X0306 4 2015-10-13 0 0001609351 Spark Therapeutics, Inc. ONCE 0001631248 High Katherine A C/O SPARK THERAPEUTICS, INC. 3737 MARKET STREET, SUITE 1300 PHILADELPHIA PA 19104 1 1 0 0 See Remarks Common Stock 2015-10-13 4 S 0 10000 48.00 D 330000 D Common Stock 2015-10-14 4 S 0 20000 49.00 D 310000 D Common Stock 2015-10-14 4 S 0 10000 50.03 D 300000 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $50.00 to $50.17, 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 sold at each separate price within the ranges set forth in footnote (1) to this Form 4. President and Chief Scientific Officer /s/ Joseph W. La Barge, attorney-in-fact for Katherine A. High 2015-10-14