Hematopoietic cell transplantation in Fanconi anemia: current evidence, challenges and recommendations

Hematopoiesis after anti-CD117 monoclonal antibody treatment in the settings of wild-type and Fanconi anemia mice

Anti-CD117 monoclonal antibody (mAb) agents have emerged as exciting alternative conditioning strategies to traditional genotoxic irradiation or chemotherapy for both allogeneic and autologous gene-modified hematopoietic stem cell transplantation. Furthermore, these agents are concurrently being explored in the treatment of mast cell disorders. Despite promising results in animal models and more recently in patients, the short- and long-term effects of these treatments have not been fully explored. We conducted rigorous assessments to evaluate the effects of an antagonistic anti-mCD117 mAb, ACK2, on hematopoiesis in wild-type and Fanconi anemia (FA) mice. Importantly, we found no evidence of short-term DNA damage in either setting following this treatment, suggesting that ACK2 does not induce immediate genotoxicity, providing crucial insights into its safety profile. Surprisingly, FA mice exhibited an increase in colony formation after ACK2 treatment, indicating a potential targeting of hematopoietic stem cells and expansion of hematopoietic progenitor cells. Moreover, the long-term phenotypic and functional changes in hematopoietic stem and progenitor cells did not differ significantly between the ACK2-treated and control groups, in either setting, suggesting that ACK2 does not adversely affect hematopoietic capacity. These findings underscore the safety of these agents when utilized as a short-course treatment in the context of conditioning, as they did not induce significant DNA damage in hematopoietic stem or progenitor cells. However, single-cell RNA sequencing, used to compare gene expression between untreated and treated mice, revealed that the ACK2 mAb, via c-Kit downregulation, effectively modulated the MAPK pathway with Fos downregulation in wild-type and FA mice. Importantly, this modulation was achieved without causing prolonged disruptions. These findings validate the safety of anti-CD117 mAb treatment and also enhance our understanding of its intricate mode of action at the molecular level.

International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the current state of hematopoietic stem and progenitor cell-based genomic therapies and the challenges faced

Genetic manipulation of hematopoietic stem cells (HSCs) is being developed as a therapeutic strategy for several inherited disorders. This field is rapidly evolving with several novel tools and techniques being employed to achieve desired genetic changes. While commercial products are now available for sickle cell disease, transfusion-dependent β-thalassemia, metachromatic leukodystrophy and adrenoleukodystrophy, several challenges remain in patient selection, HSC mobilization and collection, genetic manipulation of stem cells, conditioning, hematologic recovery and post-transplant complications, financial issues, equity of access and institutional and global preparedness. In this report, we explore the current state of development of these therapies and provide a comprehensive assessment of the challenges these therapies face as well as potential solutions.

Genomic testing for germline predisposition to hematologic malignancies

Germline predisposition (GPD) to hematological malignancies has gained interest because of the increased use of genetic testing in this field. Recent studies have suggested that GPD is underrecognized and requires appropriate genomic testing for an accurate diagnosis. Identification of GPD significantly affects patient management and has diverse implications for family members. This review discusses the reasons for testing GPD in hematologic malignancies and explores the considerations necessary for appropriate genomic testing. The aim is to provide insights into how these genetic insights can inform treatment strategies and genetic counseling, ultimately enhancing patient care.

Exploring the hub genes and potential drugs involved in Fanconi anemia using microarray datasets and bioinformatics analysis

Fanconi anemia (FA) is a genetic disorder that occurs when certain genes responsible for repairing DNA replication and promoting homologous recombination fail to function properly. This leads to severe clinical symptoms and a wide range of cancer-related characteristics. Recent treatment approaches for FA involve hematopoietic stem cell transplantation (HSCT), which helps restore the population of stem cells. A survival study using p-values indicated that specific hub genes play a significant role in diagnosing and predicting the disease. To find potential medications that interact with the identified hub genes, researchers inferred drugs. Among hub genes, TP53 was found to be particularly promising through computational analysis. Further investigation focused on two drugs, Topiramate and Tocofersolan predicted based on drug bank database analysis. Molecular docking strategies were employed to assess the best binding pose of these drugs with TP53. Topiramate showed a binding affinity of -6.5 kcal/mol, while Tocofersolan showed -8.5 kcal/mol against the active residues within the binding pocket. Molecular dynamics (MD) simulations were conducted to observe the stability of each drug's interaction with the TP53 protein over time. Both drugs exhibited stable confirmation with only slight changes in the loop region of the TP53 protein during the simulation intervals. Results also shows that there was a high fluctuation observed during apo-sate simulation time intervals as compared to complex system. Hence, it is suggested that the exploration of structure-based drug design holds promising results to specific target. This could potentially lead to a breakthrough in future experimental approaches for FA treatment.Communicated by Ramaswamy H. Sarma.

Management of Fanconi anemia beyond childhood

Fanconi anemia (FA) has long been considered a severe inherited bone marrow failure (BMF) disorder of early childhood. Thus, management of this multisystem disorder has previously been unfamiliar to many hematologists specializing in the care of adolescents and young adults (AYA). The increased diagnosis of FA in AYA patients, facilitated by widely available germline genomic testing, improved long-term survival of children with FA following matched sibling and alternative donor hematopoietic stem cell transplantation (HSCT) performed for BMF, and expanding need in the near future for long-term monitoring in patients achieving hematologic stabilization following ex vivo gene therapy are all reasons why management of FA in AYA populations deserves specific consideration. In this review, we address the unique challenges and evidence-based practice recommendations for the management of AYA patients with FA. Specific topics addressed include hematologic monitoring in AYA patients yet to undergo HSCT, management of myeloid malignancies occurring in FA, diagnosis and management of nonhematologic malignances and organ dysfunction in AYA patients with FA, and evolving considerations for the long-term monitoring of patients with FA undergoing gene therapy.

Posttransplant complications in patients with marrow failure syndromes: are we improving long-term outcomes?

Inherited bone marrow failure syndromes (IBMFS) encompass a group of rare genetic disorders characterized by bone marrow failure, non-hematologic multisystemic comorbidities, disease defining congenital anomalies, and a susceptibility to myelodysplastic syndrome, acute myeloid leukemia, and in some instances solid tumors. The most common IBMFS include Fanconi anemia, Shwachman-Diamond syndrome, Diamond-Blackfan anemia, and telomere biology disorders/ dyskeratosis congenita. Allogeneic hematopoietic stem cell transplant (HCT) is a well-established curative treatment to correct the hematological manifestations but does not halt or reverse the nonhematological complications and may hasten them. With advances in HCT and in our ability to care for patients with IBMFS, an increasing number of survivors are making it imperative to not only diagnose but also treat late effects from the pre-, peri-, and post-HCT course and complications relating to the natural history of the syndrome. As the field of HCT evolves to allow for the incorporation of alternate graft sources, for expansion of donor options to include unrelated and mismatched donors, and for use of reduced-intensity conditioning or reduced toxicity myeloablative regimens, we have yet to determine if these advances modify the disease-specific course. While long-term outcomes of these patients are often included under one umbrella, this article seeks to address disease-specific post-HCT outcomes within IBMFS.

Minimal intensity conditioning strategies for bone marrow failure: is it time for "preventative" transplants?

