Myositis as a neuromuscular complication of immune checkpoint inhibitors

Immune Checkpoint Inhibitor-induced Myositis

Myositis induced by immune checkpoint inhibitors (ICIs) is an infrequent, potentially fatal, immune-related adverse event. It has higher incidence in patients who receive combination ICI therapy compared to monotherapy. Patients can present with clinical manifestation symptoms of myositis alone or in combination with myocarditis and/or myasthenia gravis, which significantly worsens the course and prognosis. Diagnosis can generally be made on the basis of clinical presentation, elevation of muscle enzymes, and electromyographic changes, but some patients may require a muscle biopsy. The first line of therapy is high-dose corticosteroids, followed by immunosuppression, plasmapheresis, or intravenous immunoglobulin in patients with severe disease.

Role of Biomarkers in the Management of Immune-Checkpoint Inhibitor-Related Myocarditis

PURPOSE OF REVIEW

Immune checkpoint inhibitor (ICI)-related myocarditis poses a major clinical challenge given its non-specific presentation, rapid progression, and high mortality rate. Here, we review the role of blood-based biomarkers in the clinical management of patients with ICI-related myocarditis.

RECENT FINDINGS

Myocardial injury, its unique pattern, and the co-occurrence with myositis are defining features of ICI-related myocarditis. Non-cardiac biomarkers, specifically creatinine phosphokinase, precedes the symptomatic presentation and is highly sensitive for diagnosing ICI-related myocarditis, making them useful screening biomarkers. Combined elevations in cardiac troponins and non-cardiac biomarkers improve the confidence of an ICI myocarditis diagnosis. High troponin and creatinine phosphokinase levels are strongly associated with severe outcomes. We propose biomarker-based algorithms for the monitoring and diagnosis of ICI-related myocarditis. Biomarkers, such as cardiac troponins and creatine phosphokinase, can be used in combination in the monitoring, diagnosis, and prognostication of patients with ICI-related myocarditis.

Pembrolizumab-Induced Fatal Myasthenia, Myocarditis, and Myositis in a Patient with Metastatic Melanoma: Autopsy, Histological, and Immunohistochemical Findings-A Case Report and Literature Review

Immune checkpoint inhibitors (ICIs) represent a major advance in cancer treatment. The lowered immune tolerance induced by ICIs brought to light a series of immune-related adverse events (irAEs). Pembrolizumab belongs to the ICI class and is a humanized IgG4 anti-PD-1 antibody that blocks the interaction between PD-1 and PD-L1. The ICI-related irAEs involving various organ systems and myocarditis are uncommon (incidence of 0.04% to 1.14%), but they are associated with a high reported mortality. Unlike idiopathic inflammatory myositis, ICI-related myositis has been reported to frequently co-occur with myocarditis. The triad of myasthenia, myositis, and myocarditis must not be underestimated as they can rapidly deteriorate, leading to death. Herein we report a case of a patient with metastatic melanoma who fatally developed myasthenia gravis, myocarditis, and myositis, after a single cycle of pembrolizumab. Considering evidence from the literature review, autopsy, histological, and immunohistochemical investigations on heart and skeletal muscle are presented and discussed, also from a medical-legal perspective.

Transcriptomic profiling reveals distinct subsets of immune checkpoint inhibitor induced myositis

OBJECTIVES

Inflammatory myopathy or myositis is a heterogeneous family of immune-mediated diseases including dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotising myopathy (IMNM) and inclusion body myositis (IBM). Immune checkpoint inhibitors (ICIs) can also cause myositis (ICI-myositis). This study was designed to define gene expression patterns in muscle biopsies from patients with ICI-myositis.

METHODS

Bulk RNA sequencing was performed on 200 muscle biopsies (35 ICI-myositis, 44 DM, 18 AS, 54 IMNM, 16 IBM and 33 normal muscle biopsies) and single nuclei RNA sequencing was performed on 22 muscle biopsies (seven ICI-myositis, four DM, three AS, six IMNM and two IBM).

