Bothell, WA-based OncoGenex Pharmaceuticals (NASDAQ: [[ticker:OGXI]]) saw its stock tumble $3.25, or more than 26 percent, to $8.90 in mid-day trading today after issuing its quarterly financial update. The company reported yesterday that a pivotal clinical trial of its lead prostate cancer drug candidate, custirsen, has been dogged by slow patient enrollment. OncoGenex said it is awaiting word from the FDA on an amendment to the study protocol, which it hopes will speed up enrollment, by allowing patients to get either docetaxel or a new drug from Sanofi called cabazitaxel (Jevtana) in their second round of therapy. The enrollment delay means OncoGenex now expects study results in the fourth quarter of 2013, instead of by the second quarter of 2013.