Gene therapy shows promise for treating haemophilia by providing continuous expression of coagulation factors. A successful gene therapy trial for haemophilia B used an AAV vector to deliver the factor IX gene to 10 patients. This resulted in stable factor IX expression levels of 1-6% in all patients for up to 4 years, allowing 4 patients to stop prophylactic treatment and others to reduce infusions. The therapy was shown to be safe and reduced total factor IX use, resulting in over £1.75 million in savings based on 2014 prices. Gene therapy may soon reach the clinic for haemophilia and offer the potential of a cure rather than just disease management with fewer required treatment events, possibly limited to a single treatment.
This document provides guidance on dental management of medically compromised children, focusing on those with bleeding disorders like hemophilia. It discusses evaluating coagulation factor levels, using local anesthetics safely, replacing deficient factors, and administering antifibrinolytic drugs to prevent bleeding complications. Minor procedures may require only local measures, while more extensive work like oral surgery demands factor replacement, antifibrinolytics, and close monitoring to safely manage bleeding risks. Prevention through oral hygiene and regular cleanings can reduce need for invasive dental work in these high-risk patients.
Gene therapy with valoctocogene roxaparvovec provided long-term benefits for patients with severe hemophilia A in clinical trials. A single infusion of the therapy resulted in increased factor VIII activity levels and significantly reduced annual bleeding rates and factor VIII utilization compared to baseline prophylactic therapy. The therapy was generally well-tolerated with most adverse events being mild to moderate and transient. Larger ongoing phase 3 trials continue to evaluate the efficacy and safety of this promising one-time gene therapy for hemophilia A.
Hemophilia is a group of hereditary bleeding disorders caused by deficiencies in clotting factors VIII or IX. The main types are hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). Symptoms include prolonged or excessive bleeding from minor injuries, bleeding into joints, muscles or internal organs. Treatment involves replacing the missing clotting factor through infusions or injections. Nursing care focuses on preventing and controlling bleeding episodes, limiting joint damage, managing pain, providing education and emotional support to patients and families.
Hemophilia is a group of inherited bleeding disorders caused by deficiencies in clotting factors VIII or IX. The main types are hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). Symptoms include prolonged bleeding from minor injuries, excessive bruising, and bleeding into joints and muscles. Treatment involves replacing the missing clotting factor through infusions of factor concentrates. Nursing care focuses on preventing and controlling bleeding episodes, limiting joint damage, managing pain, providing education and emotional support to patients and families, and ensuring proper long-term home management of the condition.
This document provides an overview of hemophilia, including:
- Hemophilia is an inherited bleeding disorder caused by deficiencies in coagulation factor VIII or IX.
- It affects males more often than females and symptoms include prolonged bleeding from cuts or wounds.
- Diagnosis involves screening tests and measuring coagulation factor levels. Severity depends on factor level.
- Treatment involves replacing the missing clotting factor through infusions or using bypassing agents for those who develop inhibitors against factor VIII or IX.
- Bypassing agents work by activating the clotting process without using the deficient factor. The choice of agent depends on factors like the treatment phase and dosing considerations.
- Monitoring is needed to track
This document discusses infective endocarditis, including its epidemiology, classification, predisposing factors, microbiology, pathogenesis, diagnosis, management, treatment, and prophylaxis. It notes that infective endocarditis is an infection of the endocardial lining of the heart, usually caused by bacteria. It can be either acute or subacute and most commonly affects patients with pre-existing heart disease. Common causative organisms include streptococci and staphylococci. Diagnosis is based on the modified Duke criteria and involves blood cultures, echocardiography, and clinical signs. Treatment involves prolonged antibiotic therapy based on culture results, often for 6 weeks. Prophylaxis with antibiotics is recommended for certain medical
Yes, intubating the trachea of a patient with hemophilia could potentially cause bleeding complications. However, with appropriate preoperative factor replacement therapy and hemostatic precautions during the procedure, endotracheal intubation can be performed safely in a patient with hemophilia.
