CRISPR/Cas9-Mediated in vivo Genetic Correction in a Mouse Model of Hemophilia A

AAV mediated genome engineering with a bypass coagulation factor alleviates the bleeding phenotype in a murine model of hemophilia B

It is crucial to develop a long-term therapy that targets hemophilia A and B, including inhibitor-positive patients. We have developed an Adeno-associated virus (AAV) based strategy to integrate the bypass coagulation factor, activated FVII (murine, mFVIIa) gene into the Rosa26 locus using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 mediated gene-editing. AAV vectors designed for expression of guide RNA (AAV8-gRNA), Cas9 (AAV2 neddylation mutant-Cas9), and mFVIIa (AAV8-mFVIIa) flanked by homology arms of the target locus were validated in vitro. Hemophilia B mice were administered with AAV carrying gRNA, Cas9 (1 × 1011 vgs/mouse), and mFVIIa with homology arms (2 × 1011 vgs/mouse) with appropriate controls. Functional rescue was documented with suitable coagulation assays at various time points. The data from the T7 endonuclease assay revealed a cleavage efficiency of 20-42 %. Further, DNA sequencing confirmed the targeted integration of mFVIIa into the safe-harbor Rosa26 locus. The prothrombin time (PT) assay revealed a significant reduction in PT in mice that received the gene-editing vectors (22 %), and a 13 % decline in mice that received only the AAV-FVIIa when compared to mock treated mice, 8 weeks after vector administration. Furthermore, FVIIa activity in mice that received triple gene-editing vectors was higher (122.5mIU/mL vs 28.8mIU/mL) than the mock group up to 15 weeks post vector administration. A hemostatic challenge by tail clip assay revealed that hemophilia B mice injected with only FVIIa or the gene-editing vectors had significant reduction in blood loss. In conclusion, AAV based gene-editing facilitates sustained expression of coagulation FVIIa and phenotypic rescue in hemophilia B mice.

CRISPR-Cas9 system: a novel and promising era of genotherapy for beta-hemoglobinopathies, hematological malignancy, and hemophilia

Gene therapy represents a significant potential to revolutionize the field of hematology with applications in correcting genetic mutations, generating cell lines and animal models, and improving the feasibility and efficacy of cancer immunotherapy. Compared to different genetic engineering tools, clustered regularly interspaced short palindromic repeats (CRISPR) CRISPR-associated protein 9 (Cas9) emerged as an effective and versatile genetic editor with the ability to precisely modify the genome. The applications of genetic engineering in various hematological disorders have shown encouraging results. Monogenic hematological disorders can conceivably be corrected with single gene modification. Through the use of CRISPR-CAS9, restoration of functional red blood cells and hemostasis factors were successfully attained in sickle cell anemia, beta-thalassemia, and hemophilia disorders. Our understanding of hemato-oncology has been advanced via CRIPSR-CAS9 technology. CRISPR-CAS9 aided to build a platform of mutated genes responsible for cell survival and proliferation in leukemia. Therapeutic application of CRISPR-CAS9 when combined with chimeric antigen receptor (CAR) T cell therapy in multiple myeloma and acute lymphoblastic leukemia was feasible with attenuation of CAR T cell therapy pitfalls. Our review outlines the latest literature on the utilization of CRISPR-Cas9 in the treatment of beta-hemoglobinopathies and hemophilia disorders. We present the strategies that were employed and the findings of preclinical and clinical trials. Also, the review will discuss gene engineering in the field of hemato-oncology as a proper tool to facilitate and overcome the drawbacks of chimeric antigen receptor T cell therapy (CAR-T).