Hematopoietic cell transplantation (HCT) can cure blood dyscrasias and reduce the risk of hematologic cancers in patients with inherited bone marrow failure syndromes (IBMFS). However, because of its high mortality rate, HCT is generally reserved until patients with IBMFS manifest life-threatening cytopenias or myeloid malignancy, at which point outcomes are poor. Screening tests that accurately predict transformation and enable timely intervention are lacking. These unknowns and risks limit the use of HCT in patients with IBMFS, sometimes until significant disease-related sequelae have occurred. A major goal for IBMFS is to reduce cellular therapy-related complications to the point that earlier intervention can be considered before significant transfusion exposure, occurrence of comorbidities, or malignant transformation. In recent decades, disease-specific allogeneic HCT trials have yielded significant improvements in outcomes in IBMFS conditions, including Fanconi anemia and dyskeratosis congenita. This is in large part due to marked reductions in conditioning intensity to address the increased sensitivity of these patients to cytotoxic chemotherapy and radiation. The success of these approaches may also indicate an ability to leverage intrinsic fitness defects of hematopoietic stem and progenitor cells across IBMFS disorders. Now with advances in tracking somatic genetic evolution in hematopoiesis and tailored minimal intensity conditioning regimens, this question arises: is it time for preventative HCT for IBMFS?

Pediatric Bone Marrow Failure: A Broad Landscape in Need of Personalized Management

Irreversible severe bone marrow failure (BMF) is a life-threatening condition in pediatric patients. Most important causes are inherited bone marrow failure syndromes (IBMFSs) and (pre)malignant diseases, such as myelodysplastic syndrome (MDS) and (idiopathic) aplastic anemia (AA). Timely treatment is essential to prevent infections and bleeding complications and increase overall survival (OS). Allogeneic hematopoietic stem cell transplantation (HSCT) provides a cure for most types of BMF but cannot restore non-hematological defects. When using a matched sibling donor (MSD) or a matched unrelated donor (MUD), the OS after HSCT ranges between 60 and 90%. Due to the introduction of post-transplantation cyclophosphamide (PT-Cy) to prevent graft versus host disease (GVHD), alternative donor HSCT can reach similar survival rates. Although HSCT can restore ineffective hematopoiesis, it is not always used as a first-line therapy due to the severe risks associated with HSCT. Therefore, depending on the underlying cause, other treatment options might be preferred. Finally, for IBMFSs with an identified genetic etiology, gene therapy might provide a novel treatment strategy as it could bypass certain limitations of HSCT. However, gene therapy for most IBMFSs is still in its infancy. This review summarizes current clinical practices for pediatric BMF, including HSCT as well as other disease-specific treatment options.

Chemical Carcinogen (Dimethyl-benzanthracene) Induced Transplantable Cancer in Fanconi Anemia (Fanca-/-) Mice

BACKGROUND/AIM

Patients with radiation sensitive Fanconi anemia (FA) are presenting with cancers of the oral cavity, oropharynx, and other anatomic locations.

MATERIALS AND METHODS

Animal models for cancer in FA mice used orthotopic tumors from wild type mice. We derived a cancer cell line from Fanca-/- mice by topical application of the chemical carcinogen dimethyl benzanthracene (DMBA).

RESULTS

A Fanca-/- mouse rhabdomyosarcoma was derived from a Fanca-/- (129/Sv) mouse. The in vitro clonogenic survival of the Fanca-/- clone 6 cancer cell line was consistent with the FA genotype. Transplanted tumors demonstrated hypoxic centers surrounded by senescent cells.

CONCLUSION

This Fanca-/- mouse syngeneic cancer should provide a valuable resource for discovery and development of new normal tissue radioprotectors for patients with FA and cancer.

Clinical considerations at the intersection of hematopoietic cell transplantation and hereditary hematopoietic malignancy

In recent years, advances in genetics and the integration of clinical-grade next-generation sequencing (NGS) assays into patient care have facilitated broader recognition of hereditary hematopoietic malignancy (HHM) among clinicians, in addition to the identification and characterization of novel HHM syndromes. Studies on genetic risk distribution within affected families and unique considerations of HHM biology represent exciting areas of translational research. More recently, data are now emerging pertaining to unique aspects of clinical management of malignancies arising in the context of pathogenic germline mutations, with particular emphasis on chemotherapy responsiveness. In this article, we explore considerations surrounding allogeneic transplantation in the context of HHMs. We review pre- and post-transplant patient implications, including genetic testing donor selection and donor-derived malignancies. Additionally, we consider the limited data that exist regarding the use of transplantation in HHMs and safeguards that might be pursued to mitigate transplant-related toxicities.

Germline Predisposition to Myelodysplastic Syndromes

ABSTRACT

While germline predisposition to myelodysplastic syndromes is well-established, knowledge has advanced rapidly resulting in more cases of inherited hematologic malignancies being identified. Understanding the biological features and main clinical manifestations of hereditary hematologic malignancies is essential to recognizing and referring patients with myelodysplastic syndrome, who may underlie inherited predisposition, for appropriate genetic evaluation. Importance lies in individualized genetic counseling along with informed treatment decisions, especially with regard to hematopoietic stem cell transplant-related donor selection. Future studies will improve comprehension of these disorders, enabling better management of affected patients and their families.

Fanconi anemia phenotypic and transplant outcomes' associations in Iranian patients

Objectives

Fanconi anemia (FA) is a rare, heterogeneous, inherited disorder. Allogeneic hematopoietic stem cell transplantation (HSCT) represents the only therapeutic option to restore normal hematopoiesis. This study reports the outcomes of FA‐HSCT patients and identifies factors, including clinical phenotype. Our team examined more than 95% of Iranian FA patients during the last decade.

Study Design

One hundred and six FA patients (age range: 2–41) who underwent HSCT from March 2007 to February 2018 were enrolled. Clinical characteristics of genetic disease, pre‐HSCT findings, HSCT indication, and long‐term follow‐up evaluated and recorded. Data were analyzed using SPSS 19.0.

Results

The mean follow‐up period for survivors was 36 months (range, 1–101). The 3‐year overall survival (OS) and disease‐free survival were 72.2% and 71.2%, respectively. The 3‐year OS rate for patients with limited and extensive malformations was 78.8% and 56.6%, respectively (p = 0.025). Acute graft versus host disease incidence was 60.52% for patients with limited malformations versus 70% for patients with extensive ones (p = 0.49). Chronic graft versus host disease incidence for these two groups was 9.21% and 10%, respectively (p = 0.91).

Conclusions

OS was not associated with each of the malformations singly; however, it was lower in the extensive group. The younger age of patients at the HSCT time leads to a higher OS. The differences in FA patients' outcomes and the various genotypes were probably related. These data provide a powerful tool for further studies on genotype–phenotype association with HSCT results.

The younger age of FA patients at the HSCT time leads to a higher OS.

OS was lower in the congenital malformations extensive group.

The malformations’ scope affects aGvHD incidence significantly, while not cGvHD.

Various HSCT outcomes in different centers can be due to distinct genotypes.

