Immune Checkpoint Inhibitor Associated Autoimmune Encephalitis, Rare and Novel Topic of Neuroimmunology: A Case Report and Review of the Literature

Antibody-positive paraneoplastic neurological syndromes associated with immune checkpoint inhibitors: a systematic review

BACKGROUND AND OBJECTIVES

This study aimed to describe the clinical and prognostic characteristics of antibody-positive paraneoplastic neurological syndrome (PNS) associated with immune checkpoint inhibitors (ICIs).

METHODS

We conducted a systematic review of relevant publications in PubMed and Embase from inception to December 2023. Patients with positive anti-neuronal antibodies who had a definite, probable, or possible diagnosis of PNS based on the 2021 PNS-Care Score criteria were included.

RESULTS

A total of 76 records with 108 antibody-positive ICI-PNS patients were included in this systematic review. According to the updated 2021 criteria, 60.2% of patients were classified as definite PNS, 29.6% as probable PNS, and 10.2% as possible PNS. The median age was 66 years (range: 26-82), and 56.5% of patients were male. The most frequently associated tumors included lung cancer, melanoma, and Merkel cell carcinoma, and 72.2% of patients developed neurological symptoms within 6 months after ICIs treatment. The most common clinical phenotypes were limbic encephalitis (35.2%), rapidly progressive cerebellar syndrome (19.4%), and Lambert-Eaton myasthenic syndrome (13.0%), while the most common autoantibodies were anti-Hu (34.3%), anti-Ma2 (16.7%), and anti-P/Q VGCC (14.8%) antibodies. CSF inflammation was observed in 63.0% patients, predominantly lymphocytic. Corticosteroids were the mainstay of immunotherapy (90.9%), followed by intravenous immunoglobulin (IVIG) and plasma exchange. Outcome information was reported for 103 patients. The median follow-up was 4 months (IQR: 2, 10), and 56.3% of patients showed improvement, while 37.0% of patients died at the last follow-up. Patients with anti-Hu or  anti-Ma2 antibodies had a higher proportion of deterioration and mortality (P < 0.05).

CONCLUSION

Limbic encephalitis and anti-Hu antibody are relatively common in antibody-positive ICI-PNS, and most patients present with CSF inflammation. Discontinuation of ICIs and corticosteroids are the main treatments. High-risk antibodies may be a risk factor for an unfavorable prognosis, particularly anti-Hu and anti-Ma2 antibodies.

Central nervous system complications of immune checkpoint inhibitors: A comprehensive review

The ever-increasing use of immune checkpoint inhibitors (ICIs) has significantly improved cancer management, but at the cost of frequent immunologic side effects. Among them, neurologic immune-related adverse events (nirAEs) are less common but pose a challenge to clinicians due to their severity, heterogeneous nature and nonspecific clinical presentation, making diagnosis complex. The prognosis of these nirAEs, especially those related to the central nervous system (CNS), correlates with their rapid recognition and therapeutic management. Indeed, the therapeutic options are sometimes unfamiliar and may be further complicated by the lack of recommendations in the event of failure of a well-managed first-line treatment. Finally, the attribution of ICIs to certain CNS disorders is controversial and may lead to an incorrect decision to discontinue or contraindicate treatment, resulting in an irremediable loss of opportunity for the patient. Therefore, the aim of this review is to present known/suspected CNS nirAEs induced by ICI, their diagnostic approach and management through therapeutic advices for optimal treatment and rechallenge opportunities.

Brain Freeze: Pembrolizumab-Induced Autoimmune Encephalitis in Triple-Negative Breast Cancer

This case report presents the first known instance of pembrolizumab-induced autoimmune encephalitis in a 41-year-old female patient with stage IIIc triple-negative breast cancer. The patient developed expressive aphasia three days after starting pembrolizumab in combination with chemotherapy, prompting comprehensive evaluations that ruled out infectious or metastatic causes. A diagnosis of pembrolizumab-associated autoimmune encephalitis was established following a lumbar puncture and MRI. After discontinuing the immune checkpoint inhibitors (ICI) and initiating high-dose corticosteroids (methylprednisolone), the patient's symptoms significantly improved within days. This case highlights the importance of recognizing and managing neurological immune-related adverse events (irAEs) associated with ICIs, as their incidence can be variable but potentially severe. Clinicians must maintain a high index of suspicion for neurological irAEs, especially with new neurological symptoms, as early diagnosis and intervention are crucial for optimizing patient outcomes while balancing effective cancer treatment. Ongoing research is essential to elucidate the mechanisms and management strategies for ICI-related autoimmune encephalitis.

