MEDI 4736 (durvalumab) in non-small cell lung cancer

Introduction: Immune checkpoint inhibitors (ICI) are now a therapeutic option for advanced non-small cell lung cancer (NSCLC) patients. ICI, such as the PD-1 inhibitors nivolumab and pembrolizumab and the PD-L1 inhibitor atezolizumab, have already been marketed for the treatment of pretreated patients with advanced NSCLC. Other notable PD-L1 inhibitors under development include avelumab and durvalumab.

Areas covered: This article reviews literature on durvalumab development, from the preclinical data to the results of phase III clinical trials, whether published or presented at international scientific conferences. Ongoing clinical trials were also reviewed.

Expert opinion: Early phase trials of durvalumab monotherapy (and in combination) have demonstrated activity in advanced NSCLC patients and it has demonstrated a good safety profile. The authors believe that durvalumab will likely play an important role in future treatment strategies for NSCLC. The PACIFIC trial assessing durvalumab after standard chemoradiotherapy for locally advanced NSCLC has already met its primary endpoint and the potential of durvalumab will be reinforced if phase III randomized studies of first-line (MYSTIC trial) and second or subsequent (ARCTIC trial) lines of therapy demonstrate superiority over the current standard of care.     

The role of checkpoint inhibitors immunotherapy in advanced non-small cell lung cancer in the elderly

Introduction: Immune checkpoint inhibition is a novel treatment modality that has brought a new hope to patients with advanced NSCLC. Several molecules targeting cytotoxic T-lymphocyte antigen 4 (CTLA4) or programmed cell death 1 receptor/programmed death ligand-1 (PD1/PD-L1) pathways are under evaluation in NSCLC and three of them are currently approved: nivolumab and atezolizumab for advanced NSCLC after prior chemotherapy and pembrolizumab for advanced NSCLC expressing PD-L1 ≥ 1% after at least one prior chemotherapy regimen and > 50% as a first-line response.

Areas covered: To date, the efficacy and toxicity of immune checkpoint inhibitors in the elderly is unclear because available studies involved mainly a low number of elderly patients. In this paper, the authors discuss the frailty of the elderly patient and the challenges of choosing the best therapeutic strategy, focusing on the role of immune checkpoint inhibitors.

Expert opinion: There are several outstanding goals that need to be met for the proper and safe use of immunotherapeutic drugs. In terms of the elderly, it is true that age-tailored clinical trials are needed to confirm the real impact of immunotherapy and harmonize the standard of care in this specific demographic.     

Pembrolizumab for the treatment of non-small cell lung cancer

ABSTRACT

Introduction: Immune checkpoint inhibitors targeting programmed death protein 1 (PD-1) receptor and its ligand, PD-L1, have recently led to significant and durable improvements in the clinical outcomes of some types of cancers including lung cancer.

Areas covered: Pembrolizumab was approved by the US FDA for the treatment of advanced or metastatic NSCLC whose disease has progressed after other treatments and with tumors that express PD-L1. In the phase I KEYNOTE-001 trial, the overall response rate (ORR) was 19.4%, the median progression-free survival (PFS) and overall survival (OS) were 3.7 months and 12.0 months for 495 unselected NSCLC patients. Strong PD-L1 expression (≥ 50%) was associated with higher ORR, longer PFS, and longer OS. The phase II/III randomized KEYNOTE-010 trial demonstrated that pembrolizumab improved OS versus docetaxel in patients with previously treated NSCLC.

Expert opinion: Pembrolizumab, demonstrated durable response and prolonged OS especially in NSCLC patients with high expression of PD-1, thereby suggests a new treatment paradigm. However, many issues remain to be explored, including the identification of other robust biomarkers that can accurately predict the immune-responsiveness of tumors. Along with the identification of predictive biomarkers, further understanding of the tumor microenvironment is necessary to improve treatment outcomes through combinations of immunotherapy or combined with other targeted therapies.     

Nivolumab for treating non-small cell lung cancer

Introduction: Diversion of the immune checkpoint PD-1/PD-L1 by a tumor in order to escape antitumor immunity is a hallmark of NSCLC, but offers promising new strategies. Nivolumab, a fully human monoclonal antibody, is the first PD-1 inhibitor to be approved to treat metastatic NSCLC after exciting results obtained from clinical trials.

