Pembrolizumab-Induced Pancytopenia: A Case Report

Clinical Characteristics and Outcomes of Pembrolizumab Induced Gastritis: A Systematic Review of the Literature

BACKGROUND

Pembrolizumab is associated with the development of gastritis, but its clinical features have not been characterized. To explore the clinical features of pembrolizumab induced gastritis and provide reference for the prevention and treatment of gastritis.

METHODS

Case reports and case series related to pembrolizumab induced gastritis were retrospectively analyzed by searching the database from inception to September 30, 2023.

RESULTS

Thirty-nine patients with gastritis entered the study with a median age of 63 years (range 34, 81). The median time to gastritis was 11.1 months (range 0.3, 60) and 7 cycles (range 1, 27) after administration. Epigastric pain (24 cases, 61.5%), nausea (17 cases, 43.6%), and vomiting (16 cases, 41.0%) were the most frequently complained symptoms. Esophagogastroduodenoscopy mainly showed erythematous (16 cases, 41.0%), hemorrhage (14 cases, 35.9%) and erosions (11 cases, 28.2%). Gastric mucosal biopsy shows chronic active gastritis with lymphocytic infiltration. These patients' symptoms and gastric mucosa improved or recovered after receiving systemic steroid and proton pump inhibitor therapy regardless of whether pembrolizumab was discontinued. These patients' symptoms and gastric mucosa improved or recovered after treatment with systemic steroids, proton pump inhibitors, and biological agents.

CONCLUSIONS

Gastritis is an extremely rare adverse effect of pembrolizumab. When patients receiving pembrolizumab complain of abdominal symptoms, endoscopy, tissue biopsy, and immunohistochemical staining should be actively performed for early identification and diagnosis of gastritis.

Case Report: Life-threatening pancytopenia with tislelizumab followed by cerebral infarction in a patient with lung adenocarcinoma

Immune checkpoint inhibitors (ICIs) are an integral antitumor therapy for many malignancies. Most patients show very good tolerability to ICIs; however, serious immune-related adverse events (irAEs) with ICIs have been well documented and prevent some patients from continuing ICIs or even become the direct cause of patient death. Cytopenia is a rare irAE but can be life-threatening. Here, we present the case of a 66-year-old male patient with metastatic lung adenocarcinoma who received two doses of chemotherapy + PD-1 antibody tislelizumab and developed pancytopenia after each dose. Although the first episode of pancytopenia resolved with a treatment regimen of granulocyte colony-stimulating factor (G-CSF), thrombopoietin (TPO), and red blood cell and platelet transfusion, the second episode showed extreme resistance to these treatments and improved only after the administration of steroids. His second pancytopenia episode resolved after a long course of treatment with methylprednisolone, G-CSF, TPO, hetrombopag and multiple red blood cell and platelet transfusions. However, he suffered a cerebral infarction when his platelet count was in the normal range and gradually recovered 1 week later. This case highlights the importance of the early recognition and management of hematological irAEs.

Antithymocyte globulin for aplastic anemia secondary to pembrolizumab: a case report and review of literature

Aplastic anemia is a rare but potentially serious complication of immune checkpoint inhibitor therapy. The authors present a case of pembrolizumab-induced aplastic anemia that was refractory to steroids but had some hematologic response to modified-dosing antithymocyte globulin (ATG). This is the first reported case of hematological response to ATG for immune checkpoint inhibitor-induced aplastic anemia and the first reported case of modified ATG dosing for this indication. Cases of immune checkpoint inhibitor-induced aplastic anemia and management options are also summarized. Given the high morbidity and mortality associated with ICI-induced aplastic anemia, more data is necessary to guide evidence-based management recommendations.

Current challenges of hematologic complications due to immune checkpoint blockade: a comprehensive review

Immune checkpoint blockade has demonstrated durable clinical benefits in a variety of malignancies. These immune checkpoint inhibitors (ICIs) produce unwanted autoimmune reactions due to an impaired self-tolerance. Hematologic immune-related adverse events (heme-irAEs) have been increasingly reported in the literature with a reported fatality rate of 12%. In this review, we illustrate 3 cases treated at Johns Hopkins Hospital for ICI-induced agranulocytosis, aplastic anemia, and thrombocytopenia. We then summarize the available evidence regarding the incidence and prevalence of heme-irAEs. We identified immune thrombocytopenia and hemolytic anemia as the most commonly reported heme-irAEs which are more commonly observed with nivolumab therapy. Median time to onset of heme-irAEs varies between patients but occurs earlier with CTLA-4 inhibitors than with anti-PD-L1/PD-1 agents. We also describe the current challenges regarding the recurrence of heme-irAEs despite immune checkpoint blockade termination. We provide the available evidence supporting a mixed T-cell and B-cell immune-mediated response. Finally, we review the treatment algorithm of these complications and provide treatment alternatives to steroid-refractory cases.

