X0306 4 2015-10-07 0 0001609351 Spark Therapeutics, Inc. ONCE 0001458116 Altschuler Steven C/O SPARK THERAPEUTICS, INC. 3737 MARKET STREET, SUITE 1300 PHILADELPHIA PA 19104 1 0 0 0 Common Stock 2015-10-07 4 P 0 5000 49.106 A 5000 D The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $48.99 to $49.16, inclusive. The reporting person undertakes to provide to Spark Therapeutics, Inc., any security holder of Spark Therapeutics, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnote (1) to this Form 4. /s/ Joseph W. La Barge, attorney-in-fact for Steven Altschuler 2015-10-09