A Molecular Revolution in the Treatment of Hemophilia

DNA base editing corrects common hemophilia A mutations and restores factor VIII expression in in vitro and ex vivo models

BACKGROUND

Replacement and nonreplacement therapies effectively control bleeding in hemophilia A (HA) but imply lifelong interventions. Authorized gene addition therapy could provide a cure but still poses questions on durability. FVIIIgene correction would definitively restore factor (F)VIII production, as shown in animal models through nuclease-mediated homologous recombination (HR). However, low efficiency and potential off-target double-strand break still limit HR translatability.

OBJECTIVES

To correct common model single point mutations leading to severe HA through the recently developed double-strand break/HR-independent base editing (BE) and prime editing (PE) approaches.

METHODS

Screening for efficacy of BE/PE systems in HEK293T cells transiently expressing FVIII variants and validation at DNA (sequencing) and protein (enzyme-linked immunosorbent assay; activated partial thromboplastin time) level in stable clones. Evaluation of rescue in engineered blood outgrowth endothelial cells by lentiviral-mediated delivery of BE.

RESULTS

Transient assays identified the best-performing BE/PE systems for each variant, with the highest rescue of FVIII expression (up to 25% of wild-type recombinant FVIII) for the p.R2166∗ and p.R2228Q mutations. In stable clones, we demonstrated that the mutation reversion on DNA (∼24%) was consistent with the rescue of FVIII secretion and activity of 20% to 30%. The lentiviral-mediated delivery of the selected BE systems was attempted in engineered blood outgrowth endothelial cells harboring the p.R2166∗ and p.R2228Q variants, which led to an appreciable and dose-dependent rescue of secreted functional FVIII.

CONCLUSION

Overall data provide the first proof-of-concept for effective BE/PE-mediated correction of HA-causing mutations, which encourage studies in mouse models to develop a personalized cure for large cohorts of patients through a single intervention.

Deciphering conundrums of adeno-associated virus liver-directed gene therapy: focus on hemophilia

Adeno-associated virus gene therapy has been the subject of intensive investigation for monogenic disease gene addition therapy for more than 25 years, yet few therapies have been approved by regulatory agencies. Most have not progressed beyond phase 1/2 due to toxicity, lack of efficacy, or both. The liver is a natural target for adeno-associated virus since most serotypes have a high degree of tropism for hepatocytes due to cell surface receptors for the virus and the unique liver sinusoidal geometry facilitating high volumes of blood contact with hepatocyte cell surfaces. Recessive monogenic diseases such as hemophilia represent promising targets since the defective proteins are often synthesized in the liver and secreted into the circulation, making them easy to measure, and many do not require precise regulation. Yet, despite initiation of many disease-specific clinical trials, therapeutic windows are often nonexistent, resulting in excess toxicity and insufficient efficacy. Iterative progress built on these attempts is best illustrated by hemophilia, with the first regulatory approvals for factor IX and factor VIII gene therapies eventually achieved 25 years after the first gene therapy studies in humans. Although successful gene transfer may result in the production of sufficient transgenic protein to modify the disease, many emerging questions on durability, predictability, reliability, and variability of response have not been answered. The underlying biology accounting for these heterogeneous responses and the interplay between host and virus is the subject of intense investigation and the subject of this review.

Tofacitinib to prevent anti-drug antibody formation against LMB-100 immunotoxin in patients with advanced mesothelin-expressing cancers

Background

LMB-100 is a mesothelin (MSLN)-targeting recombinant immunotoxin (iTox) carrying a Pseudomonas exotoxin A payload that has shown promise against solid tumors, however, efficacy is limited by the development of neutralizing anti-drug antibodies (ADAs). Tofacitinib is an oral Janus Kinase (JAK) inhibitor that prevented ADA formation against iTox in preclinical studies.

Methods

A phase 1 trial testing LMB-100 and tofacitinib in patients with MSLN-expressing cancers (pancreatic adenocarcinoma, n=13; cholangiocarcinoma, n=1; appendiceal carcinoma, n=1; cystadenocarcinoma, n=1) was performed to assess safety and to determine if tofacitinib impacted ADA formation. Participants were treated for up to 3 cycles with LMB-100 as a 30-minute infusion on days 4, 6, and 8 at two dose levels (100 and 140 µg/kg) while oral tofacitinib was administered for the first 10 days of the cycle (10 mg BID). Peripheral blood was collected for analysis of ADA levels, serum cytokines and circulating immune subsets.

Results

The study was closed early due to occurrence of drug-induced pericarditis in 2 patients. Pericarditis with the combination was not reproducible in a transgenic murine model containing human MSLN. Two of 4 patients receiving all 3 cycles of treatment maintained effective LMB-100 levels, an unusual occurrence. Sustained increases in systemic IL-10 and TNF-α were seen, a phenomenon not observed in prior LMB-100 studies. A decrease in activated T cell subsets and an increase in circulating immunosuppressive myeloid populations occurred. No radiologic decreases in tumor volume were observed.

Discussion

Further testing of tofacitinib to prevent ADA formation is recommended in applicable non-malignant disease settings.

Clinical trial registration

https://www.clinicaltrials.gov/study/NCT04034238.

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.

Factor IX administration in the skin primes inhibitor formation and sensitizes hemophilia B mice to systemic factor IX administration

Background

Factor IX inhibitor formation is the most serious complication of replacement therapy for the bleeding disorder hemophilia B, exacerbated by severe allergic reactions occurring in up to 60% of patients with inhibitors. Low success rates of immune tolerance induction therapy in hemophilia B necessitate the search for novel immune tolerance therapies. Skin-associated lymphoid tissues have been successfully targeted in allergen-specific immunotherapy.

Objectives

We aimed to develop a prophylactic immune tolerance protocol based on intradermal administration of FIX that would prevent inhibitor formation and/or anaphylaxis in response to replacement therapy.

Methods

We measured FIX inhibitor, anti-FIX immunoglobulin G1, and immunoglobulin E titers using the Bethesda assay and enzyme-linked immunosorbent assay after 4 weeks of twice-weekly intradermal FIX or FIX-Fc administration followed by 5 to 6 weeks of weekly systemic FIX injections in C3H/HeJ hemophilia B mice. We also measured skin antigen-presenting, follicular helper T, and germinal center B cell frequencies in skin-draining lymph nodes after a single or repeat intradermal FIX administration.

Results

Intradermal administration enhanced FIX inhibitor formation in response to systemic administration. We further found that intradermal administration alone triggers inhibitor formation, even at a low dose of 0.4 IU/kg, which is 100-fold lower than the intravenous dose of 40 IU/kg typically required to induce inhibitor development in hemophilia B mice. Also, intradermal administration triggered germinal center formation in skin-draining lymph nodes and sensitized mice to systemic administration. Factor IX-Fc fusion protein did not modulate inhibitor formation.

Conclusion

Intradermal FIX administration is highly immunogenic, suggesting that the skin compartment is not amenable to immune tolerance induction or therapeutic delivery of clotting factors.

Phase 3 Trial of Concizumab in Hemophilia with Inhibitors

BACKGROUND

Concizumab is an anti-tissue factor pathway inhibitor monoclonal antibody designed to achieve hemostasis in all hemophilia types, with subcutaneous administration. A previous trial of concizumab (explorer4) established proof of concept in patients with hemophilia A or B with inhibitors.

