Nelarabine has shown to be effective in treating relapsed/refractory T-cell acute lymphocytic leukemia (T-ALL) in children and adults; however, there are known concerns about its upfront use for T-ALL. Speaking from the 2017 National Cancer Research Institute (NCRI) Conference in Liverpool, UK, Prof. David Marks, MBBS, PhD, FRACP, FRCPath, of University Hospitals Bristol NHS Foundation Trust, Bristol, UK, explains the importance of investigating the outcome of nelarabine treatment in T-ALL patients and the issues surrounding funding of the drug, as well as the lack of patients for clinical trials.