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Skip to 0 minutes and 15 seconds Another very unique metabolic pathway is so-called receptor-mediated metabolism.

Skip to 0 minutes and 25 seconds It involves the interaction of therapeutic protein with membrane receptor of the target structure. And this is required to initiate response. After that, the metabolic enzyme is activated and metabolism follows as a way of elimination and inactivation of the biologics. This process is saturable and dose dependent. For example, Trastuzumab is an HER2 antagonist for breast cancer. With increasing dose, clearance increases, and half-life also, clearance decreases, sorry. And half-life increases leading to over exposure of the drug.

Skip to 1 minute and 24 seconds Here let’s look at the membrane receptor mediated metabolism.

Skip to 1 minute and 31 seconds So the drug binds with this receptor which activates the enzyme. And the drug or the biologics is metabolized after the receptor binding. So in effect, the receptor binding triggers the enzyme activity that activated or inactivated rather, the biologics, metabolize and inactivate the biologics. And receptor-mediated binding could be dose-dependent. Let’s look at another example. This is dose-dependent kinetics for a colony-stimulating factor, is a macrophage colony-stimulating factor. Let’s look at the plasma activity, following 0.1 milligram per kilo, 1 milligram per kilo, and 10 milligram per kilo. From the plasma activity curves, you can clearly tell that the kinetics is dose-dependent.

Receptor-Mediated Metabolism

Receptor-mediated metabolism is a unique elimination pathway for biologics. It initially entails an interaction of biologics with the membrane receptors on the target structure to elicit pharmacological response. Subsequently, the specific metabolic enzyme is activated to degrade the biologics. This process is saturable and therefore could be dose-dependent for some biologics.

These slides illustrate a unique elimination pathway called receptor-mediated metabolism. The mechanism entails an initial interaction of the biologics with the membrane receptors on the target structure to elicit the pharmacological response. Subsequently, the specific metabolic enzyme is activated to degrade the biologics. This process is enzyme limited and therefore could be dose-dependent; tratuzumab and an M-GCF are given as two examples.

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Pharmacotherapy: Understanding Biotechnology Products

Taipei Medical University