Management of Hematologic Adverse Events Associated With Immune Checkpoint Inhibitors

Immune checkpoint inhibitors target suppressor receptors, including cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed cell death ligand 1 (PD-L1). The activated T cells are not antigen specific; therefore, the blockade of the immune checkpoint may result in the development of autoimmune adverse events. The most common immune-related adverse events (irAEs) are rash, colitis, and endocrinopathies. However, irAEs that affect the hematologic system are rare and can affect red blood cells (e.g., autoimmune hemolytic anemia), white blood cells, and platelets (e.g., immune thrombocytopenia). Usually one cell line is affected; however, in some cases, multiple cell lines can be affected. Other changes in the hematologic system can also be affected (e.g., cryoglobulinemia, cytokine release syndrome). Due to the rarity and lack of recognition of these AEs, the timing, spectrum of events, and clinical presentation are poorly understood. Management of hematologic irAEs usually involves the use of steroids; however, other agents (e.g., IVIG, cyclosporine, rituximab) or procedures (e.g., plasma exchange, transfusions) can also be used.

Diagnosis and Management of Hematological Adverse Events Induced by Immune Checkpoint Inhibitors: A Systematic Review

There has been less volume of literature focusing on the Immune-related Hematological Adverse Drug Events (Hem-irAEs) of Immune Checkpoint Inhibitors (ICPis) in cancer patients. Furthermore, there has been no consensus about the management of hematological toxicity from immunotherapy in the recently published practice guidelines by the European Society for Medical Oncology (ESMO). We conducted a systematic review of case reports/series to describe the diagnosis and management of potentially rare and unrecognized Hem-irAEs. We searched Medline, OVID, Web of Science for eligible articles. Data were extracted on patient characteristics, Hem-irAEs, and management strategies. We performed quality assessment using the Pierson-5 evaluation scheme and causality assessment using the Naranjo scale. Our search retrieved 49 articles that described 118 cases. The majority of patients had melanoma (57.6%) and lung cancer (26.3%). The most common Hem-irAEs reported with ICPis (such as nivolumab, ipilimumab, and pembrolizumab) were thrombocytopenia, hemolytic and aplastic anemias. Less reported adverse events included agranulocytosis and neutropenia. Steroids were commonly used to treat these adverse events with frequent success. Other used strategies included intravenous immunoglobulins (IVIG), rituximab, and transfusion of blood components. The findings of this review provide more insights into the diagnosis and management of the rarely reported Hem-irAEs of ICPis.

Pembrolizumab-induced pancytopenia in a patient with squamous cell lung cancer

Immune checkpoint inhibitors (ICIs) are reportedly effective against many kinds of neoplasm, but may be responsible for several kinds of immune‐related adverse events (irAEs). Among these irAEs, the incidence of myelosuppression due to ICIs is relatively low. Corticosteroids are needed to control most cases of myelosuppression. Here, we report an 88‐year‐old woman with squamous cell lung cancer who was administered pembrolizumab. After five cycles of pembrolizumab, she developed severe pancytopenia. The pancytopenia improved under observation without steroid administration after cessation of pembrolizumab. During recovery from this irAE, the patient also maintained long‐term antitumor efficacy.

Key points

Significant findings of the study

There are several kinds of immune‐related adverse events. We encountered a case of pembrolizumab‐induced pancytopenia with squamous cell lung cancer.

What this study adds

Corticosteroids are needed to control most cases of myelosuppression induced by ICIs, but pancytopenia induced by pembrolizumab in our case improved without steroids.

