Pancreatic Ductal Adenocarcinoma and Immune Checkpoint Inhibitors: The Gray Curtain of Immunotherapy and Spikes of Lights

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a poor 5-year overall survival rate (~10%). The revolution of immunotherapy in clinical oncology has not substantially changed clinical outcome for patients with PDAC. Despite outstanding efforts, neither immune checkpoint inhibitors (ICIs) alone, nor in combination with chemotherapy or targeted therapies have shown encouraging results. This failure mirrors the lack of knowledge about the real key players of immune system senescence and the complexity of the tumor microenvironment in PDAC. However, some hope can be derived from PARP-inhibitor combinations, vaccines, and CAR-T-cells therapy. In this review, we comprehensively summarize the latest updates about the use of ICIs in PDAC, focusing on clinical evidence and ongoing studies highlighting explanations for the failure of immunotherapy and possible solutions.

Where Do We Stand with Immunotherapy for Advanced Pancreatic Ductal Adenocarcinoma: A Synopsis of Clinical Outcomes

Pancreatic cancer is the seventh leading cause of cancer-related mortality in both sexes across the globe. It is associated with extremely poor prognosis and remains a critical burden worldwide due to its low survival rates. Histologically, pancreatic ductal adenocarcinoma (PDAC) accounts for 80% of all pancreatic cancers; the majority of which are diagnosed at advanced stages, which makes them ineligible for curative surgery. Conventional chemotherapy provides a five-year overall survival rate of less than 8% forcing scientists and clinicians to search for better treatment strategies. Recent discoveries in cancer immunology have resulted in the incorporation of immunotherapeutic strategies for cancer treatment. Particularly, immune-checkpoint inhibitors, adoptive cell therapies and cancer vaccines have already shifted guidelines for some malignancies, although their efficacy in PDAC has yet to be elucidated. In this review, we summarize the existing clinical data on immunotherapy clinical outcomes in patients with advanced or metastatic PDAC.

The Role of Immunotherapy in Pancreatic Cancer

Pancreatic adenocarcinoma remains one of the most lethal cancers globally, with a significant need for improved therapeutic options. While the recent breakthroughs of immunotherapy through checkpoint inhibitors have dramatically changed treatment paradigms in other malignancies based on considerable survival benefits, this is not so for pancreatic cancer. Chemotherapies with modest benefits are still the cornerstone of advanced pancreatic cancer treatment. Pancreatic cancers are inherently immune-cold tumors and have been largely refractory to immunotherapies in clinical trials. Understanding and overcoming the current failures of immunotherapy through elucidating resistance mechanisms and developing novel therapeutic approaches are essential to harnessing the potential durable benefits of immune-modulating therapy in pancreatic cancer patients.

Modulation of Type I Interferon Responses to Influence Tumor-Immune Cross Talk in PDAC

Immunotherapy has revolutionized the treatment of many cancer types. However, pancreatic ductal adenocarcinomas (PDACs) exhibit poor responses to immune checkpoint inhibitors with immunotherapy-based trials not generating convincing clinical activity. PDAC tumors often have low infiltration of tumor CD8+ T cells and a highly immunosuppressive microenvironment. These features classify PDAC as immunologically "cold." However, the presence of tumor T cells is a favorable prognostic feature in PDAC. Intrinsic tumor cell properties govern interactions with the immune system. Alterations in tumor DNA such as genomic instability, high tumor mutation burden, and/or defects in DNA damage repair are associated with responses to both immunotherapy and chemotherapy. Cytotoxic or metabolic stress produced by radiation and/or chemotherapy can act as potent immune triggers and prime immune responses. Damage- or stress-mediated activation of nucleic acid-sensing pathways triggers type I interferon (IFN-I) responses that activate innate immune cells and natural killer cells, promote maturation of dendritic cells, and stimulate adaptive immunity. While PDAC exhibits intrinsic features that have the potential to engage immune cells, particularly following chemotherapy, these immune-sensing mechanisms are ineffective. Understanding where defects in innate immune triggers render the PDAC tumor-immune interface less effective, or how T-cell function is suppressed will help develop more effective treatments and harness the immune system for durable outcomes. This review will focus on the pivotal role played by IFN-I in promoting tumor cell-immune cell cross talk in PDAC. We will discuss how PDAC tumor cells bypass IFN-I signaling pathways and explore how these pathways can be co-opted or re-engaged to enhance the therapeutic outcome.

