What percentage of compounds that show suitable biological activity go through clinical trials and reach the market?

• A. less than 10%
• B. about 40%
• C. about 70%
• D. more than 90%

Answer: (A)

The main idea here is how tough the drug development funnel is: many compounds show initial biological activity, but only a very small fraction become medicines. After a compound shows activity, it must pass extensive safety and pharmacokinetic assessments, then go through three clinical trial phases to prove safety and efficacy in humans. Across these stages, failures are common due to safety concerns, insufficient efficacy, or dosing and optimization issues. Because of this steep attrition, the share that actually makes it from discovery to an approved market drug is quite small—typically less than 10%. The other percentages would imply far higher success rates than what is observed in real-world development, where only a minority of candidates reach the market.