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.

Combination therapy for pancreatic cancer: anti-PD-(L)1-based strategy

Mortality associated with pancreatic cancer is among the highest of all malignancies, with a 5-year overall survival of 5-10%. Immunotherapy, represented by the blocking antibodies against programmed cell death protein 1 or its ligand 1 (anti-PD-(L)1), has achieved remarkable success in a number of malignancies. However, due to the immune-suppressive tumor microenvironment, the therapeutic efficacy of anti-PD-(L)1 in pancreatic cancer is far from expectation. To address such a fundamental issue, chemotherapy, radiotherapy, targeted therapy and even immunotherapy itself, have individually been attempted to combine with anti-PD-(L)1 in preclinical and clinical investigation. This review, with a particular focus on pancreatic cancer therapy, collects current anti-PD-(L)1-based combination strategy, highlights potential adverse effects of accumulative combination, and further points out future direction in optimization of combination, including targeting post-translational modification of PD-(L)1 and improving precision of treatment.

Immune checkpoints in targeted-immunotherapy of pancreatic cancer: New hope for clinical development

Immunotherapy has been recently considered as a promising alternative for cancer treatment. Indeed, targeting of immune checkpoint (ICP) strategies have shown significant success in human malignancies. However, despite remarkable success of cancer immunotherapy in pancreatic cancer (PCa), many of the developed immunotherapy methods show poor therapeutic outcomes in PCa with no or few effective treatment options thus far. In this process, immunosuppression in the tumor microenvironment (TME) is found to be the main obstacle to the effectiveness of antitumor immune response induced by an immunotherapy method. In this paper, the latest findings on the ICPs, which mediate immunosuppression in the TME have been reviewed. In addition, different approaches for targeting ICPs in the TME of PCa have been discussed. This review has also synopsized the cutting-edge advances in the latest studies to clinical applications of ICP-targeted therapy in PCa.

Trials and tribulations of pancreatic cancer immunotherapy

Immunotherapy has revolutionized cancer treatment in the last decade, and strategies to re-activate cytotoxic immunity are now standard of care in several malignancies. Despite rapid advances in immunotherapy for most solid cancers, progress in immunotherapy against pancreatic ductal adenocarcinoma (PDAC) has been exceptionally difficult. This is true for several approaches, most notably immune checkpoint inhibitors (ICIs) and GM-CSF cell-based vaccines (GVAX). Though many immunotherapies have been explored in clinical trials, few have shown significant therapeutic efficacy. Further, many have shown high rates of serious adverse effects and dose-limiting toxicities, and to date, immunotherapy regimens have not been successfully implemented in PDAC. Here, we provide a comprehensive summary of the key clinical trials exploring immunotherapy in PDAC, followed by a brief discussion of emerging molecular mechanisms that may explain the relative failure of immunotherapy in pancreas cancer thus far.

Precision Therapy of Pancreatic Cancer: From Bench to Bedside

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC), with a mortality rate of 94% and a 5-year-survival rate of only 8%, is one of the deadliest cancer entities worldwide, and early diagnostic methods as well as effective therapies are urgently needed.

SUMMARY

This review summarizes current clinical procedure and recent developments of oncological therapy in the palliative setting of metastatic PDAC. It further gives examples of successful, as well as failed, targeted therapy approaches and finally discusses promising ongoing research into the decade-old question of the "undruggability" of KRAS.

KEY MESSAGES

Bench-driven concepts change the clinical landscape from "one size fits all" towards precision medicine. With growing insight into the molecular mechanisms of pancreatic cancer the era of targeted therapy in PDAC is gaining a new momentum.