How often drugs advance through Phase 1, 2 and 3 to FDA approval — the industry benchmarks every biotech catalyst trader should know, and why phase data readouts move stocks. Facts, not advice.
Probability a program advances, by stage
Source: BIO / Informa Pharma Intelligence (Biomedtracker), "Clinical Development Success Rates" — 9,985 phase transitions across 7,455 programs. Figures are industry-wide averages; rates vary widely by therapeutic area.
The key numbers
Phase 1 → Phase 2~52% advance
Phase 2 → Phase 3 (hardest)~29% advance
Phase 3 → FDA filing~58% advance
FDA filing → approval~86–91%
Overall: Phase 1 → approval~8–10%
Lowest by area (oncology)~5%
Why Phase 2 is the graveyard
More drugs die in Phase 2 than anywhere else. Phase 1 mostly tests safety in a small group, so many programs clear it; Phase 2 is the first real test of whether the drug actually works (proof of concept) — and that's where roughly 7 in 10 programs fail. Phase 3 is expensive and pivotal, but a program that reaches it has already survived the hardest filter. That's why a Phase 2 readout is often the single most consequential data event in a small biotech's life.
What it means for catalyst traders
A clinical data readout is binary and idiosyncratic, like a PDUFA decision — and the smaller the company, the larger the stock reaction tends to be. Phase 2 proof-of-concept and Phase 3 pivotal readouts are the highest-stakes events; early Phase 1 signals move stocks less often but can still gap on a first look at efficacy. These are historical patterns and base rates — never predictions for any one trial. We're publishing our own quantified readout-reaction dataset (real stock moves by phase and company size) alongside a live readout calendar — coming soon.
What percentage of Phase 3 clinical trials succeed?
Per BIO/Informa's Clinical Development Success Rates analysis, about 58% of Phase 3 programs advance to an FDA filing. Of those filed, the FDA ultimately approves roughly 86-91%.
Which clinical trial phase has the lowest success rate?
Phase 2 is the hardest stage — only about 29% of Phase 2 programs advance to Phase 3. It's where proof-of-concept most often fails (the industry's "valley of death").
What is the overall drug approval success rate from Phase 1?
About 8-10% of drugs that enter Phase 1 are ultimately approved (BIO cites ~7.9-9.6% cumulative). It is lowest in oncology (~5%) and higher in areas like hematology.