Some special considerations include:
- Ensure adequate factor VIII levels prior to intubation (aim for >50% of normal)
- Use a well-lubricated, soft endotracheal tube to minimize trauma
- Use gentle technique and avoid multiple attempts during laryngoscopy and intubation
- Apply cricoid pressure during laryngoscopy to protect the airway
- Suction carefully after intubation
Venous thromboembolism (VTE) is a disorder that includes deep vein thrombosis and pulmonary embolism. A deep vein thrombosis (DVT) occurs when a blood clot forms in a deep vein, usually in the lower leg, thigh, or pelvis.
This document provides guidance on dental management of medically compromised children, focusing on those with bleeding disorders like hemophilia. It discusses evaluating coagulation factor levels, using local anesthetics safely, replacing deficient factors, and administering antifibrinolytic drugs to prevent bleeding complications. Minor procedures may require only local measures, while more extensive work like oral surgery demands factor replacement, antifibrinolytics, and close monitoring to safely manage bleeding risks. Prevention through oral hygiene and regular cleanings can reduce need for invasive dental work in these high-risk patients.
Gene therapy with valoctocogene roxaparvovec provided long-term benefits for patients with severe hemophilia A in clinical trials. A single infusion of the therapy resulted in increased factor VIII activity levels and significantly reduced annual bleeding rates and factor VIII utilization compared to baseline prophylactic therapy. The therapy was generally well-tolerated with most adverse events being mild to moderate and transient. Larger ongoing phase 3 trials continue to evaluate the efficacy and safety of this promising one-time gene therapy for hemophilia A.
Hemophilia is a group of hereditary bleeding disorders caused by deficiencies in clotting factors VIII or IX. The main types are hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). Symptoms include prolonged or excessive bleeding from minor injuries, bleeding into joints, muscles or internal organs. Treatment involves replacing the missing clotting factor through infusions or injections. Nursing care focuses on preventing and controlling bleeding episodes, limiting joint damage, managing pain, providing education and emotional support to patients and families.
Hemophilia is a group of inherited bleeding disorders caused by deficiencies in clotting factors VIII or IX. The main types are hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). Symptoms include prolonged bleeding from minor injuries, excessive bruising, and bleeding into joints and muscles. Treatment involves replacing the missing clotting factor through infusions of factor concentrates. Nursing care focuses on preventing and controlling bleeding episodes, limiting joint damage, managing pain, providing education and emotional support to patients and families, and ensuring proper long-term home management of the condition.
This document provides an overview of hemophilia, including:
- Hemophilia is an inherited bleeding disorder caused by deficiencies in coagulation factor VIII or IX.
- It affects males more often than females and symptoms include prolonged bleeding from cuts or wounds.
- Diagnosis involves screening tests and measuring coagulation factor levels. Severity depends on factor level.
- Treatment involves replacing the missing clotting factor through infusions or using bypassing agents for those who develop inhibitors against factor VIII or IX.
- Bypassing agents work by activating the clotting process without using the deficient factor. The choice of agent depends on factors like the treatment phase and dosing considerations.
- Monitoring is needed to track
This document discusses infective endocarditis, including its epidemiology, classification, predisposing factors, microbiology, pathogenesis, diagnosis, management, treatment, and prophylaxis. It notes that infective endocarditis is an infection of the endocardial lining of the heart, usually caused by bacteria. It can be either acute or subacute and most commonly affects patients with pre-existing heart disease. Common causative organisms include streptococci and staphylococci. Diagnosis is based on the modified Duke criteria and involves blood cultures, echocardiography, and clinical signs. Treatment involves prolonged antibiotic therapy based on culture results, often for 6 weeks. Prophylaxis with antibiotics is recommended for certain medical
Yes, intubating the trachea of a patient with hemophilia could potentially cause bleeding complications. However, with appropriate preoperative factor replacement therapy and hemostatic precautions during the procedure, endotracheal intubation can be performed safely in a patient with hemophilia.