Areas covered: This review aims to:) clarify the mechanism of action and toxicities of PD-1 inhibitors; recapitulate the results from various clinical trials that have evaluated nivolumab as a monotherapy for metastatic NSCLC; discuss the clinical and translational research axes to better use this molecule; and summarize the therapeutic combinations currently under evaluation.

Expert opinion: The contribution of this molecule to treat NSCLC is undeniable, making it a new standard of care after prior chemotherapy. Its toxicity profile is favorable but a good knowledge of new and potentially severe immune-related adverse effects such as endocrinopathy or interstitial pneumonitis is essential for its early detection and management. Better selection of patients is needed, particularly based on the discovery of predictive biomarkers, such as PD-L1 expression. Multiple associations with other checkpoint inhibitors, chemotherapy and targeted therapies are currently being studied and should pave the way toward new uses for this drug.     

晚期非小细胞肺癌免疫治疗进展

肺癌是我国最常见的恶性肿瘤之一,其中非小细胞肺癌(NSCLC)约占85%,且大部分NSCLC患者在确诊时疾病已进展至晚期,病死率较高。近年来,临床对于晚期NSCLC的治疗已从传统的手术治疗、化学治疗、放射治疗、靶向治疗走向了免疫治疗。免疫检查点抑制剂(ICIs)治疗晚期NSCLC体现出了良好的抗肿瘤活性,尤其体现在细胞毒性T淋巴细胞相关抗原-4(CTLA-4)、程序性死亡受体-1(PD-1)、程序性死亡配体-1(PD-L1)抑制剂。基于此,本文将重点综述CTLA-4、PD-1、PD-L1抑制剂在晚期NSCLC中的治疗进展,以期提高患者的临床获益率,为临床选择合理治疗方案提供参考。     

Nivolumab for the treatment of bladder cancer

Introduction: The checkpoint inhibitor nivolumab has recently demonstrated effectiveness against metatstatic urothelial carcinoma. Nivolumab is a fully human monoclonal antibody blocking PD-1 and thereby enhancing antitumour immune mechanisms.

Areas covered: In this review, the authors describe the treatment of metastatic bladder cancer with nivolumab against the background of the standard treatment with cisplatin-based chemotherapy which can prolong overall survival from 3–6 months in untreated cases to over one year. Different combinations of cisplatin-based chemotherapy can further prolong survival by only a few months. The authors highlight that cancer immunotherapy by checkpoint inhibition offers potential to further prolong patient survival with limited and well manageable toxicity although serious immune-related adverse events may occur.

Expert opinion: The response rate to nivolumab and other checkpoint inhibitors after first line chemotherapy remains under 30%. Patients unfit for cisplatin may benefit from first-line cancer immunotherapy. It is unclear which patients will respond and PD-1/PD-L1 expression alone is not a sufficiently reliable response marker. Treatment costs are extreme and further trials will have to clarify which subset of patients in which context of management will have a substantial benefit.     

Programmed death-1 checkpoint blockade in acute myeloid leukemia

Introduction: Immune checkpoints are regulatory pathways induced in activated T lymphocytes that regulate antigen responsiveness. These immune checkpoints are hijacked by tumors to promote dysfunction of anti-tumor effector cells and consequently of tumor escape from the host immune system.

Areas covered: Programmed death-1/programmed death ligand (PD-1/PDL-1), a checkpoint pathway, has been extensively investigated in leukemia mouse models. Expression of PD-1 on the surface of activated immune cells and of its ligands, PD-L1 and PD-L2, on leukemic blasts has been documented. Clinical trials with PD-1 inhibitors in patients with hematological malignancies are ongoing with promising clinical responses.

Expert opinion: Therapy of hematological cancers with antibodies blocking inhibitory receptors is expected to be highly clinically effective. Checkpoint inhibitory receptors and their ligands are co-expressed on hematopoietic cells found in the leukemic milieu. Several distinct immunological mechanisms are likely to be engaged by antibody-based checkpoint blockade. Co-expression of multiple inhibitory receptors on hematopoietic cells offers an opportunity for combining blocking antibodies to achieve more effective therapy. Up-regulation of receptor/ligand expression in the leukemic milieu may provide a blood marker predictive of response. Finally, chemotherapy-induced up-regulation of PD-1 on T cells after conventional leukemia therapy creates a solid rationale for application of checkpoint blockade as a follow-up therapy.     

