The Children's Hospital of Philadelphia Foundation on Friday criticized corporate governance practices at Spark Therapeutics Inc., a Children's Hospital gene therapy spin-off that has made waves with an $850,000 treatment to cure a rare form of blindness.

The Securities and Exchange Commission filing said the CHOP Foundation, which now controls 10.7 percent of Spark and is Spark's third-largest shareholder, had a representative on Spark's board until June. The foundation, with $1.4 billion in net assets, said it has been talking to Spark about returning to the board or at least having input on a director.

The foundation cited two deficiencies in the governance of Philadelphia-based Spark: it is impossible to replace the entire board at once and the company requires a 75 percent vote of stockholders for certain changes to its charter or bylaws. Neither party responded to a request for comment.