METHODS

We conducted the explorer7 trial to assess the safety and efficacy of concizumab in patients with hemophilia A or B with inhibitors. Patients were randomly assigned in a 1:2 ratio to receive no prophylaxis for at least 24 weeks (group 1) or concizumab prophylaxis for at least 32 weeks (group 2) or were nonrandomly assigned to receive concizumab prophylaxis for at least 24 weeks (groups 3 and 4). After a treatment pause due to nonfatal thromboembolic events in three patients receiving concizumab, including one from the explorer7 trial, concizumab therapy was restarted with a loading dose of 1.0 mg per kilogram of body weight, followed by 0.2 mg per kilogram daily (potentially adjusted on the basis of concizumab plasma concentration as measured at week 4). The primary end-point analysis compared treated spontaneous and traumatic bleeding episodes in group 1 and group 2. Safety, patient-reported outcomes, and pharmacokinetics and pharmacodynamics were also assessed.

RESULTS

Of 133 enrolled patients, 19 were randomly assigned to group 1 and 33 to group 2; the remaining 81 were assigned to groups 3 and 4. The estimated mean annualized bleeding rate in group 1 was 11.8 episodes (95% confidence interval [CI], 7.0 to 19.9), as compared with 1.7 episodes (95% CI, 1.0 to 2.9) in group 2 (rate ratio, 0.14 [95% CI, 0.07 to 0.29]; P<0.001). The overall median annualized bleeding rate for patients receiving concizumab (groups 2, 3, and 4) was 0 episodes. No thromboembolic events were reported after concizumab therapy was restarted. The plasma concentrations of concizumab remained stable over time.

CONCLUSIONS

Among patients with hemophilia A or B with inhibitors, the annualized bleeding rate was lower with concizumab prophylaxis than with no prophylaxis. (Funded by Novo Nordisk; explorer7 ClinicalTrials.gov number, NCT04083781.).

Transplanting FVIII/ET3-secreting cells in fetal sheep increases FVIII levels long-term without inducing immunity or toxicity

Hemophilia A is the most common X-linked bleeding disorder affecting more than half-a-million individuals worldwide. Persons with severe hemophilia A have coagulation FVIII levels <1% and experience spontaneous debilitating and life-threatening bleeds. Advances in hemophilia A therapeutics have significantly improved health outcomes, but development of FVIII inhibitory antibodies and breakthrough bleeds during therapy significantly increase patient morbidity and mortality. Here we use sheep fetuses at the human equivalent of 16-18 gestational weeks, and we show that prenatal transplantation of human placental cells (107-108/kg) bioengineered to produce an optimized FVIII protein, results in considerable elevation in plasma FVIII levels that persists for >3 years post-treatment. Cells engraft in major organs, and none of the recipients mount immune responses to either the cells or the FVIII they produce. Thus, these studies attest to the feasibility, immunologic advantage, and safety of treating hemophilia A prior to birth.

Efanesoctocog alfa for the prevention and treatment of bleeding in patients with hemophilia A

INTRODUCTION

Hemophilia A is an inherited bleeding disorder due to a deficiency of coagulation factor VIII (FVIII). Prevention and treatment of bleeding is traditionally through intravenous infusion of a FVIII concentrate. Modifications of recombinant FVIII (rFVIII) with an aim to prolong the half-life have been modest, thought because FVIII is dependent on plasma von Willebrand factor (VWF) for its half-life. Efanesoctocog alfa (ALTUVIIIO), approved by the Federal Drug Administration (FDA) in February 2023, was made independent of endogenous VWF by linking of the FVIII-binding D'D3 domain of VWF to B-domain deleted single chain FVIII.

AREAS COVERED

This review will outline the development of efanesoctocog alfa and the pharmacokinetic and safety data from clinical trials, as well as efficacy data from the phase 3 trials. These data formed the basis for the FDA approval.

EXPERT OPINION

Efanesoctocog alfa is a new type of FVIII replacement with an extended half-life allowing once weekly dosing to achieve hemostasis and FVIII trough levels of 13-15 IU/dL. This provides a highly effective option for treatment and prevention of bleeding in hemophilia A, where FVIII levels are easily measured. It also provides an option for treatment of bleeding and coverage for surgery with few infusions.

In vivo genome editing for hemophilia B therapy by the combination of rebalancing and therapeutic gene knockin using a viral and non-viral vector

Recent therapeutic strategies for hemophilia include long-term therapeutic gene expression using adeno-associated virus (AAV) and rebalancing therapy via the downregulation of anticoagulant pathways. However, these approaches have limitations in immune responses or insufficiency to control acute bleeding. Thus, we developed a therapeutic strategy for hemophilia B by a combined rebalancing and human factor 9 (hF9) gene knockin (KI) using a lipid nanoparticle (LNP) and AAV. Antithrombin (AT; Serpin Family C Member 1 [Serpinc1]) was selected as the target anticoagulation pathway for the gene KI. First, the combined use of LNP-clustered regularly interspaced short palindromic repeats (CRISPR) and AAV donor resulted in 20% insertions or deletions (indels) in Serpinc1 and 67% reduction of blood mouse AT concentration. Second, hF9 coding sequences were integrated into approximately 3% of the target locus. hF9 KI yielded approximately 1,000 ng/mL human factor IX (hFIX) and restored coagulation activity to a normal level. LNP-CRISPR injection caused sustained AT downregulation and hFIX production up to 63 weeks. AT inhibition and hFIX protein-production ability could be maintained by the proliferation of genetically edited hepatocytes in the case of partial hepatectomy. The co-administration of AAV and LNP showed no severe side effects except random integrations. Our results demonstrate hemophilia B therapy by a combination of rebalancing and hF9 KI using LNP and AAV.

Suppression of anti-drug antibody formation against coagulation factor VIII by oral delivery of anti-CD3 monoclonal antibody in hemophilia A mice

Active tolerance to ingested dietary antigens forms the basis for oral immunotherapy to food allergens or autoimmune self-antigens. Alternatively, oral administration of anti-CD3 monoclonal antibody can be effective in modulating systemic immune responses without T cell depletion. Here we assessed the efficacy of full length and the F(ab')2 fragment of oral anti-CD3 to prevent anti-drug antibody (ADA) formation to clotting factor VIII (FVIII) protein replacement therapy in hemophilia A mice. A short course of low dose oral anti-CD3 F(ab')2 reduced the production of neutralizing ADAs, and suppression was significantly enhanced when oral anti-CD3 was timed concurrently with FVIII administration. Tolerance was accompanied by the early induction of FoxP3+LAP-, FoxP3+LAP+, and FoxP3-LAP+ populations of CD4+ T cells in the spleen and mesenteric lymph nodes. FoxP3+LAP+ Tregs expressing CD69, CTLA-4, and PD1 persisted in spleens of treated mice, but did not produce IL-10. Finally, we attempted to combine the anti-CD3 approach with oral intake of FVIII antigen (using our previously established method of using lettuce plant cells transgenic for FVIII antigen fused to cholera toxin B (CTB) subunit, which suppresses ADAs in part through induction of IL-10 producing FoxP3-LAP+ Treg). However, combining these two approaches failed to improve suppression of ADAs. We conclude that oral anti-CD3 treatment is a promising approach to prevention of ADA formation in systemic protein replacement therapy, albeit via mechanisms distinct from and not synergistic with oral intake of bioencapsulated antigen.

