X0306 4 2015-07-27 0001594864 Juno Therapeutics, Inc. JUNO 0001239241 EVNIN ANTHONY B C/O VENROCK 3340 HILLVIEW AVENUE PALO ALTO CA 94304 1 0 0 0 Common Stock 2015-07-27 4 S 0 80740 48.26 D 146614 I By Funds Common Stock 2015-07-27 4 S 0 146614 47.82 D 0 I By Funds Common Stock 75000 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by Venrock Healthcare Capital Partners, L.P. ("VHCP") and VHCP Co-Investment Holdings, LLC ("VHCP Co-Invest") on May 18, 2015. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $48.07 to $49.06, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) - (6) to this Form 4. On July 29, 2015, VHCP distributed an aggregate of 493,147 shares of the common stock of the Issuer to its respective partners pro rata based on their respective interests in VHCP (the "VHCP Distribution"). In connection with the VHCP Distribution, VHCP Management, LLC ("VHCP Management"), the general partner of VHCP, recevied an aggregate of 137,148 shares of the Issuer. Dr. Evnin did not receive any shares of the Issuer in connection wtih the VHCP Distribution, and with respect to Dr. Evnin, the VHCP Distribution did not represent a change in beneficial ownership. Consists of 0 shares held by VHCP and 58,171, shares held by VHCP Co-Invest and 88,443 shares held by VHCP Management. VHCP Management is the general partner of VHCP and the manager of VHCP Co-Invest and may be deemed to beneficially own these shares. The reporting person is a member of VHCP Management and may be deemed to beneficially own these shares. The reporting person disclaims beneficial ownership of these shares except to the extent of his indirect pecuniary interest therein. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $47.50 to $48.06, inclusive. Consists of 0 shares held by VHCP, 0 shares held by VHCP Co-Invest and 0 held by VHCP Management. VHCP Management, is the general partner of VHCP and the manager of VHCP Co-Invest and may be deemed to beneficially own these shares. The reporting person is a member of VHCP Management and may be deemed to beneficially own these shares. The reporting person disclaims beneficial ownership of these shares except to the extent of his indirect pecuniary interest therein. /s/ Anthony B. Evnin 2015-07-29