Pembrolizumab for the treatment of diffuse large B-cell lymphoma

ABSTRACT

Introduction: Pembrolizumab is a novel monoclonal antibody that targets the interaction between programmed cell death protein 1 (PD-1) and its ligand (PD-L1). Pembrolizumab has shown significant clinical efficacy in Hodgkin Lymphoma (HL), but results in non Hodgkin Lymphoma (NHL) are mixed. Some NHL subtypes, which share certain genetic features with HL, such as alterations in chromosome 9p24.1 and expression of PD-L1, have shown promising responses in early phase trials.

Areas covered: In this review, we provide an overview of pembrolizumab as a compound, and present the available clinical efficacy and safety data in the treatment of diffuse large B cell lymphomas.

Expert opinion: Current early phase data suggest that single agent pembrolizumab in NHL demonstrates both efficacy and a favorable safety profile. However, it is anticipated that future treatment strategies will be biomarker-driven and incorporate pembrolizumab into combination therapies with chemotherapy and/or immunotherapy agents.     

Ramucirumab for the treatment of advanced or metastatic non-small cell lung cancer

ABSTRACT

Introduction: On 12 December 2014, the U.S. Food and Drug Administration (FDA) approved ramucirumab for use in combination with docetaxel for the treatment of patients with metastatic non-small cell lung cancer (NSCLC) with disease progression on or after platinum-based chemotherapy.

Areas covered: This review discusses the best treatment strategy for ramucirumab, a vascular endothelial growth factor receptor-2 inhibitor for patients with advanced NSCLC.

Expert opinion: The addition of ramucirumab to docetaxel in the treatment of patients with metastatic NSCLC who have progressed on or after platinum-based chemotherapy confers a 1.4-month improvement in overall survival, with an acceptable toxicity profile. The potential impact of the approval of the programmed death receptor-1 (PD-1)-blocking antibody nivolumab or pembrolizumab on the use of ramucirumab plus docetaxel in advanced NSCLC patient population is uncertain in clinical practice. In order to improve overall outcomes for patients with advanced NSCLC, both ramucirumab plus docetaxel and the PD-1-blocking antibody should be used in any treatment line.     

Immune checkpoint inhibition for the treatment of mesothelioma

Introduction: Combination chemotherapy is currently standard care for advanced mesothelioma. Checkpoint blockade is a promising new treatment.

Areas covered: This review covers clinical use and biomarkers of checkpoint blockade. Medline search used keywords ‘mesothelioma’ combined with ‘checkpoint blockade’ OR ‘PD-L1? OR ‘PD1? OR ‘anti-CTLA4?; the search terms AND ‘clinical trial’ or AND ‘biomarker*’ were added. Handsearching covered abstracts from relevant meetings from 2016 to 2018 and reference lists. Data informed a narrative review.

Expert Opinion: Single agent anti-CTLA4 blockade is inactive in mesothelioma. Single agent PD-1 blockade as second or subsequent treatment gives 20–29% partial responses; no randomized comparisons against placebo or chemotherapy are available. Biomarkers of response have been difficult to identify. There is no consensus as to whether tumor PD-L1 expression predicts outcomes. Combination checkpoint inhibitors (CTLA4 and PD1 blockade) provide a small incremental increase in response rates and progression-free survival. Chemoimmunotherapy is the next frontier.     

Immunotherapy of non-small cell lung cancer: report from an international experts panel meeting of the Italian association of thoracic oncology

ABSTRACT

Introduction: The potential long term survival gain, related to immune adaptability and memory, the potential activity across multiple tumour types through targeting the immune system, and the opportunity for combinations offered by the unique mechanism of actions and safety profile of these new agents, all support the role of immunotherapy in the cancer treatment pathway or paradigm.

Areas covered: The authors discuss the recent advances in the understanding of immunology and antitumor immune responses that have led to the development of new immunotherapies, including monoclonal antibodies that inhibit immune checkpoint pathways, such as Programmed Death-1 (PD-1) and Cytotoxic T-Lymphocyte-Associated Antigen 4 (CTLA-4). Currently, two PD-1 inhibitors are available in clinical practice for treatment of advanced non-small cell lung cancer (NSCLC): nivolumab and pembrolizumab.

Expert opinion: Ongoing research will dictate future strategies, including the potential incorporation of immunotherapy in stage dependent treatment settings (early stage locally advanced disease and first line therapy for metastatic disease). Immunotherapy combinations are promising avenues, and careful selection of patients, doses of each agent and information supporting strategies (i.e. concomitant or sequential) is still needed.     

