SECOND ADDENDUM

Exhibit 10.40.2

SECOND ADDENDUM

THIS ADDENDUM, made and entered into this 23rd day of October, 2015, to that Lease dated December 16, 2010, by and between CRESTVIEW, LLC, a Colorado limited liability company (herein called “Landlord”) and MIRAGEN THERAPEUTICS, INC., a Delaware corporation (herein called “Tenant”).

The parties hereto agree to modify said Lease, effective October 26, 2015, as follows:

1. Paragraph 4 is modified to read as follows:

RENT. Tenant agrees to pay to Landlord as Base Rent, without prior notice or demand, the following amounts:

Schedule of Base Rent

Tenant shall begin to pay the Base Rent on the date the Primary Lease Term commences and

thereafter on the first day of each month during the term hereof. Except as provided herein, all Rents shall be paid in advance, without notice, set off, abatement, counterclaim, deduction or diminution, at The Colorado Group, Inc., 3434 47^th Street, Suite 220, Boulder, Colorado 80301, Attn: Susan Chrisman, or at such place as Landlord, from time-to-time, designates in writing. In addition, Tenant shall pay to Landlord Tenant’s Pro Rata Share of Operating Expenses as provided herein and such other charges as are required by the terms of this Lease to be paid by Tenant which shall be referred to herein as “Additional Rent.” Landlord shall have the same rights as to the Additional Rent as it has in the payment of Base Rent. At no time shall Tenant’s Rent obligation be less than the Base Rent amount set forth above.

2. Tenant hereby acknowledges occupancy of the second floor on October 26, 2015 and therefore the obligation to commence paying 100% of Property Operating Expenses as of that date.

3. Other than as modified herein, all terms and conditions of the Lease shall remain unchanged.

IN WITNESS WHEREOF, the undersigned have executed this document as of the date above written.