Compound optimization. Four compounds are evaluated for characteristics including the IC50, log(P), and cmax (the maximal concentration of compound present) measured in the serum of dogs. The compound shown at the bottom (highlighted in yellow) has the weakest inhibitory power (measured by IC50) but by far the best bioavailability (measured by cmax). This compound was selected for further development, leading to the drug indinavir (Crixivan).