First-in-Human (FIH)

First-in-Human (FIH) designates the initial clinical trial administering an investigational drug or therapeutic intervention to human subjects, representing a critical milestone transitioning from preclinical development to clinical evaluation. These Phase I studies primarily assess safety, tolerability, pharmacokinetics, and pharmacodynamics in small cohorts, employing conservative dose escalation schemes starting substantially below predicted therapeutic levels.

The biopharmaceutical industry approaches FIH studies with rigorous planning and risk mitigation given inherent uncertainties translating animal data to humans. Starting dose selection employs multiple approaches including no observed adverse effect levels from animal studies, minimum anticipated biological effect levels, or allometric scaling. Dose escalation follows established schemes like 3+3 designs, accelerated titration, or model-based approaches incorporating accumulating data. Sentinel dosing staggers participants within cohorts enabling observation before exposing additional subjects. Novel modalities including gene therapies, cellular therapies, and first-in-class mechanisms warrant particular caution. As therapeutic innovation advances, FIH study design continues evolving through improved translational models, biomarker integration, and adaptive approaches balancing rapid learning with participant safety.