Factor VIII and Factor IX
6 August 2005
16:00 to 19:30
Ballroom 2
Sydney Convention and Exhibition Centre
Chairman: K. Mertens, The Netherlands
Co-Chairmen: J. C. Gill, USA; C. Lee, UK; J. Oldenburg, Germany;
JM Saint-Remy, Belgium; A. Srivastava, India; HM van den Berg, The Netherlands
The Chairman opened the Subcommittee meeting at 16.00 for an audience of approximately 200 attendants. He explained that, due to the more condensed format of this year’s meeting, not the entire portfolio of Subcommittee activities could be addressed this year. In particular the issue of novel FVIII assays could not be included this time, but the issue will return on the program in 2006.
Completed Reports and Recommendations
In the past year no SSC recommendations have been published. Standardisation activities performed within the Subcommittee have resulted in two full papers in Journal of Thrombosis and Haemostasis:
Section 1: Factor VIII: Clinical Issues: Co-Chairs: C. Lee and H.M. van den Berg
Global PTP inhibitor surveillance study: follow-up: D.M.DiMichele
The international need for an international PTP surveillance effort was established at the FVIII/IX Subcommittee in 2003, and the project ratified by the Subcommittee in 2004. Donna DiMichele presented a progress report on this ongoing project. In an initial effort to develop a consensus data collection tool, a questionnaire was sent in 10/04 to countries known to have national PTP inhibitor databases (UK, France and Germany) to ascertain both the nature and the scope of data collected. Similar information was also solicited from Italy and Canada in 07/05. As anticipated, data presented from the responses received to date indicate variability in both the nature and scope of ongoing or planned national data collection. A working party currently represented by the US , UK , France , Germany and Italy , but seeking all other interested national participants (contact Donna DiMichele at dmdimich@med.cornell.edu ), will begin working on a the development of a consensus minimum international data set to satisfy international regulatory requirements. A funded US pilot effort through the CDC to prospectively collect PUP and PTP inhibitor prevalence/incidence data, is in the planning stages and will incorporate the international consensus guidelines for data collection developed through this working party. A progress report is planned for 2006.
M eta-analysis of PUP studies of recombinant FVIII: H.M. van den Berg
Dr. Van den Berg, who reported also on behalf of drs Gouw and Van der Bom, addressed the question whether treatment-related factors like early age at first exposure, early start of prophylaxis and a higher intensity of treatment concurrently with tissue damage would increase the risk of inhibitor development. An individual patient data meta-analysis has been performed on four international, multicentre studies of recombinant human factor VIII products (Kogenate Ò , Kogenate FS Ò , Recombinate Ò , ReFacto Ò ) including 236 previously untreated severe haemophilia A (FVIII:C <0.02 IU/ml) patients. The outcome was clinically relevant inhibitor development, defined as at least two positive inhibitor titres combined with a decreased recovery. The analysis included the effect of ethnicity, family history of inhibitors, age at first exposure, start of regular prophylaxis, periods of intensive treatment, duration between exposure days and dosing of FVIII products on the risk of inhibitor development. The databases contained data on patient characteristics and all first fifty exposure days (dates, reason of treatment, dose, bodyweight) and inhibitor tests. However, FVIII gene mutations were not available. Sixty-seven of 236 patients (28.4%) developed clinically relevant inhibitory antibodies against factor VIII. Inhibitors developed at a median of 10 exposure days (IQR 7.5-17 days) at a mean age of 17.6 months. Forty-four were high titre (65.7%) and 23 were low titre inhibitors (34.3%). A black or hispanic ethnicity and a positive family history were positively related to inhibitor development. Dr. Van den Berg concluded that combination of age and intensity of treatment is highly associated with inhibitor development. Also peak moments, surgery and a higher dosing of FVIII were found to be statistically significant determinants of inhibitor development.