Some special considerations include:
- Ensure adequate factor VIII levels prior to intubation (aim for >50% of normal)
- Use a well-lubricated, soft endotracheal tube to minimize trauma
- Use gentle technique and avoid multiple attempts during laryngoscopy and intubation
- Apply cricoid pressure during laryngoscopy to protect the airway
- Suction carefully after intubation
Venous thromboembolism (VTE) is a disorder that includes deep vein thrombosis and pulmonary embolism. A deep vein thrombosis (DVT) occurs when a blood clot forms in a deep vein, usually in the lower leg, thigh, or pelvis.
Webinar Series on COVID-19 vaccine: Jointly organized by Malaysian Society of Infection Control and Infectious Diseases (MyICID) & Institute for Clinical Research (ICR), NIH
Speaker: Dr. Veena Selvaratnam is a Haematologist, Ampang Hospital, Ministry of Health Malaysia.
This document provides information on hemophilia, including the objectives, coagulation factors, types and severity of hemophilia, clinical manifestations, complications, labs, treatment including factor replacement therapy and management in special situations. It discusses the basic concepts of hemophilia, how to approach cases, calculate factor requirements, lifestyle modifications, and management during situations like surgery, dental procedures, delivery, and menstruation in hemophiliacs.
This document discusses recent advances in the management of pediatric septic shock. It summarizes that evidence is shifting away from protocolized care to more individualized, physiology-based approaches. Specifically, the evidence no longer supports aggressive fluid resuscitation and liberal blood transfusions. Instead, more conservative fluid and transfusion strategies are favored. The document also reviews new evidence regarding use of biomarkers, inotrope selection, antibiotic timing, and steroid use in managing pediatric septic shock.
Hemophilia is a genetic bleeding disorder caused by low levels of certain clotting factors in the blood. There are two main types, hemophilia A caused by a factor VIII deficiency and hemophilia B caused by a factor IX deficiency. Symptoms include prolonged bleeding after injuries or surgery. Treatment involves replacing the missing clotting factor through transfusions or injections. Nurses play an important role in managing hemophilia through emotional support, applying pressure to bleeding sites, administering clotting factor treatments, restricting activity after bleeding, and educating patients.
1) She has a partial quantitative defect of von Willebrand factor as shown by her decreased vWF activity compared to her antigen level.
2) Her multimers were normal.
3) Her bleeding was responsive to DDAVP and factor replacement initially but her levels decreased over time, consistent with type 1 VWD.
This document presents a case study of a 10-year-old girl who presented with petechiae and was diagnosed with idiopathic thrombocytopenic purpura (ITP). Her clinical examination and lab tests confirmed the diagnosis of ITP. She was monitored as an outpatient without treatment. Over the next few years, her platelet count remained low and she received various treatments including IVIG and corticosteroids. Her condition was managed long-term with intermittent corticosteroid therapy and consideration of splenectomy. The document also provides background information on ITP including epidemiology, pathophysiology, diagnosis, treatment guidelines, and outcomes.
This document provides guidelines for preoperative patient preparation. It discusses gathering patient history and conducting examinations. It recommends specific investigations depending on the type and risk of surgery. It describes optimizing patient conditions by addressing medical issues like cardiovascular disease, respiratory disease, gastrointestinal disease, and other systems. It provides guidance on when to refer patients to specialists. The document aims to ensure patients are medically optimized and prepared for surgery and potential complications.
This document summarizes several coagulation disorders including haemophilia A, haemophilia B, von Willebrand disease, other hereditary coagulation factor deficiencies, and disseminated intravascular coagulation. It describes the clinical features, inheritance, laboratory findings, treatment, and management of each condition. Key points include that haemophilia A is the most common clotting factor deficiency, von Willebrand disease is the most common inherited bleeding disorder, and disseminated intravascular coagulation can be triggered by trauma, infection, cancer and other conditions.