Small Molecular Immune Modulators as Anticancer Agents

After decades of intense effort, immune checkpoint inhibitors have been conclusively demonstrated to be effective in cancer treatments and thus are revolutionizing the concepts in the treatment of cancers. Immuno-oncology has arrived and will play a key role in cancer treatment in the foreseeable future. However, efforts to find novel methods to improve the immune response to cancer have not ceased. Small-molecule approaches offer inherent advantages over biologic immunotherapies since they can cross cell membranes, penetrate into tumor tissue and tumor microenvironment more easily, and are amenable to be finely controlled than biological agents, which may help reduce immune-related adverse events seen with biologic therapies and provide more flexibility for the combination use with other therapies and superior clinical benefit. On the one hand, small-molecule therapies can modulate the immune response to cancer by restoring the antitumor immunity, promoting more effective cytotoxic lymphocyte responses, and regulating tumor microenvironment, either directly or epigenetically. On the other hand, the combination of different mechanisms of small molecules with antibodies and other biologics demonstrated admirable synergistic effect in clinical settings for cancer treatment and may expand antibodies' usefulness for broader clinical applications. This chapter provides an overview of small-molecule immunotherapeutic approaches either as monotherapy or in combination for the treatment of cancer.

Management of immune checkpoint inhibitor-related adverse events: A review of case reports

Immune checkpoint inhibitors represent a major breakthrough in cancer therapy. Immune‐related adverse events (irAEs) may occur during treatment due to their unique mechanism of action. Management of irAEs is based on clinical experience because it is not easy to conduct prospective trials to evaluate the best treatment strategy. Using a combination of search terms in the PubMed and Embase databases, we reviewed all cases in the English language citing toxicities associated with either pembrolizumab, nivolumab, ipilimumab, atezolizumab, tremelimumab, durvalumab, avelumab or any combination of these agents published before 20 May 2019. A total of 128 reports with 239 cases were included in the study. Here, we summarize the spectrum of toxicities, safety in special patients, rechallenging after irAEs and agents used for treatment of irAEs in those reports.

Toxicities associated with checkpoint inhibitors-an overview

Immunotherapy has an increasing role in the management of cancer, both in metastatic disease and as an adjuvant therapy. However, sensitization of the immune system with checkpoint inhibitors comes with a unique side effect profile. Full appreciation of this can take some time to emerge as some adverse events are rare, or can be subtle and potentially overlooked. Clinician awareness of these side effects can be particularly important in patients with pre-existing autoimmune conditions. Here we describe common symptoms and diagnostic strategies for organ-specific side effects of anti-CTLA-4 and anti-PD-1/PD-L1 immunotherapy agents.

Blocking the FSTL1-DIP2A Axis Improves Anti-tumor Immunity

Immune dysfunction is a strong factor in the resistance of cancer to treatment. Blocking immune checkpoint pathways is a promising approach to improve anti-tumor immunity, but the clinical efficacies are still limited. We previously identified follistatin-like 1 (FSTL1) as a determinant of immune dysfunction mediated by mesenchymal stromal/stem cells (MSCs) and immunoregulatory cells. Here, we demonstrate that blocking FSTL1 but not immune checkpoint pathways significantly suppresses cancer progression and metastasis in several mouse tumor models with increased MSCs. Expression of DIP2A (the receptor of FSTL1) in tumor cells is critical for FSTL1-induced immunoresistance. FSTL1/DIP2A co-positivity in tumor tissues correlates with poor prognosis in NSCLC patients. Thus, breaking the FSTL1-DIP2A axis may be a useful strategy for successfully inducing anti-tumor immunity.

Pancytopenia And Limbic Encephalopathy Complicating Immunotherapy For Clear Cell Endometrial Cancer With Microsatellite Instability-High (MSI-H)

BACKGROUND

Clear cell carcinoma of the endometrium (CCE) has a tendency to occur in a mismatch repair protein deficient molecular background. Treatment with immunotherapy can predict a favorable response.

CASE PRESENTATION

We are presenting a 53-year-old female, diagnosed with CCE 17 years ago, who was treated initially with hysterectomy and left salpingo-oophorectomy, who relapsed a few months later, and was then treated with left pelvic mass excision and sigmoidectomy. Recently, the disease recurred as a retroperitoneal lymphadenopathy, which was resected but then relapsed locally, spread to the lungs, and progressed further after three lines of chemotherapy. On pathological review of the tumor, it was found to harbor loss of nuclear expression of MLH-1 and PMS-2. Based on a strong predictor of response to immunotherapy, pembrolizumab was tried. However, within a few days of the single dose of pembrolizumab, immune thrombocytopenia followed by pancytopenia, recurrent seizures, visual hallucination, and cerebellar signs consistent with limbic encephalitis developed, which were not responding to steroid and intravenous immunoglobulin.

