A recent Haematology digest,
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Study Type: Preclinical translational study (patient tumour scRNA-seq, in vitro rechallenge model, in vivo xenograft model). Not a clinical trial.

Key Question: Does chronic antigen stimulation drive CD8 CART19 exhaustion in rrLBCL, and can a non-alpha IL2 receptor agonist (pegenzileukin) prevent it?

Key Findings:

• scRNA-seq of post-CART19 progression tumours showed clonally expanded, proliferating CART19 cells with dysfunction signatures in a subset of patients, consistent with ongoing tumour engagement rather than CAR T-cell absence.
• In vitro, serial tumour rechallenge caused loss of tumour control, T-cell dysfunction and reduced IL2 signalling; pegenzileukin restored T-cell expansion and tumour control.
• In an in vivo model derived from a post-CART19 progression tumour, CART19 alone gave transient response then progression with CNS relapse; CART19 plus pegenzileukin achieved complete tumour eradication.

Clinical Relevance: Supports exhaustion as a targetable failure mechanism after CAR-T for rrLBCL, a major unmet need given limited options at post-CAR-T relapse in the NHS.

Limitations: Evidence is entirely preclinical, with efficacy shown in a single patient-derived model and no human safety or efficacy data.

Study Type: Preclinical experimental study (in vitro assays and murine in vivo models); no human data.

Key Question: Can adding a thrombin-cleavable hinge peptide to emicizumab create a self-limiting FVIII-mimetic antibody that retains haemostatic efficacy while reducing thrombotic risk, particularly with aPCC co-exposure?

Key Findings:

• AR-emicizumab matched parental emicizumab for EC50 of FVIII-mimetic activity and correction of blood loss in haemophilia A mice.
• Under supra-physiological thrombin exposure, AR-emicizumab was proteolytically inactivated (parental drug unaffected), significantly attenuating the excess thrombin peak seen with emicizumab plus aPCC in thrombin generation assays.
• In vivo, AR-emicizumab prevented platelet-consumptive coagulopathy and reduced microvascular pulmonary thrombosis versus the parental molecule, without altering systemic antibody levels. Specific effect sizes were not reported in the abstract.

Clinical Relevance: Thrombotic microangiopathy and thrombosis with emicizumab plus aPCC remain a concern for UK clinicians managing breakthrough bleeds in inhibitor patients, so this is an early proof-of-concept for a potentially safer next-generation agent.

Limitations: Findings are preclinical only; safety, immunogenicity, and efficacy of the thrombin-cleavable construct in humans are untested.

Study Type: Narrative review (with a proposed mechanistic model drawing on the authors' own and others' investigations). No systematic search methodology is stated in the abstract.

Key Question: What immunologic and plasma-dependent mechanisms drive chronic haemolysis and acute hyperhaemolysis in sickle cell disease?

Key Findings:

• Sickle red cell clearance is immune-regulated, involving altered membrane markers (phosphatidylserine, mannose, CD47, CD95/Fas), plasma opsonins (including IgG, C3b, Gas6, MFG-E8) and their macrophage receptors.
• Proposed model: chronic haemolysis is predominantly extravascular (erythrophagocytosis), whereas acute events, including post-transfusion hyperhaemolysis syndrome (HHS), shift towards intravascular haemolysis via membrane attack complex assembly, Fas-mediated erythronecroptosis and heme-mediated ferroptosis.
• Mechanisms by which transfusion may accelerate these pathways and precipitate HHS are discussed.

Clinical Relevance: The proposed complement- and cell-death-based mechanisms of HHS may inform future therapeutic targets (e.g., complement inhibition) and transfusion strategies for SCD patients in UK practice, where HHS remains difficult to manage.

Limitations: As a narrative review presenting a hypothesis-generating model, it provides no quantitative clinical data, and the proposed model has not been validated clinically.

Study Type: Pragmatic long-term follow-up of a randomised trial cohort (SPRINT); post-hoc observational extension, not a new randomised comparison.

Key Question: Does initial fixed low-dose versus moderate-dose hydroxyurea affect long-term recurrent stroke and mortality in children with sickle cell disease and prior stroke?

Key Findings:

• Over 4.9 years of follow-up, recurrent stroke and all-cause mortality did not differ significantly between low and moderate initial fixed-dose arms.
• Events clustered in the first year after assignment.
• Effect sizes, confidence intervals, event numbers and sample size are not reported in the abstract.

Clinical Relevance: Supports the view that fixed-dose hydroxyurea may be a pragmatic option, particularly in resource-limited settings, though UK practice (dose escalation to maximum tolerated dose, with transfusion for secondary stroke prevention) is unlikely to change on this evidence alone.