European standard clinical practice - Key issues for the medical care of individuals with familial leukemia

Although hematologic malignancies (HM) are no longer considered exclusively sporadic, additional awareness of familial cases has yet to be created. Individuals carrying a (likely) pathogenic germline variant (e.g., in ETV6, GATA2, SAMD9, SAMD9L, or RUNX1) are at an increased risk for developing HM. Given the clinical and psychological impact associated with the diagnosis of a genetic predisposition to HM, it is of utmost importance to provide high-quality, standardized patient care. To address these issues and harmonize care across Europe, the Familial Leukemia Subnetwork within the ERN PaedCan has been assigned to draft an European Standard Clinical Practice (ESCP) document reflecting current best practices for pediatric patients and (healthy) relatives with (suspected) familial leukemia. The group was supported by members of the German network for rare diseases MyPred, of the Host Genome Working Group of SIOPE, and of the COST action LEGEND. The ESCP on familial leukemia is proposed by an interdisciplinary team of experts including hematologists, oncologists, and human geneticists. It is intended to provide general recommendations in areas where disease-specific recommendations do not yet exist. Here, we describe key issues for the medical care of familial leukemia that shall pave the way for a future consensus guideline: (i) identification of individuals with or suggestive of familial leukemia, (ii) genetic analysis and variant interpretation, (iii) genetic counseling and patient education, and (iv) surveillance and (psychological) support. To address the question on how to proceed with individuals suggestive of or at risk of familial leukemia, we developed an algorithm covering four different, partially linked clinical scenarios, and additionally a decision tree to guide clinicians in their considerations regarding familial leukemia in minors with HM. Our recommendations cover, not only patients but also relatives that both should have access to adequate medical care. We illustrate the importance of natural history studies and the need for respective registries for future evidence-based recommendations that shall be updated as new evidence-based standards are established.

Inherited bone marrow failure syndromes: a review of current practices and potential future research directions

PURPOSE OF REVIEW

Recent advances in diagnosis and treatment of inherited bone marrow failure syndromes (IBMFS) have significantly improved disease understanding and patient outcomes. Still, IBMFS present clinical challenges that require further progress. This review aims to provide an overview of the current state of diagnosis and treatment modalities of the major IBMFS seen in paediatrics and present areas of prioritization for future research.

RECENT FINDINGS

Haematopoietic cell transplantation (HCT) for IBMFS has greatly improved in recent years, shifting the research and clinical focus towards cancer predispositions and adverse effects of treatment. Each year, additional novel genes and pathogenic variants are described, and genotype-phenotype mapping becomes more sophisticated. Moreover, novel therapeutics exploring disease-specific mechanisms show promise to complement HCT and treat patients who cannot undergo current treatment options.

SUMMARY

Research on IBMFS should have short-term and long-term goals. Immediate challenges include solidifying diagnostic and treatment guidelines, cancer detection and treatment, and continued optimization of HCT. Long-term goals should emphasize genotype-phenotype mapping, genetic screening tools and gene-targeted therapy.

Germ line predisposition variants occur in myelodysplastic syndrome patients of all ages

The frequency of pathogenic/likely pathogenic (P/LP) germ line variants in patients with myelodysplastic syndrome (MDS) diagnosed at age 40 years or less is 15% to 20%. However, there are no comprehensive studies assessing the frequency of such variants across the age spectrum. We performed augmented whole-exome sequencing of peripheral blood samples from 404 patients with MDS and their related donors before allogeneic hematopoietic stem cell transplantation. Single-nucleotide and copy number variants in 233 genes were analyzed and interpreted. Germ line status was established by the presence of a variant in the patient and related donor or for those seen previously only as germ line alleles. We identified P/LP germ line variants in 28 of 404 patients with MDS (7%), present within all age deciles. Patients with P/LP variants were more likely to develop higher-grade MDS than those without (43% vs 25%; P = .04). There was no statistically significant difference in outcome parameters between patients with and without a germ line variant, but the analysis was underpowered. P/LP variants in bone marrow failure syndrome genes were found in 5 patients aged less than 40 years, whereas variants in DDX41 (n = 4), telomere biology disorder genes (n = 2), and general tumor predisposition genes (n = 17) were found in patients aged more than 40 years. If presumed germ line variants were included, the yield of P/LP variants would increase to 11%, and by adding suspicious variants of unknown significance, it would rise further to 12%. The high frequency of P/LP germ line variants in our study supports comprehensive germ line genetic testing for all patients with MDS regardless of their age at diagnosis.

Modern management of Fanconi anemia

In this review, we present a clinical case report and discussion to outline the importance of long-term specific Fanconi anemia (FA) monitoring, and we discuss the main aspects of the general management of patients with FA and clinical complications. While several nontransplant treatments are currently under evaluation, hematopoietic stem cell transplantation (HSCT) remains the only therapeutic option for bone marrow failure (BMF). Although HSCT outcomes in patients with FA have remarkably improved over the past 20 years, in addition to the mortality intrinsic to the procedure, HSCT increases the risk and accelerates the appearance of late malignancies. HSCT offers the best outcome when performed in optimal conditions (moderate cytopenia shifting to severe, prior to transfusion dependence and before clonal evolution or myelodysplasia/acute myeloid leukemia); hence, an accurate surveillance program is vital. Haploidentical HSCT offers very good outcomes, although long-term effects on malignancies have not been fully explored. A monitoring plan is also important to identify cancers, particularly head and neck carcinomas, in very early phases. Gene therapy is still experimental and offers the most encouraging results when performed in early phases of BMF by infusing high numbers of corrected cells without genotoxic effects. Patients with FA need comprehensive monitoring and care plans, coordinated by centers with expertise in FA management, that start at diagnosis and continue throughout life. Such long-term follow-up is essential to detect complications related to the disease or treatment in this setting.

Inherited bone marrow failure in the pediatric patient

Inherited bone marrow (BM) failure syndromes are a diverse group of disorders characterized by BM failure, usually in association with ≥1 extrahematopoietic abnormalities. BM failure, which can involve ≥1 cell lineages, often presents in the pediatric age group. Furthermore, some children initially labeled as having idiopathic aplastic anemia or myelodysplasia represent cryptic cases of inherited BM failure. Significant advances in the genetics of these syndromes have been made, identifying more than 100 disease genes, giving insights into normal hematopoiesis and how it is disrupted in patients with BM failure. They have also provided important information on fundamental biological pathways, including DNA repair: Fanconi anemia (FA) genes; telomere maintenance: dyskeratosis congenita (DC) genes; and ribosome biogenesis: Shwachman-Diamond syndrome and Diamond-Blackfan anemia genes. In addition, because these disorders are usually associated with extrahematopoietic abnormalities and increased risk of cancer, they have provided insights into human development and cancer. In the clinic, genetic tests stemming from the recent advances facilitate diagnosis, especially when clinical features are insufficient to accurately classify a disorder. Hematopoietic stem cell transplantation using fludarabine-based protocols has significantly improved outcomes, particularly in patients with FA or DC. Management of some other complications, such as cancer, remains a challenge. Recent studies have suggested the possibility of new and potentially more efficacious therapies, including a renewed focus on hematopoietic gene therapy and drugs [transforming growth factor-β inhibitors for FA and PAPD5, a human poly(A) polymerase, inhibitors for DC] that target disease-specific defects.

Does immune destruction drive all forms of bone marrow failure?