Prospective evaluation of a uniform factor replacement protocol in surgery: A.Srivastava
This report was a follow-up to the international survey done over the last 2 years to document current practices of factor replacement strategies for prophylaxis against post-operative bleeding in hemophilia. The data showed that both continuous and bolus infusion techniques were widely used with doses varying up to 5-fold between centers for similar procedures with no apparently significant difference in complications. This was so regardless of the location of the centers in developed or developing countries. The need for some standardization of practice was obvious. From the various protocols received and based of average figures of factor replacement, consensus protocols were evolved for bolus and continuous infusions and lower and higher doses. Centers were invited to comment on the proposal, choose a protocol that they felt comfortable with and join the effort at collecting prospective information on outcome and complications of surgery. Once identified, funding will be sought for data management and the study initiated over the next 6-12 months. In the discussion, the issue was raised whether this design would be compatible with the notion that individual patients may need individualised dosage. In response to this, Dr Srivastava explained that the advantage of his proposal is its prospective study design.
Assessment of inhibitor risk: new approach for trial design and evaluation: M.L. Lee
Dr Lee discussed a new analytical method to design and evaluate data from clinical studies of new Factor VIII products where the endpoint is inhibitor development. Current approaches to this problem involve the evaluation of approximately 80-100 patients followed by the calculation of a 95% confidence interval for the inhibitor rate. The upper bound of this interval is then compared with some fixed standard. The basic problem with this approach is that it requires an underlying rate in the order of 1% to succeed. Since confidence intervals are a function of sample data and not fixed quantities, fundamental analytical problems arise. Dr. Lee proposed the use of a Bayesian paradigm, whereby any and all prior information on the safety of the product (or similar products) is employed. The clinical data from a prospective study is then used to update this prior knowledge, resulting in a final calculation of a “posterior” probability that the product meets some acceptable standard. This approach is clinical intuitive and provides a very interpretable outcome from the study data. Moreover it is shown that this approach provides acceptable conclusions for currently licensed recombinant Factor VIII products, but would reject a product with known inhibitor risk (Bisinact). Details of this proposal have been recently published (Haemophilia 2005, vol 11, pp 5-12)
Molecular characterisation of haemophilia A patients with undetectable mutations in the FVIII gene: A. Srivastava
Dr Srivastava presented also on behalf of Dr. Oldenburg. About 2% of patients with hemophilia A do not have detectable mutations in the FVIII gene. This could be due inadequate sensitivity of current techniques for detecting sequence change in this gene or changes being in parts of this gene or other genes not being analyzed. Significant numbers of such cases have not been systematically analyzed. This proposal intends to initiate an international multicenter effort at identifying such cases, reviewing their clinical and hematological features, reassessing their status for mutations within the FVIII coding regions and then subjecting them to further analysis if found to be negative. This would include analysis of peripheral blood lymphocytic RNA for detection of splice defects or rearrangements. If this was negative, then haplotype analysis would be undertaken for familial cases see if FVIII deficiency was segregating with the FVIII gene. If so, epistatic factors would need to be evaluated in these cases. For the others, one approach could be a genome wide linkage analysis to identify regions of interest (increased lod scores) followed by further analysis / sequencing of these regions. These issues will be discussed further once the participating centers are identified and resources found for this project.
Section 2: Standardisation Issues: Co-Chairs: J.M. Saint-Remy and K. Mertens
FVIII Collaborative Studies: Phase I field study: S. Raut
Dr. Raut reported on a new FVIII SSC Collaborative Study. This project has been on hold for a few years, mainly due to limited improvements achieved during the successive studies. Last year the Steering Committee that oversees these activities decided that the program may be resumed provided that it will be performed in a more controlled format. As a first step the number of samples has been extended which should make some more detailed analysis possible. Four samples (3 recombinants and 1 plasma-derived) have been distributed over 31 participants. Data were received from 30 labs. Methods used were the 1-stage assay (12 labs) and the chromogenic assay (the majority). Standards included the EP/Mega-2 standard, and in-house standards calibrated directly against the WHO standard. Dr. Raut explained that, as in previous studies, the results still were unsatisfactory, with GCVs between 14 and 19%. The data further revealed assay discrepancies, which differed for plasma-derived (1-stage > chromogenic) and recombinant (1-stage < chromogenic) FVIII. This unique data set will be further analysed in more detail. This will further provide an opportunity to analyse potency estimates based on the EP/Mega-2 standard material, which has two different assigned potencies depending on the FVIII assay method used. The extended data analysis will be reported at the meeting in 2006.
