Allogeneic Hematopoietic Cell Transplantation for Patients With Deficiency of Adenosine Deaminase 2 (DADA2): Approaches, Obstacles and Special Considerations.

Deficiency of adenosine deaminase 2 (DADA2) is an inherited autosomal recessive disease characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages, end organ vasculitis), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure. Allogeneic hematopoietic cell transplantation (HCT) is curative for DADA2 as it reverses the hematological, immune and vascular phenotype of DADA2. The primary goal of HCT in DADA2, like in other non-malignant diseases, is engraftment with the establishment of normal hematopoiesis and normal immune function. Strategies in selecting a preparative regimen should take into consideration the specific vulnerabilities to endothelial dysfunction and liver toxicity in DADA2 patients. Overcoming an increased risk of graft rejection while minimizing organ toxicity, graft-versus-host disease, and infections can be particularly challenging in DADA2 patients. This review will discuss approaches to HCT in DADA2 patients including disease-specific considerations, barriers to successful engraftment, post-HCT complications, and clinical outcomes of published patients with DADA2 who have undergone HCT to date.

Hashem H ，Dimitrova D ，Meyts I 《Frontiers in Immunology》

Hematopoietic Cell Transplantation Cures Adenosine Deaminase 2 Deficiency: Report on 30 Patients.

Deficiency of adenosine deaminase 2 (DADA2) is an inherited inborn error of immunity, characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure (BMF). Tumor necrosis factor (TNF-α) blockade is the treatment of choice for the vasculopathy, but often fails to reverse refractory cytopenia. We aimed to study the outcome of hematopoietic cell transplantation (HCT) in patients with DADA2. We conducted a retrospective study on the outcome of HCT in patients with DADA2. The primary outcome was overall survival (OS). Thirty DADA2 patients from 12 countries received a total of 38 HCTs. The indications for HCT were BMF, immune cytopenia, malignancy, or immunodeficiency. Median age at HCT was 9 years (range: 2-28 years). The conditioning regimens for the final transplants were myeloablative (n = 20), reduced intensity (n = 8), or non-myeloablative (n = 2). Donors were HLA-matched related (n = 4), HLA-matched unrelated (n = 16), HLA-haploidentical (n = 2), or HLA-mismatched unrelated (n = 8). After a median follow-up of 2 years (range: 0.5-16 years), 2-year OS was 97%, and 2-year GvHD-free relapse-free survival was 73%. The hematological and immunological phenotypes resolved, and there were no new vascular events. Plasma ADA2 enzyme activity normalized in 16/17 patients tested. Six patients required more than one HCT. HCT was an effective treatment for DADA2, successfully reversing the refractory cytopenia, as well as the vasculopathy and immunodeficiency. HCT is a definitive cure for DADA2 with > 95% survival.

Hashem H ，Bucciol G ，Ozen S ，Unal S ，Bozkaya IO ，Akarsu N ，Taskinen M ，Koskenvuo M ，Saarela J ，Dimitrova D ，Hickstein DD ，Hsu AP ，Holland SM ，Krance R ，Sasa G ，Kumar AR ，Müller I ，de Sousa MA ，Delafontaine S ，Moens L ，Babor F ，Barzaghi F ，Cicalese MP ，Bredius R ，van Montfrans J ，Baretta V ，Cesaro S ，Stepensky P ，Benedicte N ，Moshous D ，Le Guenno G ，Boutboul D ，Dalal J ，Brooks JP ，Dokmeci E ，Dara J ，Lucas CL ，Hambleton S ，Wilson K ，Jolles S ，Koc Y ，Güngör T ，Schnider C ，Candotti F ，Steinmann S ，Schulz A ，Chambers C ，Hershfield M ，Ombrello A ，Kanakry JA ，Meyts I ... -  《-》

Hematopoietic stem cell transplantation rescues the hematological, immunological, and vascular phenotype in DADA2.

Hashem H ，Kumar AR ，Müller I ，Babor F ，Bredius R ，Dalal J ，Hsu AP ，Holland SM ，Hickstein DD ，Jolles S ，Krance R ，Sasa G ，Taskinen M ，Koskenvuo M ，Saarela J ，van Montfrans J ，Wilson K ，Bosch B ，Moens L ，Hershfield M ，Meyts I ，Deficiency of Adenosine Deaminase Type 2 Foundation ... -  《-》

Human adenosine deaminase 2 deficiency: A multi-faceted inborn error of immunity.

