Life has been rather busy lately, but I have been using my spare time to learn new things too. Having come from a background working mostly with small molecules, I have decided to take some time to learn about the PK of biologics too. I spent the past week learning about the PK of antibodies. Let me share with you some of my learnings with you!

Most antibodies tend to follow a 2 compartment PK, with a distribution and elimination phase. Unlike small molecules where total clearance can generally be lumped under a single term of CL, however, antibody PK can be described using 2 terms for clearance instead. This is because antibodies tend to have 2 distinct clearance pathways – a linear clearance pathway via either elimination or catabolism in cells, and a saturable clearance pathway with targeted antigen mediated clearance. As there are 2 clearance pathways instead of 1, this can make the elimination slope of the antibody with saturated clearance very different from that of a small molecule with saturated clearance.

Check out the RShiny app to try adjusting the parameters yourself!
https://janicegoh.shinyapps.io/AntibodyPK/

Hope you learnt something with me! Feel free to add in your suggestions on what other non-small molecule therapeutics are important to learn about too, and if I missed out any important points in this explanation.