Stocks On the Move: Biogen Inc, AveXis Inc, and Amphastar Pharmaceuticals Inc

U.S. stocks are higher, as tech stocks and homebuilders lead. Among specific equities in focus today are biotech stocks Biogen Inc (NASDAQ:BIIB), AveXis Inc (NASDAQ:AVXS), and Amphastar Pharmaceuticals Inc (NASDAQ:AMPH). Here's a quick look at what's moving BIIB, AVXS, and AMPH.

• BIIB is up 1.4% at $291.42, after the U.S. Food and Drug Administration (FDA) granted approval for its spinal muscular atrophy drug, nusinersen, developed in partnership with Ionis Pharmaceuticals Inc (NASDAQ:IONS). BIIB is up more than 30% since its late-June lows, though the shares still sit below the key $300 level. Option bulls have been betting on more upside, with Biogen Inc's 10-day call/put volume ratio at the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX) of 2.20 sitting in the 84th percentile of its annual range.
  
  
• AVXS is down 6.4% at $49.90, after BIIB's FDA approval. AveXis Inc is currently developing a similar drug, AVXS-101, which would now be the second spinal muscular atrophy drug available on the market, if approved. However, one Chardan analyst thinks AVXS-101 could still clear space in the market, given its lower death rate, which gives it the potential to be a "breakthrough therapy." The Wall Street rookie has tumbled nearly 32% since hitting an all-time peak last month, and short sellers have been piling on. Short interest on AVXS surged 171.95% during the past two reporting periods, and now accounts for 20% of the stock's total available float.

• AMPH is among the worst performers on the Nasdaq, currently trading 9.2% lower at $18.56, on news that the FDA has issued a Complete Response Letter (CRL) denying the biotech's New Drug Application (NDA) (subscription required) for its primatene mist asthma inhaler. Amphastar Pharmaceuticals Inc's CEO said the company will work to address the FDA's concerns by the middle of 2017. AMPH is still up more than 75% since its early March lows, though the shares now sit below the $19.50 level that has acted as support since a mid-November bull gap. Short sellers are likely cheering today's move, with AMPH's 2.7 million shorted shares accounting for more than 7.4% of AMPH's float, which would take just under two weeks of trading to cover, at the stocks' average daily volume.