Haemophilia B - Diagnostic Insights, Genetic Aspects and Clinical Outcomes

Haemophilia B (HB) is a rare inherited bleeding disorder caused by the deficiency of coagulation factor IX (FIX). The major clinical issues are bleedings, often targeting the joints, and the development of neutralising antibodies, i.e. inhibitors, to the FIX replacement therapy. Historically HB has been seen as identical to the more common haemophilia A (HA), i.e. deficiency of coagulation factor VIII (FVIII), but important differences between the two diseases exist. As a result of the rarity of HB, much of our knowledge of HB has been extrapolated from what is known about HA. To improve the care for persons with HB (PwHB), studies focusing on HB are of importance. The aim of this thesis was to characterise HB regarding its diagnostic challenges, treatment, clinical outcomes, and the quality of life of PwHB, and to compare some of these aspects to those of HA.Paper I describes the comparison of the one-stage and the chromogenic assays in measuring the FIX activity level. In HA, a discrepancy between the two methods in measuring FVIII has been reported in approximately one-third of persons with non-severe HA; however, this has not previously been evaluated in HB. We found that 25% of persons with non-severe HB had discrepant results between the two methods, with higher values recorded when the chromogenic method was used. All but one of these persons had the same FIX gene (F9) mutated amino acid. This was the first study to show that assay discrepancy occurs in HB and we concluded that both the one-stage and the chromogenic assays are needed for the correct diagnosis and classification of HB.Papers II-IV describe a cohort of 79 persons with severe HB from the Nordic countries, and 79 matched controls with HA. In Paper II, joint assessment using ultrasound and haemophilia joint health score (HJHS) was conducted and showed that despite the fact that 95% of PwHB were treated with prophylaxis, 37% reported joint bleedings during the prior year. Ultrasound scores were overall low and HJHS scores were significantly lower among PwHB compared with persons with HA (PwHA), indicative of a milder arthropathy in patients with severe HB than in PwHA. Treatment adherence was evaluated using Validated Haemophilia Regimen Treatment Adherence Scale (VERITAS) questionnaires and showed overall good adherence.Paper III presents information on F9 variants, inhibitors, and immune tolerance induction (ITI) therapy in PwHB. We found a high proportion of severe F9 gene defects and a relatively high prevalence of inhibitors of 15%. Of inhibitor patients, 92% had experienced allergic manifestations and 25% nephrotic syndrome. ITI success was independent of the F9 variant and was attained despite allergic reactions and previous ITI failures. Immunosuppression included in the ITI regimen showed a high beneficial rate and may enhance the chances of success. Analyses of noninhibitory anti-FIX antibodies (NNAs) with a multi analyte profiling-based fluorescence immunoassay (xFLI) and an enzyme-linked immunosorbent assay (ELISA) were conducted, but no NNAs were identified. In Paper IV, health-related quality of life (HRQoL) was assessed using the EQ 5D 3L questionnaire and showed a high frequency of pain, mobility problems and anxiety/depression in PwHB, indicating that areas of insufficient care exist. No significant differences in HRQoL between PwHB and PwHA were found, and impaired joint health assessed by the HJHS was found to have a significant negative impact on HRQoL

Treatment outcomes in persons with severe haemophilia B in the Nordic region : The B-NORD study

Introduction Data on outcome in persons with haemophilia B (PwHB) are limited and mainly extrapolated from studies of haemophilia A (HA). Aim To characterize treatment outcomes in persons with severe HB in the Nordic region, with a focus on joint health, compared with matched controls with HA. Methods PwHB attending haemophilia centres in Denmark, Finland, Norway and Sweden were enrolled and matched with controls with HA. Joint assessment using Haemophilia Joint Health Score (HJHS) and ultrasound according to Haemophilia Early Arthropathy Detection protocol (HEAD-US) was conducted. Adherence was evaluated using the Validated Haemophilia Regimen Treatment Adherence Scale (VERITAS). Results Seventy-nine males with HB, with median age of 30 years (range 1-75), were enrolled. Eleven patients (14%) had a history of or current inhibitor. Twenty-nine PwHB (37%) reported joint bleeds during the prior year, and 35% had previously undergone joint surgery. Ninety-five per cent were on prophylaxis, and 70% used recombinant concentrates, with a median factor consumption of 3,900 IU/kg/year for standard half-life products. Only two patients had a VERITAS score corresponding to 'non-adherence'. Joint health, assessed with HJHS, showed a significant lower score among PwHB compared with HA controls, explained by a difference in the 18-49 age group, without observed differences in older or younger subgroups. The HEAD-US scores were overall low. Conclusion The Nordic cohort of PwHB is well treated by prophylaxis, but the goal of zero bleeds for all is not reached. Our findings suggest that patients with severe HB suffer from a milder arthropathy than patients with severe HA.Peer reviewe

