X0306 4 2016-11-08 0 0001594864 Juno Therapeutics, Inc. JUNO 0001656998 Azelby Robert C/O 307 WESTLAKE AVENUE N STE 300 SEATTLE WA 98109 0 1 0 0 EVP & Chief Commercial Officer Common Stock 2016-11-08 4 A 0 10000 0.00 A 48640 D Common Stock 2016-11-10 4 S 0 12921 24.135 D 35719 D Stock Option (Right to Buy) 25.29 2016-11-08 4 A 0 40000 0.00 A 2026-11-07 Common Stock 40000 40000 D Represents restricted stock units ("RSUs") granted pursuant to the 2014 Equity Incentive Plan. 25% of the RSUs vest on each anniversary of November 8, 2016. The sale reported on this Form 4 was effected pursuant to an Issuer approved Rule 10b5-1 compliant sell-to-cover award, in order to cover tax withholding incident to the vesting of 38,640 RSUs. The number of shares sold to cover such withholding obligations was determined based on the trade price, which is equal to the average of the high and low prices of the Issuer's common stock on November 2, 2016, the next trading day following the date on which the RSUs vested. 1/48th of the shares subject to the option become vested and exercisable on December 8, 2016 and 1/48th of the shares subject to the option shall vest monthly thereafter. /s/ Zachary D. Hale, attorney-in-fact 2016-11-10