al. reported that patients with metastatic PAC receiving Ipilimumab or Nivolumab with or without GVAX and CRS-207 showed enhanced T cell responses. Interestingly, an increased number of expanded T cells after treatment correlated with longer survival only in patients receiving Ipilimumab [
      • Hopkins A.C.
      • Yarchoan M.
      • Durham J.N.
      • Yusko E.C.
      • Rytlewski J.A.
      • Robins H.S.
      • et al.
      T cell receptor repertoire features associated with survival in immunotherapy-treated pancreatic ductal adenocarcinoma.
      ].
      Further studies are evaluating the role of immune checkpoint inhibitors in combination with Cy/GVAX and CRS-207 vaccines (NCT02243371 [
      • Le D.T.
      • Crocenzi T.S.
      • Uram J.N.
      • Lutz E.R.
      • Laheru D.A.
      • Sugar E.A.
      • et al.
      Randomized phase II study of the safety, efficacy, and immune response of GVAX pancreas vaccine (with cyclophosphamide) and CRS-207 with or without nivolumab in patients with previously treated metastatic pancreatic adenocarcinoma (STELLAR).
      ], NCT02451982 [

      Hopkins SKCCCaJ, Institute NC, Squibb B-M. Neoadjuvant/Adjuvant GVAX Pancreas Vaccine (With CY) With or Without Nivolumab and Urelumab Trial for Surgically Resectable Pancreatic Cancer. https://clinicaltrials.gov/show/NCT02451982; 2016.

      ]). Another study in patients with advanced solid tumors, including patients with PAC, evaluated the combination of Pembrolizumab with p53-expressing modified vaccinia Ankara virus (p53MVA) vaccine that activates p53-reactive T cells in peripheral blood [
      • Chung V.
      • Kos F.J.
      • Hardwick N.
      • Yuan Y.
      • Chao J.
      • Li D.
      • et al.
      Evaluation of safety and efficacy of p53MVA vaccine combined with pembrolizumab in patients with advanced solid cancers.
      ]. The authors observed clinical responses in 3 out of 11 patients who had disease stabilization for 30, 32 and 49 weeks. Two patients who had clinical response during the treatment showed increased frequency and persistent presence of p53-reactive CD8+ T cells and increased expression of multiple immune response genes. The authors concluded that the combination is safe and may offer clinical benefit in selected patients [
      • Chung V.
      • Kos F.J.
      • Hardwick N.
      • Yuan Y.
      • Chao J.
      • Li D.
      • et al.
      Evaluation of safety and efficacy of p53MVA vaccine combined with pembrolizumab in patients with advanced solid cancers.
      ].

