Aprotinin

1. Aprotinin Brian Minarcik, DO January 24, 2014

2. Goals Aprotinin Pharmacology Mangano study Costs and profits Lysine analogs Future of Aprotinin

3. 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

4. History Initially 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

5. 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

6. History This 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

7. There 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 Aprotinin

8. Studying Aprotinin’s Efficacy Dietrich 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

9. Studying Aprotinin’s Efficacy In 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.

10. Antifibrinolytic Agents Studied Most of the early studies using antifibrinolytic agents showed decreased mediastinal drainage in patients treated with Amicar However, 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

11. Studying Aprotinin’s Efficacy Favorable 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.

12. Pharmacology Aprotinin 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)

13. Pharmacology The 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

14. Pharmacology Its 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

17. 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)

18. 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)

20. MANGANO Overall, 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)

23. 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

25. 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. The Financial life of Aprotinin FDA approval 1993 Sales: $300 Million in 2005 $225 Million in 2006 $135 Million in 2007

26. 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

27. 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

28. 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.

29. 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

30. 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

31. References Mangano 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.PMID16436767 Mahdy AM, Webster NR (2004). "Perioperative systemic haemostatic agents". British journal of anaesthesia93 (6): 842–58. doi:10.1093/bja/aeh227.PMID15277296. Anesthesia & Analgesia: November 2006 - Volume 103 - Issue 5 - pp 1067-1070 Aprotinin Use During Cardiac Surgery: A New or Continuing Controversy?