Lack of desmopressin (DDAVP) response in men with hemophilia A following liver transplantation

Genotype-Dependent Response to Desmopressin in Hemophilia A and Proposal of a Predictive Response Score

BACKGROUND

 Desmopressin (DDAVP) is used in patients with moderate/mild hemophilia A (PWMHs) to increase their factor VIII (FVIII) level and, if possible, normalize it. However, its effectiveness varies between individuals. The GIDEMHA study aims to investigate the influence of F8 gene variants.

MATERIAL AND METHODS

 The study collected the trajectory of FVIII levels from therapeutic intravenous DDAVP tests in four French hemophilia treatment centers. A pharmacological analysis was performed associated with efficacy scores according to F8 variants: absolute and relative responses, as well as new scores: absolute duration (based on duration with FVIII ≥ 0.50 IU.mL-1) and relative duration (based on half-life).

RESULTS

 From enrolled 439 PWMHs, 327 had a hot-spot F8 variant (with ≥5 PWMHs). For these, the median (min-max) basal and peak FVIII were 0.20 (0.02-0.040) and 0.74 (0.14-2.18) IU.mL-1 respectively, with FVIII recovery being 3.80 IU.ml-1 (1.15-14.75). The median FVIII half-life was 3.9 hours (0.7-15.9 hours). FVIII was normalized (≥0.50 IU.mL-1) in 224/327 PWMHs (69%) and the median time with normalized FVIII was 3.9 hours (0.0-54.1 hours). Following the response profiles to DDAVP defined by the four efficacy scores, four groups of F8 variants were isolated, and then compared using survival curves with normalized FVIII (p < 0.0001): "long-lastingly effective" [p.(Glu739Lys), p.(Ser2030Asn), p.(Arg2178His), p.(Gln2208Glu), and T-stretch deletion in intron 13]; "moderately effective" [p.(Ser112Phe), p.(Ala219Thr), p.(Thr2105Ile), p.Phe2146Ser), and p.(Asp2150Asn)]; "moderately ineffective" [p.Ala81Asp), p.(Gln324Pro), p.(Tyr492His), p.(Arg612Cys), p.(Met701Val), p.(Val2035Asn), and p.(Arg2178Cys)]; and "frequently ineffective" [c.-219C > T, p.(Cys2040Tyr), p.(Tyr2169His), p.(Pro2319Leu), and p.(Arg2326Gln)].

CONCLUSION

 In view of our data, we propose indications for DDAVP use in PWMH based on F8 variants for minor and major invasive procedures.

Observational cohort study of long-term outcomes of liver transplantation in haemophilia

INTRODUCTION

Gene therapy is now a reality for individuals with haemophilia, yet little is known regarding the quality-of-life impact of factor correction. As few data exist, and recognizing the analogy to liver transplantation (OLTX), we identified OLTX+ and OLTX- men in the ATHNdataset to compare post-OLTX factor VIII and IX on quality of life (QoL) by Haem-A-QoL and PROMIS-29.

METHODS

OLTX- were matched to OLTX+ by age, race, and haemophilia type and severity. Deidentified demographic data, including post-transplant factor levels, genotype and target joint disease were analysed by descriptive statistics. Haem-A-Qol and PROMIS-29 were compared in OLTX+ and OLTX- by student's t-test and univariate regression models.

RESULTS

Of 86 people with haemophilia A (HA) or haemophilia B (HB) cared for at 10 haemophilia treatment centers (HTCs), 21 (24.4%) OLTX+ and 65 (75.6%) OLTX- were identified. OLTX+ and OLTX- had a similar frequency of target joint disease (p = .806), HA genotypes, null versus non-null (p = .696), and HIV infection (p = .316). At a median 9.2 years post-OLTX, median FVIII, .63 IU/mL [IQR 0.52-0.97] and FIX, .91 IU/mL [IQR .63-1.32], Haem-A-QoL, PROMIS-29, and HOT scores were comparable. Severe HA/HB had lower post-OLTX 'dealing with haemophilia' scores (p = .022) and higher 'sports and leisure' (p = .010) and 'view of yourself' scores (p = .024) than OLTX+ non-severe participants. Non-caucasian OLTX+ had significantly lower scores in sports and leisure (p = .042), future expectations (p = .021) and total score (p = .010).

