Clinical DevelopmentLast reviewed April 2026

First-in-Human Study(FIH)

The first clinical trial in which an investigational product is administered to human subjects, typically as a Phase 1 study.

Usage Examples

The FIH study used MABEL-based dosing starting at 1% of the projected clinical dose.
Single ascending dose cohorts of 6 healthy volunteers each progressed on a 2-week stagger.
A dose-limiting toxicity in cohort 3 triggered the safety review committee to confirm escalation criteria.

What is FIH?

A First-in-Human (FIH) study is the initial clinical investigation of an investigational product in human subjects. FIH studies are typically Phase 1 trials enrolling healthy volunteers for small molecules or patients for oncology and other high-risk indications. The design addresses fundamental safety questions: tolerability, pharmacokinetics, and preliminary pharmacodynamics at planned clinical doses.

FIH study design is driven by the IND-enabling nonclinical package. Starting dose selection typically uses NOAEL-based or MABEL-based approaches depending on product class. Single Ascending Dose (SAD) designs escalate through cohorts; Multiple Ascending Dose (MAD) follows to assess repeat-dose tolerability. Dose-limiting toxicity stopping rules, safety review committee roles, and emergency protocols are essential design elements.

FIH studies for high-risk products (biologics with novel mechanisms, CAR-T therapies, first-in-class oncology products) face additional scrutiny. The 2006 TGN1412 incident at Northwick Park highlighted risks and led to EMA and FDA guidance on minimum anticipated biological effect level (MABEL) dosing for high-risk biologics. Starting doses for these products are typically significantly lower than NOAEL-derived estimates.

Regulatory Context

This term appears most often in clinical development workflows where submission quality, regulatory evidence, and audit readiness depend on consistent language. It is commonly referenced alongside ICH M3, 21 CFR 312, FDA GUIDANCE EXPLORATORY IND.

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When This Matters

The FIH study used MABEL-based dosing starting at 1% of the projected clinical dose.
Single ascending dose cohorts of 6 healthy volunteers each progressed on a 2-week stagger.
A dose-limiting toxicity in cohort 3 triggered the safety review committee to confirm escalation criteria.

Common Mistakes

Applying one-region clinical assumptions to global submission strategies.
Missing protocol-to-regulation traceability for pivotal studies.
Underestimating how regional guidance updates impact trial documentation.

Related Regulations

ICH M321 CFR 312FDA GUIDANCE EXPLORATORY IND

Frequently Asked Questions

Small molecules typically use NOAEL (No Observed Adverse Effect Level) divided by a safety factor (commonly 10x) and allometrically scaled to humans. High-risk biologics use MABEL (Minimum Anticipated Biological Effect Level) which can produce much lower starting doses. Specific methodology depends on mechanism, species translation, and indication.

Depends on indication and risk profile. Most small molecules and non-oncology biologics are first studied in healthy volunteers. Oncology products and high-risk indications (advanced disease, life-threatening conditions) are typically studied directly in patients from FIH onward.

The 2006 TGN1412 incident — six healthy volunteers developed life-threatening cytokine release syndrome at a starting dose derived from NOAEL — prompted EMA and FDA guidance on high-risk FIH design. MABEL-based dosing, sequential subject enrollment (not parallel), and enhanced safety monitoring became standard for this product class.