michel vounatsos joins us now.e first alzheimer's drug approved in 18 years, the first ever to potentially slow the course of the week and this is a controversial decision how are you looking at this moment this historic moment for alzheimer's disease and the people saying this was the wrong decision by the fda and they need more data >> thank you, meg, for having me it is a historic day for the company. i want to applaud the amazing job made by the colleagues why it is an honor to be leading the company at this stage but today i want to think first about the patients, the cavegivers and the families after almost two decades without any innovation it is a new day, it is some hope finally for the patients and families. it is a new chapter that is being opened that we are going to write together with the patients and the families and the caregivers. >> now the fda approved the drug in a creative new pathway as an accelerated approval approved on the fact to clear plaques from the brain and should confer a clinical be

anna: that was the biogen ceo michel vounatsos. sam joins us. to it everything, he is a step closer to treating alzheimer's. we saw a significant stock price move. how excited are you about this development? >> i wish i was a bit more excited than i am, because i have been a long-term critic, not of the idea obviously of trying to treat alzheimer's disease, but the idea that the data are controversial. no one sees more data than the fda does, however, the fda convened a panel of experts during the fourth quarter and ask them directly " do you think this drug should be approved?" they said no. what is the point of the fda having these extra panels, if they ignore what they say? anna: what is so controversial about it? what is -- >> two trials were conducted -- one of them failed, one did not. that is not the way trials are done. you say " if this drug works, we are expected to do -- we expected to do -- you say, " if this drug works, we expect it to do x." if you do not find x you cannot go looking for y and z. anna: how unusual is it that the fd