Syndecan-4 Mediates the Cellular Entry of Adeno-Associated Virus 9

Due to their low pathogenicity, immunogenicity, and long-term gene expression, adeno-associated virus (AAV) vectors emerged as safe and efficient gene delivery tools, over-coming setbacks experienced with other viral gene delivery systems in early gene therapy trials. Among AAVs, AAV9 can translocate through the blood-brain barrier (BBB), making it a promising gene delivery tool for transducing the central nervous system (CNS) via systemic administration. Recent reports on the shortcomings of AAV9-mediated gene delivery into the CNS require reviewing the molecular base of AAV9 cellular biology. A more detailed understanding of AAV9's cellular entry would eradicate current hurdles and enable more efficient AAV9-based gene therapy approaches. Syndecans, the transmembrane family of heparan-sulfate proteoglycans, facilitate the cellular uptake of various viruses and drug delivery systems. Utilizing human cell lines and syndecan-specific cellular assays, we assessed the involvement of syndecans in AAV9's cellular entry. The ubiquitously expressed isoform, syndecan-4 proved its superiority in facilitating AAV9 internalization among syndecans. Introducing syndecan-4 into poorly transducible cell lines enabled robust AAV9-dependent gene transduction, while its knockdown reduced AAV9's cellular entry. Attachment of AAV9 to syndecan-4 is mediated not just by the polyanionic heparan-sulfate chains but also by the cell-binding domain of the extracellular syndecan-4 core protein. Co-immunoprecipitation assays and affinity proteomics also confirmed the role of syndecan-4 in the cellular entry of AAV9. Overall, our findings highlight the universally expressed syndecan-4 as a significant contributor to the cellular internalization of AAV9 and provide a molecular-based, rational explanation for the low gene delivery potential of AAV9 into the CNS.

Pathogenesis and treatment of osteoporosis in patients with hemophilia

INTRODUCTION

Hemophilia is a rare X-linked recessive inherited bleeding disorder caused by mutations of the genes encoding coagulation factor VIII (FVIII) or IX (FIX). Patients with hemophilia (PWH) often have a high risk of osteoporosis and fractures that is usually ignored. Herein, we review the underlying mechanisms of osteoporosis and the increased risk of fractures and their treatment in patients with FVIII or FIX deficiency.

METHODS

The PubMed, Web of Science, Embase, and Cochrane Library databases were searched to identify original research articles, meta-analyses, and scientific reviews on the mechanisms or treatment of osteoporosis in PWH.

RESULTS

The pathogenic mechanisms of osteoporosis in PWH are multifactorial and remain unclear. The available evidence shows that FVIII and FIX deficiency may directly affect bone metabolism by interfering with the RANK/RANKL/OPG pathway. Other potential mechanisms of osteoporosis in PWH include thrombin deficiency and the unloading and immobilization of bone, which will affect osteoblast and osteoclast activity by changing the cytokine profiles. The treatment of osteoporosis in PWH includes antiresorptive, anabolic, and dual-action drugs; weight-bearing exercise; fall prevention; and prophylactic coagulation factor replacement therapy. However, clinical studies of the efficacy of anti-osteoporotic agents in osteoporosis of PWH are urgently needed.

CONCLUSION

This review summarizes recent progress in research on the pathogenesis of osteoporosis in PWH and provides insights into potential treatment for osteoporosis in PWH.

Considerations for shared decision management in previously untreated patients with hemophilia A or B

Recent advances in therapeutics are now providing a wide range of options for adults and children living with hemophilia. Although therapeutic choices are also increasing for the youngest individuals with severe disease, challenges remain about early management decisions, as supporting data are currently limited. Parents and healthcare professionals are tasked with helping children achieve an inclusive quality of life and maintain good joint health into adulthood. Primary prophylaxis is the gold standard to optimize outcomes and is recommended to start before 2 years of age. A range of topics need to be discussed with parents to aid their understanding of the decisions they can make and how these will affect the management of their child/children. For those with a family history of hemophilia, prenatal considerations include the possibility of genetic counseling, prenatal investigations, and planning for delivery, together with monitoring of the mother and neonate, as well as diagnosis of the newborn and treatment of any birth-associated bleeding. Subsequent considerations, which are also applicable to families where infant bleeding has resulted in a new diagnosis of sporadic hemophilia, involve explaining bleed recognition and treatment options, practical aspects of initiating/continuing prophylaxis, dealing with bleeds, and ongoing aspects of treatment, including possible inhibitor development. Over time, optimizing treatment efficacy, in which individualizing therapy around activities can play a role, and long-term considerations, including retaining joint health and tolerance maintenance, become increasingly important. The evolving treatment landscape is creating a need for continually updated guidance. Multidisciplinary teams and peers from patient organizations can help provide relevant information. Easily accessible, multidisciplinary comprehensive care remains a foundation to care. Equipping parents early with the knowledge to facilitate truly informed decision-making will help achieve the best possible longer-term health equity and quality of life for the child and family living with hemophilia.

Plain language summary

Points to be taken into account to help families make decisions to best care for children born with hemophilia Medical advances are providing a range of treatment options for adults and children with hemophilia. There is, however, relatively limited information about managing newborns with the condition. Doctors and nurses can help parents to understand the choices for infants born with hemophilia. We describe the various points doctors and nurses should ideally discuss with families to enable informed decision-making. We focus on infants who require early treatment to prevent spontaneous or traumatic bleeding (prophylaxis), which is recommended to start before 2 years of age. Families with a history of hemophilia may benefit from discussions before pregnancy, including how an affected child would be treated to protect against bleeds. When mothers are pregnant, doctors can explain investigations that can provide information about their unborn child, plan for the birth, and monitor mother and baby to minimize bleed risks at delivery. Testing will confirm whether the baby is affected by hemophilia. Not all infants with hemophilia will be born to families with a history of the condition. Identification of hemophilia for the first time in a family (which is 'sporadic hemophilia') occurs in previously undiagnosed infants who have bleeds requiring medical advice and possibly hospital treatment. Before any mothers and babies with hemophilia are discharged from hospital, doctors and nurses will explain to parents how to recognize bleeding and available treatment options can be discussed. Over time, ongoing discussions will help parents to make informed treatment decisions:• When and how to start, then continue, prophylaxis.• How to deal with bleeds (reinforcing previous discussions about bleed recognition and treatment) and other ongoing aspects of treatment. ○ For instance, children may develop neutralizing antibodies (inhibitors) to treatment they are receiving, requiring a change to the planned approach.• Ensuring treatment remains effective as their child grows, considering the varied needs and activities of their child.

Adding recombinant AAVs to the cancer therapeutics mix

Gene therapy is a powerful biological tool that is reshaping therapeutic landscapes for several diseases. Researchers are using both non-viral and viral-based gene therapy methods with success in the lab and the clinic. In the cancer biology field, gene therapies are expanding treatment options and the possibility of favorable outcomes for patients. While cellular immunotherapies and oncolytic virotherapies have paved the way in cancer treatments based on genetic engineering, recombinant adeno-associated virus (rAAV), a viral-based module, is also emerging as a potential cancer therapeutic through its malleability, specificity, and broad application to common as well as rare tumor types, tumor microenvironments, and metastatic disease. A wide range of AAV serotypes, promoters, and transgenes have been successful at reducing tumor growth and burden in preclinical studies, suggesting more groundbreaking advances using rAAVs in cancer are on the horizon.

Long-term prophylaxis: what are our options and how to define success?

Currently, we are at an enviable place in hemophilia treatment. Although full prophylaxis with standard half-life recombinant or plasma-derived factor concentrates has been definitively shown to be inadequate for full protection against bleeding and arthropathy, a number of novel therapies with improved hemostatic enhancement are clinically available or in promising clinical trials. In order to compare outcomes among a number of very efficacious therapies, it is necessary to have sensitive tools employed in long-term follow-up for several years for participants with no or minimal joint disease. The tool kit must be comprehensive, with outcomes of bleeding, factor level restoration or hemostatic capacity, joint structure, joint function, pain, quality of life, and patient satisfaction. This article reviews the history of prophylaxis, the promise of emerging therapies, and the sensitive tools used to assess long-term efficacy for joint structure and function.