Factor IX antibodies and tolerance in hemophilia B in the Nordic countries - The impact of F9 variants and complications

Introduction: The development of inhibitory antibodies (inhibitors) in persons with hemophilia B (PwHB) causes significant morbidity. Data on the impact of the F9 variant and immune tolerance induction (ITI) outcome are limited.The aim of this study was to investigate the presence of neutralizing and non-neutralizing antibodies (NNA) in severe hemophilia B (HB) and to evaluate ITI outcome and complications in relation to the pathogenic F9 variant.Materials and methods: Persons with severe HB in the Nordic countries were enrolled and information on F9 variants, inhibitors, ITI and complications were collected. Analyses of anti-FIX antibodies with a fluorescence -immunoassay (xFLI) and an ELISA method were conducted.Results: Seventy-nine PwHB were enrolled. Null variants were seen in 33 (42 %) PwHB and 12 (15 %) had a current or former inhibitor. Eleven (92 %) of the inhibitor patients had experienced allergic manifestations and three (25 %) nephrotic syndrome. Of 10 PwHB with at least one ITI attempt, eight (80 %) were considered tolerant at enrolment. Immunosuppression was included in seven of eight successful or partially successful at-tempts. Five PwHB had at least one ITI failure before a successful or partially successful ITI. No NNA could be identified.Conclusion: A high proportion of severe F9 gene defects among persons with severe HB in the Nordic countries may explain the observed relatively high prevalence of inhibitors. ITI success was independent of the F9 variant and attained despite allergic manifestations and previous ITI failures. Inclusion of immunosuppression tenta-tively enhances the chances of ITI success. No NNA were observed.Peer reviewe

Synthesis of Novel Inhibitors of IdeS, a Bacterial Cysteine Protease Including Studies of Stereoselective Reductive Aminations

Abstract The cysteine protease IdeS is an IgG degrading enzyme secreted by the bacterium Streptococcus pyogenes to evade the human immune system. In this thesis several inhibitors of IdeS have been synthesized and evaluated. Such inhibitors should be highly useful when elucidating the detailed mechanism of IdeS action. They might also have a potential as treatment of acute and severe infections caused by the bacteria. Further, IdeS has a therapeutic application of its own due to the proteolytic ability and an IdeS inhibitor might contribute during the development. Only irreversible, unselective inhibitors of IdeS were known five years ago. In this thesis, three strategies with the aim to synthesize and identify more inhibitors have been undertaken. Focus was first set on compounds with a substructure resembling the known inhibitors but with reversible warheads, i.e. nitrile, azide and aldehyde functions. The aldehyde derivatives were found to provide the first reversible inhibitors of IdeS. Then, to avoid covalent interactions and obtain more selective inhibitors, a substrate based strategy was undertaken. A 3-aminopiperidine fragment was used as replacement of either of the two residues adjacent to the scissile bond in IgG. Such fragments can be synthesized from N-protected 3-aminopiperidone and amino acid esters in reductive aminations in which a stereogenic center is formed. A series of di-, tri- and tetrapeptide analogues, together with eight peptides covering the cleavage site of IgG, were screened for their capacity to inhibit the cysteine proteases IdeS, SpeB and papain. Several analogues showed inhibition capacity, two compounds showed also high selectivity for IdeS. In contrast, none of the tested peptides showed any inhibition. Computational docking studies indicate that the identified IdeS peptide analogues and the non-active peptides do not share the same binding site in IdeS. Probably, the piperidine moiety hinders the inhibitor to enter the catalytic site. A more detailed study of the stereoselectivity in the reductive aminations affording the 3-aminopiperidine fragment showed that a large protecting group (trityl) together with a large reducing agent (NaBH(O-2- ethylhexanoyl)3) gave the highest diastereomeric ratio. The highest ratio obtained was 21:79 when Lproline methyl ester was used. The newly formed stereogenic center had the R-configuration, determined by chemical correlation. Computer based conformational analysis combined with Boltzmann distribution calculations implies an axial attack by the reducing reagent on the intermediary imine. To improve the potency of the two identified di- and tripeptide analogues synthetic routes to conformationally restricted N-containing bicyclic derivatives was undertaken in a third strategy. Five compounds with different bicyclic scaffolds were screened for their inhibition capacity towards IdeS and papain. One of the compounds was able to inhibit the first step of proteolytic cleavage of IgG by IdeS, a process usually completed in seconds

