Exhibit 10.3

[Avalanche Biotechnologies, Inc. letterhead]

August 11, 2015

Hans P. Hull, Esq.

1035 O’Brien Drive

Suite A

Menlo Park, California 94025

Re: Special Interim CEO Compensation

Dear Hans:

Pursuant to your Special Bonus letter, dated July 23, 2015, you were notified of
the Special Bonus of $120,000 payable to you within ten (10) business days of
the date of commencement of employment of a permanent Chief Executive Officer of
Avalanche Biotechnologies, Inc. (the “Company”), subject to your continued
employment through such date. The Board of Directors of the Company has modified
the payment schedule for your Special Bonus. Subject to your continued
employment on the payment dates, you will be paid $10,000 per month, beginning
August 15, 2015, up to a maximum of $120,000. In the event a permanent Chief
Executive Officer commences employment prior to full payment of the Special
Bonus, you will be paid any unpaid portion of the Special Bonus in a lump sum
within ten (10) business days of the date of commencement of employment of the
permanent Chief Executive Officer.

In addition to the Special Bonus, effective August 15, 2015, the Board of
Directors of the Company has determined to increase your annual base salary to
$360,000 per year.

We greatly appreciate your services to the Company during this transition time.

 

Sincerely,

/s/ Mark S. Blumenkranz

 

Mark S. Blumenkranz, M.D.

Chairman of the Board