CONCLUSION

We are presenting a case of a CCE with deficient mismatch repair that developed two autoimmune side effects, pancytopenia and limbic encephalitis, within a few days of a single injection of pembrolizumab.

Efficacy and safety profiles of programmed cell death-1/programmed cell death ligand-1 inhibitors in the treatment of triple-negative breast cancer: A comprehensive systematic review

Triple-negative breast cancer (TNBC) is associated with worse prognosis, with limited treatment regiments available and higher mortality rate. Immune checkpoint inhibitors targeting programmed cell death-1 (PD-1) or programmed cell death-ligand 1 (PD-L1) showed great potentials in treating malignancies and may serve as potential therapies for TNBC. This systematic review aims to evaluate the efficacy and safety profiles of PD-1/PD-L1 inhibitors in the treatment of TNBC. Literature search was performed via PubMed, EBSCOhost, Scopus, and CENTRAL databases, selecting studies which evaluated the use of anti-PD-1/PDL1 for TNBC from inception until February 2019. Risk of bias was assessed by the Newcastle-Ottawa Scale (NOS). Overall, 7 studies evaluating outcomes of 1395 patients with TNBC were included in this systematic review. Anti-PD-1/PD-L1 showed significant antitumor effect, proven by their promising response (objective response rate (ORR), 18.5-39.4%) and survival rates (median overall survival (OS), 9.2-21.3 months). Moreover, anti- PD-1/PD-L1 yielded better outcomes when given as first-line therapy, and overexpression of PD-L1 in tumors showed better therapeutic effects. On the other hands, safety profiles were similar across agents and generally acceptable, with grade ≥3 treatment- related adverse effects (AEs) ranging from 9.5% to 15.6% and no new AEs were experienced by TNBC patients. Most grade ≥3 AEs are immune-mediated, which are manifested as neutropenia, fatigue, peripheral neuropathy, and anemia. PD-1/PD-L1 inhibitors showed promising efficacy and tolerable AEs, and thus may benefit TNBC patients. Further studies of randomized controlled trials with larger populations are needed to better confirm the potential of these agents.

Bone Marrow Findings of Immune-Mediated Pure Red Cell Aplasia Following Anti-Programmed Cell Death Receptor-1 Therapy: A Report of Two Cases and Review of Literature

Immune checkpoint inhibitors have recently emerged as important and effective advanced cancer treatment options. Programmed cell death receptor-1 (PD-1) antagonists such as pembrolizumab and nivolumab have been approved by the US Food and Drug Administration for treatment of many advanced cancers. As anti-PD-1 checkpoint inhibitor use has been increasing, previously unreported rare side effects emerge. These checkpoint inhibitors upregulate humoral and cellular immune responses to tumor antigens. Consequently, they can be associated with immune-related adverse events including hematological-related reactions such as autoimmune hemolytic anemia, immune thrombocytopenia, neutropenia and pancytopenia. However, pure red cell aplasia (PRCA) induced by anti-PD-1 checkpoint inhibitors is rarely reported in the literature. We herein report cases of two patients who developed PRCA during treatment with anti-PD-1 checkpoint inhibitors. In both cases, a peripheral blood smear examination demonstrated reticulocytopenia. Bone marrow biopsies revealed severe erythroid hypoplasia with maturation arrest at the proerythroblast stage, relative granulocytic hyperplasia and lymphocytosis. Flow cytometry and immunohistochemistry revealed that the lymphocytes were predominantly CD8⁺ T cells. T lymphocytosis, especially in one of the two patients, mimicked a T-cell lymphoproliferative disorder; lack of clonality indicated a reactive process. Our findings, in addition to data presented in the literature, suggest that T cells play a critical role in the pathogenesis of immune-related PRCA. PRCA is an under-recognized immune-mediated adverse event that does not manifest during the clinical trial phase. It is a potentially life-threatening complication, which should be considered in the differential diagnosis of anemia in patients treated with anti-PD-1 checkpoint inhibitors.