CONCLUSION

Nine years after OLTX, QoL is comparable to OLTX-, but significantly better in OLTX+ with severe than non-severe disease and in caucasians than non-caucasians.

Desmopressin in moderate hemophilia A patients: a treatment worth considering

Desmopressin increases endogenous factor VIII levels in hemophilia A. Large inter-individual variation in the response to desmopressin is observed. Patients with a lower baseline factor VIII activity tend to show a reduced response, therefore, desmopressin is less frequently used in moderate hemophilia A patients (baseline factor VIII activity 1-5 international units/deciliter), even though factor VIII levels may rise substantially in some of them. We aim to describe the response to desmopressin in moderate hemophilia A patients and to identify predictors. We selected data on 169 patients with moderate hemophilia from the multicenter Response to DDAVP In non-severe hemophilia A patients: in Search for dEterminants (RISE) cohort study. Adequate response to desmopressin was defined as a peak factor VIII level ≥ 30, and excellent response as ≥ 50 international units/deciliter after desmopressin administration. We used univariate and multiple linear regression techniques to analyze predictors of the peak factor VIII level. Response was considered adequate in 68 patients (40%), of whom 25 showed excellent response (15%). Intravenous administration, age, pre-desmopressin factor VIII activity and von Willebrand factor antigen, peak von Willebrand factor activity and desmopressin-induced rise in von Willebrand factor antigen were significant predictors of peak factor VIII level and explained 65% of the inter-individual variation. In 40% of moderate hemophilia A patients, desmopressin response was adequate, thus it is important not to with-hold this group of patients from desmopressin responsiveness. Among the six predictors that we identified for desmopressin-induced factor VIII rise, factor VIII activity and desmopressin-induced rise in von Willebrand factor antigen had the strongest effect.

Life in the shadow of a dominant partner: the FVIII-VWF association and its clinical implications for hemophilia A

A normal hemostatic response to vascular injury requires both factor VIII (FVIII) and von Willebrand factor (VWF). In plasma, VWF and FVIII normally circulate as a noncovalent complex, and each has a critical function in the maintenance of hemostasis. Furthermore, the interaction between VWF and FVIII plays a crucial role in FVIII function, immunogenicity, and clearance, with VWF essentially serving as a chaperone for FVIII. Several novel recombinant FVIII (rFVIII) therapies for hemophilia A have been in clinical development, which aim to increase the half-life of FVIII (∼12 hours) and reduce dosing frequency by utilizing bioengineering techniques including PEGylation, Fc fusion, and single-chain design. However, these approaches have achieved only moderate increases in half-life of 1.5- to 2-fold compared with marketed FVIII products. Clearance of PEGylated rFVIII, rFVIIIFc, and rVIII-SingleChain is still regulated to a large extent by interaction with VWF. Therefore, the half-life of VWF (∼15 hours) appears to be the limiting factor that has confounded attempts to extend the half-life of rFVIII. A greater understanding of the interaction between FVIII and VWF is required to drive novel bioengineering strategies for products that either prolong the survival of VWF or limit VWF-mediated clearance of FVIII.

Patterns of expression of factor VIII and von Willebrand factor by endothelial cell subsets in vivo

Circulating factor VIII (FVIII) is derived from liver and from extrahepatic sources probably of endothelial origin, but the vascular sites of FVIII production remain unclear. Among organs profiled, only liver and lymph nodes (LNs) show abundant expression of F8 messenger RNA (mRNA). Transcriptomic profiling of subsets of stromal cells, including endothelial cells (ECs) from mouse LNs and other tissues, showed that F8 mRNA is expressed by lymphatic ECs (LECs) but not by capillary ECs (capECs), fibroblastic reticular cells, or hematopoietic cells. Among blood ECs profiled, F8 expression was seen only in fenestrated ECs (liver sinusoidal and renal glomerular ECs) and some high endothelial venules. In contrast, von Willebrand factor mRNA was expressed in capECs but not in LECs; it was coexpressed with F8 mRNA in postcapillary high endothelial venules. Purified LECs and liver sinusoidal ECs but not capECs from LNs secrete active FVIII in culture, and human and mouse lymph contained substantial

FVIII

C activity. Our results revealed localized vascular expression of FVIII and von Willebrand factor and identified LECs as a major cellular source of FVIII in extrahepatic tissues.

