Answer:
4. agents should act against the pathogen and not the host.
Explanation:
A chemotherapeutic chemical should exhibit selective toxicity. This chemical should target the specific chemicals or the processes exhibited by the pathogen only so that the host cells are not adversely affected. This is called selective toxicity. To exhibit selective toxicity, drugs are designed in such a way that the pathogen-specific vital pathways and molecules are affected.
For example, human cells lack peptidoglycan which in turn is a major constituent of bacterial cell walls. Therefore, a drug with selective toxicity can target the synthesis and/ or stability of peptidoglycan.
