Pfizer Inc., maker of a top-selling COVID-19 vaccine, will buy all the shares of Trillium Therapeutics Inc. it doesn’t own, gaining the immune cancer drugmaker for an equity value of $2.26 billion. 

Pfizer will pay $18.50 a share for Cambridge, Massachusetts-based Trillium, the companies said Monday in a statement. The price represents a 118% premium to the stock’s 60-day weighted average price. Shares of Trillium nearly tripled to as much as $11.67, while Pfizer rose as much as 3.6% as of 9:38 a.m. in New York. 

Pfizer invested $25 million in Trillium in September as part of its Breakthrough Growth Initiative, when Jeff Settleman, senior vice president of Pfizer’s oncology research and development group, was named to Trillium’s scientific advisory board. 

Trillium’s two lead molecules, TTI-622 and TTI-621, block signaling proteins involved in blood cancers, and are both in human trials across several types of disease. They target CD47, a protein found on some cancer cells that cloaks them from the normal immune response, and send a signal activating the response. 

Early clinical data for both molecules is encouraging and they’re expected to become another important backbone immunotherapy for multiple types of cancer, especially those of the blood, Chris Boshoff, Pfizer’s chief development officer for oncology, said in the statement. 

Blood cancers represent 6% of all tumor diagnoses across the world, according to the statement. Last year, more than 1 million people worldwide were diagnosed with a form of blood cancer and more than 700,000 people died from the disease. 

The move follows Pfizer’s July deal with Arvinas Inc. to develop and commercialize ARV-471, a drug for breast cancer that degrades the hormone estrogen. Pfizer agreed to pay Arvinas $650 million upfront as well as $1.4 billion in potential milestone payments, along with a $350 million equity investment in the biotech.

Pfizer’s oncology portfolio includes 24 approved drugs that yielded about $10.9 billion in revenue last year, up 21% operationally from 2019. During the first half of 2021, global oncology revenues were $6 billion, up 16% operationally from the period a year earlier, the company said. 

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