Carfilzomib‐induced hemolysis is noticeably common but rarely shows features of thrombotic microangiopathy: a retrospective study

OBJECTIVE: Hemolysis is a sporadically reported but potentially serious side effect of the proteasome inhibitor carfilzomib. We aimed to investigate the frequency of hemolysis in an unselected cohort. METHODS: We performed a retrospective, single-center study of the incidence of hemolysis in patients treated with carfilzomib, based mainly on consecutive haptoglobin levels. The patients were diagnosed with myeloma (n = 20), AL amyloidosis (n = 3), and light-chain deposition disease (n = 1). Carfilzomib treatment was applied after a median of 3 (range: 1-7) therapy lines. RESULTS: Haptoglobin levels were normal/increased before, generally suppressed during, and normalized after treatment with carfilzomib. Very low haptoglobin (<0.1 g/L) implying the presence of hemolysis was observed in 16 of 24 (67%) patients during carfilzomib therapy. Hemolysis was mild in 11 of 16 (69%) affected patients, whereas 5 of 16 (31%) required transfusion. Severe hemolysis was explained by thrombotic microangiopathy (TMA) in one patient who died of the complication. Mechanisms were unclear in the remaining 15 patients. CONCLUSIONS: Hemolysis was surprisingly common but mostly mild during carfilzomib treatment. However, the possibility of TMA should be kept in mind in this setting. Hypothetically, non-TMA hemolysis could be attributed to the accumulation of globin chains due to the suppression of eukaryotic translation initiation inhibition by carfilzomib.