Phase I trial of low dose decitabine targeting DNA hypermethylation in patients with chronic lymphocytic leukaemia and non‐Hodgkin lymphoma: dose‐limiting myelosuppression without evidence of DNA hypomethylation

Targeting aberrant DNA hypermethylation in chronic lymphocytic leukaemia (CLL) and non‐Hodgkin lymphoma (NHL) with decitabine may reverse epigenetic silencing in B‐cell malignancies. Twenty patients were enrolled in two phase I trials to determine the minimum effective pharmacological dose of decitabine in patients with relapsed/refractory CLL (n = 16) and NHL (n = 4). Patients received 1–3 cycles of decitabine. Dose‐limiting toxicity (DLT) was observed in 2 of 4 CLL and 2 of 2 NHL patients receiving decitabine at 15 mg/m² per d days 1–10, consisting of grade 3–4 thrombocytopenia and hyperbilirubinaemia. Six patients with CLL received decitabine at 10 mg/m² per d days 1–10 without DLT; however, re‐expression of methylated genes or changes in global DNA methylation were not observed. Therefore, a 5‐day decitabine schedule was examined. With 15 mg/m² per d decitabine days 1–5, DLT occurred in 2 of 6 CLL and 2 of 2 NHL patients, consisting of grade 3–4 neutropenia, thrombocytopenia, and febrile neutropenia. Eight patients had stable disease. In 17 patients, there were no significant changes in genome‐wide methylation or in target gene re‐expression. In conclusion, dose‐limiting myelosuppression and infectious complications prevented dose escalation of decitabine to levels associated with changes in global methylation or gene re‐expression in CLL and NHL.