When a headline says a peptide “is in clinical trials”, the phase matters more than the phrase. A phase 1 study in a few dozen healthy volunteers and a phase 3 trial in thousands of patients are different universes of evidence. This guide explains what each phase tests, how often drugs make it through, how trials are authorized in Canada, and where the peptides in our research library sit on that ladder.
The short answer
- Clinical trials run in phases: phase 0 (optional, tiny exploratory studies), phase I (safety and how the body handles a drug), phase II (early efficacy and dose-finding), phase III (large confirmatory trials) and phase IV (monitoring after approval).
- Most candidates fail. Of drugs entering phase I between 2011 and 2020, 7.9% reached US approval, and phase II was the biggest hurdle, passed by only 28.9%.
- In Canada, testing an unapproved drug in people requires authorization from Health Canada through a Clinical Trial Application, plus research ethics board approval.
- “In clinical trials” is not the same as approved. Many research peptides never got past early phases, and some programmes were stopped.
The phases at a glance
| Phase | Main question | Typical participants | Typical size |
|---|---|---|---|
| Phase 0 | Does the drug behave in people as lab work predicted? | A few volunteers, very small exposures | Around 10 to 15 |
| Phase I | Is it safe, and how is it absorbed, distributed and cleared? | Healthy volunteers or people with the condition | 20 to 100 |
| Phase II | Does it show an effect, and at what dose range? | People with the condition | Up to several hundred |
| Phase III | Does it work and stay safe in a large, often placebo-controlled trial? | People with the condition, often across many sites | Roughly 300 to 3,000 or more |
| Phase IV | What happens once it is used widely after approval? | Real-world patients | Thousands |
Before any of this, a candidate goes through laboratory and animal work, often called preclinical research. Most research peptides are studied mainly at that stage, which is why our guides mark the level of evidence for each compound. Our guide on how to read a peptide study covers the ladder from cell studies upward.
How many drugs make it
The largest industry analysis of the past decade, by BIO, Informa Pharma Intelligence and QLS Advisors, tracked 12,728 phase transitions in 9,704 development programmes from 2011 to 2020. Overall, 7.9% of candidates entering phase I reached US approval. The odds varied widely by field: about 24% in haematology, but only about 5% in oncology. Other methods give different numbers, and a 2019 analysis by Wong, Siah and Lo estimated 13.8%, but every approach agrees that most candidates fail, and phase II is where most of them stop.
How trials are authorized in Canada
In Canada, a sponsor that wants to test an unapproved drug in people must file a Clinical Trial Application with Health Canada under the clinical trial rules of the Food and Drug Regulations, and the trial also needs approval from a research ethics board. Health Canada reviews the application, typically within 30 days, and can object or ask for changes. Information on authorized trials is published in Health Canada’s Clinical Trials Database, and many trials are also registered internationally on registries such as ClinicalTrials.gov.
A trial authorization is not a marketing authorization. Only once a product has been reviewed and approved for sale does it receive a Notice of Compliance and a DIN; our explainer on what a DIN number means covers that step.
Every compound guide in our library shows where its evidence stands.
Browse the research libraryWhere research peptides sit
| Compound | Furthest stage | Our guide |
|---|---|---|
| Semaglutide | Approved, now in phase IV monitoring | GLP-1 map |
| SS-31 (elamipretide) | Approved in the US in 2025 for Barth syndrome | Mitochondrial peptides |
| Retatrutide | Phase III | TRIUMPH results |
| CJC-1295 with DAC | Phase II, stopped in 2006 | CJC-1295 with DAC |
| MOTS-c analogue CB4211 | Early-phase trials; programme ended in 2023 | MOTS-c |
| BPC-157 | No published controlled efficacy trials | BPC-157 guide |
| Epitalon | Cell and animal studies, mostly from one group | Epitalon |
The pattern is typical. A handful of peptides become approved medicines, more stall in early phases, and many research peptides have never been through controlled human trials at all. Research reagents sold for laboratory use, including the peptides we supply, are not trial products and are not authorized for use in people.
Reading “in clinical trials” claims
- Which phase? A phase I safety study says little about whether a compound works.
- In whom? Healthy volunteers, a specific disease or a narrow subgroup.
- Against what? Placebo-controlled and randomized, or open-label with no comparison.
- Finished and published? Registered, started, stopped and published are four different things.
- Same molecule? Trials of an analogue, such as CB4211, are not trials of the parent peptide.
What a phase tells you
- How far a compound has travelled in formal human testing.
- Roughly what kind of question has been answered so far.
What it does not tell you
- Whether the trial succeeded, or was stopped.
- Whether results apply to a different form or use of the compound.
Research compounds with clinical-trial histories
Several compounds in our catalogue have been tested in human trials as drug candidates, including the four below. We supply them strictly as research reagents, and their Janoshik test reports are listed on our Lab Testing page.
RetatrutideGIP/GLP-1/glucagon triple agonistView product
CagrilintideLong-acting amylin analogueView product
ARA-290EPO-derived research peptideView product
AOD-9604Modified hGH 177–191 fragmentView product
Research use only. Pure Peptides Canada supplies laboratory reagents that are not authorized drugs and are not for human or veterinary use. This article is general education about how clinical research works and is not medical advice.
Frequently asked questions
What are the phases of clinical trials?
Phase 0 is an optional tiny exploratory study; phase I tests safety and how the body handles a drug; phase II looks for an effect and a dose range; phase III confirms benefit and safety in large trials; and phase IV monitors a drug after approval.
What happens in a phase 1 clinical trial?
A small group, typically 20 to 100 healthy volunteers or people with the condition, receives the drug so researchers can study its safety and how it is absorbed, distributed and cleared. Phase 1 is not designed to show whether the drug works.
What percentage of drugs pass clinical trials?
An analysis of 2011 to 2020 data by BIO, Informa Pharma Intelligence and QLS Advisors found that 7.9% of drug candidates entering phase I went on to US approval. Rates vary by disease area and analysis method.
What is a phase 4 trial?
Phase 4 studies take place after a drug is approved, monitoring safety and effectiveness in large, real-world populations and picking up rare side effects that smaller trials miss.
How are clinical trials authorized in Canada?
The sponsor files a Clinical Trial Application with Health Canada, which reviews it, typically within 30 days, and the trial also needs research ethics board approval. Authorized trials are listed in Health Canada’s Clinical Trials Database.
Does “in clinical trials” mean a drug is approved?
No. Approval comes only after successful trials and a regulatory review. In Canada, an approved drug receives a Notice of Compliance and a DIN; a compound in trials, or one whose trials stopped, has neither.
Research peptides, with the evidence in view
Every guide in our library states how far a compound’s evidence goes, from cell studies to approved medicines.
References
- BIO, Informa Pharma Intelligence, QLS Advisors. Clinical Development Success Rates and Contributing Factors 2011–2020. February 2021. PDF
- Wong CH, Siah KW, Lo AW. Estimation of clinical trial success rates and related parameters. Biostatistics. 2019;20(2):273–286.
- US Food and Drug Administration. The drug development process, step 3: clinical research. FDA
- Health Canada. Clinical Trials Database; Food and Drug Regulations, Part C, Division 5 (drugs for clinical trials involving human subjects).
For laboratory research use only. Not for human or veterinary use. This article is educational and is not medical advice.