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Abstract

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

General use of plasma components includes replacement for multiple coagulation factor deficiencies, for treatment of single coagulation factor deficiencies for which a concentrate is unavailable, and as a replacement fluid used in therapeutic plasma exchange for thrombotic thrombocytopenic purpura. Four major products currently transfused are fresh-frozen plasma (FFP), plasma frozen within 24 hours of phlebotomy (FP24), cryoprecipitate-poor plasma (CPP), and thawed plasma. FP24, CPP, and thawed plasma contain decreased amounts of labile coagulation factors. Pathogen reduction technology has included solvent/detergent, methylene blue, and ultraviolet light irradiation with psoralen or riboflavin treatment and is available in Europe but not in the United States. Pathogen-reduced plasma may contain reduced levels of certain coagulant and/or anticoagulant factors compared to FFP. Clinical findings with pathogen-reduced plasma have provided an impetus to the US Food and Drug Administration to promulgate specific requirements for approval of novel plasma products, some of which may be too burdensome for the industry to readily overcome.

ABBREVIATIONS:
aPTT =

activated partial thromboplastin time

B19 =

parvovirus B19

CPP =

cryoprecipitate-poor plasma

DIC =

disseminated intravascular coagulation

FP24 =

plasma frozen within 24 hours

MB =

methylene blue

PT =

prothrombin time

RCT(s) =

randomized controlled trial(s)

TPE =

therapeutic plasma exchange

TTP =

thrombotic thrombocytopenic purpura

Plasma contains a complex mixture of water, inorganic salts, organic compounds, and more than 1000 proteins, each of which may undergo further activation, degradation, or removal during processing, storage, and preparation for use in patients. While albumin and immunoglobulins comprise much of the biomass, the coagulation, antithrombotic, and complement factors are especially prone to alteration ex vivo, which could affect the efficacy and adverse events associated with the clinical use of a given formulation. Despite these potential differences, multiple available plasma products are generally used interchangeably in clinical practice for each of three broad indications: replacement in multiple coagulation factor deficiencies (e.g., disseminated intravascular coagulation [DIC]), replacement in single coagulation deficiencies (e.g., Factor [F]XI deficiency), and plasma exchange in thrombotic microangiopathic anemias. This report will provide a brief overview of the plasma components currently available for transfusion in the United States and the pathogen-reduced products commonly in use in other countries. We will then highlight the evidence suggesting that particular products may differ in their efficacy and/or safety profiles and describe the US regulatory approach that increasingly seeks to identify analytical differences in plasma products despite there being only weak observational evidence of clinical application.

GENERAL USE OF PLASMA PRODUCTS

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

Replacement of multiple coagulation factor deficiencies

Use of plasma products to treat multiple coagulation factor deficiencies is most often the case in severe bleeding and/or DIC. In these situations tissue injury, hypothermia, and acidosis may contribute to the activation of both the coagulation and the fibrinolytic pathways. Restoration of hemostasis using factor-specific components (e.g., cryoprecipitate for fibrinogen deficiency) or recombinant coagulant factors should be used before plasma infusion when indicated. Choosing the appropriate component and dosage is dependent on an analysis of the patient's volume and red blood cell (RBC) losses, as well as the sufficiency of the coagulation pathways by measuring prothrombin time (PT), activated partial thromboplastin time (aPTT), platelet (PLT) count and function, and the level of fibrinogen. After the exchange of approximately 1 blood vol (10 units in a 70-kg adult), there should be sufficient clotting proteins to control bleeding if the PLT count is at least 100,000.1 After two volume exchanges, clotting proteins may be diluted to as little as 5% of normal levels. To achieve a significant increase in factor activity, rapid infusion of 10 to 30 mL/kg of plasma may be required. In recent years, many trauma centers have instituted formula-driven massive transfusion protocols that advocate the early use of plasma infusion before the advent of laboratory detectable coagulation abnormalities, to prevent the onset of coagulopathy.2 These protocols specify a fixed ratio of RBCs to PLTs to plasma that should be infused irrespective of laboratory variables. “Massive transfusion” is often defined as the rapid loss of between 30 and 50% of total blood volume or the transfusion of at least 10 units of RBCs in a 24-hour period.

There is little evidence that there is a benefit to transfusing plasma in nonbleeding patients with liver disease with an elevated PT. Even in cases of hepatic resection there is no universally accepted standard of care. Plasma transfusion is indicated during the anhepatic phase of liver transplant, especially to maintain the levels of liver-derived factors with short half-lives (e.g., FVII); however, even then the number of units used varies tremendously across institutions. Remarkably, liver transplant may be performed successfully without any blood component use, as reported by Jabbour and coworkers3,4 in their study of Jehovah's Witness patients.

