Anti-Platelet-Derived Growth Factor Receptor Alpha Chain Antibodies Predict for Response to Nilotinib in Steroid-Refractory or -Dependent Chronic Graft-Versus-Host Disease

Imatinib has clinical activity in chronic graft-versus-host disease (cGVHD), a significant complication of allogeneic hematopoietic cell transplant. Nilotinib is a tyrosine kinase inhibitor that targets the same receptors as imatinib but with different affinities. We tested the hypothesis that nilotinib is safe and has clinical activity in cGVHD. Thirty-three participants were enrolled in a phase I/II dose escalation and dose extension clinical trial of nilotinib for the treatment of steroid-refractory or- dependent cGVHD (ClinicalTrials.gov, NCT01155817). We assessed safety, clinical response, and pretreatment anti-platelet-derived growth factor receptor alpha chain (anti-PDGFRA) antibody levels. The 200-mg dose was identified as the maximum tolerated dose and used for the phase II dose extension study. At 6 months the incidence of failure-free survival (FFS), cGVHD progression, and nilotinib intolerance resulting in its discontinuation was 50%, 23%, and 23%, respectively. cGVHD responses in skin, joints, and mouth were observed at 3 and 6 months based on improvement in respective National Institutes of Health organ severity scores. Pretreatment anti-PDGFRA antibody levels ≥ .150 optical density as measured by ELISA correlated with longer FFS time (P < .0005) and trended with time until cGVHD progression (P < .06) but not drug intolerance. Nilotinib may be effective for corticosteroid-resistant or -refractory cGVHD in some patients, but its use is limited by intolerable side effects. Selection of patients with high pretreatment anti-PDGFRA antibody levels might improve the risk-to-benefit ratio of nilotinib and better justify its side effects.