Acute Eosinophilic Pneumonia Induced by Immune Checkpoint Inhibitor and Anti-TIGIT Therapy

BACKGROUND Immune checkpoint inhibitors (ICIs) have been linked to various immune-related adverse events, including pneumonitis, necessitating early recognition and potential treatment discontinuation. Acute eosinophilic pneumonia (AEP) induced by ICIs, particularly with no reported cases involving anti-TIGIT therapy, is rare. This report describes a case of AEP following treatment with pembrolizumab and anti-TIGIT therapy. CASE REPORT A 46-year-old woman with lung adenoid cystic carcinoma and chronic hypoxemic respiratory failure on long-term oxygen therapy presented with fever, cough, and shortness of breath. She underwent left pneumonectomy and radiation therapy at diagnosis 9 years earlier. She was participating in a clinical trial using pembrolizumab and anti-TIGIT EOS-448, due to cancer progression. After starting therapy, she developed stable peripheral eosinophilia and a skin rash, suggestive of a drug reaction. On admission, she was in acute-on-chronic hypoxemic respiratory failure, febrile, with an elevated eosinophil count and new multifocal infiltrates in the right lung. Despite broad antibiotics coverage for pneumonia, she developed worsening respiratory symptoms and eosinophilia. She was then empirically started on intravenous methylprednisolone for acute eosinophilic pneumonia without confirmatory bronchoscopy as she was at high risk with her previous pneumonectomy. She subsequently had rapid improvement in her symptoms. CONCLUSIONS AEP should be considered in patients treated with ICIs who develop immune-related adverse effects. Although bronchoscopy findings are part of AEP's diagnostic criteria, this case underscores the importance of clinical judgment in the prompt initiation of steroids, even without confirmatory bronchoscopy, in rapidly progressing cases. The role of anti-TIGIT therapy in this context remains uncertain.