      Pancreatic tumor microenvironment

      Tumor microenvironment as a barrier for immunotherapy in pancreatic cancer

      The most significant barrier against an effective immunotherapy is the tumor microenvironment (TME) of PAC. PAC tumor is a combination of malignant cells and desmoplastic stroma which is characterized by an abundance of mesenchymal origin fibroblasts, blood vessels, pancreatic stellate and immune cells that are surrounded by extracellular matrix (Fig. 1A) [
      • Neesse A.
      • Algul H.
      • Tuveson D.A.
      • Gress T.M.
      Stromal biology and therapy in pancreatic cancer: a changing paradigm.
      ]. Thus, this structure protects PAC cells, as a physical barrier, against an effective delivery of chemotherapeutic agents [
      • Torphy R.J.
      • Zhu Y.
      • Schulick R.D.
      Immunotherapy for pancreatic cancer: Barriers and breakthroughs.
      ].
      Figure thumbnail gr1
      Fig. 1Pancreatic tumor microenvironment. (A) Tumor microenvironment creates a barrier for immunotherapy in pancreatic cancer as well for cytotoxic drugs to act significantly. (B) Resistance mechanism in pancreatic cancer inducing tumor progression, immunosuppression and cancer cell survival. CAF: Carcinoma-associated fibroblasts; PAC: Pancreatic adenocarcinoma; TAM: Tumor-associated macrophages; MDSC: Myeloid-derived suppressive cells; CTL: Cytotoxic T-lymphocytes; PSC: Pancreatic stellate cells; ECM: Extracellular matrix.
      Carcinoma-associated fibroblasts (CAFs) of epithelial malignancies, arising from pancreatic stellate cells, have been identified to express fibroblast activation protein-a (FAP) which associates with worse prognosis for PAC patients [
      • Park H.
      • Lee Y.
      • Lee H.
      • Kim J.W.
      • Hwang J.H.
      • Kim J.
      • et al.
      The prognostic significance of cancer-associated fibroblasts in pancreatic ductal adenocarcinoma.
      ]. Furthermore, FAP appears to have immunosuppressive properties in the TME as it was identified with a vaccine-based immunotherapy in in vivo mice model [
      • Kraman M.
      • Bambrough P.J.
      • Arnold J.N.
      • Roberts E.W.
      • Magiera L.
      • Jones J.O.
      • et al.
      Suppression of antitumor immunity by stromal cells expressing fibroblast activation protein-alpha.
      ]. Another study using KPC mice showed that depletion of FAP+ stromal cells enhanced the role of anti-PD-L1 and anti-CTLA-4 checkpoint inhibitors, to further associate the role of stroma and TME in suppressing anti-tumor immunity [
      • Feig C.
      • Jones J.O.
      • Kraman M.
      • Wells R.J.
      • Deonarine A.
      • Chan D.S.
      • et al.
      Targeting CXCL12 from FAP-expressing carcinoma-associated fibroblasts synergizes with anti-PD-L1 immunotherapy in pancreatic cancer.
      ]. Moreover, CAFs produce a plethora of extracellular matrix proteins, cytokines, and vascular endothelial cells, all infiltrated by different immunogenic cells, such as lymphocytes, macrophages and mast cells (Fig. 1B). This highly fibrotic stroma has been identified to surround both primary and metastatic PAC tumors [
      • Whatcott C.J.
      • Diep C.H.
      • Jiang P.
      • Watanabe A.
      • LoBello J.
      • Sima C.
      • et al.
      Desmoplasia in Primary Tumors and Metastatic Lesions of Pancreatic Cancer.
      ]. In orthotopic mouse models, co-injection of tumor cells and pancreatic stellate cells increased the size and metastatic potential of PAC tumors [
      • Pereira B.A.
      • Vennin C.
      • Papanicolaou M.
      • Chambers C.R.
      • Herrmann D.
      • Morton J.P.
      • et al.
      CAF Subpopulations: A New Reservoir of Stromal Targets in Pancreatic Cancer.
