Bristol-Myers Squibb Co. announced two deals valued at a total of about $1.6 billion that will further strengthen the drugmaker’s oncology pipeline.

The deals with Flexus Biosciences Inc. and Rigel Pharmaceuticals Inc. will add to Bristol’s portfolio of treatments that use the body’s own immune system to fight cancer. New York-based Bristol has shed units in other areas to focus heavily on a new generation of oncology treatments.

Bristol agreed to acquire closely held Flexus in a deal valued at as much as $1.25 billion, assuming certain development milestones are met, the companies said in a statement Monday. The deal gives Bristol full rights to Flexus’s F001287 immunotherapy, which the company plans to move into human trials in the second half of the year. Current shareholders of Flexus, which is based in San Carlos, California, will be part of a spinoff that will retain its earlier-stage immunotherapies.

Bristol and Flexus predict that the deal will close this quarter.

Bristol also signed a research agreement valued at $339 million, plus royalties, with Rigel, which is based in South San Francisco, California, to develop and sell cancer immunotherapies that for use alone or in combination with Bristol’s melanoma treatments Opdivo and Yervoy, the companies said in a statement. Bristol will gain the rights to therapies derived from Rigel’s portfolio of TGF beta receptor kinase inhibitors.

Bristol this month said its hepatitis C treatment daclatasvir would lose a special designation from the U.S. Food and Drug Administration as a breakthrough therapy that can lead to faster market approval. The announcement was made after Gilead Sciences Inc. and AbbVie Inc. gained clearance to sell medications to treat the disease that were more convenient than those already on the market.

Rigel’s stock rose 40 percent to $3.56 at 9:50 a.m. in New York, its biggest intraday gain since December 2007. Bristol’s shares were up less than 1 percent to $60.82.