Current paradigms of bone marrow failure (BMF) pathophysiology suggest that immune-mediated destruction of hematopoietic stem and progenitor cells (HSPCs) drives acquired aplastic anemia. In contrast, loss of HSPCs due to senescence and/or apoptosis causes BMF in inherited BMF syndromes. In this issue of the JCI, Casado and colleagues challenge this dichotomous conception by demonstrating that NK cell–dependent, immune-mediated hematopoietic suppression and HSPC clearance drive BMF in Fanconi anemia (FA). They show that genotoxic stress upregulates natural killer group 2 member D ligands (NKG2D-L) on FA HSPCs leading to NK cell cytotoxicity through NKG2D receptor activation. Inhibition of NKG2D–NKG2D-L interactions enhanced FA HSPC clonogenic potential and improved cytopenias in vivo. These results provide alternative targets for the development of immunosuppressive therapies to reduce HSPC loss and mitigate the risk of hematologic malignancies in FA.

Correction of Fanconi Anemia Mutations Using Digital Genome Engineering

Fanconi anemia (FA) is a rare genetic disease in which genes essential for DNA repair are mutated. Both the interstrand crosslink (ICL) and double-strand break (DSB) repair pathways are disrupted in FA, leading to patient bone marrow failure (BMF) and cancer predisposition. The only curative therapy for the hematological manifestations of FA is an allogeneic hematopoietic cell transplant (HCT); however, many (>70%) patients lack a suitable human leukocyte antigen (HLA)-matched donor, often resulting in increased rates of graft-versus-host disease (GvHD) and, potentially, the exacerbation of cancer risk. Successful engraftment of gene-corrected autologous hematopoietic stem cells (HSC) circumvents the need for an allogeneic HCT and has been achieved in other genetic diseases using targeted nucleases to induce site specific DSBs and the correction of mutated genes through homology-directed repair (HDR). However, this process is extremely inefficient in FA cells, as they are inherently deficient in DNA repair. Here, we demonstrate the correction of FANCA mutations in primary patient cells using ‘digital’ genome editing with the cytosine and adenine base editors (BEs). These Cas9-based tools allow for C:G > T:A or A:T > C:G base transitions without the induction of a toxic DSB or the need for a DNA donor molecule. These genetic corrections or conservative codon substitution strategies lead to phenotypic rescue as illustrated by a resistance to the alkylating crosslinking agent Mitomycin C (MMC). Further, FANCA protein expression was restored, and an intact FA pathway was demonstrated by downstream FANCD2 monoubiquitination induction. This BE digital correction strategy will enable the use of gene-corrected FA patient hematopoietic stem and progenitor cells (HSPCs) for autologous HCT, obviating the risks associated with allogeneic HCT and DSB induction during autologous HSC gene therapy.

Metformin for treatment of cytopenias in children and young adults with Fanconi anemia

Fanconi anemia (FA), a genetic DNA repair disorder characterized by marrow failure and cancer susceptibility. In FA mice, metformin improves blood counts and delays tumor development. We conducted a single institution study of metformin in nondiabetic patients with FA to determine feasibility and tolerability of metformin treatment and to assess for improvement in blood counts. Fourteen of 15 patients with at least 1 cytopenia (hemoglobin < 10 g/dL; platelet count < 100 000 cells/µL; or an absolute neutrophil count < 1000 cells/µL) were eligible to receive metformin for 6 months. Median patient age was 9.4 years (range 6.0-26.5 ). Thirteen of 14 subjects (93%) tolerated maximal dosing for age; 1 subject had dose reduction for grade 2 gastrointestinal symptoms. No subjects developed hypoglycemia or metabolic acidosis. No subjects had dose interruptions caused by toxicity, and no grade 3 or higher adverse events attributed to metformin were observed. Hematologic response based on modified Myelodysplastic Syndrome International Working Group criteria was observed in 4 of 13 evaluable patients (30.8%; 90% confidence interval, 11.3-57.3). Median time to response was 84.5 days (range 71-128 days). Responses were noted in neutrophils (n = 3), platelets (n = 1), and red blood cells (n = 1). No subjects met criteria for disease progression or relapse during treatment. Correlative studies explored potential mechanisms of metformin activity in FA. Plasma proteomics showed reduction in inflammatory pathways with metformin. Metformin is safe and tolerable in nondiabetic patients with FA and may provide therapeutic benefit. This trial was registered at as #NCT03398824.

Upregulation of NKG2D ligands impairs hematopoietic stem cell function in Fanconi anemia

Fanconi anemia (FA) is the most prevalent inherited bone marrow failure (BMF) syndrome. Nevertheless, the pathophysiological mechanisms of BMF in FA have not been fully elucidated. Since FA cells are defective in DNA repair, we hypothesized that FA hematopoietic stem and progenitor cells (HSPCs) might express DNA damage–associated stress molecules such as natural killer group 2 member D ligands (NKG2D-Ls). These ligands could then interact with the activating NKG2D receptor expressed in cytotoxic NK or CD8⁺ T cells, which may result in progressive HSPC depletion. Our results indeed demonstrated upregulated levels of NKG2D-Ls in cultured FA fibroblasts and T cells, and these levels were further exacerbated by mitomycin C or formaldehyde. Notably, a high proportion of BM CD34⁺ HSPCs from patients with FA also expressed increased levels of NKG2D-Ls, which correlated inversely with the percentage of CD34⁺ cells in BM. Remarkably, the reduced clonogenic potential characteristic of FA HSPCs was improved by blocking NKG2D–NKG2D-L interactions. Moreover, the in vivo blockage of these interactions in a BMF FA mouse model ameliorated the anemia in these animals. Our study demonstrates the involvement of NKG2D–NKG2D-L interactions in FA HSPC functionality, suggesting an unexpected role of the immune system in the progressive BMF that is characteristic of FA.

Genotype-phenotype and outcome associations in patients with Fanconi anemia: the National Cancer Institute cohort

Fanconi anemia (FA) is caused by pathogenic variants in the FA/BRCA DNA repair pathway genes, and is characterized by congenital abnormalities, bone marrow failure (BMF) and increased cancer risk. We conducted a genotype-phenotype and outcomes study of 203 patients with FA in our cohort. We compared across the genes, FA/BRCA DNA repair pathways (upstream, ID complex and downstream), and type of pathogenic variants (hypomorphic or null). We explored differences between the patients evaluated in our clinic (clinic cohort) and those who provided data remotely (field cohort). Patients with variants in upstream complex pathway had less severe phenotype [lacked VACTERL-H (Vertebral, Anal, Cardiac, Trachea-esophageal fistula, Esophageal/duodenal atresia, Renal, Limb, Hydrocephalus) association and/or PHENOS (Pigmentation, small-Head, small-Eyes, Neurologic, Otologic, Short stature) features]. ID complex was associated with VACTERL-H. The clinic cohort had more PHENOS features than the field cohort. PHENOS was associated with increased risk of BMF, and VACTERL-H with hypothyroidism. The cumulative incidence of severe BMF was 70%, solid tumors (ST) 20% and leukemia 6.5% as the first event. Head and neck and gynecological cancers were the most common ST, with further increased risk after hematopoietic cell transplantation. Among patients with FANCA, variants in exons 27-30 were associated with higher frequency of ST. Overall median survival was 37 years; patients with leukemia or FANCD1/BRCA2 variants had poorest survival. Patients with variants in the upstream complex had better survival than ID or downstream complex (p=0.001 and 0.016, respectively). FA is phenotypically and genotypically heterogeneous; detailed characterization provides new insights towards understanding this complex syndrome and guiding clinical management.