      ]. However, the interaction between PAC tumor cells and stroma is characterized by increased complexity [
      • Neesse A.
      • Algul H.
      • Tuveson D.A.
      • Gress T.M.
      Stromal biology and therapy in pancreatic cancer: a changing paradigm.
      ,
      • Liu T.
      • Han C.
      • Wang S.
      • Fang P.
      • Ma Z.
      • Xu L.
      • et al.
      Cancer-associated fibroblasts: an emerging target of anti-cancer immunotherapy.
      ].
      Moffitt et al. identified two different stromal subtypes, normal and activated (with worse median OS for the normal subtype), based on different genes expression [
      • Moffitt R.A.
      • Marayati R.
      • Flate E.L.
      • Volmar K.E.
      • Loeza S.G.
      • Hoadley K.A.
      • et al.
      Virtual microdissection identifies distinct tumor- and stroma-specific subtypes of pancreatic ductal adenocarcinoma.
      ]. The first subtype is characterized by high expression of genes that are associated with macrophages, such as integrins (ITGAM) and chemokine (C-C motif) ligand (CCL) 13/18. Despite the fact that PAC is a non-immunogenic cancer, a robust amount of infiltrate immunogenic cells, such as tumor-associated macrophages (TAMs), myeloid derived suppressor cells (MDSCs) and neutrophils, has been identified [
      • Young K.
      • Hughes D.J.
      • Cunningham D.
      • Starling N.
      Immunotherapy and pancreatic cancer: unique challenges and potential opportunities.
      ]. In contrast, tumor-infiltrating lymphocytes (TILs) are presented in smaller numbers, aggregated or trapped within the stroma as clusters, prevented from directly interacting with the cancer cells of PAC tumor [
      • Chen D.S.
      • Mellman I.
      Elements of cancer immunity and the cancer-immune set point.
      ]. PAC tumor cells secrete several molecules, such as CCL2 and GM-CSF, which lead to MDSCs and TAMs attraction to the TME (Fig. 1B) [
      • Young K.
      • Hughes D.J.
      • Cunningham D.
      • Starling N.
      Immunotherapy and pancreatic cancer: unique challenges and potential opportunities.
      ]. MDSCs have been associated with worse prognosis in PAC patients with resected disease. The presence of CD8+ and CD4+ T cells (effector T cells) appear to have a beneficial effect on patients’ prognosis [
      • Foley K.
      • Kim V.
      • Jaffee E.
      • Zheng L.
      Current progress in immunotherapy for pancreatic cancer.
      ]. In addition, B-cells that produce interleukin-35 (IL-35) are accumulated in the TME during the early stage of PAC carcinogenesis [
      • Pylayeva-Gupta Y.
      • Das S.
      • Handler J.S.
      • Hajdu C.H.
      • Coffre M.
      • Koralov S.B.
      • et al.
      IL35-Producing B Cells Promote the Development of Pancreatic Neoplasia.
      ].
      Although T cells are present in PAC TME, they are unable to initiate an immune response against tumor cells. Several immunosuppressive molecules, such as IL-10 and transforming growth factor (TGF)-β are responsible for T cell inactivation [
      • von Bernstorff W.
      • Voss M.
      • Freichel S.
      • Schmid A.
      • Vogel I.
      • Johnk C.
      • et al.
      Systemic and local immunosuppression in pancreatic cancer patients.
      ]. Furthermore, regulatory (FOXP3+) T cells in TME, macrophages and γδ T cells (an immunosuppressive type of T cells) prevent the effector T cells to enter TME via a mechanism which is associated with PD-1/PD-L1 signaling [
      • Blazquez J.L.
      • Benyamine A.
      • Pasero C.
      • Olive D.
      New Insights Into the Regulation of gammadelta T Cells by BTN3A and Other BTN/BTNL in Tumor Immunity.
      ].

