Factor VIII PEGylation and Glycosylation

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.

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.