Improved collection of hematopoietic stem cells and progenitors from Fanconi anemia patients for gene therapy purposes

Lentivirus-mediated gene therapy corrects ribosomal biogenesis and shows promise for Diamond Blackfan anemia

This study lays the groundwork for future lentivirus-mediated gene therapy in patients with Diamond Blackfan anemia (DBA) caused by mutations in ribosomal protein S19 (RPS19), showing evidence of a new safe and effective therapy. The data show that, unlike patients with Fanconi anemia (FA), the hematopoietic stem cell (HSC) reservoir of patients with DBA was not significantly reduced, suggesting that collection of these cells should not constitute a remarkable restriction for DBA gene therapy. Subsequently, 2 clinically applicable lentiviral vectors were developed. In the former lentiviral vector, PGK.CoRPS19 LV, a codon-optimized version of RPS19 was driven by the phosphoglycerate kinase promoter (PGK) already used in different gene therapy trials, including FA gene therapy. In the latter one, EF1α.CoRPS19 LV, RPS19 expression was driven by the elongation factor alpha short promoter, EF1α(s). Preclinical experiments showed that transduction of DBA patient CD34+ cells with the PGK.CoRPS19 LV restored erythroid differentiation, and demonstrated the long-term repopulating properties of corrected DBA CD34+ cells, providing evidence of improved erythroid maturation. Concomitantly, long-term restoration of ribosomal biogenesis was verified using a potentially novel method applicable to patients' blood cells, based on ribosomal RNA methylation analyses. Finally, in vivo safety studies and proviral insertion site analyses showed that lentivirus-mediated gene therapy was nontoxic.

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.

Beyond current treatment of Fanconi Anemia: What do advances in cell and gene-based approaches offer?

Fanconi anemia (FA) is a rare inherited disorder that mainly affects the bone marrow. This condition causes decreased production of all types of blood cells. FA is caused by a defective repair of DNA interstrand crosslinks and to date, mutations in over 20 genes have been linked to the disease. Advances in science and molecular biology have provided new insight between FA gene mutations and the severity of clinical manifestations. Here, we will highlight the current and promising therapeutic options for this rare disease. The current standard treatment for FA patients is hematopoietic stem cell transplantation, a treatment associated to exposure to radiation or chemotherapy, immunological complications, plus opportunistic infections from prolonged immune incompetence or increased risk of morbidity. New arising treatments include gene addition therapy, genome editing using CRISPR-Cas9 nuclease, and hematopoietic stem cell generation from induced pluripotent stem cells. Finally, we will also discuss the revolutionary developments in mRNA therapeutics as an opportunity for this disease.

Editing human hematopoietic stem cells: advances and challenges

Genome editing of hematopoietic stem and progenitor cells is being developed for the treatment of several inherited disorders of the hematopoietic system. The adaptation of CRISPR-Cas9-based technologies to make precise changes to the genome, and developments in altering the specificity and efficiency, and improving the delivery of nucleases to target cells have led to several breakthroughs. Many clinical trials are ongoing, and several pre-clinical models have been reported that would allow these genetic therapies to one day offer a potential cure to patients with diseases where limited options currently exist. However, there remain several challenges with respect to establishing safety, expanding accessibility and improving the manufacturing processes of these therapeutic products. This review focuses on some of the recent advances in the field of genome editing of hematopoietic stem and progenitor cells and illustrates the ongoing challenges.

The chemokines CXCL8 and CXCL12: molecular and functional properties, role in disease and efforts towards pharmacological intervention

Chemokines are an indispensable component of our immune system through the regulation of directional migration and activation of leukocytes. CXCL8 is the most potent human neutrophil-attracting chemokine and plays crucial roles in the response to infection and tissue injury. CXCL8 activity inherently depends on interaction with the human CXC chemokine receptors CXCR1 and CXCR2, the atypical chemokine receptor ACKR1, and glycosaminoglycans. Furthermore, (hetero)dimerization and tight regulation of transcription and translation, as well as post-translational modifications further fine-tune the spatial and temporal activity of CXCL8 in the context of inflammatory diseases and cancer. The CXCL8 interaction with receptors and glycosaminoglycans is therefore a promising target for therapy, as illustrated by multiple ongoing clinical trials. CXCL8-mediated neutrophil mobilization to blood is directly opposed by CXCL12, which retains leukocytes in bone marrow. CXCL12 is primarily a homeostatic chemokine that induces migration and activation of hematopoietic progenitor cells, endothelial cells, and several leukocytes through interaction with CXCR4, ACKR1, and ACKR3. Thereby, it is an essential player in the regulation of embryogenesis, hematopoiesis, and angiogenesis. However, CXCL12 can also exert inflammatory functions, as illustrated by its pivotal role in a growing list of pathologies and its synergy with CXCL8 and other chemokines to induce leukocyte chemotaxis. Here, we review the plethora of information on the CXCL8 structure, interaction with receptors and glycosaminoglycans, different levels of activity regulation, role in homeostasis and disease, and therapeutic prospects. Finally, we discuss recent research on CXCL12 biochemistry and biology and its role in pathology and pharmacology.

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.

Adenine base editing efficiently restores the function of Fanconi anemia hematopoietic stem and progenitor cells

Fanconi Anemia (FA) is a debilitating genetic disorder with a wide range of severe symptoms including bone marrow failure and predisposition to cancer. CRISPR-Cas genome editing manipulates genotypes by harnessing DNA repair and has been proposed as a potential cure for FA. But FA is caused by deficiencies in DNA repair itself, preventing the use of editing strategies such as homology directed repair. Recently developed base editing (BE) systems do not rely on double stranded DNA breaks and might be used to target mutations in FA genes, but this remains to be tested. Here we develop a proof of concept therapeutic base editing strategy to address two of the most prevalent FANCA mutations in patient hematopoietic stem and progenitor cells. We find that optimizing adenine base editor construct, vector type, guide RNA format, and delivery conditions leads to very effective genetic modification in multiple FA patient backgrounds. Optimized base editing restored FANCA expression, molecular function of the FA pathway, and phenotypic resistance to crosslinking agents. ABE8e mediated editing in primary hematopoietic stem and progenitor cells from FA patients was both genotypically effective and restored FA pathway function, indicating the potential of base editing strategies for future clinical application in FA.