      Immunotherapy in MSI pancreatic cancer

      The mismatch repair (MMR) system is composed by several genes (MSH2, MSH3, MSH6, PMS1, MLH1 and PMS2) playing a pivotal role in error repair during DNA replication. A defective MMR system leads to random mutations occurring in small repetitive elements referred to as microsatellite instability (MSI) [
      • Lower S.S.
      • McGurk M.P.
      • Clark A.G.
      • Barbash D.A.
      Satellite DNA evolution: old ideas, new approaches.
      ,
      • Veigl M.L.
      • Kasturi L.
      • Olechnowicz J.
      • Ma A.H.
      • Lutterbaugh J.D.
      • Periyasamy S.
      • et al.
      Biallelic inactivation of hMLH1 by epigenetic gene silencing, a novel mechanism causing human MSI cancers.
      ]. The accumulation of somatic mutations leads to increased neoantigen formation serving as targets for the immune system and promotes the expression of inflammatory cytokines and T cell activation, thus rendering tumors susceptible to immunotherapy [
      • Le D.T.
      • Durham J.N.
      • Smith K.N.
      • Wang H.
      • Bartlett B.R.
      • Aulakh L.K.
      • et al.
      Mismatch repair deficiency predicts response of solid tumors to PD-1 blockade.
      ]. Although there is limited and inconsistent literature regarding PAC patients with mismatch repair deficiency (dMMR/MSI), these tumors have been reported to demonstrate prolonged survival rates. Hu et al. [
      • Hu Z.I.
      • Shia J.
      • Stadler Z.K.
      • Varghese A.M.
      • Capanu M.
      • Salo-Mullen E.
      • et al.
      Evaluating Mismatch Repair Deficiency in Pancreatic Adenocarcinoma: Challenges and Recommendations.
      ] used next generation sequencing to estimate MMR status on 833 PAC patients. A dMMR status was found to be a rare event in PAC with a frequency of 0.8% (7/833) and Lynch syndrome was detected in all 7 patients with dMMR PAC. In a study presented by Nataka and colleagues [
      • Nakata B.
      • Wang Y.Q.
      • Yashiro M.
      • Nishioka N.
      • Tanaka H.
      • Ohira M.
      • et al.
      Prognostic value of microsatellite instability in resectable pancreatic cancer.
      ], though, 17.4% of the patients with histologically proven PAC were reported as MSI-High (MSI-H), while Eatrides et al. reported MSI-H prevalence as high as 22% [
      • Eatrides J.M.
      • Coppola D.
      • Diffalha S.A.
      • Kim R.D.
      • Springett G.M.
      • Mahipal A.
      Microsatellite instability in pancreatic cancer.
      ]. Variabilities in sample size, histology and non-standardized testing plus evolving detection methods could be possible etiological factors for the observed discordance regarding its prevalence in PAC. Both studies, though, presented a comparatively better prognosis and significantly prolonged survival for MSI-H compared to MSI-Low PAC [
      • Nakata B.
      • Wang Y.Q.
      • Yashiro M.
      • Nishioka N.
      • Tanaka H.
      • Ohira M.
      • et al.
      Prognostic value of microsatellite instability in resectable pancreatic cancer.
      ,
      • Fraune C.
      • Burandt E.
      • Simon R.
      • Hube-Magg C.
      • Makrypidi-Fraune G.
      • Kluth M.
      • et al.
      MMR Deficiency is Homogeneous in Pancreatic Carcinoma and Associated with High Density of Cd8-Positive Lymphocytes.
      ,
      • Yamamoto H.
      • Itoh F.
      • Nakamura H.
      • Fukushima H.
      • Sasaki S.
      • Perucho M.
      • et al.
      Genetic and clinical features of human pancreatic ductal adenocarcinomas with widespread microsatellite instability.
      ]. A significant association between use of checkpoint inhibitors and dMMR has been reported for patients with PAC [
      • Kim S.T.
      • Klempner S.J.
      • Park S.H.
      • Park J.O.
      • Park Y.S.
      • Lim H.Y.
      • et al.
      Correlating programmed death ligand 1 (PD-L1) expression, mismatch repair deficiency, and outcomes across tumor types: implications for immunotherapy.
      ] emerging the potential role of MSI-H status as predictive of response to immunotherapy.
      Correlation between PD-L1 and dMMR/MSI on PAC tumors would be central to optimizing patient outcomes; however, literature in this regard is inconsistent. Even though there was a significant correlation between PD-L1 and MLH1/MSH2 in advanced gastrointestinal or other types of cancers [
      • Kim S.T.
      • Klempner S.J.
      • Park S.H.
