JPMorgan analyst Eric Joseph views the after-market rally of 65% in shares of Acceleron Pharma as "somewhat excessive" if sustained. While the pulmonary arterial hypertension top-line data is a "clear win," the strong reaction is potentially reflective of rising takeover expectations, Joseph tells investors in a research note. The analyst awaits fuller Phase 2 data to better inform sotatercept's probability of success and commercial penetration assumptions. He keeps an Overweight rating on Acceleron, whose stock is up 51% to $79.62 in premarket trading.