Gene Therapy in Hemophilia A: Achievements, Challenges, and Perspectives

Strides in advancements of care of persons with hemophilia include development of long-acting factor replacement therapies, novel substitution and hemostatic rebalancing agents, and most recently approved gene therapy. Several decades of preclinical and clinical trials have led to development of adeno-associated viral (AAV) vector-mediated gene transfer for endogenous production of factor VIII (FVIII) in hemophilia A (HA). Only one gene therapy product for HA (valoctocogene roxaparvovec) has been approved by regulatory authorities. Results of valoctocogene roxaparvovec trial show significant improvement in bleeding rates and use of factor replacement therapy; however, sustainability and duration of response show variability with overall decline in FVIII expression over time. Further challenges include untoward adverse effects involving liver toxicity requiring immunosuppression and development of neutralizing antibodies to AAV vector rendering future doses ineffective. Real-life applicability of gene therapy for HA will require appropriate patient screening, infrastructure setup, long-term monitoring including data collection of patient-reported outcomes and innovative payment schemes. This review article highlights the success and development of HA gene therapy trials, challenges including adverse outcomes and variability of response, and perspectives on approach to gene therapy including shared decision-making and need for future strategies to overcome the several unmet needs.

Old age as a risk factor for liver diseases: Modern therapeutic approaches

Recent scientific interest has been directed towards age-related diseases, driven by the significant increase in global life expectancy and the growing population of individuals aged 65 and above. The ageing process encompasses various biological, physiological, environmental, psychological, behavioural, and social changes, leading to an augmented susceptibility to chronic illnesses. Cardiovascular, neurological, musculoskeletal, liver and oncological diseases are prevalent in the elderly. Moreover, ageing individuals demonstrate reduced regenerative capacity and decreased tolerance towards therapeutic interventions, including organ transplantation. Liver diseases, such as non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis, fibrosis, and cirrhosis, have emerged as significant public health concerns. Paradoxically, these conditions remain underestimated despite their substantial global impact. Age-related factors are closely associated with the severity and unfavorable prognosis of various liver diseases, warranting further investigation to enhance clinical management and develop novel therapeutic strategies. This comprehensive review focuses specifically on age-related liver diseases, their treatment strategies, and contemporary practices. It provides a detailed account of the global burden, types, molecular mechanisms, and epigenetic alterations underlying these liver pathologies.

Innovations in RNA therapy for hemophilia

Given the shortcomings of current factor-, nonfactor-, and adeno-associated virus gene-based therapies, the recent advent of RNA-based therapeutics for hemophilia is changing the fundamental approach to hemophilia management. From small interfering RNA therapeutics that knockdown clot regulators antithrombin, protein S, and heparin cofactor II, to CRISPR/Cas9 gene editing that may personalize treatment, improved technologies have the potential to reduce bleeds and factor use and avoid inhibitor formation. These novel agents, some in preclinical studies and others in early phase trials, have the potential to simplify treatment and improve hemostasis and quality of life. Furthermore, because these therapies arise from manipulation of the coagulation cascade and thrombin generation and its regulation, they will enhance our understanding of hemostasis and thrombosis and ultimately lead to better therapies for children and adults with inherited bleeding disorders. What does the future hold? With the development of novel preclinical technologies at the bench, there will be fewer joint bleeds, debilitating joint disease, orthopedic surgery, and improved physical and mental health, which were not previously possible. In this review, we identify current limitations of treatment and progress in the development of novel RNA therapeutics, including messenger RNA nanoparticle delivery and gene editing for the treatment of hemophilia.

Treatment of congenital coagulopathies, from biologic to biotechnological drugs: The relevance of gene editing (CRISPR/Cas)

Congenital coagulopathies have, throughout the history of medicine, been a focus of scientific study and of great interest as they constitute an alteration of one of the most important and conserved pathways of evolution. The first therapeutic strategies developed to address them were aimed at restoring the blood components lost during hemorrhage by administering whole blood or plasma. Later on, the use of cryoprecipitates was a significant breakthrough as it made it possible to decrease the volumes of blood infused. In the 1970' and 80', clotting factor concentrates became the treatment and, from the 1990's to the present day, recombinant factors -with increasingly longer half-lives- have taken over as the treatment of choice for certain coagulopathies in a seamless yet momentous transition from biological to biotechnological drugs. The beginning of this century, however, saw the emergence of new advanced (gene and cell) treatments, which are currently transforming the therapeutic landscape. The possibility to use cells and viruses as well as specific or bispecific antibodies as medicines is likely to spark a revolution in the world of pharmacology where therapies will be individualized and have long-term effects. Specifically, attention is nowadays focused on the development of gene editing strategies, chiefly those based on CRISPR/Cas technology. Rare coagulopathies such as hemophilia A and B, or even ultra-rare ones such as factor V deficiency, could be among those deriving the greatest benefit from these new developments.

