Biotech Glossary

Biotech coverage is full of jargon. Here's what it all actually means — 54 terms, in plain English.

FDA & Regulatory

The regulatory pathway terms you'll see in every biotech headline.

PDUFA Date: The deadline by which the FDA must complete its review of a drug application. Set under the Prescription Drug User Fee Act. It's the most predictable binary catalyst in biotech — the FDA has to act (approve, reject, or delay) by this date.
BLA (Biologics License Application): The application a company files with the FDA to get approval for a biologic drug — anything made from living organisms (antibodies, cell therapies, gene therapies). The biologic equivalent of an NDA.
NDA (New Drug Application): The application filed with the FDA to approve a small-molecule drug — a chemically synthesized compound, like a pill. The FDA reviews safety, efficacy, and manufacturing before deciding.
IND (Investigational New Drug): The application a company files with the FDA before it can begin testing a drug in humans. The FDA reviews preclinical safety data and the proposed clinical trial design. Approval lets the company start Phase 1.
Orphan Drug Designation: FDA status granted to drugs treating rare diseases (fewer than 200,000 patients in the US). Benefits include 7 years of market exclusivity, tax credits for clinical costs, and waiver of FDA user fees. Biotech companies love orphan designations.
Fast Track Designation: An FDA designation that speeds up the review of drugs for serious conditions with unmet medical need. Allows rolling submissions (submitting data piece by piece instead of all at once) and more frequent FDA communication.
Breakthrough Therapy Designation: An FDA designation for drugs showing substantial improvement over existing therapies for serious conditions. Provides intensive FDA guidance and a faster development path. It's not a guarantee of approval, but it's a strong signal.
Accelerated Approval: A pathway that lets the FDA approve a drug based on a surrogate endpoint (a lab measure or early sign) rather than waiting for definitive clinical outcomes. The company must run confirmatory trials post-approval. Controversial — some approved drugs later fail confirmatory trials.
Priority Review: FDA review designation that shortens the review timeline from 10 months to 6 months. Granted for drugs that would be significant improvements over existing therapies. Often paired with other expedited pathways.
Advisory Committee (AdCom): A panel of outside experts the FDA convenes to review a drug application and vote on whether to recommend approval. The FDA usually follows the committee's recommendation but is not legally bound by it.
Complete Response Letter (CRL): The letter the FDA sends when it decides NOT to approve a drug application. It explains what the company needs to do to get approval (more data, manufacturing fixes, safety studies). A CRL is a major negative catalyst — stocks often crater on the news.
Surrogate Endpoint: A substitute measure used to predict a clinical outcome — like tumor shrinkage instead of overall survival. The FDA may accept a surrogate endpoint for accelerated approval, but confirmatory clinical data must follow.
FDA Holds (Clinical Hold): When the FDA halts a clinical trial — usually for safety reasons. A clinical hold on a lead asset is a significant negative catalyst. Partial holds allow some patients to continue dosing.

Clinical Trials

How drugs move from the lab to the pharmacy.

Phase I: The first testing in humans — typically a small trial (20–80 healthy volunteers, or patients for cancer drugs) focused on safety, dosing, and side effects. Not powered to prove efficacy. Still, Phase 1 data can move stocks if early signals are strong.
Phase II: Testing in a larger group (100–300 patients) with the target disease. The goal is preliminary evidence of efficacy (does it work?) and continued safety monitoring. Phase 2 is where many biotech stocks live or die — proof-of-concept data.
Phase III: Large-scale trials (hundreds to thousands of patients) comparing the drug to standard of care or placebo. This is the pivotal data the FDA reviews. Phase 3 success is the single biggest catalyst in biotech investing.
Phase IV: Post-marketing surveillance after a drug is approved. Required for accelerated approvals (confirmatory trials) and sometimes for broader label use.
Pivotal Trial: The key Phase 3 trial that forms the basis for FDA approval. These trials are typically randomized, double-blind, and placebo-controlled — the gold standard of clinical evidence.
Randomized Controlled Trial (RCT): A trial where patients are randomly assigned to receive either the drug or a control (placebo or standard therapy). Randomization eliminates bias. Double-blind means neither patients nor doctors know who got what.
Primary Endpoint: The main outcome a trial is designed to measure — like progression-free survival in cancer or viral clearance in hepatitis. Missing the primary endpoint is a failure, even if secondary endpoints look good.
Secondary Endpoint: Additional outcomes the trial measures — like overall survival, quality of life, or safety. Positive secondary endpoints can support label expansion but don't replace the primary endpoint.
Progression-Free Survival (PFS): A common oncology endpoint — the time patients live without their cancer getting worse. PFS is a surrogate endpoint; overall survival (OS) is the gold standard but takes years longer to read out.
Overall Survival (OS): The most important endpoint in oncology — the time from trial start to death from any cause. Definitive but slow. Drugs approved on PFS may later need OS data for label expansion or reimbursement.
ORR (Overall Response Rate): The percentage of patients whose tumors shrink by a predefined amount. Common in early-phase oncology trials. Higher ORR means more patients benefit, but durability matters too.
CR (Complete Response): Disappearance of all signs of cancer in response to treatment. The best possible outcome on imaging. Partial response (PR) means significant but incomplete shrinkage.
Median Survival: The time at which half of the patients in a trial are still alive. Reported as 'median OS of 18 months' — meaning half lived longer. Provides a quick measure of treatment effect.
Hazard Ratio (HR): A statistical measure comparing the risk of an event (like death or disease progression) between two groups. An HR of 0.6 means the treatment group has a 40% lower risk — generally a good result.
P-Value: A measure of statistical significance — the probability that the result happened by chance. The magic threshold is p < 0.05. A p-value of 0.01 means a 1% chance the result is random. Biotech investors watch p-values closely.
Confidence Interval (CI): A range that likely contains the true effect size. A 95% CI of 0.5–0.7 for a hazard ratio means we're 95% confident the true HR is between 0.5 and 0.7. Narrow intervals mean more precise estimates.

