Treatment switch to nonacog beta pegol factor IX in hemophilia B: A Canadian cost-consequence analysis based on real-world factor IX consumption and clinical outcomes.

Background: The Canadian Bleeding Disorders Registry (CBDR) is a source of real-world data for Canadian patients with hemophilia B. Nonacog beta pegol (N9-GP), an extended half-life (EHL) recombinant factor IX (FIX) concentrate, was awarded a Canadian Blood Services contract in 2018 and subsequently made available across Canada (except Québec) to adult patients. For most patients already on another EHL FIX treatment, a switch to N9-GP occurred. Objectives: This study estimates the impact on treatment costs of a switch from a prior FIX to N9-GP based on annualized bleed rates and FIX consumption volumes before and after N9-GP switch from the CBDR. Methods: Real-world data from the CBDR for total FIX consumption and annualized bleed rates were used to inform a deterministic 1-year cost-consequence model. The model considered that the EHL to N9-GP switches were from eftrenonacog alfa and the standard half-life switches were from nonacog alfa. Because FIX prices are confidential in Canada, the model assumed cost parity for annual prophylaxis with each FIX based on the product monograph recommended dosing regimen to calculate an estimated price per international unit for each product. Results: The switch to N9-GP resulted in improvements in real-world annualized bleed rates and therefore reductions in annual breakthrough bleed treatment costs. Switching to N9-GP also resulted in reduced real-world annual FIX consumption for prophylaxis. Overall, annual treatment costs were 9.4% and 10.5% lower after the switch to N9-GP from nonacog alfa and eftrenonacog alfa, respectively. Conclusion: N9-GP improves clinical outcomes and may be cost-saving vs nonacog alfa and eftrenonacog alfa.

Switching to nonacog beta pegol in hemophilia B: Outcomes from a Canadian real-world, multicenter, retrospective study.

Background: The Canadian Bleeding Disorders Registry (CBDR) captures data from 24 hemophilia treatment centers and patients directly. Nonacog beta pegol (N9-GP) was approved in Canada in 2018. Objectives: To assess treatment outcomes following switching to N9-GP in a real-world setting. Methods: CBDR data for Canadian male patients (aged 7-72 years) with hemophilia B receiving prophylactic N9-GP for ≥6 months as of March 31, 2021, were included. To allow comparison with the previously used products, only patients for whom data were available in the CBDR for at least 6 months before the switch to N9-GP were included in this retrospective analysis. Results: Forty-two patients were included in the analysis (total observation period: 148.0 patient-years). The distribution of disease severity was 62% severe, 36% moderate, 2% mild, with 62% of patients previously receiving recombinant factor IX-Fc-fusion protein (rFIXFc) and 38% previously receiving standard half-life (SHL) recombinant factor IX (rFIX). During a median follow-up period of 2.3 years on N9-GP prophylaxis, 232 bleeds were reported in 30 patients, 29% of patients reported zero bleeds. The median overall annualized bleeding rate on N9-GP was 0.73 for patients switching from rFIXFc (previously 1.44) and 2.10 for patients switching from SHL rFIX (previously 6.06). Median total annualized factor consumption (IU/kg) was lower with N9-GP than with previous SHL rFIX (2152 vs 3018) and previous rFIXFc (1766 vs 2278). Conclusions: Results from this first real-world study of N9-GP in patients with hemophilia B suggest optimal bleeding control with low factor consumption after switching to N9-GP, irrespective of the previous product.

Regulatory serine residues mediate phosphorylation-dependent and phosphorylation-independent activation of interferon regulatory factor 7.

Interferon regulatory factor (IRF)7 is a key transcription factor required for establishment of antiviral resistance. In response to infection, IRF7 is activated by phosphorylation through the action of the non-canonical IkappaB kinases, IkappaB kinase-epsilon and TANK-binding kinase 1. Activation leads to nuclear retention, DNA binding, and derepression of transactivation ability. Clusters of serine residues located in the carboxyl-terminal regulatory domain of IRF7 are putative targets of virus-activated kinases. However, the exact sites of phosphorylation have not yet been established. Here, we report a comprehensive structure-activity examination of potential IRF7 phosphorylation sites through analysis of mutant proteins in which specific serine residues were altered to alanine or aspartate. Phosphorylation patterns of these mutants were analyzed by two-dimensional gel electrophoresis, and their transcriptional activity was monitored by reporter assays. Essential phosphorylation events were mapped to amino acids 437-438 and a redundant set of sites at either amino acids 429-431 or 441. IRF7 recovered from infected cells was heterogeneously phosphorylated at these sites, and greater phosphorylation correlated with increased transactivation. Interestingly, a distinct serine cluster conserved in the related protein IRF3 was also essential for IRF7 activation and distal phosphorylation. However, the essential role of this motif did not appear to be fulfilled by phosphorylation. Rather, these serine residues and an adjacent leucine were required for phosphorylation at distal sites and may determine a conformational element required for function.

Acetylation of interferon regulatory factor-7 by p300/CREB-binding protein (CBP)-associated factor (PCAF) impairs its DNA binding.

Interferon regulatory factor 7 (IRF7) is an interferon-inducible transcription factor required for induction of delayed early interferon alpha genes and the onset of a potent antiviral state. After induction of IRF7 by autocrine interferon, latent IRF7 is activated by virus-induced phosphorylation on serine residues within the C-terminal regulatory domain. Although it is likely that IRF7 is subjected to a cascade of events responsible for regulating its biological activity, to date no mechanism other than phosphorylation has been reported to modulate IRF7 activity. Here, we report that IRF7 is acetylated in vivo by the histone acetyltransferases p300/CBP-associated factor (PCAF) and GCN5. The single lysine residue target for acetylation, lysine 92, is located in the DNA-binding domain and is conserved throughout the entire IRF family. Mutation of lysine 92 resulted in complete abolition of DNA binding ability. However, a mutant that cannot be acetylated by PCAF due to a change in the surrounding amino acid context of lysine 92 showed increased DNA binding and activity compared with wild type IRF7. Conversely, we showed that acetylated IRF7 displayed impaired DNA binding capability and that over-expression of PCAF led to decreased IRF7 activity. Together, our results strongly suggest that acetylation of lysine 92 negatively modulates IRF7 DNA binding.