Plasma infusion to counteract the effects of warfarin is generally not indicated, unless the patient is actively bleeding or is a candidate for urgent surgery, and pathogen-reduced prothrombin complex concentrates that include FVII are not available. In these cases, infusion should be of adequate volume to correct the deficit (10-30 mL/kg). In routine nonurgent practice, vitamin K supplementation is a safer approach to factor replenishment and plasma is generally not warranted.

Replacement of single factor deficiency

Plasma may be used to treat single coagulation factor deficiencies when no pathogen-reduced plasma product or recombinant product is available, either to treat bleeding or as surgical or routine prophylaxis. Dosage depends on the patients' residual level of factor activity, the desired level of activity, the half-life of the factor involved, the presence or absence of inhibitors, and the duration of hemostasis required. Deficiencies treated in this manner may include FII, FV, FXI, FXIII, fibrinogen, and protein C.

Plasma exchange in thrombotic thrombocytopenic purpura

Daily single to 1.5-fold total blood volume therapeutic plasma exchange (TPE) is the first-line therapy for thrombotic thrombocytopenic purpura (TTP) and use of plasma as replacement fluid is detailed in another paper in this supplement. TTP is often caused by a relative lack of the von Willebrand factor (VWF)-cleaving metalloprotease (ADAMTS-13) that allows the interaction of high-molecular-weight VWF multimers with PLTs under sheer flow conditions. Microaggregates form, resulting in disseminated thrombi throughout the microvasculature and severe ischemic organ damage. The lack of ADAMTS-13 may be congenital or acquired, most commonly through an autoimmune antibody directed against the protease. TPE serves to remove these antibodies and replace the ADAMTS-13 protease. Plasma products that are reduced in high-molecular-weight VWF multimers are hypothesized to be less likely to trigger further TTP exacerbations.

CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

Plasma for transfusion may be obtained by separation from whole blood collections or by apheresis procedures from donors meeting all of the eligibility requirements for voluntary donation. The resulting components vary in volume from 150 to 300 mL, are diluted approximately 8% to 20% by anticoagulant, and contain naturally variable amounts of circulating proteins. The actual volume and type of anticoagulant, a mixture of citrate, phosphate buffer, and dextrose, are included on the label. For each coagulation protein, individual unit potency per milliliter may vary by 50% to 150% of a pooled standardized control, this representing the normal range. Variation in volume and potency therefore affords great unit-to-unit inconsistency that confounds efforts to standardize therapy. This is exacerbated for FVIII and VWF, where blood group O individuals express levels on average 30% lower than those with other ABO blood groups.5

Natural variation is exacerbated by ex vivo loss of labile protein activity (FVIII and, to a lesser extent, FV) during processing and storage of plasma.6 Plasma products other than fresh-frozen plasma (FFP) generally have reduced FVIII activity and are contraindicated for situations where replacement of FVIII is required. FVIII is an acute-phase reactant and is seldom at critical levels in those clinical situations that require plasma therapy. Richer sources of FVIII are available as cryoprecipitate, pathogen-reduced plasma-derived or recombinant FVIII concentrates, and these should be used when replacement is specifically indicated.

In the United States, most plasma for transfusion is collected from male donors or never-pregnant females to reduce the likelihood of transfusion-related acute lung injury (TRALI). These donors are less likely to harbor alloreactive HLA antibodies that are associated with TRALI reactions. After the recommendation by the AABB to minimize patient exposure to alloreactive antibodies, a dramatic decrease in fatal and nonfatal TRALI has been reported.7,8 Some blood centers may also screen female donors with a history of pregnancy for HLA antibodies alone, or together with HNA antibodies, to expand the donor pool and permit the distribution of “TRALI low-risk” antibody negative units.9 These practices currently are variably employed by blood centers in the United States and the actual risk of transfusing a unit containing alloreactive antibodies is best determined through discussions with the local blood supplier.

FFP

Plasma is obtained by separation from the RBCs and PLTs in a whole blood collection or collection by apheresis. The plasma is frozen at not more than −18°C and stored at these temperatures until it is thawed for transfusion. To be labeled as “FFP,” the plasma must be placed in a −18°C or lower freezer within 6 to 8 hours of phlebotomy, depending on the bag manufacturers' instructions. FFP contains high levels of stable and labile (FV and FVIII) proteins and is usually prepared in units of 200 to 250 mL, when derived from whole blood collections. Apheresis units, however, may be as large as 400 to 600 mL (“jumbo units”). FFP is thawed in a warm water bath (30-37°C) to return it to its liquid state and should be transfused within 24 hours of thaw.

