Immune checkpoint inhibitors (ICPis) are a novel class of immunotherapeutic agents that have revolutionized the treatment of cancer; however, these drugs can also cause a unique spectrum of autoimmune toxicity. Autoimmune hemolytic anemia (AIHA) is a rare but often severe complication of ICPis. We identified 14 patients from 9 institutions across the US who developed ICPi-AIHA. The median interval from ICPi initiation to development of AIHA was 55 days (interquartile range [IQR], 22-110 days). Direct antiglobulin test (DAT) results were available for 13 of 14 patients: eight patients (62%) had a positive DAT and five (38%) had a negative DAT. The median pre-treatment and nadir hemoglobin concentrations were 11.8 g/dL (IQR, 10.2-12.9 g/dL) and 6.3 g/dL (IQR, 6.1-8.0 g/dL), respectively. Four patients (29%) had a pre-existing lymphoproliferative disorder, and two (14%) had a positive DAT prior to initiation of ICPi therapy. All patients were treated with glucocorticoids, with 3 requiring additional immunosuppressive therapy. Complete and partial recoveries of hemoglobin were achieved in 12 (86%) and 2 (14%) patients, respectively. Seven patients (50%) were re-challenged with ICPis, and one (14%) developed recurrent AIHA. Clinical and laboratory features of ICPi-AIHA were similar in DAT positive and negative patients. ICPi-AIHA shares many clinical features with primary AIHA; however, a unique aspect of ICPi-AIHA is a high incidence of DAT negativity. Glucocorticoids are an effective first-line treatment in the majority of patients with ICPi-AIHA, and most patients who are re-challenged with an ICPi do not appear to develop recurrence of AIHA. This article is protected by copyright. All rights reserved.
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