Hemophilia a patients with inhibitors: Mechanistic insights and novel therapeutic implications

The development of coagulation factor VIII (FVIII) inhibitory antibodies is a serious complication in hemophilia A (HA) patients after FVIII replacement therapy. Inhibitors render regular prophylaxis ineffective and increase the risk of morbidity and mortality. Immune tolerance induction (ITI) regimens have become the only clinically proven therapy for eradicating these inhibitors. However, this is a lengthy and costly strategy. For HA patients with high titer inhibitors, bypassing or new hemostatic agents must be used in clinical prophylaxis due to the ineffective ITI regimens. Since multiple genetic and environmental factors are involved in the pathogenesis of inhibitor generation, understanding the mechanisms by which inhibitors develop could help identify critical targets that can be exploited to prevent or eradicate inhibitors. In this review, we provide a comprehensive overview of the recent advances related to mechanistic insights into anti-FVIII antibody development and discuss novel therapeutic approaches for HA patients with inhibitors.

IL-15 blockade and rapamycin rescue multifactorial loss of factor VIII from AAV-transduced hepatocytes in hemophilia A mice

Hepatic adeno-associated viral (AAV) gene transfer has the potential to cure the X-linked bleeding disorder hemophilia A. However, declining therapeutic coagulation factor VIII (FVIII) expression has plagued clinical trials. To assess the mechanistic underpinnings of this loss of FVIII expression, we developed a hemophilia A mouse model that shares key features observed in clinical trials. Following liver-directed AAV8 gene transfer in the presence of rapamycin, initial FVIII protein expression declines over time in the absence of antibody formation. Surprisingly, loss of FVIII protein production occurs despite persistence of transgene and mRNA, suggesting a translational shutdown rather than a loss of transduced hepatocytes. Some of the animals develop ER stress, which may be linked to hepatic inflammatory cytokine expression. FVIII protein expression is preserved by interleukin-15/interleukin-15 receptor blockade, which suppresses CD8+ T and natural killer cell responses. Interestingly, mice with initial FVIII levels >100% of normal had diminishing expression while still under immune suppression. Taken together, our findings of interanimal variability of the response, and the ability of the immune system to shut down transgene expression without utilizing cytolytic or antibody-mediated mechanisms, illustrate the challenges associated with FVIII gene transfer. Our protocols based upon cytokine blockade should help to maintain efficient FVIII expression.

Site-specific genome editing in treatment of inherited diseases: possibility, progress, and perspectives

Advancements in genome editing enable permanent changes of DNA sequences in a site-specific manner, providing promising approaches for treating human genetic disorders caused by gene mutations. Recently, genome editing has been applied and achieved significant progress in treating inherited genetic disorders that remain incurable by conventional therapy. Here, we present a review of various programmable genome editing systems with their principles, advantages, and limitations. We introduce their recent applications for treating inherited diseases in the clinic, including sickle cell disease (SCD), β-thalassemia, Leber congenital amaurosis (LCA), heterozygous familial hypercholesterolemia (HeFH), etc. We also discuss the paradigm of ex vivo and in vivo editing and highlight the promise of somatic editing and the challenge of germline editing. Finally, we propose future directions in delivery, cutting, and repairing to improve the scope of clinical applications.

Multiple criteria decision analysis for therapeutic innovations in a hemophilia care center: A pilot study of the organizational impact of innovation in hemophilia care management

Background

Several innovative drugs liable to lead to changes in healthcare organization are or soon will be available for the management of hemophilia. Analyzing their implementation can shed further light on healthcare decision-making, to anticipate changes and risk of breakdown in the patient’s care pathway.

Methods

Multiple criteria decision analysis (MCDA), based on ISPOR recommendations, was used to assess the organizational impact of innovation in hemophilia care management. The MCDA process designed for this specific context involved ten French experts in hemophilia care management (physicians, nurses, pharmacist, physiotherapist and psychologist) in the hemophilia care center of Chambéry, in the Rhône-Alpes Region of France. This pilot study involved seven steps: (i) defining the decision problem; (ii) selecting and structuring criteria; (iii) assessing the relative weight of each criterion with software-assisted simulation based on pairwise comparisons of different organizational change scenarios; (iv) measuring the performance of the selected innovations; (v) scoring alternatives; (vi) calculating aggregate scores; (vii) discussion. The endpoint was to determine the expected overall organizational impact on a 0–100 scale.

Results

Seven organizational criteria were selected. "Acceptability for patient/caregiver/association" was the most heavily weighted. Factor VIII by subcutaneous route obtained the highest aggregate score: i.e., low impact on care organization (88.8 out of 100). The innovation with strongest organizational impact was gene therapy (27.3 out of 100).

Conclusion

This approach provided a useful support for discussion, integrating organizational aspects in the treatment decision-making process, at healthcare team level. The study needs repeating in a few years’ time and in other hemophilia centers.

Immune complications and their management in inherited and acquired bleeding disorders

Disorders of coagulation, resulting in serious risks for bleeding, may be caused by autoantibody formation or by mutations in genes encoding coagulation factors. In the latter case, antidrug antibodies (ADAs) may form against the clotting factor protein drugs used in replacement therapy, as is well documented in the treatment of the X-linked disease hemophilia. Such neutralizing antibodies against factors VIII or IX substantially complicate treatment. Autoantibody formation against factor VIII leads to acquired hemophilia. Although rare, antibody formation may occur in the treatment of other clotting factor deficiencies (eg, against von Willebrand factor [VWF]). The main strategies that have emerged to address these immune responses include (1) clinical immune tolerance induction (ITI) protocols; (2) immune suppression therapies (ISTs); and (3) the development of drugs that can improve hemostasis while bypassing the antibodies against coagulation factors altogether (some of these nonfactor therapies/NFTs are antibody-based, but they are distinct from traditional immunotherapy as they do not target the immune system). Choice of immune or alternative therapy and criteria for selection of a specific regimen for inherited and autoimmune bleeding disorders are explained. ITI serves as an important proof of principle that antigen-specific immune tolerance can be achieved in humans through repeated antigen administration, even in the absence of immune suppression. Finally, novel immunotherapy approaches that are still in the preclinical phase, such as cellular (for instance, regulatory T cell [Treg]) immunotherapies, gene therapy, and oral antigen administration, are discussed.

Genome editing-mediated knock-in of therapeutic genes ameliorates the disease phenotype in a model of hemophilia

Recently, clinical trials of adeno-associated virus-mediated replacement therapy have suggested long-term therapeutic effects for several genetic diseases of the liver, including hemophilia. However, there remain concerns regarding decreased therapeutic effects when the liver is regenerated or when physiological proliferation occurs. Although genome editing using the clustered regularly interspaced short palindromic repeats/Cas9 system provides an opportunity to solve this problem, low knock-in efficiency may limit its application for therapeutically relevant expression. Here, we identified a novel gene, APOC3, in which a strong promoter facilitated the expression of knocked-in genes in hepatocytes. We also investigated the effects of APOC3 editing using a small Cas9 protein derived from Campylobacter jejuni (CjCas9) in a hemophilic model. We demonstrated that adeno-associated virus-mediated delivery of CjCas9 and donor led to moderate levels of human factor 9 expression in APOC3-humanized mice. Moreover, knock-in-driven expression induced substantial recovery of clotting function in mice with hemophilia B. There was no evidence of off-target editing in vitro or in vivo. Collectively, our findings demonstrated therapeutically relevant expression using a precise and efficient APOC3-editing platform, providing insights into the development of further long-term therapeutics for diverse monogenic liver diseases.

