UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): November 4, 2015

Juno Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

307 Westlake Avenue North, Suite 300

Seattle, Washington 98109

(Address of principal executive offices, including zip code)

(206) 582-1600

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

On November 10, 2015, Juno Therapeutics, Inc. (“Juno”) announced its financial results for the quarter ended September 30, 2015. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information in Item 2.02 of this Form 8-K (including Exhibit 99.1) shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference under the Securities Act of 1933, as amended, except as expressly set forth by specific reference in such a filing, regardless of any general incorporation language in any such filing, unless Juno expressly sets forth in such filing that such information is to be considered “filed” or incorporated by reference therein.

(e)

Change in Control and Severance Plan

On November 4, 2015, Juno’s Board of Directors (the “Board”) adopted a change in control and severance plan (the “Severance Plan”) applicable to Juno’s employees with a rank of vice president, an equivalent title, or a more senior title, including Juno’s Chief Executive Officer (“CEO”) and other officers under Section 16 of the Exchange Act (“Section 16 Officers”).

Under the plan, for the period commencing from the closing of a “Change in Control” (as defined in the Severance Plan) until 12 months following a Change in Control (the “change in control period”) if any plan participant is terminated for any reason other than “Cause” (as defined in the Severance Plan), death or disability or a plan participant voluntarily resigns for “Good Reason,” the plan participant would be entitled to receive severance benefits. Upon the occurrence of such an event, each plan participant is entitled to receive the severance benefits set forth in the table below, provided that such benefits are more favorable than the plan participant would be entitled to receive under his or her employment contract with Juno:

Additionally, with respect to any unvested equity award granted after November 4, 2015 that is held by a plan participant who remains a service provider of Juno through the closing of a Change in Control, 25% of the unvested shares subject to such award will become vested and exercisable immediately prior to the Change in Control. Further, if any unvested equity award is not assumed by the acquirer as part of the transaction, all of the unvested shares subject to such award will become vested and exercisable immediately prior to the Change in Control.

Further, under the Severance Plan, if, outside the change in control period, any plan participant is terminated for any reason other than Cause, death or disability, the plan participant would be entitled to receive severance benefits. Upon the occurrence of such an event, each plan participant is entitled to receive the severance benefits set forth in the table below, provided that such benefits are more favorable than the plan participant would be entitled to receive under his or her employment contract with Juno:

Pursuant to the Severance Plan, in order to receive the severance benefits, each plan participant must (i) comply with certain confidentiality, non-solicitation, non-competition, and non-disparagemeent requirements for a period equal to the length of time that the participant continues to receive severance benefits, and (ii) sign and not revoke a release of claims in Juno’s favor within the timeframe set forth in the Severance Plan.

The Severance Plan may not be amended in a manner that materially diminishes the rights of a plan participant under the Severance Plan without the plan participant’s written consent.

(d) Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EXHIBIT INDEX