Ixazomib for Treatment of Refractory Chronic Graft-versus-Host Disease: A Chronic GVHD Consortium Phase II Trial

New interventions are needed in advanced chronic graft-versus-host disease (GVHD). In a phase II, single-arm, multicenter trial, we examined the efficacy of ixazomib in patients with chronic GVHD who had progressed after at least 1 previous line of systemic immunosuppressive (IS) therapy. Ixazomib was given as a 4 mg oral dose weekly on days 1, 8, and 15 of a 28-day cycle for up to 6 total cycles. The primary endpoint was 6-month treatment failure, a composite endpoint including death, relapse, and requirement for an additional line of systemic IS therapy. A total of 50 subjects were enrolled at 6 institutions. The median time from the onset of chronic GVHD to enrollment was 2.8 years (interquartile range, 1.5 to 4.3 years). The degree of chronic GVHD at enrollment was National Institutes of Health (NIH)-defined moderate (16%) or severe (84%), predominantly classic (80% versus 20% overlap), with 52% of patients having involvement of 4 or more organs. The patients were heavily pretreated, with 39 (78%) receiving 3 or more previous lines of systemic therapy for chronic GVHD. Of the 50 patients treated, 26 completed 6 months of planned therapy. The 6-month treatment failure rate was significantly lower than the historical benchmark (28% versus 44%; P = .01) previously established in second-line therapy for chronic GVHD. No patient, transplantation, or chronic GVHD variables were significantly associated with 6-month treatment failure. NIH-defined overall response rate was 40% at 6 months. Overall survival was 92% at 6 months and 90% at 12 months. Ixazomib met the primary endpoint of low treatment failure at 6 months in the setting of advanced chronic GVHD. At 6 months, the NIH-defined rate of complete/partial response was 40%, and 52% of patients remained on ixazomib therapy, suggesting that the low treatment failure rate was due in part due to prevention of progressive disease that would have required additional treatment.