In Vitro

In vitro (Latin for 'within the glass') refers to biological or biochemical experiments performed in a controlled, artificial laboratory environment outside a living organism. Examples include receptor-binding affinity assays, surface plasmon resonance (SPR), enzymatic stability tests, and immortalized cell culture incubations.

In vitro assays demonstrate what a peptide is chemically capable of binding, but cannot predict human oral bioavailability, liver metabolism, immune clearance, or clinical side effects.

Much of the evidence behind popular unapproved peptides comes from cell cultures and test tubes rather than people. A 2025 systematic review of BPC-157 in orthopaedic sports medicine included 36 studies, of which 35 were preclinical (cell or animal work) and only one was clinical. When a product page says “studies show”, the first question is what kind of studies they were.

In vitro experiments answer narrow questions: does a peptide bind a receptor, or switch on a signal in these cells at this concentration? They cannot show whether the peptide survives digestion or enzymes in the blood, reaches the target tissue, or produces concentrations similar to those used in the dish. They also leave out the immune system, the liver and the kidneys, which shape what a peptide does in a body.

None of this makes in vitro work useless. FDA lists in vitro and in vivo studies as the two types of preclinical research used to look for toxicity before a drug is tested in people, and every approved peptide passed through this stage. The problem arises when an early, exploratory result is presented as if it were the conclusion.

“It worked on human cells, so it will work in humans”

Using human cells makes an experiment more relevant, but cells in a dish lack circulation, metabolism, immune responses and the barriers a peptide must cross in the body. Concentrations that act in culture may be unreachable or unsafe in a person. Whether an effect carries over can only be shown in animal studies and, ultimately, clinical trials.

“Lab studies prove it is safe”

In vitro toxicity screens can flag obvious problems, but they cannot capture effects that depend on whole organs, long-term exposure or the immune system. For BPC-157, a 2025 systematic review found preclinical safety studies but no clinical safety data in humans. Absence of harm in a dish is not evidence of safety in people.

“In vitro means bad science”

In vitro studies can be rigorous, well controlled and essential, and drug development depends on them to understand mechanisms and screen candidates. The limitation is not quality but scope: they answer early questions about what a molecule can do, not whether it helps or harms patients.

What does in vitro mean?

In vitro is Latin for “in glass”. It describes experiments done outside a living organism, such as on isolated cells, tissues or purified molecules in dishes, tubes or plates. In peptide research, typical examples include receptor-binding assays, enzyme stability tests and cell culture experiments that measure signalling or growth.

What is the difference between in vitro and in vivo?

In vitro studies take place outside a living organism, using cells or molecules in a controlled laboratory setting. In vivo studies take place inside a living organism, from laboratory animals to human trial participants. In vitro work is faster and more controlled; in vivo work captures metabolism, circulation and whole-body effects that cell experiments cannot.

Is BPC-157 research mostly in vitro?

BPC-157 research is mostly preclinical, a mix of cell culture and animal studies. A 2025 systematic review identified 35 preclinical studies and one clinical study, a small retrospective report of 12 patients with knee pain, and found no clinical safety data. BPC-157 is not FDA-approved for any use.

Why do drug developers use in vitro studies?

In vitro studies let researchers screen many candidates quickly, measure how strongly a molecule binds its target, explore mechanisms and look for early signs of toxicity, all without exposing animals or people. They form the first layer of preclinical research, and promising results are then tested in animals before any human trial can begin.