Limitations: The abstract lacks quantitative data, and population, setting and dosing details are unspecified (SPRINT context is inferred); non-significance may reflect insufficient power rather than true equivalence.

Study Type: Nationwide multicentre retrospective cohort study with molecular characterisation (24 Spanish centres)

Key Question: How common are donor cell-derived haematologic neoplasms (DDHN) after allo-HSCT, and what molecular mechanisms drive them?

Key Findings:

• Prevalence was 0.28% among 8,465 allo-HSCTs (2013–2022), significantly higher after related-donor than unrelated-donor transplants (0.41% vs 0.06%, p=0.0026). Median latency was 56 months; 87% of the 39 cases were MDS (51%) or AML (36%).
• Of 33 cases with molecular data, 10 carried pathogenic/likely pathogenic germline variants (DDX41 n=7, CEBPA n=2, CHEK2 n=1), all in related-donor transplants.
• Donor-derived clonal hematopoiesis was confirmed in only one case (U2AF1).

Clinical Relevance: Supports germline testing at diagnosis in patients being considered for allo-HSCT, with cascade testing of candidate related donors, which is relevant to UK donor selection and genomic testing pathways.

Limitations: Retrospective design with likely under-ascertainment of DDHN, and molecular data were unavailable for 6 of the 39 cases.

Study Type: Narrative review (no original data; abstract reports no systematic methodology).

Key Question: What is currently understood about the biology, genotype-phenotype associations and clinical implications of recurrent splicing factor mutations in myeloid malignancies, particularly MDS?

Key Findings:

• Splicing factor mutations, first described in 2011, are among the most frequent genetic lesions in MDS and related dysplastic myeloid neoplasms, implicating aberrant RNA splicing as a core pathogenetic pathway.
• Mutation-specific splicing effects and strong genotype-phenotype associations are established, and SF mutations are now incorporated into current disease classification and prognostic models.
• The mechanisms driving positive clonal selection and genotype-phenotype associations remain poorly understood; co-mutations, clonal architecture, ageing and the marrow microenvironment modify disease expression.

Clinical Relevance: SF mutation status already informs classification and risk stratification in MDS, so UK haematologists should understand its biological basis when interpreting NGS myeloid panel results, though therapeutic translation remains unrealised.

Limitations: As a narrative review, it offers expert synthesis rather than new evidence, and the abstract gives no quantitative data or specific therapeutic findings.

Study Type: Translational/mechanistic study using multi-omic spatial profiling (snRNA-seq, ATAC-seq, Stereo-seq) of patient tissue; sample sizes not stated in abstract.

Key Question: What are the immune and molecular mechanisms driving EBV-positive lymphoproliferative disorder after CD7 CAR-T therapy (PCLD)?

Key Findings:

• Infiltrating T cells in PCLD are CD7-negative, with limited proliferative capacity and impaired anti-EBV activity, consistent with loss of effective viral surveillance.
• IDO1-high macrophages (Macro_IDO1) form spatially organised immunosuppressive niches that exclude T cells and are enriched for inhibitory signalling, including PD-1/PD-L1.
• Uncontrolled EBV infection of B cells drives plasmacytic differentiation, sustained proliferation and microenvironmental remodelling. PCLD was compared against PTLD, EBV-negative DLBCL and normal lymph nodes.

Clinical Relevance: As CD7 CAR-T is explored for T-cell malignancies, clinicians should anticipate EBV reactivation and LPD as a distinct post-therapy risk, with PD-1/IDO1 pathways emerging as candidate intervention targets.

Limitations: Abstract reports no cohort size, incidence, clinical outcomes or interventional data, so generalisability and therapeutic implications cannot be assessed.

Study Type: Retrospective cohort study (single analysis of paediatric SAA patients with targeted enhanced whole exome sequencing).

Key Question: In children with severe aplastic anaemia (SAA) and a negative standard clinical/laboratory workup for inherited bone marrow failure syndromes (IBMFS), is waiting for germline genetic testing justified?

Key Findings:

• Of 149 patients with complete clinical data, 113 (75.8%) had no IBMFS features; none carried pathogenic or likely pathogenic IBMFS variants.
• Among 36 patients (24.2%) with at least one suggestive clinical finding, one had a pathogenic heterozygous *SAMD9L* variant with a consistent history; another had two *ERCC6L2* pathogenic variants, but phasing (and so affected status) was undetermined.

Clinical Relevance: Supports starting definitive immunosuppressive or transplant-pathway treatment without delay for genetic results in children with a clean comprehensive workup, which is relevant to UK paediatric SAA pathways.

Limitations: Retrospective design; sequencing was IBMFS-gene-targeted, so non-exomic or novel genetic causes may have been missed.