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Clinical Trials: Phase I, II and III

Beginner

Kurz erklärtA drug candidate must pass through three clinical phases: Phase I tests safety, Phase II tests whether the drug works in principle, and Phase III tests efficacy at scale. The later the phase, the higher the probability of success — and the higher the share price tends to be.

Definition

Clinical trials are the prescribed process by which a drug must demonstrate its safety and efficacy before a regulator can grant approval. For investors in small-cap biotech stocks, the trial calendar is often the single most important driver of the share price.

Phase I — Safety

A few dozen participants, often healthy volunteers. The aim is to establish whether the drug is well tolerated and how the body processes it. Passing Phase I says almost nothing about whether the drug will ultimately work.

Phase II — Does it work in principle?

A few hundred patients with the relevant condition. This is the first indication of whether the drug does what it is supposed to do, and at what dose. Most candidates fail at this stage — it is considered the most critical hurdle.

Phase III — The proof

Several hundred to several thousand patients, usually compared against a standard treatment or a placebo. Only these data are generally sufficient to support a marketing authorisation application. Phase III trials are expensive and take years — and the need for capital is correspondingly high.

The primary endpoint is what counts

Before the trial begins, the company defines how success will be measured — the primary endpoint. If it is missed, the trial is considered a failure, even if some secondary findings look positive. Phrases such as 'encouraging signals in secondary endpoints' should therefore be read with caution.

Common mistakes

Treating 'topline data' as the full dataset. Topline data are a summary; the details can tell a different story.
Reading positive Phase II data as a guarantee of approval — a significant proportion of drugs still fail in Phase III.
Assuming a trial discontinuation is automatically a disaster without checking the reason: safety concerns and lack of efficacy have very different consequences for the rest of a company's pipeline.

FDA and EMA: How a Marketing Authorisation Works Burn Rate and Cash Runway

Educational content only, not investment advice. Small caps are highly speculative and total loss is possible. All information without warranty.