ECAT study on FVIII inhibitor assays: B. Verbruggen
Dr. Verbruggen reported on the recently concluded ECAT study. Three samples containing respectively 0, 1.5 and about 16 u/ml FVIII inhibitors were sent to 175 laboratories worldwide, with 135 responded (77%). For the negative sample, 4 laboratories reported a positive result. For the high-titer sample, all the reported results were positive, the coefficient of variation (CV) ranged from 32% for the Nijmegen method to more than 60% for the Bethesda method. For the low-titer sample, 16/131 (8%) results were reported negative with similar CVs as for the high titer sample. Based on these results Dr. Verbruggen concluded that the specificity of the used methods is acceptable but the sensitivity of the reported method is rather low. Further standardisation of the assay method seems needed.
Factor VIII inhibitor assay standardisation: S. Raut
Three types of reagents have been used in an attempt to standardize an assay for inhibitor detection, namely rabbit polyclonal antibodies, two different human monoclonal antibodies derived from the memory B cell repertoire of patients with inhibitors (one type 1 and one type 2 inhibitor) and human plasma. The latter was found difficult to use for ethical reasons. Results show large variations between laboratories, the less so with rabbit polyclonal antibodies. The reasons for such variation are being examined, including the source of FVIII, dilution buffers and the method actually used by laboratories to carry out the assay. Confounding factors include the possible interference due to the presence of rheumatoid factor or anti-allotypic antibodies in some of the serums. Based on these findings Dr. Raut concluded that a collaborative study would be useful to address assay standardisation. Currently a Steering Committee is being formed in order to decide on the design of the Working Party and to oversee its future activities.
SSC working standard (plasma lot 3): summary of calibration: S. Kitchen
Calibrations of the Scientific and Standardisation Committee (SSC) Secondary Coagulation Standard Lot #3 for Factor VIII:C, von Willebrand Factor Ristocetin Cofactor Activity (VWF: RCo). von Willebrand Factor Collagen binding (VWF:CB) and von Willebrand Factor Antigen (VWF:Ag) were carried out against the h World Health Organisation (WHO) International Standard (IS) for Factor VIII/VWF and IX in plasma (02/150). A total of 19 expert laboratories in 11 countries participated in this collaborative study employing the same assay protocol but with different reagents and instruments. The overall geometric mean potencies (* excluding 1 statistical outlier) were as follows:
These potencies have been accepted by the participating centres and by the SSC Working Group on Coagulation Standards..
Human Genome Variation Society: nomenclature recommendations: A. Goodeve
The Human Genome Variation Society (HGVS) has devised a series of nomenclature recommendations for gene names, nucleotide and amino acid alterations over the past 10 years. Recommendations are available at http://www.genomic.unimelb.edu.au/mdi/mutnomen/. These detail how all sequence variation can be described using a standardised system. A number of journals and genetics EQA schemes are now specifying use of this system. Factor VIII and IX genes are denoted F8 and F9. A standardised start point of the first methionine for proteins and the A of the ATG start codon for nucleotide sequence, using the cDNA sequence where possible are recommended for all genes. Dr. Goodeve mentioned that the haemophilia databases can adopt this new system, if accepted. In the discussion it was acknowledged that this proposal would indeed eliminate many inconsistencies in the genetic literature. At the same time, however, it might raise confusion in the protein literature on the FVIII and FIX proteins. In this regard Dr. Mertens referred to the dual numbering for the FIX serine protease domain (FIX and chymotrypsin numbering) which is already confusing sometimes. As such, the merit of a third amino acid numbering remains unclear.
Prothrombin complex labelling: R. Seitz
Dr. Seitz presented in vitro and animal experiments demonstrating that prothrombin overload leads to enhanced thrombin generation and appears to be a major cause of thromboembolic complications during treatment with PCC. The European Pharmacopoeia considers changing the monograph on PCC to make factor II the labelled potency of PCC. Dr. Seitz asked for the input of the subcommittee concerning the following questions: Are licensed PCC products still used for haemophilia B treatment? How would the proposed change of labelling impact on the clinical use? Would there be a need to carry out new clinical studies? During the discussion Dr. Barrowcliffe noted that the prothrombin overload was mainly associated with a single PCC product that is not being used outside Germany. Along the same line, Dr. Mertens suggested that this problem should not impact on other manufacturers whose products do have equivalent FIX and prothrombin content. As PCCs continue to be used for haemophilia B treatment outside Europe and the USA, the Subcommittee does not support changing the current labelling practice.
