T-replete cord transplants give superior outcomes in high risk and relapsed/refractory paediatric myeloid malignancy

Stem cell transplant (SCT) outcomes in high-risk (HR) and relapsed/refractory (R/R) paediatric acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) have been poor historically. Cord blood allows T-cell replete transplant (TRCB), enabling enhanced graft-versus-leukaemia. We collected data from 367 consecutive patients undergoing TRCB (112 patients) or other cell source (255 patients) SCT for paediatric AML/MDS in the UK and Ireland between January 2014 and December 2021. Data was collected about patient's demographics, disease and its treatment including previous transplant, measurable residual disease (MRD) status at transplant, HLA-match, relapse, death, graft versus host disease (GvHD) and transplant-related mortality (TRM). Univariable and multivariable analyses were undertaken. There was a higher incidence of poor prognosis features in the TRCB cohort: 51.4% patients were MRD positive at transplant, 46.4% had refractory disease and 21.4% had relapsed after a previous SCT, compared with 26.1%, 8.6% and 5.1% respectively in the comparator group (all p <0.001). Within the TRCB cohort, Event Free Survival (EFS) was 64.1%, 50% in MRD positive patients and 79% in MRD negative (p= 0.009). To allow for the imbalance in baseline characteristics, a multivariable analysis was performed: the TRCB cohort had significantly improved EFS (0.57[0.35-0.91], p=0.019), time to relapse (0.46[0.26-0.81), p=0.008), and reduced chronic GVHD (HR 0.28 [95% CI 0.11-0.70]; p=0.007), with some evidence of improved Overall Survival (OS) (0.65[0.39-1.07], p = 0.088). The effect appeared similar regardless of MRD status, (interaction p-value= 0.29). CB transplant without serotherapy may be the optimal transplant option for children with myeloid malignancy

Hypomorphic RAG deficiency: impact of disease burden on survival and thymic recovery argues for early diagnosis and HSCT

Patients with hypomorphic mutations in RAG1 and RAG2 genes present as either Omenn syndrome or atypical combined immunodeficiency (CID) with a wide phenotypic range. Hematopoietic stem cell transplantation (HSCT) is potentially curative, but data are scarce. We report on a worldwide cohort of 60 patients with hypomorphic RAG variants who underwent HSCT, 78% of whom experienced infections (29% active at HSCT), 72% autoimmunity and 18% granulomas pre-transplant. These complications were frequently associated with organ damage. Eight individuals (13%) were diagnosed by newborn screening or family history. HSCT was performed at a median of 3.4 years (range 0.3 - 42.9 years) from matched unrelated donors, matched sibling or matched family donors or mismatched donors (MMFD) in 48%, 22% and 30% of the patients, respectively. Grafts were T-cell depleted in 15 cases (25%). Overall survival at 1 and 4 years was 77.5 and 67.5% (median follow-up 39 months). Infection was the main cause of death. In univariable analysis, active infection, organ damage pre-HSCT, T-cell depletion of the graft and transplant from a MMFD were predictive of worse outcome, while organ damage and T-cell depletion remained significant in multivariable analysis (HR=6.01, HR=8.46, respectively). All patients diagnosed by newborn screening or family history survived. Cumulative incidences (CI) of acute and chronic GvHD were 35% and 22% respectively. CI of new-onset autoimmunity was 15%. Immune reconstitution, particularly recovery of naïve CD4+ T-cells was faster and more robust in patients transplanted before 3.5 years and without organ damage. These findings support the indication for early transplantation