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Biotech & Trading Glossary: 70+ terms to understand catalysts, the FDA and small caps

The Merlintrader reference guide to the terms that actually matter when you follow biotech, small caps and catalysts: from the PDUFA date to cash runway, from a short squeeze to a surrogate endpoint. Clear, plain-English definitions.

Updated: July 5, 2026

Type: Educational guide (pillar)

Author: Merlintrader

00How to use this glossary

This page collects the terms that come up again and again in Merlintrader articles and reports on biotech, small and mid caps and catalysts. The goal is not to turn you into a regulatory expert, but to give you the minimum vocabulary to read a news item, an SEC filing or a company press release without getting lost. Every entry is meant to be self-contained: find it, read it, go back to your article.

Terms are grouped by area: the FDA and regulatory pathway, clinical trials, financials, market and trading, and corporate actions. Use the menu above to jump to the section you need. Where useful you will find a summary table and recap boxes. The definitions apply to the context of US markets (Nasdaq, NYSE) and US regulatory agencies, with a few European references where relevant.

Important note: this guide is purely educational. It explains what terms mean; it never tells you what to buy or sell. No entry should be read as a trading suggestion.

01FDA & the regulatory pathway

In biotech, a company’s value often hinges on a single decision by the regulator. Understanding how the FDA pathway works is therefore central to everything. Here are the terms you will meet most often.

FDA — Food and Drug Administration

The US federal agency that regulates drugs, medical devices, food and other products. For biotech it is the body that decides whether a drug can be sold in the United States. Its European counterpart is the EMA (European Medicines Agency). A positive or negative FDA decision can move a sector company’s stock by 50% or more in a single session.

IND — Investigational New Drug

The application a company files with the FDA in order to start testing an experimental drug in humans. It is the step that opens the door to clinical trials: without an active IND you cannot begin Phase 1. It is an early, low-profile milestone, but it marks a drug candidate’s official entry into clinical development.

NDA / BLA — New Drug Application / Biologics License Application

The formal applications for approval submitted to the FDA at the end of trials. The NDA covers chemically synthesised drugs; the BLA covers biologics (antibodies, cell and gene therapies, vaccines). The submission and acceptance of an NDA or BLA are meaningful catalysts because they officially start the FDA review clock.

505(b)(2)

An approval route that lets a company rely in part on existing data (for example from an already approved drug) instead of generating every study from scratch. It is often faster and cheaper than a full NDA and is used for reformulations, new routes of administration or new indications. For small caps it is a path that cuts development cost and time.

PDUFA — Prescription Drug User Fee Act

The law that allows the FDA to collect fees from companies in exchange for a commitment to meet set review timelines. It is renewed every five years: the version in force, PDUFA VII, covers fiscal years 2023-2027. It is the framework that makes the FDA’s decision timing predictable.

PDUFA date — target action date

The date by which the FDA commits to reach a decision on an approval application. Under standard review the goal is to act within 10 months of the application’s filing date; under Priority Review the goal drops to 6 months. Note: the PDUFA date is the deadline for a decision, which can be an approval or a rejection (CRL), not a guarantee of clearance. It is one of the most closely watched catalysts in all of biotech.

CRL — Complete Response Letter

The letter through which the FDA states that it will not approve the drug in its submitted form, listing the issues to resolve. It does not necessarily mean a definitive no: the company can address the points raised (new data, manufacturing fixes) and resubmit. In the market, however, a surprise CRL is typically a very negative event for the stock, especially for a single-product small cap.

Priority Review / Standard Review

Two review tracks. Standard Review has a 10-month decision goal. Priority Review is granted to drugs that, if approved, would offer a significant improvement in the treatment, diagnosis or prevention of serious conditions, and it cuts the goal to 6 months by focusing resources on the file. Priority Review shortens timelines but does not change the standard of evidence required for approval.

Fast Track

A designation designed to facilitate development and expedite the review of drugs that treat serious conditions and address an unmet medical need. It can be granted even on the basis of preclinical data and brings more frequent interactions with the FDA during development. It is a signal that the agency recognises the program’s importance, but it does not guarantee approval.