Uncovering key targets of success for immunotherapy in pancreatic cancer

INTRODUCTION

Despite available treatment options, pancreatic ductal adenocarcinoma (PDAC) is frequently lethal. Recent immunotherapy strategies have failed to yield any notable impact. Therefore, research is focussed on unearthing new drug targets and therapeutic strategies to tackle this malignancy and attain more positive outcomes for patients.

AREAS COVERED

In this perspective article, we evaluate the main resistance mechanisms to immune checkpoint inhibitors (ICIs) and the approaches to circumvent them. We also offer an assessment of concluded and ongoing trials of PDAC immunotherapy. Literature research was performed on Pubmed accessible through keywords such as: 'pancreatic ductal adenocarcinoma,' 'immunotherapy,' 'immunotherapy resistance,' 'immune escape,' 'biomarkers.' Papers published between 2000 and 2021 were selected.

EXPERT OPINION

The tumor microenvironment is a critical variable of treatment resistance because of its role as a physical barrier and inhibitory immune signaling. Promising therapeutic strategies appear to be a combination of immunotherapeutics with other targeted treatments. Going forward, predictive biomarkers are required to improve patient selection. Biomarker-driven trials could enhance approaches for assessing the role of immunotherapy in PDAC.

Next-generation immunotherapy for pancreatic ductal adenocarcinoma: navigating pathways of immune resistance

To date, the use of immune checkpoint inhibitors has proven largely ineffective in patients with advanced pancreatic ductal adenocarcinoma. A combination of low tumor antigenicity, deficits in immune activation along with an exclusive and suppressive tumor microenvironment result in resistance to host defensives. However, a deepening understanding of these immune escape and suppressive mechanisms has led to the discovery of novel molecular targets and treatment strategies that may hold the key to a long-awaited therapeutic breakthrough. In this review, we describe the tumor-intrinsic and microenvironmental barriers to modern immunotherapy, examine novel immune-based and targeted modalities, summarize relevant pre-clinical findings and human experience, and, finally, discuss novel synergistic approaches to overcome immune-resistance in pancreatic cancer. Beyond checkpoint inhibition, immune agonists and anti-tumor vaccines represent promising strategies to stimulate host response via activation and expansion of anti-tumor immune effectors. Off-the-shelf natural killer cell therapies may offer an effective method for bypassing downregulated tumor antigen presentation. In parallel with this, sophisticated targeting of crosstalk between tumor and tumor-associated immune cells may lead to enhanced immune infiltration and survival of anti-tumor lymphocytes. A future multimodal treatment strategy involving immune priming/activation, tumor microenvironment reprogramming, and immune checkpoint blockade may help transform pancreatic cancer into an immunogenic tumor.

Therapeutic Application of Monoclonal Antibodies in Pancreatic Cancer: Advances, Challenges and Future Opportunities

Pancreatic cancer remains as one of the most aggressive cancer types. In the absence of reliable biomarkers for its early detection and more effective therapeutic interventions, pancreatic cancer is projected to become the second leading cause of cancer death in the Western world in the next decade. Therefore, it is essential to discover novel therapeutic targets and to develop more effective and pancreatic cancer-specific therapeutic agents. To date, 45 monoclonal antibodies (mAbs) have been approved for the treatment of patients with a wide range of cancers; however, none has yet been approved for pancreatic cancer. In this comprehensive review, we discuss the FDA approved anticancer mAb-based drugs, the results of preclinical studies and clinical trials with mAbs in pancreatic cancer and the factors contributing to the poor response to antibody therapy (e.g. tumour heterogeneity, desmoplastic stroma). MAb technology is an excellent tool for studying the complex biology of pancreatic cancer, to discover novel therapeutic targets and to develop various forms of antibody-based therapeutic agents and companion diagnostic tests for the selection of patients who are more likely to benefit from such therapy. These should result in the approval and routine use of antibody-based agents for the treatment of pancreatic cancer patients in the future.

Advances in Targeted Therapy and Immunotherapy for Pancreatic Cancer

Pancreatic cancer is a highly aggressive malignancy with an overall 5-year survival rate of <6% due to therapeutic resistance and late-stage diagnosis. These statistics have not changed despite 50 years of research and therapeutic development. Pancreatic cancer is predicted to become the second leading cause of cancer mortality by the year 2030. Currently, the treatment options for pancreatic cancer are limited. This disease is usually diagnosed at a late stage, which prevents curative surgical resection. Chemotherapy is the most frequently used approach for pancreatic cancer treatment and has limited effects. In many other cancer types, targeted therapy and immunotherapy have made great progress and have been shown to be very promising prospects; these treatments also provide hope for pancreatic cancer. The need for research on targeted therapy and immunotherapy is pressing due to the poor prognosis of pancreatic cancer, and in recent years, there have been some breakthroughs for targeted therapy and immunotherapy in pancreatic cancer. This review summarizes the current preclinical and clinical studies of targeted therapy and immunotherapy for pancreatic cancer and ends by describing the challenges and outlook.

