PROLONG-9FP clinical development program – phase I results of recombinant fusion protein linking coagulation factor IX with recombinant albumin (rIX-FP)

Expert opinion paper on the treatment of hemophilia B with albutrepenonacog alfa

Introduction: Current guidelines recommend prophylactic treatment of hemophilia B with the missing coagulation factor IX, either with standard half-life or extended half-life products. Extended half-life products have half-lives three to six times longer than the former, allowing a reduction in the number of weekly injections and therefore, potentially impacting on treatment adherence and quality of life. Albutrepenonacog alfa is an extended half-life fusion protein of coagulation factor IX with recombinant human albumin, indicated for both on-demand and prophylactic treatment for bleeding in patients with hemophilia B of all ages.Areas covered: The authors review the clinical and pharmacokinetic characteristics of albutrepenonacog alfa, as well as the available information regarding trough levels and real-world evidence. Given the availability of other factor IX products in the market, indirect comparisons of clinical and pharmacokinetic characteristics are presented.Expert opinion: The authors exhibit their expert opinion on which patient profiles are candidates for prophylactic treatment with albutrepenonacog alfa, and on the management of patients in terms of dosing, regimens of administration and protocols for switching the treatment.

Albumin-based drug delivery using cysteine 34 chemical conjugates – important considerations and requirements

The long blood circulation time of albumin has been clinically utilized as a half-life extension technology for improved drug performance. The availability of one free thiol for site-selective chemical conjugation offers an alternative approach to current genetic fusion and association-based products. This special report highlights important factors for successful conjugation that allows the reader to design and evaluate next-generation albumin conjugates. Albumin type, available conjugation chemistries, linker length, animal models and influence of conjugation on albumin pharmacokinetics and drug activity are discussed.

Population pharmacokinetics of a new long-acting recombinant coagulation factor IX albumin fusion protein for patients with severe hemophilia B

Essentials The new recombinant factor IX (FIX) albumin fusion protein (rIX-FP) has a prolonged half-life. A population pharmacokinetic (PK) model was based on FIX activity levels of hemophilia B patients. The model was used to simulate different dosing scenarios of rIX-FP to help guide dosing. The population PK model supported prolonged dosing of rIX-FP with intervals of up to 2 weeks. Click to hear Prof.Makris's presentation on new treatments in hemophilia SUMMARY: Background The recombinant fusion protein linking recombinant coagulation factor IX with recombinant albumin (rIX-FP; Idelvion® ) exhibits a longer half-life than plasma-derived factor IX (FIX) and the commercially available recombinant FIX products. Objectives (i) Characterize the population pharmacokinetics (PK) of rIX-FP in hemophilia B patients, (ii) identify covariates that are potential determinants of rIX-FP PK variability and (iii) simulate different dosing scenarios of rIX-FP following single and steady-state dosing. Patients/Methods A population PK model was developed based on FIX activity levels of 104 patients who had received treatment with rIX-FP. Patients were aged 1-65 years with FIX activity ≤ 2 IU dL-1 . PK sampling was performed for up to 14 days (336 h). Results Simulation of a single intravenous infusion of rIX-FP (25-75 IU kg-1 ) predicted that the median trough exogenous FIX activity levels would remain > 5 IU dL-1 for up to 16 days in adolescents/adults aged ≥ 12 years, up to 12 days in children aged 6 to < 12 years, and up to 9.5 days in children aged < 6 years. For steady-state dosing, the median trough exogenous FIX activity levels were maintained at > 5 IU dL-1 for the duration of the dosing interval for the 25, 35 and 40 IU kg-1 weekly regimens and for 75 IU kg-1 every 14 days in adolescents/adults, and for the 35 and 40 IU kg-1 weekly regimens in children. Conclusion The population PK model developed here correlates well with observed clinical data and supports prolonged dosing of rIX-FP with intervals of up to 2 weeks.