Oral consideration and laboratory investigations of bleeding and clotting dis...kashmira483
This document provides information on bleeding and clotting disorders. It discusses the pathophysiology of hemostasis including the vascular, platelet, coagulation, and fibrinolytic phases. It describes different types of bleeding disorders like vessel wall disorders, platelet disorders, and coagulation disorders. Laboratory tests for identifying bleeding disorders are outlined. Oral manifestations and dental considerations for management are summarized. Local hemostatic agents and systemic agents for different bleeding disorders are also mentioned.
Guillain-Barré syndrome is an acute inflammatory polyneuropathy typically presenting with progressive ascending motor weakness. Intravenous immunoglobulin and plasma exchange are first-line treatments aimed at hastening recovery. While some vaccinations have a temporal association with Guillain-Barré syndrome, the causal relationship remains unclear and risks must be weighed against benefits of preventing severe infectious diseases. Careful supportive care including respiratory monitoring is important given potential respiratory complications.
A 72-year-old man presented with multiple fractures and splenic rupture following an MVA. He was now septic and bleeding from all wounds. Laboratory results showed a low hemoglobin and platelets, elevated PT and PTT, and low fibrinogen. Blood products including platelets, cryoprecipitate, and RBCs should be given to treat the coagulopathy and bleeding. NovoSeven may help control bleeding in surgical patients if platelet counts, PT, PTT and fibrinogen have been corrected first, as it requires these clotting factors to work effectively.
This case discusses a 7-year-old male who presented with a 6-day fever and convulsions. His symptoms did not improve with initial treatment. Extensive testing did not identify an infectious cause. He was diagnosed with autoimmune encephalitis based on his clinical presentation and improvement with immunotherapies. The document discusses how autoimmune causes now surpass viral infections as the most common cause of encephalitis in developing countries. It emphasizes the importance of considering and treating non-infectious autoimmune etiologies to achieve better neurological outcomes.
AAV vector-mediated gene therapy shows promise as a treatment for hemophilia B. Recent clinical trials using AAV5 vectors with liver-specific promoters demonstrated significantly improved patient symptoms and decreased need for factor IX injections by achieving clinically meaningful increases in FIX expression. While expression was sustained for up to 3 years in trials, limitations include the potential for immune responses, insufficient transgene expression, and uncertainty around long-term safety and cost-effectiveness. Overall, AAV5 vectors appear to be the most clinically successful approach thus far.
This document summarizes anticoagulants and their uses. It discusses the coagulation cascade and how anticoagulants work to prevent unwanted clotting. Several classes of anticoagulants are covered, including unfractionated and low molecular weight heparins, vitamin K antagonists like warfarin, and direct acting anticoagulants. Indications, dosages, monitoring, and adverse effects are provided for many of the discussed anticoagulants. The document also addresses perioperative management of anticoagulation and treatments for bleeding or over-anticoagulation.
This document discusses thrombotic disorders in pediatrics. It begins with an overview of hemostasis and coagulation. It then discusses the epidemiology, risk factors, clinical manifestations, investigations, and management of thrombotic disorders in children. A case scenario is presented of a child with diabetes admitted for DKA who develops leg swelling and tenderness. The document provides guidance on approaching such a case and considering deep vein thrombosis.
This document provides information on contrast-induced nephropathy (CIN) including its definition, importance of prevention, risk factors, and prevention strategies based on clinical trials. CIN is defined as a 25% increase or 0.5 mg/dL absolute increase in creatinine 2-5 days after contrast. Prevention is important as CIN can cause prolonged hospitalization, dialysis, and increased mortality. High risk groups include those with GFR <60 mL/min, especially diabetics. Prevention strategies shown to be effective include intravenous hydration before and after contrast, using low- or iso-osmolar contrast, and oral acetylcysteine. The document discusses various prevention strategies and concludes hydration and choosing
Webinar Series on COVID-19 vaccine: Jointly organized by Malaysian Society of Infection Control and Infectious Diseases (MyICID) & Institute for Clinical Research (ICR), NIH
Speaker: Dr. Veena Selvaratnam is a Haematologist, Ampang Hospital, Ministry of Health Malaysia.