Breakthrough Therapy

A stronger designation than Fast Track: it includes all its benefits plus intensive FDA guidance on an efficient development program, with the involvement of the agency’s senior managers. It is granted when preliminary clinical evidence suggests a substantial improvement over existing therapies. The market often reads it as a strong endorsement of the drug’s potential.

Accelerated Approval

Not a designation but an actual approval pathway. It allows clearance based on a surrogate endpoint (a marker that can be measured earlier than the final clinical outcome, such as tumour shrinkage instead of survival) for serious diseases with unmet need. In exchange, the company must then confirm the benefit with post-approval studies: if they fail, the approval can be withdrawn.

Orphan Drug

A status granted to drugs intended for rare diseases (in the US, those affecting fewer than 200,000 people). It brings incentives such as multi-year market exclusivity, tax credits on studies and reductions of certain fees. For small-cap biotechs it is an important factor because it improves the economics of a program in a therapeutic niche.

AdCom — Advisory Committee

A panel of outside experts the FDA can convene to get an opinion on a drug before deciding. The experts vote (for example for or against the benefit-risk balance), but their vote is advisory: the FDA is not obliged to follow it, although it often does. An AdCom is a closely watched intermediate catalyst because the vote often signals the agency’s likely leaning.

EUA — Emergency Use Authorization

A temporary authorization that allows the use of a product not yet fully approved during a declared public-health emergency, when the known benefits outweigh the known risks. It became familiar during the pandemic. It is not equivalent to full approval and can be revoked once the emergency ends.

REMS — Risk Evaluation and Mitigation Strategy

A safety program the FDA can require to manage a drug’s known risks (for example mandatory physician training, patient monitoring, controlled distribution). A burdensome REMS can limit a product’s commercial uptake even after approval, so it matters when assessing sales potential.

Label / Labeling

The official FDA-approved document describing how and for whom the drug can be used: indications, dosing, warnings, side effects. A broad label (more patients, fewer restrictions) is worth more than a narrow one. Even with the same approval, the label details can shift sales estimates and the stock’s reaction.

Phase 4 — post-marketing

Studies conducted after approval, while the drug is already on the market, to monitor long-term safety and real-world effectiveness. They can be required by the FDA (for example as confirmation after an Accelerated Approval) or launched by the company to broaden indications. A negative result can lead to new warnings or, in extreme cases, product withdrawal.

02Clinical trials

Trial data are the fuel of biotech catalysts. Understanding how a study is structured helps you judge whether a result is solid or fragile, and why the market reacts the way it does.

Preclinical

The research phase before human testing, carried out in the lab and in animal models to assess basic safety and biological activity. It serves to justify starting clinical trials (the IND). Preclinical results are promising but weakly predictive: many molecules that work in the test tube later fail in humans.

Phase 1

The first test in humans, usually in a small group of healthy volunteers (or patients, in oncology). The main goal is safety: understanding how the body tolerates the drug, dosing and side effects. It is not designed to prove efficacy, so signals of activity should be read with caution.

Phase 2

In a larger group of patients who have the target disease. Here the first signals of efficacy are sought and dosing is refined, while safety data continue to be collected. It is often the juncture where it is decided whether the program makes sense: many drugs stop in Phase 2.

Phase 3

The pivotal study, in hundreds or thousands of patients, that must rigorously confirm efficacy and safety against a placebo or the standard of care. It is the main basis on which the FDA assesses approval. A success or a failure in Phase 3 is typically the heaviest catalyst in the life of a clinical-stage biotech.

Primary & secondary endpoints

Endpoints are the outcomes measured to judge whether the drug works. The primary endpoint is the study’s pre-specified main objective: it is the one that must be hit for the trial to be considered positive. Secondary endpoints are supporting measures. A trial can “miss the primary endpoint” but show secondary signals: in that case the market is usually harsh, because the primary is what counts most.