      • Park J.O.
      • Park Y.S.
      • Lim H.Y.
      • et al.
      Correlating programmed death ligand 1 (PD-L1) expression, mismatch repair deficiency, and outcomes across tumor types: implications for immunotherapy.
      ], no sufficient data were presented on PAC patients. In another study performed by Salem et al. [
      • Salem M.E.
      • Puccini A.
      • Grothey A.
      • Raghavan D.
      • Goldberg R.M.
      • Xiu J.
      • et al.
      Landscape of Tumor Mutation Load, Mismatch Repair Deficiency, and PD-L1 Expression in a Large Patient Cohort of Gastrointestinal Cancers.
      ] on 870 patients with PAC, a positive PD-L1 expression of 11.1% and 8.6%, was reported on MSI-H and MSS PACs, respectively. On the other hand, tumor mutational burden (TMB) is the total number of mutations per coding area of a tumor gene increasing the sensitivity to immunotherapy [
      • Champiat S.
      • Ferte C.
      • Lebel-Binay S.
      • Eggermont A.
      • Soria J.C.
      Exomics and immunogenics: Bridging mutational load and immune checkpoints efficacy.
      ]. Typically, MSI-H tumors may have high TMB [
      • Salem M.E.
      • Puccini A.
      • Grothey A.
      • Raghavan D.
      • Goldberg R.M.
      • Xiu J.
      • et al.
      Landscape of Tumor Mutation Load, Mismatch Repair Deficiency, and PD-L1 Expression in a Large Patient Cohort of Gastrointestinal Cancers.
      ]. In the study by Salem et al. only 1.4% of PAC subgroup was both MSI-high and TMB-high [
      • Salem M.E.
      • Puccini A.
      • Grothey A.
      • Raghavan D.
      • Goldberg R.M.
      • Xiu J.
      • et al.
      Landscape of Tumor Mutation Load, Mismatch Repair Deficiency, and PD-L1 Expression in a Large Patient Cohort of Gastrointestinal Cancers.
      ].
      Nevertheless, in May 2017, immune checkpoint inhibitor pembrolizumab was granted tumor site agnostic approval by the US Food and Drug Administration (FDA) for adult and pediatric patients with unresectable or metastatic cancer which would be identified as dMMR/MSI-H. Based on response to pembrolizumab as defined by Response Evaluation Criteria in Solid Tumors (RECIST), 83% of PAC patients showed a response to immunotherapy with this checkpoint inhibitor and a response duration range of 2.6–9.2 months [
      • Lemery S.
      • Keegan P.
      • Pazdur R.
      First FDA Approval Agnostic of Cancer Site - When a Biomarker Defines the Indication.
      ]. Efficacy of pembrolizumab in dMMR/MSI-H PAC was also reported as part of the phase II Keynote-158 study [
      • Marabelle A.
      • Le D.T.
      • Ascierto P.A.
      • Giacomo A.M.D.
      • Jesus-Acosta A.D.
      • Delord J.-P.
      • et al.
      Efficacy of Pembrolizumab in Patients With Noncolorectal High Microsatellite Instability/Mismatch Repair-Deficient Cancer: Results From the Phase II KEYNOTE-158 Study.
      ] with OS and PFS evaluated at 4.0 (95% CI 2.1 to 9.8) and 2.1 (95% CI 1.9 to 3.4) months, respectively (Table 5). Response was assessed per RECIST version 1.1 by independent central radiologic review.
      In 2019, a case report by Chen et al. [
      • Chen M.
      • Yang S.
      • Fan L.
      • Wu L.
      • Chen R.
      • Chang J.
      • et al.
      Combined Antiangiogenic Therapy and Immunotherapy Is Effective for Pancreatic Cancer With Mismatch Repair Proficiency but High Tumor Mutation Burden: A Case Report.
      ], described a cT4N1M1 PAC patient with mismatch repair proficiency (pMMR) demonstrating a good response to immunotherapy after a series of ineffective treatments. A PR was observed when the patient was treated with the combination of pembrolizumab and the antiangiogenic agent lenvatinib, resulting in primary tumor shrinkage and of the metastatic lesion in the liver by 27.3% and 33.0%, respectively [
      • Chen M.
      • Yang S.
      • Fan L.
      • Wu L.
      • Chen R.
      • Chang J.
      • et al.
      Combined Antiangiogenic Therapy and Immunotherapy Is Effective for Pancreatic Cancer With Mismatch Repair Proficiency but High Tumor Mutation Burden: A Case Report.
      ]. Further studies and clinical trials are needed to assess the potential role of MSI to guide immunotherapy across PAC patients. Currently, several clinical trials using MSI-H status are recruiting PAC patients (Table 5). Immune checkpoint inhibitors either alone or in combination with chemotherapy or other immunotherapy agents are being studied.

