Thrombosis and Haemostasis © F K Schattauer Verlagsgesellschaft mbH (Stuttgart) 71 (6) 703-6 (1994)
Clinical Course of Factor VIII Inhibitors Developed öfter
Exposure to a Pasteurised Dutch Concentrate Compared
to Clossic Inhibitors in Hemophilia A
E. P, Mauser-Bunschoten
1, F. R, Rosendaal
2-
3, H. K. Nieuwenhuis
4, G. Roosendaal
1,
E. Briet
3, H. M. van den Berg
1From the 'Van Creveld Clinic, the 4Department of Hematology, Urwersity Hospital, Utrecht, and the 2Department of Clinical Epidemiology, the 3Department of Hematology, University Hospital, Leiden, The Netherlands
Summary
After the mtroduction of a new pasteunsed factor VIII concentrate (Factor VIIICPS-P) m The Netherlands rn June 1990, an mcrease m the occurrence of inhibitois m hemophihaA patients was reported The clinical course of this gtoup of Inhibitors (n = 12) was compared with hemophilia patients in whom an Inhibitor developed before June 1990 (classic Inhibitors) (n = 32) Stnkmg differences were found between both groups not only m patient age (median 22 yeais versus 8 yeais) and number of exposure days (<50 - >1000 versus <50), äs descnbed in previous reports, but also m clinical course and response to treatment In the recent group of mhibitois antibody titers showed a rapid declme when product was changed which was not the case m the group with classic Inhibitors In the gioup of classic Inhibitors immune tolerance therapy with low dose factor VIII succeeded m 83% Success was to a high degree dependent on the mhibitor level In the gioup of recent mhibitors immune tolerance with the same concentiate was only successful m a smgle patient However, once the patients were switched to anothei concentrate, antibody levels diopped to less than 2 BU/ml withm 8 months m all patients
It seems hkely that m this group of product associated mhibitors, treatment success was due to elimmation of antigen Stimulation rather than mductton of immune tolerance
Introduction
The development of antibodies to factor VIII (mhibitors) is a senous comphcation m hemophilia treatment It is estimated that about 5-25% of hemophilia patients develop mhibitors (1-8) In severe hemophilia inhibitois usually develop at an early age and are seldom found after 50 days of exposure to factor VIII clottmg products (7) In older patients mhibitor development is raie and usually without clinical problems
In 1991 a sudden mcrease in the development of mhibitors was seen m The Netherlands and Belgmm (9, 10) This mcrease was shown to be associated with one particular factor VIII pioduct This pasteunsed mtermediate punfied factor concentrate (factor VIII CPS-P) was mtroduced m 1990 by the Central Laboratory of The Netherlands Red Cross Blood Transfusion Service (CLB) Inhibitors weie subsequently detected m 12Dutch patients with hemophihaA, which imphed a
Conespondence to Dr E P Mauser-Bunschoten, Van Creveld Chmc University Hospital, Postbox 85500, N3508 AG Utiecht, The Netherlands -Fax Number +3130544397
5-fold mcreased nsk compared to the time penod pnor to the mtroduc-tion of this concentrate (9) In this paper we descnbe the clinical course m the 12 patients who developed an mhibitor after factor VIII CPS-P admimstration ("recent mhibitors") and compare this to those of hemophilia patients in whom an mhibitor was detected before the new product was mtroduced ("classic mhibitors")
Methods Study Population
The study population consisted of all 32 imbitor patients registered in our centei between 1966 and June 1990, äs well äs of 12 patients found m the national study on mhibitor formation m hemophilia patients between June 1990 and March 1992 Togethei they form the majonty (estimated at more than 90%) of hemophilia patients with a known mhibitor m The Netherlands Inhibitor patients could be divided mto three groups
Group l Classic Inhibitors
This group consisted of all mhibitor patients detected before June 1990 (n = 32) Nme of these patients (group l a) had not received immune tolerance therapy, whereas 23 patients (group l b) had received this tieatmenl m a dosage of 25 U/kg body weight (bw) factor VIII, given 3 times a week 01 on alternate days (11, 12) For immune tolerance therapy we used cryoprecipitate and a vanety of concentrates