Plasma frozen within 24 hours

Plasma frozen within 24 hours (FP24) is prepared solely from whole blood that is stored at 4-6°C after collection and must be separated and placed at not more than −18°C within 24 hours of phlebotomy. FP24 is usually prepared in units of 200 to 250 mL and contains levels of stable proteins that are comparable to those in FFP; however, the levels of FVIII and, to a lesser extent, FV are reduced (Table 1).5,6 FP24 is used for the same indications as FFP, that is, the treatment of single and multiple protein deficiencies and the treatment of TTP, although US labeling requires that FP24 not be used for indications specifically requiring replacement of FV and/or FVIII.

Table 1. Factor composition of plasma products relative to thawed FFP*
ProteinsFP24ThawedCryopoorCryoprecipitateS/DMBINTERCEPTMirasol
  • * 

    Estimates are approximate, as they represent multiple independent evaluations performed at different times, in various laboratories under varying conditions5,6,10-15[LEFT RIGHT ARROW]= >95% activity; [DOWNWARDS ARROW] = 80%-95% activity; [DOWNWARDS ARROW][DOWNWARDS ARROW] = 30%-79% activity; [DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW] = <30% activity.

  • † 

    On Day 5 after thaw.

  • HMW = high molecular weight.

Fibrinogen[LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FII[LEFT RIGHT ARROW][LEFT RIGHT ARROW][LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FV[LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW] [DOWNWARDS ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FVII[LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FVIII[DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
F IX[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FX[LEFT RIGHT ARROW][LEFT RIGHT ARROW][LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FXI[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
FXII[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW] [DOWNWARDS ARROW]
FXIII[LEFT RIGHT ARROW] [DOWNWARDS ARROW][DOWNWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW]
Antithrombin-III[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW]
Protein C[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
Protein S[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [DOWNWARDS ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
α2-Antiplasmin[LEFT RIGHT ARROW] [LEFT RIGHT ARROW] [DOWNWARDS ARROW][DOWNWARDS ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW]
VWF antigen[LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW][DOWNWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][UPWARDS ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW] [LEFT RIGHT ARROW]
VWF multimers[LEFT RIGHT ARROW][LEFT RIGHT ARROW]Reduced HMW Reduced HMW  [DOWNWARDS ARROW][DOWNWARDS ARROW]
VWF protease[LEFT RIGHT ARROW][LEFT RIGHT ARROW][LEFT RIGHT ARROW] [LEFT RIGHT ARROW][LEFT RIGHT ARROW][LEFT RIGHT ARROW][DOWNWARDS ARROW]

Plasma cryoprecipitate reduced or cryopoor plasma

This product is made by thawing FFP at 1 to 6°C, separating the cold-induced precipitate by centrifugation, and refreezing the remaining supernatant plasma. The cryoprecipitate-reduced plasma must be refrozen at not more than −18°C within 24 hours of thawing. This product differs from either FFP or FP24 as it is significantly deficient in FVIII, FXIII, fibrinogen, and VWF (Table 1). The high-molecular-weight forms of VWF are preferentially depleted, giving rise to the conjecture that it may be especially indicated for TPE in TTP, where high-molecular-weight VWF is thought to play a role in TTP pathogenesis. However, clinical efficacy of FFP and cryoprecipitate-poor plasma (CPP) is comparable (see below).

Thawed plasma

Thawed plasma is prepared from either FFP or FP24, by thawing the unit at 30 to 37°C and storing the liquid component at 1 to 6°C for up to 4 days after the initial thaw (5 days in total). As the days pass, there is some degradation of most clotting proteins; however, the levels of FII, FVII, F IX, FX, fibrinogen, and ADAMTS-13 are comparable to the levels found in FFP or FP24, even after 4 days. FVIII suffers the greatest degree of degradation.5

Liquid plasma

Liquid plasma is produced from whole blood within 5 days of the whole blood expiration date. Liquid plasma is maintained at 1 to 6°C and stored for up to 30 days and is deficient in labile factors. It is used primarily for immediate treatment of acutely bleeding patients, especially where reversal of the effects of warfarin is required, as the vitamin K–dependent factors FII, FVII, F IX, and FX are relatively stable under these storage conditions. Liquid plasma is rarely used in the United States.