Factor V: calibration of 1 st International Standard: A. Hubbard
An international collaborative study involving 22 laboratories in 11 countries has been undertaken to calibrate the Proposed WHO 1st IS FV Plasma for FV clotting activity. Each laboratory estimated FV:C in the candidate preparation relative to a local normal pooled plasma which was arbitrarily assigned a value of 1.0 unit per ml. Most laboratories (21/23) used thromboplastin-based methods rather than APTT-based methods. Estimates relative to the fresh local pools (mean 0.74 IU/ml) were significantly lower than estimates relative to the frozen local pools (mean 0.80 IU/ml) and this could be an indication that some FV:C activity has been lost during freeze-thawing of the frozen pools. It is therefore proposed that the calibration should be based only on the estimates relative to the fresh local pools with a mean value of 0.74 IU/ampoule and inter-laboratory variability (GCV) of 7.6%. Estimation of FV:C in a second freeze-dried plasma (SSC/ISTH Secondary Coagulation Standard) relative to the Proposed WHO 1st IS demonstrated low inter-laboratory variability (GCV 3.5%, n=23); this indicates that the Proposed WHO 1st IS should lead to improved harmonization between laboratories. Estimates of stability based on an accelerated degradation study have predicted a loss of less than 0.01 % per year at -20 oC. All of the participating laboratories have agreed to the proposal to calibrate the WHO 1st IS with a value of 0.74 IU/ampoule. Prior to the meeting, the Chairman had distributed the report among Subcommittee members for a vote per email. This has resulted in acceptance of Dr. Hubbard’s proposal by the Subcommittee.
Section 3: Rare Bleeding Disorders: Co-Chairs: A. Srivastava and K. Mertens
SSC Working Party on Rare Inherited Bleeding Disorders: F.Peyvandi
Dr. Peyvandi reported that the main goals of this official SSC-endorsed Working Party are two-fold. The first goal addresses database development, which should serve to (a) identify current national and international databases, (b) identify potential collaborators worldwide, particularly in areas where RBDs could collect data, (c) finalize database tools and data collection protocols and disseminate worldwide and (d) establish a Steering Committee for data evaluation. The second goal relates to product development and licensure. This involves the following step: (a) to finalize common regulatory requirements within FDA/EMEA, (b) to identify already available products (FVII, FXI, FXIII, fibrinogen), (c) to design completed clinical trial in order to get global licensure, (d) to explore new product development (FV) and (e) to design implement post-licensure surveillance. So far an International Database on RBDs (RBDD, www.rbdd.org) has been developed, with the aim of efficiently collecting and extracting available data. Dr Payvandi has contacted National and International Organizations and Treatment Centres registered in the WFH mailing list with the aim to learn how many Centres would like to participate and what type of intervention needs to be done in each region of the world; so far 22 centres have already responded.
Update MASAC Working Party on US situation: D.M. DiMichele
This update was presented by Donna DiMichele on behalf on the Working Party on RBDs of the Medical and Scientific Advisory Council of the NHF, chaired by Amy Shapiro. The report focused on efforts planned by this group in the aftermath of the FDA Workshop on Rare Plasma Protein Disorders held June 13-14, 2005 in accordance with the priorities established by both this meeting and by the FVIII/IX Subcommittee Working Party on RBDs. The efforts planned include:
Treatment of rare bleeding disorders in Europe; the French organisation: J. Goudemand
Dr. Goudemand reported that patients affected with rare bleeding disorders in France are included in a national project: FranceCoag Network. This is a prospective multicenter national cohort of patients affected with severe and hereditary haemorrhagic disorders. FranceCoag network is funded by the French health Ministry and coordinated by a public health institution: INVS (Institut National de Veille Sanitaire). Beside the epidemiologic objectives, the aim is to set up a surveillance system able to investigate any unexpected events occurring in this population. Inclusion criteria are defect (<30%) in FVIII or IX, severe defects (<10%) in FII, V, VII, X, XI, XIII, afibrinogenemia, severe VWD. At that time 4049 patients registered in 37 French centres have been included in the project and 3439 record forms analyzed. There are 3103 patients (90%) with haemophilia, 239 (7%) with severe VWD and 97 (3%) with other rare bleeding disorders. Clinical and biological data are collected as part of the regular follow up (main bleeding episodes, surgeries, treatments, coagulation tests…) and monitored by the coordinating centre. The project (http://www.francecoag.org) is opened to any interested researcher with the agreement of the steering committee. Regarding the treatment, several specific concentrates (VWF, FVII, FXI, FXIII, Fibrinogen, PCC) are available in France to treat these patients.
