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Comment by mbreese | Hacker News Reader

I haven’t read anything about this study, but this is common for highly effective treatments.

Let’s say you have a randomized clinical trial with a control arm (placebo) and test arm (drug). If the vast majority of the test cases do significantly better (like 90% of the test cases), at some point it becomes unethical to continue. Why? Because you already have the evidence that the treatment works, so having the control arm becomes meaningless. You already know that the drug works, so there is no longer a point to collect more data AND you know that the control arm isn’t going to help half the patients. So, you stop the trial early so that you can get started with the approval process so that the drug can get to all patients faster.

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Pardon my naive question, but aren't there more objectives for the clinical trial? Particularly testing for negative side effects? How are those judged if the trial is discontinued?

You don't need people to actually have covid to find side effects. So you don't need sick people in your control arm.

To be cleared though, both arms or the trial are people who have COVID. The control arm is not getting the drug. If there are side effects that occur in some combination with having COVID, they will find those.

Safety continues to be evaluated during Phase 3 (and after approval), but trials don't proceed to Phase 3 without establishing some reasonable baseline for safety in the earlier phases.

Data on the most obvious side effects are collected in the first phase which is a very small group of healthy patients who take the drug under medical supervision in increasing doses until the side effects are so bad they can't keep going. They use this data to establish safety limits for the rest of the clinical trial and continue monitoring the situation until well after the drug is approved.

This was a phase 2/3 trial. So there was some side effect data collected, but enough people went through the trial to see any large/common side effects.

I generally think of the phases like this (this is just how I think of it):

Phase 1 - is it safe? If you don’t see severe toxicity then you can go to phase 2.

Phase 2 - does it work? You look for good outcomes (cures, better survival, etc). If there is significantly better outcomes relative to placebo, then go to phase 3.

Phase 3 - does it work for a large population? What is the appropriate dose? Dialing in the numbers before public release.

Phase 4 - after you’ve made the drug public, monitor the larger population for side effects or adverse events. You can’t hope to cover all patients in a phase 2/3 trial, so you keep monitoring the first waves of patients that get the drug.

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