Kidney complications in 107 Fanconi anemia patients submitted to hematopoietic cell transplantation

Fanconi anemia (FA) is a rare disease characterized by progressive bone marrow failure, cancer predisposition, and multiple systemic malformations, including congenital abnormalities of the kidney and urinary tract (CAKUT). Hematopoietic cell transplantation (HCT), the only potentially curative treatment for the hematological complications of FA, may precipitate acute kidney injury (AKI) and hypertension. We retrospectively investigated 107 FA patients who underwent HCT between 2009 and 2017. We investigated the incidence and risk factors of AKI within 100 days after HCT in a cohort of FA patients, and kidney function and hypertension over 2-year follow-up.The incidence of AKI (mainly stage I) was 18.7%. Patients aged ≥ 11 years at transplantation showed a higher risk of AKI (OR 3.53). The eGFR was 60-90 mL/min/1.73 m² in 53 (49.5%), 55 (51.4%), 50 (50.5%), 50 (51%), and 46 (59.7%) patients before HCT, at 100 days, 6 months, 1 year, and 2 years. Within the first 100 days after HCT, hypertension was observed in 72% of the patients and was associated with cyclosporine therapy. Most (62.3%) patients had stage 2 hypertension. CAKUT was observed in 33.7% of the patients and was associated with both hypertension (86%) and diminished kidney function but not with AKI.Conlusion: Although AKI, a commonly known HCT complication, was mild in this study, the prevalence of chronic kidney disease (CKD), as well as the high incidence of hypertension, specially associated with CAKUT point out the importance of kidney care in short and long-term follow up of FA patients. What is Known: • Fanconi anemia (FA) is the most frequent inherited bone marrow failure in children, and 30% of cases have congenital anomalies of kidney (CAKUT). • Acute kidney injury and hypertension after hematopoietic cell transplantation (HCT) may impact the outcomes.. What is New: • Despite the presence of CAKUT and stage 2 CKD in 33.7% and 50% of the patients, respectively, AKI was mild and transitory after HCT in FA patients. • CAKUT in FA patients was associated with lower kidney function and hypertension after HCT.

Fanconi anemia and hematopoietic stem cell transplant as risk factors for oral squamous cell carcinoma: A case report with a 12-year follow-up

Fanconi anemia is a rare disorder resulting from defects in genes responsible for DNA damage responses. It is characterized by congenital anomalies, aplastic anemia, and a predisposition to cancer. Currently, hematopoietic stem cell transplant (HSCT) is the only curative treatment available for bone marrow failure; however, HSCT increases oral squamous cell carcinoma (OSCC) risk. Here we report the case of a patient diagnosed with Fanconi anemia in childhood who was treated with HSCT and later diagnosed with multiple OSCCs during a 12-year follow-up. Despite multiple surgical interventions and radiotherapy regimens, the patient`s health deteriorated. Management of individuals with Fanconi anemia is challenging and must be provided by a multidisciplinary healthcare team to ensure better staging, treatment planning, and coordination.

Hematopoietic stem cell transplantation for classical inherited bone marrow failure syndromes: an update

INTRODUCTION

Inherited bone marrow failure syndromes (IBMFS) feature complex molecular pathophysiology resulting in ineffective hematopoiesis and increased risk of progression to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Allogenic hematopoietic stem cell transplantation (HSCT) is the only well-established cure for the hematological manifestations of these diseases.

AREAS COVERED

In recent years, analysis of large series from international databases (mainly from the European Bone Marrow Transplantation [EBMT] database) has improved knowledge about HSCT in IBMFS. This review, following a thorough Medline search of the pertinent published studies, reports the most recent data on HSCT in IBMFS.

EXPERT OPINION

Despite the common features, IBMFS are very different in their manifestations and in the occurrence and management of HSCT complications. Thus, a 'disease-specific' HSCT using an optimized conditioning regimen based on the characteristics of the disease is essential for achieving long-term survival. The phenotypical heterogeneity associated with extramedullary abnormalities has to be carefully evaluated before HSCT because transplantation may only correct impaired hematopoiesis. HSCT may be associated with the risk of treatment-related mortality and with significant early and late morbidity. For these reasons, the benefits should be carefully weighed against the risks.

Oral and Dental Manifestations of Fanconi Anemia

Fanconi anemia is a rare disease, which is characterized by decreased production of all blood cell types. Fanconi anemia is the most common inherited form of aplastic anemia. Congenital abnormalities of the eyes, ears, and heart, malformed or absent kidney, urogenital system involvement are common. There is a delay in physical development. Intelligence in patients with Fanconi anemia is usually normal. The most serious problems associated with Fanconi anemia include the gradual development of bone marrow disorders. Many patients with Fanconi anemia develop leukemia or myelodysplastic syndrome, as well as other oncological diseases. Oral manifestations in patients with Fanconi anemia can be classified as gingivitis, periodontitis, dental caries, dental anomalies, soft tissue lesions, oral cancer, and lesions of the tongue. Patients with Fanconi anemia have increased predisposition to squamous cell carcinoma of the head and neck and oral cancer. The interdisciplinary team of medical and dental specialists must be included in the medical and dental treatment of patients with Fanconi anemia. For proper dental care of patients with Fanconi anemia, the close cooperation of dental specialists, including orthodontists, pedodontists, prosthetists, oral surgeons, as well as specialists in periodontology and oral diseases, is of particular importance.

An update on Fanconi anemia: Clinical, cytogenetic and molecular approaches (Review)

Fanconi anemia is a genetic syndrome clinically characterized by congenital malformations that affect several human systems, leads to progressive bone marrow failure and predisposes an individual to cancer, particularly in the urogenital area as well as the head and neck. It is commonly caused by the biallelic compromise of one of 22 genes involved in the FA/BRCA repair pathway in most cases. The diagnosis is based on clinical suspicion and confirmation using genetic analysis, where the chromosomal breakage test is considered the gold standard. Other diagnostic methods used include western blotting, multiplex ligation-dependent probe amplification and next-generation sequencing. This genetic condition has variable expressiveness, which makes early diagnosis difficult in certain cases. Although early diagnosis does not currently allow for improved cure rates for this condition, it does enable healthcare professionals to perform a specific systematic follow-up and, if indicated, a bone marrow transplantation that improves the mobility and mortality of affected individuals. The present review article is a theoretical revision of the pathophysiology, clinical manifestations and diagnosis methods intended for different specialists and general practitioners to improve the diagnosis of this condition.

