Preclinical

Preclinical research comprises the stage of biomedical discovery that precedes human clinical testing. It includes in vitro biochemical and receptor assays, cell culture experiments, and in vivo animal disease models (typically rodents, rabbits, canines, or non-human primates). Preclinical testing evaluates target validation, pharmacological mechanism, allometric dosing, and Good Laboratory Practice (GLP) toxicology.

Over 85% of compounds that demonstrate promising results in preclinical animal models fail when tested in human clinical trials due to lack of efficacy or unexpected human toxicity.

Most of the excitement around peptides such as BPC-157 and TB-500 rests on preclinical work. A 2025 systematic review of BPC-157 in orthopaedic sports medicine included 36 studies, of which 35 were preclinical and only one involved people, and it found no clinical safety data. When a product claim cites “dozens of studies”, checking whether any were done in humans is often the single most useful step.

Preclinical results are a filter, not a verdict. Drug developers use cell and animal experiments to decide which compounds deserve human testing, yet even candidates that pass this stage usually fail: around 90% of drugs that enter clinical trials never reach approval. A promising rat study is therefore a reason to run human trials, not evidence that the effect will appear in people.

Animal studies also differ from real-world use in ways that matter. They often use young, healthy, genetically similar animals, standardised injuries, short follow-up and exposures that may not match what people actually take. The FDA notes that preclinical studies are usually not very large and centre on establishing toxicity before human testing, so they are not designed to show long-term safety in people.

“Proven in animals means proven”

Animal and cell studies show what can happen under specific laboratory conditions. They cannot confirm that an effect occurs in humans, at realistic exposures, or that it outweighs the risks. Many compounds that look effective and safe in animals fail in human trials, through lack of efficacy or unexpected toxicity, which is exactly why clinical trials are required before approval.

“No side effects in animal studies means it is safe for people”

Preclinical safety testing is designed to catch obvious toxicity before first use in humans, not to rule out rare, delayed or human-specific harms. The 2025 BPC-157 systematic review noted that preclinical safety studies reported no adverse effects across several organ systems, yet no clinical safety data existed. An absence of observed harm in rats is not evidence of safety in humans.

“Preclinical research is bad research”

Preclinical work is essential, and well-designed animal and laboratory studies are rigorous science. The problem is not the research but how it is used. Treating preclinical findings as a basis for human use skips the clinical trials that exist precisely to test whether laboratory results hold up in people, in realistic conditions, with proper safety monitoring.

What does preclinical mean in drug development?

Preclinical refers to the research stage before a drug is tested in people. It includes in vitro work, such as cell and receptor assays, and in vivo studies in animals. The FDA requires preclinical laboratory studies to follow Good Laboratory Practice regulations, and the results are used to decide whether a compound is safe enough to move into human clinical trials.

Has BPC-157 been tested in humans?

Barely. A 2025 systematic review identified 36 relevant studies of BPC-157 for musculoskeletal injuries: 35 were preclinical and one was a small retrospective human report in which 7 of 12 patients with knee pain said they had relief. The review found no clinical safety data. BPC-157 is not FDA-approved, and its effects in people remain unproven.

What percentage of drugs fail after preclinical testing?

Estimates vary, but a widely cited 2022 analysis puts the failure rate of drug candidates entering clinical trials at about 90%, with lack of efficacy and unmanageable toxicity in humans among the main reasons. That figure counts only compounds already judged promising enough in preclinical work to be tested in people.

What is the difference between in vitro and in vivo?

In vitro means “in glass”: experiments on cells, tissues or molecules outside a living organism, such as in a dish or test tube. In vivo means “in the living”: studies in whole animals or people. In vivo studies capture absorption, metabolism and whole-body effects that in vitro work misses, but animal in vivo results still may not translate to humans.