Why bluebird bio's Shares Have Tumbled 11.9% in 2018 So Far

Why bluebird bio's Shares Have Tumbled 11.9% in 2018 So Far

Source: 
Motley Fool
snippet: 

Although the data from bluebird bio so far looks good, investors have been ratcheting back exposure to the company to reflect what's emerging to be a very competitive marketplace.