[An autopsy case of nivolumab-induced myasthenia gravis and myositis]

Inflammatory Cell Infiltration Into Islets Without PD-L1 Expression Is Associated With the Development of Immune Checkpoint Inhibitor-Related Type 1 Diabetes in Genetically Susceptible Patients

Immune checkpoint inhibitors (ICIs) could cause type 1 diabetes (T1D). However, the underlying mechanism remains unclear. We immunohistochemically analyzed pancreatic specimens from three individuals with ICI-related T1D, and their histopathological data were compared those from three patients who had received ICI therapy but did not develop T1D (non-T1D) and seven normal glucose-tolerant subjects as control subjects. All ICI-related T1D patients had susceptible HLA haplotypes. In ICI-related T1D, the β-cell area decreased and the α-cell area increased compared with non-T1D and control subjects. The number of CD3-positive cells around islets increased in ICI-related T1D and non-T1D compared with control subjects, while the number of CD68-positive cells around islets increased in ICI-related T1D compared with non-T1D and control subjects. The expression ratios of programmed death-ligand 1 (PD-L1) on islets decreased in non-T1D and almost completely disappeared in ICI-related T1D, while PD-L1 expression was observed in most cells of pancreatic islets in control subjects. This study, therefore, indicates that ICI therapy itself could reduce PD-L1 expression on islets in all subjects, which may be related to β-cell vulnerability. In addition, we showed that absence of PD-L1 expression on β-cells, genetic susceptibility, and infiltration of macrophages as well as T lymphocytes around islets might be responsible for T1D onset.

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.

Myasthenia gravis induced or exacerbated by immune checkpoint inhibitors: a rising concern

Immune checkpoint inhibitors can cause immune side effects, with myasthenia gravis (MG) being relatively rare. With this review, we present 66-year-old man with melanoma treated with pembrolizumab who developed MG. With immuno-oncology (IO) single agent usage, 42 cases reported new-onset MG and 9 cases reported exacerbation of pre-existing MG. Among the patients who had new-onset MG after administration of programmed cell death protein 1 (PD-1) inhibitors, 14 patients (38.8%) developed severe respiratory failure and required intubation and 10 patients (27.02%) died. Among the patients with exacerbation of pre-existing MG after receiving PD-1 inhibitors, 1 patient (11.1%) required intubation, and no death was reported. Combination IO therapy-induced MG was reported in seven cases, with at least two cases complicated by respiratory failure and one death. Our observations suggest a possible difference in the severity of the disease and outcome among different IO therapy options.