Group 2 Recent Inhibito: s
Twelve patients m whom an mhibitor was detected after the mtroduction of factor VIII CPS-P (9) In none of these patients antibodies had been detected before, 11 of them have severe hemophilia Immune tolerance therapy m this group of patients varied fiom 25 U/kg bw factor VIII on alternate days, to 25 U/kg bw factor VIII daily
Evaluatwn of Immune Toleiance Therapy
Immune tolerance therapy was consideied to be successful when the mhibitor level feil to less than 2 BU/ml, with a factor VIII recovery of at least 50% of normal, a factor VIII half life of 6 h or more (13) and the absence of an anamnestic response of the mhibitor after mfusion with factor VIII
Laboratory Assay Plasma Samplmg
40
Ljüi
66 68 70 72 74 76 78 80 82 84 86 88 90 92 year of mhibitor devslopment
Fig l Cumulative numbei of hemophiha patients with an mhibitor detected between 1966 and 1992 m the Netherlands Classic = classic mhibitor detected between 1966 and June 1990 (group 1) CPS-P mh = recent mhibitors, detected after the mtroducüon of Factor VIII CPS-P m June 1990 (gioup 2)
1 00 000 12 36 —l— 48 60 72 months 84 i 1 1 96 108 120 Fig 2 Disappearance of factor VIII Inhibitors A Classic mhibitor patients (n = 5) never treated with factor VIII smce the detection of the mhibitor B Classic mhibitor patients (n = 27) treated with factor VIII or with immune tolerance therapy
C Recent mhibitor patients (n = 12) who developed an mhibitor after 1990 Table l General charactensation of the two groups of mhibitor patients
agemyeais median ränge days of exposure <50 >50 ränge clmical Symptoms yes no
maximum mhibitor titer m BU/ml total group ränge
successful ΓΓ unsuccessful ΓΓ classic·1' (n = 32) 8 1-39 32 0 12-<50 30 2 1 1-6400 1 1-164 44-450 recent·1· (n =12) 22 1-57 2' 10' 8->1000' 11 1 56-457 5 6-457 (2)2 (10)2 (8 -ISO)2
' classic Inhibitors detected between 1966 and 1990 (group 1) ^ recent mhibitors detected after 1990 (group 2)
1 exposure to all factor VIII concentrates 2 exposure to Factor VIII CPS-P 3 IT = Immune tolerance therapy
needle m a sihcone trealed Vacutamei tube m which 0 5 ml of 3 8% sodiumcitrate was added Immediately after collection samples weie caiefully mixed and centnfuged at 3000 X Gfor 15 mm at4°C, caiefully pipelted off and stored in a plastic tube at -20°C
Samples of all patients with classic mhibitors and of 11 recent mhibitoi palients with severe hemophiha were analysed at the coagulation laboratory of the Umversity Hospital of Utrecht (head Dr JW Akkerman) Additional mhibitoi measurements were performed at the local hemophiha centers Inhibitor As wy
Inhibitor measurements were peiformed usmg the Bethesda method äs
descnbed by Kasper et al (14) In patients with positive mhibitoi tests, blood samples foi mhibitor measurement weie taken every 4 to 8 weeks
Factor VIIIAssays
These were performed by the one stage method based on the kaolme activa ted partial thiomboplastme time and expressed äs a percentage of factor VIII present m pooled normal human plasma (15)
In Vivo Recovery
Blood samples for factor VIII assays were taken befoie and 15 mmutes after transfusion with factor VIII Recovery was defmed äs the level of factor VIII measured 15 mm aftei mfusion and the expected level calculated by the method accordmg to Lee et al (16) Recoveiy was assessed every 4 to 8 weeks m all mhibitoi patients who were treated with factor VIII
Statistical Analysis
The probabihty of the persistence of a factoi VIII mhibitoi over time was evaluated by the Kaplan Meier method (17) and the logiank lest (18) The startmg-pomt for the life-table was the initial treatment with immune tolerance therapy, or, m non-treated patients, the time of mhibitor delection
Results
Figure l shows the cumulative number of mhibitors regtstered m our center smce 1966 Most of the gradual increase over time will reflect the mcreased total number of hemophilia patients and the growth of the catchment area of our center In 1991 and 1992, however, an mcreased mcidence of mhibitor development occmred The clmical course of this group of mhibitor patients was compared with the classic mhibitor patient group (table 1)
