Inflammatory myopathy associated with PD-1 inhibitors

Area of Science:

• Neurology
• Immunology
• Oncology

Background:

• Immune checkpoint inhibitors, such as PD-1 inhibitors, can cause immune-related adverse events.
• Inflammatory myopathies are a group of debilitating muscle diseases.
• PD-1 inhibitor myopathy is an emerging condition requiring detailed characterization.

Purpose of the Study:

• To define the clinical, histological, and immunological features of inflammatory myopathy associated with PD-1 inhibitors (PD-1 myopathy).

Main Methods:

• A cohort of 19 Japanese patients with PD-1 myopathy was analyzed.
• Clinical data, including symptoms, disease severity, and response to treatment, were collected.
• Histopathological examination of muscle biopsies and immunological markers were assessed.
• Comparison with control groups of other inflammatory myopathies and healthy subjects was performed.

Main Results:

• PD-1 myopathy presented with diverse symptoms including ptosis, diplopia, facial weakness, bulbar symptoms, limb and neck weakness, myalgia, and cardiac/respiratory involvement.
• Ocular, facial, cardiac, respiratory symptoms, and myalgia were more frequent compared to controls.
• Elevated serum creatine kinase levels were observed, with negative autoantibodies for common inflammatory myopathies but positive anti-striational antibodies in 68% of patients.
• Muscle pathology showed necrotic myofibers with inflammation and MHC class I expression; HLA-C*12:02 alleles were more frequent.

Conclusions:

• PD-1 myopathy represents a unique subset of inflammatory myopathy.
• Distinct clinical and pathological features differentiate it from other myopathies.
• Early recognition and treatment with corticosteroids are crucial for managing PD-1 myopathy.