Autoimmune encephalitis following treatment with durvalumab for small-cell lung cancer

The traditional treatment for small-cell lung cancer (SCLC) has been traditional systemic platinum-containing chemotherapy because the response rate is 50-90%. Durvalumab is an immune checkpoint inhibitor that blocks the binding of programmed cell death protein 1 and programmed cell death 1 ligand 1. Durvalumab combined with traditional chemotherapy agents has been recommended as the first-line treatment for extensive-stage SCLC, but its use may cause immune-related adverse events. Autoimmune encephalitis is a rare and potentially fatal neurological adverse event. This current case report describes a male patient in his late 50s with ES-SCLC who developed autoimmune encephalitis associated with durvalumab treatment after three cycles of combination chemotherapy. This current case furthers the understanding of autoimmune encephalitis caused by durvalumab treatment.

Toxicity profiles of immune checkpoint inhibitors in nervous system cancer: a comprehensive disproportionality analysis using FDA adverse event reporting system

BACKGROUND

Immune-related adverse events (irAEs) always occur during treatment with immune checkpoint inhibitors (ICIs). Patients with nervous system cancer (NSC) may gain clinical benefit from ICIs, but irAEs in NSC patients are rarely examined. Therefore, our study systematically summarized reports of irAEs in NSC.

METHODS

We obtained information from the FDA adverse event reporting system from the first quarter (Q1) of 2013 to the fourth quarter (Q4) of 2022. We examined use of a combination of ICIs and chemotherapy (ICI_Chemo) or chemotherapy only (ICI_Chemo) for patients with NSC. Multiple disproportionality analyses were applied to assess irAEs. Multiomics data from the gene expression omnibus (GEO) database were analyzed to explore potential molecular mechanisms associated with irAEs in NSC patients.

RESULTS

Fourteen irAEs were identified in 8,357 NSC patients after removing duplicates; the top five events were seizure, confused state, encephalopathy, muscular weakness and gait disturbance. Older patients were more likely to develop irAEs than were younger patients. From the start of ICIs_Chemo to irAE occurrence, there was a significant difference in the time to onset of irAEs between age groups. irAEs may occur via mechanisms involving the inflammatory response, secretion of inflammatory mediators, and aberrant activation of pathologic pathways.

CONCLUSIONS

This study helps to characterize irAEs in NSC patients treated with ICIs. We combined GEO database analysis to explore the potential molecular mechanisms of irAEs. The results of this study provide a basis for improving the toxic effects of ICIs in NSC patients.

Severe Cytokine Release Syndrome and Immune Effector Cell-associated Neurotoxicity Syndrome in a Man Receiving Immune Checkpoint Inhibitors for Lung Cancer

A 55-year-old man with stage IV lung adenocarcinoma was treated with cisplatin, pemetrexed, nivolumab, and ipilimumab. Approximately 100 days after treatment initiation, he became disoriented and presented to the emergency department with a high fever. Blood tests revealed liver and kidney dysfunctions. Subsequently, the patient developed generalized convulsions that required intensive care. He was clinically diagnosed with cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Organ damage was gradually controlled with immunosuppressive drugs, including steroids, and the patient was discharged. Successful treatment is rare in patients with CRS, including ICANS, during immune checkpoint inhibitor treatment for solid tumors.

Autoimmune Encephalitis following Checkpoint Inhibitor Therapy in a Patient with Metastatic Melanoma in Complete Remission

The use of immune checkpoint inhibitors (ICIs) in cancer is increasing. Their side effects are mainly due to the triggering of autoimmunity, which are mild or moderate and include skin rash, colitis, hepatitis, endocrine disorders, myositis, interstitial lung disorder, etc., in most cases during the course of therapy. Autoimmune encephalitis (AE) is rare in cancer patients treated with ICIs. Fifty patients with ICI-related encephalitis were identified in a recent review. Herein, we report a case of pembrolizumab associated with AE with a favorable short-term prognosis. A 68-year-old man with malignant metastatic melanoma achieved complete remission after pembrolizumab treatment. However, 10 months after pembrolizumab cessation due to grade 3 diarrhea, he developed confusion, an altered mental status, progressive memory loss, and gait disturbance. He was admitted to the neurologic department, and a comprehensive neurological workup, brain magnetic resonance imaging, cerebral fluid analysis, EEG, and blood test allowed the diagnosis of autoimmune encephalitis. The patient was treated with plasmapheresis, a high dose of intravenous steroids, and intravenous immunoglobulins. The patient improved, and he is now well with a performance status of 1. This case is interesting since the AE developed approximately 10 months after the cessation of immunotherapy, the underlying cancer was in complete remission, and the AE showed a good response after the treatment was performed.