RESULTS

Unsupervised clustering defined three distinct transcriptomic subsets of ICI-myositis: ICI-DM, ICI-MYO1 and ICI-MYO2. ICI-DM included patients with DM and anti-TIF1γ autoantibodies who, like DM patients, overexpressed type 1 interferon-inducible genes. ICI-MYO1 patients had highly inflammatory muscle biopsies and included all patients that developed coexisting myocarditis. ICI-MYO2 was composed of patients with predominant necrotising pathology and low levels of muscle inflammation. The type 2 interferon pathway was activated both in ICI-DM and ICI-MYO1. Unlike the other types of myositis, all three subsets of ICI-myositis patients overexpressed genes involved in the IL6 pathway.

CONCLUSIONS

We identified three distinct types of ICI-myositis based on transcriptomic analyses. The IL6 pathway was overexpressed in all groups, the type I interferon pathway activation was specific for ICI-DM, the type 2 IFN pathway was overexpressed in both ICI-DM and ICI-MYO1 and only ICI-MYO1 patients developed myocarditis.

Characterization of Immune Checkpoint Inhibitor-Induced Myasthenia Gravis Using the US Food and Drug Administration Adverse Event Reporting System

Myasthenia gravis (MG) is a rare but fatal adverse event of immune checkpoint inhibitors (ICIs). We assessed whether patient characteristics differed between those with ICI-related myasthenia gravis and those with idiopathic myasthenia gravis. Reports from the US Food and Drug Administration Adverse Event Reporting System were analyzed. Multivariate analyses were conducted to evaluate the associations between age, sex, and ICI treatment and the reporting rate of myasthenia gravis. Among 5 464 099 cases between 2011 and 2019, 53 447 were treated with ICIs. Myasthenia gravis was reported more often in ICI users. Multiple logistic regression analyses showed that the reporting rate of ICI-related myasthenia gravis did not differ significantly between men and women; however, it was higher in older people than in younger people (adjusted odds ratio, 2.4 [95%CI, 1.84-3.13]). We also investigated useful signs for the early detection of myositis and myocarditis, which are fatal when overlapping with ICI-related myasthenia gravis. Patients with elevated serum creatine kinase or troponin levels were more likely to have concurrent myositis and myocarditis. Unlike idiopathic myasthenia gravis, there was no sex difference in the development of ICI-related myasthenia gravis, which may be more common in older people. Considering the physiological muscle weakness that occurs in the elderly, it may be necessary to monitor ICI-related myasthenia gravis more closely in older people.

Exploring the role of immune checkpoint inhibitors in the etiology of myasthenia gravis and Lambert-Eaton myasthenic syndrome: A systematic review

Background

While immune checkpoint inhibitors (ICIs) have been revolutionary in the treatment of cancer, their administration has been associated with a variety of immune-related adverse events (irAEs), including myasthenia gravis (MG), and Lambert-Eaton myasthenic syndrome (LEMS).

Objective

To provide a comprehensive synthesis of the evidence supporting an etiological role for ICIs in MG and LEMS in patients with no prior history of autoimmune disease.

Hypothesis

ICIs may trigger MG and LEMS in patients with no prior susceptibility to autoimmune disease.

Methods

Relevant primary research on Medline was interrogated using a series of search algorithms. Search terms were constructed based on the PICOS tool endorsed by the Cochrane Collaboration, which describes population, intervention, comparison, outcomes, and study design. Papers were screened according to inclusion and exclusion criteria. Additional papers were retrieved from the reference lists of screened papers. Each paper included in the qualitative synthesis was assigned an integrated metric of evidence (IME) value, ranging from 0 to 7, based on study design, quality of data, likelihood of a causal link between the immune checkpoint inhibitor(s) and MG/LEMS, confidence of MG/LEMS diagnosis, and the number of patients treated with an ICI prior to MG/LEMS diagnosis.

Results

Ninety-four papers describing at least one patient treated with ICI(s) prior to the onset of MG and/or LEMS were documented. Overall evidence for a causal link between ICI administration and MG/LEMS was low, with a median IME value of 2.88 (range 2.05-6.61).

Conclusions

There is a paucity of evidence in support of an etiological relationship between ICIs and MG/LEMS, due largely to the lack of mechanistic studies and/or prospective clinical trials with relevant study endpoints. The current literature is dominated by case reports and retrospective cohort studies, which inherently yield only low-level evidence, supporting the need for further work in this area. A role of ICIs in the etiology of MG/LEMS remains plausible, arguing for continued vigilance for irAEs in patients treated with these drugs. We argue that there is a need for future mechanistic, high quality, large-scale studies specifically investigating the possible etiological role of ICIs in MG/LEMS.