Optimizing Patient Selection to Maximize Drug Efficacy: the Expanding Role of Pharmacogenomics in the Clinical Development of Pembrolizumab for the Treatment of Non-small Cell Lung Cancer

Pembrolizumab (MK-3475) is a potent and highly selective humanized monoclonal antibody of the immunoglobulin G4κ class directed against the immune checkpoint programmed cell death protein-1 (PD-1). Binding to PD-1 prevents its interaction with natural ligands and allows for the reactivation of the immune response against cancer cells. The list of approved indications of pembrolizumab is fast expanding, including its use as first-line treatment of metastatic non–small cell lung cancer (NSCLC), which is a complex and evolving disease. Pharmacogenomics significantly contributed to understanding this complexity, allowing for the identification of molecular biomarkers and novel pharmacologic targets. This approach has delivered more effective and less toxic drugs for advanced NSCLC. In our opinion, pharmacogenomics played a key role in the approval of pembrolizumab as frontline therapy for NSCLC with high expression of the PD-1 ligand, which occurs in ∼30% of patients. Moreover, an analysis conducted on the ongoing clinical trials sponsored by the drug's patent holder shows that the characterization and validation of additional pharmacogenomic biomarkers of response has the potential to extend the frontline clinical use of pembrolizumab in NSCLC.     

PD-1 checkpoint blockade alone or combined PD-1 and CTLA-4 blockade as immunotherapy for lung cancer?

Introduction: Signaling through T-cell surface, an immune checkpoint protein such as PD-1 or CTLA-4 helps dampen or terminate unwanted immune responses. Blocking a single immune checkpoint or multiple checkpoints simultaneously can generate anti-tumor activity against a variety of cancers including lung cancer.

Area covered: This review highlights the results of recent clinical studies of single or combination checkpoint inhibitor immunotherapy in non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC). The authors discuss pembrolizumab and pembrolizumab plus ipilimumab, durvalumab and durvalumab plus tremelimumab, nivolumab and nivolumab plus ipilimumab for NSCLC as well as nivolumab and nivolumab plus ipilimumab for SCLC.

Expert opinion: Available data suggest that, in both metastatic NSCLC and SCLC, combined PD-1 and CTLA-4 blockade may produce a higher tumor response rate than PD-1 blockade alone. Nevertheless, combination therapy is associated with an increased toxicity. Several larger-scale studies are currently ongoing. For checkpoint inhibitor immunotherapy in SCLC and NSCLC, combination therapy is associated with a higher incidence of toxicities than single therapy; however, it appears to help increase tumor response rate. The increased response rate, if confirmed in larger scale studies, will likely make combination therapy another useful therapeutic approach for lung cancer.     

Recent developments with immunotherapy for hepatocellular carcinoma

Introduction: Immunotherapy is on the way to become the new standard of care for advanced hepatocellular carcinoma (HCC) worldwide. With higher rates of objective responses, and overall less side effects compared to tyrosine-kinase inhibitors (TKIs) immunotherapeutics will probably replace sorafenib from standard first-line treatment.

Areas covered: This review covers recent clinical data on systemic agents and ongoing trials in patients with advanced HCC focusing on immunotherapy.

Expert opinion: In unselected patients with advanced HCC immunotherapeutics, namely the programmed cell death-1 (PD-1) antibodies, nivolumab and pembrolizumab have shown promising efficacy in therapy-naïve, as well as pre-treated patients with advanced HCC. However, only 10–20 percent of treated patients show an objective and durable response to the indicated therapeutics. Therefore, combination therapies including different immunotherapeutics, e.g. PD-1/programmed cell death 1 ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies, or combinations of immunotherapeutics and small molecules, or bifunctional antibodies will be needed to improve response rates.

Abbreviations: HCC: hepatocellular carcinoma; TKI: tyrosine-kinase inhibitors; PD-1: programmed death receptor-1; PD-L1: programmed cell death 1 ligand 1; CTLA-4: cytotoxic T-lymphocyte-associated Protein 4; CAR-T: chimeric T cell receptors; TACE: transarterial chemoembolization; SIRT: selective internal radiation therapy; SBRT: stereotactic body radiation therapy; VEGF: vascular endothelial growth factor; MEK: mitogen-activated protein kinase kinase; NK cell: natural killer cell; TGFβ: transforming growth factor-β; OV: Oncolytic viruses; PFU: plaque-forming unit     

Prospects and progress of atezolizumab in non-small cell lung cancer

Introduction: Immunotherapy has recently come to the forefront of oncology treatment as a potential means of combating cancer by restoring the body’s adaptive cancer-immunity cycle. Atezolizumab is a monoclonal antibody agent that specifically targets programmed death ligand 1 (PD-L1), a key molecule in the cancer-immunity pathway, to block binding to its receptors PD-1 and B7.1.

