X0306 4 2017-05-30 0 0001594864 Juno Therapeutics, Inc. JUNO 0001189130 FLATLEY JAY T C/O 400 DEXTER AVENUE NORTH SUITE 1200 SEATTLE WA 98109 1 0 0 0 Common Stock 2017-05-30 4 P 0 10000 22.92 A 31500 I By the Flatley Family Trust This Form 4 is being filed to report a transaction that occurred on May 30, 2017. This transaction was executed in multiple trades at prices ranging from $22.8787 to $22.9262. The price reported above reflects the weighted average purchase price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. /s/ Zachary D. Hale, attorney-in-fact 2018-01-30