Afternoon Market Gainers

Bluebird Bio BLUE traded up 49.55 percent to $25.41. Wednesday's IPO for the company was initially priced at $17.

Nektar Therapeutics NKTR rose 9.99 percent to $10.79 after announcing positive top-line results from a human abuse liability (HAL) study for NKTR-181.

Gevo GEVO climbed 9.23 percent to $2.26 after yesterday's announcement that it had resumed commercial production of Isobutanol.

Keryx BioPharma KERX shot up 6.50 percent to $8.16 after analysts at JP Morgan initiated coverage on the stock with an Overweight rating.

MannKind MNKD regained 6.48 percent to $7.03 after yesterday's double-digit drop.