Weekly Reflection

This week, we have learnt PK differences between small molecules and therapeutic proteins; difference in absorption between small molecule and therapeutic proteins; the effects of macromolecule binding on distribution and elimination of protein and peptide drugs; the renal excretion of large molecules; the hepatic metabolism of large molecules; the effects of immunogenic response on PK of therapeutic proteins; the structural modifications to change the PK of peptide or protein drugs; and PK/PD models and correlations for therapeutic proteins.

Here are some key points for you to review what you have learnt this week. There is no need to answer them all. You could use these to check the gist of this week.

1. Define in general terms the difference between pharmacokinetics, pharmacodynamics and PK-PD correlation. What parameters (variables) are measured in characterizing PK, PD and PK-PD correlation for biologics.

2. Contrast small molecule drugs and large molecules proteins in terms of absorption, distribution, metabolism, excretion, and overall elimination process.

3. Contrast small molecule drugs and large molecule proteins in terms of pharmacology, biochemistry and formulation. Would that suggest to you that “biosimilarity” requirements will be more stringent than generic bioequivalence?

4. Analyze the five models that have been used to depict the PK-PD correlation for drugs or biologics. What is the difference between the direct link model and indirect link model, with regard to the site of action being in the central or peripheral compartment?