Exhibit 10.13

FIRST AMENDMENT TO LEASE

THIS FIRST AMENDMENT TO LEASE (this “Amendment”) is entered into as of this 31st day of July, 2015, by and between BMR-217^th PLACE LLC, a Delaware limited liability company (“Landlord”), and JUNO THERAPEUTICS, INC., a Delaware corporation (“Tenant”).

RECITALS

A. WHEREAS, Landlord and Tenant are parties to that certain Lease dated as of February 2, 2015 (as the same may have been amended, supplemented or modified from time to time, the “Existing Lease”), whereby Tenant leases certain premises (the “Premises”) from Landlord at 1522 217^th Place, Bothell, Washington 98021 (the “Building”);

B. WHEREAS, Landlord and Tenant have determined that it is advisable to perform certain work with respect to the roof and roof membrane of the Building (collectively, the “Roof”) as more particularly described in the scope of work attached hereto as Exhibit A (the “Roof Work”);

C. WHEREAS, pursuant to Section 17.2 of the Lease, Landlord, at Landlord’s sole cost and expense, is responsible for capital repairs and replacements (if necessary, as reasonably determined by Landlord) of the Building roof covering, structural system and membrane;

D. WHEREAS, Landlord and Tenant have agreed that Tenant’s general contractor, BNBuilders (“Contractor”), will perform the Roof Work pursuant to the scope of work attached hereto as Exhibit A (the “Scope of Work”), at Tenant’s cost, and Landlord’s shall reimburse Tenant for the cost of such Roof Work, up to a maximum amount of Five Hundred Thirty-Three Thousand Four Hundred Fifty-Two and No/100 Dollars ($533,452.00) (“Maximum Cost”), on the terms and conditions set forth in this Amendment; and

E. WHEREAS, Landlord and Tenant desire to modify and amend the Existing Lease only in the respects and on the conditions hereinafter stated.

AGREEMENT

NOW, THEREFORE, Landlord and Tenant, in consideration of the mutual promises contained herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, and intending to be legally bound, agree as follows:

1. Definitions. For purposes of this Amendment, capitalized terms shall have the meanings ascribed to them in the Existing Lease unless otherwise defined herein. The Existing Lease, as amended by this Amendment, is referred to collectively herein as the “Lease.” From and after the date hereof, the term “Lease,” as used in the Existing Lease, shall mean the Existing Lease, as amended by this Amendment.

BioMed Realty form dated 3/27/15

2. Performance of Roof Work. Tenant shall cause Contractor to perform the Roof Work in accordance with the Scope of Work and the requirements set forth in Exhibit B attached hereto (the “Additional Roof Requirements”) in a good and workmanlike manner, free from defects and mold, in conformance with all Applicable Laws, permits and standards of the industry, using materials that are new and of good quality. If the Roof Work does not conform to these requirements, it shall be considered defective, and if Landlord delivers written notice of any such defect to Tenant, then Tenant shall cause Contractor to immediately replace and correct such defect at no additional cost to Landlord. Tenant shall cause Contractor to obtain and maintain all permits and licenses required for Contractor to perform the Roof Work, and upon Landlord’s request, Contractor shall produce evidence satisfactory to Landlord of such permits or licenses. Landlord shall cooperate with the permit process, as reasonably necessary. Tenant shall cause Contractor to comply with Landlord’s reasonable safety standards and protocols and to take commercially reasonable steps to protect the Building during the performance of the Roof Work. Tenant hereby assigns to Landlord any warranty for such Roof Work provided by Contractor. Landlord and Tenant hereby approve the Scope of Work. Landlord and Tenant have thoroughly discussed the condition of the Roof and mutually agreed that the performance of the Roof Work as described in the Scope of Work is the appropriate method for remedying any existing defects in the condition of the Roof, and that the performance of the Roof Work by Contractor in accordance with the Scope of Work and Landlord’s reimbursement of cost incurred by Tenant for Contractor to perform such Roof Work as set forth in Section 3 below satisfies any obligations of Landlord under Section 17.2 of the Lease with respect to any such existing defects.

3. Reimbursement of Cost of Roof Work. Upon completion of the Roof Work in accordance with this Amendment, Tenant shall deliver to Landlord an invoice for the cost incurred by Tenant for Contractor to perform such Roof Work, together with reasonable supporting documentation. Within thirty (30) days after receipt of such invoice and supporting documentation, Landlord shall reimburse Tenant for such cost, up to the Maximum Cost. In no event shall Landlord be required to pay any amount for the Roof Work in excess of the Maximum Cost.

