The degree to which a treatment or intervention achieves its intended purpose or produces the desired outcomes. In this case, it refers to how well the new drug treats the particular condition.
Related terms
Treatment efficacy: Refers to how well a treatment works under ideal conditions.
Side effects: Unintended and often unwanted effects that can occur as a result of taking a medication.
Placebo effect: The phenomenon where patients experience improvement in their condition simply because they believe they are receiving an effective treatment.