According to NASDAQ, their holdings as of 3/31 were: BLACKROCK ADVISORS LLC 03/31/2012 62,189 BLACKROCK FUND ADVISORS 03/31/2012 2,125,201 BLACKROCK INVESTMENT MANAGEMENT, LLC 03/31/2012 138,366 Read more: http://www.nasdaq.com/symbol/pphm/institutional-holdings#ixzz20JBJNOvs