Factor VIII PEGylation and Glycosylation

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Questions and Answers

What is the main reason for shortening the protein alterplase?

To enhance its fibrin selectivity

To reduce its production cost

To increase its glycosylation

To improve its half-life (correct)

Why is reteplase produced in E. coli?

Because it is a more expensive process

Because it enhances its catalytic activity

Because it is a simpler and cheaper process than producing in CHO cells (correct)

Because it allows for glycosylation

What is the advantage of Tenecteplase over alterplase?

It is produced in E. coli

It has a shorter half-life

It has a longer half-life and increased resistance to PAI-1 (correct)

It is cheaper to produce

Why is streptokinase preferred over t-PA?

Because it is cheaper to produce Signup and view all the answers

What is the function of streptokinase?

To activate plasminogen into plasmin Signup and view all the answers

What is the source of urokinase?

Human urine Signup and view all the answers

Why is t-PA an expensive drug?

Because its production in cell culture is a difficult and expensive process Signup and view all the answers

What is the advantage of glycosylation in Tenecteplase?

It increases its resistance to PAI-1 Signup and view all the answers

What is the primary reason for the prolonged half-life of recombinant factor VIII?

PEGylation prevents binding to receptors on hepatocytes. Signup and view all the answers

Why is glycosylation important for recombinant factor VIII?

It ensures proper function and activity of the protein. Signup and view all the answers

What can happen if a patient develops antibodies against factor VIII?

Factor VIII can no longer perform its function. Signup and view all the answers

At what temperature should factor VIII be produced and stored to prevent degradation?

4° Signup and view all the answers

Which modification could potentially increase the half-life of factor VIII?

Deletion of the B-domain. Signup and view all the answers

What is one major challenge in producing recombinant factor VIII?

Limiting its immunogenicity. Signup and view all the answers

What alternative factors might be administered if factor VIII therapy is ineffective due to immune response?

Factor VIIa or factor Xa. Signup and view all the answers

What characteristic of factor VIII makes its production particularly challenging?

It is a large and unstable molecule. Signup and view all the answers

What is the primary function of tissue plasminogen activator (tPA) in the treatment of thrombosis?

To dissolve existing blood clots by activating plasminogen Signup and view all the answers

Which of the following statements accurately describes the production of tissue plasminogen activator (tPA)?

tPA is produced in a genetically engineered mammalian cell line, similar to Xigiris Signup and view all the answers

Why is tPA's half-life so short?

tPA is rapidly taken up by the liver and metabolized Signup and view all the answers

What is the primary reason for the development of modified forms of tPA?

To overcome the size limitations of tPA, allowing for easier delivery to target sites Signup and view all the answers

What is the main difference between tPA and Xigiris?

tPA is used to treat thrombosis, while Xigiris is used to treat sepsis Signup and view all the answers

What is the role of protein C in preventing blood clot formation?

It inactivates specific clotting factors, reducing the coagulation cascade Signup and view all the answers

How does the presence of gamma-carboxyglutamate and beta-hydroxylated residues in Xigiris contribute to its function?

These residues are essential for the enzymatic activity of Xigiris, enabling it to inactivate clotting factors Signup and view all the answers

Which of the following is NOT a potential application for thrombolytic agents like tPA?

Treatment of deep vein thrombosis (DVT) in the legs Signup and view all the answers

Study Notes

Factor VIII and Its Modifications

Factor VIII has a prolonged half-life due to altered degradation processes, specifically through PEGylation, which prevents binding to hepatic receptors.
Recombinant factor VIII, also known as factor VIIIC, is produced in eukaryotic cells like CHO and BHK to ensure proper glycosylation, as it has 25 potential glycosylation sites critical for function.
Due to long-term treatment needs, some patients develop antibodies against factor VIII, leading to ineffective therapy; alternative treatments include factor Xa or factor VIIa.
Temperature sensitivity of factor VIII necessitates production and storage at 4°C to prevent degradation.
Research focuses on improving factor VIII through B-domain deletions and other modifications to enhance half-life, secretion, potency, and reduce immunogenicity.

Protein C and Its Treatment

Protein C is vital in preventing clot formation; Xigiris is a recombinant human activated protein C designed to treat severe sepsis and minimize organ failure due to clotting.

Thrombolytic Agents Overview

Thrombolytic agents dissolve fibrin clots and are used for acute myocardial infarction, ischemic stroke, peripheral arterial thrombosis, pulmonary embolism, and occluded hemodialysis shunts.

Tissue Plasminogen Activator (tPA)

tPA is the most commonly used thrombolytic drug, a serine protease naturally found in endothelial cells, and was the first recombinant protein produced in goat milk, not marketed.
It activates plasminogen to plasmin, facilitating the breakdown of fibrin clots, and exhibits a short half-life of just 3 minutes due to its 527 amino acid length.
Modifications of tPA include reteplase, a shorter version at 335 amino acids with a half-life of 20 minutes, allowing for single bolus administration; it is non-glycosylated and produced in E. coli.
Tenecteplase, produced in CHO cells with 6 amino acid differences, has a 15-19 minute half-life and increased resistance to PAI-1 due to glycosylation.
tPA production is costly, rendering it an expensive treatment compared to alternatives.

Competitive Thrombolytics

Streptokinase, derived from Streptococcus haemolyticus, is an inexpensive thrombolytic agent that activates plasminogen but may provoke immune responses; it is preferred for its low cost and ease of purification.
Urokinase, another serine protease, functions similarly to tPA and is collected from human urine.

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Description

This quiz covers the prolonged half-life of factor VIII due to PEGylation, its degradation in hepatocytes, and the importance of glycosylation in eukaryotic cells.