Measurable Residual Disease-Dependent Unfavorable Outcomes in Pediatric PAX5-Rearranged B-Acute Lymphoblastic Leukemia.
In pediatric PAX5-rearranged B-ALL, the study reports unfavorable event-free survival specifically among patients with positive end-of-induction MRD, alongside high FLT3 expression and preclinical sensitivity of patient-derived xenografts to FLT3 inhibitors, including gilteritinib with dexamethasone.
Open original publication →What the AI sees
In pediatric PAX5-rearranged B-ALL, the study reports unfavorable event-free survival specifically among patients with positive end-of-induction MRD, alongside high FLT3 expression and preclinical sensitivity of patient-derived xenografts to FLT3 inhibitors, including gilteritinib with dexamethasone.
Research significance
The supplied evidence shows FLT3 overexpression and FLT3-inhibitor sensitivity in PAX5-rearranged PDX models; it therefore supports—but does not clinically validate—the hypothesis that adding an FLT3 inhibitor such as gilteritinib could benefit MRD-positive pediatric PAX5-rearranged B-ALL.
Source abstract
PAX5-altered acute lymphoblastic leukemia (PAX5-alt ALL) is a recently recognized molecular subtype of B-ALL characterized by a distinct transcriptional signature and frequent PAX5 fusions (PAX5-r). While PAX5-alt ALL has been associated with intermediate outcomes, clinical data specifically investigating pediatric PAX5-r ALL remain limited. We collected and analyzed 159 pediatric cases of PAX5-r ALL treated between 2001-2024 within AIEOP-BFM ALL studies across Italy, Germany and Austria, revealing high-risk clinical features. Comparative analyses of patients consecutively enrolled in the AIEOP-BFM ALL 2017 study (PAX5-r, n=96 vs. non-PAX5-r, n=1948) confirmed higher rates of hyperleukocytosis at diagnosis (22.9% vs. 8%, p<0.001) and enrichment of IKZF1plus profile (14.7% vs. 7.8%, p=0.0015) in PAX5-r patients. No relevant differences in terms of minimal/measurable residual disease (MRD)-based treatment response and risk-group stratification were observed. PAX5-r patients had a 4-year EFS and OS of 72.6±5.7% and 95.4±2.3%, respectively. Four-year EFS were 100%, 63.4±9.7% and 63.3±10% for standard-risk, medium-risk (MR) and high-risk (HR) groups, respectively, indicating that the poor prognostic impact of PAX5-r applies only when end-of-induction MRD is positive (MR/HR). Whole transcriptome sequencing revealed high FLT3 median expression in PAX5-r ALL and high-throughput drug screening of patient-derived xenografts (PDXs) showed marked sensitivity to several FLT3 inhibitors. Gilteritinib showed potent ex vivo cytotoxicity and synergism with dexamethasone in PAX5-r PDX models. Collectively, this study investigated clinical and biological features of pediatric PAX5-r ALL highlighting its MRD-dependent unfavorable prognosis and identifying FLT3 overexpression as a novel, potential therapeutic target.