Core1: Stages of drug development in brief

💡 High-yield / 要点：Drug development = Preclinical → Phase 1 → Phase 2 → Phase 3 → NDA review → Phase 4. Goal is to prove safety + efficacy + acceptable risk/benefit before and after approval.

Overall / 全体像

• Development usually takes 8–12 years and may cost $1–2 billion per drug.
• Flow: lead compound → preclinical testing → IND → clinical trials → NDA → marketing/post-market surveillance.
• Main evaluation axes: mechanism of action, PK, PD, toxicity, efficacy, safety.

Preclinical / 前臨床

• Done before human trials.
• Uses in vitro studies + animal testing.
• Checks:
  • MOA / 作用機序
  • PK / 薬物動態
  • PD / 薬力学
  • toxicity / 毒性
  • expected safe dose range
• Purpose: decide whether the candidate is safe enough to enter clinical trials.

Clinical phases / 臨床試験

Phase	Main subjects	Main question	Key point
Phase 1	Healthy volunteers, small number	Is it safe?	Safety, tolerability, PK, dose/dosing regimen
Phase 2	Patients with target disease	Does it work?	Efficacy + safety; informs Phase 3 design
Phase 3	Large patient population	Does it work reliably?	Randomized, double-blind, placebo-controlled; confirms safety/efficacy and risk/benefit
Phase 4	Real-world users after approval	What happens long-term?	Post-market surveillance, rare adverse effects, long-term safety/effectiveness

Regulatory review / 承認審査

• After successful Phase 3, the company submits an NDA / New Drug Application.
• Regulatory agency such as the FDA reviews whether benefits outweigh risks.
• If approved, the drug can be marketed, but monitoring continues in Phase 4.

Example / 例

• Sofosbuvir: antiviral drug for chronic HCV infection.
• Approved by the FDA in 2013 after preclinical and clinical studies showed efficacy and safety.

Remember / 覚え方

• Preclinical = “Can we try it in humans?”
• Phase 1 = “Is it safe?”
• Phase 2 = “Does it work in patients?”
• Phase 3 = “Can we prove it in many patients?”
• Phase 4 = “Is it still safe in the real world?”