AprotininBrian Minarcik, DO January 24, 2014

GoalsAprotinin

Pharmacology

Mangano study

Costs and profits

Lysine analogs

Future of Aprotinin

Pharmacologic approaches to reduce bleeding and transfusion in cardiac surgical patients are based on either preventing the defects associated with the CPB induced coagulopathy

Different pharmacologic agents have been reported, however the currently accepted pharmacologic interventions are based on using a protease inhibitor, aprotinin, or lysine analogs to inhibit fibrinolysis

HistoryInitially named "kallikrein inactivator", aprotinin was first isolated from

cow parotid glands in 1930 and purified from bovine lung in 1964

As it inhibits pancreatic enzymes, it was initially used in the treatment

for acute pancreatitis in which destruction of the gland by its own

enzymes is thought to be part of the pathogenesis

Named BPTI - Bovine Pancreas Trypsin

Inhibitor

Because it is a small, stable protein whose

structure had been determined at high

resolution by 1975, it was the first

macromolecule of scientific interest to be

simulated using molecular dynamics

computation, in 1977

BPTI was the cover image on a protein

folding compendium volume by Thomas

Creighton in 1992

HistoryThis serine protease inhibitor has a long history of use in clinical

medicine including its use in cardiac surgery as far back as in the 1960s

Aprotinin (Trasylol) is a serine protease inhibitor derived from bovine lung that inhibits trypsin, chymotrypsin, plasmin, tissue plasminogen activator, and kallikrein

Although aprotinin was studied in the 1960's, low doses were evaluated in an effort to treat bleeding after cardiac surgery rather than to prevent it

However, it was not until the late 1980's that prophylactic use was reported

AprotininThere was a resurgence of interest

in aprotinin in the 1980s following the reports from the United Kingdom by Royston who demonstrated its blood-sparing effects during cardiac surgery

In 1987 Van Oeveren reported a 47% reduction in blood loss in patients receiving aprotinin during CABG surgery

In 22 patients having reoperations with bubble oxygenators, Royston developed a pharmacologic approach to inhibit inflammatory responses during CPB administering a loading dose of 2 million units of aprotinin following intubation, and a continuous infusion of 500,00 units/hour with a CPB pump prime dose of 2 million units

Studying Aprotinin’s EfficacyDietrich found decreased blood loss in patients receiving aprotinin as

compared to those receiving placebo (738 ml vs. 1431 ml) for primary CABG

He also reported less formation of thrombin, fibrin, split products, and D-dimers in patients receiving aprotinin

Separate studies by Blauhut, Havel, Lemmer, and Marx have all confirmed decreased blood loss in patients receiving aprotinin at high doses

Aprotinin also reduced blood loss 49-75% and transfusion requirements from 49-77% in three studies in patients receiving aspirin

Studying Aprotinin’s EfficacyIn redo CABG patients, Cosgrove reported 171 patients who received either high dose aprotinin, low dose aprotinin, or placebo

They found that low dose aprotinin was as effective as high dose aprotinin in decreasing blood loss and blood transfusion requirements

Levy found that transfusion of allogenic packed RBC's was significantly less in the aprotinin-treated patients compared to the placebo (high dose: 1.6 units, low dose: 1.6 units, pump prime only: 2.5 units, placebo: 3.4 units), with even greater reductions in total blood product exposure in high dose and half dose groups compared to placebo or pump prime cohorts

There were no differences in treatment groups for the incidence of perioperative MI, and the incidence of stroke was lower in the aprotinin treated patients.

Antifibrinolytic Agents Studied

Most of the early studies using antifibrinolytic agents showed decreased mediastinal drainage in patients treated with AmicarHowever, many of these studies lacked controls, were retrospective, and not blinded

In 350 patients undergoing CABG, Del Rossi reported using a low dose of amicar a significant decrease in mediastinal drainage and RBC transfusion with no difference in MI or stroke

Vander Salm reported a reduction in chest tube drainage in 51 patients who received Amcar, no differences in platelet function between Amicar and the placebo group, and no differences in blood transfusion

Horrow studied TA given in a prophylactic manner prior to skin incision for primary CABG showing 12 hour postop blood loss was 496 ml in the TA group compared to 750 ml in the placebo group. However, transfusions were not different

Studying Aprotinin’s EfficacyFavorable results from randomized, double-blind and placebo-controlled trials in the United States led to the approval of aprotinin by the FDA in 1993 for patients undergoing re-op CABG surgery or for those at high-risk for excessive bleeding

This approval was later extended to all CABG patients in 1998.

PharmacologyAprotinin is a broad spectrum protease inhibitor which modulates the

systemic inflammatory response associated with CPB

Aprotinin, through its inhibition of multiple mediators [e.g., kallikrein, plasmin] results in the attenuation of inflammatory responses, fibrinolysis, and thrombin generation

Aprotinin inhibits pro-inflammatory cytokine release and maintains glycoprotein homeostasis

In platelets, aprotinin reduces glycoprotein loss (e.g., GpIb, GpIIb/IIIa), while in granulocytes it prevents the expression of pro-inflammatory adhesive glycoproteins (e.g., CD11b)

PharmacologyThe effects of aprotinin use in CPB involves a reduction in inflammatory response which translates into a decreased need for allogeneic blood transfusions, reduced bleeding, and decreased mediastinal re-exploration for bleeding

Aprotinin inhibits several serine proteases, specifically trypsin, chymotrypsin and plasmin at a concentration of about 125,000 IU/ml, and kallikrein at 300,000 IU/ml

Its action on kallikrein leads to the inhibition of the formation of factor XIIa

As a result, both the intrinsic pathway of coagulation and fibrinolysis are inhibited

PharmacologyIts action on plasmin independently slows fibrinolysis.

