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Prana Biotechnology Limited Message Board

  • pivalde pivalde Jan 30, 2013 10:26 AM Flag

    small patient numbers in the AD and HD studies

    Big pharma has done ph3 studies with thousands of patients, but the Prana's studies have only 40 AD patients and 100 HD patients including controls. To me it is a sign of confidence about the results they will get. Of course there is also money involved in limiting the numbers but the numbers are not limited because of money. Prof Masters told almost 2 y ago that when you have Pitsburg positive MCI patients and if you have a drug reducing 10% of the amyloid plaques you only need 23 patients to demonstrate it according the power calculations. In the case of a drug with 20% effecacy you will need only 7 cases ( he did not tell how long a follow up time is needed, however).
    In the HD study the numbers are bigger but in fact we have 2 studies. preclinical and the clinical patients and even low dose and high dose. The number 100 is also based on power calculations based on some facts. (pilot cases??)
    It is evident that in neither studies the power calculations are based only on imaging but also on clinical parameters. Prana seems very confident even with these small patient numbers in these studies and to me it is very positive.

    Sentiment: Strong Buy

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    • For a phase 2, considering the nature of the presumed MOA, considering a microcap that skillfully absorbed the dilution and had to harvest grants and private equity (Quintiles), a small trial still translated into meaningful progress and defined a dose response. However, with a minimal designed trial size, hitting the acceptable r values for trial endpoints can be jeopardized if pts drop out during the trial. As you know, SAE may not surface in the small numbers which can bite later on in a much larger Phase 3. Ultimately, it will be the phase 3 that largely feeds the NDA.

      Sentiment: Strong Buy

    • Do the numbers 23 and 7 cited by Masters include control patients? If so, then we're probably safe with just 40 total patients in the AD study.

      Prana probably had to do a balancing act to optimize the size of each trial, based on cost and predicted efficacy. Prana does not have much money, but at the same time they'd want to have a big enough study to provide statistical significance. If the study were too small and stat sig did not get achieved, the time and money spent on the study would have been wasted.

      Sentiment: Buy

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