The docking of Ritonavir to CYP 3A4 results in an extremely high PLP docking score, 142. This confirms its use as an effective inhibitor. It essentially fills the entire cavity adjacent to the heme iron frame, see Figure . Note that it has 50 heavy atoms and its size is primarily responsible for the high PLP docking (interaction) score. Per atom the score is 2.56, which is high, but the filling of the cavity and the number of atoms is the primary reason for its large interaction with CYP 3A4. By contrast, Nirmatrelvir has 35 atoms, a score of 84.11, and a similar score per atom of 2.41 to CYP 3A4.