Treatment of mycophenolate-resistant immune-related organizing pneumonia with infliximab

Background: The development of pulmonary immune-related adverse events (irAEs) in patients undergoing PD-(L)1 targeted checkpoint inhibitors are rare, but may be life-threatening. While many published articles and guidelines are focusing on the presentation and upfront treatment of pulmonary irAEs, the strategy in patients with late-onset pneumonia that are resistant to commonly used immunosuppressive drugs remains unclear. Case presentation: Here, we report the successful treatment of a mycophenolate-resistant organizing pneumonia (OP) with infliximab in a patient with metastatic melanoma after PD-1 blockade. The patient received two years of PD-1 targeted immunotherapy when he developed multiple nodular lung lesions mimicking a metastatic progression. However, wedge resection of these lesions showed defined areas of OP, which responded well to corticosteroids. Upon tapering, new foci of OP developed which were resistant to high-dose steroids and mycophenolate treatment. The TNF alpha antagonist infliximab led to a rapid and durable regression of the inflammatory lesions. Conclusion: This case describes a not well-studied situation, in which a mycophenolate-resistant PD-1 blocker associated pneumonitis was successfully treated with a TNF alpha neutralizing antibody. The outcome of this case suggests that infliximab might be the preferable option compared to classical immunosuppressants in the case of steroid-resistant/-dependent late onset pulmonary irAEs.