Bone marrow transplant using fludarabine-based reduced intensity conditioning regimen with in vivo T cell depletion in patients with Fanconi anemia

FA is the most common cause of inherited BMF syndromes. The only cure for BMF in FA remains HSCT. Due to DNA instability in FA, RIC has been used to decrease immediate and late complications of HSCT. Most FA conditioning regimens in mismatched and unrelated donor transplants rely on TBI, which increases the risk of secondary malignancies. Most of the non-TBI conditioning regimens use an ex vivo T-cell depletion approach, but this is not feasible at all pediatric stem cell transplant programs. To evaluate the success of HSCT in patients with FA using non-TBI conditioning regimens with in vivo T-cell depletion approach. HSCT using non-TBI based conditioning was performed on two siblings with FA. The first sibling underwent matched unrelated donor transplant with a BM graft using fludarabine, alemtuzumab, busulfan, and cyclophosphamide conditioning and cyclosporine and mycophenolate as GVHD prophylaxis. The second sibling underwent MSD transplant with UCB and BM grafts using similar approach, but without busulfan and mycophenolate. Both siblings had engraftment without signs of acute or chronic GVHD. Acute post-transplant complications included brief viral reactivations. At last follow-up, both siblings continued to have full immune reconstitution with stable chimerism. Conditioning regimens without radiation and inclusion of alemtuzumab can lead to successful engraftment without development of GVHD and reduce risk of developing secondary neoplasms, even with unrelated donor transplants.

Hematopoietic stem cell transplantation for inherited bone marrow failure syndromes: alternative donor and disease-specific conditioning regimen with unmanipulated grafts

Objective: The outcomes of alternative donor hematopoietic stem cell transplantation (HSCT) with unmanipulated grafts for Inherited bone marrow failure syndromes (IBMFS) are discouraging. Our study is to demonstrate that IBMFS with disease-specific characteristics requires a tailored conditioning regimens to enhance engraftment and reduce regimen related toxicities. Methods: We retrospectively analyzed 42 patients diagnosed with IBMFS and transplanted with an alternative donor graft at our center from November 2012 to August 2018. Twenty-seven patients had Fanconi anemia (FA), 7 had dyskeratosis congenita (DC), and 8 had severe congenital neutropenia (SCN). Patients received ex-vivo unmanipulated alternative donor grafts from a matched unrelated donor (MUD) (n = 22), haploidentical donor (HID) (n = 17) and unrelated cord blood donor (UCBD) (n = 3). FA and DC patient subgroups received reduce intensified conditioning (RIC), while SCN patients received a myeloablative conditioning (MAC) regimen. Results: The median follow-up time for the surviving patients was 38 months (range: 9-63 months). The failure-free survival (FFS) for entire cohort was 76.1%, and was 72.4%, 100% and 56.2% for patients with FA, DC and SCN, respectively. There were no primary graft failures. The cumulative incidence of aGVHD at day 100 was 48.1%. The cumulative incidence of cGVHD at 1 and 3 years was 35.0% and 69.3%, respectively. Conclusion: HSCT using alternative donors with unmanipulated grafts and disease-specific conditioning regimens for IBMFS patients shows promising survival.

Use of the cell division assay to diagnose Fanconi anemia patients' hypersensitivity to mitomycin C

The recently reported cell division assay (CDA) was optimized to measure the relative sensitivity of cells to cytotoxic drugs in vitro. Here, we investigated the in vitro hypersensitivity of lymphocytes from Fanconi anemia (FA) patients, to cytotoxic drugs using CDA. Peripheral blood mononuclear cells (PBMC) as well as cell lines derived from FA patients were treated with two DNA interstrand crosslinking (ICL) agents, mitomycin C and cyclophosphamide. Our data indicate that the CDA detects hypersensitivity of cells from FA patients to mitomycin C. Further, cell lines derived from FA-patients were also hypersensitive to mitomycin C as well as cyclophosphamide, when assayed by the CDA. This study suggests that the CDA is a useful alternative for the diagnosis of FA patients' hypersensitivity to ICL agents.

Excellent overall and chronic graft-versus-host-disease-free event-free survival in Fanconi anaemia patients undergoing matched related- and unrelated-donor bone marrow transplantation using alemtuzumab-Flu-Cy: the UK experience

Haematopoietic stem cell transplantation (HSCT) remains the only curative option in Fanconi anaemia (FA). We analysed the outcome of children transplanted for FA between 1999 and 2018 in the UK. A total of 94 transplants were performed in 82 patients. Among the donors, 51·2% were matched related donors (MRD) while the remainder were alternative donors. Most patients received a fludarabine-cyclophosphamide (Flu-Cy)-based conditioning regimen (86·6%) and in vivo T-cell depletion with alemtuzumab (69·5%). Five-year overall survival (OS) was 85·4% [70·4-93.2] with MRD, 95·7% [72·9-99.4] with matched unrelated donors (MUD), 44·4% [6·6-78.5] with mismatched unrelated donors (MMUD) and 44·4% [13·6-71.9] with mismatched related donors (MMRD) (P < 0·001). Other factors significantly impacting OS were pre-transplant bone marrow status, source of stem cells, cytomegalovirus (CMV) serostatus, preparation with Flu-Cy, use of total body irradiation (TBI) and alemtuzumab as serotherapy. In multivariate analysis, absence of myelodysplastic syndrome (MDS) or leukaemia, bone marrow as source of stem cells, cytomegalovirus (CMV) other than +/- (Recipient/Donor) and Flu-Cy were protective factors for five-year OS. Five-year chronic graft-versus-host-disease (cGVHD)-free event-free survival was 75·4% with the same risk factors except for CMV serostatus. Five-year non-relapse mortality was 13·8% [7·3-22.3]. Only five patients (6·1%) developed grade II-IV acute GVHD and two patients chronic GVHD. These data confirm the excellent outcome of matched related or unrelated HSCT in children with FA.

Targeted gene panels identify a high frequency of pathogenic germline variants in patients diagnosed with a hematological malignancy and at least one other independent cancer

The majority of studies assessing the contribution of pathogenic germline variants (PGVs) to cancer predisposition have focused on patients with single cancers. We analyzed 45 known cancer predisposition genes (CPGs) in germline samples of 202 patients with hematological malignancies (HMs) plus one or more other independent cancer managed at major tertiary medical centers on two different continents. This included 120 patients with therapy-related myeloid neoplasms (t-MNs), where the HM occurred after cytotoxic treatment for a first malignancy, and 82 patients with multiple cancers in which the HM was not preceded by cytotoxic therapy (MC-HM). Using American College of Medical Genetics/Association for Molecular Pathology variant classification guidelines, 13% of patients had PGVs, most frequently identified in CHEK2 (17% of PGVs), BRCA1 (13%), DDX41 (13%), and TP53 (7%). The frequency of PGVs in MC-HM was higher than in t-MN, although not statistically significant (18 vs. 9%; p = 0.085). The frequency of PGVs in lymphoid and myeloid HM patients was similar (19 vs. 17.5%; p > 0.9). Critically, patients with PGVs in BRCA1, BRCA2 or TP53 did not satisfy current clinical phenotypic criteria for germline testing. Our data suggest that a personal history of multiple cancers, one being a HM, should trigger screening for PGVs.

