Update (9:38 a.m.): Updated with Wednesday market open information.
The stock was up 2.91% to $74.30 at 9:37 a.m. on Wednesday.
A series of clinical trials will test the combination of Bristol-Myers Squibb's Opdivo with Nektar's NKTR-214 in multiple tumor types.
The company has spent $600 million weighing a potential breakup.
Jefferies increased AstraZeneca's (AZN) stock rating to 'buy' this morning.