Major progress has been made toward our understanding of the programmed death-1/programmed death ligand-1 (PD-1/PD-L1) pathway (referred to as the PD pathway). mAbs are already being used to block ...the PD pathway to treat human cancers (anti-PD therapy), especially advanced solid tumors. This therapy is based on principles that were discovered through basic research more than a decade ago, but the great potential of this pathway to treat a broad spectrum of advanced human cancers is just now becoming apparent. In this Review, we will briefly review the history and development of anti-PD therapy, from the original benchwork to the most up-to-date clinical results. We will then focus the discussion on three basic principles that define this unique therapeutic approach and highlight how anti-PD therapy is distinct from other immunotherapeutic approaches, namely tumor site immune modulation, targeting tumor-induced immune defects, and repairing ongoing (rather than generating de novo) tumor immunity. We believe that these fundamental principles set the standard for future immunotherapies and will guide our efforts to develop more efficacious and less toxic immune therapeutics to treat human cancers.
Harnessing an antitumor immune response has been a fundamental strategy in cancer immunotherapy. For over a century, efforts have primarily focused on amplifying immune activation mechanisms that are ...employed by humans to eliminate invaders such as viruses and bacteria. This “immune enhancement” strategy often results in rare objective responses and frequent immune-related adverse events (irAEs). However, in the last decade, cancer immunotherapies targeting the B7-H1/PD-1 pathway (anti-PD therapy), have achieved higher objective response rates in patients with much fewer irAEs. This more beneficial tumor response-to-toxicity profile stems from distinct mechanisms of action that restore tumor-induced immune deficiency selectively in the tumor microenvironment, here termed “immune normalization,” which has led to its FDA approval in more than 10 cancer indications and facilitated its combination with different therapies. In this article, we wish to highlight the principles of immune normalization and learn from it, with the ultimate goal to guide better designs for future cancer immunotherapies.
This Perspective discusses the concept of immune normalization and how its underlying principles may help to augment, as well as design, cancer immunotherapies.
The immune suppressive molecule programmed death-1 (PD-1) is upregulated in activated T lymphocytes and inhibits T-cell function upon binding to its ligands B7-H1 (PD-L1, CD274) and B7-DC (PD-L2, ...CD273). Substantial experimental data from in vitro cell culture systems and animal models, and more recently from clinical trials, indicate that PD-1/PD-1-ligand interactions are a major mechanism of immune suppression within the tumor microenvironment. Initial clinical studies of antibodies directed against PD-1 and B7-H1 showed both an encouraging safety profile and remarkable antitumor activity in subsets of patients with metastatic disease, including malignancies--such as lung cancer--which were previously thought to be unresponsive to immunotherapy. Preliminary data have suggested a correlation between tumor membrane B7-H1 expression and clinical response to anti-PD-1 antibodies. Several key challenges remain to optimize development of PD-1/B7-H1 pathway blockade, including defining the biologic significance of all potential ligand-receptor interactions in the tumor microenvironment, developing more accurate predictive biomarkers of response, determining the breadth of activity in human malignancies, and developing rational combinations of therapy that address key mechanisms involved in positive and negative regulation of antitumor immune responses.
PD-L1 and PD-1 (PD) pathway blockade is a highly promising therapy and has elicited durable antitumor responses and long-term remissions in a subset of patients with a broad spectrum of cancers. How ...to improve, widen, and predict the clinical response to anti-PD therapy is a central theme in the field of cancer immunology and immunotherapy. Oncologic, immunologic, genetic, and biological studies focused on the human cancer microenvironment have yielded substantial insight into this issue. Here, we focus on tumor microenvironment and evaluate several potential therapeutic response markers including the PD-L1 and PD-1 expression pattern, genetic mutations within cancer cells and neoantigens, cancer epigenetics and effector T cell landscape, and microbiota. We further clarify the mechanisms of action of these markers and their roles in shaping, being shaped, and/or predicting therapeutic responses. We also discuss a variety of combinations with PD pathway blockade and their scientific rationales for cancer treatment.
Immune-checkpoint inhibitors (ICI), particularly inhibitors of the PD-1 axis, have altered the management of non-small cell lung cancer (NSCLC) over the last 10 years. First demonstrated to improve ...outcomes in second-line or later therapy of advanced disease, ICIs were shown to improve overall survival compared with chemotherapy in first-line therapy for patients whose tumors express PD-L1 on at least 50% of cells. More recently, combining ICIs with chemotherapy has been shown to improve survival in patients with both squamous and nonsquamous NSCLC, regardless of PD-L1 expression. However, PD-L1 and, more recently, tumor mutational burden have not proven to be straightforward indicative biomarkers. We describe the advances to date in utilizing these biomarkers, as well as novel markers of tumor inflammation, to ascertain which patients are most likely to benefit from ICIs. Ongoing translational work promises to improve the proportion of patients who benefit from these agents.
Immune evasion is an important hallmark of cancer, and a better understanding of this mechanism is essential for the development of effective strategies against cancer. The B7 homolog 1 ...(B7-H1)/programmed cell death 1 (PD-1) pathway has been demonstrated as a major mechanism of immune evasion in tumor site, and its blockade therapy shows very encouraging results in clinical trials. Inducible B7-H1 expression in tumor microenvironment is complex, with multidimensional interactions and expression by different subsets of hematopoietic and nonhematopoietic cells. Understanding these interactions and how tumors take advantage of this pathway can help us design future strategies for better therapeutic efficacy and to overcome resistances.
Results from the first-in-human phase I trial of the anti-programmed death-1 (PD-1) antibody BMS-936558 in patients with treatment-refractory solid tumors, including safety, tolerability, ...pharmacodynamics, and immunologic correlates, have been previously reported. Here, we provide long-term follow-up on three patients from that trial who sustained objective tumor regressions off therapy, and test the hypothesis that reinduction therapy for late tumor recurrence can be effective.
Three patients with colorectal cancer, renal cell cancer, and melanoma achieved objective responses on an intermittent dosing regimen of BMS-936558. Following cessation of therapy, patients were followed for more than 3 years. A patient with melanoma who experienced a prolonged partial regression followed by tumor recurrence received reinduction therapy.
A patient with colorectal cancer experienced a complete response, which is ongoing after 3 years. A patient with renal cell cancer experienced a partial response lasting 3 years off therapy, which converted to a complete response, which is ongoing at 12 months. A patient with melanoma achieved a partial response that was stable for 16 months off therapy; recurrent disease was successfully treated with reinduction anti-PD-1 therapy.
These data represent the most prolonged observation to date of patients with solid tumors responding to anti-PD-1 immunotherapy and the first report of successful reinduction therapy following delayed tumor progression. They underscore the potential for immune checkpoint blockade with anti-PD-1 to reset the equilibrium between tumor and the host immune system.
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