Adeno-associated virus-mediated expression of activated factor V (FVa) for hemophilia phenotypic correction

Adeno-associated virus (AAV) gene therapy has been successfully applied in hemophilia patients excluding patients with inhibitors. During the coagulation pathway, activated factor V (FVa) functions downstream as a cofactor of activated factor X (FXa) to amplify thrombin generation. We hypothesize that the expression of FVa via gene therapy can improve hemostasis of both factor IX and FVIII deficiencies, regardless of clotting factor inhibitor. A human FVa (hFVa) expression cassette was constructed, and AAV8 vectors encoding hFVa (AAV8/TTR-hFVa) were intravenously administrated into mice with hemophilia A and B with or without FVIII inhibitors. Hemostasis, including hFVa level, activated partial thromboplastin time (aPTT), tail clip, and the saphenous vein bleeding assay (SVBA), was evaluated. In hemophilia B mice, a dose of 4 × 1013 vg/kg AAV8/TTR-hFVa vectors achieved a complete phenotypic correction over 28 weeks. In hemophilia A mice, hemostasis improvement was also achieved, regardless of FVIII inhibitor development. In vivo hemostasis efficacy was confirmed by tail clip and SVBA. Interestingly, while minimal shortening of aPTT was observed at a lower dose of AAV8 vectors, hemostasis improvement was still achieved via in vivo bleeding assays. Collectively, FVa-based AAV gene therapy shows promise for hemostasis correction in hemophilia, regardless of inhibitor development and no potential risk for thrombosis.

In Vitro Conditioning of Adipose-Derived Mesenchymal Stem Cells by the Endothelial Microenvironment: Modeling Cell Responsiveness towards Non-Genetic Correction of Haemophilia A

In recent decades, the use of adult multipotent stem cells has paved the way for the identification of new therapeutic approaches for the treatment of monogenic diseases such as Haemophilia A. Being already studied for regenerative purposes, adipose-derived mesenchymal stem cells (Ad-MSCs) are still poorly considered for Haemophilia A cell therapy and their capacity to produce coagulation factor VIII (FVIII) after proper stimulation and without resorting to gene transfection. In this work, Ad-MSCs were in vitro conditioned towards the endothelial lineage, considered to be responsible for coagulation factor production. The cells were cultured in an inductive medium enriched with endothelial growth factors for up to 21 days. In addition to significantly responding to the chemotactic endothelial stimuli, the cell populations started to form capillary-like structures and up-regulated the expression of specific endothelial markers (CD34, PDGFRα, VEGFR2, VE-cadherin, CD31, and vWF). A dot blot protein study detected the presence of FVIII in culture media collected from both unstimulated and stimulated Ad-MSCs. Remarkably, the activated partial thromboplastin time test demonstrated that the clot formation was accelerated, and FVIII activity was enhanced when FVIII deficient plasma was mixed with culture media from the untreated/stimulated Ad-MSCs. Overall, the collected evidence supported a possible Ad-MSC contribution to HA correction via specific stimulation by the endothelial microenvironment and without any need for gene transfection.

Gene therapy - are we ready now?

Introduction

Haemophilia therapy has evolved from rudimentary transfusion‐based approaches to an unprecedented level of innovation with glimmers of functional cure brought by gene therapy. After decades of misfires, gene therapy has normalized factor (F)VIII and factor (F)IX levels in some individuals in the long term. Several clinical programmes testing adeno‐associated viral (AAV) vector gene therapy are approaching completion with imminent regulatory approvals.

Discussion

Phase 3 studies along with multiyear follow‐up in earlier phase investigations raised questions about efficacy as well as short‐ and long‐term safety, prompting a reappraisal of AAV vector gene therapy. Liver toxicities, albeit mostly low‐grade, occur in the first year in at least some individuals in all haemophilia A and B trials and are poorly understood. Extreme variability and unpredictability of outcome, as well as a slow decline in factor expression (seemingly unique to FVIII gene therapy), are vexing because immune responses to AAV vectors preclude repeat dosing, which could increase suboptimal or restore declining expression, while overexpression may result in phenotoxicity. The long‐term safety will need lifelong monitoring because AAV vectors, contrary to conventional wisdom, integrate into chromosomes at the rate that calls for vigilance.

Conclusions

AAV transduction and transgene expression engage the host immune system, cellular DNA processing, transcription and translation machineries in ways that have been only cursorily studied in the clinic. Delineating those mechanisms will be key to finding mitigants and solutions to the remaining problems, and including individuals who cannot avail of gene therapy at this time.

Managing invasive procedures in haemophilia patients with limited resources, extended half-life concentrates or non-replacement therapies in 2022

New treatment possibilities and modalities are now available globally for patients with haemophilia requiring surgery or invasive procedures. The first is the appropriate application of low-dose protocols of clotting factor concentrates (CFC) achieving adequate perioperative haemostasis in resources constraint environments. The increasing availability of CFC through humanitarian aid programs allows more invasive surgeries to be performed for which efficacy and safety data should be more widely collected and reported. Second, extended half-life CFC that are increasingly available in many countries represent valuable alternatives to standard half-life products in surgical patients allowing reduced number of infusions and lower consumption, in particular for extended half-life factor IX. Third, in the era of recently introduced nonfactor prophylaxis, some minor surgical procedures can now be performed without additional haemostatic treatment, others with few low-dose administrations of CFC or bypassing agents. Additional factor VIII/IX or recombinant activated factor VII has proven to be safe and effective in association with emicizumab for major surgeries and it was effectively given at low doses in association with fitusiran (including activated prothrombin complex concentrate). No thrombotic complications have been reported in the surgical setting so far. A multidisciplinary team/facility remains crucial to manage major surgery in patients on prophylaxis with these new agents.

Liver gene therapy with intein-mediated F8 trans-splicing corrects mouse haemophilia A

Liver gene therapy with adeno‐associated viral (AAV) vectors is under clinical investigation for haemophilia A (HemA), the most common inherited X‐linked bleeding disorder. Major limitations are the large size of the F8 transgene, which makes packaging in a single AAV vector a challenge, as well as the development of circulating anti‐F8 antibodies which neutralise F8 activity. Taking advantage of split‐intein‐mediated protein trans‐splicing, we divided the coding sequence of the large and highly secreted F8‐N6 variant in two separate AAV‐intein vectors whose co‐administration to HemA mice results in the expression of therapeutic levels of F8 over time. This occurred without eliciting circulating anti‐F8 antibodies unlike animals treated with the single oversized AAV‐F8 vector under clinical development. Therefore, liver gene therapy with AAV‐F8‐N6 intein should be considered as a potential therapeutic strategy for HemA.

Pharmacokinetic analysis identifies a factor VIII immunogenicity threshold after AAV gene therapy in hemophilia A mice

Advances in the development of novel treatment options for hemophilia A are prevalent. However, the anti-factor VIII (FVIII) neutralizing antibody (inhibitor) response to existing FVIII products remains a major treatment challenge. Although some novel products are designed to function in the presence of inhibitors, they do not specific address the immunogenicity risk or mechanistic causes of inhibitor development, which remain unclear. Furthermore, most preclinical studies supporting clinical gene therapy programs have reported immunogenicity signals in animal models, especially at higher vector doses and sometimes using multiple vector designs. In these settings, immunogenicity risk factor determination, comparative immunogenicity of competing vector designs, and the potential for obtaining meaningful prognostic data remain relatively unexplored. Additionally, there remains the opportunity to investigate clinical gene therapy as an alternative to standard immune tolerance induction therapy. The current study was designed to address these issues through longitudinal dose-response evaluation of 4 adeno-associated viral (AAV) vector candidates encoding 2 different FVIII transgenes in a murine model of hemophilia A. Plasma FVIII activity and anti-FVIII antibody data were used to generate a pharmacokinetic model that (1) identifies initial AAV-FVIII product expression kinetics as the dominant risk factor for inhibitor development, (2) predicts a therapeutic window where immune tolerance is achieved, and (3) demonstrates evidence of gene therapy-based immune tolerance induction. Although there are known limitations to the predictive value of preclinical immunogenicity testing, these studies can uncover or support the development of design principles that can guide the development of safe and effective genetic medicines.