This document provides information on hemophilia, including the objectives, coagulation factors, types and severity of hemophilia, clinical manifestations, complications, labs, treatment including factor replacement therapy and management in special situations. It discusses the basic concepts of hemophilia, how to approach cases, calculate factor requirements, lifestyle modifications, and management during situations like surgery, dental procedures, delivery, and menstruation in hemophiliacs.
This document discusses recent advances in the management of pediatric septic shock. It summarizes that evidence is shifting away from protocolized care to more individualized, physiology-based approaches. Specifically, the evidence no longer supports aggressive fluid resuscitation and liberal blood transfusions. Instead, more conservative fluid and transfusion strategies are favored. The document also reviews new evidence regarding use of biomarkers, inotrope selection, antibiotic timing, and steroid use in managing pediatric septic shock.
Hemophilia is a genetic bleeding disorder caused by low levels of certain clotting factors in the blood. There are two main types, hemophilia A caused by a factor VIII deficiency and hemophilia B caused by a factor IX deficiency. Symptoms include prolonged bleeding after injuries or surgery. Treatment involves replacing the missing clotting factor through transfusions or injections. Nurses play an important role in managing hemophilia through emotional support, applying pressure to bleeding sites, administering clotting factor treatments, restricting activity after bleeding, and educating patients.
1) She has a partial quantitative defect of von Willebrand factor as shown by her decreased vWF activity compared to her antigen level.
2) Her multimers were normal.
3) Her bleeding was responsive to DDAVP and factor replacement initially but her levels decreased over time, consistent with type 1 VWD.
This document presents a case study of a 10-year-old girl who presented with petechiae and was diagnosed with idiopathic thrombocytopenic purpura (ITP). Her clinical examination and lab tests confirmed the diagnosis of ITP. She was monitored as an outpatient without treatment. Over the next few years, her platelet count remained low and she received various treatments including IVIG and corticosteroids. Her condition was managed long-term with intermittent corticosteroid therapy and consideration of splenectomy. The document also provides background information on ITP including epidemiology, pathophysiology, diagnosis, treatment guidelines, and outcomes.
This document provides guidelines for preoperative patient preparation. It discusses gathering patient history and conducting examinations. It recommends specific investigations depending on the type and risk of surgery. It describes optimizing patient conditions by addressing medical issues like cardiovascular disease, respiratory disease, gastrointestinal disease, and other systems. It provides guidance on when to refer patients to specialists. The document aims to ensure patients are medically optimized and prepared for surgery and potential complications.
This document summarizes several coagulation disorders including haemophilia A, haemophilia B, von Willebrand disease, other hereditary coagulation factor deficiencies, and disseminated intravascular coagulation. It describes the clinical features, inheritance, laboratory findings, treatment, and management of each condition. Key points include that haemophilia A is the most common clotting factor deficiency, von Willebrand disease is the most common inherited bleeding disorder, and disseminated intravascular coagulation can be triggered by trauma, infection, cancer and other conditions.
Oral consideration and laboratory investigations of bleeding and clotting dis...kashmira483
This document provides information on bleeding and clotting disorders. It discusses the pathophysiology of hemostasis including the vascular, platelet, coagulation, and fibrinolytic phases. It describes different types of bleeding disorders like vessel wall disorders, platelet disorders, and coagulation disorders. Laboratory tests for identifying bleeding disorders are outlined. Oral manifestations and dental considerations for management are summarized. Local hemostatic agents and systemic agents for different bleeding disorders are also mentioned.
Guillain-Barré syndrome is an acute inflammatory polyneuropathy typically presenting with progressive ascending motor weakness. Intravenous immunoglobulin and plasma exchange are first-line treatments aimed at hastening recovery. While some vaccinations have a temporal association with Guillain-Barré syndrome, the causal relationship remains unclear and risks must be weighed against benefits of preventing severe infectious diseases. Careful supportive care including respiratory monitoring is important given potential respiratory complications.