      Antigenicity and tumor mutational burden in pancreatic cancer

      The anticancer immune response is a complicate and multistep process. The first step is associated with the release and presentation of neoantigens: tumor-associated or tumor-specific antigens. Neoantigen presentation in TME leads to increasing number of TILs and enhanced sensitivity to checkpoint inhibitors [
      • Young K.
      • Hughes D.J.
      • Cunningham D.
      • Starling N.
      Immunotherapy and pancreatic cancer: unique challenges and potential opportunities.
      ].
      PAC is characterized by the low TMB with only 1 mutation/megabase (melanoma and lung cancer have 10 mutation/megabase). Somatic mutations lead to gene expression and subsequently to the formation of neoantigens in tumors [
      • Alexandrov L.B.
      • Nik-Zainal S.
      • Wedge D.C.
      • Aparicio S.A.
      • Behjati S.
      • Biankin A.V.
      • et al.
      Signatures of mutational processes in human cancer.
      ]. Despite the fact of comparatively low TMB, PAC appears to express quality neoantigens which predict to have a robust level of expression on HLA class 1 molecules [
      • Bailey P.
      • Chang D.K.
      • Forget M.A.
      • Lucas F.A.
      • Alvarez H.A.
      • Haymaker C.
      • et al.
      Exploiting the neoantigen landscape for immunotherapy of pancreatic ductal adenocarcinoma.
      ]. In PAC, the activation of T cells through neoantigen presentation by APCs, such as DCs, on the MHC I and II, appears to be problematic. In addition, DCs in PAC tend to be immature with very low density in the TME and low TMB which leads to impaired antigen recognition and subsequent T cell activation [
      • Young K.
      • Hughes D.J.
      • Cunningham D.
      • Starling N.
      Immunotherapy and pancreatic cancer: unique challenges and potential opportunities.
      ].

      Conclusion

      Despite advances in cancer treatment and translational research, PAC is associated with extremely poor outcomes and remains a lethal malignancy. The main cure for PAC is surgical resection; however, at the time of diagnosis, more than 60% of patients have advanced disease that precludes surgical intervention. Traditional treatment strategies such as surgery, locoregional therapies, chemotherapy and radiotherapy still provide low survival rates of less than 1 year for the majority of the patients. On the other hand, immunotherapy has marked a therapeutic renaissance for many solid tumors, including melanoma, lung cancer, renal cell cancer and others.
      In this era of immunotherapy, many clinical trials seek to evaluate the efficacy of immunotherapy in PAC, including the effect of immune checkpoint inhibitors (Table 1), cancer vaccines (Table 2), adoptive cell transfer (Table 3), and combinations with chemoradiotherapy or other molecularly targeted agents (Table 4); however, results have uniformly been disappointing for the majority of these trials. It is known that PAC is a tumor with low immunogenicity, which is attributed to low TMB. Low number of mutations hampers production and release of neoantigens and subsequently leads to low number of TILs [

      Upadhrasta S, Zheng L. Strategies in Developing Immunotherapy for Pancreatic Cancer: Recognizing and Correcting Multiple Immune “Defects” in the Tumor Microenvironment. J Clin Med. 2019; 8.

