UHN - Trillium expands immunology pipeline and enters stem cell field through in-licensing of two new programs

Toronto, Canada – March 11, 2010 - Trillium Therapeutics Inc. (TTI), a biopharmaceutical
company developing innovative immune-based biologics, today announced that it has entered
into two definitive license agreements with University Health Network (UHN) and The Hospital for
Sick Children (SickKids) in Toronto, Ontario, granting Trillium exclusive worldwide rights to
commercialize two immunology programs in the areas of hematopoietic stem cell transplantation
and cancer.

“We are very excited to have strengthened our immunology franchise and to have reinforced our
existing bond with Toronto’s world-class immunology community. Our productive long-standing
relationship with UHN bodes well for the success of this new collaboration”, commented Dr.
Niclas Stiernholm, Trillium’s CEO. “This transaction exemplifies how ground-breaking Canadian
science can and should be commercialized by our domestic biotechnology industry, something
that must be encouraged and supported also by government and investor groups.”

The first project licensed by TTI is aimed at improving hematopoietic stem cell engraftment by
agonizing a key immunoregulatory pathway and thereby preventing the host immune system from
attacking transplanted stem cells. The second program is focused on the treatment of several
types of cancers by antagonizing the same pathway in cancer stem cells, stimulating the patient’s
own immune system to attack the cancer. Drs. John Dick, and Jean Wang from UHN, and Dr.
Jayne Danska at Sickkids, world renowned scientists in their respective fields and the inventors of
these technologies, first published their initial findings in Nature Immunology in December 2007.
Through companion sponsored research agreements, they will be collaborating closely with
Trillium’s scientific team to advance this cutting-edge science towards testing in humans.

Dr. Christopher Paige, VP Research at UHN stated “We are very pleased to have created this
partnership with a vibrant Canadian biotechnology company like Trillium Therapeutics. It
represents an excellent example of how Research Hospitals like UHN and SickKids can work
together to translate cutting edge research discoveries into new product development
opportunities”. Dr. Janet Rossant, Chief of Research at SickKids added “Research collaborations
between scientists at our institutions have now been extended to development interactions with
the private sector, clearly indicating that we can bring biotherapeutic research and development
together in Toronto”.

Trillium Press Release: http://www.trilliumtherapeutics.com/pdf/UHN.HSCrelease.pdf