Cryoprecipitated antihemophilic factor or cryoprecipitate

Cryoprecipitate is prepared from the cold-insoluble proteins removed from thawed FFP. The cryoprecipitate must be refrozen within 1 hour of the initial thaw. This product contains concentrated amounts of FVIII, FXIII, VWF, fibrinogen, and fibronectin. By regulation, each unit must contain at least 80 IU of FVIII and at least 150 mg of fibrinogen in variable amounts of plasma (usually 5 to 20 mL). This product is indicated primarily in the treatment of hemorrhage secondary to fibrinogen deficiency and in FXIII deficiency. It is also used for bleeding associated with uremia and as a second-line therapy for hemophilia A and von Willebrand disease. Two to 10 units may be pooled at the time of manufacturing and supplied as prepooled cryoprecipitate.

Source plasma

Source plasma is defined as plasma collected by apheresis and intended for further manufacturing. Source plasma may be collected from volunteer or paid donors and is not considered as a substitute for any of the plasma products licensed for transfusion.

PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

Solvent/detergent-treated plasma

Solvent/detergent (S/D) plasma is a pooled standardized pharmaceutical product with extensive in-process control16 first described by Horowitz and colleagues in 1992.17 Pools of plasma of a given ABO type are mixed with a solvent, 1% tri(n-butyl)phosphate, and a detergent, 1% Triton X-100. The pools are incubated at 30°C for 4 hours and then subjected to extraction with oil and chromatography on insolubilized C18 resin, to remove traces of the solvent and detergent. The final product may be concentrated before freezing (in the United States) and stored in standard volumes (e.g., 200 mL) for up to 4 years at not more than 18°C before use.18 The S/D process effectively destroys more than 5 logs of most enveloped viruses, including human immunodeficiency virus (HIV), hepatitis C virus, and West Nile virus, but not vaccinia virus, which demonstrates relative resistance.16,18 The process is also reported to destroy cells, bacteria, protozoa, and cellular fragments but not nonenveloped viruses such as parvovirus B19 (B19) and hepatitis A virus (HAV). Transfusion transmission of B19 has been reported with S/D plasma, despite the theoretical benefit of neutralizing antibodies present in pooled products.19 This risk may be reduced by prescreening plasma donors for B19 and HAV infection. S/D plasma has also been reported to carry reduced risk of TRALI and allergic reactions, possibly due to the dilution of individual alloreactive antibodies and allergens by the mixing process.16

S/D plasma products show evidence of variation according to the specific manufacturing processes employed. In Europe, more than 5 million units have been manufactured and distributed for transfusion by Octapharma AG (Lachen, Switzerland) or from other fractionators operating under license. Plasma is collected from whole blood or apheresis collections and is generally frozen within 4 hours. Factor content varies both by the time to initial freeze and by plasma source (whole blood versus apheresis).20 For the Octaplas product (Octapharma AG), 500 to 1600 units of thawed plasma are pooled and treated. Proteins are stabilized by a sodium hydrogen phosphate buffer and the solvent is extracted utilizing castor oil. In France, local manufacturers utilize pools of 100 plasma units. In contrast, PLAS+SD plasma (V.I. Technologies, Watertown, MA), produced and subsequently taken off of the market in the United States, employed pools of 2500 units that were frozen approximately 15 hours after collection. This process used calcium chloride as a buffer and soybean oil for extraction, followed by a concentration step to make up for losses of labile factors during processing.18

The S/D process leads to losses of the labile FV and FVIII and also of the serine protease inhibitor (serpins) activities of α1-antitrypsin and α2-antiplasmin, but not antithrombin (Table 1).10 The latter losses could interfere with the role of plasma transfusion in conditions with systemic activation of proteolytic cascades, such as DIC, acquired fibrinolytic states, and sepsis, where serpins are thought to play a regulatory role. FVIII loss is associated with a decrease in high-molecular-weight VWF, a change that may make S/D plasma a suitable replacement fluid during TPE in TTP. Distinct differences between PLAS+SD and the European S/D plasma have been demonstrated.21 PLAS+SD had lower levels of citrate and protein S as well as antitrypsin activity, but higher levels of complement 3a.16,22

S/D plasma was first introduced into clinical practice in Germany, based on observational studies demonstrating safety and efficacy.11 In a series of reports involving fewer than 100 patients, no differences were noted in clinical response, decrease in PT, and arrest in bleeding in patients with complex coagulopathies, massive transfusion, open heart surgery, and hereditary deficiency of coagulation factors.16,23,24 Three subsequent small randomized controlled trials (RCTs) compared S/D plasma with FFP in liver transplant and hepatopathy (49 patients randomized)25 and severe coagulopathy (40 patients randomized)26 and with methylene blue (MB) plasma in cardiopulmonary bypass surgery (71 patients randomized).27 Again, no clinical differences were noted and no safety issues were identified. For licensure in the United States, Horowitz and Pehta28 described observational studies in 48 patients with hereditary deficiencies of FII, FV, FVII, FX, FXI, and FXIII treated in 137 transfusion episodes for active bleeding (51 episodes), surgical prophylaxis (47 episodes), or routine prophylaxis (39 episodes), and an open-label, FFP-controlled study in TTP involving 32 patients (of which 13 evaluable patients were in the test arm—see below). These studies were followed by a randomized controlled study comparing S/D plasma and FFP in 45 patients with severe coagulopathy, which demonstrated no difference in correction of the PT or clinical response.29

