The correct answer to this open question is the following.
You forgot to include the options for this question. However, we can answer the following.
The single amino acid substitution the drug company should try to implement is leucine in place of methionine.
Leucine is what the drug company wants to target as an internal amino acid in the inhibitor.
Leucine is an amino acid used to catalyze proteins. For the human body, leucine is an important component that must be obtained by the food we eat. That is why in our daily good nutrition habits we have to include proteins, beans, dairy products, varied legumes, and meat.