Every approved medical treatment that exists today – whether for cancer, diabetes, rare diseases or infections – started with clinical trials.
And that process began with a phase 1 clinical trial.
This stage is the first time a new drug/biologic or therapy is tested in people, and while it’s often less talked about than during later phases, phase 1 is absolutely critical – especially for rare cancers like mesothelioma.
Phase 1 clinical trials are where researchers ask the most basic, but most important, question: Is this treatment safe for humans?
What Is a Phase 1 Trial?
Phase 1 trials are the earliest stage of human testing. After a drug has gone through both lab research and animal studies, it enters this phase to begin testing in a small group of people.
The main goal of phase 1 is safety rather than whether the treatment works. Researchers look at how the body handles the drug, how long it stays in the system, and what side effects it might cause.
These trials typically involve smaller cohort sizes of 20-100 participants, depending on the disease and how common it is. For instance, phase 1 mesothelioma clinical trials generally involve 15-30 participants since mesothelioma is rare and the population pool is limited.
In most non-cancer studies, healthy volunteers are enrolled. In cancer and rare disease trials, the participants are often patients with advanced disease who have exhausted standard treatment options..
Why Phase 1 Trials Matter?
It’s easy to overlook phase 1 trials because they don’t usually grab headlines. The results won’t lead to an FDA approval just by nature of the three-phase process.
However, phase 1 studies lay the groundwork for every step that follows. Without the information collected here, you can’t move forward safely or responsibly.
Some of the key things researchers learn in this phase include:
- The right dose range
- How the drug moves through the body (absorption, metabolism, elimination)
- Potential side effects, both expected and unexpected
- The safest way to give the treatment (by mouth, IV, injection, etc.)
Phase 1 is also when scientists determine the maximum tolerated dose, meaning how much can be given before the side effects become too severe. They’re also trying to identify any early warning signs of drug toxicity.
Safety Comes Before Efficacy
It’s natural to want to know if a new drug works. However, that’s not what phase 1 trials are designed to prove. In this phase, any sign of benefit – such as a tumor shrinking or symptoms improving – is a bonus but not the main objective. If those things happen, they get documented and may help inform future studies.
The top priority in phase 1 clinical trials is minimizing harm while understanding how the drug behaves in real people. This helps researchers set the stage to enter phase 2, where the drug’s effectiveness becomes a bigger part of the equation.
Why Are Phase 1 Clinical Trials Small?
It’s important to note that the small sample size in phase 1 trials is intentional. These studies primarily aim to evaluate the safety, tolerability and biological reaction of new treatments rather than a drug’s efficacy.
For instance, a phase 1 study investigating the combination of chemotherapy drugs pemetrexed and carboplatin in patients with malignant pleural mesothelioma enrolled just 27 patients to determine the maximum tolerated dose and assess safety and efficacy. Similarly, the PACLIMES trial, which explored the use of paclitaxel-loaded mesenchymal stromal cells in pleural mesothelioma, planned to enroll 9-18 patients depending on dose-limiting toxicities observed.
What Happens After Phase 1 Studies?
If a drug clears phase 1 successfully – demonstrating an acceptable safety profile – and researchers learn enough to move forward, it can proceed to phase 2. That’s where larger groups of patients are involved, and the focus shifts toward how well the drug works in addition to its safety. But phase 1 is what makes that possible. Without solid safety and dosing data, there’s no path forward.
Phase 1 Clinical Trials In Summary
Phase 1 clinical trials are the quiet beginning of nearly every new treatment. They don’t always get much attention, but they play a huge role in getting promising science from the lab to the real world. These early trials are where ideas get tested against reality, risks are weighed, and researchers take the first steps toward a treatment that could one day save lives.
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