Biotech Catalyst Glossary
A comprehensive guide to FDA approval terminology, regulatory pathways, and event-driven investing concepts. Understand PDUFA dates, advisory committees, breakthrough designations, and ODIN scores.
Designed for biotech investors, event-driven traders, and anyone researching pharmaceutical catalysts. Each term includes a clear definition tailored for non-regulatory professionals.
PDUFA
Prescription Drug User Fee Act. The FDA's commitment to review drug applications (NDAs, BLAs) within standard (10 months) or priority (6 months) timelines. PDUFA dates are key biotech catalysts.
NDA
New Drug Application. The formal submission to FDA seeking approval to market a new drug in the United States. Required for all new small-molecule therapeutics and some biologics.
BLA
Biologics License Application. The FDA submission for biological products (monoclonal antibodies, cell therapies, gene therapies, vaccines). Follows similar review timelines as NDAs.
sNDA
Supplemental New Drug Application. An application to amend an already-approved NDA (e.g., new indication, formulation, or dosage). Often faster to approve than original NDAs.
CRL
Complete Response Letter. FDA rejection of a drug application citing deficiencies. Companies must address all CRL issues and resubmit. Multiple CRLs reduce approval probability significantly.
AdCom
Advisory Committee Meeting. The FDA convenes independent experts to review trial data and vote on a drug's benefit-risk profile. AdCom votes strongly influence FDA approval decisions.
Priority Review
FDA expedited review pathway (6-month timeline instead of standard 10 months). Granted for drugs that provide substantial improvement over existing therapies.
Breakthrough Therapy
FDA designation for drugs showing significant efficacy advantage over available therapies. Enables expedited review, more frequent meetings with FDA, and potential accelerated approval.
Fast Track
FDA expedited development pathway for drugs addressing serious or unmet medical needs. Enables priority review and rolling submission of application data.
Accelerated Approval
FDA approval based on surrogate or intermediate endpoints rather than clinical benefit. Requires confirmatory Phase 4 trials. Enables faster market entry but carries uncertainty risk.
REMS
Risk Evaluation and Mitigation Strategy. FDA-mandated program for drugs with serious safety risks. REMS requirements complicate marketing and reduce patient access, impacting peak sales potential.
CMC
Chemistry, Manufacturing, and Controls. The regulatory section of a drug application covering drug substance synthesis, drug product formulation, stability, and quality assurance. CMC deficiencies often delay approval.
sBLA
Supplemental Biologics License Application. Amendment to an approved BLA (e.g., new indication, manufacturing change). sBLA approvals can provide near-term catalysts for biotech companies.
Orphan Drug
Designation for drugs treating rare diseases (<200,000 patients in US). Provides 7-year market exclusivity post-approval, tax credits, and expedited review. Reduces market size but increases profit margins.
ODIN Score
Proprietary machine learning score (0–100%) predicting FDA approval probability for a PDUFA event. Trained on 2,210 historical FDA decisions. PDUFA.bio's flagship predictive metric.
Runup Strategy
Trading strategy buying biotech stock weeks or months before a PDUFA decision, expecting stock appreciation if approved. TIER_1 and TIER_2 ODIN events are prime runup candidates.
Regulatory Pathways at a Glance
| Pathway | Timeline | Eligibility | Impact |
|---|---|---|---|
| Standard Review | 10 months (NDA/BLA) | All drugs | Neutral |
| Priority Review | 6 months | Substantial advantage over existing | Bullish |
| Breakthrough Therapy | Expedited | Significant advantage | Very Bullish |
| Fast Track | Expedited | Serious unmet need | Bullish |
| Accelerated Approval | Expedited | Surrogate endpoint evidence | Very Bullish / Risky |
Drug Application Types
NDA
Original approval for new small-molecule drugs. Full data package (chemistry, manufacturing, nonclinical, clinical). Standard or priority review timelines apply.
BLA
Approval for biologics: monoclonal antibodies, cell therapies, gene therapies, recombinant proteins, vaccines. Follow similar pathways as NDAs but with specialized chemistry/manufacturing requirements.
sNDA
Amendment to approved NDA for new indication, dosage, formulation, or manufacturing change. Often faster approval (3–6 months) because active ingredient already approved.
sBLA
Amendment to approved BLA for manufacturing, indication, or dosage changes. Important catalyst for approved biotech companies seeking label expansions.
Key Investing Concepts
CRL Risk
A Complete Response Letter from FDA means rejection. The drug cannot launch; company must address deficiencies and resubmit. CRL probability is 15–30% even for strong candidates. TIER_4 ODIN events have >50% CRL risk.
REMS Burden
Risk Evaluation and Mitigation Strategy requirements (e.g., patient enrollment registries, prescriber training) reduce peak sales potential by 20–50%. Common for cancer drugs, opioids, and other high-risk products.
Label Expansion
sNDA/sBLA approvals for new indications or patient populations. Often quicker than original approval and can double-triple peak sales. Secondary catalysts for approved drugs.
Orphan Advantage
Rare disease designation (Orphan Drug status) grants 7-year market exclusivity post-approval. Smaller peak sales but higher margins. Common in oncology, neurology, immunology.