 Shares of Genprex Inc. GNPX, 121.37 skyrocketed 121 on massive volume in afternoon trading Monday, after the gene therapy company said its Reqorsa Immunogene Therapy was granted Fast Track Designation FTD by the U.S. Food and Drug Administration for use in combination with Merck Co. Inc.s MRK, -0.29 cancer treatment Keytruda. Trading volume exploded to 163.9 million shares, compared with the full-day average of about 476,600 shares, and enough to make the stock the most actively traded on major U.S. exchanges. 