Engineered Molecular Therapeutics Targeting Fibrin and the Coagulation System: a Biophysical Perspective

The coagulation cascade represents a sophisticated and highly choreographed series of molecular events taking place in the blood with important clinical implications. One key player in coagulation is fibrinogen, a highly abundant soluble blood protein that is processed by thrombin proteases at wound sites, triggering self-assembly of an insoluble protein hydrogel known as a fibrin clot. By forming the key protein component of blood clots, fibrin acts as a structural biomaterial with biophysical properties well suited to its role inhibiting fluid flow and maintaining hemostasis. Based on its clinical importance, fibrin is being investigated as a potentially valuable molecular target in the development of coagulation therapies. In this topical review, we summarize our current understanding of the coagulation cascade from a molecular, structural and biophysical perspective. We highlight single-molecule studies on proteins involved in blood coagulation and report on the current state of the art in directed evolution and molecular engineering of fibrin-targeted proteins and polymers for modulating coagulation. This biophysical overview will help acclimatize newcomers to the field and catalyze interdisciplinary work in biomolecular engineering toward the development of new therapies targeting fibrin and the coagulation system.

Concizumab as a Subcutaneous Prophylactic Treatment Option for Patients with Hemophilia A or B: A Review of the Evidence and Patient’s Perspectives

Concizumab is a monoclonal, humanized IgG4 antibody specific for the Kunitz-2 domain of Tissue Factor Pathway Inhibitor (TFPI). Preclinical studies in vitro or on animal models and in vivo have demonstrated the ability of concizumab to restore thrombin generation, promoting the establishment of a procoagulant action; all these results were subsequently confirmed in the studies of EXPLORER program. Concizumab may represent a new opportunity for the treatment of persons with hemophilia, so there is much anticipation for the results of the ongoing trials still. This review retraces all the studies on concizumab published to date, with a brief discussion about the patient’ perspectives.

Long-term efficacy and safety of subcutaneous concizumab prophylaxis in hemophilia A and hemophilia A/B with inhibitors

Despite current treatments, there remains an unmet need for patients with hemophilia. The main parts of two phase 2 trials established clinical proof-of-concept for once-daily, subcutaneous concizumab prophylaxis in patients with hemophilia A/B with inhibitors (HAwI/HBwI; explorer4) and severe hemophilia A without inhibitors (HA; explorer5,). Here, we present results from extension parts of these trials, included to evaluate longer-term safety and efficacy. Both trials included main (≥24 weeks) and extension parts (52-102 weeks), with patients receiving 0.15 mg/kg concizumab with potential dose escalation to 0.20 or 0.25 mg/kg if they experienced ≥3 treated spontaneous bleeds within 12 weeks. Endpoints included annualized bleeding rate (ABR), adverse events (AEs), and anti-drug antibody (ADA) occurrence. Thromboembolic events were AEs of special interest. Thirty-six patients with HA, 15 with HAwI and 10 with HBwI were exposed to concizumab. Estimated ABRs during the main+extension parts at last dose level were 4.8 (95% confidence interval [CI]: 3.2-7.2) and 6.4 (95% CI: 4.1-9.9) in explorer4 and explorer5, respectively (spontaneous ABRs were 1.8 [95% CI: 1.2-2.6] and 2.1 [95% CI: 1.3-3.3]). Most AEs were mild, with no deaths, events leading to withdrawal or thromboembolic events. ADAs developed in 25% of patients and were low titer and transient with no observed clinical effect in most cases. Results of the main+extension parts of these trials were consistent with the main parts. Ongoing phase 3 trials will further evaluate concizumab as a once-daily, subcutaneous treatment across hemophilia subtypes. Trials registered at www.clinicaltrials.gov (NCT03196284; NCT03196297).

Gene Therapy Advances: A Meta-Analysis of AAV Usage in Clinical Settings

Adeno-associated viruses (AAVs) are the safest and most effective gene delivery vehicles to drive long-term transgene expression in gene therapy. While animal studies have shown promising results, the translatability of AAVs into clinical settings has been partly limited due to their restricted gene packaging capacities, off-target transduction, and immunogenicity. In this study, we analysed over two decades of AAV applications, in 136 clinical trials. This meta-analysis aims to provide an up-to-date overview of the use and successes of AAVs in clinical trials, while evaluating the approaches used to address the above challenges. First, this study reveals that the speed of novel AAV development has varied between therapeutic areas, with particular room for improvement in Central Nervous System disorders, where development has been slow. Second, the lack of dose-dependent toxicity and efficacy data indicates that optimal dosing regimes remain elusive. Third, more clinical data on the effectiveness of various immune-modulation strategies and gene editing approaches are required to direct future research and to accelerate the translation of AAV-mediated gene therapy into human applications.

CAR-T Regulatory (CAR-Treg) Cells: Engineering and Applications

Regulatory T cells are critical for maintaining immune tolerance. Recent studies have confirmed their therapeutic suppressive potential to modulate immune responses in organ transplant and autoimmune diseases. However, the unknown and nonspecific antigen recognition of polyclonal Tregs has impaired their therapeutic potency in initial clinical findings. To address this limitation, antigen specificity can be conferred to Tregs by engineering the expression of transgenic T-cell receptor (TCR) or chimeric antigen receptor (CAR). In contrast to TCR Tregs, CAR Tregs are major histocompatibility complex (MHC) independent and less dependent on interleukin-2 (IL-2). Furthermore, CAR Tregs maintain Treg phenotype and function, home to the target tissue and show enhanced suppressive efficacy compared to polyclonal Tregs. Additional development of engineered CAR Tregs is needed to increase Tregs' suppressive function and stability, prevent CAR Treg exhaustion, and assess their safety profile. Further understanding of Tregs therapeutic potential will be necessary before moving to broader clinical applications. Here, we summarize recent studies utilizing CAR Tregs in modulating immune responses in autoimmune diseases, transplantation, and gene therapy and future clinical applications.

Genomic Designs of rAAVs Contribute to Pathological Changes in the Livers and Spleens of Mice

Recombinant AAV (rAAV) gene therapy is being investigated as an effective therapy for several diseases including hemophilia B. Reports of liver tumor development in certain mouse models due to AAV treatment and genomic integration of the rAAV vector has raised concerns about the long-term safety and efficacy of this gene therapy. To investigate whether rAAV treatment causes cancer, we utilized two mouse models, inbred C57BL/6 and hemophilia B Balb/C mice (HemB), to test if injecting a high dose of various rAAV8 vectors containing or lacking hFIX transgene, a Poly-A sequence, or the CB or TTR promoter triggered liver fibrosis and/or cancer development over the course of the 6.5-month study. We observed no liver tumors in either mouse cohort regardless of rAAV treatment through ultrasound imaging, gross anatomical assessment at sacrifice, and histology. We did, however, detect differences in collagen deposition in C57BL/6 livers and HemB spleens of rAAV-injected mice. Pathology reports of the HemB mice revealed many pathological phenomena, including fibrosis and inflammation in the livers and spleens across different AAV-injected HemB mice. Mice from both cohorts injected with the TTR-hFIX vector demonstrated minimal adverse events. While not tumorigenic, high dose of rAAVs, especially those with incomplete genomes, can influence liver and spleen health negatively that could be problematic for cementing AAVs as a broad therapeutic option in the clinic.