Areas covered: This review covers the role of atezolizumab in the treatment of non-small-cell lung cancer (NSCLC). Several studies have reported promising efficacy in this indication. The phase II FIR and BIRCH studies evaluated atezolizumab monotherapy across different lines of therapy in NSCLC selected by PD-L1 expression status. The randomized POPLAR and OAK trials of atezolizumab versus docetaxel in previously treated NSCLC reported improved efficacy in the atezolizumab arm. Several ongoing studies yet to report data are also described and treatment-related adverse events are discussed.

Expert opinion: Clinical trials have shown that atezolizumab has a favorable risk-benefit ratio compared with standard chemotherapy in second-line treatment of non-oncogene-driven advanced NSCLC. Promising response rates and survival over 2 years has been reported in the first-line setting; however, more research is needed in this setting and in evaluating combinatorial strategies to treat NSCLC.     

Intralesional and systemic immunotherapy for metastatic melanoma

ABSTRACT

Introduction: Immunotherapy has revolutionized the treatment of metastatic melanoma and dramatically improved patient outcomes. Ipilimumab, an inhibitor of cytotoxic T-lymphocyte antigen-4 (CTLA-4), was the first immunotherapeutic agent to demonstrate improved survival in advanced melanoma. More recently, other immune checkpoint inhibitors, including the programmed death-1 (PD-1) inhibitors pembrolizumab and nivolumab, have demonstrated efficacy in locally advanced unresectable and metastatic melanoma. In addition to systemically delivered immunotherapies, intralesional therapies such as talimogene laherparepvec (TVEC) play an important role in the treatment of locoregionally advanced and metastatic melanoma.

Areas covered: This review provides an overview of the mechanisms behind immune checkpoint inhibitors. Clinical evidence of their efficacy is presented and discussion of new patterns of response and associated immune related adverse events associated with immunotherapy are provided.

Expert opinion: Treatment options for locally advanced and metastatic melanoma are expanding with new developments in immunotherapy and immune checkpoint inhibitors. The utility of these novel therapies in the adjuvant setting is currently being explored. The ideal treatment of metastatic melanoma continues to be multimodal, combining systemic treatments, intralesional and regional therapies, surgery and radiotherapy to achieve optimal outcomes.     

Immune checkpoint blockade as a potential therapeutic target in non-small cell lung cancer

ABSTRACT

Introduction: The recent emergence of immune checkpoint blockade therapy and the progression of immunobiology in cancer have spurred an increasing interest in the immunotherapy for advanced non-small cell lung cancer (NSCLC). Immune checkpoint inhibitors (ICIs), designed to directly target immune inhibitory molecules, have demonstrated efficacy in the treatment of patients with advanced NSCLC.

Areas covered: In the present article, the authors summarize the mechanism, efficacy and safety of major ICIs for the treatment of advanced or metastatic NSCLC. Combinations of different ICIs or conventional therapy and/or targeted agents for NSCLC treatment in clinical trials are also updated. In addition, immune-related adverse events and the roles of inhibitory immune checkpoint molecules as potential biomarkers in the immune checkpoint blockade therapy for NSCLC are emphatically elucidated.

Expert opinion: Immunotherapies targeting the immune checkpoint pathways have shown potential to generate durable responses and improve survival for NSCLC patients. Although the toxicity profile of this immunotherapy is manageable, immune-related adverse events and drug resistance may cause therapeutic failure. Therefore, a better understanding of the mechanisms underpinning its function and the potential side effects of ICIs, as well as the identification of predictive biomarkers for patient selection are essential.     

