Nelarabine: new drug. T-lymphoblastic leukaemia/lymphoma: more evaluation needed.

1) Acute T-lymphoblastic leukaemia and T-lymphoblastic lymphoma are closely related malignant haemopathies. There is a better prognosis for children with these disorders than for adults. There is no consensus treatment in case of relapses. However, only haematopoietic stem cell transplantation following chemotherapy offers a chance of long-term survival; 2) Nelarabine is a purine analogue closely related to clofarabine, fludarabine and cytarabine. It is marketed for the treatment of children and adults with one or the other of these two malignant haemopathies, after failure of at least two lines of chemotherapy; 3) Clinical evaluation of nelarabine in this setting includes two non-comparative trials in accordance with the conditions of the marketing terms, one in 48 children and the other in 28 adults. A complete haematological response was observed in about 20% to 25% of patients overall. But this type of non-comparative trial cannot demonstrate whether a specific drug increases survival time compared with existing alternatives; 4) In addition to haematological and gastrointestinal disorders, the main adverse effects of nelarabine were neurological (headache, drowsiness, peripheral neuropathies). Some adverse effects were serious, and they did not all resolve after treatment cessation. It is not known to what extent they affect quality of survival; 5) In practice, there are too many outstanding questions to determine whether nelarabine represents a therapeutic advance compared with clofarabine, or even whether it should be used outside the clinical trial setting.