Inhibition of chronic graft-vs-host disease with retention of anti-myeloma effects by the proteasome inhibitor bortezomib

New and emerging therapies for acute and chronic graft versus host disease

Graft versus host disease (GVHD) remains a major cause of morbidity and mortality following allogeneic hematopoietic stem-cell transplantation (HSCT). Despite the use of prophylactic GVHD regimens, a significant proportion of transplant recipients will develop acute or chronic GVHD following HSCT. Corticosteroids are standard first-line therapy, but are only effective in roughly half of all cases with ~50% of patients going on to develop steroid-refractory disease, which increases the risk of nonrelapse mortality. While progress has been made with improvements in survival outcomes over time, corticosteroids are associated with significant toxicities, and many currently available salvage therapies are associated with increased immunosuppression, infectious complications, and potential loss of the graft versus leukemia (GVL) effect. Thus, there is an unmet need for development of newer treatment strategies for both acute and chronic GVHD to improve long-term post-transplant outcomes and quality of life for HSCT recipients. Here, we provide a concise review of major emerging therapies currently being studied in the treatment of acute and chronic GVHD.

A phase II study of bortezomib plus prednisone for initial therapy of chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) induces significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Corticosteroids are standard initial therapy, despite limited efficacy and long-term toxicity. Based on our experience using bortezomib as effective acute GVHD prophylaxis, we hypothesized that proteasome-inhibition would complement the immunomodulatory effects of corticosteroids to improve outcomes in chronic GVHD (cGVHD). We undertook a single-arm phase II trial of bortezomib plus prednisone for initial therapy of cGVHD. Bortezomib was administered at 1.3 mg/m(2) i.v. on days 1, 8, 15, and 22 of each 35-day cycle for 3 cycles (15 weeks). Prednisone was dosed at .5 to 1 mg/kg/day, with a suggested taper after cycle 1. All 22 enrolled participants were evaluable for toxicity; 20 were evaluable for response. Bortezomib plus prednisone therapy was well tolerated, with 1 occurrence of grade 3 sensory peripheral neuropathy possibly related to bortezomib. The overall response rate at week 15 in evaluable participants was 80%, including 2 (10%) complete and 14 (70%) partial responses. The organ-specific complete response rate was 73% for skin, 53% for liver, 75% for gastrointestinal tract, and 33% for joint, muscle, or fascia involvement. The median prednisone dose decreased from 50 mg/day to 20 mg/day at week 15 (P < .001). The combination of bortezomib and prednisone for initial treatment of cGVHD is feasible and well tolerated. We observed a high response rate to combined bortezomib and prednisone therapy; however, in this single-arm study, we could not directly measure the impact of bortezomib. Proteasome inhibition may offer benefit in the treatment of cGVHD and should be further evaluated.

Proteasome inhibition and allogeneic hematopoietic stem cell transplantation: a review

The proteasome and its associated ubiquitin protein modification system have proved to be an important therapeutic target in the treatment of multiple myeloma and other cancers. In addition to direct antitumor effects, proteasome inhibition also exerts strong effects on nonneoplastic immune cells. This indicates that proteasome inhibition, through the use of agents like bortezomib, could be used therapeutically to modulate immune responses. In this review we explore the emerging data, both preclinical and clinical, highlighting the importance of proteasome targeting of immunologic responses, primarily in the context of allogeneic hematopoietic stem cell transplantation (HSCT), both for the control of transplant-related toxicities like acute and chronic graft-versus-host disease (aGVHD, cGHVHD), and for improved malignant disease control after allogeneic HSCT.