Drug Types & Modalities

From small molecules to gene editing — what's in the lab.

Small Molecule: A chemically synthesized drug — a pill. Small molecules can cross cell membranes and reach intracellular targets. Examples: aspirin, statins, and most traditional pharmaceuticals.
Biologic: A drug made from living organisms — antibodies, proteins, vaccines, cell therapies. Biologics are large, complex molecules that are manufactured in cells, not synthesized chemically. Usually injected or infused.
Monoclonal Antibody (mAb): A lab-made protein that targets a specific antigen (like a cancer cell surface marker). The backbone of modern biotech — from Keytruda (Merck) to Dupixent (Regeneron).
Antibody-Drug Conjugate (ADC): A 'smart bomb' — an antibody linked to a toxic payload. The antibody delivers the drug directly to cancer cells, sparing healthy tissue. Hot area: Trodelvy (Gilead), Enhertu (AstraZeneca/Daiichi Sankyo).
CAR-T Cell Therapy: A treatment where the patient's own T cells are genetically engineered to attack their cancer. One-time treatment, potentially curative. Approved examples: Kymriah (Novartis), Yescarta (Gilead), Casgevy (Vertex/CRISPR).
Gene Therapy: A one-time treatment that fixes or replaces a defective gene. Usually delivered via a viral vector (AAV). Examples: Zolgensma (Novartis) for SMA, Luxturna (Spark) for blindness.
CRISPR: A gene-editing technology that acts as molecular scissors to cut DNA at specific locations. The basis of Casgevy (Vertex/CRISPR Therapeutics), the first FDA-approved CRISPR therapy.
mRNA (Messenger RNA): A molecule that instructs cells to make proteins. The technology behind COVID vaccines (Pfizer-BioNTech, Moderna) and now being applied to cancer vaccines, rare diseases, and more.
RNAi (RNA Interference): A technology that silences specific genes by destroying their mRNA before it can make proteins. Alnylam is the pioneer with Onpattro and Givlaari. Potential applications in hypertension and rare disease.
Antisense Oligonucleotide (ASO): A short DNA-like molecule that binds to RNA to block or modify protein production. Ionis Pharmaceuticals is the leader in ASO therapeutics (Spinraza, Tegsedi).
Bispecific Antibody: An engineered antibody that binds two different targets simultaneously. Used in oncology to link T cells to cancer cells. Examples: Tecvayli (J&J), Elrexfio (Pfizer).
Checkpoint Inhibitor: An antibody that releases the brakes on the immune system, allowing it to attack cancer. The class that revolutionized oncology: Keytruda (Merck), Opdivo (BMS), Yervoy (BMS).

Biotech Business Terms

The financial and deal terms that determine whether a company survives.

Cash Runway: How many months a biotech can keep operating before it runs out of money. Calculated as cash on hand divided by monthly burn. Most biotechs need to raise capital (dilution) or find a partner before Phase 3.
Burn Rate: The rate at which a biotech spends cash — typically $5–20 million per quarter for clinical-stage companies. High burn rates with limited cash are a major red flag.
Partner / License Deal: A deal where a biotech licenses its drug to a larger pharma company for upfront cash, milestones, and royalties. Partnering can fund development without dilution. Large pharma validates the science.
Milestone Payment: A cash payment triggered by a specific event — like FDA approval, Phase 3 success, or reaching $1B in sales. Milestone payments can transform a biotech's balance sheet overnight.
Royalty: A percentage of drug sales paid to the biotech that originated the drug, even after it's partnered or sold. A royalty stream is a biotech's annuity.
Phase 3 Readiness: The stage where a biotech has enough cash and data to start the pivotal trial. Companies often raise capital or partner here to fund the expensive Phase 3 program.
Biotech IPO: A biotech's initial public offering — usually on Nasdaq, raising $75–200 million to fund clinical programs. Most biotech IPOs happen between Phase 1 and Phase 3, when the company has enough early data to attract investors.
Reverse Stock Split: When a company reduces its share count to boost the price (e.g., 1-for-10 split). Common for struggling biotechs trying to stay above Nasdaq's $1 minimum. Often a red flag, but not always fatal.
Dilution: When a biotech issues new shares to raise cash, reducing existing shareholders' ownership. Biotechs burn through cash and dilute frequently. Investors must watch the share count as carefully as the science.
Clinical Stage: A company that hasn't yet generated revenue from drug sales. Pure clinical-stage biotechs have no product revenue — their value is entirely based on trial data and the probability of approval.
Commercial Stage: A biotech that has at least one approved drug generating sales. Commercial-stage companies have product revenue, which changes the financial story from pure R&D to commercial execution.
Patent Cliff: When a company's key patent expires and generic competitors enter. The biotech's revenue can drop sharply. Investors watch the patent life of key drugs to estimate how long the revenue stream lasts.
Companion Diagnostic: A test that identifies which patients are likely to respond to a drug. Required for many targeted therapies — the drug only works in patients the test identifies as positive.