Shares of AveXis (AVXS) jumped 16% to $84.44 on Friday morning after the Chicago-based gene therapy company after the market close yesterday reported results from a phase one trial of AVXS-101 in spinal muscular atrophy (SMA) Type 1 and also announced results for the fourth quarter and full-year 2016.

The company said that as of Jan. 20, AVXS-101 "appeared to have a favorable safety profile and to be generally well tolerated, with no new safety or tolerability concerns identified."

Also on Thursday, AveXis reported a fourth-quarter net loss of $25.4 million, or $0.92 per share.

Meanwhile, shares of Amgen (AMGN - Get Report) fell 6.9% to $167.75. The Thousand Oaks, Calif.-based firm said Friday that  its new cholesterol drug Repatha reduced the risk of heart attacks, strokes and other heart-related health problems by 15% compared to a placebo.

Investors were expecting Repatha to show a cardiovascular risk reduction of 20-22%, so the drug's true performance in a population of higher-risk patients is a disappointment from the market's perspective.

Sean Harper, head of research and development at Thousand Oaks, Calif.-based Amgen, pushed back against anticipated negative investor reaction.

In an interview with TheStreet's Adam Feuerstein on Thursday, Harper pointed to additional evidence from the study -- adjusted for what he calls a "treatment lag" -- showing Repatha reduced the risk of heart attack and stroke by 33%.

"There is no legitimate criticism you can make about the efficacy outcome, though you do have to be able to interpret the data," Harper said

Among the other biotech stock movers on Friday were Esperion Therapeutics (ESPR) , whose shares were down 21.4% to $23.30, and Medicines Co. (MDCO) , down 20.8% to $41.67.