Sec Form 4 Filing - NELSEN ROBERT @ Juno Therapeutics, Inc. - 2018-03-05

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person NELSEN ROBERT 2. Issuer Name and Ticker or Trading Symbol Juno Therapeutics, Inc. [ JUNO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O 8755 WEST HIGGINS ROAD, SUITE 1025 3. Date of Earliest Transaction (MM/DD/YY) 03/05/2018 (Street) CHICAGO, IL60631 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/05/2018( 1 )( 2 ) U 50,824 D $ 87 3,234 D Common Stock 03/05/2018( 1 )( 2 ) D 3,234 D $ 87 ( 3 ) 0 D Common Stock 03/05/2018( 1 )( 2 ) U 10,552,390 D $ 87 0 I Held by ARCH Venture Fund VII, L.P. ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Director Stock Option (Right to Buy) $ 60 03/05/2018( 1 ) D 12,000 ( 5 ) 06/11/2025 Common Stock 12,000 $ 27 ( 5 ) 0 D Director Stock Option (Right to Buy) $ 42.4 03/05/2018( 1 ) D 12,000 ( 5 ) 06/16/2026 Common Stock 12,000 $ 44.6 ( 5 ) 0 D Director Stock Option (Right to Buy) $ 23.29 03/05/2018( 1 ) D 12,000 ( 5 ) 06/15/2027 Common Stock 12,000 $ 63.71 ( 5 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other NELSEN ROBERT C/O 8755 WEST HIGGINS ROAD SUITE 1025 CHICAGO, IL60631 X Signatures /s/ Zachary D. Hale, attorney-in-fact 03/07/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On January 21, 2018, Juno Therapeutics, Inc. (the "Company"), entered into an Agreement and Plan of Merger (the "Merger Agreement") with Celgene Corporation ("Parent"), and Blue Magpie Corporation, a wholly owned subsidiary of Parent ("Purchaser"). On March 5, 2018, Purchaser irrevocably accepted for payment and promptly paid for, all shares of common stock validly tendered and not validly withdrawn pursuant to the Offer (as defined in the Merger Agreement). On March 6, 2018, Purchaser merged with and into the Company pursuant to Section 251(h) of the General Corporation Law of the State of Delaware, with the Company being the surviving corporation (the "Merger") and becoming a wholly-owned subsidiary of Parent. ( 2 )Pursuant to the terms of the Merger Agreement and the Offer, each share of common stock of the Company held by the Reporting Person, other than as described in note (3) below, was validly tendered for $87.00 per share in cash, without interest and subject to withholding of taxes. ( 3 )In accordance with their terms, RSUs held by non-employee directors were converted into the right to receive an amount in cash equal to the product of (i) the number of shares of common stock subject to such RSU and (ii) $87.00. ( 4 )These shares are owned directly by ARCH Venture Fund VII, L.P. ("ARCH Fund VII"). The sole general partner of ARCH Fund VII is ARCH Venture Partners VII, L.P. ("ARCH Partners VII"). The sole general partner of ARCH Partners VII is ARCH Venture Partners VII, LLC ("ARCH VII LLC"). Robert Nelsen is one of the Managing Directors of ARCH VII LLC, and is deemed to have voting and dispositive power over the shares and may be deemed to beneficially own certain shares held by ARCH Fund VII. Robert Nelsen disclaims beneficial ownership of these securities, except to the extent of his pecuniary interest therein. ( 5 )In accordance with their terms, Options held by non-employee directors were converted into the right to receive an amount in cash equal to the product of (i) the number of shares of common stock subject to such Option and (ii) $87.00 less the applicable exercise price.

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