Long-term outcome of liver transplantation in HCV/HIV coinfected haemophilia patients. A single centre study of 10 patients

The outcome and clinical features during long term follow-up of 10 haemophilia patients (haemophilia A n = 9, haemophilia B n = 1), who underwent successful orthotopic liver transplantation (OLT) due to hepatitis associated liver disease, are summarised.

PATIENTS

Eight patients were HIV/HCV co-infected. Despite severe postoperative complications, which were not bleeding-associated, all patients survived OLT.

RESULTS

Long-term survival was 70% after in mean 8 years follow-up. Twelve years after OLT one patient developed a cyclosporine-induced nephropathy requiring haemodialysis. HIV-HAART was initiated in all patients after OLT, and allowed a successful HCV treatment in 6 patients. Factor VIII production was sufficient in mean 72 h after OLT and remained stable at subnormal to normal FVIII levels of in median 30% (range 14-96%) also during long-term follow-up. Post-OLT spontaneous bleeding events were rare compared to pre-OLT, therefore, the performance status improved in all patients.

DISCUSSION

OLT substitutes the hepatic FVIII but has no effect on the extra-hepatic endothelial FVIII production, suggesting that in case of severe tissue injury enhanced bleeding might occur. Additionally, after OLT there is no acute phase reaction of the FVIII protein. Therefore, our OLT patients received in case of a reduced FVIII activity a peri-interventional prophylactic short-term FVIII substitution in surgical and diagnostic interventions with high bleeding risk.

CONCLUSION

Bleeding and wound healing disturbances were not seen.

Murine coagulation factor VIII is synthesized in endothelial cells

The primary cellular source of factor VIII (FVIII) biosynthesis is controversial, with contradictory evidence supporting an endothelial or hepatocyte origin. LMAN1 is a cargo receptor in the early secretory pathway that is responsible for the efficient secretion of factor V (FV) and FVIII to the plasma. Lman1 mutations result in combined deficiency of FV and FVIII, with levels of both factors reduced to ~10% to 15% of normal in human patients. We generated Lman1 conditional knockout mice to characterize the FVIII secretion profiles of endothelial cells and hepatocytes. We demonstrate that endothelial cells are the primary biosynthetic source of murine FVIII and that hepatocytes make no significant contribution to the plasma FVIII pool. Utilizing RiboTag mice and polyribosome immunoprecipitation, we performed endothelial cell-specific messenger RNA isolation and quantitative polymerase chain reaction analyses to confirm that endothelial cells highly express F8 and to explore the heterogeneity of F8 expression in different vascular beds. We demonstrate that endothelial cells from multiple, but not all, tissues contribute to the plasma FVIII pool in the mouse.

A conditional knockout mouse model reveals endothelial cells as the principal and possibly exclusive source of plasma factor VIII

The cellular source of coagulation factor VIII (FVIII) remains controversial. Like many coagulation proteins, FVIII is produced in the liver, and FVIII synthesis has long been associated with hepatocytes. But extrahepatic synthesis also occurs, and mounting evidence suggests that hepatocytes are not responsible for FVIII production. To determine the tissue that synthesizes FVIII, we developed a Cre/lox-dependent conditional knockout (KO) model in which exons 17 and 18 of the murine factor VIII gene (F8) are flanked by loxP sites, or floxed (F8(F)). In cells expressing Cre-recombinase, the floxed sequence is deleted, resulting in F8(F→KO) gene inactivation. When F8(F) mice were crossed with various tissue-specific Cre strains, we found that hepatocyte-specific F8-KO mice are indistinguishable from controls, whereas efficient endothelial-KO models display a severe hemophilic phenotype with no detectable plasma FVIII activity. A hematopoietic Cre model was more equivocal, so experimental bone marrow transplantation was used to examine hematopoietic FVIII synthesis. FVIII(null) mice that received bone marrow transplants from wild-type donors were still devoid of plasma FVIII activity after hematopoietic donor cell engraftment. Our results indicate that endothelial cells are the predominant, and possibly exclusive, source of plasma FVIII.

