(d) Appointment of Robert Perez to Board of Directors

On January 3, 2018, the Company, following the recommendation of the Nominating and Corporate Governance Committee of the Board, elected Robert Perez, to the Company’s Board of Directors. The election was effective as of January 3, 2018. Mr. Perez was designated as a Class I member of the Board to serve until the 2019 annual meeting of the stockholders of the Company and thereafter until his successor has been duly elected and qualified, or until his earlier death, resignation or removal.

In connection with his election, on January 3, 2018, the Company granted Mr. Perez a stock option to purchase 8,000 shares of common stock with an exercise price of $55.76, the closing price of the Company's common stock on the Nasdaq Global Select Market on January 3, 2018 as well as 3,000 restricted stock units to acquire 3,000 shares of common stock upon the satisfaction of certain vesting conditions and the lapse of certain forfeiture conditions.

Mr. Perez is not a party to any transaction with the Company that would require disclosure under Item 404(a) of Regulation S-K, and there are no arrangements or understandings between Mr. Perez and any other persons to which she was selected as a director.

In connection with his election, Mr. Perez will enter into the Company’s standard form of Indemnification Agreement, a copy of which was filed as Exhibit 10.26 to Amendment No. 1 to the Company’s Registration Statement on Form S-1 (File No. 333-201318) filed with the SEC on January 20, 2015. to the terms of this agreement, the Company may be required, among other things, to indemnify Mr. Perez for some expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by her in any action or proceeding arising out of her service as a director of the Company.

About Spark Therapeutics, Inc. (NASDAQ:ONCE)

Spark Therapeutics, Inc. (Spark) is engaged in developing products in the field of gene therapy. The Company focuses on treating orphan diseases. It has a pipeline of product candidates targeting multiple rare blinding conditions, hematologic disorders and neurodegenerative diseases. Its SPK-RPE65 (voretigene neparvovec) targets genetic blinding conditions known as inherited retinal dystrophies (IRDs). Its product candidates include SPK-CHM and SPK-FIX. Its product development portfolio includes product candidates targeting expression of genes in the liver, with an initial focus on hematologic disorders. It is engaged in the development and commercialization of SPK-FIX product candidates for the treatment of hemophilia B. The Company is developing a lead product candidate for the treatment of a form of Batten disease in SPK-TPP1 program. The Company is also conducting preclinical studies on a product candidate for the treatment of Huntington’s disease, a hereditary genetic disorder.