Safety and Tolerability of Immune Checkpoint Inhibitors (PD-1 and PD-L1) in Cancer

Immunotherapy has emerged in recent years and has revolutionized the treatment of cancer. Immune checkpoint inhibitors, including anti-cytotoxic T lymphocyte antigen-4 (CTLA-4), anti-programmed cell death-1 (PD-1) and anti-programmed cell death ligand-1 (PD-L1) agents, are the first of this new generation of treatments. Anti-PD-1/PD-L1 agents target immune cells by blocking the PD-1/PD-L1 pathway. This blockade leads to enhancement of the immune system and therefore restores the tumour-induced immune deficiency selectively in the tumour microenvironment. However, this shift in the balance of the immune system can also produce adverse effects that involve multiple organs. The pattern of toxicity is different from traditional chemotherapy agents or targeted therapy, and there is still little experience in recognizing and managing it. Thus, toxicity constitutes a real clinical management challenge and any new alteration should be suspected of being treatment-related. The most common toxicities occur in the skin, gastrointestinal tract, lungs, and endocrine, musculoskeletal, renal, nervous, haematologic, cardiovascular and ocular systems. Immune-mediated toxic effects are usually manageable, but toxicities may sometimes lead to treatment withdrawal, and even fulminant and fatal events can occur. Oncologists need to collaborate with internists, clinical immunologists and other specialists to understand, manage and prevent toxicity derived from immunotherapy. This review focuses on the mechanisms of toxicity of anti-PD-1/PD-L1 agents, and its diagnosis and management.

AIHA and Pancytopenia as Complications of Pembrolizumab Therapy for Metastatic Melanoma: A Case Report

Immunotherapy has been an emerging treatment for metastatic melanoma and several other malignancies since 2015. Hematological immune-mediated adverse effects from immunotherapy are rarely reported but they can cause serious harm to patients. Antibodies such as ipilimumab, nivolumab and pembrolizumab target different immune checkpoints to promote T cell anti-tumour response. In particular, pembrolizumab is an antibody that inhibits programmed cell death receptor 1 (PD-1) to upregulate tumour suppression. In this report, we present a case of pembrolizumab-induced autoimmune hemolytic anemia and pancytopenia in a patient who was receiving pembrolizumab treatment for metastatic melanoma. This patient has a history of chronic lymphocytic leukemia and was diagnosed with metastatic melanoma in 2017. He developed symptomatic AIHA and pancytopenia after receiving 8 cycles of pembrolizumab in 2018. Pembrolizumab treatment was discontinued and he was treated with blood transfusion and prednisone. After 5 months of tapering prednisone treatment, his anemia and pancytopenia have improved toward successful recovery. Cancer patients already face an increased risk of immunosuppression with conventional chemotherapy. This case report also summarized all reported cases of PD-1 inhibitor hematological adverse effects in the treatment of oncological diseases. These incidents reflect the risk of immune-mediated hematologic adverse effects, which should be considered in all patients using immunotherapy.

Haematological immune-related adverse events induced by anti-PD-1 or anti-PD-L1 immunotherapy: a descriptive observational study

BACKGROUND

Anti-programmed cell death 1 (PD-1) and anti-programmed cell death ligand 1 (PD-L1) antibodies are novel immunotherapies for cancer that can induce immune-related adverse events (irAEs). These adverse events can involve all organs, including the haemopoietic system. Thus far, haematological irAEs (haem-irAEs) have not been extensively characterised. This study aims to provide a comprehensive report of the haem-irAEs induced by anti-PD-1 or anti-PD-L1.

METHODS

In this descriptive observational study, we included consecutive patients aged at least 18 years with grade 2 or worse haem-irAEs induced by anti-PD-1 or anti-PD-L1 immunotherapy registered in three French pharmacovigilance databases: the Registre des Effets Indésirables Sévères des Anticorps Monoclonaux Immunomodulateurs en Cancérologie (REISAMIC; a prospective registry of patients treated with anti-PD-1 or anti-PD-L1 at a single centre), the ImmunoTOX committee of Gustave Roussy (a national referral database of suspected irAEs in patients treated with immunotherapy), and the registry of the Centre de Référence des Cytopénies Auto-Immunes de l'Adulte (CeReCAI; a national database of autoimmune cytopenias). Cases were reviewed by a central committee; adverse events had to be classed as certainly or probably related to anti-PD-1 or anti-PD-L1 therapy, and their severity was assessed according to the Common Terminology Criteria for Adverse Events (version 4.03). The primary endpoint was clinical description of haem-irAEs, as reported in all databases, and their frequency, as reported in the prospective REISAMIC registry.

