Phase 1 trials are the earliest trials in the life of a new drug or treatment. Phase 1 is sometimes written as phase I. They are usually small trials, recruiting anything up to about 30 patients, although often a lot less. The trial may be open to people with any type of cancer.
When laboratory testing shows that a new treatment might help treat cancer, phase 1 trials are carried out to find out:
- The safe dose range
- The side effects
- How the body copes with the drug
- If the treatment shrinks the cancer
Patients are recruited very slowly onto phase 1 trials. So although they don't recruit many patients, they can take a long time to complete. The first few patients to take part (called a 'cohort' or group) are given a very small dose of the drug. If all goes well, the next group have a slightly higher dose. The dose is gradually increased with each group. The researchers monitor the effect of the drug, until they find the best dose to give. This is called a dose escalation study.
In a phase 1 trial, you may have lots of blood tests, as the researchers look at how the drug is affecting you. They also look at how your body copes with, and gets rid of the drug. They record any side effects.
People taking part in phase 1 trials often have advanced cancer and have usually had all the treatment available to them. They may benefit from the new treatment in the trial, but many won't. Phase 1 trials aim to look at doses and side effects. This work has to be done first, before we can test the potential new treatment to see if it works. Phase 1 trials are important because they are the first step in finding new treatments for the future.
Phase 2 trials
Not all treatments tested in a phase 1 trial make it to a phase 2 trial. Phase 2 is sometimes written as phase II. These trials may be for people who all have the same type of cancer, or who have several different types of cancer. Phase 2 trials aim to find out:
- If the new treatment works well enough to test in a larger phase 3 trial
- Which types of cancer the treatment works for
- More about side effects and how to manage them
- More about the best dose to use
Although these treatments have been tested in phase 1 trials, you may still have side effects that the doctors don't know about. Drugs can affect people in different ways.
Phase 2 trials are often larger than phase 1. There may be up to 100 or so people taking part. Sometimes in a phase 2 trial, a new treatment is compared with another treatment already in use, or with a dummy drug (placebo). If the results of phase 2 trials show that a new treatment may be as good as existing treatment, or better, it then moves into phase 3.