First-in-Human Dosing: CRO Support for a Seamless Phase 1 Transition

A scientist with gloves on holding a pen near test tubes

After years of research and preclinical testing, the moment arrives: your investigational therapy is ready for first-in-human (FIH) dosing. This critical milestone marks the start of clinical development and provides the first real-world data on safety, tolerability, and pharmacokinetics in humans.

But FIH studies are complex and highly scrutinized by regulatory agencies. To de-risk and streamline this transition, biotech companies increasingly partner with experienced Contract Research Organizations (CROs) like InfinixBio.

What Is First-in-Human Dosing?

FIH dosing occurs during Phase 1 clinical trials, where healthy volunteers (or, in some cases, patients) receive a new investigational drug for the first time. The primary objectives are to assess:

Safety and tolerability
Pharmacokinetics (PK) — how the drug is absorbed, distributed, metabolized, and excreted
Pharmacodynamics (PD) — biological effects and dose-response relationships
Maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs)

These insights guide dosing strategies for subsequent trials and support regulatory filings.

What’s Needed Before You Dose?

A scientist sat at a desk typing on a keyboard

Before reaching FIH dosing, your program must meet strict regulatory and scientific criteria. This includes:

Completion of GLP toxicology studies
Validated bioanalytical methods
A strong Investigational New Drug (IND) application
Clear clinical protocols and risk mitigation strategies
Manufacturing of GMP-grade drug substance and product

How CROs Streamline the FIH Process

A well-aligned CRO can support your FIH transition by:

Designing dose-escalation protocols informed by preclinical PK/PD and safety data
Providing IND-enabling studies, including toxicology and bioanalysis
Performing PK/PD modeling to refine dose and schedule
Ensuring data quality and regulatory compliance

With experienced guidance, you can avoid common pitfalls and gain meaningful data from your very first dose.

InfinixBio’s FIH Support Services

At InfinixBio, we provide end-to-end support to help your molecule reach humans safely and efficiently.

Our capabilities include:

Preclinical toxicology, DMPK, and bioanalytical services
Regulatory consulting and robust reporting to aid in the IND document preparation
Clinical bioanalysis with validated LC-MS/MS and ligand binding assays
PK/PD modeling to support dose selection

We specialize in helping biotech innovators de-risk early clinical development and position their programs for long-term success.

Make Your First Dose Count

Your first-in-human trial is a defining moment. With InfinixBio, you gain a CRO partner that’s scientifically rigorous, operationally agile, and committed to moving your program forward—safely and strategically.

Let’s make your clinical debut a success—schedule a consultation to learn more!