Surrogate endpoint

A marker that can be measured earlier and stands in for the final clinical outcome. For example, in oncology one can measure tumour shrinkage instead of waiting for survival data, which would take years. Surrogate endpoints allow faster decisions (they underpin Accelerated Approval) but do not always predict a true clinical benefit.

Topline data / readout

The main, summary results of a study, released as soon as available, before the full data are published. The “readout” is precisely the moment these data come out: it is the event that often moves the stock sharply. Topline data say whether the primary endpoint was hit, but the details (which come later) can change the interpretation.

Randomized, double-blind, placebo-controlled

The “gold standard” of study design. Randomized: patients are assigned to groups by chance. Double-blind: neither patients nor doctors know who receives the real drug. Placebo-controlled: there is a group receiving an inactive substance as a comparison. The more a trial meets these criteria, the more credible and hard to challenge the results are.

Open-label

A study in which everyone knows who receives the drug (no blinding). It is simpler and cheaper, but more exposed to bias: the expectations of doctors and patients can influence results. Open-label data should therefore be taken as indicative, not as definitive proof of efficacy.

Arm

A group of patients within a study that receives a specific treatment. A trial can have several arms: for example one with the drug, one with placebo, one with the standard of care. Comparing the arms is how the real effect of the drug is measured.

p-value & statistical significance

The p-value measures the probability that a result is due to chance. By convention, a value below 0.05 is considered “statistically significant”, meaning the observed effect is unlikely to be a fluke. A trial can show a numerical improvement but miss statistical significance: in that case, for both the FDA and the market, the result often is not enough.

ITT — Intention To Treat

An analysis method that includes all patients assigned to a treatment, even those who later drop out or do not follow it correctly. It is considered more conservative and realistic because it reflects what happens in practice. Alternative analyses that exclude “non-compliant” patients tend to make the drug look better than it is.

DSMB — Data Safety Monitoring Board

An independent committee that oversees an ongoing trial to protect patients. It can recommend continuing, modifying or stopping the study, for example if safety risks emerge or if efficacy is already evident. A DSMB decision (especially a stop) is an event that can move the stock abruptly.

Enrollment

The process of recruiting patients into a study. Slow enrollment is a real risk: it lengthens timelines, burns cash and delays catalysts. Announcements of “enrollment completion” are positive milestones because they bring the readout date closer.

Safety and efficacy

The two dimensions every trial must balance. Safety concerns side effects and risks; efficacy concerns how well the drug works. A highly effective drug with safety problems can still be rejected or receive a restricted label. The benefit-risk balance is what the FDA ultimately assesses.

03Financials & the balance sheet

A biotech can have the best science in the world, but if it runs out of cash before its catalyst it is forced to raise capital on unfavourable terms. Reading the balance sheet is therefore essential, especially for small caps. Here are the key terms.

Market cap

The market value of all a company’s shares: price times the number of shares outstanding. It is the most immediate measure of a company’s size. Small cap, mid cap and large cap are classes defined precisely by market cap; small-cap biotechs are often below a billion and far more volatile.

Enterprise value — EV

A measure of company value that starts from market cap, adds debt and subtracts cash. It is used to assess how much the operating business really “costs” regardless of financial structure. For a cash-rich, debt-free biotech, EV can be much lower than market cap.

Cash

The available liquidity (cash and easily liquidated instruments) the company can use to operate. For a revenue-less biotech, cash is the resource that keeps the company alive until results arrive. It is found on the balance sheet in quarterly (10-Q) and annual (10-K) filings.

Burn rate

The pace at which the company consumes cash, usually expressed per month or per quarter. A high burn rate relative to available cash is a warning sign. It is estimated by comparing cash at the start and end of the period in filings, or by looking at net operating expenses.

Cash runway

The time the current cash lasts against the burn rate, that is how many months the company can keep going without raising more capital. A short runway ahead of an important catalyst is risky, because it often forces the company into a dilutive capital raise at the worst possible time. It is one of the first numbers to check on a small cap.

