What are the phases of clinical trials? CLL expert Dr. Michael Choi outlines the research purpose of clinical trials and what happens in each phase.
Dr. Michael Choi is a hematologist and medical oncologist at UC San Diego Moores Cancer Center. More information on Dr. Choi here.
Dr. Choi, can you please walk us through the phases of a clinical trial and what happens during each phase?
That’s a great question. Yeah, historically, trials have been divided into different phases. The way I think of it is when a drug is first being tested, we don’t want to expose too many people to it, because we’re still learning about the right dose and about its safety. And then, as we learn more and more and maybe get some confirmation that it’s doing what it’s supposed to do, then we have bigger trials and eventually, bring in some comparisons to existing standards.
So, a Phase I trial is usually, I would say, a few dozen patients, getting the drug for the very first time or sometimes for the first time for this diagnosis. Oftentimes, the very first Phase I trials might have a dose escalation component where the first dose or the first group of patients might get a dose that is based on an assurance that it will be – or some confidence that it will be safe and well-tolerated.
Then, as the trial goes on, a higher dose will be used once we see that the previous doses are safe. Now, sometimes, this dose escalation happens in between different groups of patients, and sometimes, some trials will escalate the dose for even within an individual patient. But the basic idea of it is to start at doses that we think will be safe and then to gradually escalate it, again, prioritizing the safety of the patients.
I shouldn’t also – although Phase I trials are designed to determine the safety of a drug, there are many Phase I trials that show clinical activity and benefit to the patients, so I don’t think people should be altogether discouraged from enrolling in a Phase I trial either.
I can also say that some Phase I trials are just looking at a combination of drugs that we have experience with already, but designed or written as a Phase I trial, because we have to confirm the safety of those two drugs. In those trials, the doses might not be that different than what’s used already, and there’s often more expectation of immediate clinical benefit. Phase II trials are where we’re principally looking or usually looking mainly at the response rate or some sort of clinical endpoint, how many patients get into a partial remission, or how many patients get into a complete remission and so on.
And I would say these are usually our trials that are 20, 30, 50 patients, to that effect. And basically, from that group of patients, we can get a pretty good estimate of how effective a drug or a drug combination may be. And then finally, the third type of trial, Phase III trial, is when a new drug or a new combination is compared directly to a different – to what would be considered the standard of care at the time.
So, this is a way that we can get more confidence that this new drug is indeed better than what we’ve been doing up until now.