Complications of management in rare bleeding disorders: U. Seligsohn
Dr. Seligsohn presented an interesting report on the management of bleeding with minimum usage of coagulation factor products. Plasma, and plasma derived or recombinant factor concentrates are used for management of patients with deficiencies of factors I, II, V, VII, X, XI or XIII during bleeding episodes or prophylaxis during surgery. Major complications include transmission of infections agents, development of inhibitors and thrombosis. The paradigm of severe factor XI deficiency was used to evaluate by retrospective analyses whether treatment by blood components during surgery and labor can be avoided or tailored. For tooth extractions, only tranexamic acid was necessary to prevent bleeding in 19 patients. A relatively low frequency of bleeding in 62 untreated women during vaginal (24%) or caesarian deliveries (17%) advocates an on-demand policy of replacement therapy. A similar policy is recommended in patients undergoing surgery at tissues with no fibrinolytic activity because only 8/121 (6.6%) of such procedures were accompanied by bleeding, compared to 29/48 (60.4%) during procedures at fibrinolytic sites. Retrospective analyses of patients with other deficiency states are warranted to minimize the deleterious effects of blood components.
Profile of rare bleeding disorders in India: A. Srivastava
With a population of about 1.1 billion people and significant practice of consanguineous marriages in major parts of the country, India has potentially large number of patients (250-1000) with the rare bleeding disorders. This presentation described the clinical and hematological features and the molecular genetics of 27 patients with fibrinogen, 7 patients with prothrombin, 20 patients with factor V, 25 patients with factor VII, 25 patients with factors V and FVIII, 19 patients with factor X, 3 patients with factor XI deficiency and 59 patients with factor XIII defects / deficiency. There were significant differences in the clinical features noted in this study when compared to the data in the literature. The cause for this was not clear. A wide variety of mutations, including many novel ones, were detected among patients with prothrombin, factors VII, X, XI and XIII deficiencies. Further characterization of these cases for better understanding their biology and management is progressing. A collaboration is being established with Dr. Peyvandi’s laboratory.
Report on FDA workshop “Biological therapeutics for rare plasma protein disorders”: M. Weinstein
FDA and the Office of Public Health and Science (OPHS) sponsored a workshop entitled, "Biological Therapeutics for Rare Plasma Protein Disorders “, in Bethesda, MD on June 13, 14. The focus of the workshop was to facilitate the development of products to treat patients with very rare plasma protein disorders – affected cohorts on the order of 10’s or 100’s in the US. Presentations from the international, patient, physician, and industry perspectives were made on the need for these products, and challenges to their development . We reviewed opportunities and incentives to foster development that are currently available in the US and Europe. These include regulatory pathways to license products with limited clinical data, orphan drug provisions and incentives, small business and research grant support, and the medicare payment program. Case studies of protein C, factor XIII, antithrombin III, and treatment of Glanzmann’s thrombasthenia and Fabry’s disease were presented as examples of product development for very small patient populations. Several potential opportunities for enhancing product development were identified. These included:
Slide presentations from the meeting are at http:/www.fda.gov/cber/summaries.htm. When available, transcripts of the workshop will be at http://www.fda.gov/cber/minutes/workshop-min.htm. A docket is being prepared for comments and suggestions for further product development.
The Chairman closed the meeting at 20.00, thanking the speakers and the audience for their contribution.