Dilution

The reduction of existing shareholders’ ownership stake when the company issues new shares. More shares outstanding means each share represents a smaller slice of the company. For revenue-less biotechs dilution is almost inevitable over time: the question is not whether it will happen, but at what price and how often.

ATM offering — At-The-Market

A mechanism that lets the company sell new shares on the open market, little by little, at prevailing prices. It is flexible and discreet, but it feeds a continuous and often low-visibility dilution that can weigh on the stock over time. It should be looked for in filings and in the notes on issuance programs.

Secondary / follow-on offering

An issuance of new shares after the IPO, to raise capital in one go (often with the help of underwriting banks). It usually happens at a discount to the market price, so in the short term it can push the stock down. It is one of the typical ways a biotech funds development.

Shelf registration — S-3

A registration with the SEC (form S-3) that lets the company prepare in advance the ability to issue securities, then do so quickly when it wants, up to a certain limit. It is not itself dilution, but it is the “launch pad” that makes it possible: its presence signals that the company could raise capital at short notice.

Warrant

An instrument that gives the holder the right to buy the company’s shares at a set price by a certain date. Warrants are often bundled with capital raises as an incentive for investors. When exercised they create new shares, and therefore further dilution: this is why they must be counted when assessing the capital structure.

Reverse split

An action that reduces the number of shares by consolidating them (for example 1 new for every 10 old), mechanically raising the price per share without changing the overall value. It is often used to stay above the minimum price threshold required by Nasdaq and avoid delisting. It is frequently read as a sign of weakness, because it indicates the stock had fallen too far.

Going concern

An accounting warning that appears in financial statements when there is substantial doubt about the company’s ability to keep operating over the next 12 months, typically due to lack of cash. It is a serious red flag: it indicates that without new capital or positive events the company may not make it. It should always be looked for in the notes of the 10-K and 10-Q.

10-K, 10-Q, 8-K, S-1 — the SEC filings

The documents that listed companies file with the SEC. The 10-K is the full annual report (financials, risks, strategy). The 10-Q is the quarterly report, more concise. The 8-K flags material events as they happen (deals, capital raises, management changes, trial results): it is often the first place an official piece of news appears. The S-1 is the registration document for a listing (IPO). They can be read for free on EDGAR, the SEC’s public archive.

Guidance

The estimates management provides on future results (revenue, expenses, timing). In pre-revenue biotech, guidance often concerns catalyst timing and cash runway more than sales figures. Raised or lowered guidance can move the stock as much as the results themselves.

04Market & trading

Small caps move violently not only because of news, but because of how their market structure is built: few shares traded, many shorts, thin liquidity. These terms explain why.

Float

The number of shares actually available for trading on the market, excluding those that are locked up (for example held by insiders or restricted). A small float means it takes few trades to move the price a lot: it is one of the reasons micro caps are so volatile. Not to be confused with total shares outstanding.

Short interest

The share of stock sold short, that is borrowed and sold by those betting on a decline. A high short interest indicates strong market skepticism, but it also creates the fuel for a possible explosive rebound (the short squeeze) if news goes the other way. It is often expressed as a percentage of the float.

Short squeeze

The rapid upward move triggered when many short sellers are forced to buy back shares to close their positions, further fuelling the rise. It is more likely on stocks with high short interest and a small float. It can produce spectacular, short-lived moves, often disconnected from fundamentals.

Days to cover — short ratio

An estimate of how many days of trading it would take short sellers to buy back all the shorted shares, given average volume. A high value indicates that, if a rebound starts, shorts will struggle to exit quickly: it is considered an ingredient that makes a squeeze more likely.

Liquidity

The ease with which a stock can be bought or sold without moving its price too much. Small caps often have low liquidity: trades are sparse and the spread between bid and ask is wide. Low liquidity means greater volatility and greater difficulty entering or exiting a position at a fair price.

Volatility

The measure of how widely and quickly a stock’s price swings. Biotechs and small caps are among the most volatile assets precisely because their value depends on binary events (a trial, an FDA decision). High volatility means opportunity but also elevated risk, in both directions.