l Classic Inhibitors (group 1)
In these 32 patients the mhibitor was first detected at a median age of 8 3 years (ränge 1-39 years) All mhibitors were detected before the 50th day of exposure, after treatment with cryoprecipitate, or vanous factor VIII concentrates Thirty patients were tested because of mcreased bleedmg problems, two were detected at routme laboratory control
Nme patients (group l a) did not receive immune tolerance therapy In five patients who did not receive any factor VIII therapy aftei developmg an mhibitor, the mhibitoi levels remamed above 10 BU/ml Three of these 5 patients died (one of an unmanageable bleedmg), the other two patients still have mhibitor levels above 30 BU/ml Four patients received only short-term factor VIII therapy (7 to 10 days), with 50 U/kg body weight daily, foi hfe threatemng bleedmg episodes or surgery Withm this penod their mhibitoi levels mcieased to over 100 BU/ml and factor VIII admimstiation had to be discontmued
Twenty-three patients (gioup l b) leceived immune toleiance theiapy Nineteen patienls (83%) weie tieated only with a low dose regimen (25 U/kg body weight 3-4 times a week), which was success ful aftei 2-28 months m all 19 patients In 2 patients immune toleiance was not achieved even aftei additional theiapy with gammaglobulms and cyclophosphamide (19), and factoi VIII theiapy was discontinued after two yeais Two othei patients still receive immune tolerance therapy
In eleven patients with mhibitoi titeis that nevei exceeded 60 BU/ml immune tolerance was obtamed more easily, aftei 2-11 months (median 6 months) than m the eight patients with mhibitoi levels above 60 BU/ml 12-28 months (median 19 months) Several factor VIII pioducts were used, without any obvious lelation between the concentrate and the success late
2 Recent Inhibitors (group 2)
Twelve patients m whom a persistent mhibitoi developed after June 1990 weie eligible for follow-up The median age at mhibitor development was 22 years (1-57 yeais) Stiikmgly, pnor to mhibitoi development, most patients had received several hundreds of exposures to factoi VIII with vanous concentiates, before they changed to Factor VIIICPS P After this change, it still took moie than 50 exposure days to this paiticulai concentiate before the mhibitor became appaient m ten of the twelve mhibitor patients
In two patients factor VIII admimstration was discontinued, and in the othei 10 patients immune toleiance theiapy with factor VIIICPS-P was staited, m a legimen of 25 U/kg body weight factor VIII on altemate days This therapy was successful in only one patient, wheieas mhibitoi levels lemamed the same 01 even incieased m mne Dosage increases to 50 U/kg body weight factor VIII (12,20) in 4 patients with severe clmical problems, and additional coiticosteroid admimstiation (21) m one of them, did not have any beneficial effect In all mne non-respondmg patients we switched to anothei concentrate, fust m the foui patients with debihtating bleedmgs, and latei, when Factor VIII CPS-P was taken of the maiket (Maich 1992), m the othei five patients In all mne patients the change to anothei concentiate resulted in a rapid deciease of the mhibitoi titei to less than l BU/ml withm 8 months, noimal recoveiy tests, and the disappearance of clmical bleeding Symptoms The concentiates that were used mstead of Factor VIII CPS-P mcluded ultra-puie monoclonally punfied and mtei mediale punfied concentrate, and pasteunsed äs well äs SD pioducts (Factor VIII M-SD, Hemofil M-SD, Monoclate-P, Haemate P)
In one patient immune tolerance therapy with factoi VIII CPS-P proved to be successful This patient lesembled a classic mhibitoi smce he had developed an mhibitoi withm 10 exposuie days at the age of l 5 yeais
As Fig 2 shows, Inhibitors disappeared much soonei (withm one year) m these lecently developed mhibitor patients than m classical mhibitois (p<00001) Moieover, success was achieved m all Inhibitors
Discussion