Neurological adverse events of immune checkpoint inhibitors and the development of paraneoplastic neurological syndromes

Immune checkpoint inhibitors, a class of oncological treatments that enhance antitumour immunity, can trigger neurological adverse events closely resembling paraneoplastic neurological syndromes. Unlike other neurological adverse events caused by these drugs, post-immune checkpoint inhibitor paraneoplastic neurological syndromes predominantly affect the CNS and are associated with neural antibodies and cancer types commonly found also in spontaneous paraneoplastic neurological syndromes. Furthermore, post-immune checkpoint inhibitor paraneoplastic neurological syndromes have poorer neurological outcomes than other neurological adverse events of immune checkpoint inhibitors. Early diagnosis and initiation of immunosuppressive therapy are likely to be crucial in preventing the accumulation of neurological disability. Importantly, the neural antibodies found in patients with post-immune checkpoint inhibitor paraneoplastic neurological syndromes are sometimes detected before treatment, indicating that these antibodies might help to predict the development of neurological adverse events. Experimental and clinical evidence suggests that post-immune checkpoint inhibitor paraneoplastic neurological syndromes probably share immunological features with spontaneous paraneoplastic syndromes. Hence, the study of post-immune checkpoint inhibitor paraneoplastic neurological syndromes can help in deciphering the immunopathogenesis of paraneoplastic neurological syndromes and in identifying novel therapeutic targets.

Protective effect of resveratrol against pembrolizumab-induced hepatotoxicity and neurotoxicity in male rats

The present study investigates the effects of resveratrol (RSV) on brain and liver tissues in rats with pembrolizumab (PEMB)-induced toxicity. Obtained for the study were 28 male Sprague-Dawley rats (3-4 months old) which were divided into four groups: Group 1: Control. Group 2: Administered PEMB at 5 mg/kg/day i.p. for a week. Group 3: Administered RSV orally at the dose of 20 mg/kg/day for 30 days by gavage. Group 4: Administered PEMB and RSV at 20 and 5 mg/kg/day RSV, respectively, for 30 days. The results of this study revealed that PEMB leads to a significant increase in thiobarbituric acid reactive substance (TBARS) levels and a significant decrease in glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD) activities, and glutathione (GSH) levels in the liver and brain tissues. The decreased SOD, CAT, GPx activities, and GSH levels increased significantly following RSV treatment in Group 4. The PEMB treatment showed histopathological alterations associated with strong positive cysteinyl aspartic acid-protease-3 (caspase-3) immunoreactivity, while RSV treatment reduced both the expression of caspase-3 protein and the histopathological changes. RSV administration prevents the biochemical, immunological, and histological alterations induced by PEMB. It can be suggested that the lower caspase-3 immunoreactivity in the PEMB + RSV group than in the PEMB group led to an inhibition of RSV on apoptosis.

Pembrolizumab-induced encephalitis in a patient with renal cell carcinoma post nephrectomy: A case report

A new category of immune-related adverse effects has been identified due to increasing use of immune checkpoint inhibitor therapy to treat solid organ cancers. Pembrolizumab approved for renal cell carcinoma also has neurological immune-related adverse effects causing long-term morbidity. We here present a case of renal cell carcinoma post nephrectomy with suspected pembrolizumab (anti-PD-1)-induced encephalitis presenting as light headedness and dizziness treated with high dose of corticosteroid and intravenous immunoglobulin. Lumbar puncture was performed which showed elevated protein, nucleated cells with lymphocyte predominant, suggestive of chemical meningitis. Scans were found to be normal while electroencephalogram showed diffuse cerebral dysfunction indicating encephalopathy. The patient was under pembrolizumab treatment so encephalitis was suspected. Clinical attention is necessary when patients receiving immune checkpoint inhibitors appear with new neurological symptoms to prevent long-term morbidity or even possible mortality.

Neurological adverse events of immune checkpoint blockade: from pathophysiology to treatment

PURPOSE OF REVIEW

We review the recent advances in neurological toxicities of immune checkpoint inhibitors, with a focus on underlying pathophysiologic mechanisms and the implications on their therapeutical management.

RECENT FINDINGS

A growing number of cancer patients benefit from immune checkpoint agents and oncologists are increasingly confronted with these novel autoimmune syndromes. During the last years, further progresses have occurred in this field, notably in the identification of specific clinical patterns, such as the association of myasthenic syndrome with myositis and myocarditis, and polyradiculoneuropathies accompanied by cerebrospinal fluid lymphocytic pleocytosis. In addition, recent immune-histological studies improved the understanding of the pathophysiologic mechanisms behind immune-related neurotoxicities.

SUMMARY

Neurological toxicity is rare compared with other organs and systems, but its potential morbidity and mortality requires a prompt management. If there is a consensus for steroids as a first-line treatment, no exhaustive clinical data exist for other treatments. Recent advances in the knowledge of pathophysiological mechanisms (behind these toxicities) should be taken into account for the management of these patients. Drugs targeting T-cell mediated inflammation should be preferred in patients who are refractory to steroids, whereas therapies targeting humoral mechanisms should be considered in specific cases associated with autoantibodies such as immune-related myasthenic syndrome.