Efficacy and Safety of Programmed Cell Death 1 Inhibitor Monotherapy Versus Chemotherapy as Second-Line Treatment for Advanced Esophageal Cancer: A Meta-analysis and Systematic Review

PurposeWith programmed cell death 1 (PD-1) inhibitors approved for second-line treatment of advanced esophageal cancer, immunotherapy and chemotherapy have gradually become the main treatments for second-line treatment of patients with advanced esophageal cancer (AEC). This meta-analysis and systematic review were conducted to evaluate the efficacy and safety of PD-1 inhibitors monotherapy versus chemotherapy in second-line treatment of AEC.MethodsEligible randomized controlled trials were searched in PubMed, Embase, and the Cochrane Library and abstracts presented at the American Society of Clinical Oncology or European Society of Medical Oncology were reviewed to assess the efficacy and tolerability of PD-1/programmed cell death ligand 1 (PD-L1) inhibitors relative to chemotherapy for AEC from January 2016 to October 2020. Patients diagnosed with AEC and progressing after first-line therapy were included in this study. Hazard ratios (HRs) of progression-free survival (PFS) and overall survival (OS), risk ratios (RRs) of objective response rate (ORR), and the odds ratios (ORs) of adverse effects (AEs) were calculated.FindingsThe study included 4 randomized controlled trials with 1683 patients. The results indicated that PD-1 inhibitors prolonged the OS (HR = 0.79; 95% CI, 0.71–0.88; P < 0.01) and improved the ORR (RR = 3.00; 95% CI, 2.36–3.82; P = 0.01) but did not improve the PFS (HR = 0.96; 95% CI, 0.76–1.20; P = 0.692) compared with chemotherapy in the second-line treatment of AEC. PD-1 inhibitors alone were associated with a lower incidence of all treatment-related AEs (OR = 0.29; 95% CI, 0.09–0.89; P = 0.03) and grade 3 to 5 treatment-related AEs (OR = 0.26; 95% CI, 0.16–0.44; P < 0.01) versus chemotherapy. PD-1 inhibitors prolonged OS mainly in the following patient groups: male, age <65 years, Eastern Cooperative Oncology Group performance status of 1, or PD-L1 tumor proportion score ≥10%. Asian patients had a longer OS than non-Asian patients (P = 0.01).ImplicationsThe available evidence indicates that the efficacy and tolerability of PD-1 inhibitors were better than chemotherapy in the second-line treatment of AEC, and the benefiting population of these patients was limited to males, those <65 years of age, those with a Eastern Cooperative Oncology Group performance status of 1, or those with a PD-L1 tumor proportion score ≥10%. Notably, Asian patients receiving immune monotherapy had longer OS than non-Asian patients.     

Companion diagnostic assays for PD-1/PD-L1 checkpoint inhibitors in NSCLC

The immune checkpoint inhibitors pembrolizumab and nivolumab together with their diagnostic assays have recently been granted market authorization for treatment of advanced non-small-cell lung cancer in the USA. The two assays, PD-L1 IHC 22C3 pharmDx and PD-L1 IHC 28-8 pharmDx (both by Dako, Glostrup, Denmark), are the first PD-L1 IHC assays to obtain regulatory approval through the Premarket Approval process. This approval is supported by recent clinical studies that have shown a positive correlation between PD-L1 expression and the outcome following treatment with different PD-1/PD-L1 checkpoint inhibitors. These diagnostic assays are able to identify the group of non-small-cell lung cancer patients who will benefit most from treatment with the immune checkpoint inhibitors. However, so far, it is only the PD-L1 IHC 22C3 pharmDx assay, which is linked to the use of pembrolizumab, that has obtained regulatory status as a companion diagnostic.     

Diabetic ketoacidosis induced by a single dose of pembrolizumab

Immune checkpoint inhibitors are a new class of anticancer drugs recently approved by the US Food and Drug Administration (FDA) for the treatment of various malignancies. Pembrolizumab is an immune checkpoint inhibitor that targets the programmed cell death protein-1 (PD-1) receptor and blocks its interaction with programmed cell death ligand-1 (PD-L1) and programmed cell death ligand-2 (PD-L2). Pembrolizumab was first approved by the FDA in 2014 for the treatment of advanced melanoma and is currently approved for use in non-small cell lung cancer and several other neoplasms. Immune checkpoint inhibitors such as pembrolizumab have been reported to induce immune-mediated side effects, including type 1 diabetes mellitus in very rare cases (0.1% in clinical trials). Here, we report the case of a woman with no known history of diabetes who presented to our emergency department in a state of diabetic ketoacidosis within 3?weeks of receiving only a single dose of pembrolizumab therapy, and without any previous exposure to immunotherapy. This case of abrupt adult-onset type 1 diabetes mellitus is an example of the undesirable side effects that can emerge after only a brief exposure to an immune checkpoint inhibitor. Close monitoring of patients receiving immune checkpoint inhibitors is warranted for the early diagnosis and management of imminent and potentially life-threatening complications.