MB-treated plasma

MB plasma treatment was developed in Springe, Germany,30 and is currently available in many European countries, in kits manufactured by Macopharma (THERAFLEX MB plasma, Mouvaux, France). Single units of 200 of 300 mL FFP are first leukoreduced and then mixed with a fixed dose of MB to produce a concentration of approximately 1 mmol/L, before exposure to a standard dose of visible light. The product is filtered to remove MB and its reaction breakdown products, leaving a MB concentration of 0.1 to 0.3 mmol/L before freezing and storage.18 MB is a phenothiazine compound that is activated by light to generate reactive oxygen species, mainly singlet oxygen, that reacts with membranes and proteins to inactivate a large variety of enveloped viruses with more than 5 logs kill, including HIV, hepatitis C, and, to a lesser extent (approx. 4 logs kill), some nonenveloped viruses, such as parvovirus B19. MB is not effective at inactivating white blood cells (WBCs), protozoa, bacteria, or intracellular viruses; however, the original process incorporated a freeze-thaw cycle to lyse cells, increasing the susceptibility of intracellular viruses to inactivation, while currently available systems rely on leukoreduction to remove the cells, thereby reducing the threat.16 Given that single units are treated, this process may be performed in routine blood center operations; however, the product has variable factor content, as represented by the FFP units from which it is made. Nevertheless, MB treatment is known to modify and reduce the functional activity of fibrinogen (24%-39% decrease), FVIII (13%-33% decrease), F IX (11%-23% decrease), and FXI (17%-27% decrease), and this is manifested by a prolongation in the PT and aPTT.31 Levels of most other proteins are within 20% of the untreated plasma and specifically, the anticoagulants protein C and S and antithrombin are relatively unaltered. Levels of VWF activity are reduced by 10% to 20% but the VWF multimeric distribution and VWF-cleaving protease activity is reportedly unchanged.18 MB has been studied in terms of safety and adverse reactions with few issues identified.32,33 There are few RCTs comparing MB and other forms of plasma in the literature; however, a small study reported in abstract form was performed in 71 cardiac surgery patients who received either S/D or MB plasma. MB plasma resulted in better replacement of protein S and α2 antitrypsin, but no difference in blood loss.27 A concern about potential in vitro mutagenic effects of MB and its derivatives led the Paul Ehrlich Institute to decline to relicense the product without an active final MB removal step, as is now incorporated into the commercial kits used in other European countries.

Psoralen and ultraviolet light–treated (INTERCEPT) plasma

INTERCEPT plasma is pathogen-reduced whole blood or apheresis plasma that is CE marked in Europe and is gradually being adopted in blood centers in Spain, France, Belgium, Switzerland, and other European countries. Whole blood plasma (usually pools of 2-3 units) or single-unit jumbo apheresis plasma (approx. 600 mL) is treated with a psoralen compound, amotosalen, plus ultraviolet A (UVA) light, followed by removal of the amotosalen and its breakdown products by use of a filter compound absorption device. The final product is frozen in 200-mL aliquots within 8 hours of collection, although earlier versions utilized an absorption phase of 16 hours on a different compound absorption device configuration, prolonging the treatment process. Amotosalen is a synthetic psoralen that readily crosses cell membranes and intercalates with DNA and RNA. The addition of UVA light activates a crosslinking reaction that effectively prevents DNA-RNA replication, transcription, and RNA translation, preventing cell division. The INTERCEPT process effectively inactivates more than 4 to 6 logs of enveloped and nonenveloped viruses, bacteria, protozoa, and WBCs, with some notable exceptions: nonenveloped viruses such as hepatitis A and spore-forming bacteria (bacillus) show a high degree of resistance. The treatment process reduces the levels of fibrinogen, FV, FVII, FVIII, and FX by 13% to 33%, although antithrombotic factors are generally preserved (<10% change), as is the VWF-cleaving protease activity (Table 1).