Mesenchymal stem cells contribute to endogenous FVIII:c production

Besides the liver, it has been difficult to identify which organ(s) and/or cellular component(s) contribute significantly to the production of human FVIII:c (FVIII). Thus far, only endothelial cells have been shown to constitute a robust extrahepatic source of FVIII, possibly explaining both the diverse presence of FVIII mRNA in the body, and the observed increase in FVIII levels during liver failure. Here, we investigate whether human mesenchymal stem cells (MSC), ubiquitously present in different organs, could also contribute to FVIII production. MSC isolated from human lung, liver, brain, and bone marrow expressed FVIII message as determined by quantitative-RT-PCR. Using an antibody specific for FVIII, confocal microscopy, and umbilical cord-derived endothelial cells (HUVEC) as a negative control, we demonstrated that, in MSC, FVIII protein was not stored in granules; rather, it localized to the perinuclear region. Furthermore, functional FVIII was detected in MSC supernatants and cell lysates by aPTT and chromogenic assays. These results demonstrate that MSC can contribute at low levels to the functional FVIII pool, and advance the understanding of the physiology of FVIII production and secretion.

Intravascular recovery of VWF and FVIII following intraperitoneal injection and differences from intravenous and subcutaneous injection in mice

Intravenous infusion studies in humans suggest that both von Willebrand factor (VWF) and factor VIII (FVIII) remain intravascular in contrast to other coagulation proteins. We explored whether infusion of VWF and FVIII by either intraperitoneal (i.p.) or subcutaneous (s.c.) injection would result in efficient absorption of these large proteins into the vascular circulation. FVIII(null) or VWF(null) mice were infused with plasma-derived or recombinant VWF and/or FVIII by i.p., s.c., or intravenous (i.v.) injection. Both VWF and FVIII were absorbed into the blood circulation after i.p. injection with a peak between 2 and 4 h at levels similar to those observed in mice infused intravenously. In contrast, neither VWF nor FVIII was detected in the plasma following s.c. injection. Although i.v. injection achieved peak plasma levels quickly, both human VWF and FVIII rapidly decreased during the first 2 h following i.v. injection. Following both i.v. and i.p. infusion of VWF, the multimeric structure of circulating VWF was similar to that observed in the infusate. These results demonstrate that both VWF and FVIII can be efficiently absorbed into the blood circulation following i.p., but not s.c. injection, indicating that i.p. administration could be an alternative route for VWF or FVIII infusion.

Factor VIII alters tubular organization and functional properties of von Willebrand factor stored in Weibel-Palade bodies

In endothelial cells, von Willebrand factor (VWF) multimers are packaged into tubules that direct biogenesis of elongated Weibel-Palade bodies (WPBs). WPB release results in unfurling of VWF tubules and assembly into strings that serve to recruit platelets. By confocal microscopy, we have previously observed a rounded morphology of WPBs in blood outgrowth endothelial cells transduced to express factor VIII (FVIII). Using correlative light-electron microscopy and tomography, we now demonstrate that FVIII-containing WPBs have disorganized, short VWF tubules. Whereas normal FVIII and FVIII Y1680F interfered with formation of ultra-large VWF multimers, release of the WPBs resulted in VWF strings of equal length as those from nontransduced blood outgrowth endothelial cells. After release, both WPB-derived FVIII and FVIII Y1680F remained bound to VWF strings, which however had largely lost their ability to recruit platelets. Strings from nontransduced cells, however, were capable of simultaneously recruiting exogenous FVIII and platelets. These findings suggest that the interaction of FVIII with VWF during WPB formation is independent of Y1680, is maintained after WPB release in FVIII-covered VWF strings, and impairs recruitment of platelets. Apparently, intra-cellular and extracellular assembly of FVIII-VWF complex involves distinct mechanisms, which differ with regard to their implications for platelet binding to released VWF strings.