New developments in the management of moderate-to-severe hemophilia B

Hemophilia B is an X-linked genetic deficiency of coagulation factor IX (FIX) activity associated with recurrent deep tissue and joint bleeding that may lead to long-term disability. FIX replacement therapy using plasma-derived protein or recombinant protein has significantly reduced bleeding and disability from hemophilia B, particularly when used in a prophylactic fashion. Although modern factor replacement has excellent efficacy and safety, barriers to the broader use of prophylaxis remain, including the need for intravenous (IV) access, frequent dosing, variability in individual pharmacokinetics, and cost. To overcome the requirement for frequent factor dosing, novel forms of recombinant FIX have been developed that possess extended terminal half-lives. Two of these products (FIXFc and rIX-FP) represent fusion proteins with the immunoglobulin G1 (IgG1) Fc domain and albumin, respectively, resulting in proteins that are recycled in vivo by the neonatal Fc receptor. The third product has undergone site-specific PEGylation on the activation peptide of FIX, similarly resulting in a long-lived FIX form. Clinical trials in previously treated hemophilia B patients have demonstrated excellent efficacy and confirmed less-frequent dosing requirements for the extended half-life forms. However, gaps in knowledge remain with regard to the risk of inhibitor formation and allergic reactions in previously untreated patient populations, safety in elderly patients with hemophilia, effects on in vivo FIX distribution, and cost-effectiveness. Additional strategies designed to rebalance hemostasis in hemophilia patients include monoclonal-antibody-mediated inhibition of tissue factor pathway inhibitor activity and siRNA-mediated reduction in antithrombin expression by the liver. Both of these approaches are long acting and potentially involve subcutaneous administration of the drug. In this review, we will discuss the biology of FIX, the evolution of FIX replacement therapy, the emerging FIX products possessing extended half-lives, and novel “rebalancing” approaches to hemophilia therapy.

The long and short of it: using the new factor products

Hemophilia A (HA) and B (HB) are classified as mild (>5%-40%) moderate (1%-5%) and severe (<1%) disease based on plasma factor activity. Severity of bleeding is commensurate with baseline factor levels in general; however, heterogeneity of bleeding in patients is well described. Recurrent bleeding with painful and disabling musculoskeletal complications is the largest source of morbidity for persons with hemophilia (PWH) but treatment advances through the years has led to improved outcomes. In the early 20th century, only whole blood and fresh frozen plasma (FFP) was available to treat bleeding episodes. In 1959, cryoprecipitate was discovered and became an option for treatment of HA in 1965. In the 1970s plasma fractionation led to the first standard half-life (SHL) concentrates. These products ushered in the use prophylactic therapy to prevent bleeding episodes. However, viral contamination slowed the use of prophylaxis until the 1980s when viral attenuation steps increased the safety of plasma concentrates. In the 1990s recombinant concentrates were developed and prophylactic therapy is increasing widely yet not yet universally used. However even with frequent SHL concentrate infusions outcomes are not optimal as PWH spend the majority of time with factor levels below the normal range and are at increased risk for bleeding. In 2014, the first extended half-life (EHL) products were approved for use and have begun to change the landscape of hemophilia care. Challenges of EHL implementation include patient selection, product selection, dose and schedule of infusions, monitoring for safety, efficacy and outcomes, and managing economic aspects of care.

Emerging and future therapies for hemophilia

The evolution of care in hemophilia is a remarkable story. Over the last 60 years, advances in protein purification, protein chemistry, donor screening, viral inactivation, gene sequencing, gene cloning, and recombinant protein production have dramatically enhanced the treatment and lives of patients with hemophilia. Recent efforts have produced enhanced half-life (EHL) clotting factors to better support prophylaxis and decrease the frequency of infusions. Medical needs remain in the areas of alternate modes of administration to decrease the need for venous access, better treatment, and prophylaxis for patients who form antibodies to clotting factors, and ultimately a cure of the underlying genetic defect. In this brief review, the authors summarize data on EHL clotting factors, introduce agents whose mode of action is not clotting factor replacement, and list current gene therapy efforts.

Longer-acting clotting factor concentrates for hemophilia

Hemophilia, when severe, leads to spontaneous life-threatening bleeding episodes. Current therapy requires frequent intravenous infusions. Most patients must limit their physical activities to avoid bleeding when the factor activity levels are below normal. In 2014, new therapeutic factor VIII and IX products were approved in Canada and the U.S. Over the next couple of years, other new factor products will likely be approved. These new factors have been engineered to have improved pharmacokinetic properties, including extended half-life in circulation, thus providing major therapeutic advances for patients with hemophilia. In the completed clinical trials, over 700 patients have successfully used these longer acting products regularly for more than one year. These promising new therapies should allow patients with hemophilia to use fewer infusions to prevent spontaneous bleeding or to treat bleeding episodes, and to provide appropriate clotting factor levels for different physical activities.