Quantitative Structure-Activity Relationship of Peptides Binding to the Class II Major Histocompatibility Complex Molecule A(q) Associated with Autoimmune Arthritis.

Presentation of (glyco)peptides by the class II major histocompatibility complex molecule Aq to T cells plays a central role in collagen-induced arthritis, an animal model for the autoimmune disease rheumatoid arthritis. A peptide library was designed using statistical molecular design in amino acid space in which five positions in the minimal mouse collagen type II binding epitope CII260-267 were varied. A substantially reduced peptide library of 24 peptides with diverse and representative molecular characteristics was selected, synthesized, and evaluated for the binding strength to Aq. A multivariate QSAR model was established by correlating calculated descriptors, compressed to its principle properties, with the binding data using partial least-square regression. The model was successfully validated by an external test set. Interpretation of the model provided a molecular property binding motif for peptides interacting with Aq. The information may be useful in future research directed toward new treatments of rheumatoid arthritis

3-Aminopiperidine-Based Peptide Analogues as the First Selective Noncovalent Inhibitors of the Bacterial Cysteine Protease IdeS

A series of eight peptides corresponding to the amino acid sequence of the hinge region of IgG and 17 newly synthesized peptide analogues containing a piperidine moiety as a replacement of a glycine residue were tested as potential inhibitors of the bacterial IgG degrading enzyme of Streptococcus pyogenes, IdeS. None of the peptides showed any inhibitory activity of IdeS, but several piperidine-based analogues were identified as inhibitors. Two different analysis methods were used: an SDS-PAGE based assay to detect IgG cleavage products and a surface plasmon resonance spectroscopy based assay to quantify the degree of inhibition. To investigate the selectivity of the inhibitors for IdeS, all compounds were screened against two other related cysteine proteases (SpeB and papain). The selectivity results show that larger analogues that are active inhibitors of IdeS are even more potent as inhibitors of papain, whereas smaller analogues that are active inhibitors of IdeS inhibit neither SpeB nor papain. Two compounds were identified that exhibit high selectivity against IdeS and will be used for further studies

No difference in quality of life between persons with severe haemophilia A and B

IntroductionGood health-related quality of life (HRQoL) is an important goal in the treatment of persons with haemophilia B (PwHB). Studies focusing on this population are limited, however, and data are insufficient. AimTo assess the HRQoL in PwHB and to compare this to data on persons with haemophilia A (PwHA), as well as to evaluate the impact of joint health on HRQoL and to identify areas of insufficient care. MethodsThe B-NORD study enrolled persons with severe haemophilia B and matched controls with haemophilia A. HRQoL was assessed using the EQ-5D-3L questionnaire and joint health using Haemophilia Joint Health Score 2.1 (HJHS). ResultsThe EQ-5D-3L was completed by 63 PwHB and 63 PwHA. Mobility problems were reported by 46% of PwHB and 44% of PwHA, pain/discomfort by 62% and 56%, and anxiety/depression by 33% and 17%, respectively. No significant difference was observed between PwHA and PwHB in EQ-5D profiles, level sum score, EQ-5D index (PwHB mean .80, PwHA mean .83, p = .24), or EQ VAS score (PwHB: mean 70, PwHA: mean 77, p = .061). Linear regression adjusted for age demonstrated that an increase in HJHS score was associated with a significant decrease in both EQ-5D index (B -.003, R-2 .22) and EQ VAS score (B -.37, R-2 .17). ConclusionDespite the majority of patients being treated with prophylaxis, impaired HRQoL was reported in both PwHB and PwHA. No differences in HRQoL were found between the two groups. Impaired joint health had a significant negative impact on HRQoL.Peer reviewe