Shares of Greenwich LifeSciences Inc. GLSI, +998.35% blasted 2,399.3% higher in very active and volatile afternoon trading Wednesday, after the Texas-based biopharmaceutical company displayed upbeat results of a Phase IIb trial for its breast cancer treatment. The stock, which has been halted no less than 20 times for volatility, was easily the biggest gainer trading on major U.S. exchanges, while trading volume of 15.9 million shares was many multiples of the full-day average of about 22,000 shares. The company said before the open that a poster presentation of five-year data for the GP2 clinical trial met all of its endpoints and showed zero recurrence of breast cancer in patients who had previously undergone surgery. The stock, which went public on Sept. 25, was now trading 2,159.7% above its $5.75 initial public offering price. The stock was soaring on a day that the iShares Nasdaq Biotechnology ETF IBB, -1.88% dropped 1.9% and the S&P 500 SPX, -0.79% fell 0.7%.