The State-of-the-Art of Phase II/III Clinical Trials for Targeted Pancreatic Cancer Therapies

Pancreatic cancer is a devastating disease with very poor prognosis. Currently, surgery followed by adjuvant chemotherapy represents the only curative option which, unfortunately, is only available for a small group of patients. The majority of pancreatic cancer cases are diagnosed at advanced or metastatic stage when surgical resection is not possible and treatment options are limited. Thus, novel and more effective therapeutic strategies are urgently needed. Molecular profiling together with targeted therapies against key hallmarks of pancreatic cancer appear as a promising approach that could overcome the limitations of conventional chemo- and radio-therapy. In this review, we focus on the latest personalised and multimodal targeted therapies currently undergoing phase II or III clinical trials. We discuss the most promising findings of agents targeting surface receptors, angiogenesis, DNA damage and cell cycle arrest, key signalling pathways, immunotherapies, and the tumour microenvironment.

Molecular Mechanisms and Potential Therapeutic Reversal of Pancreatic Cancer-Induced Immune Evasion

Pancreatic cancer ranks high among the causes of cancer-related mortality. The prognosis of this grim condition has not improved significantly over the past 50 years, despite advancement in imaging techniques, cancer genetics and treatment modalities. Due to the relative difficulty in the early detection of pancreatic tumors, as low as 20% of patients are eligible for potentially curative surgery; moreover, chemotherapy and radiotherapy (RT) do not confer a great benefit in the overall survival of the patients. Currently, emerging developments in immunotherapy have yet to bring a significant clinical advantage among pancreatic cancer patients. In fact, pancreatic tumor-driven immune evasion possesses one of the greatest challenges leading to immunotherapeutic resistance. Most of the immune escape pathways are innate, while poor priming of hosts' immune response and immunoediting constitute the adaptive immunosuppressive machinery. In this review, we extensively discuss the pathway perturbations undermining the anti-tumor immunity specific to pancreatic cancer. We also explore feasible up-and-coming therapeutic strategies that may restore immunity and address therapeutic resistance, bringing hope to eliminate the status quo in pancreatic cancer prognosis.

Durvalumab With or Without Tremelimumab for Patients With Metastatic Pancreatic Ductal Adenocarcinoma: A Phase 2 Randomized Clinical Trial

Importance

New therapeutic options for patients with metastatic pancreatic ductal adenocarcinoma (mPDAC) are needed. This study evaluated dual checkpoint combination therapy in patients with mPDAC.

Objective

To evaluate the safety and efficacy of the anti-PD-L1 (programmed death-ligand 1) antibody using either durvalumab monotherapy or in combination with the anticytotoxic T-lymphocyte antigen 4 antibody using durvalumab plus tremelimumab therapy in patients with mPDAC.

Design, Setting, and Participants

Part A of this multicenter, 2-part, phase 2 randomized clinical trial was a lead-in safety, open-label study with planned expansion to part B pending an efficacy signal from part A. Between November 26, 2015, and March 23, 2017, 65 patients with mPDAC who had previously received only 1 first-line fluorouracil-based or gemcitabine-based treatment were enrolled at 21 sites in 6 countries. Efficacy analysis included the intent-to-treat population; safety analysis included patients who received at least 1 dose of study treatment and for whom any postdose data were available.

Interventions

Patients received durvalumab (1500 mg every 4 weeks) plus tremelimumab (75 mg every 4 weeks) combination therapy for 4 cycles followed by durvalumab therapy (1500 mg every 4 weeks) or durvalumab monotherapy (1500 mg every 4 weeks) for up to 12 months or until the onset of progressive disease or unacceptable toxic effects.

Main Outcomes and Measures

Safety and efficacy were measured by objective response rate, which was used to determine study expansion to part B. The threshold for expansion was an objective response rate of 10% for either treatment arm.

Results

Among 65 randomized patients, 34 (52%) were men and median age was 61 (95% CI, 37-81) years. Grade 3 or higher treatment-related adverse events occurred in 7 of 32 patients (22%) receiving combination therapy and in 2 of 32 patients (6%) receiving monotherapy; 1 patient randomized to the monotherapy arm did not receive treatment owing to worsened disease. Fatigue, diarrhea, and pruritus were the most common adverse events in both arms. Overall, 4 of 64 patients (6%) discontinued treatment owing to treatment-related adverse events. Objective response rate was 3.1% (95% CI, 0.08-16.22) for patients receiving combination therapy and 0% (95% CI, 0.00-10.58) for patients receiving monotherapy. Low patient numbers limited observation of the associations between treatment response and PD-L1 expression or microsatellite instability status.

