Biotech catalyst glossary

The vocabulary you need to read a catalyst calendar, in plain sentences. If a term on an event page isn’t here, it should be — tell us and it gets added.

FDA decision deadline (PDUFA date)

The date by which the FDA has committed to decide on a drug application, under the Prescription Drug User Fee Act. Standard review targets about ten months from filing acceptance, priority review about six; the agency usually hits the date, occasionally slips it, and can act early. On this site the short label is FDA decision.

NDA — New Drug Application

The application a company files to market a small-molecule drug in the US. Accepting it for review is what starts the PDUFA clock.

BLA — Biologics License Application

The equivalent filing for a biologic: antibodies, vaccines, cell and gene therapies. Same review machinery, different regulatory center.

sNDA / sBLA — supplemental application

A filing to change something about a drug that is already approved, most often to add a new indication or population. Supplements get their own PDUFA date, which is why an approved drug can still have catalysts.

Priority Review

An FDA designation for drugs that would be a significant improvement over what exists. It shortens the review goal to roughly six months, so a priority-review filing produces an earlier PDUFA date than a standard one.

Accelerated Approval

Approval based on a surrogate endpoint — a lab measure reasonably likely to predict real benefit — instead of waiting for the clinical outcome. Confirmatory trials are required afterwards, and the approval can be withdrawn if they fail.

FDA expert panel (AdComm)

A panel of outside experts the FDA convenes to review an application in public and vote on specific questions. The vote is non-binding, but it moves stocks hard, and the agency usually follows it. On this site the short label is FDA panel.

Not approved yet (CRL)

The FDA’s formal “not in this cycle” letter — a Complete Response Letter — listing what has to be fixed before the application can be approved. It is not a permanent rejection — many drugs are approved after resubmission — but it usually resets the timeline by six months or more. On this site the short label is Not approved.

First summary results (topline data)

The first public summary of a trial’s results: whether the primary endpoint was met and the headline numbers. It arrives weeks to months before the full dataset is presented or published, and it is the moment the market prices in. On this site those events are labeled Trial results.

Interim analysis

A pre-planned look at accumulating trial data before the trial ends, usually done by an independent monitoring committee. It can stop a trial early for overwhelming benefit, for futility, or for safety.

Primary endpoint

The single outcome a trial is designed and statistically powered to measure. A trial “succeeds” or “fails” on this measure; strong secondary endpoints rarely rescue a missed primary.

Phase 1, Phase 2, Phase 3

Phase 1 tests safety and dosing in a small group. Phase 2 looks for an efficacy signal and settles the dose. Phase 3 is the large, controlled trial meant to prove the drug works. Only phase 2 and later trials appear on this calendar.

Pivotal trial

The trial a company intends to submit as the main evidence of efficacy — normally Phase 3, sometimes a Phase 2 in rare disease or oncology. Pivotal readouts are the highest-variance events in biotech.

Primary completion date

A ClinicalTrials.gov milestone: the date the last participant’s primary-endpoint data is collected. It is not the readout date — companies announce results when they are ready, typically weeks or months later — but it is the best free leading indicator of one.

Label expansion

Approval to market an already-approved drug for an additional indication or patient group. Cheaper than a new drug and often the larger revenue event.

Breakthrough Therapy designation

An FDA status for drugs showing early evidence of substantial improvement on a serious condition. It buys more agency interaction and a faster path; it does not guarantee approval.

Orphan Drug designation

A status for treatments of rare diseases — broadly, fewer than 200,000 US patients — carrying fee waivers, tax credits and seven years of market exclusivity after approval.

Clinical hold

An FDA order to pause or stop a trial, either fully or for specific patients, usually over a safety finding. Holds arrive without a scheduled date, which is exactly why they are hard to trade around.