Shares of Ziopharm Oncology Inc. /zigman2/quotes/200291745/composite ZIOP -0.38% tumbled 12% in morning trade Friday, after the biotechnology company's stock offering priced at a deep discount. The company said its follow-on offering of 9.7 million shares priced at $5.15, which is 28% below Thursday's closing price of $7.12. The stock hasn't closed as low as $5.15 since Oct. 14, 2016. The company has 132.4 million shares outstanding, according to FactSet. Ziopharm said that including the proceeds from the offering, expected to be $50 million, the company should have enough cash to fund operations into the fourth quarter of 2018. The stock has soared 33% year to date through Thursday, while the iShares Nasdaq Biotechnology ETF /zigman2/quotes/206189322/composite IBB -0.74% has climbed 9.9% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.39% has gained 6.9%.