After-Hours Stock Movers:
Alpine Immune Sciences (NASDAQ:ALPN) climbed 36%, adding to earlier gains, after it announced an agreement to be acquired by Vertex Pharma (NASDAQ:VRTX) for $65 per share. Vertex declined 1%.
Costco (NASDAQ:COST) climbed 0.8% after it reported March sales and raised its dividend. Total comps were up 7.7%.
Crown Castle (NYSE:CCI) rose 0.3% after it named a new President and CEO, industry veteran Steven J. Moskowitz.
Ashland (NYSE:ASH) rose 1% after it was upgraded to 'overweight' by analysts at Wells Fargo.