William Lis, Chief Executive Officer, Portola Pharmaceuticals, Inc.
It is still meaningful. I mean the drug has to show activity, all indications is that it should. We have the events. The events are occurring, so you know if the drug is dosed appropriately. We should see activity. I think again, it just puts more wind in our sales to push to the finish line if it is successful.
These trials build overtime. The momentum, either positive or negative, builds overtime because they are so large. They are big moving aircraft carriers and now it seems to be building in the positive direction. We can still fail from our operation standpoint or from a clinical standpoint. We could still fail, but certainly, we are building momentum. We are right where we want to be. We could not ask for anything more at this stage but we still have 35% of the way go and we are still in 32 countries and 450 sites. Believe me, it is a bear to manage but so far so good.
Female
Can you help us understand how to understand a concept of conditional probability, where it would be in certain range, you would think you would have to increase the effect size? I mean because you are powered for a certain effect size with the numbers that you are having, right?That is why I am having a little bit of trouble driving why it is not to just a yes-no scenario.
Alexander Gold, Senior Vice President, Clinical Development, Portola Pharmaceuticals, Inc.
Sure. We are not getting too much of the statics. The concept of the conditional probability has to do with, again, this concept of ruling out a low probability of success. What we do is we define what low probability of success means. Our executive committee which is composed of leading academics in the areas – you probably know if you look at our papers – including Bob Harrington, Mike Gibson,Andy Cohen. What they do is they sit down and say, “What is clinically meaningful for patients to prevent their thrombotic events from happening?” Based on that, they define a threshold below which it is really not clinical significant or the probability of success which is something that we would like to not rule out. What I mean by that is not to continue the trial in case there are still possibilities clinically meaningful, if that makes sense to you.
That is really the main concept. If it is beyond that threshold and it is really futile, hence the concept, then do not go on. If there is still a possibility, probability that this drug will prevent VTEs from happening at a reasonable, clinical rate, then that is something we would like to continue and complete the trial.
William Lis, Chief Executive Officer, Portola Pharmaceuticals, Inc.
Let me answer that differently. Again, we are not breaking any new ground here. For 25 years that I am seeing this clinical trial, we have been doing the same thing. To put in terms of what you said, you are expecting a certain relative risk reduction. We are powered 95% to see a 35% relative risk reduction, but that is not what the DS&D is looking at. They are not looking to see a 35% relative risk reduction to say yes or no. We are looking to see some clinical activity that suggests halfway through the trials, but this is only done with 50% of the patients that you are on target to show a clinical benefit and that there is a probability that you can kind of get there. If they see that there is a probability that you cannot get there as Alex, that is really what they are focused on. There is not a probability that can get there within a range, not 35%. There is not a probability that they can get there. That is really what they are looking at. Does that make sense?
Female
We have to guess in part, but under what [off mic] would they say, “You should increase your [off mic].”The probability will be…