Immunogenicity of Therapeutic Biological Modalities - Lessons from Hemophilia A Therapies

The introduction and development of biologics such as therapeutic proteins, gene-, and cell-based therapy have revolutionized the scope of treatment for many diseases. However, a significant portion of the patients develop unwanted immune reactions against these novel biological modalities, referred to as immunogenicity, and no longer benefit from the treatments. In the current review, using Hemophilia A (HA) therapy as an example, we will discuss the immunogenicity issue of multiple biological modalities. Currently, the number of therapeutic modalities that are approved or recently explored to treat HA, a hereditary bleeding disorder, is increasing rapidly. These include, but are not limited to, recombinant factor VIII proteins, PEGylated FVIII, FVIII Fc fusion protein, bispecific monoclonal antibodies, gene replacement therapy, gene editing therapy, and cell-based therapy. They offer the patients a broader range of more advanced and effective treatment options, yet immunogenicity remains the most critical complication in the management of this disorder. Recent advances in strategies to manage and mitigate immunogenicity will also be reviewed.

Hemophilia Gene Therapy: The End of the Beginning?

Extensive preclinical research over the past 30 years has culminated in the recent regulatory approval of several gene therapy products for hemophilia. Based on the efficacy and safety data in a recently conducted phase III clinical trial, Roctavian® (valoctocogene roxaparvovec), an adeno-associated viral (AAV5) vector expressing a B domain deleted factor VIII (FVIII) complementary DNA, was approved by the European Commission and Food and Drug Administration (FDA) for the treatment of patients with severe hemophilia A. In addition, Hemgenix® (etranacogene dezaparvovec) was also recently approved by the European Medicines Agency and the FDA for the treatment of patients with severe hemophilia B. This product is based on an AAV5 vector expressing a hyper-active factor IX (FIX) transgene (FIX-Padua) transgene. All AAV-based phase III clinical trials to date show a significant increase in FVIII or FIX levels in the majority of treated patients, consistent with a substantial decrease in bleeding episodes and a concomitant reduction in factor usage obviating the need for factor prophylaxis in most patients. However, significant interpatient variability remains that is not fully understood. Moreover, most patients encountered short-term asymptomatic liver inflammation that was treated by immune suppression with corticosteroids or other immune suppressants. In all phase III trials to date, FIX expression has appeared relatively more stable than FVIII, though individual patients also had prolonged FVIII expression. Whether lifelong expression of clotting factors can be realized after gene therapy requires longer follow-up studies. Further preclinical development of next-generation gene editing technologies offers new prospects for the development of a sustained cure for hemophilia, not only in adults, but ultimately in children with hemophilia too.

Correction of F8 intron 1 inversion in hemophilia A patient-specific iPSCs by CRISPR/Cas9 mediated gene editing

Introduction: Hemophilia A (HA) is the most common genetic bleeding disorder caused by mutations in the F8 gene encoding coagulation factor VIII (FVIII). As the second predominant pathogenic mutation in hemophilia A severe patients, F8 Intron one inversion (Inv1) completely splits the F8 gene into two parts and disrupts the F8 transcription, resulting in no FVIII protein production. The part which contains exon 2-exon 26 covers 98% of F8 coding region.