Gap

A price jump between one session’s close and the next session’s open, with no trades in between. On biotech stocks, gaps are common after news released while markets are closed (a readout, an FDA decision): the stock can open far above or far below the prior day’s price.

Trading halt

A temporary suspension of trading in a stock, decided by the exchange. It can be triggered by excess volatility or, very often in biotech, while awaiting an important piece of news (an FDA decision, a corporate announcement). When trading resumes the stock can move sharply based on the content of the news.

Pre-market and after-hours

The trading sessions outside official hours: before the open (pre-market) and after the close (after-hours). Many biotech news items come out in these windows, and the first moves happen there. Liquidity is thin, however, so prices can be extreme and not very representative of where the stock will later open in the regular session.

Catalyst

An event capable of moving a stock’s price significantly: an FDA decision, a trial readout, a deal, a merger, a data release. “Catalyst investing” consists of tracking these appointments on the calendar. In biotech, catalysts are often dated (for example a PDUFA date), which makes them predictable in timing, but not in outcome.

Binary event

A catalyst whose outcome is essentially “all or nothing”: the trial succeeds or fails, the FDA approves or rejects. Around a binary event a stock can double or halve in an instant. It is the concept that explains why certain biotechs are described as high-risk bets: much of the value depends on a single yes or no.

05M&A & corporate actions

Deals, licences and acquisitions are among the most powerful catalysts in biotech, because they can validate a company’s science and bring cash without dilution. Here is what they are called.

M&A — Mergers and Acquisitions

Mergers and acquisitions: when one company buys another or two companies combine. In biotech, large pharma companies often acquire small caps to get their hands on a promising drug. The announcement of an acquisition typically pushes the target stock toward the offer price, with a premium over its prior value.

Buyout premium

The difference between the price offered in an acquisition and the stock’s market price before the announcement. A high premium reflects how much the buyer values the asset and how much competition it fears. It is what often generates the sudden jumps in the target stock when a deal becomes public.

Partnership / collaboration

An agreement between two companies to develop or commercialise a product together, sharing costs, expertise and revenue. For a small cap, a partnership with a large pharma company often brings an upfront payment, credibility and reduced execution risk. It is seen as external validation of the science.

Licensing deal

An agreement through which one company grants another the right to develop or sell its drug, in exchange for payments. It typically includes an upfront (initial payment), milestones tied to targets and royalties on sales. For a cash-poor biotech it is a way to fund itself by monetising the pipeline without diluting shareholders.

Milestone payment

A payment conditional on reaching a predefined target: the start of a trial, a positive result, an approval, a sales threshold. Press releases often mention deals worth “up to” a certain figure: that figure almost always includes milestones that may never materialise. They should therefore be read carefully, distinguishing certain money (upfront) from potential money.

Royalty

A percentage of a product’s future sales owed to whoever granted the rights (for example the company that invented the drug). Royalties can become a stable, long-term revenue stream, without the company having to bear commercialisation costs. They are a key element in assessing the value of a licensing deal.

06Merlintrader Health Score

In Merlintrader reports you will often find a summary score called the Health Score. It is worth explaining here, because it is an “in-house” term that helps you read the stock profiles.

Health Score — robustness score

A score from 1 to 5 that summarises the robustness or fragility of a company over a 12-18 month horizon. It is based on five pillars with different weights: Balance sheet and runway (30%), Catalyst (30%), Dilution (20%), Liquidity (10%) and Execution (10%). A high score indicates a more solid structure; a low one, more fragility.

Keep in mind: the Health Score measures structural soundness; it is not a buy or sell signal. A fragile company can still rise and a solid one can still fall: the score is there to frame risk, not to predict price.

Pillar	Weight	What it measures
Balance sheet & runway	30%	Available cash and how long it lasts at the current burn rate.
Catalyst	30%	Presence, quality and timing of upcoming events able to move the stock.
Dilution	20%	Risk of new share issuance and history of past dilution.
Liquidity	10%	Ease of trading the stock and depth of its market.
Execution	10%	Management’s ability to meet timelines and promises.

