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 The confirmatory trial can fail, and the drug can be withdrawn.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.
Clinical trial terms
The words a readout press release is written in. Each definition says what the term measures and what it does not: simplifying the language never simplifies the fact.
Control arm / comparator
A second group of patients in a trial who got a different treatment, so results could be compared. A comparator is often an active drug, not a placebo.
Single-arm trial
Everyone in the study got the drug; there was no comparison group. Standard and accepted in some settings (much of oncology), but it means there is no direct read on how patients would have done on something else.
Randomized
Patients were sorted into treatment groups by chance, not by choice. This reduces one specific kind of bias; it does not by itself make a trial correct.
Double-blind
Neither the patients nor their doctors knew who got which treatment. The sponsor and trial monitors often do know.
Placebo-controlled
Compared against a dummy treatment with no active ingredient. A placebo is not nothing; measuring against it is the point.
Primary endpoint
The main question the study was built to answer. A study can miss its primary endpoint and still be useful.
Met its primary endpoint
The study answered its main question in the drug's favour. This is a statistical result, not by itself proof of clinical benefit.
ORR (objective response rate)
The share of patients whose tumours shrank by a set amount. Shrinkage is not cure and is not survival.
PFS (progression-free survival)
How long patients lived without their disease getting worse. Different from overall survival, which is how long they lived.
OS (overall survival)
How long patients lived. The endpoint that needs no proxy.
Median
The middle value: half the patients were higher, half lower. Not the same as the average, and the difference matters in survival data.
Hazard ratio
A hazard ratio of 0.65 means the event happened about 35% less often in the treated group in this study. It is not a percentage improvement in outcome.
Statistically significant (p < 0.05)
A result this large would be unlikely to happen by chance alone. Statistical significance is not the same as clinical importance.
95% confidence interval
The range the true value most likely falls in. A number without its range invites over-reading.
Non-inferiority trial
Designed to show the drug is not meaningfully worse than an existing one, within a pre-set margin -- not that it is better.
505(b)(2)
An approval route that lets a company rely partly on studies already done for a similar drug. It has its own full evidence requirements; it is not a shortcut.
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