Methods: We hypothesized that in situ genetic manipulation of F8 to add a promoter and exon one before the exon two could restore the F8 expression. The donor plasmid included human alpha 1-antitrypsin (hAAT) promoter, exon one and splicing donor site (SD) based on homology-mediated end joining (HMEJ) strategy was targeted addition in hemophilia A patient-derived induced pluripotent stem cell (HA-iPSCs) using CRISPR/Cas9. The iPSCs were differentiated into hepatocyte-like cells (HPLCs).

Results: The hAAT promoter and exon one were targeted addition in HA-iPSCs with a high efficiency of 10.19% via HMEJ. The FVIII expression, secretion, and activity were detected in HPLCs derived from gene-targeted iPSCs.

Discussion: Thus, we firstly rescued the 140 kb reversion mutation by gene addition of a 975 bp fragment in the HA-iPSCs with Inv1 mutation, providing a promising gene correction strategy for genetic disease with large sequence variants.

Progress in and Prospects of Genome Editing Tools for Human Disease Model Development and Therapeutic Applications

Programmable nucleases, such as zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas, are widely accepted because of their diversity and enormous potential for targeted genomic modifications in eukaryotes and other animals. Moreover, rapid advances in genome editing tools have accelerated the ability to produce various genetically modified animal models for studying human diseases. Given the advances in gene editing tools, these animal models are gradually evolving toward mimicking human diseases through the introduction of human pathogenic mutations in their genome rather than the conventional gene knockout. In the present review, we summarize the current progress in and discuss the prospects for developing mouse models of human diseases and their therapeutic applications based on advances in the study of programmable nucleases.

Characteristics of BAY 2599023 in the Current Treatment Landscape of Hemophilia A Gene Therapy

Hemophilia A, a single gene disorder leading to deficient Factor VIII (FVIII), is a suitable candidate for gene therapy. The aspiration is for single administration of a genetic therapy that would allow the production of endogenous FVIII sufficient to restore hemostasis and other biological processes. This would potentially result in reliable protection from bleeding and its associated physical and emotional impacts. Gene therapy offers the possibility of a clinically relevant improvement in disease phenotype and transformational improvement in quality of life, including an opportunity to engage in physical activities more confidently. Gene therapy products for hemophilia A in advanced clinical development use adeno-associated viral (AAV) vectors and a codon-optimized B-domain deleted FVIII transgene. However, the different AAV-based gene therapies have distinct design features, such as choice of vector capsid, enhancer and promoter regions, FVIII transgene sequence and manufacturing processes. These, in turn, impact patient eligibility, safety and efficacy. Ideally, gene therapy technology for hemophilia A should offer bleed protection, durable FVIII expression, broad eligibility and limited response variability between patients, and long-term safety. However, several limitations and challenges must be overcome. Here, we introduce the characteristics of the BAY 2599023 (AAVhu37.hFVIIIco, DTX 201) gene therapy product, including the low prevalence in the general population of anti-AAV-hu37 antibodies, as well as other gene therapy AAV products and approaches. We will examine how these can potentially meet the challenges of gene therapy, with the ultimate aim of improving the lives of patients with hemophilia A.

Application of Gene Therapy in Hemophilia

Gene therapy refers to introducing normal exogenous genes into target cells to correct or compensate for the diseases caused by defective and abnormal genes for the purpose of therapy. It holds out hope of a cure for single-gene genetic diseases such as thalassemia, hemophilia, etc. At present, gene therapy is performed in two ways: introducing exogenous genes, and gene editing. A great number of clinical trials of gene therapy in hemophilia have been carried out using viral vectors to introduce foreign genes into target cells. However, the production of neutralizing antibodies following injection and the inability to prepare viral vectors in large quantities limit their application. Although gene-editing methods like CRISPR avoid the above problems, the potential risks of off-target effects are still unknown. More trials and evidence are needed to elucidate the safety and accuracy of gene therapy. This paper will review the bench and clinical work of gene therapy in hemophilia in recent years, and summarize the challenges and prospects of gene therapy, so as to provide directions for future scientific research in this field.