Ophthalmic immune-related adverse events associated with immune checkpoint inhibitors

Purpose

To investigate the incidence of immune-related adverse events (irAEs) of immune checkpoint inhibitor (ICI) therapy and to report the clinical features, management, and outcomes of ophthalmic irAEs.

Methods

We retrospectively reviewed the medical records of patients who received ICI therapy from January 2016 to September 2022 at Peking Union Medical College Hospital and analyzed the incidence of systemic and ophthalmic adverse effects of this therapy.

Results

Of 962 patients, 248 (25.8%) experienced irAEs. The first-year incidences of total irAEs and ophthalmic irAEs were 23.5% and 1.1%. The most common ICI received by the patients was pembrolizumab (373; 38.8%). Nearly half of the patients (477; 49.6%) had lung cancer. Combination therapy was associated with an increased incidence of irAEs without statistical significance. Patients with lung cancer presented with an increased incidence of total irAEs (p = 0.003) and ophthalmic irAEs (p = 0.032). Eleven patients had ophthalmic manifestations, including ophthalmoplegia (6/11), conjunctivitis (3/11), reactive cutaneous capillary endothelial proliferation (RCCEP) (1/11), and orbital inflammation (1/11). Eight patients had concomitant extra-ophthalmic irAEs. Furthermore, ICIs were discontinued in nine patients, and most ophthalmic manifestations were well controlled with topical and systemic steroids. Ten patients were treated with intravenous or oral steroids. However, cancer progression occurred in five out of eleven patients after the interruption of ICIs.

Conclusion

IrAEs are correlated with ICI regimens and underlying neoplasia. In our Chinese cohort, patients have a higher risk of ophthalmoplegia than uveitis. Early recognition and multidisciplinary consultation are crucial for optimal treatment of ophthalmic irAEs.

Pathologic Predictors of Response to Treatment of Immune Checkpoint Inhibitor–Induced Kidney Injury

Background: Immune-related adverse events are a management challenge in patients receiving immune checkpoint inhibitors (ICIs). The most common renal immune-related adverse event, acute interstitial nephritis (AIN), is associated with patient morbidity and mortality. AIN, characterized by infiltration of renal tissue with immune cells, may be analogous to kidney transplant rejection. We evaluated clinical variables and pathologic findings to identify predictors of renal response and overall survival (OS) in patients with ICI-induced AIN. Design, setting, participants, and measurements: We reviewed the records and biopsy specimens of all 35 patients treated for ICI-induced AIN at our institution, between August 2007 and August 2020, who had biopsy specimens available. Two board-certified renal pathologists graded the severity of inflammation and chronicity using transplant rejection Banff criteria and performed immunohistochemistry analysis. Patients were categorized as renal responders if creatinine had any improvement or returned to baseline within 3 months of initiating treatment for AIN. Clinical and pathologic characteristics and OS were compared between responders and non-responders. Results: Patients with high levels of interstitial fibrosis were less likely to be responders than those with less fibrosis (p = 0.02). Inflammation, tubulitis, the number of eosinophils and neutrophils, and the clustering or presence of CD8+, CD4+, CD20+, or CD68+ cells were not associated with renal response. Responders had better OS than non-responders (12-month OS rate 77% compared with 27%, p = 0.025). Responders who received concurrent ICIs had the best OS, and non-responders who did not receive concurrent ICIs had the worst OS (12-month OS rate 100% for renal response and concurrent ICIs, 72% for renal response and no concurrent ICIs, and 27% for no renal response and no concurrent ICIs; p = 0.041). Conclusions: This is the first analysis of ICI induced nephritis where a detailed pathological and clinical evaluation was performed to predict renal response. Low levels of interstitial fibrosis in kidney tissue are associated with renal response to treatment for ICI-induced AIN, and the renal response and use of concurrent ICIs are associated with better OS in these patients. Our findings highlight the importance of the early diagnosis and treatment of ICI-AIN, while continuing concurrent ICI therapy.

