Shares of Spark Therapeutics, the Philadelphia gene therapy developer backed by Childrens Hospital of Philadelphia, zoomed as high as $45 a share after trading opened at $23 in its initial public stock offering (IPO) led by JPMorgan and Credit Suisse.

The company said it grossed $161 milllion, before payments to brokers, by selling 7 million shares (ticker symbol: ONCE) to investors on the Nasdaq stock market at $23/share. But a surge of investor interest in the company boosted Spark's total value (including shares still held by earlier investors before it went public) to nearly $1 billion, and increased the value of 4.9 million shares owned by CHOP, according to previous federal securities filings, to as much as $220 million.

Chief executive Jeff Marrazzo is another major beneficiary: he owns 380,000 shares, now worth around $16 million, according to federal securities records. Spark's statement on the IPO here.  More on Spark's structure, investors, founders and early products in my Philadelphia Inquirer colleague David Sell's Jan. 2 story here.  Spark investor prospectus with more detail on what they're going to do with the money here.