Coagulation factor IX gene transfer to non-human primates using engineered AAV3 capsid and hepatic optimized expression cassette

Hepatic gene transfer with adeno-associated viral (AAV) vectors shows much promise for the treatment of the X-linked bleeding disorder hemophilia B in multiple clinical trials. In an effort to further innovate this approach and to introduce alternative vector designs with potentially superior features into clinical development, we recently built a vector platform based on AAV serotype 3 because of its superior tropism for human hepatocytes. A vector genome with serotype-matched inverted terminal repeats expressing hyperactive human coagulation factor IX (FIX)-Padua was designed for clinical use that is optimized for translation using hepatocyte-specific codon-usage bias and is depleted of immune stimulatory CpG motifs. Here, this vector genome was packaged into AAV3 (T492V + S663V) capsid for hepatic gene transfer in non-human primates. FIX activity within or near the normal range was obtained at a low vector dose of 5 × 1011 vector genomes/kg. Pre-existing neutralizing antibodies, however, completely or partially blocked hepatic gene transfer at that dose. No CD8+ T cell response against capsid was observed. Antibodies against the human FIX transgene product formed at a 10-fold higher vector dose, albeit hepatic gene transfer was remarkably consistent, and sustained FIX activity in the normal range was nonetheless achieved in two of three animals for the 3-month duration of the study. These results support the use of this vector at low vector doses for gene therapy of hemophilia B in humans.

Homodimeric Minimal Factor H: In Vivo Tracking and Extended Dosing Studies in Factor H Deficient Mice

C3 glomerulopathy (C3G) is associated with dysregulation of the alternative pathway (AP) of complement and treatment options remain inadequate. Factor H (FH) is a potent regulator of the AP. An in-depth analysis of FH-related protein dimerised minimal (mini)-FH constructs has recently been published. This analysis showed that addition of a dimerisation module to mini-FH not only increased serum half-life but also improved complement regulatory function, thus providing a potential treatment option for C3G. Herein, we describe the production of a murine version of homodimeric mini-FH [mHDM-FH (mFH1-5^18-20^R1-2)], developed to reduce the risk of anti-drug antibody formation during long-term experiments in murine models of C3G and other complement-driven pathologies. Our analysis of mHDM-FH indicates that it binds with higher affinity and avidity to WT mC3b when compared to mouse (m)FH (mHDM-FH KD=505 nM; mFH KD=1370 nM) analogous to what we observed with the respective human proteins. The improved binding avidity resulted in enhanced complement regulatory function in haemolytic assays. Extended interval dosing studies in CFH-/- mice (5mg/kg every 72hrs) were partially effective and bio-distribution analysis in CFH-/- mice, through in vivo imaging technologies, demonstrates that mHDM-FH is preferentially deposited and remains fixed in the kidneys (and liver) for up to 4 days. Extended dosing using an AAV- human HDM-FH (hHDM-FH) construct achieved complete normalisation of C3 levels in CFH-/- mice for 3 months and was associated with a significant reduction in glomerular C3 staining. Our data demonstrate the ability of gene therapy delivery of mini-FH constructs to enhance complement regulation in vivo and support the application of this approach as a novel treatment strategy in diseases such as C3G.

Emerging drugs for hemophilia A: insights into phase II and III clinical trials

INTRODUCTION

Hemophilia is a lifelong, genetic-bleeding disorder, which inadequately treated results in permanent joint damage. It is characterized by spontaneous and trauma-related bleeding episodes. In the last 50 years, treatment has seen dramatic improvements which have improved the quality of life of persons with hemophilia.

AREAS COVERED

This review will provide a summary of current pharmacological approaches for hemophilia A as well as discuss novel agents which are either approved recently or in phase II-III clinical trials, plasma-derived and recombinant factor VIII (FVIII) products, extended half-life FVIII products, bypassing agents and non-replacement therapies.

EXPERT OPINION

Novel therapies are already changing the way that hemophilia A is managed, and as more new therapies get approved, there will be a revolution in the management of this serious condition. Clinicians will have both the opportunities as well as the challenges of incorporating such new technologies into clinical practice.

Preclinical development of plant-based oral immune modulatory therapy for haemophilia B

Anti-drug antibody (ADA) formation is a major complication in treatment of the X-linked bleeding disorder haemophilia B (deficiency in coagulation factor IX, FIX). Current clinical immune tolerance protocols are often not effective due to complications such as anaphylactic reactions against FIX. Plant-based oral tolerance induction may address this problem, as illustrated by the recent first regulatory approval of orally delivered plant cells to treat peanut allergy. Our previous studies showed that oral delivery of plant cells expressing FIX fused to the transmucosal carrier CTB (cholera toxin subunit B) in chloroplasts suppressed ADA in animals with haemophilia B. We report here creation of the first lettuce transplastomic lines expressing a coagulation factor, in the absence of antibiotic resistance gene. Stable integration of the CTB-FIX gene and homoplasmy (transformation of ˜10 000 copies in each cell) were maintained in both T1 and T2 generation marker-free plants. CTB-FIX expression in lyophilized leaves of T1 and T2 marker-free plants was 1.0-1.5 mg/g dry weight, confirming that the marker excision did not affect antigen levels. Oral administration of CTB-FIX to Sprague Dawley rats at 0.25, 1 or 2.5 mg/kg did not produce overt adverse effects or toxicity. The no-observed-adverse-effect level (NOAEL) is at least 2.5 mg/kg for a single oral administration in rats. Oral administration of CTB-FIX at 0.3 or 1.47 mg/kg either mixed in food or as an oral suspension to Beagle dogs did not produce any observable toxicity. These toxicology studies should facilitate filing of regulatory approval documents and evaluation in haemophilia B patients.

Mobile Health Technology for the Personalized Therapy of Hemophilia

The management of patients with hemophilia has evolved significantly since the first treatment attempts were made in the late 1930s. Since then, each new step in the treatment of patients with hemophilia has brought important advancements, as well as its unique set of challenges. Today, a patient-centered, individualized comprehensive approach is the new paradigm, moving away from the traditional "one size-fits-all" approach, to provide the best possible care for each patient with a bleeding disorder. As part of this complex task, mobile health applications might have the capacity to play an important role in reaching that goal. However, the use of new electronic technologies as part of a comprehensive treatment approach for patients with hemophilia simultaneously presents a new set of challenges that needs consideration. In the first section, currently available treatment of hemophilia patients will be revised, while in the second part the role of IT software in the treatment monitoring of hemophilia patients will be discussed.

The role of the physiotherapist in the management of people with haemophilia: defining the new normal

Physiotherapists aim to maximise quality of life and movement potential within the spheres of promotion, prevention, treatment/intervention and rehabilitation. Haemophilia care is witnessing a significant shift towards a new era of potentially life-changing treatments which offer a future of minimal or no bleeds for people with haemophilia. As such, physiotherapy intervention should be more proactive rather than reactive to treat and rehabilitate recurrent bleeding episodes. The role of the physiotherapist within the multidisciplinary team includes the differential diagnosis of musculoskeletal bleeding, supporting and encouraging higher levels of physical activity, rehabilitation to maximise physical potential and capabilities, assessment and treatment of non-bleed-related musculoskeletal issues, managing comorbidities and falls risk, and improving the longitudinal surveillance of musculoskeletal health. Encouraging and supporting people with haemophilia to become more active will improve wellbeing and improve health and health outcomes, and physical activity is becoming one of the most important outcomes for people with haemophilia. Recommendations on the best way to accurately capture these data are vital to ensure the full health benefits of new treatments for people with haemophilia are clear.

Disruptive technology and hemophilia care: The multiple impacts of emicizumab

Emicizumab, a bispecific antibody mimicking the action of factor VIII (FVIII), is currently the first and only approved and increasingly accessible disruptive treatment option for hemophilia A, a disease so far mainly treated with frequent intravenous infusions of FVIII concentrates or bypassing agents in case of inhibitor development. Other disruptive treatments are expected to follow, such as agents that rebalance coagulation and gene therapy with the ambition of curing hemophilia. While these treatment options represent major achievements or expectations, their adoption and implementation should consider their multiple direct and indirect, immediate or delayed, consequences on hemophilia care globally. It is these multiple changes, present and future, already visible or hypothetical, that this article intends to review and explore.

