Neurological and related adverse events in immune checkpoint inhibitors: a pharmacovigilance study from the Japanese Adverse Drug Event Report database

Introduction Immune checkpoint inhibitors (ICPI), a breakthrough immunotherapy for cancer, can cause serious neurological adverse events (AEs). We aimed to investigate the characteristics of the neurological and related AEs associated with ICPI treatment, using a large pharmacovigilance database from Japan. Methods We conducted disproportionality analysis using the Japanese Adverse Drug Event Report (JADER) database containing 566,698 patient cases recorded between April 2004 and March 2019, to detect neurological and related AE signals associated with ICPI treatment by calculating reporting odds ratio (ROR). Results Among 7604 cases with ICPI usage, we identified 583 cases (7.67%) with a significantly high reporting of neurological and related AEs (lower 95% of the ROR > 1), including myasthenia gravis (MG), inflammatory myositis, non-infectious encephalitis/myelitis, non-infectious meningitis, hypophysitis/hypopituitarism, and peripheral neuropathy including Guillain-Barre syndrome (GBS). Among the ICPI subtypes, when compared to nivolumab as a reference, number of hypophysitis, hypopituitarism, and meningitis reports from the use of ipilimumab and number of encephalitis/myelitis and meningitis reports from the use of anti-programmed cell death-ligand-1 (PD-L1) agents were significantly higher. Additionally, time to AE onset of symptoms post administration was short in meningitis (median 21 days), MG (median 28 days), myositis (median 28 days), and encephalitis/ myelitis (median 32.5 days), while it was longer in peripheral neuropathy (median 42 days), hypophysitis (median 94 days), and hypopituitarism (median 112 days). Conclusions Our results showed characteristic features of neurological and related AEs associated with each ICPI subtype, reported in a large number of Japanese patients. This would help in prompt identification and treatment of neurological AEs associated with ICPI treatment.y