Shares in Sierra Oncology Inc. (NASDAQ:SRRA) surged 38.5% to $54.75 on April 13 as Glaxosmithkline plc made a $55-per-share offer for the company, which values it at $1.9 billion. The offer represents a premium of about 39% on Sierra’s April 12 closing share price of $39.52 and a premium of about 63% over its volume-weighted average share price over the last 30 trading days.