Aprotinin is slowly degraded by lysosomal enzymes.

Following a single IV dose of radiolabelled aprotinin, approximately 25-40% of the radioactivity is excreted in the urine over 48 hours. After a 30 minute infusion of 1 million KIU, about 2% is excreted as unchanged drug. After a larger dose of 2 million KIU infused over 30 minutes, urinary excretion of unchanged aprotinin accounts for approximately 9% of the dose

The Risk Associated with Aprotinin in Cardiac Surgery Mangano NEJM 2006

Antifibrinolytic therapy to limit blood loss

Observational study of 4374 patients undergoing revascularization with 3 agents

Aprotinin (1295)

Aminocaproic acid (883)

Tranexamic Acid (882)

No agent (1374)

MANGANO 69 institutions in North and

South America, Europe, the Middle East, and Asia

Each outcome event was prespecified, defined by the protocol, and classified as cardiovascular (MI or heart failure), cerebrovascular (stroke, encephalopathy, or coma), or renal (dysfunction or failure)

MANGANOOverall, the use of aprotinin was associated with an increased risk of renal and

nonrenal events when compared with aminocaproic acid, tranexamic acid, or no antifibrinolytic therapy a finding confirmed by multivariable logistic regression

Interaction by drug group and complexity of surgery was not significant

The three medications reduced blood loss to similar extents

EBL

827±573 ml in the control group

753±660 ml in the aprotinin group (P<0.001)

719±578 ml in the aminocaproic acid group (P<0.001)

676±741 ml in the tranexamic acid group (P<0.001)

Unlike lysine analogues, aprotinin has high affinity for the kidneys

After free glomerular passage, aprotinin binds selectively to the brush border of the

proximal tubule membrane, and then, by pinocytosis, it enters into and accumulates

within the cytoplasm, inhibiting tubule protease secretion, prostaglandin and renin

synthesis, prostasin secretion, and bradykinin release.

A dose-dependent renal afferent vasoconstriction; deep cortical and medullary perfusion

and its autoregulation are thereby impaired, and focal tubular necrosis ensues

Because of Aprotinin’s interference with the synthesis and release of endothelial nitric

acid, aprotinin also may instigate macrovascular or microvascular thrombosis

The Financial life of Aprotinin

FDA approval 1993

Sales:

$300 Million in 2005

$225 Million in 2006

$135 Million in 2007

Withdrawn from market November 2007

That research concluded that halting the drug’s use would prevent 10,000 to 11,000 cases of kidney failure a year and save more than $1 billion a year in dialysis costs.

Lysine Analogs

Amicar and tranexamic acid are derivatives of the amino acid lysine

Both of these drugs inhibit the proteolytic activity of plasmin and the conversion of plasminogen to plasmin by plasminogen activators

Plasmin cleaves fibrinogen and a series of other proteins involved in coagulation

Tranexamic acid is 6 to 10 times more potent than e-aminocaproic acid

Lysine Analogs

After the withdrawal of aprotinin from the market, tranexamic acid and ɛ-

aminocaproic acid are the agents of choice for this indication and are used

routinely in most centers worldwide

Both agents are effective in reducing blood loss after cardiac surgery when

used prophylactically, which has been demonstrated in recent meta-

analyses

Lysine Analogs

The blood sparing effect of the lysine analogues was also shown in the

Mangano study and in the BART trial, even though there was a trend towards

aprotinin being more efficacious to prevent massive bleeding compared with

both lysine analogues combined (RR 0.79; 95% CI 0.61–1.01)

However, the BART trial was ultimately not adequately powered to determine

the superiority of aprotinin because of early termination.

Lysine Analogs

Comparing the two lysine analogues directly, tranexamic acid seems to reduce

blood loss more effectively than ɛ-aminocaproic acid, but only retrospective

data are available to support this

Therefore, a recommendation to use one of the lysine analogues in preference

to the other cannot be made based on the existing literature

European Medicines Agency recommends lifting suspension of aprotinin

Review finds that benefits of all antifibrinolytic medicines outweigh risks in restricted range of indications

This follows a full review of the benefits and risks of all antifibrinolytic medicines, which found that the results of the BART study on which the suspension was based are unreliable.

The Committee found that there were a number of problems with the way the BART study was conducted, which cast doubt on the previous conclusions

These included the imbalances in the way blood-thinning medicines such as heparin were used, inappropriate monitoring of the use of these medicines and how problems with the way that data from some patients were excluded from the initial analysis

The Committee found that the BART study’s results were not replicated in other studies and that the overall data available showed that aprotinin’s benefits are greater than its risks in the restricted indication

ReferencesMangano DT, Tudor IC, Dietzel C (2006). "The risk associated with aprotinin in cardiac surgery". N. Engl. J. Med. 354 (4): 353–65. doi:

10.1056/NEJMoa051379.PMID 16436767

Mahdy AM, Webster NR (2004). "Perioperative systemic haemostatic agents". British journal of anaesthesia 93 (6): 842–58. doi:10.1093/bja/aeh227.PMID 15277296.

Anesthesia & Analgesia:November 2006 - Volume 103 - Issue 5 - pp 1067-1070

Aprotinin Use During Cardiac Surgery: A New or Continuing Controversy?