4. Roof Maintenance Obligations. From and after the completion of the Roof Work, in addition to any other obligations under the Lease, Tenant shall cause inspections of the physical condition of the Roof to be performed and written inspection reports to be prepared by a licensed roofing contractor reasonably acceptable to Landlord, which shall be a certified or authorized warranty inspector of the Roof system manufacturer (“Roof Maintenance Contractor”), and shall cause a Roof Maintenance Contractor to perform regular maintenance of the Roof, all in accordance with the Additional Roof Requirements; provided, however, that at all times during the Term, notwithstanding anything set forth in the Additional Roof Requirements, Landlord shall have the right to perform its own inspections and maintenance of the Roof, subject to the notice and access provisions in the Lease. Landlord hereby approves Cobra BEC, Inc. as the Roof Maintenance Contractor.

5. No Default. Landlord and Tenant represent, warrants and covenant to one another that, to the best of their respective knowledge, Landlord and Tenant are not in default of any of their respective obligations under the Existing Lease and no event has occurred that, with the passage of time or the giving of notice (or both) would constitute a default by either Landlord or Tenant thereunder.

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6. Notices. Tenant confirms that, notwithstanding anything in the Lease to the contrary, notices delivered to Tenant pursuant to the Lease should be sent to:

Juno Therapeutics, Inc.

307 Westlake Avenue N., Suite 300

Seattle, WA 98109-5219

Attention: Dir. of Eng. and Capital Projects

with a copy to:

Juno Therapeutics, Inc.

307 Westlake Avenue N., Suite 300

Seattle, WA 98109-5219

Attention: General Counsel.

7. Effect of Amendment. Except as modified by this Amendment, the Existing Lease and all the covenants, agreements, terms, provisions and conditions thereof shall remain in full force and effect and are hereby ratified and affirmed. In the event of any conflict between the terms contained in this Amendment and the Existing Lease, the terms herein contained shall supersede and control the obligations and liabilities of the parties.

8. Successors and Assigns. Each of the covenants, conditions and agreements contained in this Amendment shall inure to the benefit of and shall apply to and be binding upon the parties hereto and their respective heirs, legatees, devisees, executors, administrators and permitted successors and assigns and sublessees. Nothing in this section shall in any way alter the provisions of the Lease restricting assignment or subletting.

9. Miscellaneous. This Amendment becomes effective only upon execution and delivery hereof by Landlord and Tenant. The captions of the paragraphs and subparagraphs in this Amendment are inserted and included solely for convenience and shall not be considered or given any effect in construing the provisions hereof. All exhibits hereto are incorporated herein by reference. Submission of this instrument for examination or signature by Tenant does not constitute a reservation of or option for a lease, and shall not be effective as a lease, lease amendment or otherwise until execution by and delivery to both Landlord and Tenant.

10. Authority. Tenant guarantees, warrants and represents that the individual or individuals signing this Amendment have the power, authority and legal capacity to sign this Amendment on behalf of and to bind all entities, corporations, partnerships, limited liability companies, joint venturers or other organizations and entities on whose behalf such individual or individuals have signed.

11. Counterparts; Facsimile and PDF Signatures. This Amendment may be executed in one or more counterparts, each of which, when taken together, shall constitute one and the same document. A facsimile or portable document format (PDF) signature on this Amendment shall be equivalent to, and have the same force and effect as, an original signature.

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IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment as of the date and year first above written.

On this 28 day of July, 2015, before me, the undersigned, a Notary Public in and for the State of Washington, duly commissioned and sworn personally appeared Andy Walker, known to me to be the SVP of Manufacturing/Operations JUNO THERAPEUTICS, INC., a Delaware corporation, the corporation that executed the foregoing instrument, and acknowledged the said instrument to be the free and voluntary act and deed of said corporation, for the purposes therein mentioned, and on oath stated that he/she was authorized to execute said instrument.

I certify that I know or have satisfactory evidence that the person appearing before me and making this acknowledgment is the person whose true signature appears on this document.

WITNESS my hand and official seal hereto affixed the day and year in the certificate above written.

EXHIBIT A

SCOPE OF WORK

Juno 60 mil TPO Replacement Scope

A-1

EXHIBIT B

ADDITIONAL ROOF REQUIREMENTS

General Comments:

Inspections during Performance of Roof Work:

Roof Inspections and Maintenance after Completion of Roof Work:

B-1