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Keryx Biopharmaceuticals Inc. Message Board

  • ockerfan ockerfan Feb 2, 2012 12:38 PM Flag

    What date do you start to feel very comfortable?

    I have been asking myself and been asked by other people at what date for the 360th event do I start to feel very secure in my belief that we will have a successful outcome. We all know that with biotech you can never say never. But one of the tests that I have done is a basic smell test. It goes like this: assume for a moment that there is no drug advantage. What date would you have to get to to have a 7 month median survival for the whole trial -- for the aggregate of both the control and the drug group assuming no advantage? When I model with the following assumptions: 1% die in month 1, 4% in month 2, 6% in month 3, 8% in month 4, 9% in month 5, 10% in month 6, 12% in month 7, 9% in month 8, 7% in month 9, 5% in month 10, 5% in month 11, 4% in month 12, 3 % in month 13, 2% in months 14,15 and 16, 1% in each of months 17 through 22 and 5% live for years, I get a 7 month median survival with the 360th even occurring in the first week of March. Now I know these numbers are not exact... but the key is, they are reasonable. They try to solve with a projected median rather than solve for the 360th event and determine the median ex post. The assumptions provide for a long survival tail >20% beyond 1 year,10% still surviving at month 18 and 5% superheros who live for years. And they provide for a smooth survival curve that is at least broadly consistent with the survival curves that have been observed in earlier trials. A couple of interesting things: the model yields a death count of 163 in the first week in August, consistent with what the company reported. (When I tried to solve for a 6 month aggregate median survival I was getting 179 events in the first week in August -- too big a difference from the 163 reported number. The 6 month aggregate median predicts a 360th event in mid Feb, which I don't think is going to happen, but even if it does there is a good chance that we will be able to achieve success-depending on the actual median of the control group)
    Now comes the smell test part of my 7 month model. I know with a high degree of certainty that the control group is NOT going to achieve median survival of 7 months. That long a period would be hugely inconsistent with anything that has been observed for late stage mcrc patients in any reasonably sized trial that has ever been run. With that high degree of certainty I then do some analysis. If the control group comes in with a median survival of 5 months then by definition the drug group must have come in with some number closer to 9 months (I will leave it to the mathematicians to figure out the exact number) for the whole trial to have achieved a 7 month aggregate median. Maybe 5 months is too much to hope for for the control. But if the median survival was even an unusually long 6 months for the control group (far longer than I am expecting), then you would need a median survival of over 8 months for the drug group to get the aggregate of 7 months. What I am essentially saying is that though I believe we can achieve success if the 360th event occurs as early as next week, if this thing gets into early March,which I believe that it will, we are in very very good shape. That is just my view anyway.

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