Exhibit 10.3

AMENDMENT TO EMPLOYMENT LETTER AGREEMENT

THIS AMENDMENT (the “Amendment”) to the Employment Letter Agreement between
CELLADON CORPORATION, a Delaware Corporation (the “Company”) and ANDREW JACKSON,
an individual (the “Employee”) dated February 28, 2014, as amended on May 27th
(the “Agreement”), is made effective as of the 29th day of May, 2015.

WHEREAS, Company and Employee desire to amend the Agreement as set forth below;

NOW THEREFORE, in consideration of the foregoing premises and the covenants and
promises contained in the Agreement as amended hereby, the Parties, intending to
be bound, hereby agree that the following sections of the Agreement shall be
amended as follows:

 

1. The first paragraph of Section 1 is hereby deleted and replaced with the
following:

“You will be employed as the Company’s Chief Financial Officer, and you will
report to the Chief Executive Officer of the Company. You shall perform the
duties of such position as are customary, as specified in the Bylaws of the
Company, and as may be required by the Chief Executive Officer of the Company or
the Board of Directors of the Company (or any authorized committee thereof) (the
“Board”).

 

2. The first sentence of Section 2 is hereby deleted and replaced with the
following:

“Your base salary will be paid at the rate of $18,333.33 per month (an annual
rate of $220,000.00), less payroll and withholdings.”

 

3. The first two sentences of Section 3 are hereby deleted and replaced with the
following:

“As Chief Financial Officer, you will be eligible to earn an annual performance
bonus pursuant to the Company’s annual incentive bonus plan, with the target
amount of such bonus equal to 25% of your annual base salary.”

All other terms and conditions of the Agreement shall remain unchanged and in
full force and effect. All initially capitalized terms not defined herein shall
have the same meaning given to such terms in the Agreement.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly
executed by their authorized representatives effective as of the date set forth
above.

 

ACCEPTED AND AGREED TO FOR:

     

CELLADON CORPORATION

   

ANDREW C. JACKSON

“Company”

   

“Employee”

By:

 

/s/ Paul Cleveland

   

By: /s/ Andrew C. Jackson

Name:

 

Paul Cleveland

   

Name:  Andrew C. Jackson

Title:

 

President & CEO