Role of gene therapy in Fanconi anemia: A systematic and literature review with future directions

Gene therapy (GT) has been reported to improve bone marrow function in individuals with Fanconi anemia (FA); however, its clinical application is still in the initial stages. We conducted this systematic review, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, to assess the long-term safety and clinical outcomes of GT in FA patients. Electronic searches from PubMed, Web of Science, Cochrane Library, and Google Scholar were conducted and full texts of articles meeting our inclusion criteria were reviewed. Three clinical trials were included, with a total of nine patients and mean age of 10.7 ± 5.7 years. All patients had lentiviral-mediated GT. A 1-year follow-up showed stabilization in blood lineages, without any serious adverse effects from GT. A metaregression analysis could not be conducted, as very little long-term follow-up data of patients was observed, and the median survival rate could not be calculated. Thus, we can conclude that GT seems to be a safe procedure in FA; however, further research needs to be conducted on the longitudinal clinical effects of GT in FA, for a better insight into its potential to become a standard form of treatment.

MYC Promotes Bone Marrow Stem Cell Dysfunction in Fanconi Anemia

Bone marrow failure (BMF) in Fanconi anemia (FA) patients results from dysfunctional hematopoietic stem and progenitor cells (HSPCs). To identify determinants of BMF, we performed single-cell transcriptome profiling of primary HSPCs from FA patients. In addition to overexpression of p53 and TGF-β pathway genes, we identified high levels of MYC expression. We correspondingly observed coexistence of distinct HSPC subpopulations expressing high levels of TP53 or MYC in FA bone marrow (BM). Inhibiting MYC expression with the BET bromodomain inhibitor (+)-JQ1 reduced the clonogenic potential of FA patient HSPCs but rescued physiological and genotoxic stress in HSPCs from FA mice, showing that MYC promotes proliferation while increasing DNA damage. MYC-high HSPCs showed significant downregulation of cell adhesion genes, consistent with enhanced egress of FA HSPCs from bone marrow to peripheral blood. We speculate that MYC overexpression impairs HSPC function in FA patients and contributes to exhaustion in FA bone marrow.

Envelope-Specific Adaptive Immunity following Transplantation of Hematopoietic Stem Cells Modified with VSV-G Lentivirus

Current approaches for hematopoietic stem cell gene therapy typically involve lentiviral gene transfer in tandem with a conditioning regimen to aid stem cell engraftment. Although many pseudotyped envelopes have the capacity to be immunogenic due to their viral origins, thus far immune responses against the most common envelope, vesicular stomatitis virus glycoprotein G (VSV-G), have not been reported in hematopoietic stem cell gene therapy trials. Herein, we report on two Fanconi anemia patients who underwent autologous transplantation of a lineage-depleted, gene-modified hematopoietic stem cell product without conditioning. We observed the induction of robust VSV-G-specific immunity, consistent with low/undetectable gene marking in both patients. Upon further interrogation, adaptive immune mechanisms directed against VSV-G were detected following transplantation in both patients, including increased VSV-G-specific T cell responses, anti-VSV-G immunoglobulin G (IgG), and cytotoxic responses that can specifically kill VSV-G-expressing target cell lines. A proportion of healthy controls also displayed preexisting VSV-G-specific CD4+ and CD8+ T cell responses, as well as VSV-G-specific IgG. Taken together, these data show that VSV-G-pseudotyped lentiviral vectors have the ability to elicit interfering adaptive immune responses in the context of certain hematopoietic stem cell transplantation settings.

Special pre- and posttransplant considerations in inherited bone marrow failure and hematopoietic malignancy predisposition syndromes

Advances in the diagnosis and treatment of inherited bone marrow failure syndromes (IBMFS) have provided insight into the complexity of these diseases. The diseases are heterogeneous and characterized by developmental abnormalities, progressive marrow failure, and predisposition to cancer. A correct diagnosis allows for appropriate treatment, genetic counseling, and cancer surveillance. The common IBMFSs are Fanconi anemia, dyskeratosis congenita, and Diamond-Blackfan anemia. Hematopoietic cell transplantation (HCT) offers curative treatment of the hematologic complications of IBMFS. Because of the systemic nature of these diseases, transplant strategies are modified to decrease immediate and late toxicities. HCT from HLA-matched related or unrelated donors offers excellent survival for young patients in aplasia. Challenges include the treatment of adults with marrow aplasia, presentation with myeloid malignancy regardless of age, and early detection or treatment of cancer. In this article, I will describe our approach and evaluation of patients transplanted with IBMFS and review most frequent complications before and after transplant.

Hematopoietic Stem Cell Transplantation for Fanconi Anemia: A Single Center Experience from India

Hematopoietic stem cell transplantation (HSCT) is the only treatment option for the hematological manifestations of Fanconi anemia (FA). Fludarabine based reduced intensity conditioning regimens have helped in improving outcomes significantly in FA patients. We retrospectively analyzed the outcomes of FA patients who underwent allogeneic HSCT at BLK Superspeciality Hospital, New Delhi from June 2011 to September 2019. Twenty FA patients underwent 23 transplants at our center. Overall survival and disease free survival were 65% and 50%, respectively at a median of 23 months. Overall mortality was 30%. HSCT for FA is a feasible option even in developing countries although children present late to transplant centers after multiple transfusions and infections.

Outcome of patients with Fanconi anemia developing myelodysplasia and acute leukemia who received allogeneic hematopoietic stem cell transplantation: A retrospective analysis on behalf of EBMT group

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is curative for bone marrow failure in patients with Fanconi anemia (FA), but the presence of a malignant transformation is associated with a poor prognosis and the management of these patients is still challenging. We analyzed outcome of 74 FA patients with a diagnosis of myelodysplastic syndrome (n = 35), acute leukemia (n = 35) or with cytogenetic abnormalities (n = 4), who underwent allo-HSCT from 1999 to 2016 in EBMT network. Type of diagnosis, pre-HSCT cytoreductive therapies and related toxicities, disease status pre-HSCT, donor type, and conditioning regimen were considered as main variables potentially influencing outcome. The 5-year OS and EFS were 42% (30-53%) and 39% (27-51%), respectively. Patients transplanted in CR showed better OS compared with those transplanted in presence of an active malignant disease (OS:71%[48-95] vs 37% [24-50],P = .04), while none of the other variables considered had an impact. Twenty-two patients received pre-HSCT cytoreduction and 9/22 showed a grade 3-4 toxicity, without any lethal event or negative influence on survival after HSCT(OS:toxicity pre-HSCT 48% [20-75%] vs no-toxicity 51% [25-78%],P = .98). The cumulative incidence of day-100 grade II-IV a-GvHD and of 5-year c-GvHD were 38% (26-50%) and 40% (28-52%). Non-relapse-related mortality and incidence of relapse at 5-years were 40% (29-52%) and 21% (11-30%) respectively, without any significant impact of the tested variables. Causes of death were transplant-related events in most patients (34 out of the 42 deaths, 81%). This analysis confirms the poor outcome of transformed FA patients and identifies the importance of achieving CR pre-HSCT, suggesting that, in a newly diagnosed transformed FA patient, a cytoreductive approach pre-HSCT should be considered if a donor have been secured.

