Catalyst glossary

Plain English, and where the term is routinely misused, we say so. 14 terms.

PDUFA date

The deadline the FDA gives itself to decide on a drug application, set under the Prescription Drug User Fee Act. Standard review is 10 months from filing; priority review is 6. It is a goal, not a guarantee — the FDA can act early, act late, or issue a CRL instead.

CRL

Complete Response Letter. The FDA declining to approve, in its current form. It is not a rejection of the drug forever — it lists what must be fixed. Roughly 43% of drugs that get a CRL are approved on the next cycle. See what is a CRL.

Topline / readout

A company's first public summary of a trial's results — usually a press release, weeks to months after the last patient is measured. There is no scheduled date. Unlike a PDUFA, a company announces when it decides to.

Primary completion date

The date the last patient is measured for a trial's primary outcome. It is a data lock, not an announcement. Topline typically follows weeks to months later. We never present it as a readout date.

Advisory Committee (AdComm)

An external panel of experts convened by the FDA to advise on an application. Its vote is not binding — the FDA usually follows it, but not always. An AdComm is a separate event from the PDUFA decision, and often lands weeks earlier.

Breakthrough Therapy Designation (BTD)

An FDA designation that speeds development for drugs showing substantial improvement over available therapy on a clinically significant endpoint. It is a process advantage, not evidence the drug works.

Priority Review

Shortens the FDA's review clock from 10 months to 6. Granted when a drug would be a significant improvement in safety or effectiveness. It changes the deadline, not the odds.

Orphan Drug Designation

For drugs treating conditions affecting fewer than 200,000 people in the US. Brings tax credits, fee waivers and 7 years of market exclusivity.

Accelerated Approval

Approval based on a surrogate endpoint reasonably likely to predict clinical benefit, with confirmatory trials required afterwards. The confirmatory trial can fail, and the drug can be withdrawn.

Surrogate endpoint

A measurable stand-in (a lab value, a scan) for the outcome you actually care about (survival, symptoms). Faster and cheaper — and sometimes wrong.

Run-up

The stock's price move into a catalyst. Widely believed to be reliably positive in biotech. Across ~4,800 events in three catalyst classes, we find no systematic run-up — the population median is within half a percent of zero. See the readout study.

Days to cover

Short interest divided by average daily volume. For an illiquid nano-cap the denominator collapses and the ratio explodes — 18% of our FINRA panel exceeds 100 days. Above ~60 it stops meaning “squeeze risk” and starts meaning “this stock barely trades.” We do not print those numbers.

Market-cap tier

nano (<$50M) · micro ($50M–$300M) · small ($300M–$2B) · mid ($2B–$10B) · large (>$10B). We compute the tier as of the event date, not today — using today's is a look-ahead error.

IQR (interquartile range)

The middle 50% of outcomes — from the 25th to the 75th percentile. We lead with the median and the IQR rather than the mean, because in biotech a handful of enormous winners drags the mean far above what actually happens to a typical name.

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