Nonacog gamma, a novel recombinant factor IX with low factor IXa content for treatment and prophylaxis of bleeding episodes

Nonacog gamma is a new recombinant factor IX to treat factor IX deficiency. It is indicated for control of bleeding episodes, perioperative management and routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and children with hemophilia B. Nonacog gamma was first approved in the USA in June 2013 under the trade name RIXUBIS followed by market approvals in Australia and the EU in 2014, and marketing authorization decision is pending in Japan. Nonacog gamma is derived from a recombinant Chinese hamster ovary cell line using a state of the art biotechnological manufacturing process. Recombinant factor IX is produced by Baxter's protein-free fermentation technology, which was first developed for ADVATE. The product is purified and formulated in the absence of any human or animal-derived protein. Nonacog gamma was characterized both in comprehensive in vitro and in vivo non-clinical studies as well as in an extensive clinical trial program.

Lasting power of new clotting proteins

Hemophilia is a genetic disease caused by a deficiency of one of the coagulation proteins. The term usually refers to either hemophilia A, factor VIII (FVIII), with an incidence of ∼1 in 5000 male births, or hemophilia B, factor IX (FIX), with an incidence of ∼1 in 30 000 male births. When severe, the disease leads to spontaneous life-threatening bleeding episodes. Current therapy requires frequent intravenous infusions of therapeutic factor concentrates. Most patients administer the infusions at home every few days and must limit their physical activities to avoid bleeding when the factor activity levels are below normal. In March 2014, a new therapeutic FIX preparation was approved for clinical use in Canada and the United States and, in June 2014, a new FVIII preparation was approved for clinical use in the United States. Over the next couple of years, other new factor products for FIX, FVIIa, and FVIII, which are currently in late stages of clinical trials, will likely also be approved. These new factors have been engineered to extend their half-life in circulation, thus providing major therapeutic advances for patients with hemophilia primarily by allowing treatment with fewer infusions per month. In the clinical trials so far, >500 patients have successfully used these extended half-life products regularly for >1 year to prevent spontaneous bleeding, to treat successfully any bleeding episodes, and to provide effective coagulation for major surgery. Essentially all infusions were well tolerated and effective. These promising new therapies should allow patients to use fewer infusions to maintain appropriate clotting factor activity levels in all clinical settings.

Half-life extension technologies for haemostatic agents

The use of plasma-derived and recombinant coagulation factors for the treatment of haemophilia A and B is well established and permits patients to live a relatively normal life. In order to improve treatment options, several products are in development, which have a prolonged duration of action, thus enabling less frequent prophylactic dosing and aiming to reduce the burden of treatment. Several innovative approaches are being pursued to extend the half-life of factor VIIa, factor VIII and factor IX, utilising technologies such as Fc fusion, recombinant albumin fusion and addition of polyethyleneglycol (PEG) (PEGylation). These methods prolong the time in the circulation by reducing degradation and elimination. This review summarises the technologies and products in development and their stages of development, and also discusses their pros and cons.

Molecular approaches for improved clotting factors for hemophilia

Hemophilia is caused by a functional deficiency of one of the coagulation proteins. Therapy for no other group of genetic diseases has seen the progress that has been made for hemophilia over the past 40 years, from a life expectancy in 1970 of ∼20 years for a boy born with severe hemophilia to essentially a normal life expectancy in 2013 with current prophylaxis therapy. However, these therapies are expensive and require IV infusions 3 to 4 times each week. These are exciting times for hemophilia because several new technologies that promise extended half-lives for factor products, with potential for improvements in quality of life for persons with hemophilia, are in late-phase clinical development.

Molecular approaches for improved clotting factors for hemophilia

Hemophilia is caused by a functional deficiency of one of the coagulation proteins. Therapy for no other group of genetic diseases has seen the progress that has been made for hemophilia over the past 40 years, from a life expectancy in 1970 of ∼20 years for a boy born with severe hemophilia to essentially a normal life expectancy in 2013 with current prophylaxis therapy. However, these therapies are expensive and require IV infusions 3 to 4 times each week. These are exciting times for hemophilia because several new technologies that promise extended half-lives for factor products, with potential for improvements in quality of life for persons with hemophilia, are in late-phase clinical development.