07Other useful terms

A selection of terms that come up often in news and filings and round out the basic vocabulary.

Standard of care

The treatment currently considered best and most widely used for a given disease. A new drug is often compared to the standard of care, not just to placebo: beating the standard is much harder and worth far more commercially. Understanding what the standard of care is helps judge how meaningful a positive result really is.

OS & PFS — Overall Survival, Progression-Free Survival

Two key endpoints in oncology. Overall Survival (OS) measures how long patients live: it is the most solid data point but takes a long time. Progression-Free Survival (PFS) measures how long the disease does not worsen: it is faster to obtain and is often used as an intermediate endpoint. A PFS improvement without a clear OS benefit can spark debate about the drug’s true value.

ORR — Objective Response Rate

The percentage of patients whose tumour shrinks by a predefined amount in response to treatment. It is an endpoint often used in early phases and in Accelerated Approval because it can be measured relatively early. A high ORR is encouraging, but on its own it does not say how long the response lasts or whether patients live longer.

Boxed Warning — black box warning

The most serious warning the FDA can require on a drug’s label, reserved for potentially grave or lethal risks. A boxed warning can strongly limit a product’s use and sales, even if approved. Its imposition or removal is therefore an element the market follows closely.

Biosimilar

A highly similar version of an already approved biologic drug, produced by another company after exclusivity expires. It is the equivalent of generics for biologics, although not identical because of the complexity of these molecules. The arrival of biosimilars erodes the original drug’s sales and reshapes competition in a market.

Priority Review Voucher — PRV

A “voucher” the FDA grants in specific cases (for example certain rare pediatric or tropical diseases) that entitles the holder to a Priority Review on a future drug of their choosing. It has real economic value because it is transferable: it can be sold to other companies for tens or hundreds of millions. Its award or sale is a catalyst in itself.

Form 4 — insider buying & selling

The form that executives, directors and large shareholders file with the SEC when they buy or sell shares of their own company. Insider purchases are often read as a signal of confidence; sales should be interpreted with more caution, because they can have personal reasons. It is public, verifiable data on EDGAR.

13F — institutional ownership

The quarterly report that large managers (funds, hedge funds) file with the SEC listing their equity positions. It lets you see whether institutional investors are entering or exiting a stock. Note: 13Fs are published with a delay, so they capture the past, not necessarily current positions.

Convertible note

A debt security that can be converted into shares under certain conditions. For the company it is a way to raise capital at a lower cost than pure debt, but it carries potential dilution if conversion occurs. It should be considered when assessing how many shares might exist in the future.

Non-dilutive financing

Capital raised without issuing new shares: for example public grants, licensing deals with an upfront, the sale of a Priority Review Voucher or of royalties. It is particularly valuable for biotechs because it funds development without penalising existing shareholders. When a company announces it, it is often read as a positive signal about the quality of its assets.

Analyst rating & price target

The assessments published by investment-bank analysts: a rating (for example Overweight, Neutral, Underweight) and a 12-month price target. They are opinions, not certainties, and on small-cap biotechs coverage is often limited to a few banks. Useful as a viewpoint, but to be weighed critically and not taken as a guarantee.

Sentiment

The overall mood of investors toward a stock, often gauged by looking at comments on forums and social platforms such as Reddit, Stocktwits or X. It reflects the opinions of non-professional traders, not institutional analysts, and can change quickly. It is useful for understanding the narrative around a stock, but should not be confused with fundamental analysis.

Primary sources

Biotech / Tech Catalyst Calendar
PDUFA dates, clinical data, defense & tech catalysts in one calendar.
Open the calendar →

Disclaimer. For educational and informational purposes only. Not financial advice nor a recommendation to buy, sell or hold, in accordance with SEC (USA) guidance. Securities and instruments mentioned may be volatile and involve substantial risk, including loss of principal. Always do your own research and consult a licensed advisor. Full disclaimer: merlintrader.com/disclaimer.

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