Human adenosine deaminase 1 deficiency was described in the 1970s to cause severe combined immunodeficiency. The residual adenosine deaminase activity in these patients was attributed to adenosine deaminase 2. Human adenosine deaminase type 2 deficiency (DADA2), due to biallelic deleterious mutations in the ADA2 gene, is the first described monogenic type of small- and medium-size vessel vasculitis. The phenotype of DADA2 also includes lymphoproliferation, cytopenia, and variable degrees of immunodeficiency. The physiological role of ADA2 is still enigmatic hence the pathophysiology of the condition is unclear. Preliminary data showed that in the absence of ADA2, macrophage differentiation is skewed to a pro-inflammatory M1 subset, which is detrimental for endothelial integrity. The inflammatory phenotype responds well to anti-TNF therapy with etanercept and that is the first-line treatment for prevention of severe vascular events including strokes. The classic immunosuppressive drugs are not successful in controlling the disease activity. However, hematopoietic stem cell transplantation (HSCT) has been shown to be a definitive cure in DADA2 patients who present with a severe cytopenia. HSCT can also cure the vascular phenotype and is the treatment modality for patients' refractory to anti-cytokine therapies. In this review, we describe what is currently known about the molecular mechanisms of DADA2. Further research on the pathophysiology of this multifaceted condition is needed to fine-tune and steer future therapeutic strategies.

Moens L ，Hershfield M ，Arts K ，Aksentijevich I ，Meyts I ... -  《-》

The Spectrum of the Deficiency of Adenosine Deaminase 2: An Observational Analysis of a 60 Patient Cohort.

The deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessively inherited disease that has undergone extensive phenotypic expansion since being first described in patients with fevers, recurrent strokes, livedo racemosa, and polyarteritis nodosa in 2014. It is now recognized that patients may develop multisystem disease that spans multiple medical subspecialties. Here, we describe the findings from a large single center longitudinal cohort of 60 patients, the broad phenotypic presentation, as well as highlight the cohort's experience with hematopoietic cell transplantation and COVID-19. Disease manifestations could be separated into three major phenotypes: inflammatory/vascular, immune dysregulatory, and hematologic, however, most patients presented with significant overlap between these three phenotype groups. The cardinal features of the inflammatory/vascular group included cutaneous manifestations and stroke. Evidence of immune dysregulation was commonly observed, including hypogammaglobulinemia, absent to low class-switched memory B cells, and inadequate response to vaccination. Despite these findings, infectious complications were exceedingly rare in this cohort. Hematologic findings including pure red cell aplasia (PRCA), immune-mediated neutropenia, and pancytopenia were observed in half of patients. We significantly extended our experience using anti-TNF agents, with no strokes observed in 2026 patient months on TNF inhibitors. Meanwhile, hematologic and immune features had a more varied response to anti-TNF therapy. Six patients received a total of 10 allogeneic hematopoietic cell transplant (HCT) procedures, with secondary graft failure necessitating repeat HCTs in three patients, as well as unplanned donor cell infusions to avoid graft rejection. All transplanted patients had been on anti-TNF agents prior to HCT and received varying degrees of reduced-intensity or non-myeloablative conditioning. All transplanted patients are still alive and have discontinued anti-TNF therapy. The long-term follow up afforded by this large single-center study underscores the clinical heterogeneity of DADA2 and the potential for phenotypes to evolve in any individual patient.

Barron KS ，Aksentijevich I ，Deuitch NT ，Stone DL ，Hoffmann P ，Videgar-Laird R ，Soldatos A ，Bergerson J ，Toro C ，Cudrici C ，Nehrebecky M ，Romeo T ，Jones A ，Boehm M ，Kanakry JA ，Dimitrova D ，Calvo KR ，Alao H ，Kapuria D ，Ben-Yakov G ，Pichard DC ，Hathaway L ，Brofferio A ，McRae E ，Moura NS ，Schnappauf O ，Rosenzweig S ，Heller T ，Cowen EW ，Kastner DL ，Ombrello AK ... -  《Frontiers in Immunology》