Novel developments in the prophylaxis and treatment of acute GVHD

First-line treatment of severe aplastic anemia: immunosuppressive therapy plus eltrombopag versus haploidentical hematopoietic stem cell transplantation, a multicenter prospective study

Matched-related donor hematopoietic stem cell transplantation (HSCT) remains the preferred first-line option for severe aplastic anemia (SAA) patients aged <40 years even in the era of eltrombopag (EPAG). However, there has not been any direct comparison between immunosuppressive therapy (IST) plus EPAG (IST + EPAG) and haploidentical HSCT (Haplo-HSCT) as first-line therapy. This study prospectively compared the efficacy, safety and health-related quality of life (HRQoL) of Haplo-HSCT (n = 147) and IST + EPAG (n = 121) as first-line treatment for patients with SAA. The results showed that 86.3% of patients in the Haplo-HSCT group and 24.1% of patients in the IST + EPAG group achieved normal complete blood count (CBC) (P < 0.001) after 6 months of treatment. The time to achieve transfusion independence and absolute neutrophil count ≥ 1.0 × 109/L were shorter in the Haplo-HSCT group than in the IST + EPAG group (P < 0.05). In the IST + EPAG and Haplo-HSCT, 3-year overall survival (OS) was 92.4 ± 2.4% and 82.8 ± 3.1% (P = 0.017), whereas 3-year failure-free survival (FFS) was 69.4 ± 4.2% and 81.6 ± 3.2% (P = 0.002), respectively. Similar results were observed in patients with <40 years of age. Among patients with ≥40 years of age, there was no difference in 3-year OS (88.6 ± 4.8% vs. 82.4 ± 8.1%, P = 0.517) between the IST + EPAG and Haplo-HSCT groups, whereas 3-year FFS was lower in the IST + EPAG (58.7 ± 7.5% vs. 82.4 ± 8.1%, P = 0.043). Subgroup analysis for populations aged <40 years indicated that SAA benefited more from IST + EPAG, and very SAA (vSAA) benefited more from Haplo-HSCT. Patients treated with haplo-HSCT scored significantly better in the HRQoL than treated with IST + EPAG (P < 0.0001). Multivariate analysis showed that first-line Haplo-HSCT was associated with normal CBC at 6 months, better FFS and led to a better HRQoL (P < 0.001). In summary, the IST + EPAG achieved better OS for <40 years SAA patients, while the Haplo-HSCT accelerated hematopoietic recovery and HRQoL, achieved better FFS even for those <40 years vSAA and ≥40 years patients.

Post-Transplant Maintenance Therapy in Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (allo-HCT) is potentially curative for patients with acute myeloid leukemia (AML). However, the post-transplant relapse rate ranges from 40 to 70%, particularly with reduced intensity conditioning, and remains a major cause of treatment failure for these patients due to the limited efficacy of salvage therapy options. Strategies to mitigate this risk are urgently needed. In the past few years, the basic framework of post-transplant maintenance has been shaped by several clinical trials investigating targeted therapy, chemotherapy, and immunomodulatory therapies. Although the practice of post-transplant maintenance in AML has become more common, there remain challenges regarding the feasibility and efficacy of this strategy. Here, we review major developments in post-transplant maintenance in AML, along with ongoing and future planned studies in this area, outlining the limitations of available data and our future goals.

Inborn errors of immunity: A field without frontiers

The study of primary immunodeficiencies or inborn errors of immunity continues to drive our knowledge of the function of the human immune system. From the outset, the study of inborn errors has focused on unraveling genetic etiologies and molecular mechanisms. Aided by the continuous growth in genetic diagnostics, the field has moved from the study of an infection dominated phenotype to embrace and unravel diverse manifestations of autoinflammation, autoimmunity, malignancy, and severe allergy in all medical disciplines. It has now moved from the study of ultrarare presentations to producing meaningful impact in conditions as diverse as inflammatory bowel disease, neurological conditions, and hematology. Beyond offering immunogenetic diagnosis, the study of underlying inborn errors of immunity in these conditions points to targeted treatment which can be lifesaving.

CRISPR/Cas9 deletion of MIR155HG in human T cells reduces incidence and severity of acute GVHD in a xenogeneic model

ABSTRACT

Acute graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation (allo-HCT). Using preclinical mouse models of disease, previous work in our laboratory has linked microRNA-155 (miR-155) to the development of acute GVHD. Transplantation of donor T cells from miR-155 host gene (MIR155HG) knockout mice prevented acute GVHD in multiple murine models of disease while maintaining critical graft-versus-leukemia (GVL) response, necessary for relapse prevention. In this study, we used clustered, regularly interspaced, short palindromic repeats (CRISPR)/Cas9 genome editing to delete miR-155 in primary T cells (MIR155HGΔexon3) from human donors, resulting in stable and sustained reduction in expression of miR-155. Using the xenogeneic model of acute GVHD, we show that NOD/SCID/IL2rγnull (NSG) mice receiving MIR155HGΔexon3 human T cells provide protection from lethal acute GVHD compared with mice that received human T cells with intact miR-155. MIR155HGΔexon3 human T cells persist in the recipients displaying decreased proliferation potential, reduced pathogenic T helper-1 cell population, and infiltration into GVHD target organs, such as the liver and skin. Importantly, MIR155HGΔexon3 human T cells retain GVL response significantly improving survival in an in vivo model of xeno-GVL. Altogether, we show that CRISPR/Cas9-mediated deletion of MIR155HG in primary human donor T cells is an innovative approach to generate allogeneic donor T cells that provide protection from lethal GVHD while maintaining robust antileukemic response.

Separation of GVL from GVHD -location, location, location

Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for various hematologic malignancies. However, alloimmune response is a double-edged sword that mediates both beneficial graft-versus-leukemia (GVL) effects and harmful graft-versus-host disease (GVHD). Separation of GVL effects from GVHD has been a topic of intense research to improve transplant outcomes, but reliable clinical strategies have not yet been established. Target tissues of acute GVHD are the skin, liver, and intestine, while leukemic stem cells reside in the bone marrow. Tissue specific effector T-cell migration is determined by a combination of inflammatory and chemotactic signals that interact with specific receptors on T cells. Specific inhibition of donor T cell migration to GVHD target tissues while preserving migration to the bone marrow may represent a novel strategy to separate GVL from GVHD. Furthermore, tissue specific GVHD therapy, promoting tissue tolerance, and targeting of the tumor immune microenvironment may also help to separate GVHD and GVL.