PR104, that could be activated also by the enzyme aldo-keto reductase 1C3 (AKR1C3) showed remarkable activity in in vivo B-ALL mouse models, suggesting that sensitivity is correlated with AKR1C3, whose expression could be used as a biomarker to select patients for this treatment in future clinical trials (108). The gene discussed is AKR1C3; the disease is precursor B-cell acute lymphoblastic leukemia.