Conclusion and Relevance

Treatment was well tolerated, and the efficacy of durvalumab plus tremelimumab therapy and durvalumab monotherapy reflected a population of patients with mPDAC who had poor prognoses and rapidly progressing disease. Patients were not enrolled in part B because the threshold for efficacy was not met in part A.

Trial Registration

ClinicalTrials.gov identifier: NCT02558894.

An update on treatment options for pancreatic adenocarcinoma

Pancreatic cancer is one of the most lethal solid organ tumors. Due to the rising incidence, late diagnosis, and limited treatment options, it is expected to be the second leading cause of cancer deaths in high income countries in the next decade. The multidisciplinary treatment of this disease depends on the stage of cancer at diagnosis (resectable, borderline, locally advanced, and metastatic disease), and combines surgery, chemotherapy, chemoradiotherapy, and supportive care. The landscape of multidisciplinary pancreatic cancer treatment is changing rapidly, especially in locally advanced disease, and the number of treatment options in metastatic disease, including personalized medicine, innovative targets, immunotherapy, therapeutic vaccines, adoptive T-cell transfer, or stemness inhibitors, will probably expand in the near future. This review summarizes the current literature and provides an overview of how new therapies or new therapeutic strategies (neoadjuvant therapies, conversion surgery) will guide multidisciplinary disease management, future clinical trials, and, hopefully, will increase overall survival.

Paradigm Shifting of Systemic Chemotherapy for Unresectable Pancreatic Cancer in Japan

Systemic chemotherapy plays an important role in the treatment of pancreatic cancer, to improve the survival of patients with pancreatic cancer. Unresectable pancreatic cancer can be classified into three categories: metastatic, locally advanced, and hereditary pancreatic cancers. Furthermore, the second-line chemotherapy is required to prolong the survival. The combined regimens of oxaliplatin, irinotecan, fluorouracil and leucovorin (FOLFIRINOX) and gemcitabine plus nab-paclitaxel (GEM plus nab-PTX) have been recognized as the standard of care for advanced pancreatic cancer. However, the consensus of selection of the first-line chemotherapy still remains. Randomized controlled trials (RCTs) between FOLFIRINOX and GEM plus nab-PTX are ongoing for locally advanced and metastatic disease in Japan, respectively. Hereditary pancreatic cancer, especially associated with BRCA mutations, is responsive to platinum-containing regimens and/or poly (ADP-ribose) polymerase (PARP) inhibitors. It is becoming more important to examine the presence/absence of BRCA mutations to select the appropriate treatment strategy for individual patients. Although some S-1-based regimens have been investigated in the second-line treatment after GEM-based chemotherapy in Japan, no regime demonstrated survival benefit. Nanoliposomal irinotecan (nal-IRI) plus FF has been established as the standard of care in the second-line treatment in a global phase III trial (NAPOLI-1). A randomized phase II trial comparing FF plus nal-IRI with FF alone was also conducted in Japan to examine the efficacy and safety of the FF plus nal-IRI in Japanese patients.

Systemic treatment of pancreatic cancer revisited

Pancreatic cancer is considered to be one of the most aggressive cancers. For unknown reasons, the incidence of pancreatic cancer is slowly rising and so too are mortality rates. Over 75% of patients are diagnosed with locally advanced disease or with metastases; and more than 95% of patients have metastases at diagnosis or will develop metastases during their follow-up. Despite recent improvements in the therapy of pancreatic cancer, initially with demonstration of the activity of the FOLFIRINOX regimen and subsequently the approval of nab-paclitaxel in combination with gemcitabine, prognosis remains poor and the 5-year survival rate is less than 5%. To date, neither personalized medicine nor immunotherapy, the 2 recent revolutions of cancer treatment, have delivered major positive results in the treatment of pancreatic cancer; and it is especially clear that immune checkpoint inhibitors will not become a major tool in the treatment of pancreatic cancer. There are many ongoing studies, including those exploring combinations of chemotherapy with immunotherapy. Vaccines or T cells modified with a chimeric antigen receptor (CAR-T cells) could also play a role in the treatment of cancer in the future. The aim of this review is to discuss recent improvements in standard of care, major obstacles to overcome, recent results of new treatment combinations, and the most interesting innovative approaches.