FINDINGS

We screened 948 patients registered in the three databases from June 27, 2014, to June 29, 2018 (745 from REISAMIC, 190 from the ImmunoTOX committee, and 13 from CeReCAI). 35 patients (21 men and 14 women) with haem-irAEs related to anti-PD-1 or anti-PD-L1 were included in the study. Of 745 patients in the REISAMIC registry treated with anti-PD-1 or anti-PD-L1, four had haem-irAEs, giving a frequency of 0·5%. Median age in the 35 patients was 65 years (IQR 51-75), and the most common tumour types were melanoma (15 [43%] patients), non-small-cell lung cancer (12 [34%] patients), and lymphoma (four [11%] patients). 20 (57%) patients received nivolumab, 14 (40%) received pembrolizumab, and one (3%) received atezolizumab. Among the 35 patients, neutropenia, autoimmune haemolytic anaemia, and immune thrombocytopenia were the most common types of haem-irAE (each in nine patients [26%]), followed by pancytopenia or aplastic anaemia (five patients [14%]), bicytopenia (one patients with thrombocytopenia plus anaemia and one patient with neutropenia plus anaemia [6%]), and pure red cell aplasia (one patient [3%]). The maximum grade of severity was grade 2 in three (9%) patients, grade 3 in five (14%) patients, and grade 4 in 25 (71%) patients; two (6%) patients died from febrile neutropenia during haem-irAE related to anti-PD-1. Haem-irAEs resolved in 21 (60%) of the 35 patients.

INTERPRETATION

Haem-irAEs induced by PD-1 or PD-L1 inhibitors are rare but potentially life-threatening events. The most common clinical presentations are neutropenia, autoimmune haemolytic anaemia, immune thrombocytopenia, and aplastic anaemia. Investigations into earlier detection and better management are warranted.

FUNDING

Gustave Roussy and Gustave Roussy Immunotherapy Program.

Posttransfusion purpura with antibodies against human platelet antigen-4a following checkpoint inhibitor therapy: a case report and review of the literature

BACKGROUND

Posttransfusion purpura (PTP) is a rare condition characterized by severe thrombocytopenia following receipt of blood products. Most reported PTP cases involve alloantibodies directed against human platelet antigen (HPA)-1a. We present a case of PTP-mediated severe thrombocytopenia associated with alloantibodies directed against HPA-4a in the setting of combination checkpoint inhibitor therapy.

CASE REPORT

A 62-year-old woman with rectal melanoma that progressed on combination checkpoint inhibitors (ipilimumab and nivolumab) was admitted for abdominoperineal resection. She received multiple blood products during surgery, and between the sixth and eighth days post-surgery her platelet (PLT) count decreased from 126 × 10⁹ /L to a nadir of 1 × 10⁹ /L. She received intravenous immunoglobulin (IVIG), steroids, and romiplostim with eventual recovery of her PLT count to 50 × 10⁹ /L 20 days after surgery. She tested positive for anti-HPA-4a and was shown not to express HPA-4a, confirming a diagnosis of PTP.

CONCLUSION

Alloantibodies strongly reactive to HPA-4a were detected in this patient who received multiple blood products during abdominoperineal resection surgery. Her thrombocytopenia improved with prompt administration of IVIG, steroids, and romiplostim. PTP must always be considered in patients with acute severe thrombocytopenia after receipt of blood products, and treatment should not be delayed while awaiting laboratory confirmation. To our knowledge, this is the second reported case of PTP with antibodies against HPA-4a.

New drugs and new toxicities: pembrolizumab-induced myocarditis

Pembrolizumab is an immune checkpoint inhibitor that significantly improves clinical outcomes in numerous solid organ malignancies. Despite successful therapeutic responses, this new drug comes with a constellation of adverse reactions. Herein, we chronicle the case of a patient with metastatic non-small-cell lung cancer treated with pembrolizumab. After two cycles, he developed new-onset dyspnoea on exertion. Electrocardiogram showed idioventricular rhythm with diffuse ST-segment elevations. Echocardiography revealed severe biventricular cardiac dysfunction. Based on diagnostic workup and exclusion of probable aetiologies, the patient was diagnosed with pembrolizumab-induced myocarditis. The treatment was initiated with corticosteroids and guideline-conform heart failure therapy. He demonstrated a marked clinical response with resolution of congestive heart failure symptoms. This article summarises the clinical evidence regarding the epidemiology, pathophysiology, clinical features, diagnostic modalities and management of patients with pembrolizumab-associated myocarditis. In addition, it highlights that programmed death receptor-1 inhibition can cause a spectrum of autoimmune adverse events requiring clinical monitoring and periodic screenings.