INTERCEPT plasma had been studied extensively before coming to market, including published in vitro and animal toxicology studies.34 Clinical development included autologous transfusion of treated plasma for warfarin reversal and an open-label multicenter trial in which 34 patients with congenital deficiencies in FI, FII, FV, FVII, FX, FXI, FXIII, or protein C were treated in a total of 102 transfusion episodes.12 In each case, INTERCEPT plasma effectively corrected the PT and aPTT, and in 10 patients who received treatment for active bleeding or prophylaxis for surgery, effective hemostasis was attained. Adverse events were monitored in this single treatment arm study. Urticarial rashes were the most common event and were recorded in 19 of 34 (56%) patients at least once during the course of multiunit therapy, but were generally mild and did not prevent the continuation of treatment.12

A RCT of INTERCEPT plasma versus FFP was performed in 121 patients with coagulopathy, mostly from liver disease, including 51 orthotopic liver transplants. In this complicated cohort of patients, INTERCEPT plasma demonstrated comparable correction of PT and aPTT, and no difference was noted in use of blood components, hemostasis, and safety.13 Specifically, there were six incidences of hepatic artery thrombosis, four in the control arm and two in the study arm. Finally, a RCT was reported of INTERCEPT plasma in 35 TTP patients, who were treated for up to two cycles of 35 days with study plasma.13 No difference in time to remission, relapse rates, total volume of blood products, and number of plasma exchange procedures was noted. In this study, 17 patients on the INTERCEPT plasma study arm received a mean of 11.3 TPE procedures and 165.4 units of plasma, representing a massive exposure to pathogen-reduced plasma. No antibodies were demonstrated to the amotosalen compound and no accumulation of drug was noted over time. The clinical experience with INTERCEPT plasma has been described in hemovigilance reports from Belgium and France, attesting to its equivalence to FFP in general clinical use.35,36

Riboflavin- and UV light–treated (Mirasol) plasma

Pathogen reduction utilizing a combination of riboflavin and UV light has been CE marked for distribution as the Mirasol plasma system. Single units of apheresis or whole blood plasma are treated and frozen within 8 hours of collection. The advantage of this process is the apparent lack of a need to remove excess riboflavin, as this is a natural compound with little known toxicity, and the chemistry and interaction with nucleic acids are well studied.37 Riboflavin and UV light damage nucleic acids by direct electron transfer, production of singlet oxygen, and the generation of hydroxyl radicals that damage DNA and RNA, interfering with replication, transcription, and RNA translation.

Pathogen reduction has been demonstrated for a wide range of enveloped and nonenveloped viruses and protozoa (>4-6 logs inactivation), although hepatitis A is resistant to inactivation and the demonstration of bacterial inactivation was dependent on extremely low concentrations of organisms at the time of treatment.14 Another caveat is that some of the inactivation studies were performed on Mirasol-treated PLTs, not plasma products, and utilized a variety of inactivation protocols. Mirasol treatment, like other pathogen inactivation processes, reduces the activity of various coagulation proteins, with the following mean residual activities: fibrinogen (77%), FII (80%), FVIIIc (75%), and FV (73%). Antithrombotic protein S, protein C, plasminogen, and α2-antiplasmin were retained at levels greater than 90% of untreated controls.14,18,38,39 Little data have been published on the clinical efficacy and safety of the Mirasol product, although it is reported to be in clinical use in some European countries. We await further information from clinical studies to better evaluate the risks and benefits of Mirasol plasma.

EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

The emergence of new plasma products, especially pathogen-reduced products, has required a more evidenced-based approach to assessing safety and efficacy; however, the evidence basis for plasma transfusion in general has never been formally established for most indications.40 Comparisons between existing and novel products have now detected differences that cause US regulatory agencies to require more stringent evaluation of both conventional and novel plasma products before coming to market. Some differences were investigated in the process of formal clinical trials (e.g., CPP vs. FFP in TTP), while others were identified through observational studies (S/D plasma and thrombosis).

FFP versus CPP in TPE for TTP

TTP is associated with increased circulating levels of high-molecular-weight VWF multimers, often secondary to a functional deficit of VWF-cleaving protease (ADAMTS-13).41,42 TPE was proven to be efficacious and superior to FFP transfusion in seminal studies.43 Given that CPP is depleted with respect to high-molecular-weight VWF, CPP was touted as the product of choice for TPE in these patients. At least three small RCTs attempted to demonstrate the superiority of CPP; however, only two trials are published as final reports.44-46 Zeigler and coworkers46 randomized 13 patients to TPE with FFP and 14 to TPE with CPP and no difference in outcomes were noted, including mortality (three deaths in each group), time to response, or proportion of patients that relapsed. This group went on to design a large definitive trial randomizing 236 patients; however, the study was terminated after 52 patients were enrolled, due to difficulties in recruitment and the availability of pathogen-reduced S/D plasma, viewed to be a more appropriate product for TPE.44 Analysis of the enrolled patients again did not support a statistical difference in outcomes with FFP or CPP. In this case, a laboratory-determined difference in the constituents of FFP and CPP has not proven to impact clinical outcomes and both products are considered acceptable for use for this indication.

