Juno Therapeutics Adds Antibody Engineering Capabilities Through Acquisition of X-BODY

-- Transaction Accelerates Capabilities to Create Novel Fully Human CAR T and TCR Constructs --
-- Initial Payment of Approximately $21 Million in Cash and 439,265 Shares of Juno Stock --

SEATTLE, June 2, 2015  -- Juno Therapeutics, Inc. (JUNO), a biopharmaceutical company focused on re-engaging the body's immune system to revolutionize the treatment of cancer, announced today that it has acquired X-BODY, Inc., a privately held biotechnology company with nine employees based in Waltham, Massachusetts. The acquisition furthers Juno's strategy of investing in technologies that augment the company's capabilities to create best-in-class engineered T cells against a broad array of cancer targets. The acquisition brings in-house to Juno an innovative discovery platform that interrogates the human antibody repertoire, rapidly selecting fully human antibodies with desired characteristics, even against difficult targets.

"The X-BODY acquisition brings protein engineering capabilities to Juno that meaningfully improve our ability to generate novel CAR T and TCR product candidates, which will help optimize potential therapies against both current and new targets," said Hans Bishop, CEO of Juno. "We are delighted to welcome our new Massachusetts-based employees, who have impressed us with the quality of their science and output since our partnership began in early 2014."

Juno will incorporate this platform into its process for creating CAR T constructs, using it to generate new binding domains from fully-human naive single chain variable fragment (scFv)-formatted libraries. Fully-human scFv's have the potential for reduced immunogenicity and improved CAR T cell in vivo persistence. Juno also plans to continue to explore the broader application of the technology to alternative antigen-binding platforms, including its TCR platform.

"We are excited to be a part of the Juno team. This union will advance our technology's utility in this new, potentially disruptive area of medicine, accelerating the battle against cancer," said Yan Chen, M.D., Ph.D., formerly SVP Research of X-BODY, and now Head of Biotherapeutic Discovery at Juno. "Our goal has always been to use our technology to develop best-in-class medicines to improve human health, and joining Juno only strengthens that focus."

Since its founding in 2008, by Richard W. Wagner, Ph.D., Brant Binder, and Gordon Binder, X-BODY has been focused on the discovery of human monoclonal antibodies against challenging membrane targets, and more recently the discovery of TCR binding domains. X-BODY has developed technologies that produce highly stable and functional binding molecules. X-BODY uses robust DNA-encoded human naive libraries to identify functionally active and selective human binding domains and human monoclonal antibodies against key therapeutic targets.

The initial consideration for the X-BODY acquisition was approximately $21 million in cash and 439,265 shares of Juno stock. Juno has also agreed to make success-based payments in cash to the sellers upon the achievement of certain research, clinical, and regulatory milestones for products that are generated using the X-BODY technology, as well as certain additional cash payments following commercialization.

About Juno Therapeutics, Inc.

Juno Therapeutics is building a fully integrated biopharmaceutical company focused on revolutionizing medicine by re-engaging the body's immune system to treat cancer. Founded on the vision that the use of human cells as therapeutic entities will drive one of the next important phases in medicine, Juno is developing cell-based cancer immunotherapies based on chimeric antigen receptor and high-affinity T cell receptor technologies to genetically engineer T cells to recognize and kill cancer. Juno is developing multiple cell-based product candidates to treat a variety of B-cell malignancies as well as solid tumors. Several product candidates have shown compelling evidence of tumor shrinkage in the clinical trials in refractory leukemia and lymphoma conducted to date. Juno's long-term aim is to improve and leverage its cell-based platform to develop new product candidates that address a broader range of cancers and human diseases. Juno brings together innovative technologies from some of the world's leading research institutions, including the Fred Hutchinson Cancer Research Center, Memorial Sloan Kettering Cancer Center, Seattle Children's Research Institute, and The National Cancer Institute.

Juno Forward Looking Statements

This press release contains forward-looking statements, including statements regarding Juno's strategy, ambitions, capabilities, and business plans, particularly with respect to Juno's ability to create best-in-class engineered T cells against a broad array of cancer targets, the potential of the acquired technologies and capabilities and the benefits that may be obtained in combining those technologies and capabilities with those of Juno, and the potential of fully human scFvs to reduce immunogenicity and improve CAR T cell in vivo persistence. Forward-looking statements are subject to risks and uncertainties that could cause actual results to differ materially from such forward-looking statements, and reported results should not be considered as an indication of future performance. These risks and uncertainties include, but are not limited to, risks associated with: the success, cost, and timing of Juno's product development activities and clinical trials, and Juno's ability to finance these activities and trials; Juno's ability to obtain regulatory approval for and to commercialize its product candidates; Juno's ability to establish a commercially-viable manufacturing process and manufacturing infrastructure; regulatory requirements and regulatory developments; success of Juno's competitors with respect to competing treatments and technologies; Juno's dependence on third-party collaborators and other contractors in Juno's research and development activities, including for the conduct of clinical trials and the manufacture of Juno's product candidates; Juno's ability to effectively integrate the acquired technologies and employees into Juno's operations and strategy and to realize the intended benefits of the transaction; Juno's ability to obtain, maintain, or protect intellectual property rights related to its product candidates; amongst others. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Juno's business in general, see Juno's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 12, 2015 and Juno's other periodic reports filed with the Securities and Exchange Commission. These forward-looking statements speak only as of the date hereof. Juno disclaims any obligation to update these forward-looking statements.

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