Aprotinin

 ( Antifibrinolytics ) 

Thrombosis, presumably from overactive inhibition of the fibrinolytic system, may occur at a higher rate, but until 2006 there was limited evidence for this association. Similarly, while biochemical measures of renal function were known to occasionally deteriorate, there was no evidence that this greatly influenced outcomes. A study performed in cardiac surgery patients reported in 2006 showed that there was indeed a risk of acute renal failure, myocardial infarction and heart failure, as well as stroke and encephalopathy. The study authors recommend older antifibrinolytics (such as tranexamic acid) in which these risks were not documented. The same group updated their data in 2007 and demonstrated similar findings.

In September 2006, Bayer A.G. was faulted by the FDA for not revealing during testimony the existence of a commissioned retrospective study of 67,000 patients, 30,000 of whom received aprotinin and the rest other anti-fibrinolytics. The study concluded aprotinin carried greater risks. The FDA was alerted to the study by one of the researchers involved. Although the FDA issued a statement of concern they did not change their recommendation that the drug may benefit certain subpopulations of patients. In a Public Health Advisory Update dated October 3, 2006, the FDA recommended that "physicians consider limiting Trasylol use to those situations in which the clinical benefit of reduced blood loss is necessary to medical management and outweighs the potential risks" and carefully monitor patients.

On October 25, 2007, the FDA issued a statement regarding the "Blood conservation using antifibrinolytics" (BART) randomized trial in a cardiac surgery population. The preliminary findings suggest that, compared to other antifibrinolytic drugs (epsilon-aminocaproic acid and tranexamic acid) aprotinin may increase the risk of death. On October 29, 2006 the Food and Drug Administration issued a warning that aprotinin may have serious kidney and cardiovascular toxicity. The producer, Bayer, reported to the FDA that additional observation studies showed that it may increase the chance for death, serious kidney damage, congestive heart failure and strokes. FDA warned clinicians to consider limiting use to those situations where the clinical benefit of reduced blood loss is essential to medical management and outweighs the potential risks. On November 5, 2007, Bayer announced that it was withdrawing Aprotinin because of a Canadian study that showed it increased the risk of death when used to prevent bleeding during heart surgery.

Two studies published in early 2008, both comparing aprotinin with aminocaproic acid, found that mortality was increased by 32 and 64%, respectively. One study found an increased risk in need for dialysis and revascularisation.

No cases of bovine spongiform encephalopathy transmission by aprotinin have been reported, although the drug was withdrawn in Italy due to fears of this.

In cell biology aprotinin is used as an enzyme inhibitor to prevent protein degradation during lysis or homogenization of cells and tissues.

Aprotinin can be labelled with fluorescein isothiocyanate. The conjugate retains its antiproteolytic and carbohydrate-binding properties and has been used as a fluorescent histochemical reagent for staining glycoconjugates (mucosubstances) that are rich in uronic or sialic acids.

BPTI is one of the most thoroughly studied proteins in terms of structural biology, experimental and computational dynamics, mutagenesis, and protein folding. It was one of the earliest protein crystal structures solved, in 1970 in the laboratory of Robert Huber, and it's substrate-like interaction mode deciphered in the context of the bovine trypsin complex in 1974. It later also became famous being the first protein to have its structure determined by NMR spectroscopy, in the laboratory of Kurt Wuthrich at the ETH in Zurich in the early 1980s.

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 by J. Andrew McCammon and Bruce Gelin, in the Martin Karplus group at Harvard. That study confirmed the then-surprising fact found in the NMR work that even well-packed aromatic sidechains in the interior of a stable protein can flip over rather rapidly (microsecond to millisecond time scale). Rate constants were determined by NMR for the hydrogen exchange of individual peptide NH groups along the chain, ranging from too fast to measure on the most exposed surface to many months for the most buried hydrogen-bonded groups in the center of the β sheet, and those values also correlate fairly well with degree of motion seen in the dynamics simulations.

BPTI was important in the development of knowledge about the process of protein folding, the self-assembly of a polypeptide chain into a specific arrangement in 3D. The problem of achieving the correct pairings among the 6 Cys sidechains was shown to be especially difficult for the two buried, close-together SS near the BPTI chain termini, requiring a non-native intermediate for folding the mature sequence in vitro (it was later discovered that the precursor sequence folds more easily in vivo). BPTI was the cover image on a protein folding compendium volume by Thomas Creighton in 1992.