Previous leports have shown that the use of a particulai concentiate (factor VIII CPS-P) can be associated with an incieased nsk of mhibitoi development (9, 10) In this study we have shown that the clmical course of these Inhibitors is different foi classic mhibitois, with a rapid disappeaiance m all patients after a change of concentrate
Usually mhibitois m hemophiha patients are detected before 50 exposuie days to factoi VIII (7) In oui gioup of classic mhibi-tois antibodies were detected at a relatively late age, 7 years (lange 1-22 yeais) This can be explamed by the fact that most Inhibitors weie diagnosed before 1980 at that time leplacement therapy was less ftequent than today and mhibitor measurements were not perfoimed on a routme basis However the median age m the group of lecent inmbitors was much higher 22 years (lange 1-57 years) In the classic mhibitor gioup the total number of exposuie days to any pioduct was much lowei than in the group of lecent Inhibitors Moreover, the patients m this last group even had a highei number of exposure days to the new concentiate Factor VIII CPS P pnoi to the mhibitor developed
Until 1982 it was common piactice to discontmue factor VIII theiapy once an mhibitoi had developed In our clmic immune toleiance theiapy was staited m most mhibitor patients between 1982 and 1985 Successful immune toleiance therapy seems to be mdepen-dent of the pioduct used, but highly depenmdepen-dent on the mhibitor level (11, 12) In patients with mhibitor levels over 50 B U/l mhibitoi titers dechned only slowly, wheieas patients with mhibitor levels over 200 BU/ml did not respond even to the most extended and comprehen sive immune tolerance legimens (19) In sharp contrast the decrease of the mhibitor titers in the group of lecent mhibitors was related to the pioduct used foi immune toleiance therapy, rathei than to the mhibitoi level Only an 18 months old patient with less than 10 days of exposure to factor VIII seemed to behave hke a classic mhibitor It is stnkmg that 2 patients with mhibitor levels ovei 300 BU/ml showed a lapid fall of mhibitoi titers after the change to another concentrate It seems hke that the mechamsm of this successful treatment was nol that of immune toleiance, which is thought to be the lesult of anti idiotype anlibody formation (22) A possible explanation foi the lapid declme of mhibitor titeis is that the change of concentiate led to the removal of an umque anügemc Stimulation aftei which the pioduction of antibodies stopped This also has been made plausible m laboratoi y mvestigations (23)
The cause of the antigemcity of Factor VIII CPS-P remams unclear Its predecessoi, Factor VIII CPS was prepaied by control led-poie silica adsoiption (24), and mitially diy heal-lrealed at 68° C for 72 h (CPS HT) Aftei the mtroduction of Factoi VIII CPS-HT m 1988, no mciease in mcidence of mhibitors was seen (9) In 1990 a fuither improvement m virus safety was achieved with the mtroduction of pasteunsation (Factoi VIII CPS-P) (25) Still pasteunsation itself does nol seem to change immunogemcity This may be concluded ftom the fact that similar mhibitor epidemics were not observed aftei the mtroduction of other pasteunsed products (9) and is also suppoited by the fact thal m 5 palienls Factoi VIII CPS-P was replaced by anolher pasteunsed product with good lesult Thoiough analysis of the production process of Factoi VIII CPS-P was undeitaken bul no explanation has been found Recently, it has been shown that the pasteunsed product had a much higher rate of factor Xa geneiation lhan the diy heat-treated, suggestive of the presence of small amounts of activated factor VIII (26) It is not obvious why this would lead to a highei nsk of mhibitoi develop-ment, and moie leseaich will be necessaiy lo further clanfy the umque event of an epedemic of mhibitois m multitiansfused hemophi-ha patients
In summary We conclude thal the mcrease m the mcidence of mhibitois from 1990 lo 1992 m The Netherlands aftei mtroduction of Factoi VIII CPS-P was followed by a rapid disappearance of all mhibitors after the patienls had switched to another concentrate
References
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Recewed September 24,1993 Accepted after resubmission February 21,1994