      ]. Furthermore, PAC tissue is characterized by a profoundly desmoplastic stroma, which consists of high number of fibroblasts that own immunosuppressive abilities. The heterogeneity of desmoplastic stroma and the dominance of immunosuppressive cells, such as TAMs, CAFs, MDSCs, and Tregs in TME construct a barrier for the efficacy of immunotherapy drugs [
      • Torphy R.J.
      • Zhu Y.
      • Schulick R.D.
      Immunotherapy for pancreatic cancer: Barriers and breakthroughs.
      ].
      Table 4Combination therapy of immune checkpoint blockade and vaccine therapy.
      InterventionStrategyCancer stageClinical phase, IdentifierOutcomes: Median Overall survival (Months)Bibliography
      Ipilimumab, GVAXCTLA-4 inhibitor, Whole-cell vaccineUnresectable metastatic pancreatic cancerPhase I, NCT008364075.7 (95% CI, 4.3–14.7), Combination therapy

      3.6 (95% CI, 2.5–9.2), Ipilimumab alone
      • Le D.T.
      • Lutz E.
      • Uram J.N.
      • Sugar E.A.
      • Onners B.
      • Solt S.
      • et al.
      Evaluation of ipilimumab in combination with allogeneic pancreatic tumor cells transfected with a GM-CSF gene in previously treated pancreatic cancer.
      Nivolumab, Cy, GVAX, CRS-207PD-1 inhibitor, Cytotoxic drugs, Whole-cell vaccine, Listeria vaccinePatients with previously treated metastatic pancreatic adenocarcinomaPhase II, NCT02243371No results posted yet
      • Le D.T.
      • Crocenzi T.S.
      • Uram J.N.
      • Lutz E.R.
      • Laheru D.A.
      • Sugar E.A.
      • et al.
      Randomized phase II study of the safety, efficacy, and immune response of GVAX pancreas vaccine (with cyclophosphamide) and CRS-207 with or without nivolumab in patients with previously treated metastatic pancreatic adenocarcinoma (STELLAR).
      Nivolumab, Cy, GVAX, UrelumabPD-1 inhibitor, Cytotoxic drugs, Whole-cell vaccine, human IgG4Neoadjuvant and adjuvant treatment of patients with surgically resectable adenocarcinomaPhase I, II

      NCT02451982
      No results posted yet

      Hopkins SKCCCaJ, Institute NC, Squibb B-M. Neoadjuvant/Adjuvant GVAX Pancreas Vaccine (With CY) With or Without Nivolumab and Urelumab Trial for Surgically Resectable Pancreatic Cancer. https://clinicaltrials.gov/show/NCT02451982; 2016.

      Cy: Cyclophosphamide; CRS-207: Live, attenuated Listeria monocytogenes expressing mesothelin.
      Table 5Clinical trials using immunotherapy and microsatellite instability (MSI) in pancreatic cancer patients.
      InterventionStrategyCancer stageClinical phase, IdentifierStatus/Outcomes: Median Overall Survival (Months)Estimated EnrollmentBibliography
      PembrolizumabPD-1 inhibitorMSI High/advanced pancreatic cancerPhase II, NCT02628067Recruiting/4.0 (95% CI 2.1 to 9.8)1395 participants
      • Marabelle A.
      • Le D.T.
      • Ascierto P.A.
      • Giacomo A.M.D.
      • Jesus-Acosta A.D.
      • Delord J.-P.
      • et al.
      Efficacy of Pembrolizumab in Patients With Noncolorectal High Microsatellite Instability/Mismatch Repair-Deficient Cancer: Results From the Phase II KEYNOTE-158 Study.
      Pembrolizumab, XmAb®22841PD-1 inhibitor, CTLA-4/LAG-3 inhibitorMSI High/advanced or metastatic pancreatic cancerPhase I, NCT03849469Recruiting242 participants

      Xencor I, Research IC. A Study of XmAb®22841 Monotherapy & in Combination w/ Pembrolizumab in Subjects w/ Selected Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT03849469; 2019.

      Pembrolizumab, SonidegibPD-1 inhibitor, Hh-pathway inhibitorMSI High/advanced pancreatic cancerPhase I, NCT04007744Recruiting45 participants

      Clinic M, Institute NC. Sonidegib and Pembrolizumab in Treating Patients With Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT04007744; 2020.

