McKesson (MCK - Get Report) led healthcare companies in pre-market moves Thursday morning, falling 6.95% ahead of market's open to $151.10 per share. The company reported better-than-expected earnings Wednesday after market's close, and announced a $1.1 billion acquisition of CoverMyMeds. McKesson has fallen 9% in the past year. 

Meanwhile, Bristol-Myers Squibb (BMY - Get Report) , which reported an earnings miss and cut 2017 guidance Thursday morning, also saw shares fall 1.8%, hitting $49.55 per share ahead of market's open. Bristol has seen its shares fall 19% in the past year. 

Midcap Varian Medical Systems (VAR - Get Report) was also having a rough morning. The company missed on fourth quarter earnings and revenue, and subsequently saw shares fall 5.5% ahead of opening. Varian was trading at $87.26 ahead of market's open. The company's shares have climbed 18% in the past year. 

Meanwhile, Merrimack Pharmaceuticals (MACK) was having a decent morning. The company's share price climbed 0.6 % ahead of market's open, but the stock was trading at high volume. Merrimack saw shares hit $3.22 apiece. The stock has lost nearly half of its value in the past year. 

Biogen (BIIB - Get Report) was positive ahead of market's open. The shares climbed 1.7% , hitting $278 apiece on decent earnings and revenue guidance.