Platelets as delivery systems for disease treatments

Platelets are small, anucleate, discoid shaped blood cells that play a fundamental role in hemostasis. Platelets contain a large number of biologically active molecules within cytoplasmic granules that are critical to normal platelet function. Because platelets circulate in blood through out the body, release biological molecules and mediators on demand and participate in hemostasis as well as many other pathophysiologic processes, targeting expression of proteins of interest to platelets and utilizing platelets as delivery systems for disease treatment would be a logical approach. This paper reviews the genetic therapy for inherited bleeding disorders utilizing platelets as delivery system, with a particular focus on platelet-derived FVIII for hemophilia A treatment.

Targeting FVIII expression to endothelial cells regenerates a releasable pool of FVIII and restores hemostasis in a mouse model of hemophilia A

The natural cell type(s) that synthesize and release factor VIII (FVIII) into the circulation are still not known with certainty. In vitro studies indicate that artificial expression of FVIII in endothelial cells produces an intracellular pool of FVIII that can be mobilized together with its carrier protein, von Willebrand factor (VWF), by agonists. Here, we show that expression of human B-domain deleted FVIII (hFVIII) in the vascular endothelium of otherwise FVIII-deficient mice results in costorage of FVIII and VWF in endothelial Weibel-Palade bodies and restores normal levels and activity of FVIII in plasma. Stored FVIII was mobilized into the circulation by subcutaneous administration of epinephrine. Human FVIII activity in plasma was strictly dependent on the presence of VWF. Endothelial-specific expression of hFVIII rescued the bleeding diathesis of hemophilic mice lacking endogenous FVIII. This hemostatic function of endothelial cell-derived hFVIII was suppressed in the presence of anti-FVIII inhibitory antibodies. These results suggest that targeting FVIII expression to endothelial cells may establish a releasable pool of FVIII and normalize plasma FVIII level and activity in hemophilia A, but does not prevent the inhibitory effect of anti-FVIII antibodies on the hemostatic function of transgene-derived hFVIII as is seen with platelet-derived FVIII expression.

Alternative strategies for gene therapy of hemophilia

Hemophilia A and B are monogenic disorders that were felt to be ideal targets for initiation of gene therapy. Although the first hemophilia gene therapy trial has been over 10 years ago, few trials are currently actively recruiting. Although preclinical studies in animals were promising, levels achieved in humans did not achieve long-term expression at adequate levels to achieve cures. Transplantation as a source of cellular replacement therapy for both hemophilia A and B have been successful following liver transplantation in which the recipient produces normal levels of either factor VIII (FVIII) or factor IX (FIX). Most of these transplants have been conducted for the treatment of liver failure rather than for "curing" hemophilia. There are a variety of new strategies for delivering the missing clotting factor through ectopic expression of the deficient protein. One approach uses hematopoietic stem cells using either a nonspecific promoter or using a lineage-specific promoter. An alternative strategy includes enhanced expression in endothelial cells or blood-outgrowth endothelial cells. An additional approach includes the expression of FVIII or FIX intraarticularly to mitigate the intraarticular bleeding that causes much of the disability for hemophilia patients. Because activated factor VII (FVIIa) can be used to treat patients with inhibitory antibodies to replacement clotting factors, preclinical gene therapy has been performed using platelet- or liver-targeted FVIIa expression. All of these newer approaches are just beginning to be explored in large animal models. Whereas improved recombinant replacement products continue to be the hallmark of hemophilia therapy, the frequency of replacement therapy is beginning to be addressed through longer-acting replacement products. A safe cure of hemophilia is still the desired goal, but many barriers must still be overcome.