A 72-year-old man presented with multiple fractures and splenic rupture following an MVA. He was now septic and bleeding from all wounds. Laboratory results showed a low hemoglobin and platelets, elevated PT and PTT, and low fibrinogen. Blood products including platelets, cryoprecipitate, and RBCs should be given to treat the coagulopathy and bleeding. NovoSeven may help control bleeding in surgical patients if platelet counts, PT, PTT and fibrinogen have been corrected first, as it requires these clotting factors to work effectively.
This case discusses a 7-year-old male who presented with a 6-day fever and convulsions. His symptoms did not improve with initial treatment. Extensive testing did not identify an infectious cause. He was diagnosed with autoimmune encephalitis based on his clinical presentation and improvement with immunotherapies. The document discusses how autoimmune causes now surpass viral infections as the most common cause of encephalitis in developing countries. It emphasizes the importance of considering and treating non-infectious autoimmune etiologies to achieve better neurological outcomes.
AAV vector-mediated gene therapy shows promise as a treatment for hemophilia B. Recent clinical trials using AAV5 vectors with liver-specific promoters demonstrated significantly improved patient symptoms and decreased need for factor IX injections by achieving clinically meaningful increases in FIX expression. While expression was sustained for up to 3 years in trials, limitations include the potential for immune responses, insufficient transgene expression, and uncertainty around long-term safety and cost-effectiveness. Overall, AAV5 vectors appear to be the most clinically successful approach thus far.
This document summarizes anticoagulants and their uses. It discusses the coagulation cascade and how anticoagulants work to prevent unwanted clotting. Several classes of anticoagulants are covered, including unfractionated and low molecular weight heparins, vitamin K antagonists like warfarin, and direct acting anticoagulants. Indications, dosages, monitoring, and adverse effects are provided for many of the discussed anticoagulants. The document also addresses perioperative management of anticoagulation and treatments for bleeding or over-anticoagulation.
This document discusses thrombotic disorders in pediatrics. It begins with an overview of hemostasis and coagulation. It then discusses the epidemiology, risk factors, clinical manifestations, investigations, and management of thrombotic disorders in children. A case scenario is presented of a child with diabetes admitted for DKA who develops leg swelling and tenderness. The document provides guidance on approaching such a case and considering deep vein thrombosis.
This document provides information on contrast-induced nephropathy (CIN) including its definition, importance of prevention, risk factors, and prevention strategies based on clinical trials. CIN is defined as a 25% increase or 0.5 mg/dL absolute increase in creatinine 2-5 days after contrast. Prevention is important as CIN can cause prolonged hospitalization, dialysis, and increased mortality. High risk groups include those with GFR <60 mL/min, especially diabetics. Prevention strategies shown to be effective include intravenous hydration before and after contrast, using low- or iso-osmolar contrast, and oral acetylcysteine. The document discusses various prevention strategies and concludes hydration and choosing
4. BLEEDING PHENOTYPE
• Do not bleed from superficial cuts or small vessels (e.g. nosebleeds)
• Delayed bleeding
• Deep muscle and joint bleeding
5. CURRENT TREATMENTS FOR HAEMOPHILIA
Factor replacement therapy:
1. Treat bleeds as they occur- “on demand” therapy
2. Treat bleeds before they occur- “prophylactic” therapy
6. DISADVANTAGES OF PROPHYLACTIC THERAPY
• Regular injections: Factor VII three times per week, Factor IX two times per week
• Need to start at early age
• Difficult in young children
• May need portacath
• Expensive (~£180,000 per year)
7. WHY GENE THERAPY?
• Continuous, 24/7, endogenous expression of protein at therapeutic levels
following a single gene transfer manoeuvre
• Single gene defect (deficiency of Factor VIII or IX gene)
• Therapeutic goal is modest- an increase in plasma Factor VIII or IX levels above
1% would be sufficient ameliorate the bleeding phenotype
8. GENE THERAPY FOR HAEMOPHILIA A
• Less success compared to haemophilia B due to the large size (7kb) of
Factor VIII
• Current approaches include:
The co-administration of two AAV vectors separately encoding the FVIII
heavy- and light chains
Use of AAV vectors encoding the B domain deleted Factor VIII (BDD-FVIII)
variant that is around 4.4 kb in size.
