Efficacy and pharmacologic data of second-generation tyrosine kinase inhibitor nilotinib in BCR-ABL-positive leukemia patients with central nervous system relapse after allogeneic stem cell transplantation

Abstract

Central nervous system (CNS) involvement is a severe complication of BCR-ABL-positive leukemia after allogenic stem cell transplantation (alloSCT) associated with fatal outcome. Although second-generation tyrosine-kinase inhibitors (TKI) such as nilotinib have shown activity in systemic BCR-ABL(+) disease, little data exists on their penetration and efficacy within the CNS. Four patients (3 male, 1 female; age 15-49) with meningeal relapse after alloSCT and subsequent treatment with nilotinib were identified. A total of 17 cerebrospinal fluid (csf) and serum samples were assessed for nilotinib concentration and patient outcome was recorded. Nilotinib concentrations showed a low median csf/plasma ratio of 0.53% (range 0.23-1.5%), yet pronounced clinical efficacy was observed with long-lasting responses (>1 year) in three patients. Comparison with historical data showed a trend towards superior efficacy of nilotinib versus imatinib. Despite poor csf penetration, nilotinib showed significant clinical activity in CNS relapse of BCR-ABL(+) leukemias. As nilotinib has a high protein-binding affinity, the low-protein concentration in csf could translate into a relatively higher amount of free and therefore active nilotinib in csf as compared to blood, possibly explaining the observed efficacy. Thus, treatment with a 2nd generation TKI warrants further investigation and should be considered in cases of CNS relapse of BCR-ABL-positive leukemia after alloSCT.

Figure 1

Comparison of nilotinib with imatinib. Kaplan-Meier plot of patients with Ph+ CNS relapse experiencing progressive disease leading to nilotinib discontinuation while on TKI treatment. Data for imatinib was extracted from the historical Pfeifer cohort (Pfeifer et al., [1]) and compared with data from the patients treated with nilotinib in this trial. By trend, patients treated with nilotinib had a longer time to progression, although this was not statistically significant (Chi-square-test 1.9, P = 0.17).