William Blair analyst Y. Katherine Xu last night initiated shares of Athersys with an Outperform rating. The company's cell therapy candidate MultiStem could, if successful, revolutionize stroke treatment, Xu told investors in a research note. The analyst sees a "reasonable probability of success for MultiStem in light of the challenges of drug development in stroke. Her probability-adjusted net present value model derives a fair value for Athersys shares of $11 at the end of 2017. The stock closed yesterday at $1.18 and is trading up 25c to $1.43 in the pre-market.