Treosulfan-Based Conditioning Regimen in Haematopoietic Stem Cell Transplantation with TCRαβ/CD19 Depletion in Nijmegen Breakage Syndrome

Nijmegen breakage syndrome (NBS) is a DNA repair disorder characterized by combined immunodeficiency and a high predisposition to malignancies. HSCT appears to cure immunodeficiency, but remains challenging due to limited experience in long-term risks of transplant-associated toxicity and malignancies. Twenty NBS patients received 22 allogeneic HSCTs with TCRαβ/CD19+ graft depletion with fludarabine 150 mg/m², cyclophosphamide 20-40 mg/kg and thymoglobulin 5 mg/kg based conditioning regimens (CRs). Twelve patients additionally received low-dose busulfan 4 mg/kg (Bu group) and 10 patients (including 2 recipients of a second HSCT) treosulfan (Treo group) 30 g/m². Overall and event-free survival were 0.75 vs 1 (p = 0.16) and 0.47 vs 0.89 (p = 0.1) in the Bu and Treo groups, respectively. In the Bu group, four patients developed graft rejection, and three died: two died of de novo and relapsed lymphomas and one died of adenoviral hepatitis. The four living patients exhibited split chimerism with predominantly recipient myeloid cells and predominantly donor T and B lymphocytes. In Treo group, one patient developed rhabdomyosarcoma. There was no difference in the incidence of GVHD, viral reactivation, or early toxicity between either group. Low-dose Bu-containing CR in NBS leads to increased graft failure and low donor myeloid chimerism. Treo-CR followed by TCRαβ/CD19-depleted HSCT demonstrates a low level of early transplant-associated toxicity and enhanced graft function with stable donor chimerism.

Orthodontic intervention in Fanconi's anemia: A case report

The objective of this case report was to present the orthodontic treatment of an 8-year-old female patient with Fanconi's anemia and Class III skeletal pattern and agenesis of maxillary lateral incisors. Patient presented in the late mixed dentition with a Class III malocclusion with anterior and posterior crossbites. Rapid maxillary expansion and facemask therapy was performed for 12 months. Phase II was simplified with a 6 × 2 fixed appliance only in the mandibular arch for solving the anterior crowding. Maxillary canines were reshaped as lateral incisors and the central incisors were augmented for closing spaces. Although the systemic disease, orthodontic intervention is possible if individual limitations are considered and treatment is simplified.

Effective Multi-lineage Engraftment in a Mouse Model of Fanconi Anemia Using Non-genotoxic Antibody-Based Conditioning

Conditioning chemotherapy is used to deplete hematopoietic stem cells in the recipient’s marrow, facilitating donor cell engraftment. Although effective, a major issue with chemotherapy is the systemic genotoxicity that increases the risk for secondary malignancies. Antibody conjugates targeting hematopoietic cells are an emerging non-genotoxic method of opening the marrow niche and promoting engraftment of transplanted cells while maintaining intact marrow cellularity. Specifically, this platform would be useful in diseases associated with DNA damage or cancer predisposition, such as dyskeratosis congenita, Schwachman-Diamond syndrome, and Fanconi anemia (FA). Our approach utilizes antibody-drug conjugates (ADC) as an alternative conditioning regimen in an FA mouse model of autologous transplantation. Antibodies targeting either CD45 or CD117 were conjugated to saporin (SAP), a ribosomal toxin. FANCA knockout mice were conditioned with either CD45-SAP or CD117-SAP prior to receiving whole marrow from a heterozygous healthy donor. Bone marrow and peripheral blood analysis revealed equivalent levels of donor engraftment, with minimal toxicity in ADC-treated groups as compared with cyclophosphamide-treated controls. Our findings suggest ADCs may be an effective conditioning strategy in stem cell transplantation not only for diseases where traditional chemotherapy is not tolerated, but also more broadly for the field of blood and marrow transplantation.

Genetic predisposition to MDS: diagnosis and management

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by clonal hematopoiesis with a propensity to evolve into acute myeloid leukemia. MDS presenting in children and young adults is associated with features clinically and biologically distinct from MDS arising in older adults. MDS presenting in children and young adults is associated with a higher likelihood of an underlying genetic predisposition; however, genetic predisposition is increasingly recognized in a subset of older adults. The diagnosis of a genetic predisposition to MDS informs clinical care and treatment selection. Early diagnosis allows a tailored approach to management and surveillance. Genetic testing now offers a powerful diagnostic approach but also poses new challenges and caveats. Clinical expertise in these disorders together with scientific expertise regarding the affected genes is essential for diagnosis. Understanding the basic mechanisms of genetic predisposition to myeloid malignancies may inform surveillance strategies and lead to novel therapies. The cases presented in this article illustrate challenges to the diagnosis of germline genetic predisposition to MDS and how the diagnosis affects clinical management and treatment.

Infection profile in children and adolescents with bone marrow failures treated with allogeneic hematopoietic stem cell transplantation

BACKGROUND

The objective of the study was to analyze the profile of infections in children with BMF following alloHCT.

METHODS

Data of 169 consecutive children with inherited and acquired BMF treated with alloHCT between 2012 and 2017 in Polish pediatric transplant departments were analyzed in registry-based retrospective study, with respect to the type of infection, and clinical outcome.

RESULTS

At least 1 infection was diagnosed in 107/169 patients (60.4%). In total, 182 infections were diagnosed. The most common were VI (96; 52.7%), followed by BI (71; 39.0%), and FI (15; 8.2%), P < .001. The most common etiological factors of VI were as follows: CMV (38.5%), EBV (22.9%), and BK virus (24%); while of BI were as follows: Staphylococcus spp. (17; 23.9%), Enterococcus faecium (10; 14.1%), and Klebsiella pneumoniae (9; 12.7%). No difference was found between the occurrence of infections with respect to donor type, graft source, and conditioning type. GvHD had no impact on the incidence of VI, BI, and FI. Fifteen FI were diagnosed in 12 patients, of which 14 FI were diagnosed in children transplanted for FA. Of total 107 children, 9 died (8.4%), of which 4 (3.7%) due to infections: bacterial sepsis (2) and invasive FI (2).

CONCLUSION

Infections in children with BMF following alloHCT remain an important cause of morbidity. Children with FA had high incidence of FI. In our analysis, aGvHD had no impact on the occurrence on infections, although the study was not strong enough to prove such a difference.

NHEJ-Mediated Repair of CRISPR-Cas9-Induced DNA Breaks Efficiently Corrects Mutations in HSPCs from Patients with Fanconi Anemia

Non-homologous end-joining (NHEJ) is the preferred mechanism used by hematopoietic stem cells (HSCs) to repair double-stranded DNA breaks and is particularly increased in cells deficient in the Fanconi anemia (FA) pathway. Here, we show feasible correction of compromised functional phenotypes in hematopoietic cells from multiple FA complementation groups, including FA-A, FA-C, FA-D1, and FA-D2. NHEJ-mediated repair of targeted CRISPR-Cas9-induced DNA breaks generated compensatory insertions and deletions that restore the coding frame of the mutated gene. NHEJ-mediated editing efficacy was initially verified in FA lymphoblastic cell lines and then in primary FA patient-derived CD34⁺ cells, which showed marked proliferative advantage and phenotypic correction both in vitro and after transplantation. Importantly, and in contrast to homologous directed repair, NHEJ efficiently targeted primitive human HSCs, indicating that NHEJ editing approaches may constitute a sound alternative for editing self-renewing human HSCs and consequently for treatment of FA and other monogenic diseases affecting the hematopoietic system.