Understanding Clinical Trial Phases

From laboratory to pharmacy shelf: Learn how treatments are tested for safety and effectiveness through each phase of clinical research.

10-15 Year Process$1-3 Billion Investment<10% Success Rate

The Journey from Lab to Patient

Preclinical Research

3-6 years • Lab & animal testing

Lab
I

Phase I

1-2 years • 20-100 volunteers

Phase II

2-3 years • 100-300 patients

II
III

Phase III

3-4 years • 300-3,000 patients

FDA Review

6 months - 1 year

FDA
IV

Phase IV

Ongoing • Thousands of patients

Each Phase in Detail

Pre

Preclinical Research

Before testing in humans, researchers spend years in the laboratory

What Happens

  • • Laboratory testing
  • • Cell culture studies
  • • Animal testing
  • • Toxicity evaluation
  • • Dosage determination

Key Goals

  • • Identify promising compounds
  • • Understand mechanism of action
  • • Assess basic safety
  • • Determine starting dose

Success Rate

Only 1 in 5,000 discovered compounds make it to human testing

0

Phase 0 (Exploratory)

Optional micro-dosing studies to gather preliminary data

Participants

10-15 volunteers

Very low doses (1% of therapeutic dose)

Duration

Several days to weeks

Single or few doses only

Purpose

  • • Drug absorption
  • • Target engagement
  • • Early pharmacokinetics
I

Phase I - Safety & Dosage

First testing in humans to establish safety and dosing

Participants

20-100 people

Healthy volunteers or patients

Duration

Several months

Often inpatient stays

Key Questions

  • • Is it safe?
  • • What's the right dose?
  • • How does the body process it?

Success Rate

70% of drugs pass Phase I

High compensation for volunteers

For Participants: Intensive monitoring, frequent blood draws, ECGs, and vital sign checks. May require dietary restrictions and overnight stays.

II

Phase II - Efficacy & Side Effects

Testing whether the treatment works while monitoring safety

Participants

100-300 patients

With the target condition

Duration

Several months to 2 years

Regular clinic visits

Key Questions

  • • Does it work?
  • • What are side effects?
  • • Optimal dosing schedule?

Success Rate

33% of drugs pass Phase II

May be randomized/controlled

Phase IIa

Dose-ranging studies to find optimal dose

Phase IIb

Efficacy studies at selected doses

III

Phase III - Confirmation & Comparison

Large-scale testing to confirm effectiveness vs. standard treatment

Participants

300-3,000 patients

Multiple locations

Duration

1-4 years

Long-term follow-up

Key Questions

  • • Better than existing?
  • • Rare side effects?
  • • Different populations?

Success Rate

25-30% pass Phase III

Required for FDA approval

Design Features: Randomized, double-blind, placebo or active-controlled. Multi-center trials across different geographic regions and demographics.

IV

Phase IV - Post-Market Surveillance

Ongoing monitoring after FDA approval and market release

Participants

Thousands of patients

General population

Duration

Ongoing indefinitely

Years to decades

Key Questions

  • • Long-term effects?
  • • Rare adverse events?
  • • Real-world effectiveness?

Importance

Detects rare side effects

May lead to new uses

For Patients: Your doctor may offer participation in Phase IV studies for newly approved treatments. This provides access to new therapies with additional monitoring.

The Clinical Trial Funnel

5,000-10,000 CompoundsPreclinical
5-10 Enter TrialsPhase I
2-3 ContinuePhase II
1-2 ProgressPhase III
1 ApprovedFDA

Only 1 in 5,000 discovered compounds make it to market. The entire process takes 10-15 years and costs $1-3 billion.

Special Trial Designations

Fast Track

Expedited Development

For serious conditions with unmet medical needs. More frequent FDA meetings and accelerated approval possible.

Breakthrough

Breakthrough Therapy

For drugs showing substantial improvement over existing treatments. Priority review and intensive FDA guidance.

Orphan Drug

Rare Disease Focus

For conditions affecting fewer than 200,000 people. Tax credits, grant funding, and 7-year market exclusivity.

Priority Review

Faster FDA Review

6-month review instead of standard 10-12 months for drugs addressing significant unmet medical needs.

Accelerated

Conditional Approval

Approval based on surrogate endpoints with requirement for confirmatory trials post-approval.

Pediatric

Children's Studies

Special protections and requirements for trials involving children, with additional market exclusivity incentives.

Find the Right Trial Phase for You

Whether you're seeking early access to innovative treatments or want to contribute to medical research, understanding trial phases helps you make informed decisions.