Antiphospholipid syndrome (APS) is frequently associated with thrombocytopenia, in most cases mild and in the absence of major bleedings. In some patients with a confirmed APS diagnosis, secondary immune thrombocytopenia (ITP) may lead to severe thrombocytopenia with consequent major bleeding. At the same time, the presence of antiphospholipid antibodies (aPL) in patients with a diagnosis of primary ITP has been reported in several studies, although with some specific characteristics especially related to the variety of antigenic targets. Even though it does not enter the APS defining criteria, thrombocytopenia should be regarded as a warning sign of a “high risk” APS and thus thoroughly evaluated. The presence of aPL in patients with ITP should be assessed as well to stratify the risk of paradoxical thrombosis. In detail, besides the high hemorrhagic risk in secondary thrombocytopenia, patients with a co-diagnosis of APS or only antibodies are also at risk of arterial and venous thrombosis. In this narrative review, we discuss the correlation between APS and ITP, the mechanisms behind the above-reported entities, in order to support clinicians to define the most appropriate treatment strategy in these patients, especially when anticoagulant or antiplatelet agents may be needed.

The coronavirus disease 2019 (COVID‐19) pandemic created major challenges for allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Scientific societies and authorities recommended cryopreserving grafts before starting conditioning regimens, despite limited data on the clinical impact. The Italian Group for Bone Marrow Transplantation (GITMO) conducted a registry‐based study involving 3492 patients who underwent allo‐HSCT between March 2018 and September 2021. The cryopreserved cohort (n = 976) included patients who received cryopreserved grafts during the pandemic and was compared to the historical cohort (n = 2516). Graft cryopreservation was associated with a lower day 30 incidence of neutrophil and platelet engraftment (adjusted sHR = 0.8 and 0.7, p = 0.031 and p < 0.001, respectively) and delayed hematopoietic recovery. However, primary graft failure rates at day +30 were similar in the cryo and historical cohort (4% vs. 5%, respectively; p = 0.337), also after adjustment (RR = 1.19, p = 0.518). Day 100 incidence of grade II‐IV acute GVHD was comparable between the two groups (adjusted sHR = 1.2, p = 0.194). Regarding chronic GVHD incidence, we found that it was higher in patients aged < 18 years in the cryo group (adjusted sHR = 3.9, p = 0.002), but lower in those aged 18–55 years (adjusted sHR = 0.7, p = 0.008). Cumulative incidence of relapse did not differ between historical and cryo cohort (adjusted sHR 1.0. p = 0.943), as well as non‐relapse mortality (adjusted sHR 1.1, p = 0.196) and relapse‐free survival (adjusted sHR = 1.1, p = 0.197). However, a shorter overall survival was observed in the cryopreserved group (adjusted HR = 1.2, p = 0.038). Transplant centers should carefully balance the benefits and drawbacks of cryopreservation in allo‐HSCT.

The short-term and long-term effects of genotoxic pre-transplant conditioning remain barriers to the broader application of haematopoietic stem/progenitor cell (HSPC) transplantation and gene therapies^1,2,3,4. Although monoclonal antibodies targeting KIT have been proposed as alternatives to chemotherapy or radiotherapy^5,6,7, their pharmacokinetics hinder clinical applications owing to the risk of depleting transplanted HSPCs. Here, to address this issue, we identified amino acid changes in the extracellular domain of KIT that disrupt the binding of two therapeutic monoclonal antibodies^8,9, which impair stem cell factor (SCF)-mediated signalling without affecting KIT expression or functionality. We exploited adenine base editing¹⁰ or prime editing¹¹ to efficiently introduce these mutations in HSPCs and combined them with the disruption of the BCL11A erythroid enhancer to promote expression of fetal haemoglobin (HbF)^12,13, a therapeutic approach for several haemoglobinopathies. This strategy enables in vivo co-selection of gene-engineered cells to reach the threshold required to provide therapeutic benefit in patients affected by sickle cell disease and β-thalassaemia. We show progressive enrichment of KIT plus BCL11A multiplex-edited haematopoiesis under selective pressure with KIT monoclonal antibody, in vitro and in vivo. We report that extended treatment with anti-KIT regimens leads to superior in vivo enrichment while avoiding clonal selection, as assessed by a lentiviral barcoded library. Finally, by overcoming the limitations of monoclonal antibody pharmacokinetics, epitope editing enables novel haematopoietic replacement regimens that are not limited by on-target graft elimination, allowing prolonged immune-based conditioning that maximizes haematopoietic niche clearance without chemo-radiotherapy or monoclonal antibody wash-out.