Laboratory monitoring of hemophilia A treatments: new challenges

Monitoring factor VIII (FVIII) activity has traditionally been complicated by discrepancies between assays for the various sorts of FVIII molecules. The advent of novel nonfactor therapies (emicizumab, fitusiran, and anti-tissue factor pathway inhibitor antibodies) in hemophilia A poses a new level of difficulty on the laboratory monitoring of these patients. To use the correct assays and for a proper interpretation of their results, it is pertinent to understand the mode of action of these nonfactor agents. Furthermore, the biochemical consequences for the different types of activity assays (whether it be specific FVIII activity assays or global coagulation assays) should be taken into account as well. In this review, these aspects will be discussed. In addition, the use of various animal models to estimate FVIII-equivalence of the nonfactor therapies will be presented.

Evolving AAV-delivered therapeutics towards ultimate cures

Gene therapy has entered a new era after decades-long efforts, where the recombinant adeno-associated virus (AAV) has stood out as the most potent vector for in vivo gene transfer and demonstrated excellent efficacy and safety profiles in numerous preclinical and clinical studies. Since the first AAV-derived therapeutics Glybera was approved by the European Medicines Agency (EMA) in 2012, there is an increasing number of AAV-based gene augmentation therapies that have been developed and tested for treating incurable genetic diseases. In the subsequent years, the United States Food and Drug Administration (FDA) approved two additional AAV gene therapy products, Luxturna and Zolgensma, to be launched into the market. Recent breakthroughs in genome editing tools and the combined use with AAV vectors have introduced new therapeutic modalities using somatic gene editing strategies. The promising outcomes from preclinical studies have prompted the continuous evolution of AAV-delivered therapeutics and broadened the scope of treatment options for untreatable diseases. Here, we describe the clinical updates of AAV gene therapies and the latest development using AAV to deliver the CRISPR components as gene editing therapeutics. We also discuss the major challenges and safety concerns associated with AAV delivery and CRISPR therapeutics, and highlight the recent achievement and toxicity issues reported from clinical applications.

A Rare Case of Severe Hemophilia B Combined with Hematomesenchymal Dysplasia

BACKGROUND: The prevalence of hemophilia B in the global population is approximately 1:60,000. Undifferentiated systemic mesenchymal dysplasia (uSMD) is diagnosed rather frequently, about 1:5, according to Russian authors; no data on uSMD prevalence in other countries are available. The combination of hemophilia and uSMD has grouped under the term hematomesenchymal dysplasia (HMD). This combination significantly worsens the clinical picture, prognosis, and quality of life of the patient. AIM: In this article, we present a rare clinical case of a child with a combination of hemophilia B and HMD. CASE REPORT: A clinical case of a male patient, 5 years old with hemophilia B, severe form combined with HMD, complicated by hemothorax, abscessed pulmonary lobe hematoma has presented. The presence of HMD and the above complications had an unfavorable effect on the severity of the clinical picture and the abnormal response to treatment. The main diagnostic procedures were the assessment of the phenotypic signs of HMD in combination with laboratory and instrumental examination methods such as ultrasound, computed tomography (CT) scan, and echocardiography. Vital treatment is factor IX replacement therapy and supportive one. CONCLUSION: This clinical example highlights the importance of clinical alertness to hereditary coagulopathies, which often lead to life threatening, sometimes disabling complications that significantly reduce the quality of life of children with hemophilia. Consequently, full-scale epidemiological studies of the prevalence of HMD in the population are an urgent task for the near future.

T Cell-Mediated Immune Responses to AAV and AAV Vectors

Adeno-associated virus (AAV)-mediated gene transfer has benefited patients with inherited diseases, such as hemophilia B, by achieving long-term expression of the therapeutic transgene. Nevertheless, challenges remain due to rejection of AAV-transduced cells, which in some, but not all, patients can be prevented by immunosuppression. It is assumed that CD8+ T cells induced by natural infections with AAVs are recalled by the AAV vector's capsid and upon activation eliminate cells expressing the degraded capsid antigens. Alternatively, it is feasible that AAV vectors, especially if given at high doses, induce de novo capsid- or transgene product-specific T cell responses. This chapter discusses CD8+ T cell responses to AAV infections and AAV gene transfer and avenues to prevent their activation or block their effector functions.

Immune Responses to Plasma-Derived Versus Recombinant FVIII Products

The most severe side effect of hemophilia treatment is the inhibitor development occurring in 30% of patients, during the earliest stages of treatment with factor (F)VIII concentrates. These catastrophic immune responses rapidly inactivate the infused FVIII, rendering the treatment ineffective. This complication is associated with a substantial morbidity and mortality. The risk factors involved in the onset of the inhibitors are both genetic and environmental. The source of FVIII products, i.e. plasma-derived or recombinant FVIII products, is considered one of the most relevant factors for inhibitor development. Numerous studies in the literature report conflicting data on the different immunogenicity of the products. The SIPPET randomized trial showed an increased in the inhibitor rate in patients using recombinant FVIII products than those receiving plasma-derived products in the first exposure days. The SIPPET randomized trial showed an increase in the inhibitor rate in patients using recombinant FVIII products compared to those treated with plasma-derived products in the first days of exposure. The potential increase in the immunogenicity of recombinant products can be attributed to several factors such as: the different post-translational modification in different cell lines, the presence of protein aggregates, and the role played by the chaperon protein of FVIII, the von Willebrand factor, which modulates the uptake of FVIII by antigen presenting cells (APCs). Furthermore, the presence of non-neutralizing antibodies against FVIII has shown to be in increased inhibitor development as demonstrated in a sub-analysis of the SIPPET study. In addition, the presence of the specific subclasses of the immunoglobulins may also be an important biomarker to indicate whether the inhibitor will evolve into a persistent neutralizing antibody or a transient one that would disappear without any specific treatment. Recently, the availability of novel non-replacement therapies as well as emicizumab, administered by weekly subcutaneous infusion, have significantly changed the quality of life of patients with inhibitors showing a considerable reduction of the annual bleeding rate and in most patients the absence of bleeding. Although, these novel drugs improve patients' quality of life, they do not abolish the need to infuse FVIII during acute bleeding or surgery. Therefore, the issue of immunogenicity against FVIII still remains an important side effect of hemophilia treatment.

MiR-9-1 Suppresses Cell Proliferation and Promotes Apoptosis by Targeting UHRF1 in Lung Cancer

Lung cancer is listed as the most common reason for cancer-related death all over the world despite diagnostic improvements and the development of chemotherapy and targeted therapies. MicroRNAs control both physiological and pathological processes including development and cancer. A microRNA-9 to 1 (miR-9 to 1) overexpression model in lung cancer cell lines was established and miR-9 to 1 was found to significantly suppress the proliferation rate in lung cancer cell lines, colony formation in vitro, and tumorigenicity in nude mice of A549 cells. Ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) was then identified to direct target of miR-9 to 1. The inhibition of UHRF1 by miR-9 to 1 causes G1 arrest and p15, p16, and p21 were re-expressed in miR-9 to 1 group in mRNA level and protein level. Silence of UHRF1 expression in A549 cells resulted in the similar re-expression of p15, p16, p21 which is similar with miR-9 to 1 infection. Therefore, we concluded that UHRF1 is a new target for miR-9 to 1 to suppress cell proliferation by re-expression of tumor suppressors p15, p16, and p21 mediated by UHRF1.