S/D plasma and thrombosis

S/D plasma has undergone extensive study in both observational and RCTs and is generally considered as effective as FFP for all indications that require plasma transfusion. Some countries such as the United Kingdom specifically utilize S/D plasma for patients requiring large exposures, such as TTP patients undergoing TPE.25,47 Improved safety of a virally inactivated product, despite the pooling of multiple units during manufacture, is seen as a distinct advantage. In the case of the UK, S/D plasma is manufactured from plasma collected in countries with lower risk of variant Creutzfeldt-Jakob disease, to reduce the risk of possible exposure to prion pathogens. Nevertheless, the specter of an association with venous thrombosis has been raised in at least one retrospective study of TTP patients in Europe48 and in liver transplant case reports.49 The original licensing study for PLAS+SD in the United States also deserves more consideration: In this small study comparing PLAS+SD with FFP for TPE in TTP, 23 of 26 enrolled patients were evaluable.28 Five of five patients with TTP associated with stem cell transplant died during treatment, an outcome consistent with our current understanding that these patients are not responsive to TPE and have a high mortality rate. Of the remainder, 4 of 12 (25%) patients treated with PLAS+SD and zero of six (0%) control patients died on study. While not significant, it is unlikely that such data will be found acceptable by the regulatory authorities in the United States in future licensing trials. Other negative study findings also prove to be problematic. In the United States, Flamholz and coworkers50 reported an association of TPE in TTP with venous thrombosis in a small retrospective case series of three patients. Subsequently, a cluster of six deaths associated with pulmonary embolism in patients undergoing liver transplantation led the Food and Drug Administration (FDA) to mandate a black box warning that PLAS+SD is contraindicated in patients undergoing liver transplant and patients with severe liver disease and known associated coagulopathies. In addition, the warnings were strengthened to advise that patients receiving large volumes of PLAS+SD be monitored for evidence of thrombosis, excessive bleeding, or exacerbation of DIC. PLAS+SD was withdrawn from the market soon thereafter. In Europe, S/D plasma continues to be utilized in widespread practice after studies that failed to detect thrombotic complications in similar patient groups;25 however, the laboratory findings of decreased antithrombotic protein S and observational study evidence of thrombosis are causes for concern.

MB-treated plasma in general use and in the treatment of TTP

MB is known to affect the functional activity of fibrinogen. In one retrospective study performed in a single institution in Spain, usage of plasma was compared before and after MB plasma implementation. An aggregated 56% increase in plasma usage was noted and a twofold increase in nontreated cryoprecipitate was recorded in the first year, followed by a threefold increase in the second year after the introduction of the virally inactivated product. The authors conclude that this was probably due to the low hemostatic quality of MB plasma and questioned whether this increase was justified by the potential health benefits of viral inactivation.51 In a separate retrospective analysis of 56 TTP episodes treated with either MB (27 episodes) or FFP (29 episodes), multivariate regression analysis highlighted an increased risk of dying from progressive TTP (odds ratio [OR], 31; 95% confidence interval [CI], 1.2 to >100), a greater number of recurrences while on plasma exchange therapy (OR, 4.6; 95% CI, 1.2-17), and a lower probability of attaining sustained remission within 9 days (OR, 5.2; 95% CI, 1.3-20). The authors concluded that MB plasma may be less effective for the treatment of TTP than FFP and advised that it not be used for this indication unless RCTs demonstrated efficacy.52 These findings were subsequently confirmed in a small RCT study comparing quarantine FFP and MB plasma in 102 episodes of TTP. MB plasma required more plasma exchange procedures (median, 11 vs. 5; p = 0.002) and a greater plasma volume (485 mL/kg vs. 216 mL/kg; p = 0.007) and presented with more recrudescences (29 vs. 63; p = 0.2) than those receiving quarantine FFP.53 After adjustment for confounding factors, MB plasma was associated with a lower likelihood of remission by Day 8 (OR, 0.17; 95% CI, 0.06-0.47) and a higher risk of recrudescence (OR, 4.2; 95% CI, 1.6-10.8).53,54 More recently, reports of anaphylactic reactions to MB plasma, with demonstrated IgE-mediated MB-induced specificity55,56 have led the French regulatory authority, AFFSAPS, to announce the gradual withdrawal of the product from the market in that country. MB plasma continues to be used widely in other countries, despite these issues.

REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES

In the United States, there are no pathogen-reduced plasma products approved for transfusion by the regulatory authorities and this is seen by many as an unmet need. There is also interest in the industry to develop new forms of conventional products that will provide more ready access to FP24 derived from apheresis plasma collections (either concurrently with PLT collections or as stand-alone plasmapheresis procedures) and FP24 manufactured after overnight whole blood storage at room temperature.57 Apheresis FP24 would facilitate the collection of TRALI low-risk components from male donors, never-pregnant female donors, and HLA antibody test–negative donors, especially blood group AB, which is in constant short supply. Overnight room temperature storage would facilitate the manufacture of whole blood PLTs, in the face of continuing sporadic PLT shortages.58

Given the recent accumulating experience that highly manipulated plasma products (e.g., pathogen-reduced plasma) may have unforeseen adverse clinical outcomes, the US regulatory agencies have set an extremely high bar for approval of any new plasma product. In 2010, a series of meetings were held, orchestrated by the medical technology manufacturers' trade group, AdvaMed (Washington, DC). Manufacturers, blood collectors, and the FDA sought to explore expeditious routes for approval of RBCs, PLTs, and plasma manufactured from whole blood after an overnight room temperature hold.58 The primary driver in these talks was a desire to facilitate the manufacture of whole blood–derived PLTs, and the manufacturers hoped that the extensive experience in Europe with room temperature overnight hold, combined with in vitro evidence of equivalence,59,60 would permit the US regulatory agency to allow a streamlined approval for a simple change of whole blood overnight room temperature storage (as opposed to the current requirement of 4-6°C storage) conditions before separation of plasma from RBCs.

In response, the FDA expressed their minimal requirements for approval of plasma components. These included:

  • • 
    Each manufacturer would need to provide a full set of data for each combination of its collection sets, including collection and storage bags, leukoreduction filters, and additive solutions and/or anticoagulants.
  • • 
    A study should be designed as a randomized, crossover, paired study of 60 subjects who donate 2 units of whole blood, 8 weeks apart. The new product prepared from one collection should be compared with FFP from the other, from the same donor.
  • • 
    The minimum coagulation and antithrombotic factors to be examined are shown in Table 2. The FDA did not define acceptable outcomes for each variable.
  • • 
    The FDA reserved the right to request additional studies, up to and including clinical studies, based on the outcomes of the laboratory studies.
Table 2. FDA minimal requirements for approval of a novel plasma product
Randomized, crossover, paired studies for a novel plasma product derived from whole blood units with 60 subjects
Control: FFP (n = 60)Test plasma (n = 60)
• RBC and PLT counts• RBC and PLT counts
• PT• PT
• aPTT• aPTT
• FV• FV
• FVIIa• FVIIa
• FVIII:C• FVIII:C
• FXI• FXI
• VWF activity• VWF activity
• Antithrombin-III activity• Antithrombin-III activity
• Protein S• Protein S
• Protein C• Protein C
• Fibrinopeptide A, thrombin-antithrombin complex, or F1.2• Fibrinopeptide A, thrombin-antithrombin complex, or F1.2

These requirements set a very high standard for manufacturers to meet to bring novel products to the US market, including even minor changes to existing manufacturing conditions. Manufacturers are consequently increasingly unwilling to bear the costs and risk of submission of new data to the regulatory authorities for plasma products that are distributed as low-margin commodity products by blood collectors, are used interchangeably by clinicians, and have few differentiating claims that permit premium pricing. While it may be understandable that highly manipulated products (e.g., pathogen-reduced plasma) should be subject to close regulatory scrutiny, the current regulatory approach to approval of even trivial changes in manufacturing processes is stifling innovation and preventing improvements in patient treatment and safety in the United States. The prospect for pathogen-reduced plasma products being approved in the United States is consequently that much diminished.

REFERENCES

  1. Top of page
  2. Abstract
  3. GENERAL USE OF PLASMA PRODUCTS
  4. CHARACTERISTICS OF PLASMA PRODUCTS CURRENTLY APPROVED IN THE UNITED STATES
  5. PATHOGEN-REDUCED PLASMA PRODUCTS IN WIDESPREAD USE OUTSIDE OF THE UNITED STATES
  6. EVIDENCE ON THE INTERCHANGEABILITY OF PLASMA PRODUCTS IN GENERAL CLINICAL USE
  7. REGULATORY APPROACH TO APPROVING NEW PRODUCTS IN THE UNITED STATES
  8. CONFLICT OF INTEREST
  9. REFERENCES