Exhibit 10.20

SECOND AMENDMENT TO OFFICE LEASE
This Second Amendment to Office Lease (this "Second Amendment") is entered into
effective as of the 20th day of November, 2014 (the “Effective Date”), by and
between BXP 601 & 651 GATEWAY CENTER LP, a Delaware limited partnership,
formerly known as GATEWAY CENTER, LLC, a Delaware limited liability company
("Landlord"), and IMMUNE DESIGN CORP., a Delaware corporation ("Tenant").

RECITALS

A.    Landlord and Tenant entered into that certain Office Lease dated November
21, 2013, as amended by that certain First Amendment to Office Lease dated
October 27, 2014 (the “First Amendment”) (collectively, the "Original Lease"),
whereby Landlord leased to Tenant and Tenant leased from Landlord the premises
located in the office building having an address of 601 Gateway Boulevard (the
“Building”) containing approximately 9,640 rentable square feet of space located
on the second (2nd) floor of the Building and commonly known as Suite 250, as
further described in the Lease (the “Premises”).

B.     The parties wish to amend the Original Lease to modify the definition of
the New Premises Commencement Date, and in connection therewith Landlord and
Tenant desire to amend the Original Lease on the terms and conditions contained
herein.

NOW, THEREFORE, in consideration of the mutual covenants and agreements herein
contained, and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

AGREEMENT

1.    Recitals. The foregoing recitals are true and correct and are incorporated
herein by this reference.

2.     Defined Terms. All capitalized terms used in this Second Amendment that
are not defined herein shall have the meanings as defined in the Original Lease.

3.    New Premises Term. As of the Effective Date, Section 4 of the First
Amendment shall be deleted in its entirety and replaced with the following:

“New Premises Term. The term of Tenant's lease of the New Premises shall
commence on the date (the "New Premises Commencement Date") which is the earlier
to occur of (a) the date upon which the improvements to the New Premises are
"Substantially Complete" (as defined in Section 7.2 below), or (b) the date upon
which Tenant first commences to conduct business in the New Premises. Landlord
and Tenant acknowledge that the Lease Term for the Original Premises is
scheduled to expire on January 31, 2018, pursuant to the terms of the Lease.
Notwithstanding anything to the contrary set forth in the Lease, the Lease Term
for the New Premises shall expire on (i) the day immediately preceding the fifth
(5th) anniversary of the New Premises Commencement

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Date, if the New Premises Commencement Date falls on the first day of a calendar
month, or (ii) the last day of the month in which the fifth (5th) anniversary of
the New Premises Commencement Date occurs, if the New Premises Commencement Date
falls on any day other than the first day of a calendar month, unless sooner
terminated as provided in the Original Lease, as amended by this Second
Amendment (the “New Premises Lease Expiration Date”). The period of time
beginning on the New Premises Commencement Date and ending on the New Premises
Lease Expiration Date shall be referred to herein as the “New Premises Term.”
Consequently, effective upon the New Premises Commencement Date, all references
in the Lease to the “Lease Term” shall mean and refer to the New Premises Term.”

4.    Counterparts. This Second Amendment may be executed in counterparts with
the same effect as if both parties hereto had executed the same document. All
counterparts shall be construed together and shall constitute a single
agreement.
5.    No Change. Except as set forth herein, all of the terms and conditions of
the Lease remain unchanged and in full force and effect.

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IN WITNESS WHEREOF, Landlord and Tenant have executed this Second Amendment as
of the day and date first written above.
"Landlord":

BXP 601 & 651 GATEWAY CENTER LP,
a Delaware limited partnership

BY: BXP CALIFORNIA GP LLC,
a Delaware limited liability company,
its general partner

BY: BOSTON PROPERTIES LIMITED PARTNERSHIP,
a Delaware limited partnership,
its sole member

BY: BOSTON PROPERTIES, INC.,
a Delaware corporation,
its general partner

BY: /s/ Rod C. Diehl
Name: ROD C. DIEHL
Title: SENIOR VICE PRESIDENT, LEASING
   

“Tenant":

IMMUNE DESIGN CORP.,
a Delaware corporation
By: /s/ Stephen R. Brady
     Name: Stephen R. Brady
     Title: CBO
By: /s/ Richard T. Kenney, MD
     Name: Richard T. Kenney, MD
     Title: Chief Medical Officer
 

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