Case Report: Successful treatment of steroid-refractory severe immunotherapy-induced pneumonitis with equine antithymocyte globulin

TL;DR

A patient with severe immunotherapy-induced lung inflammation was successfully treated with equine antithymocyte globulin after other treatments failed.

Contribution

This is the first reported case of successful treatment of steroid-refractory immunotherapy-induced pneumonitis using equine antithymocyte globulin.

Findings

Equine antithymocyte globulin (eATG) led to clinical and radiological improvement in a patient with severe steroid-refractory pneumonitis.

Monitoring CD2+/CD3+ T lymphocyte counts during eATG treatment may help manage refractory immunotherapy-induced pneumonitis.

The patient remained stable for 12 months after treatment with no recurrence of lung issues or melanoma.

Abstract

Immune checkpoint inhibitors (ICI) have revolutionized melanoma treatment but are associated with autoimmune toxicities. Immunotherapy-induced pneumonitis (IIP) is a potentially fatal immune-related adverse event. Current management of IIP involves corticosteroids, mycophenolate mofetil (MMF), intravenous immunoglobulin, or infliximab for severe cases. Limited data exist for corticosteroid-refractory pneumonitis. This case report is the first to describe successful treatment of refractory grade 4 IIP with equine antithymocyte globulin (eATG) after failure of corticosteroids and MMF. A 50-year-old woman with recurrent unresectable melanoma in the right ankle developed grade 4 IIP after receiving two cycles of ipilimumab and nivolumab. Despite intravenous high-dose corticosteroid and MMF, her clinical condition continued to rapidly deteriorate. eATG was administered due to its rapid onset of T lymphocyte depletion and its use in immunotherapy-induced myocarditis. An 8-day course was delivered with dose adjustment to achieve therapeutic CD2+/CD3+ lymphocyte depletion. Clinical and radiological improvement was demonstrated, with successful weaning of oxygen and corticosteroids. At 12 months, the patient remained well from a respiratory standpoint, with no recurrence of melanoma. This case highlights the potential for eATG, with therapeutic CD2+/CD3+ T lymphocyte count monitoring, to address an unmet therapeutic need in patients with refractory ICI-induced IIP.

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