Ibrutinib-Associated Cardiotoxicity: From the Pharmaceutical to the Clinical

Ibrutinib is the first-in-class Bruton tyrosine kinase (BTK) inhibitor that has revolutionized the treatment of B cell malignancies. Unfortunately, increased incidences of cardiotoxicity have limited its use. Despite over a decade of research, the biological mechanisms underlying ibrutinib cardiotoxicity remain unclear. In this review, we discuss the pharmacological properties of ibrutinib, the incidence and mechanisms of ibrutinib-induced cardiotoxicity, and practical management to prevent and treat this condition. We also synopsize and discuss the cardiovascular adverse effects related to other more selective BTK inhibitors, which may guide the selection of appropriate BTK inhibitors.

Differential diagnosis of necrotizing myopathy

PURPOSE OF REVIEW

Necrotizing myopathy is a broad term. It includes patients with the recently described immune-mediated necrotizing myopathies (IMNM) who have specific antibodies, such as anti-hydroxy-3-methylglutaryl-CoA reductase or anti-signal recognition particle, seronegative phenotypes that can be associated with cancer, and other types of myositis and connective tissue diseases involving necrotic muscle fibers as a characteristic pathologic feature. Necrotizing myopathies that are not immune-mediated, such as those caused by drugs, dystrophies, infections, or even hypothyroidism are also included. The purpose of this review is to address the differential diagnosis of these disorders.

RECENT FINDINGS

New IMNM have been described over the last few years, some of them related with checkpoint inhibitors, drugs that are being increasingly used in cancer treatment. Necrotizing myopathy has also been reported in association with specific phenotypes and autoantibodies (e.g. anti-Mi2 dermatomyositis, antisynthetase syndrome, and myositis associated with antimitochondrial antibodies). Rarer cases associated with graft-versus-host disease and severe acute respiratory syndrome coronavirus 2 infection are also emerging.

SUMMARY

Differentiation between patients with IMNM and those without the superimposed autoimmune phenomena helps clinicians determine the best individualized approach to use and the appropriate immunosuppressive therapy, whenever needed.

A systematic review of myasthenia gravis complicated with myocarditis

Among many of the autoimmune diseases observed in patients with myasthenia gravis (MG), myocarditis is one of the most critical. The goal of this review is to systematically describe and investigate the characteristics of MG complicated with myocarditis. We identified 183 records in PubMed (MEDLINE), Web of Science, and EMBASE from 1948 to September 10, 2020. Studies were included if they presented clinical data on MG complicated with myocarditis. Of the 35 patients from 28 studies in this review, 57.14% (20/35) were males, with a mean age of 59.11 ± 15.87. Dyspnea was the most common cardiac symptom accounting for over 60% in the study. Among the 35 patients, 13 cases of myocarditis occurred concomitantly with MG and the longest interval between MG and myocarditis was 7 years. Forty percent of patients developed myocarditis caused by immune checkpoint inhibitors (ICI). Among the patients with myocarditis, over half of the patients were diagnosed by myocardial biopsy. After active immune regulation and symptomatic treatment, only 15 of 35 patients with MG complicated with myocarditis improved, 18 patients died during hospitalization, one patient died due to tumor progression and 1patient died 5 years later. The prognosis of patients with MG complicated with myocarditis is poor, and myocardial enzymes and other indexes need to be monitored for patients taking ICI drugs. Patients with dyspnea who are still not ideally treated by mechanical ventilation should be vigilant against the occurrence of MG complicated with myocarditis.

Treatment strategies and safety of rechallenge in the setting of immune checkpoint inhibitors-related myositis: A national multicenter study

OBJECTIVES

The occurrence of immune-related myositis (irM) is increasing, yet there are no therapeutic guidelines. We sought to analyze the current therapeutic strategies of irM and evaluate the outcomes of immune checkpoint inhibitors (ICI) rechallenge.

METHODS

We conducted a nationwide retrospective study between April 2018 and March 2020 including irM without myocardial involvement. Depending on the presence of cutaneous signs or unusual histopathological features, patients were classified into two groups: typical or atypical irM. Therapeutic strategies were analyzed in both groups. The modalities and outcomes of ICI rechallenge were reviewed.