Use of lentiviral vectors to target haematopoietic stem cells.
11. STUDY DESIGN
• 10 men with severe haemophilia B each received a single dose of vector,
administered through a peripheral vein.
• 6 patients enrolled in an initial phase 1 dose-escalation trial, with 2 patients
each receiving a low, intermediate, or high dose.
• 4 additional patients later enrolled who received the high dose.
12. RESULTS
• Persistent stable FIX expression in all 10
subjects (1 to 6%) up to 4 years later.
• Of 7 patients receiving prophylactic treatment
before gene therapy, 4 were able to stop and
most others were able to increase the interval
between prophylactic infusions.
• Significant reduction in amount of factor IX
concentrate administered over the duration of
the study resulting in a financial savings of
more than £1.75 million based on 2014 prices.
13. CONCLUSION
• Gene therapy for the treatment of haemophilia patients may soon reach the
clinic.
• Gene therapy can be less invasive compared to protein replacement therapy
that requires multiple weekly injections.
• Offers the potential of a cure for haemophilia rather than just disease
management.
• More economical because the number of treatment events should be limited,
potentially to a single treatment.
14. REFERENCES
• Long-Term Safety and Efficacy of Factor IX Gene Therapy in Hemophilia B, N
Engl J Med 2014; 371:1994-2004
• Current status of haemophilia gene therapy
High, K H; Nathwani, A; Spencer, T; Lillicrap, D (2014)
Haemophilia : the official journal of the World Federation of Hemophilia vol.
20 Suppl 4 p. 43-9
• Gene therapy for haemophilia
Murphy, Samuel L; High, Katherine A (2008)
British journal of haematology vol. 140 (5) p. 479-87
• Gene therapy returns to centre stage
Naldini, Luigi (2015)
Nature Publishing Group,vol. 526 (7573) p. 351-360
Editor's Notes
Haem A: 1 in 10000
Haem B: 1 in 30000
Clinically indistinguishable, pattern of bleeding the same
Mild, moderate and severe forms of the disease.
Mild (6-40% factor levels)- Excessive bleeding only after major trauma or surgery
Moderate (2-5% factor levels)- Prolonged or excessive bleeding after minor trauma, rarely bleeds into joints
Severe (<1% factor levels)- spontaneous’ bleeds, joints and muscle, easy bruising, bleeding often delayed but prolonged, bleeding time normal
Clinically indistinguishable, pattern of bleeding the same
Extrinsic pathway: TF complexes with factor 7 converting it to 7a. TF and 7a convert F9 to 9a which converts F10 to 10a involving calcium and phospholipids. F10a converts F2 to thrombin which converts fibrinogen to fibrin. Once Thrombin is activated there is a feedback loop from thrombin that converts F5 to 5a and 8 into 8a. So the loss of factor 8 results in the loss of an important feedback loop.
Intrinisc: Xa interacts with tissue factor pathway inhibitor (TFPI) and turns off the extrinsic arm. However, by this point there is enough thrombin around to kick off coagulation along the intrinsic arm (with XI, IX and VIII) – and from there on out, the intrinsic arm supplies the rest of the fibrin.
Primary haemostasis is intact and sufficient for small vessels
Primary haemostasis works initially, Inadequate thrombin generation leads to Poor fibrin mesh, Increased susceptibility to fibrinolysis.
Tissues with low TF expression, More dependent on intrinsic pathway feedback
Haemophilia A
Less success due to large size of factor 8 which far exceeds the normal packaging capacity of AAV vectors.