Protein replacement therapy and gene transfer in canine models of hemophilia A, hemophilia B, von willebrand disease, and factor VII deficiency

Dogs with hemophilia A, hemophilia B, von Willebrand disease (VWD), and factor VII deficiency faithfully recapitulate the severe bleeding phenotype that occurs in humans with these disorders. The first rational approach to diagnosing these bleeding disorders became possible with the development of reliable assays in the 1940s through research that used these dogs. For the next 60 years, treatment consisted of replacement of the associated missing or dysfunctional protein, first with plasma-derived products and subsequently with recombinant products. Research has consistently shown that replacement products that are safe and efficacious in these dogs prove to be safe and efficacious in humans. But these highly effective products require repeated administration and are limited in supply and expensive; in addition, plasma-derived products have transmitted bloodborne pathogens. Recombinant proteins have all but eliminated inadvertent transmission of bloodborne pathogens, but the other limitations persist. Thus, gene therapy is an attractive alternative strategy in these monogenic disorders and has been actively pursued since the early 1990s. To date, several modalities of gene transfer in canine hemophilia have proven to be safe, produced easily detectable levels of transgene products in plasma that have persisted for years in association with reduced bleeding, and correctly predicted the vector dose required in a human hemophilia B liver-based trial. Very recently, however, researchers have identified an immune response to adeno-associated viral gene transfer vector capsid proteins in a human liver-based trial that was not present in preclinical testing in rodents, dogs, or nonhuman primates. This article provides a review of the strengths and limitations of canine hemophilia, VWD, and factor VII deficiency models and of their historical and current role in the development of improved therapy for humans with these inherited bleeding disorders.

Factor VIII and von Willebrand factor interaction: biological, clinical and therapeutic importance

The interaction of factor VIII (FVIII) with von Willebrand Factor (VWF) is of direct clinical significance in the diagnosis and treatment of patients with haemophilia A and von Willebrand disease (VWD). A normal haemostatic response to vascular injury requires both FVIII and VWF. It is well-established that in addition to its role in mediating platelet to platelet and platelet to matrix binding, VWF has a direct role in thrombin and fibrin generation by acting as a carrier molecule for the cofactor FVIII. Recent studies show that the interaction affects not only the biology of both FVIII and VWF, and the pathology of haemophilia and VWD, but also presents opportunities in the treatment of haemophilia. This review details the mechanisms and the molecular determinants of FVIII interaction with VWF, and the role of FVIII-VWF interaction in modulating FVIII interactions with other proteases, cell types and cellular receptors. The effect of defective interaction of FVIII with VWF as a result of mutations in either protein is discussed.

A phase II prospective open-label escalating dose trial of recombinant interleukin-11 in mild von Willebrand disease

von Willebrand factor (VWF) is a multimeric glycoprotein that mediates platelet adhesion and is decreased in von Willebrand disease (VWD). 1-8 deamino-d-arginine vasopressin (DDAVP), the most common treatment for VWD, is limited by tachyphylaxis and inconvenience, and in 20% of the patients, unresponsiveness. Recombinant human interleukin-11 (rhIL-11), a gp-130 signalling cytokine with haematopoietic and anti-inflammatory activity, increases VWF antigen and its activity in heterozygous VWF(+/-) mice and dogs. To determine the biological efficacy and safety of rhIL-11 in non-bleeding human subjects with mild VWD, we conducted a phase II prospective open-label trial of rhIL-11 at 10, 25 and 50 mug kg(-1) subcutaneously (s.c.), given daily for 7 days in nine subjects with mild VWD. VWF and factor VIII (FVIII) levels increased gradually and progressively after s.c. rhIL-11, which was sustained through 7 days of dosing to 1.5- to 3-fold over baseline. Following intravenous DDAVP, 0.3 mug kg(-1), on day 7 there was a further boost in VWF and FVIII levels, suggesting that the mechanism of rhIL-11 differs from that of DDAVP. Platelet VWF mRNA expression measured by quantitative PCR increased from two- to eightfold over baseline, suggesting that the mechanism of rhIL-11 effect may be upregulation of VWF mRNA. VWF and FVIII levels returned to baseline by day 14. rhIL-11 was well tolerated with less than grade-1 hypertension, hypokalaemia and fluid retention. Recombinant IL-11 increases VWF levels in humans with mild VWD, justifying future clinical trials to determine its potential in preventing or reducing bleeding in this patient population.