RESULTS

Among the 20 patients, 16 presented typical irM. Regardless of severity, most typical irM were treated with steroid monotherapy (n = 14/16) and all had a complete response within ≤ 3 weeks. The efficacy of oral steroids for non-severe typical irM (n = 10) was the same with low-dose (≤ 0.5 mg/kg/day) or high-dose (1 mg/kg/day). Severe typical irM were successfully treated with intravenous methylprednisolone. Atypical irM (n = 4) had a less favorable evolution, including one irM-related death, and required heavy immunosuppression. ICI were safely reintroduced in 9 patients presenting a moderate (n = 6) or a severe (n = 3) irM.

CONCLUSION

Our data highlight that steroid monotherapy is an effective treatment for typical irM, either with prednisone or with intravenous methylprednisone pulses depending on the severity. The identification of unusual features is important in determining the initial therapeutic strategy. The outcomes of rechallenged patients are in favor of a safe reintroduction of ICI following symptom resolution and CK normalization in moderate and severe forms of irM.

Expert Perspective: Immune Checkpoint Inhibitors and Rheumatologic Complications

Rheumatologists increasingly receive consults for patients treated with immune checkpoint inhibitors (ICIs) for cancer. ICIs can cause inflammatory syndromes known as immune-related adverse events (IRAEs). Several rheumatic IRAEs have been reported, including inflammatory arthritis, polymyalgia rheumatica, and myositis. For patients who present with musculoskeletal symptoms while receiving ICI therapy, it is important to have an algorithm for evaluation. The differential diagnosis includes a range of musculoskeletal syndromes, such as crystalline arthritis, mechanical issues, and osteoarthritis, in addition to IRAEs. After diagnosing a rheumatic IRAE, rheumatologists must work with the patient and the oncologist to form a treatment plan. Treatment of IRAEs is guided by severity. Evidence for management is limited to observational studies. Inflammatory arthritis and polymyalgia rheumatica are treated with nonsteroidal antiinflammatory drugs in mild cases, glucocorticoids for moderate-to-severe cases, and sometimes require other disease-modifying antirheumatic drugs. Myositis due to ICIs can be accompanied by myocarditis or myasthenia gravis. Glucocorticoids and withholding the ICI are usually required to treat myositis; some patients with severe myositis require intravenous immunoglobulin or plasmapheresis. Further research is needed to optimize treatment of IRAEs that does not compromise the antitumor effect of ICIs.

Immune Checkpoint Inhibitor-Induced Polymyositis and Myasthenia Gravis with Fatal Outcome

We here report on a 74-year-old man diagnosed with a pT3cN0 BRAF-mutated and mismatch repair-deficient adenocarcinoma in the colon ascendens and 3 liver metastases. After hemicolectomy, the patient received treatment with the PD-1 inhibitor pembrolizumab. Three weeks later (on day 22), laboratory tests showed leukocytosis and an increase in transaminases; immune checkpoint inhibitor (ICI)-induced hepatitis was suspected and prednisolone therapy was initiated. On day 29, the patient was acutely hospitalized due to dyspnea, somnolence and walking difficulties. Dysarthria, hoarseness, muscle pain and weakness had developed and the dose of prednisolone was increased. Serum levels of lactate dehydrogenase, creatine kinase and myoglobin were increased and ICI-induced myositis was suspected. Antibodies against acetylcholine receptor and titin were present, indicating myasthenia gravis. Eventually, bulbar myopathy developed, including dysarthria and dysphagia, and the patient could no longer attain saturation without oxygen. The patient was transferred to the intensive care unit, intubated and given methylprednisolone, intravenous immunoglobulins and infliximab. The patient developed carbon dioxide retention and died on day 39. Microscopical examination of the intercostal musculature, diaphragm, cervical musculature and tongue showed inflammatory infiltration and fibrosis consistent with a pronounced myositis. In the liver, microscopical examination did not show metastases from colorectal cancer but instead a hepatocellular cancer. The cause of death was determined as respiratory insufficiency due to polymyositis. In conclusion, ICIs may induce myositis combined with neurological immune-related adverse events. In patients developing muscle weakness and pain under ICI therapy, myositis should be suspected.