Two AAV vectors
The co-administration of two AAV vectors separately encoding the FVIII heavy- and light chains separately encoding the FVIII heavy- and light chains whose intracellular association in vivo leads to the formation of a functional molecule. The alternative two AAV vector approach exploits the tendency of these vectors to form head to tail concatamers. Therefore, by splitting the expression cassette such that one AAV vector contains a promoter and part of the coding sequence, as well as a splice donor site, whereas the other AAV vector contains the splice acceptor site and the remaining coding sequence. Following in vivo head to tail concatemerization a functional transcript is created that is capable of expressing full-length FVIII protein
B domain deleted
Use of AAV vectors encoding the B domain deleted Factor XIII (BDD-FXIII) variant that is around 4.4 kb in size. This was made after it was found that the B-domain was found to be redundant for maintaining haemostasis.
Use of lentiviral vectors
They have a larger capacity so can carry the factor 8 gene. Although FVIII expression is generally considered to be liver specific, many studies have shown that different cell types are capable of synthesizing functional FVIII protein. Virtually any cell type with access to the bloodstream can be targeted for gene transfer. With respect to retroviral gene transfer, the haematopoietic stem cell (HSC) is efficiently modified and transplanted, and has, therefore, been a reasonable target for haemophilia A gene therapy.
Limitations of previous studies
Two early trials of hemophilia B gene therapy that used either intramuscular or liver-targeted delivery of AAV factor IX vectors based on AAV serotype 2, did not achieve stable expression of factor IX in the plasma of patients with severe hemophilia B. Many studies have shown that the intramuscular route is not an effective route of administartion
Liver toxicity was observed in patients in the liver-targeted study, an adverse event that may have been due to the activation of capsid specific T cells after the infusion of the high vector dose.
Efficient transduction with AAV is, however, limited by the need to convert its single-stranded (ss) genome into transcriptionally active double-stranded (ds) forms in target cells because of its dependence on host-cell–mediated DNA synthesis of the leading strand or annealing of complementary genomes derived from separate virions.
This vector has several features to combat these issues, including a liver-specific promoter, designed self-complementary in a tail-to-tail dimer to increase transcriptional activation and transduction efficiency, and codon optimization for sequences frequently found among highly expressed eukaryotic genes. Additionally, the AAV2 vector was pseudotyped with an AAV8-capsid to blunt immune responses, since AAV8 has lower sero prevalence in humans than AAV2 so there’ll be reduced production of neutralizing antibodies. The transgene also contains the liver specific promoter LP1, which limits the FIX gene expression to only hepatocytes.
Toxicity in study
The major vector-related adverse event was a dose-dependent, asymptomatic increase in the serum Alanine aminotransferase levels associated with a decline in factor IX levels, suggesting a loss of transduced hepatocytes. Expansion of the high dose cohort showed that this adverse event was common, occurring in four of the six patients. The increase in serum ALT levels occurred consistently at 7 to 10 weeks after gene transfer, thus defining the critical period of monitoring and pharmacologic intervention. The precise pathophysiological basis for the hepatocellular toxicity, which has also been observed with other serotypes and genomic configurations, remains unclear. Apart from the dose of vector, there were no identifiable clinical differences between the patients who had an increase in the ALT level and those who did not have an increase. In any case, prednisolone was effective in limiting the hepatocellular toxicity as well as preserving the expression of transgenic factor IX, especially when such treatment was initiated early.
As expected, long-lasting AAV8 capsid-specific humoral immunity developed in all the patients who underwent gene transfer. Although the increase in anti-AAV8 IgG levels did not have direct clinical consequences as far as we can tell, its persistence at high titers would preclude subsequent gene transfer with vector of the same serotype if transgene expression fell below therapeutic levels. However, preclinical studies suggest that it may be possible to achieve successful transduction in patients with preexisting antiAAV8 antibodies after the infusion of AAV vectors pseudotyped with alternative serotypes, such as AAV5, that have low cross-reactivity with antiAAV8 antibodies.