Current issues in prophylactic therapy for persons with hemophilia

Effectiveness of Prophylactic Coagulation Factor Replacement Therapy in Patients with Severe Hemophilia A in Taiwan - A Population-Based Study

Purpose

Taiwan launched reimbursement of prophylactic coagulation factor replacement therapy (CFRT) for patients with severe hemophilia type A (severe PWHA) in 2014. However, since then, the effectiveness of prophylactic CFRT in real-world practice has not been evaluated thoroughly. This study aimed to evaluate the effectiveness of prophylactic CFRT in severe PWHA cases on the outcome of bleeding risks.

Patients and Methods

We included male, severe PWHA cases from a nationwide, population-based database in Taiwan. Given that the database lacked details of the dosing regimen for prophylactic CFRT, we applied group-based trajectory modeling using the proportion of days covered (PDC) by CFRT from 2014 to 2015 in order to classify patients. A high PDC level corresponded to a greater proportion of time under CFRT, thus implying that the patient was probably receiving prophylactic therapy. We followed up patients from January 01, 2016 until occurrence of any bleeding events, death or December 31st 2017.

Results

We identified a total of 420 severe PWHA and classified them into high- (n = 88), medium- (n = 181) and low- (n = 151) PDC groups. The mean (±SD) PDC values of the three groups were 0.78 (±0.1), 0.40 (±0.1) and 0.12 (±0.1), respectively. Using Cox regression models with propensity score adjustment, we found patients with medium- (hazard ratio: 0.69; 95% CI: 0.56-0.89) or high-PDC (0.45; 0.36-0.68) under CFRT had reduced risks of any bleeding, compared to the low PDC group.

Conclusion

The findings demonstrated the effectiveness of prophylactic CFRT in the prevention of bleeding events in real-life severe PWHA.

Non-Human Glycans Can Regulate Anti-FVIII Antibody Formation in Mice

Recombinant Factor VIII (FVIII) products represent a life-saving intervention for patients with hemophilia A. However, patients can develop antibodies against FVIII that prevent FVIII function and directly increase morbidity and mortality. The development of anti-FVIII antibodies varies depending on the type of recombinant product employed, with previous studies suggesting that 2nd generation baby hamster kidney (BHK)-derived FVIII products display greater immunogenicity than 3rd generation Chinese hamster ovary (CHO)-derived FVIII. However, the underlying mechanisms responsible for these differences remain incompletely understood. Our results demonstrate that BHK cells express higher levels of the non-human carbohydrate a1-3 galactose (aGal) than CHO cells, suggesting that aGal incorporation onto FVIII may result in anti-aGal antibody recognition that could positively influence the development of anti-FVIII antibodies. Consistent with this, BHK-derived FVIII exhibits increased levels of aGal, which corresponds to increased reactivity with anti-aGal antibodies. Infusion of BHK-derived, but not CHO-derived, FVIII into aGal knock out mice, which spontaneously generate anti-aGal antibodies, results in significantly higher anti-FVIII antibody formation, suggesting that the increased levels of aGal on BHK-derived FVIII can influence immunogenicity. These results suggest that post-translational modifications of recombinant FVIII products with non-human carbohydrates may influence the development of anti-FVIII antibodies.

Marginal zone B cells are critical to factor VIII inhibitor formation in mice with hemophilia A

Although factor VIII (FVIII) replacement therapy can be lifesaving for patients with hemophilia A, neutralizing alloantibodies to FVIII, known as inhibitors, develop in a significant number of patients and actively block FVIII activity, making bleeding difficult to control and prevent. Although a variety of downstream immune factors likely regulate inhibitor formation, the identification and subsequent targeting of key initiators in inhibitor development may provide an attractive approach to prevent inhibitor formation before amplification of the FVIII immune response occurs. As the initial steps in FVIII inhibitor development remain incompletely understood, we sought to define early regulators of FVIII inhibitor formation. Our results demonstrate that FVIII localizes in the marginal sinus of the spleen of FVIII-deficient mice shortly after injection, with significant colocalization with marginal zone (MZ) B cells. FVIII not only colocalizes with MZ B cells, but specific removal of MZ B cells also completely prevented inhibitor development following FVIII infusion. Subsequent rechallenge with FVIII following MZ B-cell reconstitution resulted in a primary antibody response, demonstrating that MZ B-cell depletion did not result in FVIII tolerance. Although recipient exposure to the viral-like adjuvant polyinosinic:polycytidylic acid enhanced anti-FVIII antibody formation, MZ B-cell depletion continued to display similar effectiveness in preventing inhibitor formation following FVIII infusion in this inflammatory setting. These data strongly suggest that MZ B cells play a critical role in initiating FVIII inhibitor formation and suggest a potential strategy to prevent anti-FVIII alloantibody formation in patients with hemophilia A.

Neonatal hyperbilirubinemia: an unexpected cause

Hyperbilirubinemia is a common cause for newborn hospital admission. Although the cause of hyperbilirubinemia is usually benign and self-limited, there is always a large differential diagnosis. Atypical presenting signs and symptoms, such as significant anemia or bleeding, should encourage further evaluation for underlying disorders, such as inherited coagulation defects. This article describes the case of a 5-day-old infant who presented to the emergency department with hyperbilirubinemia, anemia, and ecchymoses from birth trauma. His hospital course is described, along with a review on the background, evaluation, management, and complications of hemophilia A.

Liposomal approach towards the development of a longer-acting factor VIII

Prevention of spontaneous bleeding in patients with severe haemophilia A usually requires therapeutic infusions every 2-3 days because of the short half-life of factor VIII (FVIII). Longer-acting FVIII products that require less frequent infusions would be beneficial and might obviate the need for central catheters in most patients. Liposomal formulation can enhance the efficacy of some therapeutic products. The incorporation of high-molecular weight polyethylene glycol (PEG) can extend the circulatory half-life of the liposome. These combined approaches led to the development of BAY 79-4,980, a PEG-containing liposomal version of Kogenate FS (rFVIII-FS). Results from preclinical models and early clinical trials have shown that BAY 79-4,980 prolongs the time to the next bleed. Further clinical evaluation of the efficacy and long-term safety of BAY 79-4,980 are planned.