      Pembrolizumab, DEBIO1143PD-1 inhibitor, IAP inhibitorNon-MSI High/ advanced/metastatic pancreatic ductal adenocarcinomaPhase I, NCT03871959Recruiting51 participants

      Berard CL, Sharp M, Corp. D, SA DI. Pembrolizumab In Combination With Debio 1143 In Pancreatic and Colorectal Advanced/Metastatic Adenocarcinoma. https://clinicaltrials.gov/show/NCT03871959; 2019.

      LY3300054, Ramucirumab, Abemaciclib, Merestinib, LY3321367PD-1 inhibitor, VEGFR2 antagonist, CDK inhibitor, HGFR inhibitor, anti-TIM3MSI High/pancreatic cancerPhase I, NCT02791334Recruiting215 participants

      Lilly E, Company. A Study of Anti-PD-L1 Checkpoint Antibody (LY3300054) Alone and in Combination in Participants With Advanced Refractory Solid Tumors. https://clinicaltrials.gov/show/NCT02791334; 2016.

      Nivolumab, Ipilimumab, Radiation TherapyPD-1 inhibitor, CTLA-4 inhibitorMSI High/pancreatic adenocarcinomaPhase II, NCT03104439Recruiting80 participants

      Hospital MG, Squibb B-M. Nivolumab and Ipilimumab and Radiation Therapy in MSS and MSI High Colorectal and Pancreatic Cancer. https://clinicaltrials.gov/show/NCT03104439; 2017.

      FT500, Nivolumab, Pembrolizumab, Atezolizumab, Cy, FludarabineiPSC-NK cell

      PD-1 inhibitor, PD-1 inhibitor, PD-L1 inhibitor Cytotoxic drugs
      MSI High/advanced pancreatic cancerPhase I, NCT03841110Recruiting76 participants

      Therapeutics F. FT500 as Monotherapy and in Combination With Immune Checkpoint Inhibitors in Subjects With Advanced Solid Tumors. https://clinicaltrials.gov/show/NCT03841110; 2019.

      TIL Fludarabine, CyAdoptive cell transfer Cytotoxic drugsMSI High/advanced, recurrent, or metastatic pancreatic cancerPhase II, NCT03935893Recruiting10 participants

      Kammula U, Pittsburgh Uo. Adoptive Transfer of Tumor Infiltrating Lymphocytes for Advanced Solid Cancers. https://clinicaltrials.gov/show/NCT03935893; 2019.

      MSI: microsatellite instability; Hh-pathway: Hedgehog signaling pathway; IAP: inhibitor of apoptosis proteins; VEGFR2: vascular endothelial growth factor receptor 2; CDK: Cyclin-dependent kinase; HGFR: hepatocyte growth factor receptor; TIM3: T cell immunoglobulin and mucin domain-3; TIL: tumor infiltrating lymphocytes, Cy: Cyclophosphamide; iPSC-NK: induced pluripotent stem cells-derived Natural Killer cells.
      Nevertheless, there seems to be a synergistic effect for immunotherapy in combination with cytotoxic drugs. An increased OS, approaching 20 months, was demonstrated for patients with localized disease treated either with checkpoint inhibitors and chemoradiotherapy or vaccine with/without chemoradiotherapy. Moreover, patients positive to KRAS mutations, eligible for K-Ras vaccine or patients responding to vaccination had almost double survival rates compared to controls.
      Further research needs to focus on how to overcome immunotherapy resistance by targeting multiple immune defects using combinatorial immunotherapy and cytotoxic approaches in patients with PAC. In addition, the identification of valid biomarkers will guide appropriate treatment selection with the view to improve patient outcomes. Although there is limited and inconsistent literature regarding PAC patients with mismatch repair deficiency (dMMR/MSI), this small subgroup of patients has been reported to demonstrate prolonged survival rates. Furthermore, PD-L1 expression and dMMR/MSI have shown a prognostic response to immunotherapy in many malignancies. Therefore, combined approaches using different therapeutic strategies with immunotherapy may provide some hope in dMMR PAC patients (Table 5).

      Declaration of Competing Interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Acknowledgments

      Financial support: None.

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