To be sure, virtually all medical drugs have some kind of off-target activity, and as long as the intended on-target benefits outweigh those risks, physicians and regulators are generally pretty forgiving. For instance, antibiotics kill off both pathogenic bacterial strains and beneficial strains, and chemotherapy drugs kill off both cancerous cells and healthy cells. The challenge is ultimately one of specificity: developing a drug that is so closely matched to its intended target that a few atoms out of place will weaken the interaction enough to prevent the drug from causing unintended
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