 Shares of Nkarta Inc. tripled out of the gate Friday, after the biotechnology companys initial public offering priced above its expected range. The first trade of the stock was at 54.75, or 204.2 above the IPO price of 18, at 11:17 a.m. Eastern for about 159,000 shares. The company raised about 252 million in the IPO, which priced above the expected range of 16 to 17. The stock has pulled back since the open, and was last up 168 at 48.25. The company went public on a day that the Renaissance IPO ETF fell 1.0, while the SP; 500 edged up 0.3. 